Co-reporter:Wangcheng Zhan, Shize Yang, Pengfei Zhang, Yanglong Guo, Guanzhong Lu, Matthew F. Chisholm, and Sheng Dai
Chemistry of Materials September 12, 2017 Volume 29(Issue 17) pp:7323-7323
Publication Date(Web):July 27, 2017
DOI:10.1021/acs.chemmater.7b02206
Ceria-based materials possessing mesoporous structures afford higher activity than the corresponding bulk materials in CO oxidation and other catalytic applications, because of the wide pore channel and high surface area. The development of a direct, template-free, and scalable technology for directing porosity inside ceria-based materials is highly welcome. Herein, a family of mesoporous transition-metal-doped ceria catalysts with specific surface areas up to 122 m2 g–1 is constructed by mechanochemical grinding. No templates, additives, or solvents are needed in this process, while the mechanochemistry-mediated restructuring and the decomposing of the organic group led to plentiful mesopores. Interestingly, the copper species are evenly dispersed in the ceria matrix at the atomic scale, as observed in high resolution scanning transmission electron microscopy in high angle annular dark field. The copper-doped ceria materials show good activity in the CO oxidation.
Co-reporter:Hai-Feng Wang;Xue-Qing Gong;Yang-Long Guo;Yun Guo;Guan Zhong Lu;P. Hu
The Journal of Physical Chemistry C June 11, 2009 Volume 113(Issue 23) pp:10229-10232
Publication Date(Web):Publication Date (Web): May 18, 2009
DOI:10.1021/jp900942a
Using density functional theory with the inclusion of on-site Coulomb correction, the O vacancy formation energies of CexZr1−xO2 solid solutions with a series of Ce/Zr ratios are calculated, and a model to understand the results is proposed. It consists of electrostatic and structural relaxation terms, and the latter is found to play a vital role in affecting the O vacancy formation energies. Using this model, several long-standing questions in the field, such as why ceria with 50% ZrO2 usually exhibit the best oxygen storage capacity, can be explained. Some implications of the new interpretation are also discussed.
Co-reporter:Wangcheng Zhan;Yanqin Wang;Yanglong Guo;Zhigang Zhang;Xiaohui Liu;Guanzhong Lu;Yunsong Wang;Yun Guo
The Journal of Physical Chemistry C April 30, 2009 Volume 113(Issue 17) pp:7181-7185
Publication Date(Web):Publication Date (Web): April 3, 2009
DOI:10.1021/jp8101095
The epoxidation of styrene with hydrogen peroxide with higher selectivity to styrene oxide was carried out over lanthanum-doped MCM-48 (La-MCM-48) molecular sieves, in which aqueous NaOH solution was used to adjust the pH value of the reaction solution. The results show that the pH value of the reaction solution has a great influence on the catalytic performance of La-MCM-48 and the product distribution. When the pH value of the reaction solution was 11.5, the conversion of styrene reached 54.5% and the selectivity to styrene oxide was 98.8%. UV−vis and EPR spectroscopy was used to characterize the lanthanum species in the framework of La-MCM-48 and the peroxo-lanthanum species by H2O2 reacting with the lanthanum species. It has been found that the conversion of styrene has a close relationship with the amount of the peroxo-lanthanum species, and the selectivity to styrene oxide has a close relationship with the ratio of La(III)-superoxide species to La(III)-hydroperoxide species, which can be controlled by adjusting the pH value of the reaction solution.
Co-reporter:Huan Ni, Yun Guo, Li Wang, Yanglong Guo, Wangcheng Zhan, Guanzhong Lu
Powder Technology 2017 Volume 315(Volume 315) pp:
Publication Date(Web):15 June 2017
DOI:10.1016/j.powtec.2017.03.038
•Mesoporous and high surface area Al2O3 was prepared by solid-state reaction without surfactants.•High thermal-stable Al2O3 or doped Al2O3 was prepared by mesoporous precursor or AACH.•Nature of dopant and its amount affect obviously textural property and morphology of doping Al2O3.•25%Si-Al2O3 has high surface area (176 m2/g) after calcination at 1100 °C for 10 h.•Mesoporous precursor is AlOOH which can be converted hydrothermally lower crystal AACH.Alumina and M-(La, Ba, Si) doped alumina were prepared by a facile low temperature solid-state reaction route and using cheap inorganic raw materials without any surfactants, in which only a harmless byproduct to environment was NH4Cl. The results show that all the prepared samples have a mesoporous structure and the BET surface area of as-synthesized alumina precursor has reached 326 m2/g. Si-doped alumina exhibits remarkable thermal stability and high surface area (135–163 m2/g) and the Ba-doped alumina have a large pore volume (0.44–0.95 cm3/g) even after calcination at 1100 °C for 10 h. The nature of dopants and their concentrations have a significant influence on the textural properties and morphologies of M-alumina. The precursor synthesized can be converted to lower crystal ammonium aluminum carbonate hydroxide (AACH) by further thermal treatment. Si-doped alumina prepared by alumina from thermal decomposition of AACH possessed the superior thermal stability, and the surface area of 25%Si-Al2O3 calcined at 1100 °C for 10 h can reach 176 m2/g. This facile synthetic route of alumina is an environmental friendly and convenient, and can be used in synthesis of other metal oxide porous materials.Download high-res image (171KB)Download full-size image
Co-reporter:Yu Fu;Yanglong Guo;Yun Guo;Yunsong Wang;Li Wang;Wangcheng Zhan;Guanzhong Lu
Catalysis Science & Technology (2011-Present) 2017 vol. 7(Issue 18) pp:4136-4144
Publication Date(Web):2017/09/18
DOI:10.1039/C7CY00912G
Nanosize metal oxides generally possess high catalytic activity, but they tend to agglomerate into larger particles during a reaction. Therefore, the preparation of nanosize metal oxides with high stability is a crucial challenge. A novel and facile approach involving impregnation followed by a double solvent method was developed to directly encapsulate ultrafine Mn3O4 nanoparticles (NPs) into the nanocages of metal–organic frameworks (MOFs). A series of MIL-101 encapsulated Mn3O4 NPs were prepared, in which the contents of Mn3O4 ranged from 3.2% to 33%. Ultrafine Mn3O4 NPs with a particle size of about 3 nm have been successfully embedded in the nanocages of MIL-101 with a uniform distribution. The MIL-101 encapsulated Mn3O4 NPs with a Mn3O4 content of 15% exhibits the highest conversion of benzyl alcohol (38.7%) and a >99% selectivity to benzaldehyde. Furthermore, after being repeatedly used 10 times, its catalytic activity is hardly changed. When the content of Mn3O4 NPs was further increased, the catalytic activity of the catalyst decreases, due to aggregated Mn3O4 particles with a large size which formed outside the MIL-101 matrix.
Co-reporter:Chenhao Du;Yun Guo;Yanglong Guo;Xue-Qing Gong;Guanzhong Lu
Journal of Materials Chemistry A 2017 vol. 5(Issue 11) pp:5601-5611
Publication Date(Web):2017/03/14
DOI:10.1039/C7TA00015D
We proposed a hard-templated and electrostatic attraction induced deposition method to prepare a hollow core–shell Au@CeO2–ZrO2 nanocatalyst with a high surface area, in which a 6–8 nm ultrathin layer composed of CeO2–ZrO2 nanocrystals is embedded with individual Au nanoparticles, forming a sub-10 nm core–shell-like structure. In this hollow core–shell nanocatalyst, the mobility and growth of Au nanoparticles can be well inhibited even at 700 °C. For two model reactions of the selective reduction of 4-nitrophenol and CO oxidation, this Au@CeO2–ZrO2 nanocatalyst shows good catalytic activity and stability, compared with Au/CeO2–ZrO2 prepared by the deposition–precipitation (DP) method. For the CO oxidation, the activity of Au@CeO2–ZrO2 can be well maintained after calcination at 700 °C, while negligible CO conversion is observed over DP-Au/CeO2–ZrO2. Further research shows that the improved catalytic performance of this hollow core–shell nanocatalyst can be attributed to the nanoscale core–shell structure, which effectively inhibits the migration and growth of the Au NPs, and maximizes the interface between the Au NPs and the CeO2–ZrO2.
Co-reporter:Yali Shen, Jun Yu, Xiuzhen Xiao, Xiaoming Guo, Dongsen Mao, Houjin Huang, Guanzhong Lu
Journal of Catalysis 2017 Volume 352(Volume 352) pp:
Publication Date(Web):1 August 2017
DOI:10.1016/j.jcat.2017.06.022
•Polymer nanofilm-coated FeaCobOx catalysts were prepared by a solid-phase method.•The polymer nanofilm substantially minimized water-poisoning effect.•T50 of CO oxidation over the catalyst was 47 °C in the presence of ∼0.6 vol.% H2O.•The catalyst was not deactivated after 750 h operation at 3.1 vol.% H2O and 90 °C.Water-induced deactivation of the oxides catalysts (especially for the Co3O4-based catalysts) is a challenging problem. For this reason, highly effective, long-term stable, moisture-resistant polymer nanofilm-coated FeaCobOx catalysts were synthesized by a solid-phase method mediated with oxalic acid (OA)/ethlyene glycol (EG) for low-temperature CO oxidation. The effects of the Fe, OA and EG amounts and calcination temperature on the physicochemical and catalytic properties of the FeaCobOx catalysts were investigated by various characterization techniques. The results demonstrate that the FeaCobOx catalysts are structurally mesoporous, and nanostructured FeaCobOx and polymer nanofilm coating play major roles on their high catalytic activity and stability. The nanofilm-coated Fe3Co16Ox nanoparticles prepared under an optimized synthetic condition and calcined at 250 °C possesses higher surface area (134 m2/g), Co3+/Co2+ ratio (1.89) and oxygen vacancy (20.5%), and thus exhibits the excellent catalytic performance for CO oxidation, such as, T50 of −114 °C under normal moisture (3–10 ppm) and T50 of 47 °C under moisture-rich (∼0.6 vol.%) conditions. Remarkably, compared with the published results, its much-improved long-term catalytic stability (>1 month) can be observed even at a very high moisture level (3.1 vol.%) and relatively low temperature (90 °C). The deactivation of the catalyst at lower temperature resulted from accumulated water and carbonates on the catalyst surface can also be substantially minimized, through the water vapor-resistant with the help of gas-permeable polymer nanofilm coating.Download high-res image (78KB)Download full-size image
Co-reporter:Qing Zhang, Yanglong Guo, Wangcheng Zhan, Yun Guo, ... Guanzhong Lu
Chinese Journal of Catalysis 2017 Volume 38, Issue 1(Volume 38, Issue 1) pp:
Publication Date(Web):1 January 2017
DOI:10.1016/S1872-2067(16)62539-1
Ag-Cu-Cl/BaCO3 catalysts with different Cl and Cu loadings, prepared by the reduction deposition impregnation method, were investigated for gas-phase epoxidation of propylene by molecular oxygen and characterized by X-ray diffraction, X-ray photoelectron spectroscopy and O2 temperature programmed desorption. Ag-Cu-Cl/BaCO3 catalyst with 0.036 wt% Cu and 0.060 wt% Cl exhibited the highest catalytic performance for gas-phase epoxidation of propylene by molecular oxygen. A propylene oxide selectivity of 83.7% and propylene conversion of 1.2% were achieved under the reaction conditions of 20% C3H6-10% O2-70% N2, 200 °C, 0.1 MPa and 3000 h−1. Increasing the Cl loading allowed Ag to ensemble easier, whereas changing the Cu loading showed little effect on Ag crystallite size. The appropriate Cl loading of Ag-Cu-Cl/BaCO3 catalyst can reduce the dissociation adsorption of oxygen to atomic oxygen species leading to the combustion of propylene to CO2, which benefits epoxidation of propylene by molecular oxygen. Excessive Cl loading of Ag-Cu-Cl/BaCO3 catalyst decreases propylene conversion and propylene oxide selectivity remarkably because of Cl poisoning. The appropriate Cu loading of Ag-Cu-Cl/BaCO3 catalyst is efficient for the epoxidation of propylene by molecular oxygen, and an excess Cu loading decreases propylene oxide selectivity because the aggregation of Cu species increases the exposed surfaces of Ag nanoparticles, which was shown by slight increases in atomic oxygen species adsorbed. The appropriate loadings of Cu and Cl of Ag-Cu-Cl/BaCO3 catalyst are important to strike the balance between molecular oxygen and atomic oxygen species to create a favorable epoxidation of propylene by molecular oxygen.The appropriate loadings of Cu and Cl of Ag-Cu-Cl/BaCO3 catalyst are important to the balance between molecular and atomic oxygen species, which benefits the epoxidation of propylene by molecular oxygen.Download high-res image (67KB)Download full-size image
Co-reporter:Bing Zhan;Shuangshuang Zhang;Jun Yu;Xiuzheng Xiao;Xiaoming Guo
Catalysis Letters 2017 Volume 147( Issue 8) pp:2160-2166
Publication Date(Web):19 June 2017
DOI:10.1007/s10562-017-2116-3
Selective hydrogenation of amino acid methyl esters to chiral amino alcohols is an important and fascinating process. The CuZn0.3Mg0.1AlOx catalyst for the synthesis of chiral amino alcohols was prepared by the fractional co-precipitation method in the 50–100 g scale. The effect of the reduction gas on the catalytic activity, and the effects of the reaction conditions (R-p-m/Cat, temperature, reaction time, H2 pressure and solvent) on the catalytic hydrogenation of R-phenylglycine methyl ester (marked as R-p-m) were investigated. When R-p-m in the ethanol solvent was hydrogenated at 5 MPa of H2 and 80 °C for 10 h over this catalyst reduced by H2, 87.7% yield of R-phenylglycinol with ~ 100% ee value was obtained, and its reaction activation energy (Ea) was 36.7 kJ/mol. After repeated usage 16 times, its catalytic activity was hardly varied. Using this catalyst to catalyze the preparation of other amino alcohols, the high yield of product with ~100% ee value was obtained also.
Co-reporter:Lingzhan Kong;Xiuzhen Xiao;Jun Yu;Dongsen Mao
Journal of Materials Science 2017 Volume 52( Issue 11) pp:6310-6321
Publication Date(Web):2017 June
DOI:10.1007/s10853-017-0863-6
The Sm3+, Dy3+ doped and Sm3+/Dy3+ co-doped NaLa(MoO4)2 spherical phosphors were hydrothermally synthesized by the EDTA-2Na mediated method. Under the excitation of 297 nm, the quenching concentration of Sm3+ in NaLa(MoO4)2 host was determined to be 13%, and the concentration quenching mechanism was discussed to be the electric quadrupole–quadrupole interaction. After Sm3+ and Dy3+ ions were co-doped into the NaLa(MoO4)2 host, the energy transfer behaviors resulted from Dy3+ to Sm3+ ions were investigated by the help of the luminescent spectra of the obtained phosphors. By varying co-doping concentrations of Sm3+/Dy3+ ions, the emission color of NaLa(MoO4)2:Sm3+/Dy3+ can be tuned from reddish-orange, pink and white to bluish-green. The CIE chromaticity coordinate, the correlated color temperature and the quantum efficiency of NaLa0.87(MoO4)2:1%Sm3+, 12%Dy3+ were calculated to be (0.356, 0.320), 4353 K and 20%, respectively. Furthermore, in the temperature-dependent analysis, it presented good thermal stability, which can become a promising single-phased white-emitting phosphor for white LEDs devices. Based on these results, the possible energy transfer mechanism between Dy3+ and Sm3+ in NaLa(MoO4)2:Sm3+/Dy3+ was also proposed.
Co-reporter:Yu Fu, Wangcheng Zhan, Yanglong Guo, Yun Guo, ... Guanzhong Lu
Green Energy & Environment 2017 Volume 2, Issue 2(Volume 2, Issue 2) pp:
Publication Date(Web):1 April 2017
DOI:10.1016/j.gee.2017.01.006
Selective oxidation of saturated hydrocarbons with molecular oxygen has been of great interest in catalysis, and the development of highly efficient catalysts for this process is a crucial challenge. A new kind of heterogeneous catalyst, cobalt-doped carbon nitride polymer (g-C3N4), was harnessed for the selective oxidation of cyclohexane. X-ray diffraction, Fourier transform infrared spectra and high resolution transmission electron microscope revealed that Co species were highly dispersed in g-C3N4 matrix and the characteristic structure of polymeric g-C3N4 can be retained after Co-doping, although Co-doping caused the incomplete polymerization to some extent. Ultraviolet–visible, Raman and X-ray photoelectron spectroscopy further proved the successful Co doping in g-C3N4 matrix as the form of Co(II)N bonds. For the selective oxidation of cyclohexane, Co-doping can markedly promote the catalytic performance of g-C3N4 catalyst due to the synergistic effect of Co species and g-C3N4 hybrid. Furthermore, the content of Co largely affected the activity of Co-doped g-C3N4 catalysts, among which the catalyst with 9.0 wt% Co content exhibited the highest yield (9.0%) of cyclohexanone and cyclohexanol, as well as a high stability. Meanwhile, the reaction mechanism over Co-doped g-C3N4 catalysts was elaborated.A new kind of heterogeneous catalyst, cobalt-doped carbon nitride polymer (g-C3N4), was demonstrated to be highly efficient and recyclable for selective oxidation of cyclohexane with molecular oxygen.Download high-res image (177KB)Download full-size image
Co-reporter:Hai-Feng Wang, Dong Wang, Xiaohui Liu, Yang-Long Guo, Guan-Zhong Lu, and Peijun Hu
ACS Catalysis 2016 Volume 6(Issue 8) pp:5393
Publication Date(Web):July 8, 2016
DOI:10.1021/acscatal.6b00764
Achieving low-temperature C═C bond activation has been of interest in heterogeneous catalysis, and understanding the subject (i.e., establishing the mechanism and identifying the origin) is desirable. Herein, taking the CH2CH2 combustion on spinel Co3O4(110) as an example, we report a systematic investigation on the C–C bond breaking processes using first-principles calculations. An unexpected pathway for C–C cracking, called the valency-saturation-driven mechanism, is determined, and the high activity of Co3O4 in catalyzing CH2CH2 combustion at low temperature is rationalized. More importantly, some basic C–C bond activation rules on metal oxides with isolated single-atom sites, which differ from the traditional metal catalysis with multiatom active sites, are revealed. The understandings derived from this work may underpin the structure–activity relationship in oxide catalysis.Keywords: Co3O4; C−C bond activation; DFT; heterogeneous catalysis; valency-saturation-driven mechanism
Co-reporter:Zong Hu, Xiaofei Liu, Dongmei Meng, Yun Guo, Yanglong Guo, and Guanzhong Lu
ACS Catalysis 2016 Volume 6(Issue 4) pp:2265
Publication Date(Web):February 23, 2016
DOI:10.1021/acscatal.5b02617
Ceria nanocrystallites with different morphologies and crystal planes were hydrothermally prepared, and the effects of ceria supports on the physicochemical and catalytic properties of Pd/CeO2 for the CO and propane oxidation were examined. The results showed that the structure and chemical state of Pd on ceria were affected by ceria crystal planes. The Pd species on CeO2-R (rods) and CeO2-C (cubes) mainly formed PdxCe1–xO2−σ solid solution with −Pd2+–O2––Ce4+– linkage. In addition, the PdOx nanoparticles were dominated on the surface of Pd/CeO2-O (octahedrons). For the CO oxidation, the Pd/CeO2-R catalyst showed the highest catalytic activity among three catalysts, its reaction rate reached 2.07 × 10–4 mol gPd–1 s–1 at 50 °C, in which CeO2-R mainly exposed the (110) and (100) facets with low oxygen vacancy formation energy, strong reducibility, and high surface oxygen mobility. TOF of Pd/CeO2-R (3.78 × 10–2 s–1) was much higher than that of Pd/CeO2-C (6.40 × 10–3 s–1) and Pd/CeO2-O (1.24 × 10–3 s–1) at 50 °C, and its activation energy (Ea) was 40.4 kJ/mol. For propane oxidation, the highest reaction rate (8.08 × 10–5 mol gPd–1 s–1 at 300 °C) was obtained over the Pd/CeO2-O catalyst, in which CeO2-O mainly exposed the (111) facet. There are strong surface Ce–O bonds on the ceria (111) facet, which favors the existence of PdO particles and propane activation. The turnover frequency (TOF) of the Pd/CeO2-O catalyst was highest (3.52 × 10–2 s–1) at 300 °C and its Ea value was 49.1 kJ/mol. These results demonstrate the inverse facet sensitivity of ceria for the CO and propane oxidation over Pd/ceria.Keywords: ceria crystal plane; CO oxidation; effect of ceria support; propane oxidation; supported Pd catalyst
Co-reporter:Qiguang Dai, Shuxing Bai, Yang Lou, Xingyi Wang, Yun Guo and Guanzhong Lu
Nanoscale 2016 vol. 8(Issue 18) pp:9621-9628
Publication Date(Web):07 Apr 2016
DOI:10.1039/C6NR01800A
PdO/CeO2 nanosheets encapsulated by a monolayer of a continuous and dense HZSM-5 zeolite membrane were prepared by a facile in situ hydrothermal growth process and used as a highly efficient and thermally stable catalyst for methane combustion. Uncoated PdO/CeO2 suffered severe sintering at high temperature or high oxygen concentration. However, the encapsulation of HZSM-5 significantly improved sintering resistance by the suppressing effects of the HZSM-5 coating for the agglomeration of PdOx nanoparticles, resulting in the outstanding thermal stability of PdO/CeO2. Furthermore, the synthesized hybrid materials also exhibited good oxygen- and water-tolerance for methane combustion due to the oxygen or water barrier. In addition, a reactivation behavior was observed due to the self-redispersion of PdOx on CeO2 nanosheets in the reaction atmosphere at high temperature.
Co-reporter:Jie Li, Xiaofei Liu, Wangcheng Zhan, Yun Guo, Yanglong Guo and Guanzhong Lu
Catalysis Science & Technology 2016 vol. 6(Issue 3) pp:897-907
Publication Date(Web):09 Nov 2015
DOI:10.1039/C5CY01571E
Ceria–zirconia solid solution is a very important material in three-way catalysts for automotive emission control. High oxygen storage capacity (OSC) and thermally stable Ce0.5Zr0.5O2 was prepared by a modified complexing–coprecipitation (CC) method, and its surface area reached 44 m2 g−1 after calcination at 1100 °C for 6 h. Based on the characterizations of its structural and physicochemical properties, it was found that Ce0.5Zr0.5O2 prepared by the CC method existed as the t′′-phase with rich oxygen defects and surface Ce3+ and has a larger BET surface area, uniform particle and pore sizes, and excellent bulk oxygen migration and redox abilities than samples prepared by other methods. After being calcined at 1100 °C for 6 h, its surface area, OSC (and OSCC, oxygen storage capacity complete) and catalytic activity for the oxidation of CO were still the best among three Ce0.5Zr0.5O2 solid solutions prepared by three methods whether it was used as the catalyst or as a support for a Pd catalyst, reflecting its good thermostability, although its particle and pore sizes were somewhat increased. This complexing–coprecipitation method can be used to prepare other high surface area and thermally stable inorganic materials.
Co-reporter:Zheng Wang, Guanzhong Lu, Yun Guo, Yanglong Guo, and Xue-Qing Gong
ACS Sustainable Chemistry & Engineering 2016 Volume 4(Issue 3) pp:1591
Publication Date(Web):January 7, 2016
DOI:10.1021/acssuschemeng.5b01533
The liquid phase synthesis of pseudoionones (PS) by the cross-aldol condensation of citral and acetone was investigated over MgAl mixed oxides containing rare earth elements (REE = Y, La, Eu), which were obtained from corresponding REE-modified hydrotalcite materials after calcination. The results showed that the unmodified and La(Eu)-modified MgAl mixed oxide catalysts showed relatively low activity, and Y-modified MgAl mixed oxides presented an unexpected high catalytic activity. PS selectivity of ∼85% and citral conversion of 100% were achieved at 60 °C for 3 h. On the basis of the characterizations of the structural, textural, and basic properties, it was found that Mg3Al1-aYaOx catalysts exhibited relatively well-developed small flake morphology with high surface area and pore volume, resulting in exposure of more basic sites on the catalyst surface. The formation of PS over Mg3Al1-aYaOx may be accompanied by gradual modification of the catalyst surface to form re-Mg3Al1-aYaOx through a rehydration process with produced water, which reconverts the O2– basic sites to OH– basic groups. Unlike La and Eu elements, the presence of Y could promote this “one-pot” or in situ rehydration process of MgAl mixed oxides during the aldol reaction. This Y-modified MgAl mixed oxides after a one-pot rehydration process with active Brønsted basic sites is responsible for the high activity in the cross-aldol condensation of citral and acetone.Keywords: Aldol condensation; MgAl hydrotalcite; One-pot rehydration; Pseudoionone synthesis; Yttrium modification;
Co-reporter:Zhangping Shi, Shuangshuang Zhang, Xiuzhen Xiao, Dongsen Mao and Guanzhong Lu
Catalysis Science & Technology 2016 vol. 6(Issue 10) pp:3457-3467
Publication Date(Web):03 Dec 2015
DOI:10.1039/C5CY01238D
Highly effective CuZn0.3MgxAlOy (x = 0–0.2) catalysts for the synthesis of chiral L-phenylalaninol derived from Cu-rich hydrotalcite-like precursors were prepared by a co-precipitation method with Na2CO3 as the precipitant, and their physicochemical and catalytic properties were characterized. The results show that the presence of Mg2+ ions can promote the formation of hydrotalcite-like (htl) precursors, and the Mg2+ content would affect the phase purity of the prepared htl precursors. The BET surface area, exposed copper surface area and amount of acid sites of the samples decreased with the increase in the molar ratio of Mg2+/Al3+. Also, the dense layered htl precursors are beneficial to the atomically uniform distribution of the corresponding metal oxides in the prepared catalysts, promoting the stronger interaction between Cu0 and Al2O3 after the catalysts were reduced (SMSI effect). The activity of the CuZn0.3MgxAlOy catalysts is greatly dependent on not only the metallic copper surface area, but also the SMSI effect and the acidity of the catalysts. When Mg2+/Al3+ = 0.1 (mol), a phase-pure htl precursor could be obtained, and after calcination, the prepared CZA-0.1 catalyst exhibited very excellent catalytic performance for the hydrogenation of L-phenylalanine methyl ester to chiral L-phenylalaninol. After 5 h of reaction at 110 °C and 4 MPa H2, 100% conversion of L-phenylalanine methyl ester and 91.1% yield of L-phenylalaninol with an ee value of ~100% were achieved. After recycling 13 times, the L-phenylalaninol selectivity of the CZA-0.1 catalyst only decreased by 7.2%.
Co-reporter:Jun Yu, Dongsen Mao, Dan Ding and Guanzhong Lu
RSC Advances 2016 vol. 6(Issue 80) pp:76736-76742
Publication Date(Web):09 Aug 2016
DOI:10.1039/C6RA16404H
The effects of surface properties of the monodispersed SiO2 prepared using different ammonia concentrations on the catalytic performance of Rh–Mn–Li/SiO2 for CO hydrogenation to C2 oxygenates were investigated. The investigation based on the catalytic performance and characterizations of the catalysts suggested that the catalytic performance was relatively stable on the Rh–Mn–Li catalyst supported on the SiO2 prepared using high ammonia concentration, which is attributed to the steady state of the metals supported on it. However, the rough surface of SiO2 prepared using a low ammonia concentration resulted in easy agglomeration of the metals. Correspondingly, the size of Rh particles increased and the isolated Rh+ sites decreased in the reaction process, leading to the decrease of C2 oxygenate selectivity of the catalyst as a function of time.
Co-reporter:Fanyun Zhou, Xuexun Du, Jun Yu, Dongsen Mao and Guanzhong Lu
RSC Advances 2016 vol. 6(Issue 71) pp:66553-66563
Publication Date(Web):30 Jun 2016
DOI:10.1039/C6RA15205H
Carbon nanotube (CNT) supported PdCl2–CuCl2 catalysts were prepared by the two-step impregnation method, and the effects of the Pd and Cu loadings on their physicochemical properties and catalytic performance for low-temperature CO oxidation in the presence of high concentration moisture were investigated. With the increase in the Pd and Cu loadings, the surface active Pd2+ and Cu2+ species increased, improving the adsorption of CO and oxygen, and the oxidation of Pd0 to Pd2+ (or Pd+). Compared with Cu species, increasing the Pd loading can effectively add catalytically active sites for CO oxidation. For the CO oxidation, the presence of moderate water is necessary for sustaining the high activity of this catalyst, but the excessive water vapor in the feed gas would injure the activity and stability of the catalyst. When the moisture level in the reactant gas was 3.1%, the CO conversion was still retained at around 93% after 60 h of the reaction at 25 °C over the 3.3 wt% Pd–6.6 wt% Cu/CNT catalyst, indicating that this catalyst has very good stability and water-resistance.
Co-reporter:Qingping Ke;Mingzhou Wu;Chao Wang ;Dr. Guanzhong Lu
ChemCatChem 2016 Volume 8( Issue 8) pp:1557-1563
Publication Date(Web):
DOI:10.1002/cctc.201501426
Abstract
Heterogeneous catalytic reactions of aromatic organic molecules over zeolite catalysts present many challenges because of the shape selectivity of the micropores of conventional zeolites that limits the diffusion of aromatic molecules. Herein, Ullmann coupling reactions of phenols with nitro-substituted aryl halides were catalyzed by rare-earth-doped mesoporous AlPO-5 zeolites in the absence of ligands. The AlPO-5-MAlPO-5-M zeolites had a pure AFI structure and consisted of spherical particles assembled by nanofibers. The rare-earth elements were highly dispersed in the AlPO-5-MAlPO-5-M samples. The LaAlPO-5-MAlPO-5-M zeolite is an excellent catalyst for Ullmann coupling reactions of phenols and nitro-substituted aryl halides. Mesoporous LaAlPO-5 has an excellent stability and recyclability in the Ullmann coupling of p-X-nitrobenzene (X=Cl, Br, and I) with 2-naphthol. These results are important in the exploration of attractive Ullmann coupling reactions and in the development of mesoporous zeolite catalysts for other organic reactions.
Co-reporter:Jun Yu, Dongsen Mao, Dan Ding, Xiaoming Guo, Guanzhong Lu
Journal of Molecular Catalysis A: Chemical 2016 Volume 423() pp:151-159
Publication Date(Web):November 2016
DOI:10.1016/j.molcata.2016.06.018
•New insights into the roles of Mn and Li in CO hydrogenation were investigated.•The state of Rh would be changed by the promotion of Mn and Li.•A proper addition of Mn can increase the CO adsorption and weaken the CO-Rh bond.•A low doping of Li can enhance the CO adsorption ability and improve the H2 dissociation.•As the synergistic promotion of Mn and Li, the catalytic performance was improved.It has been reported widely that Rh-Mn-Li/SiO2 catalysts can exhibit high selectivity to C2+ oxygenates during CO hydrogenation, with promoters of Mn and Li playing an important role in this behavior. In this study, a series catalysts of Rh-Mn-Li/SiO2 with different amounts of Mn and Li were prepared, and the new insights into the effects of Mn and Li on the mechanistic pathway for C2+ oxygenates synthesis from syngas were investigated. The XPS analysis showed that Rh existed mainly as metallic Rh after reduction, however partially positively charged Rhδ+ atoms appeared on the surface of Mn-containing catalyst due to the interaction of Rh-Mn. The results of H2-TPR indicated that both of Li and Mn can inhibit the reduction of Rh2O3. With the increase in the ratio of Mn/Rh, the most effective interaction, associated to the presence of two reduction centers of Rh2O3, was obtained when the ratio of Mn/Rh = 1. In situ-FTIR was used to probe the effects of Mn and Li on CO absorption and hydrogenation. With regards to the CO adsorption, the doping of Mn can enhance the CO adsorption ability of Rh and weaken the CO-Rh bond strength very effectively when the amount of Mn reached 1.5 wt.%. Improved capacity of CO adsorption is conducive to increase of CO conversion, while the weakening of CO-Rh bond is beneficial to the CO insertion reaction, thus contributing to the generation of C2+ oxygenates. Moreover, the low amount of Li (≤0.075 wt.%) can also enhance the CO adsorption, resulting in the improvement of reactivity. On the other hand, Mn and Li promoted dissociation of H2, which is favorable to an increase in the rate of hydrogenation. But an opposite effect appeared at high content of Mn (>1.5 wt.%). As the optimized results, when Rh, Mn, Li content was 1.5 wt.%, 1.5 wt.% and 0.075 wt.%, the catalyst for CO hydrogenation of C2+ oxygenates achieved the best performance of C2+ oxygenates synthesis.
Co-reporter:Qing Zhang, Guangtao Chai, Yanglong Guo, Wangcheng Zhan, Yun Guo, Li Wang, Yunsong Wang, Guanzhong Lu
Journal of Molecular Catalysis A: Chemical 2016 Volume 424() pp:65-76
Publication Date(Web):1 December 2016
DOI:10.1016/j.molcata.2016.08.019
•Ag-CuCl2/BaCO3 catalyst was prepared by reduction-deposition-impregnation method.•Ag-CuCl2/BaCO3 catalyst with low CuCl2 doping exhibits better catalytic performance.•Epoxidation of propylene over Ag-CuCl2/BaCO3 catalyst follows Rideal-Eley mechanism.•Molecular oxygen species benefit epoxidation of propylene to propylene oxide.•Ag-based catalyst is deactivated by coke deposition and can be entirely regenerated.Ag-MClx/BaCO3 catalysts with different chloride promoters, prepared by reduction-deposition-impregnation method, were investigated for gas-phase epoxidation of propylene to propylene oxide (PO) by molecular oxygen. Ag-CuCl2/BaCO3 catalyst with 360 ppm of Cu and 400 ppm of Cl exhibits the best initial catalytic performance, in which PO selectivity of 71.2% and propylene conversion of 1.3% are achieved, but only PO selectivity of 13.9% is obtained at propylene conversion of 3.2% after reaction for 500 min. The catalytic reaction mechanism over Ag-CuCl2/BaCO3 catalyst follows Rideal-Eley mechanism, in which propylene in the gas phase reacts with molecular oxygen species adsorbed on the surface of Ag at the interface in close contact with CuCl2 to produce PO, and with atomic oxygen species adsorbed on the surface of Ag nanoparticles to produce CO2 and H2O. One oxygen atom of molecular oxygen species reacts with propylene to form a PO molecule, and the left insufficient oxygen atoms react with propylene to produce oxygen-containing intermediates and then to form coke deposition which covers the active sites and thus results in the catalyst deactivation. The deactivated Ag-CuCl2/BaCO3 catalyst can be completely regenerated by combustion of coke deposition and then impregnation with appropriate amount of Cl.
Co-reporter:Shuangshuang Lai, Yong She, Wangcheng Zhan, Yun Guo, Yanglong Guo, Li Wang, Guanzhong Lu
Journal of Molecular Catalysis A: Chemical 2016 Volume 424() pp:232-240
Publication Date(Web):1 December 2016
DOI:10.1016/j.molcata.2016.08.026
•The atmosphere during ion exchange and calcination affected the capacity of cation exchange and the nature of Fe species in Fe-ZSM-5 catalysts.•Fe-ZSM-5 catalysts prepared under a N2 atmosphere exhibited high SCR activity.•NH3-SCR over Fe-ZSM-5 catalysts predominantly followed the Eley-Rideal reaction mechanism.Fe-ZSM-5 catalysts for selective catalytic reduction (SCR) of NOx with ammonia were prepared by ion exchange under different atmospheres and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Temperature-programmed desorption of NH3 and NO (NH3-TPD and NO-TPD), Ultraviolet–visible (UV–vis) spectroscopy and in situ diffuse reflectance Fourier transform infrared spectroscopy (DRIFT). The results show that the atmosphere during ion exchange and calcination significantly affects the cation exchange capacity and the nature of the Fe species in Fe-ZSM-5 catalysts. An air atmosphere was conducive to improving the ability of ZSM-5 zeolites for Fe ionic exchange. However, isolated Fe3+ sites were dominant in Fe-ZSM-5 catalyst (Fe-Z(N2)) prepared under a N2 atmosphere, and small oligomeric FexOy clusters and FexOy nano-particles were markedly increased in Fe-ZSM-5 catalyst prepared in air, resulting in the higher SCR activity and wide temperature window of Fe-Z(N2). Moreover, Fe-Z(N2) catalyst possessed more Brønsted acid sites and could adsorb more NH3 species, promoting its SCR activity. In situ DRIFT studies showed that NH3 can be adsorbed on both Brønsted and Lewis acid sites on Fe-ZSM-5 catalyst, and this adsorbed NH3 can react with gaseous NOx. Additionally, NOx can be adsorbed on Fe-ZSM-5 catalyst, mainly as a bidentate nitrate, but these nitrate species cannot be confirmed to react with gaseous NH3 because of the overlap with the strong absorption band of adsorbed NH3 species. Based on the IR results and weak adsorption of NOx over Fe-ZSM-5 catalysts, it was concluded that NH3-SCR over this Fe-ZSM-5 catalyst predominantly follows the Eley-Rideal reaction mechanism.
Co-reporter:Dongmei Meng, Wangcheng Zhan, Yun Guo, Yanglong Guo, Li Wang, and Guanzhong Lu
ACS Catalysis 2015 Volume 5(Issue 10) pp:5973
Publication Date(Web):September 1, 2015
DOI:10.1021/acscatal.5b00747
Sm-Mn mixed oxide catalysts prepared by the coprecipitation method were developed, and their catalytic activities were tested for the selective catalytic reduction (SCR) of NO with ammonia at low temperature. The results showed that the amount of Sm markedly influenced the activity of the MnOx catalyst for SCR, that the activity of the Sm-Mn mixed oxide catalyst exhibited a volcano-type tendency with an increase in the Sm content, and that the appropriate mole ratio of Sm to Mn in the catalyst was 0.1. In addition, the presence of Sm in the MnOx catalyst can obviously enhance both water and sulfur dioxide resistances. The effect of Sm on the physiochemical properties of the Sm-MnOx catalyst were investigated by XRD, low-temperature N2 adsorption, XPS, and FE-SEM techniques. The results showed that the presence of Sm in the Sm-MnOx catalyst can restrain the crystallization of MnOx and increase its surface area and the relative content of both Mn4+ and surface oxygen (OS) on the surface of the Sm-MnOx catalyst. NH3-TPD, NO-TPD, and in situ DRIFT techniques were used to investigate the absorption of NH3 and NO on the Sm-MnOx catalyst and their surface reactions. The results revealed that the presence of Sm in the Sm0.1-MnOx catalyst can increase the absorption amount of NH3 and NO on the catalyst and does not vary the SCR reaction mechanism over the MnOx catalyst: that is, the coexistence of Eley–Rideal and Langmuir–Hinshelwood mechanisms (bidentate nitrate is the active intermediate), in which the Eley–Rideal mechanism is predominant.Keywords: ammonia reducing agent; nitrogen oxide; role of Sm; selective catalytic reduction; Sm-Mn oxide catalyst
Co-reporter:Chenhao Du, Yun Guo, Yanglong Guo, Xue-qing Gong and Guanzhong Lu
Journal of Materials Chemistry A 2015 vol. 3(Issue 46) pp:23230-23239
Publication Date(Web):08 Oct 2015
DOI:10.1039/C5TA05092H
Developing methods for the fabrication of active and thermally stable noble metal/metal oxide nanomaterials are very important for catalysis and material fields. Herein, we used a polymer-template synthesis approach to prepare hollow Pd–CeO2 nanocomposite spheres (NCSs) with Pd nanoparticles evenly distributed inside the CeO2 shell, in which the aggregation of Pd nanoparticles can be well inhibited with the help of the protection of CeO2 nanocrystallites even after being calcined at 700 °C. The Pd nanoparticles are partially buried in the CeO2 shell and the surface Pd species are highly ionic, which is caused by the electron exchange at the Pd–CeO2 interface during calcination. This hollow structure Pd–CeO2 nanocatalyst shows excellent catalytic activity and stability in the aqueous selective reduction of 4-nitrophenol and gaseous CO oxidation. For the selective reduction of 4-nitrophenol, the reaction rate of this h-Pd–CeO2 NCS catalyst compared to those of the supported Pd/CeO2 and physically mixed Pd + CeO2 catalysts is almost 14 times and 5 times faster, respectively. For the CO oxidation, the larger Pd–CeO2 interface in h-Pd–CeO2 NCSs could facilitate the reaction between the adsorbed CO and O2, thus showing better low temperature activity. This paper emphasizes the advantages of a core–shell hollow structure and provides a new way for obtaining novel functional nanocatalysts.
Co-reporter:Qingping Ke, Bingyan Zhang, Bolun Hu, Yangxin Jin and Guanzhong Lu
Chemical Communications 2015 vol. 51(Issue 6) pp:1012-1015
Publication Date(Web):27 Nov 2014
DOI:10.1039/C4CC09260K
A new strategy for the synthesis of epoxides is presented. This process allows the direct synthesis of epoxides from alkenes and aldehydes through C–H functionalization and C–C/C–O bond formation.
Co-reporter:Xuexun Du, Hui-Ying Li, Jun Yu, Xiuzhen Xiao, Zhangping Shi, Dongsen Mao and Guanzhong Lu
Catalysis Science & Technology 2015 vol. 5(Issue 8) pp:3970-3979
Publication Date(Web):02 Jun 2015
DOI:10.1039/C5CY00545K
The Pd–Cu–Clx/Al2O3 catalysts (PCC) were prepared by a two-step impregnation (TI) method in organic solvent, wet impregnation (WI) method and NH3 coordination-impregnation (CI) method. The PCC-TI catalyst prepared by the two-step impregnation method (TI) exhibited much higher activity and stability for CO oxidation than the other catalysts, resulting from the smaller size of Cu2Cl(OH)3 and fewer carbonates deposited on the surface of PCC-TI catalyst. Using the PCC-TI catalyst, the complete conversion temperature of CO was 10 °C in the presence of 3.1% H2O. Among the three catalysts, the activation energy (Ea) of PCC-TI/ethanol was the lowest (27.1 kJ mol−1). The PCC-TI/ethanol prepared in ethanol solvent showed a higher activity compared with PCC-TI/methanol, due to much stronger interactions between the copper and palladium species. High concentrations of moisture and CO had a negative effect on the CO conversion. The former is due to excessive numbers of –OH groups (from H2O dissociation) which occupy the active sites of Pd and Cu, though –OH groups can work as part of the catalytic cycle, and the latter may originate from competitive adsorption and the presence of carbonates on the surface. We used DFT calculations to study the adsorption of H2O and CO on the surface, and the catalytic cycle of CO oxidation on the Pd species, revealing the possible routes for the formation of common species observed in the in situ DRIFTS spectra.
Co-reporter:Xin-Ping Wu, Xue-Qing Gong and Guanzhong Lu
Physical Chemistry Chemical Physics 2015 vol. 17(Issue 5) pp:3544-3549
Publication Date(Web):17 Dec 2014
DOI:10.1039/C4CP04766D
Diffusion processes and reactions of H at stoichiometric and reduced CeO2(111) surfaces have been studied by using density functional theory calculations corrected by on-site Coulomb interactions (DFT + U). Oxygen vacancies on the surface are determined to be able to significantly affect the behavior of H by modifying the charge of surface lattice O through the occurrence of Ce3+. It has been found that, at the reduced CeO2(111) surface, the adsorption strength of H as well as the H coupling barrier can be dramatically reduced compared to those at the stoichiometric surface, while H2O formation barrier is not significantly affected. Moreover, the diffusion of H at the reduced surface or into the bulk can occur more readily than that at stoichiometric CeO2(111).
Co-reporter:Yujie Xie, Yanyan Yu, Xueqing Gong, Yun Guo, Yanglong Guo, Yanqin Wang and Guanzhong Lu
CrystEngComm 2015 vol. 17(Issue 15) pp:3005-3014
Publication Date(Web):03 Mar 2015
DOI:10.1039/C5CE00058K
Nanosized MnO2 particles with α-, β-, γ-, and δ-crystal phases were synthesized hydrothermally, and characterized by XRD, SEM, HR-TEM, low temperature N2 adsorption, TPR, TPD, FT-IR and Raman spectroscopy. The density functional theory (DFT) method was used to calculate the adsorption of propane and O2 on MnO2 catalysts. The effect of the crystal phases or crystal plane figure on the catalytic properties of MnO2 for the total oxidation of propane was evaluated. The results showed that α-, β- and γ-MnO2 exhibited a 1D structure, and δ-MnO2 was a 2D layered-structure material. For deep oxidation of propane, the catalytic activities of the MnO2 samples decreased in the order of α- ≈ γ- > β- > δ-MnO2. Compared with the other three MnO2 samples, α-MnO2 exhibited the highest catalytic activity and stability for propane oxidation, its T10 and T90 were 204 °C and 290 °C, respectively. For the different crystal phases of MnO2, there are distinct differences in the chemical bonds (Mn–O–Mn and Mn–O) and linking modes of [MnO6] octahedra, the adsorption energies of propane on the surface of MnO2 are varied in the order of (310) facet of α- > (120) of γ- > (110) of β- > (001) of δ-MnO2, and the presence of translational motion in α-MnO2 along with its stronger deformation and stretching modes may lead to its better catalytic activity for propane oxidation.
Co-reporter:Yinli Liu, Huiying Li, Jun Yu, Dongsen Mao and Guanzhong Lu
Physical Chemistry Chemical Physics 2015 vol. 17(Issue 41) pp:27758-27768
Publication Date(Web):21 Sep 2015
DOI:10.1039/C5CP03394B
Density functional theory (DFT+U) was used to study the adsorption of Aux (x = 1–4) clusters on the defective CeO2(111) facet and CO adsorption on the corresponding Aux/CeO2−x catalyst, in this work Aux clusters are adsorbed onto the CeO2−x + superoxide/peroxide surface. When Au1 is supported on the CeO2(111) facet with an O vacancy, the strong electronegative Auδ− formed is not favorable for CO adsorption. When peroxide is adsorbed on the CeO2(111) facet with the O vacancy, Aux was oxidized, resulting in stable Aux adsorption on the defective ceria surface with peroxide, which promotes CO adsorption on the Aux/CeO2−x catalyst. With more Au atoms in supported Aux clusters, CO adsorption on this surface becomes stronger. During both the Au being supported on CeO2−x and CO being adsorbed on Aux/CeO2−x, CeO2 acts as an electron buffer that can store/release the electrons. These results provide a scientific understanding for the development of high-performance rare earth catalytic materials.
Co-reporter:Shuangshuang Lai, Dongmei Meng, Wangcheng Zhan, Yun Guo, Yanglong Guo, Zhigang Zhang and Guanzhong Lu
RSC Advances 2015 vol. 5(Issue 110) pp:90235-90244
Publication Date(Web):12 Oct 2015
DOI:10.1039/C5RA12505G
Cu/ZSM-5 and Ce doped Cu/ZSM-5 catalysts were prepared by the incipient-wetness-impregnation method, and the effect of Ce doping on the structure and the catalytic performance of the Cu/ZSM-5 catalyst was investigated in detail for the selective catalytic reduction (SCR) of NO with NH3. The results showed that the addition of Ce can markedly broaden the operation temperature window of the Cu/ZSM-5 catalyst for NH3-SCR and enhance its H2O and SO2 resistance. The presence of Ce promoted an enrichment of copper species (isolated Cu2+ ions and CuO nanoparticles) on the catalyst surface and the increase in the Lewis acid sites on the surface of the Cu/ZSM-5 catalyst, and strengthened the redox property of the Cu/ZSM-5 catalyst. As a result, Ce-doped Cu/ZSM-5 catalyst possessed the high adsorption ability of NH3 and nitrite/nitrate, which is propitious to the increase in the reactivity of the Ce-doped Cu/ZSM-5 catalyst. In situ DRIFTS results indicated that the NH3-SCR reaction on the Cu/ZSM-5 catalyst and Ce1–Cu4/ZSM-5 catalysts definitely followed Langmuir–Hinshelwood mechanisms, and bridged nitrates and bidentate nitrates were the active intermediate. However, Eley–Rideal mechanism can't be confirmed over the Cu/ZSM-5 and Ce1–Cu4/ZSM-5 catalysts.
Co-reporter:Miao Wang, Guanzhong Lu, Yanqin Wang, Yanglong Guo, Yun Guo
Microporous and Mesoporous Materials 2015 Volume 207() pp:163-169
Publication Date(Web):1 May 2015
DOI:10.1016/j.micromeso.2015.01.026
•Ellipsoidal mesoporous SBA-15 silica with a tunable aspect ratio were synthesized.•Mesoporous YVO4:Eu3+ ellipsoids were synthesized by nanocasting route with SBA-15.•Mesoporous YVO4:5%Eu3+ ellipsoids exhibit strongest red emission excited by UV light.•This meso-ellipsoidal luminescent material can be potentially used as biological probes.The mesoporous luminescent materials with streamline shape (as ellipsoids) as biological probes can be importantly and potentially used in biology and medicine fields. The ellipsoidal mesoporous SBA-15 silica with a tunable aspect ratio were synthesized by changing the ethanol amount in the synthesis solution. Hexagonal ordered mesoporous Eu3+-doped yttrium vanadate (YVO4:Eu3+) ellipsoids were successfully synthesized through the nanocasting route with a Y(NO3)3/Eu(NO3)3/NH4VO3/HNO3/ethanol solution as a guest unit and mesoporous SBA-15 silica ellipsoids as the hard template host, and characterized by XRD, SEM, TEM, low-temperature N2 adsorption and photo-luminescence (PL) spectra. The prepared mesoporous YVO4:Eu3+ ellipsoids possess larger surface area and pore volume, uniform pore size, and exhibits strong red emission at 618 nm excited by UV light. When the concentration of Eu3+ dopant is 5 mol.% (Y/Eu = 95/5), the highest PL intensity can be reached.
Co-reporter:Zhibin An, Xiuzhen Xiao, Jun Yu, Dongsen Mao and Guanzhong Lu
RSC Advances 2015 vol. 5(Issue 65) pp:52533-52542
Publication Date(Web):05 Jun 2015
DOI:10.1039/C5RA08993J
YPxV1−xO4 (x = 0.3–0.9) assembled spheres with tetragonal phase were prepared hydrothermally under a simple and mild method with the assistance of EDTA. The structures and shapes of the prepared samples were significantly affected by the reaction conditions (hydrothermal treatment time, organic additive, pH value and the amount of EDTA in the synthesis solution). The characteristic emission of the spherical YPxV1−xO4:Ln3+ (Ln = Eu, Sm, Dy or Tm) phosphors were investigated in detail. The results showed that the light color of the YP0.3V0.7O4 microspheres can be easily adjusted by doping different lanthanide activators; Y0.93Sm0.07P0.3V0.7O4 and Y0.95Eu0.05P0.3V0.7O4 exhibited strong orange-red and red emission, respectively, and Y0.93Sm0.07P0.3V0.7O4 has a higher quantum efficiency of 76.8%. For the Y0.97Dy0.03PxV1−xO4 (x = 0.3–0.9) samples, both emission intensities of Dy3+ and VO43− increase with increasing the P amount, and the quantum efficiency of Y0.97Dy0.03P0.9V0.1O4 can reach 92%. It can also be found that the light color of the Y0.97Dy0.03PxV1−xO4 samples can be tuned by changing the ratio of P/V, and Y0.97Dy0.03P0.5V0.5O4 can emit white light under UV excitation.
Co-reporter:Yu Fu, Wangcheng Zhan, Yanglong Guo, Yanqin Wang, Xiaohui Liu, Yun Guo, Yunsong Wang, Guanzhong Lu
Microporous and Mesoporous Materials 2015 Volume 214() pp:101-107
Publication Date(Web):15 September 2015
DOI:10.1016/j.micromeso.2015.05.004
•The surface properties of Ce-MCM-48 affect its reactivity for cyclohexane oxidation.•F-modified Ce-MCM-48 exhibits 8.9% conversion with 91.2% selectivity to KA oil.•The catalysts prepared exhibit the excellent reusability.Ce-doped MCM-48 (Ce-MCM-48) mesoporous molecular sieve was prepared hydrothermally and its surface was modified with organic groups or fluorine, and their physicochemical properties were characterized by XRD, low-temperature N2 adsorption, TEM, UV–visible and FT-IR spectroscopies, XPS and contact angle measurement. The results indicated that Ce species were highly dispersed on the MCM-48 materials as Ce3+ and Ce4+. After post-functionalization of Ce-MCM-48, the organic groups or fluorine species have been immobilized on the surface of Ce-MCM-48, but the chemical status of Ce species were hardly changed, and the post-functionalization improved the surface hydrophobicity of the Ce-MCM-48 sample. The catalytic activity testing for the oxidation of cyclohexane with molecular oxygen showed that, Ce-MCM-48 after post-functionalization exhibited the higher cyclohexane conversion and selectivity to cyclohexanol and cyclohexanone, 8.9% cyclohexane conversion with 91.2% selectivity to cyclohexanone and cyclohexanol could be achieved over the Ce-MCM-48 with F-modified catalyst, which was attributed to the proper modification of their surface properties including hydrophobicity and polarity. The F-modified catalyst also showed excellent reusability, and its catalytic performance has no obvious deterioration after being repeatedly used five times.
Co-reporter:Jie Zhang, Xue-Qing Gong, Guanzhong Lu
Surface Science 2015 Volume 632() pp:164-173
Publication Date(Web):February 2015
DOI:10.1016/j.susc.2014.10.009
•We study physicochemical properties of reconstructed CeO2(110)–2 × 1 surface.•We compare the O vacancy formation and diffusion on reconstructed surface with original CeO2(110).•Steric effect of reconstructed CeO2(110)–2 × 1 significantly affects the surface relaxation and charge distribution.•We calculate prototype CO oxidation through reaction with lattice O at reconstructed surface.•Occurrence of CO2 is favored over surface carbonate at the missing row area of reconstructed CeO2(110)–2 × 1.Density functional theory calculations with on-site Coulomb interaction correction (DFT + U) have been performed to study the structures and catalytic activities of 2 × 1 reconstructed surface of CeO2(110). The reconstructed surface gives better thermal stability compared with the bulk truncated one and exhibits unique surface activity. We comprehensively calculated the O vacancy formation and diffusion on the reconstructed surface and found that the vacancy formation energy corresponding to the removal of one subsurface four-fold coordinated O is 1.71 eV only, which is smaller than that of the top-surface O vacancy or the sub-surface O vacancy at the bulk truncated surface. Accordingly, the O vacancy diffusion at 2 × 1 reconstructed surface is also much more feasible than that at the unreconstructed CeO2(110) with the highest diffusion barrier of only 0.84 eV. By calculating the detailed pathways of CO reaction with lattice O, we found that CO2 can directly occur without forming a bent negatively charged CO2− intermediate on the reconstructed surface, which may reduce the chance for the carbonate formation. It has also been clearly shown that strong localization characteristics of Ce 4f orbital indeed favor electron transfer from reaction intermediates to the CeO2 support.
Co-reporter:Junpeng Yan;Xiuzhen Xiao;Jun Yu;Dongsen Mao;Guanzhong Lu
Crystal Research and Technology 2015 Volume 50( Issue 7) pp:580-593
Publication Date(Web):
DOI:10.1002/crat.201500095
The tetragonally double alkaline rare earth molybdates NaRe(MoO4)2 (Re = Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, and Er) micro-particles in aqueous solution of Re(NO3)3 and Na2MoO4 were prepared hydrothermally by a facile and effective EDTA-assisted method, and investigated by XRD, SEM, FE-SEM, photoluminescence (PL) excitation and emission spectra. The results showed that the radii of Re ions, pH and the molar ratio of Re(NO3)3/Na2MoO4 in the synthesis solution play an important role in controlling sizes, morphologies and luminescent properties of the final products. And the possible formation mechanism for the bipyramid-like structure and role of EDTA were discussed in detail. The microstructure and PL property of NaYxLa1-x(MoO4)2:10%Eu3+ was investigated, and it showed that NaY0.5La0.5(MoO4)2 exhibited regular sphere-like morphology and emitted the stronger red emission with better color purity than other products. When Tm3+, Dy3+ and Eu3+ with appropriate concentrations were used as dopants to modify this bipyramid NaY(MoO4)2 material, the white light emission material of NaY(MoO4)2:1%Tm3+-11%Dy3+-0.6%Eu3+ was successfully synthesized and its CIE chromaticity coordinates is (0.33, 0.33), which is the standard white light point. These novel white-light-emitting NaY(MoO4)2:1%Tm3+-11%Dy3+-0.6%Eu3+ with single phase would be a promising material in the WLED field.
Co-reporter:Yi Shao;Qineng Xia;Xiaohui Liu; Guanzhong Lu; Yanqin Wang
ChemSusChem 2015 Volume 8( Issue 10) pp:1761-1767
Publication Date(Web):
DOI:10.1002/cssc.201500053
Abstract
A simple Pd-loaded Nb2O5/SiO2 catalyst was prepared for the hydrodeoxygenation of biomass-related compounds to alkanes under mild conditions. Niobium oxide dispersed in silica (Nb2O5/SiO2) as the support was prepared by the sol–gel method and characterized by various techniques, including N2 adsorption, XRD, NH3 temperature-programmed desorption (TPD), TEM, and energy-dispersive X-ray spectroscopy (EDAX) atomic mapping. The characterization results showed that the niobium oxide species were amorphous and well dispersed in silica. Compared to commercial Nb2O5, Nb2O5/SiO2 has significantly more active niobium oxide species exposed on the surface. Under mild conditions (170 °C, 2.5 MPa), Pd/10 %Nb2O5/SiO2 was effective for the hydrodeoxygenation reactions of 4-(2-furyl)-3-buten-2-one (aldol adduct of furfural with acetone), palmitic acid, tristearin, and diphenyl ether (model compounds of microalgae oils, vegetable oils, and lignin), which gave high yields (>94 %) of alkanes with little CC bond cleavage. More importantly, owing to the significant promotion effect of NbOx species on CO bond cleavage and the mild reaction conditions, the CC cleavage was considerably restrained, and the catalyst showed an excellent activity and stability for the hydrodeoxygenation of palmitic acid with almost no decrease in hexadecane yield (94–95 %) in a 150 h time-on-stream test.
Co-reporter:Yutao Ren;Qun Shen;Yun Guo;Yanqin Wang;Yanglong Guo
Science China Chemistry 2015 Volume 58( Issue 1) pp:123-130
Publication Date(Web):2015 January
DOI:10.1007/s11426-014-5276-7
Pd-only three-way catalyst (TWC), Pd supported on washcoating (the mixture of alumina and Ce-Zr solid solution)/cordierite, was prepared and its catalytic performance and the operation window (λ-value) at 450 °C were evaluated with the simulated automotive exhaust feed gas. Surfactants such as Tween-80 and Span-20 were added in the process of preparing the catalyst in order to improve the thermal stability and catalytic performance of Pd-only TWC. The fresh and aged catalysts at 1000 °C for 4 h were characterized by low-temperature N2 adsorption, XRD, XPS, and H2-TPR techniques. The results show that the presence of surfactants in the synthesis slurry could influence the physicochemical properties of the final Pd-only TWC. The FTS catalyst prepared with the mixed surfactant of Tween-80 and Span-20 exhibited excellent three-way catalytic performance. After being aged at 1000 °C for 4 h, the catalytic performances of Pd-only TWCs slightly decreased, but the FTS catalyst still demonstrated higher catalytic performance and better thermal stability compared with the Pd-only catalysts prepared with single surfactant or without any surfactant. And the FTS catalyst has a wider λ value (operation window) than other catalysts, even after being aged at 1000 °C.
Co-reporter:Xiang Zheng;Yang-Long Guo;Yun Guo;Qing Zhang;Xiao-Hui Liu;Li Wang
Rare Metals 2015 Volume 34( Issue 7) pp:477-490
Publication Date(Web):2015 July
DOI:10.1007/s12598-015-0500-y
The unsupported Cu and Ag catalysts with different oxidation states were prepared, and their catalytic performances for propylene epoxidation were investigated. The metallic Cu catalyst exhibits much higher catalytic activity and propylene oxide (PO) selectivity than Cu2O and CuO catalysts. The Cu0 species are the main active sites for propylene epoxidation, but Cu2O and CuO species are in favor of CO2 and acrolein production. The PO selectivity of 54.2 % and propylene conversion of 2.6 % can be achieved over the metallic Cu catalyst at 160 °C in initial stage, but metallic Cu catalyst would be oxidized to Cu2O during propylene epoxidation, resulting in a sharp decrease in the PO selectivity and propylene conversion. Nanosize AgCux bimetallic catalysts were prepared. It is found that adding Ag to the metallic Cu catalysts can prevent the oxidation of Cu and make AgCux bimetallic catalysts more stable under the condition of propylene epoxidation. The Ag/Cu molar ratio can remarkably affect the catalytic performance of AgCux catalyst and the selectivity to PO and acrolein. After AgCux was supported on MOx-modified α-Al2O3, its catalytic performance can be improved and has a close relationship with the acid–base property of support.
Co-reporter:Yang Lou, Jian Ma, Xiaoming Cao, Li Wang, Qiguang Dai, Zhenyang Zhao, Yafeng Cai, Wangcheng Zhan, Yanglong Guo, P. Hu, Guanzhong Lu, and Yun Guo
ACS Catalysis 2014 Volume 4(Issue 11) pp:4143
Publication Date(Web):October 6, 2014
DOI:10.1021/cs501049r
The doping of In2O3 significantly promoted the catalytic performance of Co3O4 for CO oxidation. The activities of In2O3–Co3O4 increased with an increase in In2O3 content, in the form of a volcano curve. Twenty-five wt % In2O3–Co3O4 (25 InCo) showed the highest CO oxidation activity, which could completely convert CO to CO2 at a temperature as low as −105 °C, whereas it was only −40 °C over pure Co3O4. The doping of In2O3 induced the expansion of the unit cell and structural distortion of Co3O4, which was confirmed by the slight elongation of the Co–O bond obtained from EXAFS data. The red shift of the UV–vis absorption illustrated that the electron transfer from O2– to Co3+/Co2+ became easier and implied that the bond strength of Co–O was weakened, which promoted the activation of oxygen. Low-temperature H2-TPR and O2-TPD results also revealed that In2O3–Co3O4 behaved with excellent redox ability. The XANES, XPS, XPS valence band, and FT-IR data exhibited that the CO adsorption strength became weaker due to the downshift of the d-band center, which correspondingly weakened the adsorption of CO2 and obviously inhibited the accumulation of surface carbonate species. In short, the doping of In2O3 induced the structural defects, modified the surface electronic structure, and promoted the redox ability of Co3O4, which tuned the adsorption strength of CO and oxygen activation simultaneously.Keywords: CO adsorption strength; CO oxidation; Co3O4; In2O3; redox ability; surface carbonate species
Co-reporter:Daqian Ding, Jianjian Wang, Jinxu Xi, Xiaohui Liu, Guanzhong Lu and Yanqin Wang
Green Chemistry 2014 vol. 16(Issue 8) pp:3846-3853
Publication Date(Web):19 Jun 2014
DOI:10.1039/C4GC00737A
Direct catalytic conversion of cellulose to levulinic acid (LA) by niobium-based solid acids and further upgrading to γ-valerolactone (GVL) on a Ru/C catalyst were realized through sequential reactions in a reactor. Firstly, using aluminium-modified mesoporous niobium phosphate as a catalyst, cellulose can be directly converted to LA with as high as 52.9% yield in aqueous solution, even in the presence of the Ru/C catalyst. To the best of our knowledge, this is the best result over a heterogeneous catalyst so far. It was found that the type of acid (Lewis and Brønsted acids) and acid strength had an influence on the yield of LA; the doping of aluminium can enhance the strong Lewis and Brønsted acids, especially the strong Lewis acid, thus resulting in the increase of LA yield from cellulose as well as from glucose and HMF. Such an enhancement by a Lewis acid on LA yield from HMF was further confirmed by adding lanthanum trifluoroacetate [(TfO)3La], a strong Lewis acid, in the catalytic system (HCl, (TfO)3H, niobium phosphate), indicating that a suitable ratio of Lewis/Brønsted acid is important for higher selectivity to LA from HMF, as well as from cellulose. Then, after replacing N2 with H2, the generated LA in the reaction mixture can be directly converted to γ-valerolactone through hydrogenation over the Ru/C catalyst without further separation of LA.
Co-reporter:Yang Lou, Xiao-Ming Cao, Jinggang Lan, Li Wang, Qiguang Dai, Yun Guo, Jian Ma, Zhenyang Zhao, Yanglong Guo, P. Hu and Guanzhong Lu
Chemical Communications 2014 vol. 50(Issue 52) pp:6835-6838
Publication Date(Web):20 Mar 2014
DOI:10.1039/C4CC00036F
Highly efficient In2O3–Co3O4 catalysts were prepared for ultralow-temperature CO oxidation by simultaneously tuning the CO adsorption strength and oxygen activation over a Co3O4 surface, which could completely convert CO to CO2 at temperatures as low as −105 °C compared to −40 °C over pure Co3O4, with enhanced stability.
Co-reporter:Zhangping Shi, Xiuzhen Xiao, Dongsen Mao and Guanzhong Lu
Catalysis Science & Technology 2014 vol. 4(Issue 4) pp:1132-1143
Publication Date(Web):22 Jan 2014
DOI:10.1039/C3CY00937H
The effects of the preparation method on the properties of Cu/ZnO/Al2O3 catalysts for L-phenylalanine methyl ester hydrogenation to L-phenylalaninol were investigated in detail, including the precipitation method and conditions (the aging time, calcination temperature and so on), with the help of ICP-OES, N2 and N2O adsorption, XRD, H2-TPR and TEM techniques. The results show that physicochemical properties of the catalysts are greatly affected by the preparation method and conditions. The uniform size distribution of CuO species can be obtained by fractional co-precipitation. The appropriate aging time is 2 h, and the catalyst aged for 2 h has the largest metallic copper surface area (SCu) and surface copper amount and the smallest CuO crystallites. The lower calcination temperature is favorable for increasing the surface area and metallic copper surface area of the catalyst. The spinel structure CuAl2O4 phase can form after calcination at 550 °C. The turnover frequency (TOF) values of L-phenylalaninol formed using different catalysts indicate the structurally sensitive character of the title reaction, and SCu is not the sole cause affecting the catalytic activities of the catalysts. B-TOF on the basis of the active sites (Cu0) in the boundary between CuO and ZnO or Al2O3 was proposed; the relationships of B-TOF with dCuO (particle size of CuO) and SCu were established. Using the Cu/ZnO/Al2O3 catalyst prepared by fractional co-precipitation with aging at 70 °C for 2 h and calcination at 450 °C for 4 h, 83.6% selectivity to L-phenylalaninol without racemization was achieved.
Co-reporter:Jie Li, Guanzhong Lu, Guisheng Wu, Dongsen Mao, Yanglong Guo, Yanqin Wang and Yun Guo
Catalysis Science & Technology 2014 vol. 4(Issue 5) pp:1268-1275
Publication Date(Web):22 Jan 2014
DOI:10.1039/C3CY01004J
Co3O4 catalysts supported on TiO2 with different crystalline structures (anatase (A), rutile (R) and P25 (Degussa)) were prepared by a deposition–precipitation method, and characterized by nitrogen adsorption/desorption, XRD, HR-TEM, EPR, Raman spectroscopy, XPS and H2-TPR techniques. The results show that Co3O4/TiO2 (A) exhibited the highest activity among the three Co3O4/TiO2 catalysts: CO can be completely oxidized to CO2 at −43 °C. When rutile TiO2 or P25 were used as the support, its catalytic activity was decreased obviously, because the TiO2 crystal structure has an influence on the physicochemical and catalytic properties of the Co3O4 catalysts. The results show that the Co3O4/TiO2 (A) catalyst contains Ti3+ species, which is in an unstable state and can affect the properties of Co3O4 by the interaction between the deposited Co3O4 and anatase TiO2 support. The Co3O4/TiO2 (A) catalyst exhibits highly defective structure and good oxygen adsorption ability. The reducibility of Co3O4 is improved by the anatase TiO2 support, resulting in Co3O4/TiO2 (A) possessing the better redox property than the other Co3O4/TiO2 catalysts, which is an important factor for its high catalytic activity.
Co-reporter:Jie Zhang, Xue-Qing Gong and Guanzhong Lu
Physical Chemistry Chemical Physics 2014 vol. 16(Issue 32) pp:16904-16908
Publication Date(Web):30 Jun 2014
DOI:10.1039/C4CP02235A
NO adsorption, diffusion and reaction at reduced CeO2(110) were studied by density functional theory calculations. NO accommodated by O vacancies can readily diffuse via alternate NO2 formation and dissociation, facilitating N2O2 formation and subsequent reduction to N2. Rare earth ceria plays an important catalytic role in both static and dynamic ways by tuning the electron distribution in adsorbates and reacting molecules.
Co-reporter:Jianjian Wang, Xiaohui Liu, Bicheng Hu, Guanzhong Lu and Yanqin Wang
RSC Advances 2014 vol. 4(Issue 59) pp:31101-31107
Publication Date(Web):22 Jul 2014
DOI:10.1039/C4RA04900D
Efficient production and sequential utilization of furan derivatives will provide a promising approach towards achieving renewable liquid biofuels from biomass. This study aims to investigate the simultaneous production of furfural and 5-(hydroxymethyl)furfural (HMF) from biomass and further upgrade them into biofuels. Firstly, furfural and HMF are obtained together with high yields from a mixture of C5 (xylose) and C6 (glucose) sugars, or from lignocellulosic biomass, such as birch, cornstalk, pine, bagasse, and poplar in a tetrahydrofuran (THF)/H2O–NaCl biphasic system under mild conditions. The co-existence of C5/C6 sugars or impurities in lignocellulosic biomass has little influence on the simultaneous production of furfural and HMF. Then, the generated furfural and HMF in the upper organic phase are directly used as substrates without extra separation and purification processes, and efficiently upgraded to 2-methylfuran (MF) and 2,5-dimethylfuran (DMF), both of which are considered as promising renewable liquid biofuels with high-energy content. Hence, the seamless integration of lignocellulosic biomass into renewable liquid biofuels will accelerate our society moving towards a renewable transportation economy by utilizing cheap feedstocks, mild reaction conditions, and cost saving in separation and purification.
Co-reporter:Wangcheng Zhan, Junming Yao, Zhun Xiao, Yanglong Guo, Yanqin Wang, Yun Guo, Guanzhong Lu
Microporous and Mesoporous Materials 2014 Volume 183() pp:150-155
Publication Date(Web):1 January 2014
DOI:10.1016/j.micromeso.2013.08.038
•The surface properties of SBA-15 support largely influences the catalytic performance of Ti-SBA-15 for the epoxidation of propylene.•Silylation treatment can further improve the performances of Ti-SBA-15 catalyst for epoxidation of propylene.•The CHP conversion of 90.3% and the PO selectivity to CHP of 96.2% can be achieved over silylated Ti-SBA-15 catalyst.Ti-SBA-15 catalysts were prepared by the chemical vapor deposition (CVD) method using TiCl4 as titanium source and characterized by XRD, N2 desorption, FT-IR and UV–vis spectroscopies, and TG analysis. The effects of SBA-15 support and silylation on the catalytic performances of Ti-SBA-15 catalysts for the propylene epoxidation using cumene hydroperoxide (CHP) as the oxidant were investigated. The results show that SBA-15 supports prepared with different methods have different surface properties, leading to the difference on the amount and the status of Ti deposited on the SBA-15 surface and different catalytic performances. On the other hand, the silylated Ti-SBA-15 catalysts exhibit higher activities than the unsilylated Ti-SBA-15 catalyst due to the increase of the hydrophobicity of the catalyst, which originates from the impact of methyl groups anchored on the surface of Ti-SBA-15 catalysts. The silylated Ti-SBA-15 catalyst prepared with reflux for 6 h exhibits the best epoxidation performances, over which CHP conversion of 90.3% and PO selectivity to CHP of 96.2% can be obtained.
Co-reporter:Ling Yang, Yanglong Guo, Wangcheng Zhan, Yun Guo, Yunsong Wang, Guanzhong Lu
Microporous and Mesoporous Materials 2014 Volume 197() pp:1-7
Publication Date(Web):October 2014
DOI:10.1016/j.micromeso.2014.05.044
•Fe3O4/CHO-SiO2 sample with cannular structure was prepared by one-pot synthesis.•PGA was covalently immobilized on the surface of Fe3O4/CHO-SiO2 sample.•PGA/Fe3O4/CHO-SiO2 sample had high initial activity and operational stability.•PGA/Fe3O4/CHO-SiO2 sample was easily recycled by an external magnetic field.Aldehyde-functionalized mesoporous silica-Fe3O4 nanocomposites, one-pot synthesized by co-condensation of tetraethylorthosilicate and trimethoxysilylpropanal in presence of triblock copolymer of Pluronic P123, NaCl and Fe3O4 nanoparticles in the neutral solution, were characterized by SAXS, XRD, TEM, nitrogen sorption, FT-IR, TG, elementary analysis and magnetic susceptibility measurements, and investigated as the supports for covalent immobilization of penicillin G acylase (PGA). The results show that paramagnetic Fe3O4 nanoparticles were embedded among the cannular mesoporous silica layers and the aldehyde groups were condensed on the surface of mesoporous silica. PGA was covalently immobilized on these paramagnetic nanocomposites via the reaction to produce Schiff’s base between the free amino groups of lysine residues of PGA and the aldehyde groups on the surface of these nanocomposites. PGA immobilized on these paramagnetic nanocomposites had better operational stability and was easily recycled by an external magnetic field. The immobilized PGA had the initial activity of 6231 U g−1 and the operational stability of 91.0% of the initial activity after recycled for 10 times.Graphical abstract
Co-reporter:Hongzhen Xie, Guanzhong Lu
Journal of Luminescence 2014 Volume 145() pp:119-124
Publication Date(Web):January 2014
DOI:10.1016/j.jlumin.2013.07.034
•Tb3+- and Eu3+-dpphen complexes exhibit strong green and red light respectively.•Luminescence of ligand is suppressed in complexes due to efficient ligand-to-metal energy transfer.•Three 1D chain-like new coordination polymers were synthesized hydrothermally.•Three lanthanide coordination polymers exhibit good thermal stability.Three new lanthanide complexes [Ln(dpphen)(L)(NO3)] (Ln=Tb(1), Eu(2), Nd(3), H2L=glutaric acid, dpphen=4,7-diphenyl-1,10-phenanthroline) have been synthesized hydrothermally by the reaction of H2L, dpphen and Ln(III) ions. The X-ray diffraction analysis reveals that three coordination polymers have similar structures. The Ln(III) ions are nine coordinated and glutarate ligands bridge Ln(III) to form 1D polymer chains. The solid-state luminescence of complexes 1 and 2 was investigated at room temperature. The complexes 1 and 2 exhibited strong green and red luminescence under ultraviolet light. The 5D4→7Fj (j=6, 5, 4 and 3) transition emissions of Tb(III) and the 5D0→7Fj (j=0–4) transition emissions of Eu(III) were observed in their emission spectra. The strong luminescence of complexes 1 and 2 demonstrates that luminescence of lanthanide coordination polymers is sensitized by an effective energy-transfer from dpphen ligand to Ln(III) ions. Moreover, the magnetic properties of complexes 1–3 were also investigated.Three new coordination polymers, [Ln(dpphen)(L)(NO3)] (Ln=Tb(1), Eu(2), Nd(3), H2L=glutaric acid) were synthesized hydrothermally. Ln(III) ions are nine coordinated and the glutarate ligands bridge the Ln(III) to from 1D polymer chains. The complexes Tb(III) and Eu(III) exhibit strong green and red luminescence respectively.
Co-reporter:Yang Yu, Yanglong Guo, Wangcheng Zhan, Yun Guo, Yunsong Wang, Guanzhong Lu
Journal of Molecular Catalysis A: Chemical 2014 Volume 392() pp:1-7
Publication Date(Web):October 2014
DOI:10.1016/j.molcata.2014.04.038
•Cu–ZnO–SiO2 catalyst showed better catalytic performance and stability.•Ba as a promoter can further improve greatly the catalyst stability.•Higher Cu surface area and ZnO dispersion can suppress the catalyst deactivation.Cu-ZnO-SiO2 (CZS) catalysts, prepared by the coprecipitation method, were investigated for gas-phase hydrogenation of maleic anhydride (MA) to γ-butyrolactone (GBL) at atmospheric pressure and characterized by XRD, N2O chemisorption, SEM and TGA. Effects of the compositions and the promoters on the catalytic performance and stability of CZS catalysts were investigated, in which CZS111 catalyst with the molar ratio of Cu:Zn:Si = 1:1:1 showed better catalytic performance and stability. The results show that the introduction of Ba as a promoter to CZS111 catalyst can further improve greatly the catalyst stability by increasing Cu surface area and ZnO dispersion with more additional adsorption sites for succinic anhydride (SA) to suppress the adsorption and polymerization of SA on the active sites of Cu0. The possible reaction pathways were proposed for gas-phase hydrogenation of MA to GBL, which could explain well the effect of Ba as a promoter on the stability of CZS111 catalyst.
Co-reporter:Ling Yang, Zhenyuan Gao, Yanglong Guo, Wangcheng Zhan, Yun Guo, Yunsong Wang, Guanzhong Lu
Microporous and Mesoporous Materials 2014 190() pp: 17-25
Publication Date(Web):
DOI:10.1016/j.micromeso.2014.01.017
Co-reporter:Zengzan Zhu, Guanzhong Lu, Zhigang Zhang, Yun Guo, Yanglong Guo, and Yanqin Wang
ACS Catalysis 2013 Volume 3(Issue 6) pp:1154
Publication Date(Web):April 16, 2013
DOI:10.1021/cs400068v
Co3O4 supported on ZSM-5 (Co3O4/ZSM-5) catalysts were prepared by impregnation (IM), deposition precipitation (DP), and hydrothermal (HT) methods. Their catalytic performances for the total oxidation of propane were tested, and their physicochemical properties were investigated by low-temperature N2 adsorption, XRD, FT-IR absorption spectroscopy, XPS, H2-TPR, TEM, and CO chemisorption. The results show that the catalytic activity of Co3O4/ZSM-5 for propane oxidation is higher than that of 1.5 wt % Pd/ZSM-5, and the preparation methods remarkably affect the catalytic activity of Co3O4/ZSM-5. Among four Co3O4/ZSM-5 catalysts prepared by different methods, the catalyst prepared by the HT method possesses the highest catalytic activity for propane oxidation, and their catalytic activities are varied in the order of HT > DP > IM. For the Co3O4/ZSM-5 (DP) catalysts, the precipitant has an evident influence on their catalytic activities. For instance, the DP catalyst prepared with ammonium bicarbonate precipitant has a higher catalytic activity than the catalyst prepared with sodium hydroxide precipitant. The excellent catalytic activity of Co3O4/ZSM-5 (HT) may be attributed to the better reducibility of Co3+, higher Co3+ content, higher surface concentration, and fast migration of the lattice oxygen of Co3O4 on this catalyst. Furthermore, the Co3O4/ZSM-5 catalyst prepared by the HT method exhibits a high stability after being used at 500 °C for 40 h.Keywords: catalyst preparation; Co3O4/ZSM-5; high activity; high stability; propane oxidation
Co-reporter:Haixiang Tao, Hong Yang, Yanhui Zhang, Jiawen Ren, Xiaohui Liu, Yanqin Wang and Guanzhong Lu
Journal of Materials Chemistry A 2013 vol. 1(Issue 44) pp:13821-13827
Publication Date(Web):07 Oct 2013
DOI:10.1039/C3TA12989F
The sole presence of relatively small micropores in zeolite catalysts strongly influences the mass transfer and catalytic conversion of bulky molecules. Herein, we report a novel synthesis route for the confined synthesis of hierarchical MFI zeolite microspheres with nanorod oriented-assembled structures for the first time via the hydrothermal crystallization of a carbon–silica composite monolith. The growth of such unique zeolite microspheres undergoes a reversed crystal-growth route. Crystallization started on the outer surface of the amorphous particles, then extended to the core and finally resulted in nanorod oriented-assembled structures, due to the confined-space effect of carbon in the carbon–silica monolith. The novel hierarchical zeolite microspheres (5–10 μm), including Silicalite-1, ZSM-5 and TS-1, composed of oriented-assembled nanorods (50–100 nm in width) are easy for separation and have inter-crystalline mesoporous networks between the nanorods; the latter are favourable for mass transfer. More importantly, the hierarchical zeolite microspheres Hier-ZSM-5 and Hier-TS-1 show much higher catalytic activities for bulky substrate conversion than the conventional ZSM-5 and TS-1, respectively. Thus, the novel hierarchical zeolite microspheres reported here show a great potential for industrial applications.
Co-reporter:Chunyou Gao, Xiuzheng Xiao, Dongsen Mao and Guanzhong Lu
Catalysis Science & Technology 2013 vol. 3(Issue 4) pp:1056-1062
Publication Date(Web):12 Dec 2012
DOI:10.1039/C2CY20763J
The Cu/ZnO/Al2O3 catalyst for hydrogenation of L-phenylalaninate to L-phenylalaninol was prepared by a co-precipitation method, and characterized by XRD, low-temperature N2 adsorption, H2-TPR, N2O chemisorption and ICP-AES. The results show that the physicochemical properties of the catalyst are greatly affected by the ZnO amount, and that the exposed copper surface area, dispersion of CuO and BET surface area of the Cu/ZnO/Al2O3 catalyst (Cu/Zn/Al = 1.0:0.3:1.0) reach the largest. The chemoselectivity of L-phenylalaninol is changed with ZnO amount in the Cu/ZnO/Al2O3 catalyst, and when Cu/Zn/Al = 1.0:0.3:1.0, the catalyst exhibits higher catalytic performance and chemoselectivity to L-phenylalaninol. Furthermore, the effect of temperature, pressure, reaction time and the molar ratio of catalyst to ester on the catalytic hydrogenation of L-phenylalaninate were investigated. When the catalytic hydrogenation of L-phenylalaninate was operated at 110 °C and 4 MPa of H2 for 5 h, the yield of L-phenylalaninol can reach 69.2 %, and its ee selectivity is 99.84 %.
Co-reporter:Jie Li, Guanzhong Lu, Guisheng Wu, Dongsen Mao, Yanglong Guo, Yanqin Wang and Yun Guo
RSC Advances 2013 vol. 3(Issue 30) pp:12409-12416
Publication Date(Web):16 May 2013
DOI:10.1039/C3RA41272E
A series of iron modified cobalt oxide catalysts (FeaCobOx (b:a = MCo:MFe, 10 < x < 15)) were prepared by a co-precipitation method, characterized by nitrogen adsorption–desorption, XRD, Raman spectroscopy, XPS, H2-temperature programmed reduction, CO-temperature-programmed desorption, O2-temperature-programmed desorption and time-resolved CO titration, and their catalytic activities for CO oxidation were evaluated. When Co:Fe is 8:2 (mol), the Fe2Co8Ox catalyst exhibits a very high catalytic activity, in which CO can be completely converted to CO2 at −80 °C. The results show that the addition of Fe to Co3O4 can increase its surface area and inhibit the agglomeration of iron oxide, improve the reduction behaviour of Co3O4, optimize the ratio of Co3+:Co2+ on the catalyst surface, and promote CO adsorption and CO2 desorption on the catalyst surface. The oxygen species on Fe2Co8Ox are more active than those on Co3O4, and when the feed gas is lacking in oxygen the lattice oxygen of Fe2Co8Ox can easily overflow to the surface to participate in the oxidation of CO.
Co-reporter:Xiaofei Chang, Guanzhong Lu, Yun Guo, Yanqin Wang, Yanglong Guo
Microporous and Mesoporous Materials 2013 Volume 165() pp:113-120
Publication Date(Web):1 January 2013
DOI:10.1016/j.micromeso.2012.07.040
A NOx adsorbent of H-beta zeolites modified with calcium oxide (Ca-beta) was prepared by an incipient wetness impregnation method, and characterized by XRD, N2 adsorption/desorption, CO2-TPD, NO-TPD and in situ FT-IR spectroscopy. The results show that the CaO loading amount affects obviously the textural structure properties and adsorption capacity of Ca-beta for NOx, and the presence of O2 in the feed gas is in favor of oxidizing NO to NO2 and promoting NO adsorption on Ca-beta. The presence of water vapor in feed gas can partly destroy the selective adsorption sites and block the micropore, resulting in lowering the adsorption property of Ca-beta. There are two kinds of adsorption sites for adsorbing NOx on Ca-beta, which are weak base sites on H-beta zeolites and strong sites from supported CaO, respectively. The in situ FT-IR spectra show that the NOx species absorbed on Ca-beta are mainly the NO3-, NO2- and NO+ species, among which the concentration of NO3- species is the highest and the second is NO2-. The NO3- species adsorbed on Ca-beta can be decomposed and desorbed at 500–550 °C.Graphical abstractHighlights► H-beta zeolite modified with CaO is a high effective NOx adsorbent. ► CaO amount affects obviously the textural structure and NOx adsorptivity of Ca-beta. ► O2 in feed gas promotes NO adsorption on Ca-beta and vapor lowers NOx adsorption on it. ► NOx absorbed species on Ca-beta are mainly NO3-, secondly NO2- and a little NO+.
Co-reporter:Jian Jiang, Guanzhong Lu, Changxi Miao, Xing Wu, Wenhai Wu, Qing Sun
Microporous and Mesoporous Materials 2013 Volume 167() pp:213-220
Publication Date(Web):February 2013
DOI:10.1016/j.micromeso.2012.09.006
The X molecular sieve catalysts modified by several alkali metal ions for the side-chain alkylation of toluene with methanol were prepared by an ion exchange method, and characterized by low temperature N2 adsorption, DTA, XRD, SEM, FT-IR and 27Al solid NMR. The effects of the reaction conditions (the reaction temperature, space velocity and reactant composition) on the side-chain alkylation of toluene with methanol and the effects of different ions and ratio of SiO2/Al2O3 on the catalytic performance of the KCsX catalyst were investigated. The results show that the X molecular sieve catalyst modified by several alkali metal ions exhibits much higher catalytic performance than the one modified by single alkali metal ions and the catalyst with lower ratio of SiO2/Al2O3 has higher activity for the side-chain alkylation of toluene with methanol. And the acid–base property of the catalyst affects obviously the methanol utilization efficiency and selectivity to product. A low temperature is in favor of increasing the selectivity to styrene, and high space velocity helps to increase the methanol utilization efficiency. With an increase in the reaction temperature, this catalyst would be deactivated due to the coke deposition on the catalyst and the slight structure damage, which results from small part of framework Al has transformed to extra-framework Al.Graphical abstractThe X molecular sieve exchanged by alkali metal ions exhibits an excellent performance for the side-chain alkylation of toluene with methanol. The performance of the KRbCs-X catalyst is higher than that of X modified by single ions and the catalyst with lower Si/Al exhibits higher activity.Highlights► X molecular sieve exchanged by alkali metal ions was developed. ► Modified X is an excellent catalyst for side-chain alkylation (SCA) of toluene. ► KRbCs-X catalyst behaves higher performance than X modified by single ions. ► Catalyst with lower Si/Al exhibits higher activity for SCA of toluene.
Co-reporter:Ya-Ling Song, Li-Li Yin, Jie Zhang, P. Hu, Xue-Qing Gong, Guanzhong Lu
Surface Science 2013 Volume 618() pp:140-147
Publication Date(Web):December 2013
DOI:10.1016/j.susc.2013.09.001
•We calculate CO oxidation at defect CeO2 surfaces.•We illuminate the effect of O vacancies on the reactivities of nearby surface O.•CO adsorption is generally weak at defect CeO2 surfaces.•O vacancies can affect the various properties of reaction intermediate states.•Occurrence of CO2 can be favored over surface carbonate at defect CeO2 surfaces.Density functional theory calculations corrected by on-site Coulomb interaction have been conducted to illuminate the effect of O vacancies on the surface reactivities toward direct CO oxidation at CeO2(110) and (111). CO adsorption at and further reaction with various surface O at the vacancy were systematically calculated, and extensive geometric and electronic analyses were also performed to understand the calculation results. It has been shown that though the existence of O vacancy can reduce the activities of neighboring O as the barriers of elementary steps are generally higher than those at stoichiometric surfaces, the relative preference for CO2 desorption is also increased due to the missing of nearby O for carbonate formation. Moreover, our calculation results also showed that the characteristic localized 4f orbitals/electrons of Ce still play the key role in determining the surface reactivities as the vacancy induced localized electrons can hinder their further occurrence and the corresponding reactions.
Co-reporter:Hongzhen XIE, Guanzhong LU
Journal of Rare Earths 2013 Volume 31(Issue 6) pp:639-644
Publication Date(Web):June 2013
DOI:10.1016/S1002-0721(12)60334-2
Five lanthanide complexes of Ln2(dpdc)2(tpy)2(NO3)2(H2O)2 [Ln=La (1), Ce (2), Pr (3), Sm (4), Gd (5), H2dpdc=2,2’-biphenyldicarboxylic acid and tpy=2,2′:6′,2″-terpyridine] were prepared at room temperature and characterized by X-ray diffraction, FT-IR and thermo-gravimetric analysis. The results showed that complexes 1–5 were isostructural and consisted of dinuclear units [Ln2(dpdc)2(tpy)2(NO3)(H2O)2] bridged by two dpdc2− ligands. The dinuclear units with strong intramolecular hydrogen bonds were assembled into 2D supramolecular layers by the weak π…π staking interactions between pyridine rings of tpy. The TG analysis showed that the complexes 1–5 behaved higher thermal stability with no mass loss at < 320 °C. The lanthanide contraction effect and the solid state luminescence properties of complexes 1–5 were also investigated. The luminescence emission spectra of complexes 1–5 exhibited ligands emission bands and complex 3 and 4 had no typical emission in the visible region.2D supramolecular layer of the complex 1 assembled by π…π stacking interaction (hydrogen atoms and dpdc2- except for O atoms are omitted for clarity, and the dash lines are intramolecular hydrogen bonds)
Co-reporter:Changli Shen;Dr. Huiying Li;Jun Yu; Guisheng Wu; Dongsen Mao; Guanzhong Lu
ChemCatChem 2013 Volume 5( Issue 10) pp:2813-2817
Publication Date(Web):
DOI:10.1002/cctc.201300356
Co-reporter:Zengzan Zhu; Guanzhong Lu; Yun Guo; Yanglong Guo;Zhigang Zhang; Yanqin Wang ; Xue-Qing Gong
ChemCatChem 2013 Volume 5( Issue 8) pp:2495-2503
Publication Date(Web):
DOI:10.1002/cctc.201300101
Abstract
Tungsten-modified 1.5 wt. % platinum supported on ZSM-5 catalysts were prepared, and their performances for the total oxidation of propane and the role of tungsten in the catalysts were investigated. The results show that the addition of tungsten can improve the catalytic activity of Pt/ZSM-5. When the tungsten loading is 5 wt. %, the Pt-5W/ZSM-5 catalyst demonstrates excellent catalytic activity and its turnover frequency is more than 1 order of magnitude higher than that of the Pt/ZSM-5 catalyst. Analyses of the surface properties of catalysts reveal that metallic platinum is scarcely found on the Pt/ZSM-5 catalyst without tungsten; the addition of tungsten can modify the nature of platinum species, which results in the presence of metallic platinum in the Pt-W/ZSM-5 catalyst. The amount of metallic platinum in the Pt-W/ZSM-5 catalyst depends on the tungsten loading and can correlate directly with its catalytic activity. Therefore, the oxidation resistance of platinum in the Pt-W/ZSM-5 catalyst seems to be responsible for the improved catalytic activity in propane oxidation. In addition, the Pt-5W/ZSM-5 catalyst demonstrates higher stability; no deactivation of the Pt-W/ZSM-5 catalyst is observed after the online test for 50 h, with the temperature alternating between 200 °C for 10 h and 500 °C for 10 h. Therefore, the Pt-5W/ZSM-5 catalyst demonstrates better catalytic activity for propane oxidation than the Pt/ZSM-5 catalyst after online aging at 700 °C for 30 h.
Co-reporter:Jun Yu, Dongsen Mao, Lupeng Han, Qiangsheng Guo, Guanzhong Lu
Journal of Molecular Catalysis A: Chemical 2013 Volume 367() pp:38-45
Publication Date(Web):February 2013
DOI:10.1016/j.molcata.2012.10.022
A series of Rh–Mn–Li catalysts supported on SiO2 prepared by different methods were tested for the synthesis of C2+ oxygenates via CO hydrogenation. The catalysts were comprehensively characterized by N2 adsorption–desorption, XRD, in situ FT-IR, CO-TPD, TPSR, and H2-TPR. It was found that the Rh–Mn–Li catalyst supported on the SiO2 synthesized by the Stöber method exhibited the highest CO conversion and selectivity toward C2+ oxygenates compared with other catalysts. The investigation based on the catalytic performance and characterizations of the catalysts suggests that the hydroxyl–metal interaction over the catalysts supported on different SiO2 results in different desorption behavior of the adsorbed CO. The specific interaction between the active components and weakly H-bonded hydroxyls on the SiO2 prepared by the Stöber method promoted the transformation from Rh+(CO)2 to Rh–CO and facilitated the desorption/reactivity of adsorbed CO as a function of temperature in the presence of hydrogen, which were proposed to be the crucial factors for obtaining higher CO conversion and C2+ oxygenates selectivity.Graphical abstractVarious hydroxyl groups exist on the silica supports prepared by the different methods, and have different interaction with metal particles, which finally affects the CO adsorption and results in different catalytic performance for CO hydrogenation.Highlights► Various hydroxyl groups exist on the SiO2 supports prepared by the different methods. ► The different hydroxyl–metal interactions affect the Rh–Mn interaction and CO adsorption. ► The weakly H-bonded hydroxyl is favorable for reactivity of the adsorbed CO. ► The increase of reactivity of the adsorbed CO results in high CO conversion.
Co-reporter:Kai Shen, Xiaohui Liu, Guanzhong Lu, Yongxia Miao, Yanglong Guo, Yanqin Wang, Yun Guo
Journal of Molecular Catalysis A: Chemical 2013 Volume 373() pp:78-84
Publication Date(Web):July 2013
DOI:10.1016/j.molcata.2013.02.020
High dispersed 10% MoO3/SiO2 catalysts were prepared by the sol–gel method using a precipitant (ammonium hydroxide) with different pH values, and investigated by XRD, FT-IR spectroscopy of pyridine adsorbed and Raman spectroscopy techniques, and so on. The results show that the catalytic performance of MoO3/SiO2 for the epoxidation of propylene with cumene hydroperoxide (CHP) is affected by pH value of precipitant, and MoO3/SiO2 prepared with precipitant of pH 9 exhibits the highest yield of propylene oxide (PO). It has been found that the weak Lewis acidic sites on MoO3/SiO2 are the active sites of the propylene epoxidation with CHP, total amount of Lewis acid sites on the catalyst surface is related with the CHP conversion, and the weaker Lewis acid sites is in favor of the propylene epoxidation. When the amount of Lewis acid sites on the catalyst surface is more and their acid strength is higher, the CHP degradation and PO acid-catalytic hydrolysis would be speeded up, resulting in a reduction of the PO selectivity. The concentration and strength of the Lewis acid sites on MoO3/SiO2 are affected by pH of precipitant, and the catalyst prepared with precipitant of pH 9.0 possesses the most weakly Lewis acidic sites and the highest selectivity to PO (91.5%). Besides, the addition of certain amount of Nd can increase the weakly acidic sites to enhance CHP conversion and reduce the Lewis acidity of the catalyst thus suppress PO hydrolysis.Graphical abstractHighlights► Precipitant pH value affect the strength of Lewis acid on MoO3/SiO2 (sol–gel method). ► Weak Lewis acid is the active site of MoO3/SiO2 catalysts for propylene epoxidation. ► Moderate addition of Nd in the MoO3/SiO2 can increase the amount of weak acid sites. ► Weak Lewis acid site is generated from the octahedral Mo specie.
Co-reporter:Shaodian Shen, Tao Gu, Dongsen Mao, Xiuzhen Xiao, Pei Yuan, Meihua Yu, Liyang Xia, Qiong Ji, Liang Meng, Wei Song, Chengzhong Yu, and Guanzhong Lu
Chemistry of Materials 2012 Volume 24(Issue 1) pp:230
Publication Date(Web):December 4, 2011
DOI:10.1021/cm203434k
Despite the extensive application of ellipsoidal micro-/nanoparticles, the synthesis of shape anisotropic ellipsoids is rare because of the minimization of surface free energy that favors simple spherical shape rather than complex nonspherical shape. We present the synthesis of silica ellipsoids with hexagonal mesostructure via the organic–inorganic cooperative assembly in the presence of cosolvents (KCl and ethanol). The aspect ratio of ellipsoids can be tuned systematically by controlling the concentration of ethanol. Transmission electron microscopy (TEM) shows that the ellipsoid possesses one-dimensional (1-D) pore channels parallel to the major axis, and the electron tomography (ET) technique shows that the ellipsoid has indeed hexagonal prism morphology in the middle and ellipsoidal morphology at two tips. A mechanism for the formation of mesoporous silica ellipsoids has been proposed. Importantly, magnetite/silica composite ellipsoids were prepared through a nanocasting route and can be used as building blocks to organize into ordered arrays in response to an external magnetic field. In addition, after functionalized with amino-groups, the amino-modified anisotropic magnetite/silica ellipsoids can be further used as carriers for delivering oligo-DNA-Cy3 into tumor cells, showing potential in directed self-assembly and drug/gene delivery.Keywords: anisotropic particles; cellular internalization; directed self-assembly; ellipsoids; mesoporous silica;
Co-reporter:Jie Li, Guanzhong Lu, Guisheng Wu, Dongsen Mao, Yanqin Wang and Yun Guo
Catalysis Science & Technology 2012 vol. 2(Issue 9) pp:1865-1871
Publication Date(Web):24 Apr 2012
DOI:10.1039/C2CY20118F
Ceria modified Co3O4 catalysts for low temperature CO oxidation were prepared by a precipitation–oxidation method, and characterized by low-temperature N2 adsorption/desorption, TPR, O2–TPD, CO–TPD and transient–response reaction. The roles of ceria in CeO2–Co3O4 catalyst and the effect of pretreatment on the performance of CeO2–Co3O4 for CO oxidation were investigated in detail. The results show that the presence of CeO2 can increase its surface area, reduce the crystal size of Co3O4, and improve obviously the catalytic activity and stability of Co3O4 for CO oxidation, such as its T100 is only −60 °C. It was also found that the addition of CeO2 can not only promote the adsorption of O2 and the reaction of adsorbed CO with surface oxygen species to form CO2, but also increase the CO2 desorption speed. The pretreatment method can affect the catalytic activity of CeO2–Co3O4, the catalyst treated in N2 exhibits higher catalytic activity for low-temperature CO oxidation due to formation of oxygen vacancy. The catalyst reduced in H2 shows lower activity for CO oxidation although it has more surface oxygen vacancies, because of the difficult desorption of CO2 on the reduced CeO2–Co3O4 catalyst.
Co-reporter:Fendy Chen, Di Liu, Jie Zhang, P. Hu, Xue-Qing Gong and Guanzhong Lu
Physical Chemistry Chemical Physics 2012 vol. 14(Issue 48) pp:16573-16580
Publication Date(Web):13 Jul 2012
DOI:10.1039/C2CP41281K
Density functional theory calculations corrected by on-site Coulomb interaction have been carried out to track down the lattice oxygen reactivity of CeO2(111) and (110) surfaces in direct oxidation of a single CO. The possible elementary steps in CO adsorption and subsequent reactions with lattice oxygen were systematically studied. From calculated energetics, we determined that the lattice oxygen of the (110) surface is more reactive than that of the (111) surface. By calculating the reaction pathways leading to different final products, we found that the formation of carbonate species is competitive to CO2 formation and desorption, and such an effect could be more significant at CeO2(110) compared to CeO2(111). More importantly, it has also been found that electron localization at the characteristic 4f orbital of Ce, directly determined by subtle structural relaxation, can give rise to a unique scenario of the overall reaction coordinates. These results may bring us one step ahead toward the comprehensive understanding of catalytic performance of CeO2-based materials.
Co-reporter:Yong Guo, Xiaohui Liu, Muhammad Usman Azmat, Wenjie Xu, Jiawen Ren, Yanqin Wang, Guanzhong Lu
International Journal of Hydrogen Energy 2012 Volume 37(Issue 1) pp:227-234
Publication Date(Web):January 2012
DOI:10.1016/j.ijhydene.2011.09.111
A Ni-B amorphous alloy catalyst (AP Ni) was prepared and used in an aqueous-phase reforming (APR) of glycerol. Higher stability and higher selectivity towards H2 were obtained when compared with Raney Ni. After 130 h’ on stream aqueous-phase reforming of glycerol, the amorphous Ni-B catalyst was transformed to hexagonal closed-packed (hcp) Ni crystallites. The high selectivity towards hydrogen and catalytic stability may be due to the formation of hcp Ni crystallites during reaction and the protection of B2O3. The AP Ni catalyst was found to be 35–50% more active in terms of the H2 production rate and 17–31% more selective toward H2 as compared to Raney Ni. The reforming reaction at different reaction temperature, feedstock concentration, feedstock flow rate and other biomass derivatives i.e., ethylene glycol and sorbitol, were also investigated over AP Ni catalyst.A Ni-B amorphous alloy catalyst (AP Ni) with higher stability and selectivity towards H2 was developed for an APR process of biomass derivatives.Highlights► A Ni-B amorphous alloy catalyst was used in aqueous-phase reforming of glycerol. ► High stability and high selectivity to H2 was obtained on Ni-B alloy catalyst. ► After long term APR of glycerol, Ni-B catalyst was transformed to hcp Ni. ► The good performance of Ni-B catalyst may be due to the formation of hcp Ni. ► The Ni-B catalyst can be used in the APR of ethylene glycol and sorbitol.
Co-reporter:Junming Yao, Wangcheng Zhan, Xiaohui Liu, Yanglong Guo, Yanqin Wang, Yun Guo, Guanzhong Lu
Microporous and Mesoporous Materials 2012 Volume 148(Issue 1) pp:131-136
Publication Date(Web):15 January 2012
DOI:10.1016/j.micromeso.2011.08.006
Ti-SBA-15C catalysts were prepared by supporting Ti on SBA-15 with chemical vapor deposition (CVD) using TiCl4 as titanium source, and were characterized by XRD, N2 adsorption, FT-IR and ICP. The results show that SBA-15E prepared by ethanol solution extracting template has higher concentration of surface Si–OH groups than SBA-15 calcined at 550 °C, resulting in high Ti content on Ti-SBA-15EC prepared by CVD. The temperature and time of TiCl4 deposition affect the Ti content and catalytic activity of Ti-SBA-15EC for the epoxidation of propylene with cumene hydroperoxide (CHP). Ti-SBA-15EC prepared by CVD at 700 °C for 1.5 h exhibits more excellent performance than Ti-SBA-15C, Ti-SBA-15 prepared hydrothermally and Ti/SBA-15 (impregnation method), and the 87.3% conversion of CHP and 96.4% selectivity to propylene oxide can be obtained at 80 °C for 4 h. The performance of Ti-SBA-15EC is decreased hardly for the epoxidation of propylene after used repeatedly 6 times.Graphical abstractTi-SBA-15 catalysts were prepared on SBA-15 by CVD using TiCl4 as titanium source. Using SBA-15 prepared by the ethanol solution extracting template as the support, Ti-SBA-15 with high Ti content can be prepared. Ti-SBA-15 prepared by CVD at 700 °C for 1.5 h exhibits more excellent performance and stability for the epoxidation of propylene with CHP than that prepared by other methods.Highlights► Ti-SBA-15 catalyst was prepared by supporting Ti on SBA-15 with CVD method. ► Template in as-prepared SBA-15 was removed by the ethanol solution extraction. ► Ti-SBA-15 catalyst has very excellent activity and stability for the epoxidation of C3H6.
Co-reporter:Pengfei Wang, Ailing Lv, Jie Hu, Jing’an Xu, Guanzhong Lu
Microporous and Mesoporous Materials 2012 Volume 152() pp:178-184
Publication Date(Web):1 April 2012
DOI:10.1016/j.micromeso.2011.11.037
In order to enhance the catalytic performance of SAPO-34 for the reaction of methanol to olefins (MTO), a mixture template of triethylamine (TEA) and tetraethyl ammonium hydroxide (TEAOH) was used to synthesize SAPO-34. The effects of the composition of the mixed template on the chemical composition, morphology and surface acidity of SAPO-34 were characterized by XRD, SEM, XRF, Si MAS NMR and NH3-TPD techniques. The catalytic performance of prepared SAPO-34 was investigated in a fixed-bed reactor at 450 °C for the MTO reaction. The results show that the chemical composition, morphology, crystal size and Si incorporation of SAPO-34 are affected greatly by the molar ratio of TEAOH/TEA. For the MTO reaction, all catalysts prepared show similar methanol conversion and product distribution, but their olefins selectivity and lifetime are greatly dependent on the ratio of TEAOH/TEA in the synthesis solution. Comparing with the SAPO-34 synthesized with single template, SAPO-34 synthesized with TEAOH/TEA = 0.1 possesses larger surface area, mild acidity and small crystal size and exhibits higher selectivity to light olefins (C2–C4), longer lifetime and lower carbon deposition rate.Graphical abstractThe SAPOs catalyst was synthesized with TEAOH/TEA = 0 (a), 0.05 (b), 0.1 (c), 0.2 (d), 0.4 (e), and 2 (f). Changing TEAOH/TEA can affect the chemical composition, morphology, crystal sizes and Si incorporation of SAPO-34. For the MTO reaction, SAPO-34 synthesized with TEAOH/TEA = 0.1 exhibits more excellent catalytic performance.Highlights► SAPO-34 was synthesized with a mixture template of TEA and TEAOH. ► TEAOH/TEA affects the physicochemical and catalytic performance of SAPOs sample. ► SAPO-34 prepared with TEAOH/TEA = 0.1 has very high catalytic performance for MTO.
Co-reporter:Anmiao Wang, Jiawen Ren, Bianfang Shi, Guanzhong Lu, Yanqin Wang
Microporous and Mesoporous Materials 2012 Volume 151() pp:287-292
Publication Date(Web):15 March 2012
DOI:10.1016/j.micromeso.2011.10.022
Mesoporous carbon materials with partially graphitized structure were synthesized by a one-pot, co-assembly of tri-block copolymer with phenolic resin under the assistance of ammonium ferric citrate. The structure was characterized by XRD, TEM, N2 sorption and TG/DTA. The mesoporous structure of the polymer conserved after the addition of ammonium ferric citrate. The graphitization of carbon material was achieved at lower temperature (700 °C), which was attributed to the catalytic property of iron, as well as the formation of carbon-polymer structure pre-carbonized at 350 °C. The final graphitic porous carbon materials had high surface area and performed well in the selective oxidation of benzyl alcohol to benzaldehyde. The selectivity to benzaldehyde reached 96.2%.Graphical abstractHighlights► Partially graphitized mesoporous carbon was obtained by one-pot synthesis. ► The carbonization temperature was as lower as 700 °C. ► The low temperature carbonization is attributed to the catalytic property of iron. ► The graphitic porous carbon has excellent activity in oxidation of benzyl alcohol.
Co-reporter:Qiuling Luo, Shaodian Shen, Guanzhong Lu, Xiuzhen Xiao, Dongsen Mao and Yanqin Wang
RSC Advances 2012 vol. 2(Issue 2) pp:616-621
Publication Date(Web):15 Nov 2011
DOI:10.1039/C1RA00653C
Cubic and hexagonal ordered mesoporous Eu3+-doped yttrium vanadate (YVO4:Eu3+) have been synthesized successfully through the nanocasting route with a Y(NO3)3/Eu(NO3)3/NH4VO3/HNO3/ethanol system as a guest unit and KIT-6 or SBA-15 silica as the hard template host, and were characterized by X-ray diffraction (XRD), transmission electronic microscopy (TEM) and low-temperature nitrogen adsorption. The prepared YVO4:Eu3+ samples have the characteristic cubic (Ia3d) (or hexagonal (p6mm)) ordered mesostructure based on different hard templates, and possess high surface area, large pore volume and uniform pore size distribution. Photoluminescence (PL) measurement shows that the main red emission peaks of two mesoporous YVO4:Eu3+ samples appear at 618 nm, and different mesostructures lead to different optimum concentrations of Eu3+ dopant and different PL intensities. For the hexagonal mesoporous YVO4:Eu3+, when Eu3+ dopant is 5(mol)% the highest PL intensity can be reached; for the cubic one, optimized Eu3+ amount is 8 mol%. The interaction between Eu3+ ions in hexagonal (p6mm) mesoporous YVO4:Eu3+ is more active than that in cubic (Ia3d) mesoporous YVO4:Eu3+, thus the absorbed energy is dissipated by nonradiation; while the cubic mesoporous YVO4:Eu3+ has more Eu3+ luminescent sites, compared with the hexagonal mesostructure one.
Co-reporter:Hai-Feng Wang;Richard Kavanagh; Yang-Long Guo; Yun Guo; Guan-Zhong Lu; P. Hu
Angewandte Chemie International Edition 2012 Volume 51( Issue 27) pp:6657-6661
Publication Date(Web):
DOI:10.1002/anie.201108981
Co-reporter:Hai-Feng Wang;Richard Kavanagh; Yang-Long Guo; Yun Guo; Guan-Zhong Lu; P. Hu
Angewandte Chemie 2012 Volume 124( Issue 27) pp:6761-6765
Publication Date(Web):
DOI:10.1002/ange.201108981
Co-reporter:Xiang Zheng, Qing Zhang, Yanglong Guo, Wangcheng Zhan, Yun Guo, Yunsong Wang, Guanzhong Lu
Journal of Molecular Catalysis A: Chemical 2012 Volume 357() pp:106-111
Publication Date(Web):May 2012
DOI:10.1016/j.molcata.2012.01.027
Supported Ag-based bimetallic catalysts with low Ag loading of 3.0 wt%, prepared by the surfactant-protected colloidal method, were investigated for the epoxidation of propylene by molecular oxygen and characterized by UV–vis, XRD, TEM, XPS, and H2-TPR. Ag–Cu/BaCO3 bimetallic catalyst exhibits better catalytic performance, governed by the molar ratio of Ag/Cu, than other supported Ag-based bimetallic catalysts and monometallic catalysts for the epoxidation of propylene by molecular oxygen. The highest propylene oxide selectivity of 55.1% and the propylene conversion of 3.6% were achieved over Ag95–Cu5/BaCO3 bimetallic catalyst. XRD and TEM results show that a small quantity of Cu can effectively regulate the size of Ag crystallites to restrain their agglomeration. XPS results indicate that the presence of Cu can withdraw electrons from nearby Ag and thus make Ag electropositive, which is beneficial to produce more active sites where electrophilic oxygen species can be absorbed to increase the propylene oxide selectivity. H2-TPR results show that the reactivity and the amount of the oxygen species adsorbed on Ag surface can be regulated by the synergistic effect between Ag and Cu, which plays an important role in increasing the propylene oxide selectivity and the propylene conversion.Graphical abstractOver Ag95–Cu5/BaCO3 bimetallic catalyst with Ag loading of 3.0 wt%, the synergistic effect between Ag and Cu is beneficial to produce more active sites where electrophilic oxygen species can be absorbed and inhibit the reactivity of the oxygen species adsorbed on Ag surface, in which the propylene oxide selectivity of 55.1% and the propylene conversion of 3.6% were achieved.Highlights► Ag–Cu/BaCO3 bimetallic catalyst exhibits better catalytic performance. ► Cu can regulate the size of Ag crystallites to restrain their agglomeration. ► Cu can withdraw electrons from nearby Ag and make Ag electropositive. ► Synergistic effect between Ag and Cu is favorable to increase catalytic performance.
Co-reporter:Qiuling Luo, Guanzhong Lu, Shaodian Shen, Xiuzhen Xiao, Dongsen Mao and Yanqin Wan
Journal of Materials Chemistry A 2011 vol. 21(Issue 43) pp:17104-17110
Publication Date(Web):07 Sep 2011
DOI:10.1039/C1JM12601F
With hydrophobic properties and ordered layered structures, mono-n-dodecyloxy-phosphinyl-cerium (terbium) (MDPCT) organic–inorganic hybrid materials were synthesized using cerium nitrate, terbium nitrate and mono-n-dodecyl phosphate (MDP) surfactant with three functions, hydrophobic group and phosphorus precursor, and characterized by XRD, SEM, TEM, FTIR and PLS. The results show that the solvent affects the interlayer spacing, crystallization and luminescent intensity of the prepared MDPCT materials. MDPCT prepared in water exhibits a more ordered layered structure and a higher degree of crystallinity, as well as stronger luminescent intensity than that prepared in ethanol. Based on the excellent solubility in organic solvents, this MDPCT hybrid luminescent material will be a promising candidate for potential biomedical applications in fluorescent imaging and analysis.
Co-reporter:Wenjie Xu, Haifeng Wang, Xiaohui Liu, Jiawen Ren, Yanqin Wang and Guanzhong Lu
Chemical Communications 2011 vol. 47(Issue 13) pp:3924-3926
Publication Date(Web):23 Feb 2011
DOI:10.1039/C0CC05775D
A new strategy was developed for the direct conversion of furfural to 1,5-pentanediol by the hydrogenolysis of the furan ring under mild conditions based on Pt/Co2AlO4 catalyst. This is the first report of the direct catalytic conversion of furfural to 1,5-pentanediol with high yield.
Co-reporter:Hui-Ying Li, Hai-Feng Wang, Yang-Long Guo, Guan-Zhong Lu and P. Hu
Chemical Communications 2011 vol. 47(Issue 21) pp:6105-6107
Publication Date(Web):26 Apr 2011
DOI:10.1039/C1CC11226K
Using first principles calculations for O vacancy diffusion on CeO2(111), we locate a surface diffusion mechanism, the two-step O vacancy exchange one, which is more favored than the most common hopping mechanism. By analyzing the results, we identify quantitatively the physical origin of why the two-step exchange mechanism is preferred.
Co-reporter:Zhicong Liu, Guanzhong Lu, Yun Guo, Yanqin Wang and Yanglong Guo
Catalysis Science & Technology 2011 vol. 1(Issue 6) pp:1006-1012
Publication Date(Web):23 Jun 2011
DOI:10.1039/C1CY00140J
The effective utilization of coal bed methane (CBM) is very significant for energy utilization and environmental protection, reducing significantly greenhouse gas methane emission. In this paper, La1−xErxCoO3 perovskite (0 ≤ x ≤ 0.4) catalysts for the catalytic deoxidization of CBM were prepared by a co-precipitation method and were characterized by X-ray diffraction (XRD), laser Raman spectroscopy (LRS), H2 and CH4 temperature-programmed reduction (H2, CH4-TPR), CO pulse and N2adsorption/desorption techniques. The results show that the amount of Er affects obviously the physicochemical and catalytic properties of La1−xErxCoO3, and when x = 0.2, La0.8Er0.2CoO3 exhibits the best activity for deoxidization of CBM, because Er doping promotes the activity and migration of the lattice oxygen of La0.8Er0.2CoO3. The influences of the operation parameters (methane concentration, oxygen concentration and space velocity) on the catalytic deoxygenation of CBM and the kinetics behaviours were investigated. The reaction order of removing oxygen is 0.9 for methane partial pressure and −0.6 for oxygen partial pressure.
Co-reporter:Shimei Ma, Guanzhong Lu, Yuexin Shen, Yun Guo, Yanqin Wang and Yanglong Guo
Catalysis Science & Technology 2011 vol. 1(Issue 4) pp:669-674
Publication Date(Web):23 May 2011
DOI:10.1039/C1CY00049G
Cu1Ce8Fex–O catalysts for low temperature CO oxidation were prepared by an improved citrate sol–gel method with incorporation of thermal treatment under N2, and characterized by the nitrogen adsorption–desorption, XRD, CO pulse experiments, CO-TPR and CO-TPD. When x = 1, the Cu1Ce8Fe1–O catalyst shows higher catalytic activity for CO oxidation, and the reaction temperature for 90% CO conversion (T90) is only 50 °C. The presence of Fe in Cu1Ce8Fe1–O can improve the catalytic activity for CO oxidation, which results from its higher surface area, smaller crystalline size, higher activity and larger amounts of surface oxygen species.
Co-reporter:Yuexin Shen, Yun Guo, Li Wang, Yanqin Wang, Yanglong Guo, Xueqing Gong and Guanzhong Lu
Catalysis Science & Technology 2011 vol. 1(Issue 7) pp:1202-1207
Publication Date(Web):16 Aug 2011
DOI:10.1039/C1CY00146A
The catalytic stability of a Pd–Cu–Clx/Al2O3 catalyst for low temperature CO oxidation was investigated in different conditions. Under ∼0.1% moisture, the CO conversion over the Pd–Cu–Clx/Al2O3 catalyst can be maintained at 100% for 30 h even at 0 °C, but it deactivated reversibly at 25 °C with ∼0.6% moisture and irreversibly deactivated at 25 °C with ∼3.1% moisture or 0 °C with ∼0.6% moisture. The reversible deactivation is resulted from physical capillary condensation in the small pores of the catalysts. The irreversible deactivation is due to a breakage of the close-knit structure of Pd–Cu–Cl leading to an aggregation or transformation of the active copper phase, and the formation of a carbonate species on the catalyst surface, meaning that the inactive Pd0 species over the surface of the Pd–Cu–Clx/Al2O3 catalyst is hard to re-oxidize back to the active Pd+ sites by copper species in the high moisture reaction conditions.
Co-reporter:Tianlong Jiang, Haixiang Tao, Jiawen Ren, Xiaohui Liu, Yanqin Wang, Guanzhong Lu
Microporous and Mesoporous Materials 2011 Volume 142(Issue 1) pp:341-346
Publication Date(Web):June 2011
DOI:10.1016/j.micromeso.2010.12.020
In this paper, extremely hydrothermal stable mesoporous Al-SBA-15 with controllable Al content has been synthesized by using triblock copolymer (P123) as template under an assistance of NaF at 160 °C. This kind of material was characterized by powder X-ray diffraction (XRD), N2 sorption isotherms, transmission electron microscopy (TEM), 27Al MAS NMR, energy-dispersive X-ray spectroscopy (EDX), and ammonia-temperature programmed desorption (NH3-TPD). It was found that nearly all Al added into the initial reaction mixture can be introduced into the product and thus-synthesized Al-SBA-15 maintained the well-ordered mesostructure and high surface area, large pore size, thick pore wall and high pore volume even after being hydrothermally treated at 100 °C for 300 h or steamed at 600 °C for 6 h. This kind of Al-SBA-15 is an efficient catalyst for the protection of carbonyl compound reactions under mild conditions.Research highlights► Extremely hydrothermal stable mesoporous Al-SBA-15 was synthesized. ► NaF was used as an assistant, which improved the hydrothermal stability. ► The reduction of BET surface area was very low after hydrothermally treatment. ► This kind of Al-SBA-15 was an efficient catalyst and had good reusability.
Co-reporter:Wenjie Xu, Xiaohui Liu, Jiawen Ren, Huihui Liu, Yichun Ma, Yanqin Wang, Guanzhong Lu
Microporous and Mesoporous Materials 2011 Volume 142(Issue 1) pp:251-257
Publication Date(Web):June 2011
DOI:10.1016/j.micromeso.2010.12.008
A novel mesoporous Co–Al spinel catalyst with high surface area and suitable basicity was prepared by the thermal decomposition of Co–Al hydrotalcite-like compound. The properties of the solid base catalyst were characterized by XRD, FTIR, TEM, nitrogen sorption and CO2-TPD. The formation mechanism of the mesopores and the Co–Al spinel structure was also investigated by TG/DTA and mass-spectrometer, respectively. This is due to the partial oxidation of Co2+ ions and the dehydration of the interface OH groups in precursor. The formed Co3+ ions collapsed into the interlayer space, coordinated with the adjacent oxygen atoms (tetrahedral or octahedral), worked as pillars between layers and made the interlayer space to be almost opened (mesopores formed). The partial oxidation of Co2+ ions plays a critical role in the phase transformation and the formation of mesopores. The as-obtained mesoporous Co–Al spinel-type solid base catalyst was first used in the aldol condensation of furfural with acetone and the self-condensation of acetone and found that it had good activity and excellent selectivity in both reactions. The stability studies showed that the catalyst can be completely regenerated easily by calcination.Graphical abstractA novel mesoporous Co–Al spinel type solid base catalyst with high surface area was prepared, which was used for the aldol condensation of furfural with acetone and the self-condensation of acetone with high activity and easy regeneration.Research highlights► A novel mesoporous Co–Al spinel-type solid base catalyst was prepared. ► The partial oxidation of Co2+ and dehydration of interface OH play the role. ► This kind of solid base catalyst was used in Aldol condensation with good activity. ► The catalytic activity can be completely regenerated easily by calcination.
Co-reporter:Pengfei Wang, Ailing Lv, Jie Hu, Jing’an Xu, and Guanzhong Lu
Industrial & Engineering Chemistry Research 2011 Volume 50(Issue 17) pp:9989-9997
Publication Date(Web):July 29, 2011
DOI:10.1021/ie201060u
Rapid deactivation and short lifetime are challenges for SAPO-34 catalysts for the reaction of methanol to olefins (MTO). To overcome these drawbacks, SAPO-34 on fully calcined kaolin microspheres (CKMs) was synthesized in situ by a hydrothermal method with tetraethylammonium hydroxide (TEAOH) and triethylamine (TEA) as templates. To facilitate the growth of SAPO-34, the CKMs were first pretreated by 2–14 wt % NaOH aqueous solution, and the effects of the NaOH concentration on the physicochemical properties of CKMs and the SAPO-34/kaolin microspheres (SCKMs) were characterized by means of XRD, XPS, SEM, low-temperature N2 adsorption, and NH3-TPD. The results showed that NaOH pretreatment has obvious effects on the chemical compositions and morphologies of the CKMs and, thus, the physicochemical properties of the SAPO-34 grown on them. Moreover, the textural and catalytic properties of the SCKMs were found to depend strongly on the concentration of NaOH solution, and the optimal NaOH concentration was determined to be 4 wt %. For the MTO reaction catalyzed by the prepared SCKM catalyst, 100% methanol conversion, 89.8% light olefins selectivity, and a 964-min lifetime (the reaction time during which the yield of C2–C4 olefins exceeded 70%) were obtained at 450 °C, which are much better than the values for free SAPO-34 and SAPO-34 supported on metakaolin microspheres.
Co-reporter:Wei-Kun Li, Li-Na Chu, Xue-Qing Gong, Guanzhong Lu
Surface Science 2011 Volume 605(15–16) pp:1369-1380
Publication Date(Web):August 2011
DOI:10.1016/j.susc.2011.04.032
We have compared the adsorption properties of small Aun (n = 1–8) nanoparticles on the defect-free (stoichiometric) and defective (partially reduced) brookite TiO2(210) and anatase TiO2(101) surfaces using density functional theory calculations. The interaction between Au atoms and anatase TiO2(101) was determined to be quite weak and small Aun particles grown at defects (O vacancies) prefer extended 2D structures. By contrast, dispersion and 3D configurations appear to be favored at brookite TiO2(210) for Aun nanoparticles due to their strong interaction. Calculations of CO oxidation at Aun (n = 6–8) particles supported at defective brookite TiO2(210) show that occurrence of protruding low-coordinated Au atoms is essential for favorable CO adsorption and subsequent reaction with O2. In particular, the configuration of the Aun nanoparticles can determine the energetics in the formation of active Au atoms, and their mobility also affects the reaction between CO and O2 (or O).Research Highlights► We calculate Au nanoparticles at two TiO2 surfaces. ► We compare the structures and catalytic activities of Au nanoparticles. ► Au nanoparticles like to grow at O vacancies of brookite (210) and anatase (101). ► 3D Au nanoparticles like to form at brookite (210). ► 3D Au nanoparticles are highly active for CO and O2 adsorption and reaction.
Co-reporter:Baogeng Xie, Guanzhong Lu, Yanqin Wang, Yun Guo, Yanglong Guo
Materials Letters 2011 Volume 65(Issue 2) pp:240-243
Publication Date(Web):31 January 2011
DOI:10.1016/j.matlet.2010.09.079
Tetragonal phase LaVO4 (t-LaVO4) was successfully selectively synthesized through a simple solution method with La(NO3)3 and NaVO4 as starting materials without any templates or catalysts. The products were characterized by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). XRD patterns showed that pure t-LaVO4 could be obtained in wide ranges of pH value and crystallization temperature. TEM images revealed that nanorods with different aspect ratios were obtained in different synthesis conditions. The shorter nanorods had mean diameters of about 18–25 nm and lengths of 40–60 nm. However, the longer nanorods had uniform sizes with an average aspect ratio about 10. It was interesting to discover that t-LaVO4 could be formed even at room temperature (RT), which might be beneficial for a large scale production. Different luminescence performances of the samples doped 5% Eu3+ were also investigated.
Co-reporter:Haixiang Tao, Changlin Li, Jiawen Ren, Yanqin Wang, Guanzhong Lu
Journal of Solid State Chemistry 2011 Volume 184(Issue 7) pp:1820-1827
Publication Date(Web):July 2011
DOI:10.1016/j.jssc.2011.05.023
Mesoporous zeolite (silicalite-1, ZSM-5, TS-1) single crystals have been successfully synthesized by adding soluble starch or sodium carboxymethyl cellulose (CMC) to a conventional zeolite synthesis system. The obtained samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen sorption analysis, 27Al magic angle spinning nuclear magnetic resonance (27Al MAS NMR), temperature-programmed desorption of ammonia (NH3-TPD) and ultraviolet–visible spectroscopy (UV–vis). The SEM images clearly show that all zeolite crystals possess the similar morphology with particle size of about 300 nm, the TEM images reveal that irregular intracrystal pores are randomly distributed in the whole crystal. 27Al MAS NMR spectra indicate that nearly all of the Al atoms are in tetrahedral co-ordination in ZSM-5, UV–vis spectra confirm that nearly all of titanium atoms are incorporated into the framework of TS-1. The catalytic activity of meso-ZSM-5 in acetalization of cyclohexanone and meso-TS-1 in hydroxylation of phenol was also studied. The synthesis method reported in this paper is cost-effective and environmental friendly, can be easily expended to prepare other hierarchical structured zeolites.Graphical abstractMesoporous zeolite single crystals were synthesized by using cheap porogens as template.Highlights► Mesoporous zeolite (silicalite-1, ZSM-5, TS-1) single crystals were synthesized. ► Soluble starch or sodium carboxymethyl cellulose (CMC) was used as porogens. ► The mesoporous zeolites had connected mesopores although closed pores existed. ► Higher catalytic activities were obtained.
Co-reporter:Xiuzhen Xiao, Guanzhong Lu, Shaodian Shen, Dongsen Mao, Yun Guo, Yanqin Wang
Materials Science and Engineering: B 2011 Volume 176(Issue 1) pp:72-78
Publication Date(Web):15 January 2011
DOI:10.1016/j.mseb.2010.09.005
The mixed solvent-thermal method has been developed for the synthesis of YVO4:Eu3+ luminescent materials in the N, N-dimethylformamide (DMF)/ de-ionized water (DIW) solution. The samples have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electronic microscope (TEM), UV/vis absorption and photoluminescence spectroscopies. The results demonstrate that we have obtained the uniform YVO4:Eu3+ cobblestone - like microcrystalline phosphors in the mixed solution of DMF and DIW, which are different to the as-obtained YVO4:Eu3+ nanoparticles in pure DIW. And the as - prepared YVO4:Eu3+ microcrystalline particles are composed of numerous nanoparticles. The assembling phenomenon of the nanoparticles is strongly affected by the pH value of the solution and the volume ratio of DMF/DIW. Under UV excitation, the samples can emit the bright red light. While, the photoluminescence (PL) intensities of YVO4:Eu3+ show some difference for samples obtained under the different reaction conditions. This is because that different microstructures of samples result in different combinative abilities between the surface and the adsorbed species so as to produce the different quenching abilities to the emission from Eu3+ ions.
Co-reporter:Muhammad Usman Azmat, Yong Guo, Yun Guo, Yanqin Wang, Guanzhong Lu
Journal of Molecular Catalysis A: Chemical 2011 Volume 336(1–2) pp:42-50
Publication Date(Web):14 February 2011
DOI:10.1016/j.molcata.2010.12.008
A single unit catalyst system (Pt/silica–chiral modifier) is developed for the enantioselective hydrogenation of ethyl pyruvate. Cinchonidine was tethered directly without prior modification over carboxylate functionalized SBA-15 by the reaction of vinyl group in cinchonidine with –COOH group in functionalized SBA-15 through ester linkage. Then Pt nanoparticles were deposited over cinchonidine tethered SBA-15. The mesostructures were characterized by small-angle XRD, N2 sorption and TEM, while the surface functionalization was confirmed by FTIR, TG/DTA and solid state 13C NMR. Enantioselectivity of the catalyst system for hydrogenation of ethyl pyruvate was determined by GC/FID. The highest enantiomeric excess was achieved as 70.8% and the catalyst recyclability was authenticated even after 3rd reuse without significant loss in enantiomeric excess.Graphical abstractA single unit heterogeneous Chiral catalyst system (Pt/CA-SBA-CD) is prepared for the enantioselective hydrogenation of ethyl pyruvate. Cinchonidine is tethered successfully with carboxylate functionalized SBA-15 which is further impregnated by Pt nanoparticles. The highest enantiomeric excess was achieved as 70.8% with adequate recyclability.Research highlights▶ A unique heterogeneous chiral catalyst is developed for hydrogenation. ▶ Cinchonidine is directly tethered with CA-SBA-15. ▶ Pt nanoparticles deposit in the channels of cinchonidine-tethered CA-SBA-15. ▶ Catalyst system provides a maximum of 70.8% e.e. value with adequate recyclability.
Co-reporter:Xiaoming Guo, Dongsen Mao, Guanzhong Lu, Song Wang, Guisheng Wu
Journal of Molecular Catalysis A: Chemical 2011 Volume 345(1–2) pp:60-68
Publication Date(Web):5 July 2011
DOI:10.1016/j.molcata.2011.05.019
A series of Cu/ZrO2 catalysts with various La loadings for methanol synthesis from CO2 hydrogenation were prepared by a urea–nitrate combustion method. The catalysts were characterized with N2 adsorption, XRD, reactive N2O adsorption, XPS, TPR, H2-TPD and CO2-TPD techniques, and tested for methanol synthesis from CO2 hydrogenation. With increasing La loading, the Cu surface area increases first and then decreases, whereas the amount of basic site over catalysts increases continuously. The results of catalytic test reveal that a linear relationship exists between the conversion of CO2 and the Cu surface area. Moreover, it is found for the first time that the selectivity to methanol is related to the distribution of basic site on the catalyst surface. The presence of La favors the production of methanol, and the optimum catalytic activity is obtained when the amount of La doping is 5% of the total amount of Cu2+ and Zr4+.Graphical abstractWith increasing La loading, the CO2 conversion takes on a volcano variation trend, whereas the methanol selectivity increases continuously.Highlights► The presence of La favors the production of methanol. ► The introduction of La affects the Cu surface area of catalyst. ► The introduction of La affects the basicity of catalyst. ► A linear relationship exists between CO2 conversion and the Cu surface area. ► The methanol selectivity is related to the distribution of basic sites of catalyst.
Co-reporter:Yang Yu, Yanglong Guo, Wangcheng Zhan, Yun Guo, Yanqin Wang, Yunsong Wang, Zhigang Zhang, Guanzhong Lu
Journal of Molecular Catalysis A: Chemical 2011 Volume 337(1–2) pp:77-81
Publication Date(Web):1 March 2011
DOI:10.1016/j.molcata.2011.01.019
Cu–CeO2–Al2O3 catalyst, prepared by co-precipitation method, was investigated for the gas-phase hydrogenation of maleic anhydride (MA) to γ-butyrolactone (GBL) at atmospheric pressure and the catalyst deactivation was also studied. Effects of catalyst composition, reaction temperature, and liquid hourly space velocity (LHSV) of raw material on the catalytic performance of Cu–CeO2–Al2O3 catalyst were investigated. The catalyst (molar ratio of Cu:Ce:Al = 1:1:2) showed better catalytic performance, in which both the conversion of MA and the selectivity of GBL kept 100% within two hours under the reaction conditions of 6 mL catalyst, 0.1 MPa, 220–280 °C, 30 mL min−1 H2, 0.6 h−1 LHSV of 20 wt.% MA/GBL. As for Cu–CeO2–Al2O3 catalyst, smaller crystallite size of Cu and higher Cu surface area are favorable to increase its catalytic performance. The deactivation of Cu–CeO2–Al2O3 catalyst is due to formation of the compact wax-like deposition on the catalyst surface, which is probably ascribed to the strong adsorption of succinic anhydride and then polymerization on the catalyst surface. The catalytic performance of the regenerated catalyst can be recovered completely by the regeneration method of N2–air–H2 stage treatment.Graphical abstractResearch highlights► Cu–CeO2–Al2O3 catalyst was prepared by co-precipitation method. ► The catalyst showed better catalytic performance. ► Small crystallite size of Cu and high Cu surface area of the catalyst are favorable. ► The catalyst deactivation is due to the compact wax-like surface deposition. ► The catalytic performance of the regenerated catalyst can be recovered completely.
Co-reporter:Wei Yao, Xiang Zheng, Yanglong Guo, Wangcheng Zhan, Yun Guo, Guanzhong Lu
Journal of Molecular Catalysis A: Chemical 2011 Volumes 342–343() pp:30-34
Publication Date(Web):1 June 2011
DOI:10.1016/j.molcata.2011.04.006
Effects of concentration of chlorohydrocarbon and reaction time on the catalytic performance of 20% Ag–0.1% Y2O3–0.1% K2O/α-Al2O3 catalyst for the epoxidation of propylene by molecular oxygen were investigated, in which the role of chlorohydrocarbon in increasing selectivity of propylene oxide (PO) was characterized by XRD, SEM-EDS and XPS. With an increase in the concentration of chlorohydrocarbon in the feed gas, PO selectivity increased significantly and propylene conversion decreased remarkably and then the catalytic performance remained nearly constant when the concentration of chlorohydrocarbon was more than 125 ppm. PO selectivity increased from 46.8% to 75.6% and propylene conversion declined from 4.0% to 0.77% after 10 h induction period, and then the catalytic performance remained nearly constant for 140 h, under the reaction conditions of 245 °C, 0.1 MPa, GHSV of 2000 h−1, and 125 ppm 1,1,1-trichloroethane (TCE). A small amount of TCE could effectively control the surface morphology of the catalyst and restrain the agglomeration of Ag crystallites, in which TCE was dissociated on the surface of Ag crystallites to form AgCl and the coexistence of Ag and AgCl was favorable to increase PO selectivity. The presence of Cl could withdraw electrons from nearby Ag and thus make Ag electropositive, which was beneficial to produce more active sites where electrophilic oxygen species could be absorbed to increase PO selectivity. Y2O3 played a role of electron-type promoter that could strongly polarize electron cloud of nearby Ag, which made the absorbed oxygen species hold proper electrophilic character and then attack CC bond of propylene to produce PO.Graphical abstractHighlights► Concentration of chlorohydrocarbon had positive effect on PO selectivity. ► Ag-based catalyst showed better PO selectivity and stability with TCE in feed gas. ► TCE could effectively restrain the agglomeration of Ag crystallites. ► Coexistence of Ag and AgCl was favorable to increase PO selectivity. ► Presence of Cl could withdraw electrons from nearby Ag and thus make Ag electropositive.
Co-reporter:Baogeng Xie;Guanzhong Lu;Qiguang Dai;Yanqin Wang;Yun Guo
Journal of Cluster Science 2011 Volume 22( Issue 4) pp:555-561
Publication Date(Web):2011 December
DOI:10.1007/s10876-011-0396-0
Tetragonal CeVO4 was prepared through hydrothermal treatment and sonication method with the same precursor in the absence of any catalysts or templates, and the products were characterized by XRD, TEM and Raman. It is found that microrods, nanoparticles, nanorods and nanoplates have been obtained. The bigger nanorods produced through hydrothermal treatment have average diameters of 15–25 nm and lengths of 20–60 nm. The smaller nanorods prepared through ultrasound treatment have average diameters of 6–12 nm and lengths of 10–18 nm. Uniform nanoplates have been produced. The nanoplates produced through hydrothermal method are composed of CeVO4 and CeO2. The mechanism of shape changing has been discussed. And the existing vanadium which is sensitive to the pH value of synthesis solution may be a key factor for the resulted sizes and shapes of the obtained nanocrystals. The samples prepared through hydrothermal treatment and sonication method were used as the catalysts for the combustion of trichloroethylene to test their catalytic activity.
Co-reporter:Dongsheng Qiao;Guanzhong Lu;Dongsen Mao;Yun Guo
Journal of Materials Science 2011 Volume 46( Issue 3) pp:641-647
Publication Date(Web):2011 February
DOI:10.1007/s10853-010-4786-8
Methane catalytic combustion was carried out over the Ce0.9–xNi0.1CaxOδ (0 < x ≤ 0.3) catalysts prepared by a citric acid complexation–combustion method. When x ≤ 0.1, the presence of Ca can enhance the surface area and reduce the crystalline size, and improve the reduction of the dispersed NiO species in catalyst, resulting in an improvement of the catalytic activity of Ce0.9–xNi0.1CaxOδ. The XRD and Raman results show that Ce0.9–xNi0.1CaxOδ (x ≤ 0.1) solid solution can form by Ni and Ca incorporation in the CeO2 lattices. TEM and etching results reveal that part of Ni disperses well on the surface of Ca-doped sample. FT-IR testing shows that with an increase in Ca amount (x > 0.1), more carbonate species (mainly carbonate calcium) can form on the catalyst surface, which would severely debase the catalytic activity of Ce0.9–xNi0.1CaxOδ.
Co-reporter:Xiaohong Wang;Guanzhong Lu;Yun Guo;Zhigang Zhang
Environmental Chemistry Letters 2011 Volume 9( Issue 2) pp:185-189
Publication Date(Web):2011 June
DOI:10.1007/s10311-009-0261-7
The Au/Al2O3 and Au–Rh/Al2O3 catalysts were prepared by deposition–precipitation. The promotional effect of Rh on the performance of the Au/Al2O3 catalyst for CO oxidation was studied. The results indicate that using Au/Al2O3 catalyst, CO can be completely oxidized at 0°C or much lower temperature but the catalyst deactivated very fast. Rh can improve the stability of Au/Al2O3 catalyst more than 10 times, which gives an important hint to develop high stable catalyst for CO oxidation at low temperature.
Co-reporter:Hongfeng Li;Guanzhong Lu;Dongsheng Qiao;Yanqin Wang;Yun Guo
Catalysis Letters 2011 Volume 141( Issue 3) pp:452-458
Publication Date(Web):2011 March
DOI:10.1007/s10562-010-0513-y
Co–Ce–O composite oxides with high surface areas were firstly prepared by a modified citrate sol–gel method with N2 thermal treatment prior to calcination in air. The prepared Co–Ce–O catalysts have higher Brunauer–Emmett–Teller surface areas than those prepared by conventional calcination in air, and thus exhibit more effective catalytic activities. Adding CeO2 into Co3O4 can not only increase the activity of Co3O4 but also greatly enhance its thermal stability. When the bulk atomic ratio of Co/Ce is 3/1, Co–Ce–O composite oxide possesses the best activity and stability for the methane combustion.
Co-reporter:Yuexin Shen, Guanzhong Lu, Yun Guo and Yanqin Wang
Chemical Communications 2010 vol. 46(Issue 44) pp:8433-8435
Publication Date(Web):11 Oct 2010
DOI:10.1039/C0CC02776F
Pd–Cu–Clx/Al2O3 catalysts were prepared by a NH3 coordination-impregnation method and exhibited an excellent activity for low-temperature CO oxidation and 100% CO conversion was obtained at −30 °C for 400 ppm CO and 1000 ppm H2O/air.
Co-reporter:Hongfeng Li, Guanzhong Lu, Qiguang Dai, Yanqin Wang, Yun Guo and Yanglong Guo
ACS Applied Materials & Interfaces 2010 Volume 2(Issue 3) pp:838
Publication Date(Web):March 5, 2010
DOI:10.1021/am900829y
Mesoporous Ce(OH)CO3 microspheres with flowerlike three-dimensional (3D) hierarchical structure were successfully synthesized via different hydrothermal systems, including glucose/acrylic acid, fructose/acrylic acid, glucose/propanoic acid, and glucose/n-butylamine systems. After Ce(OH)CO3 microspheres were calcined, mesoporous CeO2 microspheres with the same flowerlike morphology as Ce(OH)CO3 microspheres were obtained. Especially, flowerlike CeO2 microspheres prepared via the glucose/acrylic acid system are composed of many interconnected mesoporous petal-like nanosheets with thicknesses of 40−60 nm and have high surface area (211 m2 g−1), large pore volume (0.32 cm3 g−1), and narrow pore size distribution (∼3.8 nm in diameter). A possible formation mechanism of Ce(OH)CO3 microspheres is proposed: the large N-containing organic compounds in situ produced in the above reaction systems played a crucial role in controlling the assembly of Ce(OH)CO3 building blocks into the flowerlike Ce(OH)CO3 microspheres. For trichloroethylene combustion, flowerlike CeO2 microspheres were found to exhibit much higher catalytic activity than general CeO2 prepared with the conventional methods and the T10% and T90% were as low as 100 and 204 °C, respectively.Keywords: catalytic activity; flowerlike morphology; high surface area; mesoporous CeO2 microsphere; trichloroethylene combustion
Co-reporter:Cun Wen, Yi Liu, Yun Guo, Yanqin Wang and Guanzhong Lu
Chemical Communications 2010 vol. 46(Issue 6) pp:880-882
Publication Date(Web):05 Jan 2010
DOI:10.1039/B920725B
Hydrogen can be produced over Er2O3 in methane oxidation (oxygen/methane = 26). The reactivity of lattice oxygen in the catalyst plays a main role in the conversion of surface hydroxyl species to hydrogen or water. Adding a rare earth element into a catalyst can reduce the reactivity of lattice oxygen, resulting in increased hydrogen production, to eliminate catalyst hot-spots.
Co-reporter:Huiping Liu, Guanzhong Lu, Yun Guo, Yanqin Wang, Yanglong Guo
Journal of Colloid and Interface Science 2010 Volume 346(Issue 2) pp:486-493
Publication Date(Web):15 June 2010
DOI:10.1016/j.jcis.2010.03.018
Spherical-like Pt–MCM-41 meso-materials, including Pt–MCM-41, Pt–Al–MCM-41, and Pt–La–MCM-41, as well as MCM-41, were synthesized by a “one-step” approach with orthosilicate (TEOS) as silica source and cetyltrimethylammonium bromide (CTAB) as a template in the presence of suitable H2SO4 (or HCl) at 0 °C. The samples were characterized by XRD, N2 sorption, FTIR, SEM, TEM, ICP-AES, and XPS techniques. The results show that the metallic cations (such as Al3+ and La3+) were hard to be incorporated into the synthesized samples under strong acidic conditions. However, H2PtCl6 can be introduced almost 100% in the as-synthesized Pt-containing meso-materials, and H2PtCl6 in the samples can be decomposed mostly into metallic Pt accompanied by part Pt2Si and few Pt oxides during the calcination at 550 °C to remove the template. In the catalytic hydrogenation of nitrobenzene, the calcined Pt–MCM-41 meso-materials, like the corresponding reduced samples, exhibit high catalytic activities with an excellent selectivity to aniline, which are much better than those of the reduced Pt/MCM-41 prepared by the incipient wetness method.Pt–MCM-41 synthesized in the presence of H2SO4 (or HCl) at 0 °C has spherical-like morphology. TEM image of as-synthesized Pt–MCM-41 indicates that it is composed of spherical-like particles with different nano-sizes.
Co-reporter:Yangang Wang, Yanqin Wang, Jiawen Ren, Yan Mi, Fengyuan Zhang, Changlin Li, Xiaohui Liu, Yun Guo, Yanglong Guo, Guanzhong Lu
Journal of Solid State Chemistry 2010 Volume 183(Issue 2) pp:277-284
Publication Date(Web):February 2010
DOI:10.1016/j.jssc.2009.11.009
Recently, extensive works have been devoted to the morphology control of mesoporous materials with respect to their use in various applications. In this paper, we used two kinds of mesoporous silica, SBA-15 rods and spheres as hard templates to synthesize morphology-controllable mesoporous metal oxides. By carefully controlling the loading of metal precursors in the mesopores of the hard template, mesoporous Co3O4 and CeO2 with different morphologies, such as micrometer-sized rod, hollow sphere, saucer-like sphere, and solid sphere were conveniently obtained. The structural properties of these materials were characterized by XRD, BET, SEM and TEM. In addition, it is found that the differences observed in the textural properties of the two mesoporous metal oxides nanocasted from the same template can be attributed to the properties of metal precursors and the interaction between metal oxide and SiO2. Thus-obtained mesoporous metal oxides with such special morphologies may have a potential application in the field of environmental catalytic oxidation.Mesoporous Co3O4 and CeO2 with different morphologies, such as micrometer-sized rod, hollow sphere, saucer-like sphere, and solid sphere were synthesized by nanocasting.
Co-reporter:Yangang Wang, Fengyuan Zhang, Yong Guo, Yanqin Wang, Jiawen Ren, Dongsheng Qiao, Xiaohui Liu, Guanzhong Lu
Materials Chemistry and Physics 2010 Volume 120(Issue 1) pp:23-30
Publication Date(Web):15 March 2010
DOI:10.1016/j.matchemphys.2009.10.015
In this work, novel three-dimensional (3D) navicular ceria micro/nanocomposite architecture with multi-layered structure was synthesized for the first time via solution reaction followed by a simple hydrothermal treatment in the presence of lysozyme. During the synthesis procedure, a 3D navicular ceria precursor (Ce2O(CO3)2·H2O) with multi-layered structure was obtained after hydrothermal treatment at 100 °C for 10 h. Ceria with the same morphology can be obtained after thermal decomposition of this Ce2O(CO3)2·H2O precursor. Structural properties of the products were characterized by XRD, TG-DTA, FT-IR, SEM, TEM, and N2-sorption techniques. Then a possible layer-by-layer electrostatic self-assembled growth mechanism was proposed for the formation of this 3D navicular architecture based on the experimental results and detail analysis of the evolution process of ceria precursors. Furthermore, a mold reaction of the catalytic oxidation of CO was conducted on the as-obtained CeO2 and gold supported catalyst, both showed excellent activity and durability for CO conversion.
Co-reporter:Zhonghao Jin;Dao Li;Xingyi Wang;Qin Xiao
Chinese Journal of Chemistry 2010 Volume 28( Issue 1) pp:16-20
Publication Date(Web):
DOI:10.1002/cjoc.201090029
Abstract
A range of different nitrophenol derivatives were converted in one-pot to the corresponding secondary alkyl aminophenols in good to excellent yields by using ketones as alkyl source and hydrogen over 10 wt% Pd/C as reducing agent. In all examples, except for one, the secondary amine was the sole alkylation product isolated. When aldehydes were used as alkyl source, the corresponding tertiary amine as a sole alkylation product was isolated.
Co-reporter:Guojun Wang;Shunhai Zhang;Xiaochun Miao;Yun Guo;Guanzhong Lu
Rare Metals 2010 Volume 29( Issue 6) pp:597-603
Publication Date(Web):2010 December
DOI:10.1007/s12598-010-0177-1
VSb3W-Al2O3 catalysts for propane ammoxidation were prepared by the conventional slurry method and new slurry method, namely, the reduction-oxidation slurry method. The effect of preparation methods on the physicochemical properties of VSb3W-Al2O3 catalysts were studied by N2 adsorption, XRD, XPS and Raman spectroscopy, and their catalytic performance for the ammoxidation of propane to acrylonitrile were tested. Compared with the VSb3W-Al2O3 catalyst prepared by the conventional slurry method, the VSb3W-Al2O3 catalyst prepared by the reduction-oxidation slurry method exhibited better propane conversion and acrylonitrile selectivity. This is due to that the reduction-oxidation treatment was advantageous for obtaining low valence state vanadium and high valence state antimony to form more rutile SbVO4, which is a vital active phase for propane ammoxidation.
Co-reporter:Qiuling Luo, Shaodian Shen, Guanzhong Lu, Xiuzhen Xiao, Dongsen Mao and Yanqin Wang
Journal of Materials Chemistry A 2009 vol. 19(Issue 43) pp:8079-8085
Publication Date(Web):15 Sep 2009
DOI:10.1039/B911464E
Cubic ordered mesoporous yttrium phosphate (YPO4) and lanthanide-doped yttrium phosphates (YPO4:Ln3+, Ln3+ = Eu3+, Tb3+ and Ce3+) have been synthesized successfully through the nanocasting route by employing the Y(NO3)3:Ln(NO3)3/H3PO4/HNO3 system as a guest unit and KIT-6 silica as a hard template host, and their textural and structure properties were characterized by X-ray diffraction, transmission electronic microscope and nitrogen adsorption at low temperature. The results show that the cubic ordered mesoporous YPO4 and YPO4:Ln3+ materials exhibit high surface area, large pore volume and uniform pore size distribution. Photoluminescence (PL) measurements exhibit their optical properties such as red, green and blue emission, and their PL intensities can be altered by the dopant Ln3+ concentration, without the need for doping or grafting external fluorophore species.
Co-reporter:Changlin Li, Yanqin Wang, Bianfang Shi, Jiawen Ren, Xiaohui Liu, Yangang Wang, Yun Guo, Yanglong Guo, Guanzhong Lu
Microporous and Mesoporous Materials 2009 Volume 117(1–2) pp:104-110
Publication Date(Web):1 January 2009
DOI:10.1016/j.micromeso.2008.06.017
MFI nanozeolite microspheres with intercrystal mesopores were synthesized by a steam-assisted crystallization–aggregation method, starting with close packed amorphous SiO2 or Al-containing SiO2 colloidal nanoparticles. The obtained samples with different Si/Al ratios were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy (SEM)/ transmission electron microscopy (TEM) observations, nitrogen adsorption analyses and 27Al magic angle spinning nuclear magnetic resonance (NMR). The SEM images clearly showed that the mean size of nanozeolite microspheres was ca. 0.5–3 μm, agglomerated from zeolite nanocrystals and varied with different Si/Al ratios. N2 sorption analyses as well as TEM micrographs indicated the dual-porosity of samples, one is from intracrystal micropores, and the other is from intercrystal mesopores. 27Al MAS-NMR suggested nearly all of the Al atoms were located at tetrahedral-coordinated sites in the framework. Furthermore, nanozeolite microspheres with various Si/Al ratios, even Si/Al equal to five, could be prepared by this facile route and less structure-directing agent was needed compared to conventional approach. This simple method could be easily extended to prepare other hierarchically structured zeolites.
Co-reporter:Yongxia Miao, Guanzhong Lu, Xiaohui Liu, Yanglong Guo, Yanqin Wang, Yun Guo
Microporous and Mesoporous Materials 2009 Volume 122(1–3) pp:55-60
Publication Date(Web):1 June 2009
DOI:10.1016/j.micromeso.2009.02.010
The Mo-containing MCF (Mo-MCF) material was synthesized hydrothermally and used to catalyze the epoxidation of propylene with cumene hydroperoxide (CHP). The structure properties of the catalyst and the structure of surface molybdenum species were characterized by BET, TEM, XRD, Raman and UV–vis spectroscopies. It has been shown that, the Mo-MCF material has the meso-structure of silica MCF after introduction of molybdenum, and there are three molybdenum species of the isolated molybdenum species, polymolybdate species and little crystalline MoO3 of <5 nm existed in the MCF support, among which isolated and poly-molybdenum species are responsible for an increase of the epoxidation selectivity. The distribution of the molybdenum species is obviously affected by the preparation process. On the MoO3/MCF catalyst prepared by an impregnation, more polymolybdate species would congregate into dense MoO3, resulting in a decrease of the epoxidation selectivity. Comparatively, HMS, SBA-15 and SiO2 support were used to study the effect of the textural properties on the catalytic performance of Mo-containing catalyst. The results show that the structure character of support is another important factor to influence the catalytic performance of the catalyst, and the Mo-MCF material having the structure that is favorable for CHP molecules to access the active Mo sites, would restrain the decomposition of CHP and help to increase the epoxidation selectivity.
Co-reporter:Cun Wen, Yi Liu, Yun Guo, Yanqin Wang, Guanzhong Lu
Solid State Sciences 2009 Volume 11(Issue 11) pp:1985-1991
Publication Date(Web):November 2009
DOI:10.1016/j.solidstatesciences.2009.07.007
Synthesis of rare earth compound nanosheets with uniform thickness is of potential interest to the luminescent materials. Herein, whole series of rare earth hydrates and oxides nanosheets have been synthesized by using lamellar liquid crystal as a template, except Ce and Pm. Polarizing microscope images and transmission electron microscopy images show that the lamellar liquid crystal can prevent the rare earth hydrate nanosheets from curving to nanotubes in the processes of synthesis. The synthesized nanosheets have a uniform thickness of 10–15 nm and can retain morphology after being calcined at 650 °C. After facile chemical treatment, the functionalized rare earth compounds were obtained, which have unique luminescent property.
Co-reporter:Yangang Wang, Fengyuan Zhang, Yanqin Wang, Jiawen Ren, Changlin Li, Xiaohui Liu, Yun Guo, Yanglong Guo, Guangzhong Lu
Materials Chemistry and Physics 2009 Volume 115(2–3) pp:649-655
Publication Date(Web):15 June 2009
DOI:10.1016/j.matchemphys.2009.01.027
Monodispersed SBA-15 rods with different lengths (from hexagonal platelets to short rods, and to longer rods) have been synthesized by using triblock copolymer P123 as a structure-directing agent and glycerol as a cosolvent. Our studies showed that glycerol is indispensable for tuning the length of SBA-15 rods. And, in the presence of glycerol, the length of these SBA-15 rods was reversely proportional to the concentration of the acid (HCl) in the synthetic mixture. Based on our characterizations (XRD, SEM, TEM, N2-sorption, and dynamic light scattering (DLS) analyses) and the literature results, a possible glycerol-induced growth mechanism was proposed for the formation of these SBA-15 rods. Furthermore, an adsorption of lysozyme on these SBA-15 materials was investigated and the results showed that they all exhibited rapid lysozyme immobilization and high adsorption capacity (the highest up to 907 mg g−1 for capsulelike SBA-15 synthesized at MHCl = 2.0 M).
Co-reporter:Yongxia Miao, Guanzhong Lu, Xiaohui Liu, Yanglong Guo, Yanqin Wang, Yun Guo
Journal of Molecular Catalysis A: Chemical 2009 Volume 306(1–2) pp:17-22
Publication Date(Web):1 July 2009
DOI:10.1016/j.molcata.2009.02.017
The 15% MoO3/SiO2 catalysts were synthesized by a modified base-catalyzed sol–gel method and characterized by Raman, XRD, FT-IR, UV–vis, NH3-TPD and ICP. The catalytic performance of MoO3/SiO2 for the liquid phase epoxidation of propylene with cumene hydroperoxide (CHP) and the effects of preparation procedure on its physicochemical and catalytic properties were studied. The results show that, in the processes of preparing catalyst, the solvent of ammonium heptamolybdate and the sequence of feeding would affect the existing states of molybdenum species on silica support significantly. When 1,2-propanediol was used as the solvent and an appropriate sequence of feeding was adopted, the β-MoO3 species and monomeric molybdenum species can form on silica to make for the promotion of MoO3/SiO2 catalyst. Without any depressor in the reaction system, at 80 °C and 2.2 MPa for 4 h, the conversion of CHP is above 99% and the selectivity to PO reaches 85.3%.The MoO3/SiO2 catalyst was synthesized for the epoxidation of propylene with cumene hydroperoxide. The base-catalyzed sol–gel method is very effective to prepare the MoO3/SiO2 catalyst, but the preparation procedure affects the physicochemical and catalytic properties of the MoO3/SiO2 catalyst significantly. The presence of small size of β-MoO3 and monomeric molybdenum species on SiO2 are in favor of increasing its catalytic performance.
Co-reporter:Xin Gu, Changlin Li, Xiaohui Liu, Jiawen Ren, Yanqin Wang, Yanglong Guo, Yun Guo and Guanzhong Lu
The Journal of Physical Chemistry C 2009 Volume 113(Issue 16) pp:6472-6479
Publication Date(Web):2017-2-22
DOI:10.1021/jp810749s
Nanosized multilayered silica vesicles have been synthesized through a dual-template way by using cetyltrimethylammonium bromide (CTAB) and C3F7O(CFCF3CF2O)2CFCF3 CONH(CH2)3N+(C2H5)2CH3I− (FC-4) as the cotemplates and tetraethyl orthosilicate (TEOS) as the siliceous precursor. According to transmission electron microscopy, X-ray diffraction, and N2 sorption analysis, the formation of the multilayered silica vesicles passed through the route of the normal mesoporous silica spheres (MCM-41) to irregular hexagonal structures with cavities inside MCM-41 spheres and finally to the small-sized multilayered siliceous vesicles with the increase of FC-4/CTAB molar ratio. The possible mechanism of the two kinds of micelles cooperation was discussed. The synthesized silica vesicle spheres were 30−40 nm with a few shells that may facilitate the transport of the molecules. Furthermore, the vesicular structure was also obtained by aging at 150 °C, which maintained high surface area even after hydrothermal treatment in boiling water for 48 h. The higher hydrothermal stability, high surface area, and pore volume would benefit the loading of catalysts and increase the adsorption capacity.
Co-reporter:Hai-Feng Wang, Xue-Qing Gong, Yang-Long Guo, Yun Guo, Guanzhong Lu and P. Hu
The Journal of Physical Chemistry C 2009 Volume 113(Issue 15) pp:6124-6131
Publication Date(Web):2017-2-22
DOI:10.1021/jp810608c
Structures and catalytic activities of Au thin films supported at anatase TiO2(101) and a Au substrate are studied by using density functional theory calculations. The results show that O2 can hardly adsorb at flat and stepped Au thin films, even supported by fully reduced TiO2(101) that can highly disperse Au atoms and offer strong electronic promotion. Interestingly, in both oxide-supported and pure Au systems, wire-structured Au can adsorb both CO and O2 rather strongly, and kinetic analysis suggests its high catalytic activity for low-temperature CO oxidation. The d-band center of Au at the catalytic site is determined to account for the unusual activity of the wire-structured film. A generalized structural model based on the wire-structured film is proposed for active Au, and possible support effects are discussed: Selected oxide surfaces can disperse Au atoms and stabilize the formation of a filmlike structure; they may also serve as a template for the preferential arrangement of Au atoms in a wire structure under low Au coverage.
Co-reporter:Huiping Liu;Guanzhong Lu;Yun Guo;Yanqin Wang
Central European Journal of Chemistry 2009 Volume 7( Issue 4) pp:
Publication Date(Web):2009 December
DOI:10.2478/s11532-009-0071-6
Using glucose as a structuring additive and aluminium nitrate as the Al precursor, a novel kind of mesoporous Al2O3 microspheres with flower-like structure were synthesized hydrothermally at 180°C for 20 h. When the synthesis temperature was lowered to 140°C, the carambola-like Al2O3 can be synthesized. This approach is convenient and simple, and flower-like Ce-Al2O3 and La-Al2O3 spheres have also been prepared in this way. It may be applied to synthesize other metal oxides when suitable precursor salts are used. From an analysis of the experimental results, a mechanism for the formation of the flower-like Al2O3 spheres has been proposed and discussed.
Co-reporter:Hai-Feng Wang, Yang-Long Guo, Guanzhong Lu and P. Hu
The Journal of Physical Chemistry C 2009 Volume 113(Issue 43) pp:18746-18752
Publication Date(Web):September 30, 2009
DOI:10.1021/jp904371f
By combining density functional theory calculation and microkinetic analysis, NO oxidation on the platinum group metal oxides (PtO2, IrO2, OsO2) is investigated, aiming at shedding light on the activities of metal oxides and exploring the activity variations of metal oxides compared to their corresponding metals. A microkinetic model, taking into account the possible low diffusion of surface species on metal oxide surfaces, is proposed for NO oxidation. The resultant turnover frequencies of NO oxidation show that under the typical experimental condition, T = 600 K, pO2 = 0.1 atm, pNO = 3 × 10−4 atm, pNO2 = 1.7 × 10−4 atm; (i) IrO2(110) exhibits higher activity than PtO2(110) and OsO2(110), and (ii) compared to the corresponding metallic Pt, Ir, and Os, the activity of PtO2 to catalyze NO oxidation is lower, but interestingly IrO2 and OsO2 exhibit higher activities. The reasons for the activity differences between the metals and oxides are addressed. Moreover, other possible reaction pathways of NO oxidation on PtO2(110), involving O2 molecule (NO + O2 → OONO) and lattice bridge-O2c, are also found to give low activities. The origin of the Pt catalyst deactivation is also discussed.
Co-reporter:Yangang Wang, Jiawen Ren, Xiaohui Liu, Yanqin Wang, Yun Guo, Yanglong Guo, Guanzhong Lu
Journal of Colloid and Interface Science 2008 Volume 326(Issue 1) pp:158-165
Publication Date(Web):1 October 2008
DOI:10.1016/j.jcis.2008.07.012
Co-reporter:Hong Liu, Guanzhong Lu, Yanglong Guo, Yun Guo, Junsong Wang
Microporous and Mesoporous Materials 2008 Volume 108(1–3) pp:56-64
Publication Date(Web):1 February 2008
DOI:10.1016/j.micromeso.2007.03.027
A series of Fe-HMS mesostructure materials were synthesized at ambient temperature using alkylamines as the structure director. The Fe-HMS materials were characterized by XRD, DRS UV–Vis, ICP-AES, TEM and N2 adsorption. The effects of the synthesis conditions, such as the ratio of Fe/Si, chain length of surfactant, the surfactant/SiO2 ratio, synthesis time, usage of isopropyl alcohol, the H2O/SiO2 ratio and the ethanol/SiO2 ratio on the textural properties of the Fe-HMS materials were investigated. The results show that the incorporation of iron ions into the framework of HMS material is mainly tetrahedrally coordinated. After the synthesis solution was aged for 3 h Fe-HMS mesostructure has formed, and the pore structure of Fe-HMS materials is affected hardly by the synthesis time. The pore diameter of Fe-HMS can be modified by changing the chain length of surfactant and the ratios of Fe/Si, H2O/SiO2 and ethanol/SiO2. The presence of isopropyl alcohol in the synthesis gel helps to the successful synthesis of the Fe-HMS materials. The Fe-HMS mesostructure material is a highly efficient catalyst for the hydroxylation of phenol in the fixed-bed reactor.
Co-reporter:Yongjun Lü, Yanglong Guo, Yanqin Wang, Xiaohui Liu, Yunsong Wang, Yun Guo, Zhigang Zhang, Guanzhong Lu
Microporous and Mesoporous Materials 2008 Volume 114(1–3) pp:507-510
Publication Date(Web):1 September 2008
DOI:10.1016/j.micromeso.2007.12.027
Penicillin G acylase (PGA) was immobilized on KIT-6 and SBA-15 with different pore sizes to study the influence of pore size, pore volume and mesophases on the immobilized enzyme (IME) activity. The results show that the pore size, pore volume, mesophase and surface area have an obvious influence on the IME activity, of which the pore size is the most important factor. The activity of PGA immobilized on KIT-6/130 reaches to 3522 IU/g by dry support, which is higher than that ever reported for carrier-bound penicillin G acylase [A.I. Kallenberg, F. van Rantwijk, R.A. Sheldon, Adv. Synth. Catal. 347 (2005) 905–926]. Because of the covalent immobilization, the operational stability of IME increases.
Co-reporter:Yangang Wang, Xiaohong Yuan, Xiaohui Liu, Jiawen Ren, Weiyi Tong, Yanqin Wang, Guanzhong Lu
Solid State Sciences 2008 Volume 10(Issue 9) pp:1117-1123
Publication Date(Web):September 2008
DOI:10.1016/j.solidstatesciences.2007.11.018
In this paper, a series of ordered mesoporous single-crystal Cr2O3 samples were synthesized through a hard-templating pathway by using three-dimensional (3D) cubic mesoporous silica, KIT-6, as the template and chromium nitrate as the precursor. In the synthesis, the intermediate composites (chromium nitrate/KIT-6) were calcined in air for 4 h at different temperatures (from 400 to 700 °C, interval 100 °C) to decompose the nitrate species. Then, the silica template was removed by dissolution in 10% HF solution twice. The resulting Cr2O3 samples were characterized by XRD, TEM, XPS, and N2-sorption analysis and their catalytic properties were also investigated in the oxidation of toluene. These results showed that the obtained ordered mesoporous Cr2O3 are exact reverse-replica of the template. It was also found that the catalytic activity was related to mesostructure and/or surface area as well as the calcination temperatures.A series of ordered mesoporous single-crystal Cr2O3 catalysts for the toluene oxidation were prepared through a hard-templating pathway and characterized by XRD, TEM, XPS, and N2-sorption analysis. These results showed that the obtained ordered mesoporous Cr2O3 are exact reverse-replica of the template and their catalytic activity was related to mesostructure and/or surface area as well as the calcination temperatures.
Co-reporter:Jun Yu, Guisheng Wu, Dongsen Mao, Guanzhong Lu
Acta Physico-Chimica Sinica 2008 Volume 24(Issue 10) pp:1751-1755
Publication Date(Web):October 2008
DOI:10.1016/S1872-1508(08)60071-6
Pure TiO2 and La-doped TiO2 were prepared by the sol-gel method. Au was supported on TiO2 by the deposition-precipitation (DP) method, and its catalytic activity for CO oxidation was tested. The results showed that doping La in Au/TiO2 could improve its catalytic activity obviously for CO oxidation. The analyses of X-ray diffraction (XRD), temperature-programmed desorption (TPD), and Brunauer-Emmett-Teller (BET) surface area further showed that the presence of La in TiO2 not only increased its surface area and restrained the growth of TiO2 crystallites, but could also enhance the microstrain of TiO2. In terms of O2-TPD, a new adsorbed species O− appeared on the surface of La-doped TiO2. The results of in-situ Fourier transform-infrared (FT-IR) spectroscopy illustrated that the high activity of Au/La2O3-TiO2 was attributed to the presence of La promoting the reactivity of CO adsorbed on the Au site and the formation of the second active site on the surface of TiO2
Co-reporter:Jian-gong Shi;Gang Cao
Journal of Porous Materials 2008 Volume 15( Issue 5) pp:513-517
Publication Date(Web):2008 October
DOI:10.1007/s10934-007-9105-7
A new method to calculate the standard enthalpies (\(\Delta H_{\rm f,zeo}^0\)) of formation of zeolites is founded based on the assumption that the standard enthalpy of formation of zeolite is equal to the sum of the standard enthalpies of all oxide components and the reaction standard enthalpy change between the exchangeable ion oxide and alumina. The results show that the deviation of \(\Delta H_{\rm f,zeo}^0\) of zeolite calculated by this method is less than 0.7% compared with the experimental value of \(\Delta H_{\rm f,zeo}^0\). The standard enthalpy of formation of hypothetical [SiO2] unit in zeolite is suggested to estimate the thermodynamic stability of zeolite. It is found that the presence of crystal water in zeolite is in favor of increasing the thermodynamic stability of zeolite.
Co-reporter:Yangang Wang ; Jiawen Ren ; Yanqin Wang ; Fengyuan Zhang ; Xiaohui Liu ; Yun Guo ;Guanzhong Lu
The Journal of Physical Chemistry C 2008 Volume 112(Issue 39) pp:15293-15298
Publication Date(Web):September 9, 2008
DOI:10.1021/jp8048394
Ordered mesoporous LaCoO3 perovskite with high surface area was synthesized via nanocasting strategy by using ordered mesoporous cubic (Ia3d) vinyl silica as the template. The sample, prepared by filling mesopores in silica template with a La−Co citrate complex precursor followed by calcination and silica removal, was characterized by XRD, TEM, and nitrogen sorption techniques, and its catalytic activity was tested for complete methane oxidation. The wide-angle XRD pattern showed LaCoO3 perovskite was formed and no La-oxide/Co-oxide phases were detected in the obtained material. This LaCoO3 perovskite displayed a high BET surface area of 96.7 m2 g−1 from nitrogen sorption analysis and a three-dimensional ordered mesostructure from TEM images, as well as a small-angle XRD pattern. Moreover, this material showed much higher activity in the complete methane oxidation than the conventional bulk LaCoO3 perovskite. The light-off temperature (T10) and the half-conversion temperature (T50) were at 335 and 470 °C, respectively. Further analysis by means of H2-TPR and XPS techniques showed that the existence of high valent cobalt ions and high content of O22−/O− species contributed to the high activity.
Co-reporter:Y. Lü;G. Lu;Y. Wang;Y. Guo;Y. Guo;Z. Zhang;Y. Wang;X. Liu
Advanced Functional Materials 2007 Volume 17(Issue 13) pp:
Publication Date(Web):2 AUG 2007
DOI:10.1002/adfm.200600505
Functionalized cubic Ia3d mesoporous silica (FCIMS) with glycidoxypropyl groups was prepared and characterized by powder XRD, N2 adsorption, TGA, FT-IR spectroscopy, solid state 13C NMR spectroscopy and TEM, and studied as the support for the immobilization of Penicillin G acylase (PGA). The results show that the glycidoxypropyl groups have been chemically bonded to the silicon atoms on the surface of cubic Ia3d mesoporous silica (CIMS). The FCIMS materials possess the mesoporous structure with pore diameter of 8 nm which is ∼ 1 nm less than that of CIMS (9 nm). The influence of the amount of glycidoxypropyl groups on the initial specific activity and operational stability of PGA immobilized on FCIMS were examined for the hydrolysis of penicillin G potassium salt. The results show that PGA has been successfully immobilized covalently on the FCIMS materials, and the initial specific activity of PGA/FCIMS is 835 IU g–1 and PGA/CIMS is 624 IU g–1. After repeated use for 10 times, PGA/FCIMS retains 72 % of its initial specific activity and PGA/CIMS retains only 58 %.
Co-reporter:Yaojun Wang, Xiaohui Liu, Rui Zhao, Yanqin Wang, Yanglong Guo, Yun Guo, Zhigang Zhang, Yunsong Wang, Guanzhong Lu
Microporous and Mesoporous Materials 2007 Volume 102(1–3) pp:325-332
Publication Date(Web):4 May 2007
DOI:10.1016/j.micromeso.2006.12.047
In this paper, different organic group-functionalized mesoporous ethanesilicas have been synthesized by the co-condensation of 1,2-bis-(triethoxysilyl) ethane (BTEE) and organosilanes under basic conditions, using cetyltrimethylammonium bromide (CTAB) as a template. High quality mesoporous materials were obtained with MCM-41-type structure. But the employing of different organic groups, such as vinyl, aminopropyl, glycidoxypropyl, mercaptopropyl, leads to different morphologies. The ratio of organosilane to BTEE also affects the mesostructures and morphologies of the final materials. Using the similar method, Ce-doped mesoporous ethanesilica was also obtained.
Co-reporter:Rui Zhao, Yanqin Wang, Yanglong Guo, Yun Guo, Xiaohui Liu, Zhigang Zhang, Yunsong Wang, Wangcheng Zhan and Guanzhong Lu
Green Chemistry 2006 vol. 8(Issue 5) pp:459-466
Publication Date(Web):15 Mar 2006
DOI:10.1039/B517656E
Cerium-containing AlPO-5 with an AFI structure has been prepared by hydrothermal synthesis in the presence of HF, and characterized by XRD, XPS, SEM, N2 adsorption/desorption, solid state 27Al, 31P MAS NMR and TG-DTA techniques. The results show that all the samples have good crystallinity, high dispersity of Ce and high surface area, and Ce(III) replaces the position of Al(III) and enters the framework of AlPO-5. Ce/AlPO-5 is a very efficient catalyst for the oxidation of cyclohexane in a solvent-free system with oxygen as an oxidant. In the condition of 0.5 MPa O2 and 413 K for 4 h, the conversion of cyclohexane is 13%, the total selectivity of cyclohexanol and cyclohaxnone is above 92%. In addition, the Ce/AlPO-5 catalyst is very stable in the cyclohexane oxidation system.
Co-reporter:Guojie Jin, Yanglong Guo, Xiaohui Liu, Wei Yao, Yun Guo, Yunsong Wang, Fang Yuan, Guanzhong Lu
Acta Physico-Chimica Sinica 2006 Volume 22(Issue 7) pp:809-814
Publication Date(Web):July 2006
DOI:10.1016/S1872-1508(06)60034-X
The Ag-MoO3 catalyst for direct gas phase epoxidation of propylene was prepared, and in situ FT-IR technology was used to study the adsorption and reaction behavior of propylene, propylene oxide (PO), and the gaseous mixture of propylene and oxygen on the surfaces of Ag and Ag-MoO3 catalysts. The results indicate that on using single Ag catalyst the selectivity to PO is very low, and Ag-MoO3 is an efficient catalyst for the direct epoxidation of propylene using molecular oxygen as oxidant. The studies of in situ FT-IR show that no chemical reaction occurs, within the range of the experimental temperatures, when propylene is adsorbed on the surface of Ag or Ag-MoO3 catalysts, whereas the open-ring, polymerization, and coking of PO adsorbed on the Ag or Ag-MoO3 catalysts can occur at a higher temperature. The presence of MoO3 in the Ag-MoO3 catalyst can inhibit the open-ring and deep reactions of PO to some extent, despite decreasing its activity, which leads to an increase in the selectivity of PO. The lower reaction temperature and shorter contact time are favorable to inhibit the deep reaction of PO on the surface of the catalyst.
Co-reporter:Weijing Lu, Guanzhong Lu, Xu Liu, Yanglong Guo, Junsong Wang, Yun Guo
Materials Chemistry and Physics 2003 Volume 82(Issue 1) pp:120-127
Publication Date(Web):28 September 2003
DOI:10.1016/S0254-0584(03)00207-4
The ZnO supported on γ-Al2O3, SiO2, MCM-41, and β-zeolite were prepared and examined in the hydrogenation of methyl benzoate (MB). ZnO supported on γ-Al2O3 had a higher activity than ZnO. ZnO/γ-Al2O3 modified with 23 ppm lithium had a high catalytic activity (97%) and high selectivity to benzaldehyde (BD, 87%) in a fixed-bed reactor at atmospheric pressure and 400 °C. Chromium oxide modified ZnO/γ-Al2O3 also had a high selectivity to BD. Hydrogenolysis of MB occurred over copper modified catalysts. X-ray powder diffraction (XRD) revealed that in the ZnO/γ-Al2O3 catalysts, the ZnO, ZnAl2O4 and γ-Al2O3 phases exited mainly, the border of ZnO and ZnAl2O4 might be important for the hydrogenation of MB to BD. XPS and FT-IR revealed that the chemical environment of ZnO on the ZnO/γ-Al2O3 catalyst is different to ZnO and other supported ZnO catalysts, which gives the ZnO/γ-Al2O3 catalyst having a higher activity than ZnO or ZnO on SiO2, MCM-41 or β-zeolite. The presence of third metal (Li, Cr or Cu) oxide in ZnO/γ-Al2O3 could change the electronic structure of Zn and the chemical phenomena of Zn–Al in catalyst and lead to change of the catalytic performance.
Co-reporter:Zheng Wang, Pascal Fongarland, Guanzhong Lu, Nadine Essayem
Journal of Catalysis (October 2014) Volume 318() pp:108-118
Publication Date(Web):1 October 2014
DOI:10.1016/j.jcat.2014.07.006
•La and Y insertion in MgAl-HT favors the layered HT structure disorder and the amount of strong/medium basic sites.•On the mixed oxides issued from HT calcination, the rate constants per Lewis basic site were enhanced by the REE.•On rehydrated HT, the rate constants per Brønsted basic sites, OH−, were enhanced but not significantly influenced by REE.•MgAl-HT doped with Y and La presents improved water tolerance for aldol condensation reaction.MgAl-HT modified with La, Y, and Ce were evaluated in liquid-phase acetone self-aldolization as a model reaction. Calcined and rehydrated HT were characterized by XRD, N2 adsorption, IR spectroscopy, and calorimetry of CO2 adsorption. The results show that the introduction of rare earth elements (REE), of larger ionic radius than Al3+, can affect the degree of disorder of HT structure. Thus, La- and Y-modified HT exhibit larger surface areas and smaller particles sizes, resulting in higher specific amounts of medium/strong basic sites (Q > 100 kJ.mol−1). This is also correlated with the lower electronegativities of the REE ions, which may induce slight modifications of the electronic densities of the oxygen atoms, the Lewis basic centers. Calorimetry of CO2 adsorption indicates that the rehydrated HT exhibit basic sites in equivalent amounts but with more homogeneous basic strength distributions. The rehydrated HT catalysts show significant higher rate constants expressed per basic site. This confirms that acetone condensation proceeds faster over Brønsted basic sites compared with the Lewis ones. Over rehydrated HT, the rate constants per Brønsted basic sites are less dependent on the presence or nature of the REE, suggesting that the electronic effect of REE does not affect strongly the activity of the charge compensation anions OH−. The water tolerance of the catalysts was studied in the presence of 1 wt% and 5 wt% H2O in acetone, and the results show that rehydrated MgAl-HT modified with Y and La present a higher water tolerance for aldol condensation, which can be tentatively explained by their higher OH− content preferentially located on the defects of the HT platelets, where the solvation by interlayer water molecules could be limited.Download high-res image (110KB)Download full-size image
Co-reporter:Haitao Yu, Yanglong Guo, Dongliang Wu, Wangcheng Zhan, Guanzhong Lu
Journal of Molecular Catalysis B: Enzymatic (October 2011) Volume 72(Issues 1–2) pp:73-76
Publication Date(Web):1 October 2011
DOI:10.1016/j.molcatb.2011.05.006
Glucose isomerase (GI) from Streptomyces rubiginosus was immobilized covalently onto GAMM support prepared by our patented inverse suspension polymerization with glycidyl methacrylate (GMA), ally glycidyl ether (AGE), N,N′-methylene-bis(acrylamide) (MBAA), and acrylamide (MAA), and used for isomerization of glucose to fructose. Effects of immobilization conditions and reaction conditions on the activity of immobilized GI, the kinetic parameters, the operational stability, thermal stability and storage stability of immobilized GI were investigated. The optimum immobilization conditions were GI addition amount of 0.3 ml GI/g support, immobilization time of 24 h, and immobilization temperature of 25 °C. The optimum reaction conditions were pH value of reaction solution of 7.5 and reaction temperature of 65 °C. The activity of immobilized GI was 450 U/g (wet). Km and Vmax values of immobilized GI were 1.16 mol/L and 1.07 × 10−3 mol/L min, respectively. Immobilized GI onto GAMM support has better operational stability, thermal stability and storage stability, in which it retained 91% of its initial activity after recycled for 18 times and retained 97% of its initial activity after stored at 4 °C for six weeks. Therefore immobilized GI onto GAMM support was an excellent catalyst for isomerization of glucose to fructose.Graphical abstractGlucose isomerase immobilized covalently onto GAMM support, prepared by our patented inverse suspension polymerization, shows better activity of 450 U/g (wet) for isomerization of glucose to fructose and has better operational stability, thermal stability and storage stability.Download full-size imageHighlights► GAMM support was prepared by our patented inverse suspension polymerization. ► Glucose isomerase was immobilized covalently onto GAMM support. ► Immobilized glucose isomerase shows better activity for glucose isomerization.
Co-reporter:Zhenyuan Gao, Wangcheng Zhan, Yanglong Guo, Yunsong Wang, Yun Guo, Guanzhong Lu
Journal of Molecular Catalysis B: Enzymatic (July 2014) Volume 105() pp:111-117
Publication Date(Web):1 July 2014
DOI:10.1016/j.molcatb.2014.04.006
•CHO-MCFs were prepared by post-synthetical functionalization of MCFs.•The aldehydepropyl groups were grafted successfully on the surface of CHO-MCFs.•The ultra-large 3D mesostructure of CHO-MCFs is beneficial for immobilization of PGA.•PGA immobilized covalently on CHO-MCFs increased the operational stability.The aldehydepropyl-functionalized mesostructured cellular foams (CHO-MCFs) were prepared by post-synthetical functionalization of MCFs with trimethoxysilylpropanal (TMSP), and used as efficient supports for immobilization of penicillin G acylase (PGA). The physicochemical properties of CHO-MCFs were characterized by SAXS, nitrogen sorption, TEM, elementary analysis, solid state 29Si MAS NMR, FT-IR spectroscopy and thermogravimetry. The results show that the aldehydepropyl groups have been grafted successfully on the surface of MCFs, and after functionalization, the BET surface area and pore volume of CHO-MCFs decrease, but the ultra-large and continuous 3D mesoporous structure of CHO-MCFs are retained to be beneficial for immobilization of PGA with large size and diffusion of substrates and products. PGA is immobilized covalently on CHO-MCFs via the reaction to produce Schiff's base between the free amino groups of lysine residues of PGA and the aldehyde groups on the surface of CHO-MCFs, which greatly increases the operational stability of the immobilized PGA with little activity loss due to the short-chain groups of aldehydepropyl grafted on the surface of CHO-MCFs. PGA/CHO-MCFs-10 shows the immobilization yield of 57.6%, the specific activity of 22.2 U/mg and the initial enzymatic activity of 8895 U/g, and retains 93.0% of its initial enzymatic activity after recycled for 10 times.Download full-size image
Co-reporter:Hai-Feng Wang, Richard Kavanagh, Yang-Long Guo, Yun Guo, Guanzhong Lu, P. Hu
Journal of Catalysis (December 2012) Volume 296() pp:110-119
Publication Date(Web):1 December 2012
DOI:10.1016/j.jcat.2012.09.005
Understanding and then designing efficient catalysts for CO oxidation at low temperature is one of the hottest topics in heterogeneous catalysis. Among the existing catalysts, Co3O4 is one of the most interesting systems: Morphology-controlled Co3O4 exhibits exceedingly high activity. In this study, by virtue of extensive density functional theory (DFT) calculations, the favored reaction mechanism in the system is identified. Through careful analyses on the energetics of elementary reactions on Co3O4(1 1 0)-A, Co3O4(1 1 0)-B, Co3O4(1 1 1) and Co3O4(1 0 0), which are the commonly exposed surfaces of Co3O4, we find the following regarding the relation between the activity and structure: (i) Co3+ is the active site rather than Co2+; and (ii) the three-coordinated surface oxygen bonded with three Co3+ may be slightly more reactive than the other two kinds of lattice oxygen, that is, the two-coordinated O bonded with one Co2+ and one Co3+ and the three-coordinated O bonded with one Co2+ and two Co3+. Following the results from Co3O4, we also extend the investigation to MnO2(1 1 0), Fe3O4(1 1 0), CuO(1 1 0) and CuO(1 1 1), which are the common metal oxide surfaces, aiming to understand the oxides in general. Three properties, such as the CO adsorption strength, the barrier of CO reacting with lattice O and the redox capacity, are identified to be the determining factors that can significantly affect the activity of oxides. Among these oxides, Co3O4 is found to be the most active one, stratifying all the three requirements. A new scheme to decompose barriers is introduced to understand the activity difference between lattice O3c and O2c on (1 1 0)-B surface. By utilizing the scheme, we demonstrate that the origin of activity variance lies in the geometric structures.Graphical abstractDownload high-res image (87KB)Download full-size imageHighlights► The reaction mechanism of low-temperature CO oxidation on Co3O4 is studied. ► The morphology-dependent chemistry of Co3O4 is addressed. ► The surface active site (Co3+) and possible active oxygen species are suggested. ► The origin of high catalytic activities of Co3O4 over other oxides is uncovered.
Co-reporter:Bianfang Shi, Yanqin Wang, Jiawen Ren, Xiaohui Liu, Ye Zhang, Yanglong Guo, Yun Guo, Guanzhong Lu
Journal of Molecular Catalysis B: Enzymatic (April 2010) Volume 63(Issues 1–2) pp:50-56
Publication Date(Web):1 April 2010
DOI:10.1016/j.molcatb.2009.12.003
The superparamagnetic Fe3O4 microspheres about 300 nm diameter were prepared by the solvothermal method. After treated with chlorohydric acid, it was coated with aminopropyl-functionalized amorphous silica by the condensation of tetraethylorthosilicate (TEOS) and γ-aminopropyltriethoxysilane (APTES) through Stöber modified method. FT-IR, elemental analysis and TEM were used to characterize the aminopropyl-functionalized silica-coated magnetic microspheres, and then they were first used as magnetic separation carriers for immobilization of penicillin G acylase (PGA). The results showed that the amino content of the carriers has a little influence on the apparent initial activity, while the immobilization method and the shell thickness have more obvious influence on the apparent initial activity. The immobilized PGA (IMPGA) obtained through covalent attachment almost has no leaching and can retain above 78% of activity after 10 consecutive operations and exhibits higher resistance to thermal stability. More interesting, the silica-coated magnetic microspheres show high saturation magnetization and the obtained IMPGA can be separated quickly using an external magnetic field.
Co-reporter:Jun Yu, Dongsen Mao, Lupeng Han, Qiangsheng Guo, Guanzhong Lu
Catalysis Communications (5 October 2012) Volume 27() pp:1-4
Publication Date(Web):5 October 2012
DOI:10.1016/j.catcom.2012.06.010
Different amounts of Fe promoted Rh–Mn–Li/SiO2 catalysts were prepared and investigated for the synthesis of C2 oxygenates from syngas. The results showed that the low amount of Fe (≤ 0.1 wt.%) improved the reactivity and yield of C2+ oxygenates, but an opposite effect appeared at high content of Fe (> 0.1 wt.%). Diffuse reflectance infrared Fourier transform spectroscopy was used to probe the effects of Fe on CO adsorption and hydrogenation, and two opposing effects were evidenced. Moreover, it is proposed that the facile transformation of dicarbonyl Rh+(CO)2 into H–Rh–CO is responsible for high selectivity of C2+ oxygenates.Different amounts of Fe promoted Rh–Mn–Li/SiO2 catalysts were prepared and investigated for the synthesis of C2 oxygenate from syngas, and the CO conversion and C2 oxygenate selectivity are strongly influenced by the amounts of Fe.Download full-size imageHighlights► The Rh-Mn-Li/SiO2 catalysts promoted with different amounts of Fe were prepared. ► The effect of Fe on CO hydrogenation over Rh-Mn-Li-Fe/SiO2 catalysts was studied. ► The doping of Fe decreased the CO adsorption, further decreased CO conversion. ► Fe doping increased the transform rate of adsorbed CO, so promoted the reaction.
Co-reporter:Mingzhou Wu, Wangcheng Zhan, Yanglong Guo, Yun Guo, Yunsong Wang, Li Wang, Guanzhong Lu
Applied Catalysis A: General (5 August 2016) Volume 523() pp:97-106
Publication Date(Web):5 August 2016
DOI:10.1016/j.apcata.2016.06.001
Co-reporter:Xiaoming Guo, Dongsen Mao, Guanzhong Lu, Song Wang, Guisheng Wu
Journal of Catalysis (4 May 2010) Volume 271(Issue 2) pp:178-185
Publication Date(Web):4 May 2010
DOI:10.1016/j.jcat.2010.01.009
A series of CuO–ZnO–ZrO2 (CZZ) catalysts were synthesized by a glycine–nitrate combustion method and characterized by XRD, BET, N2O chemisorption, SEM and TPR techniques. The results show that the physicochemical properties of the catalysts are strongly influenced by the fuel content used in the combustion process. The dispersion of CuO exhibits an inverse-volcano variation trend with an increase in the glycine amount from 50% to 150% of the stoichiometry. The relationship between physiochemical properties and the fuel content is discussed in detail in terms of combustion temperature. The catalytic performance for the synthesis of methanol from CO2 hydrogenation was examined. The CZZ catalyst exhibits an optimum catalytic activity when 50% of stoichiometric amount of glycine was used. The turnover frequency has been calculated for various CZZ catalysts, and it reveals that the catalytic activities depend not only on the surface area of metallic copper but also on the phase state of ZrO2.The fuel content used for the preparation of CuO–ZnO–ZrO2 catalysts by combustion method had significant effect on CO2 conversion and methanol yield for the synthesis of methanol from CO2 hydrogenation.Download high-res image (74KB)Download full-size image
Co-reporter:Bianfang Shi, Yunsong Wang, Yanglong Guo, Yanqin Wang, Ying Wang, Yun Guo, Zhigang Zhang, Xiaohui Liu, Guanzhong Lu
Catalysis Today (30 October 2009) Volume 148(Issues 1–2) pp:184-188
Publication Date(Web):30 October 2009
DOI:10.1016/j.cattod.2009.02.014
The aminopropyl-functionalized silicas (APFS) with higher loading of amino groups was synthesized by the co-condensation of tetraethylorthosilicate (TEOS) and γ-aminopropyltriethoxysilane (APTES) in W/O microemulsion. Thus synthesized APFS was characterized by FT-IR spectroscopy, thermogravimetry, element analysis, solid state 13C and 29Si MAS NMR, TEM, and N2 sorption. The results show that the aminopropyl groups were condensed as the part of the silicate framework, and the amino contents could be adjusted by changing the volume ratio of APTES to TEOS in W/O microemulsion. APFS has been firstly used as the support for the immobilization of penicillin G acylase after activation with glutaraldehyde. Effects of the volume ratio of APTES to TEOS on the physico-chemical properties of APFS and the performance of immobilized penicillin G acylase were systematically investigated. Penicillin G acylase immobilized on APFS with the volume ratio of APTES/TEOS = 1/9 (1.77 mmol g−1 amino groups) behaves higher specific activity of 2759 IU g−1 and higher operational stability of 86% of the initial specific activity after recycled for 5 times, and the immobilization yield of 97%.
Co-reporter:Xiaohong Wang, Guanzhong Lu, Yun Guo, Yuye Xue, Liangzhu Jiang, Yanglong Guo, Zhigang Zhang
Catalysis Today (30 August 2007) Volume 126(Issues 3–4) pp:412-419
Publication Date(Web):30 August 2007
DOI:10.1016/j.cattod.2007.06.009
The Si-doped Ce–Zr–O solid solutions have been prepared by the reverse microemulsion method. The effects of Si and its content on the structure characters, thermal-stability and reducibility of the Ce–Zr–O solid solution have been studied by N2 adsorption, XRD, laser Raman (LR), TPR, FT-IR, NMR and XPS methods. The results indicate that, there are the bonds of Si–O–M (Ce or Zr) in the Ce–Zr–Si–O solid solutions, and the presence of Si can increase obviously the surface area, thermal-stability, crystal lattice distortion rate, and reducibility of the solid solution. The surface area of the sample with 20 wt.% Si reaches 153 m2 g−1 after being calcined at 900 °C for 6 h. The Ce–Zr–O solid solution with 5.2–10 wt.% Si shows excellent thermal-stability and reducibility.
Co-reporter:Xiaohong Wang, Yun Guo, Guanzhong Lu, Yu Hu, Liangzhu Jiang, Yanglong Guo, Zhigang Zhang
Catalysis Today (30 August 2007) Volume 126(Issues 3–4) pp:369-374
Publication Date(Web):30 August 2007
DOI:10.1016/j.cattod.2007.06.011
Thermal-stable Si-doped alumina was prepared by the reverse microemulsion method and was used as the support of Pd catalyst for the methane combustion. The physicochemical properties of Si-alumina and catalytic performance of Pd/Si-Al2O3 were characterized by XRD, N2 adsorption, FT-IR, XPS and methane catalytic combustion. The results indicate that the presence of Si can increase the thermal stability of alumina and promote the coordination state of aluminum from tetrahedral to octahedral, but its content added should be controlled appropriately to 5–6 wt%. Si-doped alumina prepared by the reverse microemulsion method is an excellent support of Pd catalyst for the methane combustion, which can increase both the catalytic activity and thermal stability of the Pd catalyst. The studies also show that the calcination temperature of support affects remarkably the performance of catalyst, and the high thermal stability of support is very important to increase the performance of Pd catalyst for the methane combustion.
Co-reporter:Yun Guo, Guanzhong Lu, Zhigang Zhang, Shunhai Zhang, Yan Qi, Yi Liu
Catalysis Today (30 August 2007) Volume 126(Issues 3–4) pp:296-302
Publication Date(Web):30 August 2007
DOI:10.1016/j.cattod.2007.06.033
Nanoparticles of CexZr1−xO2 (x = 0.75, 0.62) were prepared by the oxidation-coprecipitation method using H2O2 as an oxidant, and characterized by N2 adsorption, XRD and H2-TPR. CexZr1−xO2 prepared had single fluorite cubic structure, good thermal stability and reduction property. With the increasing of Ce/Zr ratio, the surface area of CexZr1−xO2 increased, but thermal stability of CexZr1−xO2 decreased. The surface area of Ce0.62Zr0.38O2 was 41.2 m2/g after calcination in air at 900 °C for 6 h. TPR results showed the formation of solid solution promoted the reduction of CeO2, and the reduction properties of CexZr1−xO2 were enhanced by the cycle of TPR-reoxidation. The Pd-only three-way catalysts (TWC) were prepared by the impregnation method, in which Ce0.75Zr0.25O2 was used as the active washcoat and Pd loading was 0.7 g/L. In the test of Air/Fuel, the conversion of C3H8 was close to 100% and NO was completely converted at λ < 1.025. The high conversion of C3H8 was induced by the steam reform and dissociation adsorption reaction of C3H8. Pd-only catalyst using Ce0.75Zr0.25O2 as active washcoat showed high light off activity, the reaction temperatures (T50) of 50% conversion of CO, C3H8 and NO were 180, 200 and 205 °C, respectively. However, the conversions of C3H8 and NO showed oscillation with continuously increasing the reaction temperature. The presence of La2O3 in washcoat decreased the light off activity and suppressed the oscillation of C3H8 and NO conversion. After being aged at 900 °C for 4 h, the operation windows of catalysts shifted slightly to rich burn. The presence of La2O3 in active washcoat can enhance the thermal stability of catalyst significantly.
Co-reporter:Dongsheng Qiao, Guanzhong Lu, Dongsen Mao, Xiaohui Liu, Hongfeng Li, Yun Guo, Yanglong Guo
Catalysis Communications (30 April 2010) Volume 11(Issue 9) pp:858-861
Publication Date(Web):30 April 2010
DOI:10.1016/j.catcom.2010.03.010
Methane catalytic combustion was carried out over a series of Ca doped Ce0.9 − xCu0.1CaxOδ (0 < x ≤ 0.3) catalysts prepared by the citric acid complexation–combustion method. The catalyst with x = 0.05 showed the optimum activity, with T50 = 478 °C, 60 °C lower than that of Ca undoped catalyst. The Ca doping promoted the formation of oxygen vacancies of the catalyst. With the increase in Ca amount, more carbonate species were formed on the catalyst surfaces. The carbonate species produced on the catalysts after long-term reaction, were proposed to be responsible for the activity loss of the catalysts.
Co-reporter:Yuexin Shen, Guanzhong Lu, Yun Guo, Yanqin Wang, Yanglong Guo, Xueqing Gong
Catalysis Today (25 October 2011) Volume 175(Issue 1) pp:558-567
Publication Date(Web):25 October 2011
DOI:10.1016/j.cattod.2011.03.042
The Pd–Cu–Clx/Al2O3 catalysts were prepared by an NH3 coordination-impregnation (CI) method in water and organic solvents, and exhibited much higher activity for CO oxidation than the catalyst prepared by conventional wet impregnation (WI) method. Their chemical and physical properties were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature-programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS) and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The results show that in the process of preparing the catalysts by CI, different solvents affect obviously their catalytic performance and isopropanol is the most suitable solvent among water, ethanol, acetone and isopropanol. The CO oxidation over Pd–Cu–Clx/Al2O3 catalyst (CI) can be accelerated remarkably with an increase of H2O concentration in the reactant gas, and it is weakly dependent on the CO and O2 concentrations. Compared with the catalyst prepared by WI, the catalyst prepared by CI possesses the higher dispersion and lower-temperature reducibility of copper phase, much more active Cu2+ species, and easier re-oxidation of Cu+. The Pd+ active site on the catalyst (CI) is more active than Pd2+ on the catalyst (WI), and the rate-determining step is the re-oxidation of Pd0 to Pd+ by Cu2+ on the catalyst (CI) instead of the re-oxidation of Cu+ to Cu2+ by O2 on the catalyst (WI).Graphical abstractDownload high-res image (131KB)Download full-size imageHighlights► Pd–Cu–Clx/Al2O3 possesses much more active Cu2+ species. ► Pd+ is the higher active palladium species than Pd2+. ► The re-oxidation of Cu+ to Cu2+ can be accelerated over Pd–Cu–Clx/Al2O3. ► The rate-determining step is the re-oxidation of Pd0 by Cu2+ over Pd–Cu–Clx/Al2O3.
Co-reporter:Wen-Jun Zhu, Jie Zhang, Xue-Qing Gong, Guanzhong Lu
Catalysis Today (16 May 2011) Volume 165(Issue 1) pp:19-24
Publication Date(Web):16 May 2011
DOI:10.1016/j.cattod.2010.11.085
Density functional theory calculations corrected for on-site Coulomb interactions (DFT + U) have been performed to study supported rare earth catalysts with small Au nanoclusters (Au trimer, Au3) adsorbed at CeO2 surfaces. The interaction of Au3 with all the three major facets of crystalline CeO2, namely CeO2(1 1 1), (1 1 0) and (1 0 0), were systematically investigated. The results showed that Au3 can adsorb rather strongly at the surfaces (Eads > 3 eV), and partially reduce the CeO2 support by filling the originally empty 4f orbital of one surface Ce with an electron. Moreover, corresponding to different configurations of surface relaxation caused by Au3 adsorption, the localized 4f electron can occur at different surface Ce near the Au3 at each surface. By calculating adsorption of O2, we also showed that only the surface Ce at Au3/CeO2(1 1 0) are capable of strongly holding and activating the O2.
Co-reporter:Ling Yang, Zhenyuan Gao, Yanglong Guo, Wangcheng Zhan, Yun Guo, Yunsong Wang, Guanzhong Lu
Enzyme and Microbial Technology (10 June 2014) Volume 60() pp:32-39
Publication Date(Web):10 June 2014
DOI:10.1016/j.enzmictec.2014.03.011
•NH2-Fe3O4 nanoparticles were successfully grafted on the outer surface of AMCFs.•PGA molecules were mainly immobilized covalently on the inner surface of PAMCFs.•PGA/PAMCFs show higher initial activity and operational stability.•PGA/PAMCFs are easily recycled by the magnetic field.Paramagnetic aldehyde-functionalized mesostructured cellular foams (PAMCFs), synthesized by grafting 3-aminopropyltriethoxysilane modified Fe3O4 (NH2-Fe3O4) nanoparticles with larger particle size than the window pore size of MCFs on the outer surface of aldehyde-functionalized mesostructured cellular foams (AMCFs), were investigated as efficient supports for immobilization of penicillin G acylase (PGA). The results show that NH2-Fe3O4 nanoparticles were successfully grafted on the outer surface of AMCFs and PGA molecules were mainly immobilized covalently on the inner surface of PAMCFs, which was because amino groups of NH2-Fe3O4 nanoparticles or PGA molecules reacted with aldehyde groups of AMCFs or PAMCFs to form imine bonds. PGA/PAMCFs-15 showed a rather high initial activity of 9563 U g−1 and retained 89.1% of its initial activity after recycled for 10 times. PGA/PAMCFs are easily recycled by magnetic field in order to replace tedious separation of high-speed centrifugation for mesoporous materials.Download full-size image
Co-reporter:Jianan Xu, Guanzhong Lu, Yun Guo, Yanglong Guo, Xue-Qing Gong
Applied Catalysis A: General (10 April 2017) Volume 535() pp:1-8
Publication Date(Web):10 April 2017
DOI:10.1016/j.apcata.2017.02.005
Co-reporter:Yuye Xue, Guanzhong Lu, Yun Guo, Yanglong Guo, Yanqin Wang, Zhigang Zhang
Applied Catalysis B: Environmental (1 March 2008) Volume 79(Issue 3) pp:262-269
Publication Date(Web):1 March 2008
DOI:10.1016/j.apcatb.2007.10.027
Co-reporter:Xiaoming Guo, Dongsen Mao, Guanzhong Lu, Song Wang, Guisheng Wu
Catalysis Communications (1 July 2011) Volume 12(Issue 12) pp:1095-1098
Publication Date(Web):1 July 2011
DOI:10.1016/j.catcom.2011.03.033
Cu/ZnO/ZrO2 catalysts were prepared by a route of solid-state reaction and tested for the synthesis of methanol from CO2 hydrogenation. The effects of calcination temperature on the physicochemical properties of as-prepared catalysts were investigated by N2 adsorption, XRD, TEM, N2O titration and H2-TPR techniques. The results show that the dispersion of copper species decreases with the increase in calcination temperature. Meanwhile, the phase transformation of zirconia from tetragonal to monoclinic was observed. The highest activity was achieved over the catalyst calcined at 400 °C. This method is a promising alternative for the preparation of highly efficient Cu/ZnO/ZrO2 catalysts.Cu/ZnO/ZrO2 catalysts for methanol synthesis from CO2 hydrogenation were prepared via a route of solid-state reaction, and the CO2 conversion and methanol selectivity are strongly influenced by the calcination temperature.Download full-size imageResearch Highlights►Cu/ZnO/ZrO2 catalysts were prepared by a route of solid-state reaction. ►The dispersion of copper decreases with the increase in calcination temperature. ►Phase transformation of ZrO2 occurs with the increase in calcination temperature. ►The highest activity was achieved over the catalyst calcined at 400 °C.
Co-reporter:Chenhao Du, Guanzhong Lu, Yun Guo, Yanglong Guo, and Xue-qing Gong
ACS Omega Volume 1(Issue 1) pp:118-126
Publication Date(Web):July 19, 2016
DOI:10.1021/acsomega.6b00050
A simple, one-pot method to fabricate ordered, monodispersed Pd–CeO2 colloidal assembled spheres (CASs) was developed using the surfactant-mediated solvothermal approach, which involves a tunable self-assembled process by carefully controlling different chemical reactions. The evolution process and formation mechanism of the CASs were thoroughly investigated by time-controlled and component-controlled experiments. For CO oxidation, this CAS nanocatalyst exhibited much higher catalytic activity and thermal stability than Pd/CeO2 prepared by an impregnation method, and its complete CO conversion temperature is ∼120 °C. The enhanced catalytic performance for CO oxidation could be attributed to the synergistic effect of highly dispersed PdO species and Pd2+ ions incorporated into the CeO2 lattice. For this CAS catalyst, each sphere can be viewed as a single reactor, and its catalytic performance can be further improved after being supported on alumina, which is obviously higher than results previously reported. Furthermore, this method was used to successfully prepare M–CeO2 CASs (M = Pt, Cu, Mn, Co), showing further that this is a new and ideal approach for fabricating active and stable ceria-based materials.Topics: Adsorption; Catalysts; Desorption; Diffraction; Distribution function; Microstructure; Nanocomposites; Nanoparticles; Phase; Reaction kinetics; Reaction kinetics; Redox reaction; Redox reaction; Spectra; Surfactants; Thermodynamic properties;
Co-reporter:Qiuling Luo, Shaodian Shen, Guanzhong Lu, Xiuzhen Xiao, Dongsen Mao and Yanqin Wang
Journal of Materials Chemistry A 2009 - vol. 19(Issue 43) pp:NaN8085-8085
Publication Date(Web):2009/09/15
DOI:10.1039/B911464E
Cubic ordered mesoporous yttrium phosphate (YPO4) and lanthanide-doped yttrium phosphates (YPO4:Ln3+, Ln3+ = Eu3+, Tb3+ and Ce3+) have been synthesized successfully through the nanocasting route by employing the Y(NO3)3:Ln(NO3)3/H3PO4/HNO3 system as a guest unit and KIT-6 silica as a hard template host, and their textural and structure properties were characterized by X-ray diffraction, transmission electronic microscope and nitrogen adsorption at low temperature. The results show that the cubic ordered mesoporous YPO4 and YPO4:Ln3+ materials exhibit high surface area, large pore volume and uniform pore size distribution. Photoluminescence (PL) measurements exhibit their optical properties such as red, green and blue emission, and their PL intensities can be altered by the dopant Ln3+ concentration, without the need for doping or grafting external fluorophore species.
Co-reporter:Zhangping Shi, Xiuzhen Xiao, Dongsen Mao and Guanzhong Lu
Catalysis Science & Technology (2011-Present) 2014 - vol. 4(Issue 4) pp:NaN1143-1143
Publication Date(Web):2014/01/22
DOI:10.1039/C3CY00937H
The effects of the preparation method on the properties of Cu/ZnO/Al2O3 catalysts for L-phenylalanine methyl ester hydrogenation to L-phenylalaninol were investigated in detail, including the precipitation method and conditions (the aging time, calcination temperature and so on), with the help of ICP-OES, N2 and N2O adsorption, XRD, H2-TPR and TEM techniques. The results show that physicochemical properties of the catalysts are greatly affected by the preparation method and conditions. The uniform size distribution of CuO species can be obtained by fractional co-precipitation. The appropriate aging time is 2 h, and the catalyst aged for 2 h has the largest metallic copper surface area (SCu) and surface copper amount and the smallest CuO crystallites. The lower calcination temperature is favorable for increasing the surface area and metallic copper surface area of the catalyst. The spinel structure CuAl2O4 phase can form after calcination at 550 °C. The turnover frequency (TOF) values of L-phenylalaninol formed using different catalysts indicate the structurally sensitive character of the title reaction, and SCu is not the sole cause affecting the catalytic activities of the catalysts. B-TOF on the basis of the active sites (Cu0) in the boundary between CuO and ZnO or Al2O3 was proposed; the relationships of B-TOF with dCuO (particle size of CuO) and SCu were established. Using the Cu/ZnO/Al2O3 catalyst prepared by fractional co-precipitation with aging at 70 °C for 2 h and calcination at 450 °C for 4 h, 83.6% selectivity to L-phenylalaninol without racemization was achieved.
Co-reporter:Zhicong Liu, Guanzhong Lu, Yun Guo, Yanqin Wang and Yanglong Guo
Catalysis Science & Technology (2011-Present) 2011 - vol. 1(Issue 6) pp:NaN1012-1012
Publication Date(Web):2011/06/23
DOI:10.1039/C1CY00140J
The effective utilization of coal bed methane (CBM) is very significant for energy utilization and environmental protection, reducing significantly greenhouse gas methane emission. In this paper, La1−xErxCoO3 perovskite (0 ≤ x ≤ 0.4) catalysts for the catalytic deoxidization of CBM were prepared by a co-precipitation method and were characterized by X-ray diffraction (XRD), laser Raman spectroscopy (LRS), H2 and CH4 temperature-programmed reduction (H2, CH4-TPR), CO pulse and N2adsorption/desorption techniques. The results show that the amount of Er affects obviously the physicochemical and catalytic properties of La1−xErxCoO3, and when x = 0.2, La0.8Er0.2CoO3 exhibits the best activity for deoxidization of CBM, because Er doping promotes the activity and migration of the lattice oxygen of La0.8Er0.2CoO3. The influences of the operation parameters (methane concentration, oxygen concentration and space velocity) on the catalytic deoxygenation of CBM and the kinetics behaviours were investigated. The reaction order of removing oxygen is 0.9 for methane partial pressure and −0.6 for oxygen partial pressure.
Co-reporter:Jie Li, Guanzhong Lu, Guisheng Wu, Dongsen Mao, Yanqin Wang and Yun Guo
Catalysis Science & Technology (2011-Present) 2012 - vol. 2(Issue 9) pp:NaN1871-1871
Publication Date(Web):2012/04/24
DOI:10.1039/C2CY20118F
Ceria modified Co3O4 catalysts for low temperature CO oxidation were prepared by a precipitation–oxidation method, and characterized by low-temperature N2 adsorption/desorption, TPR, O2–TPD, CO–TPD and transient–response reaction. The roles of ceria in CeO2–Co3O4 catalyst and the effect of pretreatment on the performance of CeO2–Co3O4 for CO oxidation were investigated in detail. The results show that the presence of CeO2 can increase its surface area, reduce the crystal size of Co3O4, and improve obviously the catalytic activity and stability of Co3O4 for CO oxidation, such as its T100 is only −60 °C. It was also found that the addition of CeO2 can not only promote the adsorption of O2 and the reaction of adsorbed CO with surface oxygen species to form CO2, but also increase the CO2 desorption speed. The pretreatment method can affect the catalytic activity of CeO2–Co3O4, the catalyst treated in N2 exhibits higher catalytic activity for low-temperature CO oxidation due to formation of oxygen vacancy. The catalyst reduced in H2 shows lower activity for CO oxidation although it has more surface oxygen vacancies, because of the difficult desorption of CO2 on the reduced CeO2–Co3O4 catalyst.
Co-reporter:Hui-Ying Li, Hai-Feng Wang, Yang-Long Guo, Guan-Zhong Lu and P. Hu
Chemical Communications 2011 - vol. 47(Issue 21) pp:NaN6107-6107
Publication Date(Web):2011/04/26
DOI:10.1039/C1CC11226K
Using first principles calculations for O vacancy diffusion on CeO2(111), we locate a surface diffusion mechanism, the two-step O vacancy exchange one, which is more favored than the most common hopping mechanism. By analyzing the results, we identify quantitatively the physical origin of why the two-step exchange mechanism is preferred.
Co-reporter:Jie Zhang, Xue-Qing Gong and Guanzhong Lu
Physical Chemistry Chemical Physics 2014 - vol. 16(Issue 32) pp:NaN16908-16908
Publication Date(Web):2014/06/30
DOI:10.1039/C4CP02235A
NO adsorption, diffusion and reaction at reduced CeO2(110) were studied by density functional theory calculations. NO accommodated by O vacancies can readily diffuse via alternate NO2 formation and dissociation, facilitating N2O2 formation and subsequent reduction to N2. Rare earth ceria plays an important catalytic role in both static and dynamic ways by tuning the electron distribution in adsorbates and reacting molecules.
Co-reporter:Zhangping Shi, Shuangshuang Zhang, Xiuzhen Xiao, Dongsen Mao and Guanzhong Lu
Catalysis Science & Technology (2011-Present) 2016 - vol. 6(Issue 10) pp:NaN3467-3467
Publication Date(Web):2015/12/03
DOI:10.1039/C5CY01238D
Highly effective CuZn0.3MgxAlOy (x = 0–0.2) catalysts for the synthesis of chiral L-phenylalaninol derived from Cu-rich hydrotalcite-like precursors were prepared by a co-precipitation method with Na2CO3 as the precipitant, and their physicochemical and catalytic properties were characterized. The results show that the presence of Mg2+ ions can promote the formation of hydrotalcite-like (htl) precursors, and the Mg2+ content would affect the phase purity of the prepared htl precursors. The BET surface area, exposed copper surface area and amount of acid sites of the samples decreased with the increase in the molar ratio of Mg2+/Al3+. Also, the dense layered htl precursors are beneficial to the atomically uniform distribution of the corresponding metal oxides in the prepared catalysts, promoting the stronger interaction between Cu0 and Al2O3 after the catalysts were reduced (SMSI effect). The activity of the CuZn0.3MgxAlOy catalysts is greatly dependent on not only the metallic copper surface area, but also the SMSI effect and the acidity of the catalysts. When Mg2+/Al3+ = 0.1 (mol), a phase-pure htl precursor could be obtained, and after calcination, the prepared CZA-0.1 catalyst exhibited very excellent catalytic performance for the hydrogenation of L-phenylalanine methyl ester to chiral L-phenylalaninol. After 5 h of reaction at 110 °C and 4 MPa H2, 100% conversion of L-phenylalanine methyl ester and 91.1% yield of L-phenylalaninol with an ee value of ~100% were achieved. After recycling 13 times, the L-phenylalaninol selectivity of the CZA-0.1 catalyst only decreased by 7.2%.
Co-reporter:Yuexin Shen, Guanzhong Lu, Yun Guo and Yanqin Wang
Chemical Communications 2010 - vol. 46(Issue 44) pp:NaN8435-8435
Publication Date(Web):2010/10/11
DOI:10.1039/C0CC02776F
Pd–Cu–Clx/Al2O3 catalysts were prepared by a NH3 coordination-impregnation method and exhibited an excellent activity for low-temperature CO oxidation and 100% CO conversion was obtained at −30 °C for 400 ppm CO and 1000 ppm H2O/air.
Co-reporter:Xin-Ping Wu, Xue-Qing Gong and Guanzhong Lu
Physical Chemistry Chemical Physics 2015 - vol. 17(Issue 5) pp:NaN3549-3549
Publication Date(Web):2014/12/17
DOI:10.1039/C4CP04766D
Diffusion processes and reactions of H at stoichiometric and reduced CeO2(111) surfaces have been studied by using density functional theory calculations corrected by on-site Coulomb interactions (DFT + U). Oxygen vacancies on the surface are determined to be able to significantly affect the behavior of H by modifying the charge of surface lattice O through the occurrence of Ce3+. It has been found that, at the reduced CeO2(111) surface, the adsorption strength of H as well as the H coupling barrier can be dramatically reduced compared to those at the stoichiometric surface, while H2O formation barrier is not significantly affected. Moreover, the diffusion of H at the reduced surface or into the bulk can occur more readily than that at stoichiometric CeO2(111).
Co-reporter:Yang Lou, Xiao-Ming Cao, Jinggang Lan, Li Wang, Qiguang Dai, Yun Guo, Jian Ma, Zhenyang Zhao, Yanglong Guo, P. Hu and Guanzhong Lu
Chemical Communications 2014 - vol. 50(Issue 52) pp:NaN6838-6838
Publication Date(Web):2014/03/20
DOI:10.1039/C4CC00036F
Highly efficient In2O3–Co3O4 catalysts were prepared for ultralow-temperature CO oxidation by simultaneously tuning the CO adsorption strength and oxygen activation over a Co3O4 surface, which could completely convert CO to CO2 at temperatures as low as −105 °C compared to −40 °C over pure Co3O4, with enhanced stability.
Co-reporter:Xuexun Du, Hui-Ying Li, Jun Yu, Xiuzhen Xiao, Zhangping Shi, Dongsen Mao and Guanzhong Lu
Catalysis Science & Technology (2011-Present) 2015 - vol. 5(Issue 8) pp:NaN3979-3979
Publication Date(Web):2015/06/02
DOI:10.1039/C5CY00545K
The Pd–Cu–Clx/Al2O3 catalysts (PCC) were prepared by a two-step impregnation (TI) method in organic solvent, wet impregnation (WI) method and NH3 coordination-impregnation (CI) method. The PCC-TI catalyst prepared by the two-step impregnation method (TI) exhibited much higher activity and stability for CO oxidation than the other catalysts, resulting from the smaller size of Cu2Cl(OH)3 and fewer carbonates deposited on the surface of PCC-TI catalyst. Using the PCC-TI catalyst, the complete conversion temperature of CO was 10 °C in the presence of 3.1% H2O. Among the three catalysts, the activation energy (Ea) of PCC-TI/ethanol was the lowest (27.1 kJ mol−1). The PCC-TI/ethanol prepared in ethanol solvent showed a higher activity compared with PCC-TI/methanol, due to much stronger interactions between the copper and palladium species. High concentrations of moisture and CO had a negative effect on the CO conversion. The former is due to excessive numbers of –OH groups (from H2O dissociation) which occupy the active sites of Pd and Cu, though –OH groups can work as part of the catalytic cycle, and the latter may originate from competitive adsorption and the presence of carbonates on the surface. We used DFT calculations to study the adsorption of H2O and CO on the surface, and the catalytic cycle of CO oxidation on the Pd species, revealing the possible routes for the formation of common species observed in the in situ DRIFTS spectra.
Co-reporter:Yuexin Shen, Yun Guo, Li Wang, Yanqin Wang, Yanglong Guo, Xueqing Gong and Guanzhong Lu
Catalysis Science & Technology (2011-Present) 2011 - vol. 1(Issue 7) pp:NaN1207-1207
Publication Date(Web):2011/08/16
DOI:10.1039/C1CY00146A
The catalytic stability of a Pd–Cu–Clx/Al2O3 catalyst for low temperature CO oxidation was investigated in different conditions. Under ∼0.1% moisture, the CO conversion over the Pd–Cu–Clx/Al2O3 catalyst can be maintained at 100% for 30 h even at 0 °C, but it deactivated reversibly at 25 °C with ∼0.6% moisture and irreversibly deactivated at 25 °C with ∼3.1% moisture or 0 °C with ∼0.6% moisture. The reversible deactivation is resulted from physical capillary condensation in the small pores of the catalysts. The irreversible deactivation is due to a breakage of the close-knit structure of Pd–Cu–Cl leading to an aggregation or transformation of the active copper phase, and the formation of a carbonate species on the catalyst surface, meaning that the inactive Pd0 species over the surface of the Pd–Cu–Clx/Al2O3 catalyst is hard to re-oxidize back to the active Pd+ sites by copper species in the high moisture reaction conditions.
Co-reporter:Shimei Ma, Guanzhong Lu, Yuexin Shen, Yun Guo, Yanqin Wang and Yanglong Guo
Catalysis Science & Technology (2011-Present) 2011 - vol. 1(Issue 4) pp:NaN674-674
Publication Date(Web):2011/05/23
DOI:10.1039/C1CY00049G
Cu1Ce8Fex–O catalysts for low temperature CO oxidation were prepared by an improved citrate sol–gel method with incorporation of thermal treatment under N2, and characterized by the nitrogen adsorption–desorption, XRD, CO pulse experiments, CO-TPR and CO-TPD. When x = 1, the Cu1Ce8Fe1–O catalyst shows higher catalytic activity for CO oxidation, and the reaction temperature for 90% CO conversion (T90) is only 50 °C. The presence of Fe in Cu1Ce8Fe1–O can improve the catalytic activity for CO oxidation, which results from its higher surface area, smaller crystalline size, higher activity and larger amounts of surface oxygen species.
Co-reporter:Chunyou Gao, Xiuzheng Xiao, Dongsen Mao and Guanzhong Lu
Catalysis Science & Technology (2011-Present) 2013 - vol. 3(Issue 4) pp:NaN1062-1062
Publication Date(Web):2012/12/12
DOI:10.1039/C2CY20763J
The Cu/ZnO/Al2O3 catalyst for hydrogenation of L-phenylalaninate to L-phenylalaninol was prepared by a co-precipitation method, and characterized by XRD, low-temperature N2 adsorption, H2-TPR, N2O chemisorption and ICP-AES. The results show that the physicochemical properties of the catalyst are greatly affected by the ZnO amount, and that the exposed copper surface area, dispersion of CuO and BET surface area of the Cu/ZnO/Al2O3 catalyst (Cu/Zn/Al = 1.0:0.3:1.0) reach the largest. The chemoselectivity of L-phenylalaninol is changed with ZnO amount in the Cu/ZnO/Al2O3 catalyst, and when Cu/Zn/Al = 1.0:0.3:1.0, the catalyst exhibits higher catalytic performance and chemoselectivity to L-phenylalaninol. Furthermore, the effect of temperature, pressure, reaction time and the molar ratio of catalyst to ester on the catalytic hydrogenation of L-phenylalaninate were investigated. When the catalytic hydrogenation of L-phenylalaninate was operated at 110 °C and 4 MPa of H2 for 5 h, the yield of L-phenylalaninol can reach 69.2 %, and its ee selectivity is 99.84 %.
Co-reporter:Cun Wen, Yi Liu, Yun Guo, Yanqin Wang and Guanzhong Lu
Chemical Communications 2010 - vol. 46(Issue 6) pp:NaN882-882
Publication Date(Web):2010/01/05
DOI:10.1039/B920725B
Hydrogen can be produced over Er2O3 in methane oxidation (oxygen/methane = 26). The reactivity of lattice oxygen in the catalyst plays a main role in the conversion of surface hydroxyl species to hydrogen or water. Adding a rare earth element into a catalyst can reduce the reactivity of lattice oxygen, resulting in increased hydrogen production, to eliminate catalyst hot-spots.
Co-reporter:Wenjie Xu, Haifeng Wang, Xiaohui Liu, Jiawen Ren, Yanqin Wang and Guanzhong Lu
Chemical Communications 2011 - vol. 47(Issue 13) pp:NaN3926-3926
Publication Date(Web):2011/02/23
DOI:10.1039/C0CC05775D
A new strategy was developed for the direct conversion of furfural to 1,5-pentanediol by the hydrogenolysis of the furan ring under mild conditions based on Pt/Co2AlO4 catalyst. This is the first report of the direct catalytic conversion of furfural to 1,5-pentanediol with high yield.
Co-reporter:Jie Li, Guanzhong Lu, Guisheng Wu, Dongsen Mao, Yanglong Guo, Yanqin Wang and Yun Guo
Catalysis Science & Technology (2011-Present) 2014 - vol. 4(Issue 5) pp:NaN1275-1275
Publication Date(Web):2014/01/22
DOI:10.1039/C3CY01004J
Co3O4 catalysts supported on TiO2 with different crystalline structures (anatase (A), rutile (R) and P25 (Degussa)) were prepared by a deposition–precipitation method, and characterized by nitrogen adsorption/desorption, XRD, HR-TEM, EPR, Raman spectroscopy, XPS and H2-TPR techniques. The results show that Co3O4/TiO2 (A) exhibited the highest activity among the three Co3O4/TiO2 catalysts: CO can be completely oxidized to CO2 at −43 °C. When rutile TiO2 or P25 were used as the support, its catalytic activity was decreased obviously, because the TiO2 crystal structure has an influence on the physicochemical and catalytic properties of the Co3O4 catalysts. The results show that the Co3O4/TiO2 (A) catalyst contains Ti3+ species, which is in an unstable state and can affect the properties of Co3O4 by the interaction between the deposited Co3O4 and anatase TiO2 support. The Co3O4/TiO2 (A) catalyst exhibits highly defective structure and good oxygen adsorption ability. The reducibility of Co3O4 is improved by the anatase TiO2 support, resulting in Co3O4/TiO2 (A) possessing the better redox property than the other Co3O4/TiO2 catalysts, which is an important factor for its high catalytic activity.
Co-reporter:Qingping Ke, Bingyan Zhang, Bolun Hu, Yangxin Jin and Guanzhong Lu
Chemical Communications 2015 - vol. 51(Issue 6) pp:NaN1015-1015
Publication Date(Web):2014/11/27
DOI:10.1039/C4CC09260K
A new strategy for the synthesis of epoxides is presented. This process allows the direct synthesis of epoxides from alkenes and aldehydes through C–H functionalization and C–C/C–O bond formation.
Co-reporter:Fendy Chen, Di Liu, Jie Zhang, P. Hu, Xue-Qing Gong and Guanzhong Lu
Physical Chemistry Chemical Physics 2012 - vol. 14(Issue 48) pp:NaN16580-16580
Publication Date(Web):2012/07/13
DOI:10.1039/C2CP41281K
Density functional theory calculations corrected by on-site Coulomb interaction have been carried out to track down the lattice oxygen reactivity of CeO2(111) and (110) surfaces in direct oxidation of a single CO. The possible elementary steps in CO adsorption and subsequent reactions with lattice oxygen were systematically studied. From calculated energetics, we determined that the lattice oxygen of the (110) surface is more reactive than that of the (111) surface. By calculating the reaction pathways leading to different final products, we found that the formation of carbonate species is competitive to CO2 formation and desorption, and such an effect could be more significant at CeO2(110) compared to CeO2(111). More importantly, it has also been found that electron localization at the characteristic 4f orbital of Ce, directly determined by subtle structural relaxation, can give rise to a unique scenario of the overall reaction coordinates. These results may bring us one step ahead toward the comprehensive understanding of catalytic performance of CeO2-based materials.
Co-reporter:Yinli Liu, Huiying Li, Jun Yu, Dongsen Mao and Guanzhong Lu
Physical Chemistry Chemical Physics 2015 - vol. 17(Issue 41) pp:NaN27768-27768
Publication Date(Web):2015/09/21
DOI:10.1039/C5CP03394B
Density functional theory (DFT+U) was used to study the adsorption of Aux (x = 1–4) clusters on the defective CeO2(111) facet and CO adsorption on the corresponding Aux/CeO2−x catalyst, in this work Aux clusters are adsorbed onto the CeO2−x + superoxide/peroxide surface. When Au1 is supported on the CeO2(111) facet with an O vacancy, the strong electronegative Auδ− formed is not favorable for CO adsorption. When peroxide is adsorbed on the CeO2(111) facet with the O vacancy, Aux was oxidized, resulting in stable Aux adsorption on the defective ceria surface with peroxide, which promotes CO adsorption on the Aux/CeO2−x catalyst. With more Au atoms in supported Aux clusters, CO adsorption on this surface becomes stronger. During both the Au being supported on CeO2−x and CO being adsorbed on Aux/CeO2−x, CeO2 acts as an electron buffer that can store/release the electrons. These results provide a scientific understanding for the development of high-performance rare earth catalytic materials.
Co-reporter:Jie Li, Xiaofei Liu, Wangcheng Zhan, Yun Guo, Yanglong Guo and Guanzhong Lu
Catalysis Science & Technology (2011-Present) 2016 - vol. 6(Issue 3) pp:NaN907-907
Publication Date(Web):2015/11/09
DOI:10.1039/C5CY01571E
Ceria–zirconia solid solution is a very important material in three-way catalysts for automotive emission control. High oxygen storage capacity (OSC) and thermally stable Ce0.5Zr0.5O2 was prepared by a modified complexing–coprecipitation (CC) method, and its surface area reached 44 m2 g−1 after calcination at 1100 °C for 6 h. Based on the characterizations of its structural and physicochemical properties, it was found that Ce0.5Zr0.5O2 prepared by the CC method existed as the t′′-phase with rich oxygen defects and surface Ce3+ and has a larger BET surface area, uniform particle and pore sizes, and excellent bulk oxygen migration and redox abilities than samples prepared by other methods. After being calcined at 1100 °C for 6 h, its surface area, OSC (and OSCC, oxygen storage capacity complete) and catalytic activity for the oxidation of CO were still the best among three Ce0.5Zr0.5O2 solid solutions prepared by three methods whether it was used as the catalyst or as a support for a Pd catalyst, reflecting its good thermostability, although its particle and pore sizes were somewhat increased. This complexing–coprecipitation method can be used to prepare other high surface area and thermally stable inorganic materials.
Co-reporter:Chenhao Du, Yun Guo, Yanglong Guo, Xue-qing Gong and Guanzhong Lu
Journal of Materials Chemistry A 2015 - vol. 3(Issue 46) pp:NaN23239-23239
Publication Date(Web):2015/10/08
DOI:10.1039/C5TA05092H
Developing methods for the fabrication of active and thermally stable noble metal/metal oxide nanomaterials are very important for catalysis and material fields. Herein, we used a polymer-template synthesis approach to prepare hollow Pd–CeO2 nanocomposite spheres (NCSs) with Pd nanoparticles evenly distributed inside the CeO2 shell, in which the aggregation of Pd nanoparticles can be well inhibited with the help of the protection of CeO2 nanocrystallites even after being calcined at 700 °C. The Pd nanoparticles are partially buried in the CeO2 shell and the surface Pd species are highly ionic, which is caused by the electron exchange at the Pd–CeO2 interface during calcination. This hollow structure Pd–CeO2 nanocatalyst shows excellent catalytic activity and stability in the aqueous selective reduction of 4-nitrophenol and gaseous CO oxidation. For the selective reduction of 4-nitrophenol, the reaction rate of this h-Pd–CeO2 NCS catalyst compared to those of the supported Pd/CeO2 and physically mixed Pd + CeO2 catalysts is almost 14 times and 5 times faster, respectively. For the CO oxidation, the larger Pd–CeO2 interface in h-Pd–CeO2 NCSs could facilitate the reaction between the adsorbed CO and O2, thus showing better low temperature activity. This paper emphasizes the advantages of a core–shell hollow structure and provides a new way for obtaining novel functional nanocatalysts.
Co-reporter:Qiuling Luo, Guanzhong Lu, Shaodian Shen, Xiuzhen Xiao, Dongsen Mao and Yanqin Wan
Journal of Materials Chemistry A 2011 - vol. 21(Issue 43) pp:NaN17110-17110
Publication Date(Web):2011/09/07
DOI:10.1039/C1JM12601F
With hydrophobic properties and ordered layered structures, mono-n-dodecyloxy-phosphinyl-cerium (terbium) (MDPCT) organic–inorganic hybrid materials were synthesized using cerium nitrate, terbium nitrate and mono-n-dodecyl phosphate (MDP) surfactant with three functions, hydrophobic group and phosphorus precursor, and characterized by XRD, SEM, TEM, FTIR and PLS. The results show that the solvent affects the interlayer spacing, crystallization and luminescent intensity of the prepared MDPCT materials. MDPCT prepared in water exhibits a more ordered layered structure and a higher degree of crystallinity, as well as stronger luminescent intensity than that prepared in ethanol. Based on the excellent solubility in organic solvents, this MDPCT hybrid luminescent material will be a promising candidate for potential biomedical applications in fluorescent imaging and analysis.
Co-reporter:Haixiang Tao, Hong Yang, Yanhui Zhang, Jiawen Ren, Xiaohui Liu, Yanqin Wang and Guanzhong Lu
Journal of Materials Chemistry A 2013 - vol. 1(Issue 44) pp:NaN13827-13827
Publication Date(Web):2013/10/07
DOI:10.1039/C3TA12989F
The sole presence of relatively small micropores in zeolite catalysts strongly influences the mass transfer and catalytic conversion of bulky molecules. Herein, we report a novel synthesis route for the confined synthesis of hierarchical MFI zeolite microspheres with nanorod oriented-assembled structures for the first time via the hydrothermal crystallization of a carbon–silica composite monolith. The growth of such unique zeolite microspheres undergoes a reversed crystal-growth route. Crystallization started on the outer surface of the amorphous particles, then extended to the core and finally resulted in nanorod oriented-assembled structures, due to the confined-space effect of carbon in the carbon–silica monolith. The novel hierarchical zeolite microspheres (5–10 μm), including Silicalite-1, ZSM-5 and TS-1, composed of oriented-assembled nanorods (50–100 nm in width) are easy for separation and have inter-crystalline mesoporous networks between the nanorods; the latter are favourable for mass transfer. More importantly, the hierarchical zeolite microspheres Hier-ZSM-5 and Hier-TS-1 show much higher catalytic activities for bulky substrate conversion than the conventional ZSM-5 and TS-1, respectively. Thus, the novel hierarchical zeolite microspheres reported here show a great potential for industrial applications.
Co-reporter:Jie Fang, Yanglong Guo, Guanzhong Lu, Colin L. Raston and K. Swaminathan Iyer
Dalton Transactions 2011 - vol. 40(Issue 13) pp:NaN3124-3124
Publication Date(Web):2011/02/25
DOI:10.1039/C0DT01651A
Doped lanthanum phosphate nanocrystals are a class of fluorescent material of enormous interest, presenting an unusual dichotomy on the nanoscale. The quantum yields of these crystals drops significantly in the nanoscale when compared with the corresponding bulk yields. Herein we show that the suppression of their thermodynamically favored 1-D growth in the nanoscale results in an increase in the quantum yield. This is possible by inducing heterogeneous nucleation of the crystals on the surface of single walled carbon nanotubes.
Co-reporter:Yujie Xie, Yun Guo, Yanglong Guo, Li Wang, Wangcheng Zhan, Yunsong Wang, Xue-qing Gong and Guanzhong Lu
Catalysis Science & Technology (2011-Present) 2016 - vol. 6(Issue 23) pp:NaN8233-8233
Publication Date(Web):2016/10/17
DOI:10.1039/C6CY01663D
A La-modified MnOx catalyst was developed for the total oxidation of C3H8. The promotional role of La and the effect of the preparation method on the structural, physicochemical and catalytic properties of the La–MnOx catalyst were investigated. The results show that the presence of La in MnOx can remarkably improve the oxygen reactivity of MnOx and promotes the reduction properties of Mn species with the aid of a strong interaction between Mn and La. The preparation method obviously affected the crystal structure, lattice defects, surface phase composition, reduction properties and apparent morphology of the La0.4–MnOx catalyst. When the La0.4–MnOx (C-0.4) catalyst was prepared by using the co-precipitation method, it exhibited excellent catalytic performance, good thermal stability and enhanced H2O resistance to the title reation, because the C-0.4 sample possesses a higher atomic ratio of Mn4+/Mn3+ (2.03) and contains more absorbed oxygen species and high activity and mobility of lattice oxygen. In addition, the catalytic reaction mechanism of C3H8 oxidation was not changed by La doping but promoted the C3H8 adsorption on the catalyst surface, resulting in the acceleration of its rate-determining step to a large extent.
Co-reporter:Chenhao Du, Yun Guo, Yanglong Guo, Xue-Qing Gong and Guanzhong Lu
Journal of Materials Chemistry A 2017 - vol. 5(Issue 11) pp:NaN5611-5611
Publication Date(Web):2017/02/15
DOI:10.1039/C7TA00015D
We proposed a hard-templated and electrostatic attraction induced deposition method to prepare a hollow core–shell Au@CeO2–ZrO2 nanocatalyst with a high surface area, in which a 6–8 nm ultrathin layer composed of CeO2–ZrO2 nanocrystals is embedded with individual Au nanoparticles, forming a sub-10 nm core–shell-like structure. In this hollow core–shell nanocatalyst, the mobility and growth of Au nanoparticles can be well inhibited even at 700 °C. For two model reactions of the selective reduction of 4-nitrophenol and CO oxidation, this Au@CeO2–ZrO2 nanocatalyst shows good catalytic activity and stability, compared with Au/CeO2–ZrO2 prepared by the deposition–precipitation (DP) method. For the CO oxidation, the activity of Au@CeO2–ZrO2 can be well maintained after calcination at 700 °C, while negligible CO conversion is observed over DP-Au/CeO2–ZrO2. Further research shows that the improved catalytic performance of this hollow core–shell nanocatalyst can be attributed to the nanoscale core–shell structure, which effectively inhibits the migration and growth of the Au NPs, and maximizes the interface between the Au NPs and the CeO2–ZrO2.
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