Co-reporter:Zhihong Fan, Heqin Guo, Kegong Fang and Yuhan Sun
RSC Advances 2015 vol. 5(Issue 31) pp:24795-24802
Publication Date(Web):03 Mar 2015
DOI:10.1039/C4RA16727A
A series of V2O5/TiO2 composite catalysts (V2O5–TiO2–Al2O3, V2O5–TiO2–SiO2, V2O5–TiO2–Ce2O3 and V2O5–TiO2–ZrO2) were prepared by an improved rapid sol–gel method and the catalytic behavior for dimethoxymethane (DMM) synthesized from methanol selective oxidation was investigated. The physicochemical properties of catalysts were characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller isotherms (BET), X-ray photoelectron spectroscopy (XPS), hydrogen temperature-programmed reduction (H2-TPR), NH3 temperature programmed desorption (NH3-TPD), infrared spectroscopy of adsorbed pyridine (Py-IR) and transmission electron microscopy (TEM) techniques. The best catalytic performance was obtained on a V2O5–TiO2–SiO2 catalyst with methanol conversion of 51% and DMM selectivity of 99% at 413 K. Furthermore, the V2O5–TiO2–SiO2 catalyst displayed an excellent catalytic stability within 240 h. Results showed that more Brønsted acidic sites were critical to increasing the DMM yield. The activity of V2O5/TiO2 composite catalysts decreased with increasing Brønsted acidity, but the yield of DMM increased with an increasing amount of Brønsted acidic sites. The excellent performance of the V2O5–TiO2–SiO2 catalyst might come from its optimal acidity and redox properties, higher active surface oxygen species, together with more Brønsted acid sites.
Co-reporter:Haijun Zhao, Minggui Lin, Kegong Fang, Juan Zhou, Ziyu Liu, Gaofeng Zeng and Yuhan Sun
RSC Advances 2015 vol. 5(Issue 83) pp:67630-67637
Publication Date(Web):28 Jul 2015
DOI:10.1039/C5RA13555A
A novel catalyst comprised of Cu–Mn mixed oxides and CaO–ZrO2 solid base has contributed to a high-performance methyl formate (MF) synthesis from syngas in a slurry reactor. Cu–Mn mixed oxides and mesoporous CaO–ZrO2 solid base were prepared by complexing method and alcohothermal route, respectively, and they were characterized by N2 isotherm adsorption–desorption, XRD, SEM, TEM, XPS and CO2-TPD techniques. Under the optimum reaction conditions of 160 °C, 3 MPa, 3:7 for the ratio of methanol to N,N-dimethylformamide, 40 g L−1 Cu–Mn sample, and 30 g L−1 CaO–ZrO2 sample, a low CO conversion of 22.4% was obtained over Cu–Mn/Ca–Zr, whereas the MF selectivity of 82.3% was higher than that of the traditional catalyst (e.g. Cu-catalyst and NaOCH3), which was due to the synergism between Cu–Mn and CaO–ZrO2 samples.
Co-reporter:Gang Wang, Li-tao Jia, Bo Hou, De-bao Li, Jun-gang Wang, Yu-han Sun
New Carbon Materials 2015 Volume 30(Issue 1) pp:30-40
Publication Date(Web):February 2015
DOI:10.1016/S1872-5805(15)60173-1
Fabricating self-supporting, three dimensional graphene macroscopic structures from two dimensional graphene sheets by self-assembly has been an intriguing subject in exploring the performance of graphene structures for practical advanced applications. Monolithic graphene hydrogels (GHs) with quite good mechanical properties and excellent resilience were self-assembled from graphene oxide (GO) dispersions under hydrothermal conditions by changing the pH value. The structure-property relationships and the self-assembly behavior of GHs were investigated. It was found that the formation of GHs was pH-dependent. The charge state of carboxyl groups on the graphene was the key factor that influenced the balance of attraction and repulsion interactions of the GO and consequently determined the self-assembly behavior. Both the graphene molecular structure and colloidal interactions were correlated with the unique self-assembly behavior, which can be used to design graphene arrangements with various structures, functions and mechanical properties. This method is superior to the conventional method that adjusts the concentration and reduction time of the GO dispersion.
Co-reporter:Haijuan Zhan, Feng Li, Peng Gao, Ning Zhao, Fukui Xiao, Wei Wei, Liangshu Zhong, Yuhan Sun
Journal of Power Sources 2014 Volume 251() pp:113-121
Publication Date(Web):1 April 2014
DOI:10.1016/j.jpowsour.2013.11.037
•La2CuO4 perovskite catalysts are prepared and tested.•The promoter Y, Ce, Mg, Zr can improve the performance of perovskite catalysts.•The perovskite catalysts show high selectivity for methanol.•The conversion of CO2 depends on the surface area of metallic Cu.A series of La–M–Cu–Zn–O (M = Y, Ce, Mg, Zr) based perovskite-type catalysts are prepared by sol–gel method and characterized by XRD, BET, TPR, N2O-adsorption, XPS and TPD techniques. The results indicate that all the catalysts exhibit La2CuO4 perovskite structure. The addition of Ce, Mg and Zr lead to smaller particles, lower reduction temperature, higher Cu dispersion, larger amount of hydrogen desorption at low temperature and more amount of basic sites. However, Y has less affects on the physicochemical properties. The catalysts derived from perovskite-type precursors show high selectivity for methanol, which is correlated with the Cuα+ species that exists in the reduced catalysts. More exposed Cu surface area is favorable for high CO2 conversion.
Co-reporter:Changcheng Liu;Minggui Lin;Dong Jiang;Kegong Fang
Catalysis Letters 2014 Volume 144( Issue 4) pp:567-573
Publication Date(Web):2014 April
DOI:10.1007/s10562-013-1163-7
K, Mg, and Ca modified nanowire molybdenum carbide have been prepared using an organic–inorganic hybrid method for the production of higher alcohols and hydrocarbons from the hydrogenation of CO. The results revealed that unpromoted molybdenum carbide mainly produced light alkanes, and only few alcohols were obtained. The promoters improved selectivity shift from alkane to alcohols in the sequence: K > Mg > Ca. Additional, the CO conversion was reduced with the addition of K and Mg, with K exhibiting more vigorous effect, but that remarkably increased for Mg. Moreover, the promoters showed different effectiveness on the ability of chain propagation. Potassium mainly enhanced the ability of alcohol chain propagation with higher selectivity to C2+OH, but had little effect on that of alkane. While, for magnesium and calcium, they mainly improved the ability of alkanes chain propagation with reducing the formation of methane.
Co-reporter:Yifei Yang, Litao Jia, Bo Hou, Debao Li, Jungang Wang, and Yuhan Sun
The Journal of Physical Chemistry C 2014 Volume 118(Issue 1) pp:268-277
Publication Date(Web):December 9, 2013
DOI:10.1021/jp408174w
The interfacial interaction between active species and supports is of significance for the catalytic performance of heterogeneous catalysts. Accordingly, the N-doped mesoporous carbon (NMC) was employed to support cobalt nanoparticles for insight into the nature of interfacial interaction and the reactivity of Fischer–Tropsch synthesis (FTS). Through a series of characterization techniques, it is found that the nitrogen incorporated into the carbonaceous framework, especially the sp2-type nitrogen, eventually functions as heterogeneous sites for the nucleation and growth of cobalt species. Owing to the unique structure of NMC supports, a pronounced electron transfer from the NMC supports to cobalt oxide particles takes place at the interface. The solid-state interfacial interaction significantly affects the dispersion and reduction behavior of cobalt species on the NMC substrates, resulting in the shift of the reduction peak of small particles toward high temperature, which ultimately shapes an unusual catalytic feature in the FTS. The cobalt-specific activity experiences the transition from the increasing stage to the decreasing stage and the turnover frequency increases first and then levels off with the increase in particle size. The product selectivity is also found to shift toward light hydrocarbon for the NMC supported small cobalt particles.
Co-reporter:Yifei Yang;Litao Jia;Bo Hou;Debao Li;Jungang Wang
Catalysis Letters 2014 Volume 144( Issue 1) pp:133-141
Publication Date(Web):2014 January
DOI:10.1007/s10562-013-1124-1
Highly dispersed cobalt nanoparticles were incorporated into the ordered mesoporous carbon (OMC) via the ultrasonically assisted vacuum-pressure impregnation (UAVI) for CO hydrogenation. The as-synthesized samples were subjected to the characterization of N2 physisorption, HAADF-STEM, XRD, XPS, magnetic measurement, H2 chemisorption and 59Co zero field spin-echo NMR. It is found that the cobalt particles are exclusively distributed into the channels of OMC and the rigid frameworks significantly bridle the growth of active species to obtain ultrafine cobalt particles with size less than 4 nm. The highly dispersed cobalt nanoparticles perform superior catalytic performances during the CO hydrogenation as compared to the catalyst prepared by the conventional impregnation. The observed stability of novel catalysts outperforms the conventional one during the 96 h evaluation on stream due to the confinement effect to the sintering and conglomeration of active species. On the other hand, a typical structural sensitivity is also observed for the highly dispersed catalysts and the coordinative-unsaturated disordered stacking of cobalt atoms renders higher efficiency to improve CO turnover frequency. Besides, a high selectivity to mixed alcohols is also obtained for the highly dispersed catalysts and the yields of methane and methanol decrease gradually with increasing the particle size. Unfortunately, the highly dispersed particles also display a relatively high selectivity to CO2.
Co-reporter:Changzhen Wang, Nannan Sun, Min Kang, Xia Wen, Ning Zhao, Fukui Xiao, Wei Wei, Tiejun Zhao and Yuhan Sun
Catalysis Science & Technology 2013 vol. 3(Issue 9) pp:2435-2443
Publication Date(Web):11 Jun 2013
DOI:10.1039/C3CY00153A
A mesoporous Ni–CaO–ZrO2 catalyst which showed an excellent performance in the dry reforming of CH4 was thoroughly characterized by using a series of methods including N2 physical adsorption, temperature-programmed reduction (TPR), H2/CO chemisorptions, and so forth. Particularly, samples after different treatments such as calcination, reduction and different periods of reaction were subjected to X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis, by which changes in the phase structure and surface chemistry were followed. The results suggested that metallic Ni was gradually oxidized during the reaction, and a non-stoichiometric Ni–carbon compound was slowly formed. This latter species has a role as an important intermediate (or even active phase). Kinetic studies were then carried out based on these findings, according to which a Langmuir–Hinshelwood model was developed. Both the experimental results and the kinetic analysis provided novel evidence for the bi-functional mechanism of dry reforming over ZrO2-based catalysts.
Co-reporter:Guang Zeng, Congbiao Chen, Debao Li, Bo Hou and Yuhan Sun
CrystEngComm 2013 vol. 15(Issue 18) pp:3521-3524
Publication Date(Web):13 Mar 2013
DOI:10.1039/C3CE40142A
This communication provides an insight into the exposure of (001) and (011) planes in MFI zeolite and the objective of controlling MFI crystal shapes between the coffin and octagonal shapes is achieved by adjusting the amount of template TPAOH in MFI synthesis.
Co-reporter:Heqin Guo, CongbiaoChen, Yong Xiao, Jungang Wang, Zhihong Fan, Debao Li, Yuhan Sun
Fuel Processing Technology 2013 Volume 106() pp:77-83
Publication Date(Web):February 2013
DOI:10.1016/j.fuproc.2012.07.004
Two types of sulfated vanadia–titania catalysts, VTS and SVT, were prepared by the rapid combustion method and the impregnation method, respectively. The physicochemical properties of the catalysts were characterized by SEM, XRD, Raman, BET, XPS, ICP-OES, H2-TPR-MS and NH3-TPD techniques. The catalytic activities were evaluated to the partial oxidation of methanol to dimethoxymethane (DMM). The results showed that the VTS catalyst consisted of nano-particles and exhibited pore structure. While, the morphology of the SVT catalyst was coarse and irregularly shaped. Moreover, both vanadia and sulfate were highly dispersed on VTS catalyst, while aggregated on SVT catalyst. And the highly dispersed vanadia and sulfate species increased reducibility and acidic sites. As a result, VTS catalyst presented higher methanol conversion and DMM selectivity than SVT catalyst, which was clearly related to the physicochemical state of vanadia and both acidic and redox properties of the catalyst.Highlights► Preparation method influenced the physical-chemical properties of the catalysts. ► The catalytic performance was related to the redox and acidity of the catalysts. ► The VTS has stronger reducibility, more acidic sites and higher DMM selectivity.
Co-reporter:Min Kang, Jun Zhang, Changzhen Wang, Feng Wang, Ning Zhao, Fukui Xiao, Wei Wei and Yuhan Sun
RSC Advances 2013 vol. 3(Issue 41) pp:18878-18885
Publication Date(Web):07 Aug 2013
DOI:10.1039/C3RA43742F
Thermochemical CO2 splitting was carried out over Ni-, Fe-, Mg- and Mn-doped ceria/zirconia solid solutions, where the sample was thermally reduced at 1400 °C under inert atmosphere followed by the re-oxidization of CO2 to generate CO at 1100 °C in the subsequent step. Compared with the undoped sample, all the doped ceria/zirconia had a high reduction yield in the first thermal reduction step. Due to the low thermal stability, Ni-, Fe- and Mn-doped samples showed lower CO production in the CO2 splitting step than the stoichiometric amounts. In contrast, the Mg-doped sample produced more CO with the volumes of 5.64 and 5.17 mL g−1 during the two thermochemical cycles. Moreover, a 10% Mg-doped sample prepared via hydrothermal treatment with P123 showed a more stable reactivity during cycling due to the relatively stable microstructure under the successive high temperature thermal treatment.
Co-reporter:Lei Li, Bingsheng Zhang, Feng Wang, Ning Zhao, Fukui Xiao, Wei Wei, and Yuhan Sun
Energy & Fuels 2013 Volume 27(Issue 9) pp:5388-5396
Publication Date(Web):August 19, 2013
DOI:10.1021/ef4010412
A novel sorbent, MgO/Al2O3-supported K2CO3, for CO2 sorption was prepared. It was found that the sorbent prepared by the multi-impregnation method showed a large CO2 capture capacity at low temperature under simulated flue gases with MgO loading of 10 and 20 wt % (KMgAlI3010 and KMgAlI3020). The presence of water vapor pretreatment and MgO loadings had different effects on the CO2 adsorption mechanisms. For the KMgAlI3010 sorbent, the main phase was KHCO3 after CO2 adsorption. While for the KMgAlI3020 sorbent, when pretreated with less steam, the main phase was Mg2Al2(CO3)4(OH)2·15H2O after CO2 adsorption. When pretreated with excess steam, however, the CO2 adsorption mechanism was similar to the KMgAlI3010 sorbent. Furthermore, the as-prepared KMgAl sorbents were stable even after 30 adsorption/desorption cycles.
Co-reporter:Hong-Mei Wei, Feng Wang, Jun-Liang Zhang, Bo Liao, Ning Zhao, Fu-kui Xiao, Wei Wei, and Yu-Han Sun
Industrial & Engineering Chemistry Research 2013 Volume 52(Issue 33) pp:11463-11478
Publication Date(Web):March 28, 2013
DOI:10.1021/ie3034976
Separation of dimethyl carbonate/methanol azeotropic mixture by using distillation process has been a hot-point in the study of the synthesis process of dimethyl carbonate by urea methanolysis method. Most studies focus on the steady-state design, and only few papers have dealt with the dynamic performance and control of this binary azeotropic system. This paper explores the design and control of pressure-swing distillation systems for separation of dimethyl carbonate/methanol. The steady-state and dynamic simulations are carried out with Aspen Plus and Aspen Dynamics. Then, on the basis of the global economical analysis, an optimized separation configuration is proposed. The vital operating parameters and geometric parameters are determined according to the simulation and optimization results. Furthermore, two control strategies, CS1 and CS2, are proposed. With disturbance, the proposed basic control structure (CS1) can only maintains the quality specification of products from the bottom of the first column. However, the second control structure (CS2) succeeds in holding the bottom product purity for two distillation columns, even for large feed flow rate and large composition disturbances. Detailed analysis for CS1 and CS2 is made based on dynamic simulation which illustrates that the control structure CS2 outperforms CS1 to handle the disturbances.
Co-reporter:Lei Li, Ning Zhao, Wei Wei, Yuhan Sun
Fuel 2013 Volume 108() pp:112-130
Publication Date(Web):June 2013
DOI:10.1016/j.fuel.2011.08.022
This article reviews the progress made in CO2 capture, storage, and utilization in Chinese Academy of Sciences (CAS). New concepts such as adsorption using dry regenerable solid sorbents as well as functional ionic liquids (ILs) for CO2 capture are thoroughly discussed. Carbon sequestration, such as geological sequestration, mineral carbonation and ocean storage are also covered. The utilization of CO2 as a raw material in the synthesis of chemicals and liquid energy carriers which offers a way to mitigate the increasing CO2 buildup is introduced.Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Progress on CO2 capture, storage, and utilization (CCSU) in Chinese Academy of Sciences (CAS) were reviewed. ► The main advantages and disadvantages of the CCSU process were discussed. ► The further research directions of CCSU were proposed.
Co-reporter:Yong Li;Xia Wen;Lei Li;Feng Wang;Ning Zhao
Journal of Sol-Gel Science and Technology 2013 Volume 66( Issue 3) pp:353-362
Publication Date(Web):2013 June
DOI:10.1007/s10971-013-3017-6
A one-pot template-free route was developed for the synthesis of novel tetraethylenepentamine modified porous silica as CO2 adsorbents, the obtained materials were characterized by N2 adsorption/desorption, thermogravimetry, elemental analysis, Fourier transform infrared spectrometry,scanning electron microscopy and transmission electron microscopy. It was found that the amine species were inserted into the silica skeleton, which considerably enhanced their dispersion. Compared with similar materials derived from impregnation, the porous structure of the silica can be better reserved, leading to a promising CO2 adsorption capacity of 3.98 mmol CO2/g-adsorbent and a fast adsorption kinetic in simulated flue gas at 348 K. The resulted adsorbents could also be easily regenerated and showed a good durability in multiple adsorption–desorption cycles. All these features make this method a promising option for the preparation of CO2 adsorbents.
Co-reporter:Peng Gao, Feng Li, Fukui Xiao, Ning Zhao, Nannan Sun, Wei Wei, Liangshu Zhong and Yuhan Sun
Catalysis Science & Technology 2012 vol. 2(Issue 7) pp:1447-1454
Publication Date(Web):20 Mar 2012
DOI:10.1039/C2CY00481J
A series of Cu/Zn/Al/Zr catalysts were synthesized by calcination of hydrotalcite-containing precursors with different Cu2+/Zn2+ atomic ratios (n). Two other catalysts (n = 2) were also prepared via phase-pure hydrotalcite-like and conventional rosasite precursors for comparison. XRD and UV-Vis-NIR DRS characterizations demonstrate that most Cu2+ of hydrotalcite-containing materials did not enter the layer structure. The Cu dispersion of the catalysts decreases with the increase of Cu content, while both the exposed Cu surface area and the Cu+ and Cu0 content on the reduced surface reach a maximum when n is 2. The catalytic performance for the methanol synthesis from CO2 hydrogenation was also tested. The catalytic activity and selectivity of the catalysts (n = 0.5–4) via hydrotalcite-containing precursors rise first and then decrease with increasing Cu2+/Zn2+ ratios, and the optimum performance is obtained over the catalyst with Cu2+/Zn2+ = 2. Moreover, the Cu/Zn/Al/Zr catalyst (n = 2) via hydrotalcite-containing precursor exhibits the best catalytic performance, which is mainly due to the maximum content of active species compared with another two catalysts derived from different precursors.
Co-reporter:Zhong Liu, Baoliang Lv, Dong Wu, Yan Zhu and Yuhan Sun
CrystEngComm 2012 vol. 14(Issue 11) pp:4074-4080
Publication Date(Web):14 Mar 2012
DOI:10.1039/C2CE06683A
In the present work, a significant advance has been made in precisely tailoring dendritic α-Fe2O3 structures along [100] and/or its equivalent directions. We proposed that the benzoate anions adsorb on (100) and/or its equivalent facets, leading to the slow growth of these facets. By carefully controlling the experimental conditions, the dendritic structures can be gradually tailored to nanorods and finally to dodecahedral α-Fe2O3 nanoparticles with twelve exposed (012) planes. Interestingly, with the process proceeding, the coercivity (Hc) of these particles decreases successively due to the reduction in magnetic anisotropy by lessening intensity of hierarchical hyperbranched structure. The tailoring process gives us an in-depth understanding of the formation mechanism of dendritic α-Fe2O3 structures, which is not possibly achieved by the traditional time-dependent method.
Co-reporter:Gang Wang, Li-Tao Jia, Yan Zhu, Bo Hou, De-Bao Li and Yu-Han Sun
RSC Advances 2012 vol. 2(Issue 30) pp:11249-11252
Publication Date(Web):26 Sep 2012
DOI:10.1039/C2RA21348F
Nitrogen-doped graphene (N-G), in the form of a stable dispersion, a strong hydrogel and a macroporous aerogel, was synthesized by simultaneous nitrogen doping and reduction of graphene oxide with aqueous ammonia under mild conditions. The N content and thermal stability of the resultant samples proved to be high.
Co-reporter:Zhong Liu;Baoliang Lv;Dong Wu;Yao Xu
European Journal of Inorganic Chemistry 2012 Volume 2012( Issue 25) pp:4076-4081
Publication Date(Web):
DOI:10.1002/ejic.201200140
Abstract
Octadecahedral α-Fe2O3 nanoparticles were hydrothermally synthesized in the presence of formamide. These octadecahedral α-Fe2O3 nanoparticles have a threefold axis and are enclosed by twelve dominant {112} facets and six {104} facets. In comparison with the {104} facets, the sterically less hindered {112} facets induced the selective adsorption of formamide more easily, which resulted in the gradual increase in the amount of {112} facets by decreasing the amount of {104} facets with increasing formamide. The coercivity (Hc) of these octadecahedral particles increased successively as the aspect ratio (c/a) increased. The sensing capability of these particles toward H2O2 was investigated, and the response currents of the particles dominated by {112} facets showed a linear relationship with a concentration of H2O2 in the range from 40 μM to 6.66 mM in different stages.
Co-reporter:Yangyan Gao, Ning Zhao, Wei Wei, Yuhan Sun
Computational and Theoretical Chemistry 2012 Volume 992() pp:1-8
Publication Date(Web):15 July 2012
DOI:10.1016/j.comptc.2012.04.022
The mechanisms of urea decomposition into isocyanic acid (HNCO) and ammonia (NH3) in gas-phase and on the ZnO (101¯0) surface have been investigated by using density functional theory. In gas-phase, urea decomposes into HNCO and NH3 in one step, which is a concert reaction. However, on the ZnO (101¯0) surface urea is found to decompose gradually, in which urea molecule first adsorbs on the ZnO surface, followed by the NH and the NC bonds breaking, and eventually rebinds to form NH3 and HNCO. The presence of ZnO (101¯0) surface decreases the energy barrier of urea decomposition. And as the intense interaction between the surface and urea, urea decomposition is exothermic by 48.0 kcal/mol on the surface, which is endothermic by 22.0 kcal/mol in the gas-phase.Graphical abstractHighlights► The adsorption of urea on the ZnO (101¯0) surface is investigated. ► In gas-phase urea decomposition is concerted, while on the surface it is stepwise. ► The ZnO (101¯0) surface effectively catalyzes urea decomposition reaction.
Co-reporter:Yifei Yang;Litao Jia;Yan Meng;Bo Hou;Debao Li
Catalysis Letters 2012 Volume 142( Issue 2) pp:195-204
Publication Date(Web):2012 February
DOI:10.1007/s10562-011-0747-3
Ordered mesoporous carbon supported cobalt-based catalysts (Co/MC) were synthesized via incipient wetness impregnation with different amounts of furfuryl alcohol (FA) as carbon precursor. The characterizations of obtained Co/MC were subjected to N2 adsorption, XRD, XPS, TEM, H2-TPR, H2-TPD and H2-TPSR. The results indicate that the reducibility and dispersion of Co active species vary significantly due to the difference of FA amount. By simply tuning the FA content from 25 to 100 wt%, the reduction temperature of deriving metallic Co shifts gradually to lower. The catalytic performance of Co/MC was evaluated for Fischer–Tropsch (FT) synthesis. The observed FT activity exhibits a volcano-type curve with the amount of FA due to the effect of both reducibility and dispersion of active species. As the precursor concentration overweighs 50 wt%, the ability of CO to dissociate over the active surface and the selectivity to the C5+ products level off after experiencing an initial increase. Substantially, the catalysts with higher concentration of FA render the larger crystallites having an average size of more than 6 nm, which facilitates the CO hydrogenation by way of carbon chain propagation. It seems that the sample with FA content of 50 wt% is optimum in terms of FT activity and C5+ selectivity.
Co-reporter:Yulong Lin, Yu Wei, Yuhan Sun, Jing Wang
Materials Research Bulletin 2012 47(3) pp: 614-618
Publication Date(Web):
DOI:10.1016/j.materresbull.2011.12.042
Co-reporter:Yulong Lin, Yu Wei, Yuhan Sun
Journal of Molecular Catalysis A: Chemical 2012 Volumes 353–354() pp:67-73
Publication Date(Web):February 2012
DOI:10.1016/j.molcata.2011.11.006
Lepidocrocite was synthesized by aerial oxidation using an FeIIEDTA solution. The synthesis was performed under irradiation from different monowavelength light emitting diode (LED) lamps at room temperature. X-ray diffraction results showed the formation of differently crystallized lepidocrocite. The indirect bandgap values of the lepidocrocite samples were about 2.34, 2.36, and 2.31 eV for red, green, and blue light, respectively. The kinetics of the photo-decolorization of crystal violet (CV) was investigated in a system composed of lepidocrocite, H2O2, and visible light. H2O2 concentration, light irradiation, and catalyst concentration were also investigated. The rate of CV decolorization was found to fit pseudo-first-order kinetics. The results show that different as-prepared lepidocrocite have different adsorption and photocatalytic characteristics. A possible mechanism was also suggested for the dye degradation.Graphical abstractLepidocrocite with different indirect bandgap values was synthesized by aerial oxidation FeIIEDTA solution under different monowavelength LED lamps irradiation at room temperature. Different photocatalytic activity was found in the decolorization of crystal violet dye.Highlights► Lepidocrocite was room-temperature synthesized by monowavelength LED irradiation. ► Different wavelength irradiation led to different Eg value of lepidocrocite. ► γ-FeOOH obtained by blue LED irradiation has the highest Γmax and catalytic activity. ► A mechanism was suggested for the degradation of crystal violet dye.
Co-reporter:Baoliang Lv, Yao Xu, Dong Wu and Yuhan Sun
Chemical Communications 2011 vol. 47(Issue 3) pp:967-969
Publication Date(Web):12 Nov 2010
DOI:10.1039/C0CC03632C
Single-crystal α-Fe2O3 hexagonal nanorings with hexagonal inner hole were synthesized under the stepwise influence of different anionic ligands (F− and SCN−). This is a new method to design and modify crystal structures of transition metal oxide nanoparticles.
Co-reporter:Baoliang Lv, Yao Xu, Dong Wu and Yuhan Sun
CrystEngComm 2011 vol. 13(Issue 24) pp:7293-7298
Publication Date(Web):10 Oct 2011
DOI:10.1039/C1CE05431G
α-Fe2O3
nanoparticles with various morphologies (including spindles, rods, tubes, disks and nanorings) were synthesized under the influence of H2PO4− ions via a simply hydrothermal method. It was found that the morphologies of the α-Fe2O3 nanoparticles were highly sensitive to the concentration of H2PO4− ions. The special all doubly coordinated surface hydroxyl configuration on (001) facets of α-Fe2O3 was the most important factor for the morphology evolution. The final morphologies of the samples mainly depend on how the H2PO4− anions oriented the growth of the (001) facet. All morphologies of the synthesized α-Fe2O3 nanoparticles could be systemically evaluated by the competition of Fe3+ and H2PO4− ions on the (001) facets.
Co-reporter:Zunyuan Xie, Feng Wang, Ning Zhao, Wei Wei, Yuhan Sun
Applied Surface Science 2011 Volume 257(Issue 8) pp:3596-3602
Publication Date(Web):1 February 2011
DOI:10.1016/j.apsusc.2010.11.085
Abstract
The hydrophobisation of commercial viscose-based activated carbon fiber (ACF) was obtained by grafting vinyltrimethoxysilane (vtmos) on the ACF surface, to improve ACF's adsorption selectivity towards carbon disulfide (CS2) under highly humid condition. The characterizations, including FTIR, 29Si NMR, adsorption/desorption of nitrogen, thermal analysis and elemental analysis, revealed that the vtmos was successfully grafted onto the ACF surface, even though the hydrophobisation caused a partial filling of the porosity along with a slight decrease in the surface area. The efficiency of the hydrophobisation modification was evaluated by both equilibrium and dynamic adsorption experiment of water vapor and CS2. The equilibrium adsorption results indicated that the hydrophobisation modifications accounted for a decrease of both the amounts of water and CS2 adsorbed by the hydrophobised ACF. However, dynamic adsorption found that the adsorption performance was improved under highly humid condition, evidencing that hydrophobisation improved the hydrophobicity of the ACF surface and enhanced the adsorption selectivity towards CS2.
Co-reporter:Lei Li, Yong Li, Xia Wen, Feng Wang, Ning Zhao, Fukui Xiao, Wei Wei, and Yuhan Sun
Energy & Fuels 2011 Volume 25(Issue 8) pp:3835
Publication Date(Web):July 6, 2011
DOI:10.1021/ef200499b
CO2 capture was carried out over dry K2CO3/MgO/Al2O3 sorbent in a fluidized-bed reactor. The result showed that the total CO2 adsorption capacity of the new sorbent reached 109.6 mg of CO2/g of sorbent in the bubbling regime at 60 °C. The X-ray diffraction (XRD) results revealed that there were several kinds of carbonates formed during CO2 adsorption, such as KHCO3, KAl(CO3)2(OH)2, K2Mg(CO3)2, K2Mg(CO3)2·4H2O, and MgCO3. The high concentration CO2 could be obtained by the multi-stage adsorption/desorption cycles. The sorbent could be completely regenerated at 480 °C, and the adsorption capacity remained unchanged after 6 cycles. Furthermore, the application of a conceptual CO2-capture process using this sorbent was proposed for an existing coal-fired power plant.
Co-reporter:Lihong Jia, Litao Jia, Debao Li, Bo Hou, Jungang Wang, Yuhan Sun
Journal of Solid State Chemistry 2011 Volume 184(Issue 3) pp:488-493
Publication Date(Web):March 2011
DOI:10.1016/j.jssc.2010.10.002
A series of silylated Co/SBA-15 catalysts were prepared via the reaction of surface Si–OH of SBA-15 with hexamethyldisilazane (HMDS) under anhydrous, vapor-phase conditions, and then characterized by FT-IR, N2 physisorption, TG, XRD, and TPR-MS. The results showed that organic modification led to a silylated SBA-15 surface composed of stable hydrophobic Si–(CH3)3 species even after calcinations and H2 reduction at 673 K. Furthermore, the hydrophobic surface strongly influenced both metal dispersion and reducibility. Compared with non-silylated Co/SBA, Co/S-SBA (impregnation after silylation) showed a high activity, due to the better cobalt reducibility on the hydrophobic support. However, S-Co/SBA (silylation after impregnation) had the lowest FT activity among all the catalysts, due to the lower cobalt reducibility along with the steric hindrance of grafted –Si(CH3)3 for the re-adsorption of α-olefins.Graphical abstractThe silylation of an SBA-15 before cobalt impregnation enhanced the reducibility of cobalt oxides on an SBA-15-supported cobalt catalyst and consequently increased the catalytic activity for Fischer–Tropsch synthesis.
Co-reporter:Tao Tang, Xiaoan Li, Yao Xu, Dong Wu, Yuhan Sun, Jun Xu, Feng Deng
Colloids and Surfaces B: Biointerfaces 2011 Volume 84(Issue 2) pp:571-578
Publication Date(Web):1 June 2011
DOI:10.1016/j.colsurfb.2011.02.019
To remove bilirubin from human plasma, amine/methyl bifunctionalized SBA-15 materials were directly synthesized from the co-condensation of 3-aminopropylmethyldiethoxysilane and tetraethoxysilane with an amphiphilic block copolymer P123 as template. XRD, N2 sorption analysis, FTIR and 29Si MAS NMR were used to identify their well-ordered mesostructure and the grafting of amine and methyl groups on the surface of as-synthesized materials. Both SEM and TEM indicated that the bifunctionalized SBA-15 possessed platelet morphology. This might be attributed to the charge repulsion brought by protonated amine groups and the diminution of hydroxyl groups on the end of silicate-micelles, which passivated the end-to-end anchoring of silicate-micelles along the longitudinal axis. Such a material was investigated as the adsorbent for selective bilirubin removal from human plasma, which showed a high bilirubin clearance of 51.4% within 1.5 h with a little amount of albumin adsorption. The results of hemolysis assay suggested that the bifunctionalized SBA-15 caused serious hemolysis of red blood cells. However, in practical application, plasma separation technique could avoid direct contact between the adsorbent and red blood cells. The further hemeolysis assay proved that the plasma after contacting with the bifunctionalized SBA-15 could not lead to the hemolysis of red blood cells. Thus, the bifunctionalized SBA-15 is expected to be a potential candidate as a clinical hemoperfusion material.Graphical abstractResearch highlights► Well-ordered bifunctional SBA-15 with platelet morphology was synthesized. ► The synthesized material showed high bilirubin clearance. ► The synthesized material exhibited high bilirubin adsorption selectivity. ► The synthesized material exhibited negligible hemolytic activity.
Co-reporter:Yangyan Gao, Weicai Peng, Ning Zhao, Wei Wei, Yuhan Sun
Journal of Molecular Catalysis A: Chemical 2011 Volume 351() pp:29-40
Publication Date(Web):December 2011
DOI:10.1016/j.molcata.2011.09.006
Using density functional theory, the reaction mechanism for dimethyl carbonate (DMC) synthesis from methyl carbamate (MC) and methanol (CH3OH) with and without catalysts is investigated. And to investigate solvent effects, the reactions are simulated in CH3OH solvent by using the conductor like solvent model (COSMO). In our calculation, the uncatalyzed MC methanolysis reaction is kinetically and thermodynamically unfavorable. However, it is obviously catalyzed by acid and base catalysts. By orbital energy calculation, MC methanolysis reaction is considered as the charge-controlled reaction. Thus, electrostatic potential fitted charges as reaction indicator is used to infer the activity of species after catalyst Zn(NH3)2(NCO)2 initiation. And it is confirmed to be successful in reactivity prediction. The catalytic cycles involved the selected active species are proposed. By calculating activation energies, the catalytically active species is considered to be Zn(NH3)2(NCO)(NHCOOCH3), which derives from the reaction of Zn(NH3)2(NCO)2 with CH3OH. The DMC synthesis from the catalytically active species and CH3OH is favored, of which the reaction activation energy is effectively decreased.Graphical abstract. ESP fitted charges as reaction indicator is successful in prediction reactivity of the active species.Highlights► The mechanism for MC methanolysis reaction is clearly presented. ► The base catalyst is in favor of MC methanolysis via facilitating CH3O− formation. ► The catalytically active specie is Zn(NH3)2(NCO)(NHCOOCH3). ► The ESP fitted charges is confirmed be to appropriate as the reactivity indicator.
Co-reporter:Nannan Sun, Xia Wen, Feng Wang, Wei Wei and Yuhan Sun
Energy & Environmental Science 2010 vol. 3(Issue 3) pp:366-369
Publication Date(Web):08 Feb 2010
DOI:10.1039/B925503F
Ni–CaO–ZrO2 catalysts with different pore structures were prepared and tested for CO2 reforming of methane. It was found that the catalyst with a mesoporous framework showed both high activity and stability. In particular, no deactivation was observed at a period of run on stream. The characterization confirmed that the “confine effect” of the mesoporous structure prevented Ni particles from sintering during reaction, and as a result, the catalyst with such a mesoporous framework showed a better catalytic performance and resistance to coking.
Co-reporter:Baoliang Lv;Zhenyu Liu;Hong Tian;Yao Xu;Dong Wu
Advanced Functional Materials 2010 Volume 20( Issue 22) pp:3987-3996
Publication Date(Web):
DOI:10.1002/adfm.201001021
Abstract
Despite significant advances in iron oxide nanoparticles, it is still a challenge to synthesize regular polyhedral single-crystalline α-Fe2O3 particles because the surface energies of several low-index planes are fairly similar. In the work presented here, well-dispersed and single-crystalline dodecahedral and octodecahedral α-Fe2O3 particles are synthesized by a facile hydrothermal method with the aid of F− anions. The crystalline structure of the polyhedral particles is disclosed by various characterization techniques. The dodecahedral particles are of hexagonal bipyramidal shape and enclosed by twelve equivalent (101) planes. The octodecahedral particles are formed by adding six equivalent (111) planes on the two tips of a dodecahedral particle, that is, they are enclosed by twelve (101) planes and six (111) planes. The existence of F− anions plays a crucial role in the control of polyhedral particle shape. The function of F− anions in the shape formation of the polyhedral particles is proposed as follows: 1) A high concentration of exposed Fe3+ cations induces preferential adsorption of F− anions on the (100) plane and leads to the slowest growth along the [100] direction. When the concentration of F− anions is higher than 24 mM, a stable speed ratio of growth along the [001] and [100] directions results in the exposure of (101) planes. 2) With a lower concentration of F− anions, six symmetrical (111) planes with low concentration of exposed Fe3+ cations are present at the tops of a dodecahedral particle to form an octodecahedron. Furthermore, the dodecahedral and octodecahedral α-Fe2O3 particles show much stronger magnetism than the previously reported α-Fe2O3 nanostructures, having coercivities of 4986 Oe and 6512 Oe, respectively. Such high coercivities are attributed to a large local magnetic anisotropy, which might be induced by the polyhedron with equivalent crystallographic planes and/or the presence of F− anions.
Co-reporter:Dengfeng Wang, Xuelan Zhang, Yangyan Gao, Fukui Xiao, Wei Wei, Yuhan Sun
Fuel Processing Technology 2010 Volume 91(Issue 9) pp:1081-1086
Publication Date(Web):September 2010
DOI:10.1016/j.fuproc.2010.03.017
Various lanthanum compounds were used as the catalyst for the synthesis of dimethyl carbonate (DMC) from methyl carbamate and methanol. Among them, La(NO3)3 presented the best catalytic performance with the DMC yield of 53.7% under suitable reaction conditions. Based on the results of X-ray diffraction, Fourier transform infrared spectroscopy and element analysis, a possible reaction mechanism over lanthanum nitrate was proposed for this reaction.
Co-reporter:Lihong Shi, Debao Li, Bo Hou, Yuelun Wang, Yuhan Sun
Fuel Processing Technology 2010 Volume 91(Issue 4) pp:394-398
Publication Date(Web):April 2010
DOI:10.1016/j.fuproc.2009.06.003
SiO2 was modified by various organic groups before the impregnation of cobalt precursor. These modified supports and the corresponding catalysts were characterized by BET, 29Si CP MAS NMR, XRD, Raman, XPS and H2-TPR. These characterizations clearly show the changes of morphology as well as reducibility of the catalysts. The organic modification of SiO2 remarkably influences the reducibility and catalytic properties of Co catalysts. Co catalyst supported on (CH3)3-modified SiO2 exhibits high activity and C5+ hydrocarbon selectivity. However, COOH-, NH2-, and NH2(CH2)2NH-modified SiO2 distinctly suppress the catalytic activity of Co catalysts.
Co-reporter:Shifang Mu, Debao Li, Bo Hou, Lihong Jia, Jiangang Chen and Yuhan Sun
Energy & Fuels 2010 Volume 24(Issue 7) pp:3715
Publication Date(Web):January 13, 2010
DOI:10.1021/ef901274y
The effect of ZrO2 loading on SBA-15-supported cobalt Fischer−Tropsch catalysts was investigated by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), NH3-temperature-programmed desorption (TPD), and CO hydrogenation. Zirconia was first impregnated into SBA-15 to produce Zr-modified SBA-15 supports, following impregnation of Co. The final catalysts contained Zr content from 0 to 20 wt %. It was found that the promotion of ZrO2 increased the cobalt dispersion, but the Co−Si interaction was gradually replaced by the Co−Zr interaction, which led to a decrease in the reduction degree (<400 °C) of cobalt species. As a result, both CO conversion and C5+ selectivity showed a maximum with appropriate ZrO2 content. Furthermore, C5−C11 hydrocarbon selectivity increased with the rise of ZrO2 content.
Co-reporter:Jun Zhang, Ning Zhao, Wei Wei, Yuhan Sun
International Journal of Hydrogen Energy 2010 Volume 35(Issue 21) pp:11776-11786
Publication Date(Web):November 2010
DOI:10.1016/j.ijhydene.2010.08.025
A series of Ni/Mg/Al/La mixed oxides prepared by thermal decomposition of layered double hydrotalcites (HT) were characterized by XRD, ICP, EXAFS, TGA, TPR-H2, SEM, and N2 adsorption/desorption technique. The results revealed the formation of periclase-type catalysts with mesoporous structure, and the addition of La3+ lowered the phase crystallization with the formation of small oxide particles. Such catalysts had both high activities and stabilities toward partial oxidation of methane (POM). The catalyst containing 6.5 mol.% La3+ showed the highest performance at 1053 K with CH4 conversion of 99%, CO selectivity of 93% and H2 selectivity of 96%, which could be attributed to the presence of highly dispersed nickel and then the resistance to coke formation due to the promotion effect of lanthanum.
Co-reporter:Lei Li, Xia Wen, Xin Fu, Feng Wang, Ning Zhao, Fukui Xiao, Wei Wei, and Yuhan Sun
Energy & Fuels 2010 Volume 24(Issue 10) pp:5773-5780
Publication Date(Web):September 30, 2010
DOI:10.1021/ef100817f
The MgO/Al2O3 sorbent for CO2 capture under low temperatures was investigated in a fixed bed. It was found that, with MgO loading of 10 wt %, MgO/Al2O3 sorbent showed a maximum CO2 capture capacity, which originated from the balance of physical adsorption and chemical absorption of the sorbent. The CO2 capture capacity increased with the water vapor at first and then decreased. Typically, the total CO2 capture capacities were as high as 0.97 and 1.36 mmol/g, with water vapor concentration of 0 and 13 vol %, respectively, at 60 °C with 13 vol % CO2. The high CO2 concentration could be approached by the multi-stage absorption/desorption cycles, during which the sorbent could be regenerated at 350 °C and maintained stable even after 5 cycles. In addition, a deactivation model was proposed that gave good predictions of the CO2 breakthrough curves. Results showed that sorption rate parameters obtained in the presence of water vapor were found to be larger than the corresponding values in the absence of water vapor. It was possibly caused by increasing the reactivity of the sorbent prior to the sorption of CO2 in the presence of water vapor.
Co-reporter:Dengfeng Wang, Xuelan Zhang, Wenbo Zhao, Weicai Peng, Ning Zhao, Fukui Xiao, Wei Wei, Yuhan Sun
Journal of Physics and Chemistry of Solids 2010 Volume 71(Issue 4) pp:427-430
Publication Date(Web):April 2010
DOI:10.1016/j.jpcs.2009.12.005
A series of mixed oxides calcined from hydrotalcite-like compounds with different cations were prepared and their catalytic activities were studied by the synthesis of dimethyl carbonate (DMC) from methyl carbamate and methanol. Among them, ZnFe mixed oxide possessed the best catalytic ability. Furthermore, the zinc-based mixed oxides as well as the corresponding hydrotalcite-like compounds were characterized by using ICP, TGA, CO2-TPD and N2 adsorption/desorption techniques.
Co-reporter:Yanling Zhao;Yao Xu;Dong Wu;Wei Wei
Journal of Sol-Gel Science and Technology 2010 Volume 56( Issue 1) pp:93-98
Publication Date(Web):2010 October
DOI:10.1007/s10971-010-2280-z
A novel CH3-functionalized mesoporous silica material (PTM) with nearly spherical morphology was synthesized by a one-step synthesis route using polymethylhydrosiloxane and tetraethoxylsilane in the presence of triblock copolymer P123 as structure-directing agent. Thus-obtained material possessed highly-ordered mesopore arrays and texture with highly CH3-functionalized surface. As compared with pure siliceous SBA-15, PTM showed the high performance for gas chromatographic separation of hexene isomers.
Co-reporter:Jun Ma, Xuelan Zhang, Ning Zhao, Abdullah S.N. Al-Arifi, Taieb Aouak, Zeid Abdullah Al-Othman, Fukui Xiao, Wei Wei, Yuhan Sun
Journal of Molecular Catalysis A: Chemical 2010 315(1) pp: 76-81
Publication Date(Web):
DOI:10.1016/j.molcata.2009.09.003
Co-reporter:Heqin Guo;Debao Li;Dong Jiang;Wenhuai Li
Catalysis Letters 2010 Volume 135( Issue 1-2) pp:48-56
Publication Date(Web):2010 March
DOI:10.1007/s10562-010-0263-x
The VOx-TiO2 (VT-RC) and sulfated VOx-TiO2 (VTS-RC) catalysts were prepared by rapid combustion method (RC) and evaluated by the one-step oxidation of methanol to dimethoxymethane (DMM). The results showed that the VT-RC and VTS-RC catalysts were consisted of nano-particles and exhibited pore structure. Compared with the coprecipitated VOx-TiO2 (VT-CP) catalyst, the VT-RC catalyst showed more acidic sites and stronger reducibility. The addition of sulfate into VT catalyst further increased the number of acidic sites and had little effect on the reducibility. The catalytic test showed that the VT-RC catalyst exhibited high DMM selectivity (89.96% at 35% methanol conversion), which was further increased on VTS-RC catalyst (91.76% at 48% methanol conversion), and that was due to the larger number of acidic sites and stronger reducibility on these catalysts.
Co-reporter:Jungang Wang;Debao Li;Bo Hou;Litao Jia;Jiangang Chen
Catalysis Letters 2010 Volume 140( Issue 3-4) pp:127-133
Publication Date(Web):2010 December
DOI:10.1007/s10562-010-0449-2
Both mono- and bi-modal Co-based Fischer–Tropsch Synthesis (FTS) catalysts were prepared by incipient-wetness impregnation (IWI). XRD and N2 physisorption revealed that the catalyst with a bi-modal distribution of 2.5–17 nm had the smallest size of cobalt crystal. In this case, the Raman absorbance shifted toward lower frequencies due to the size quantization effect. Furthermore, H2-TPR indicated a lower reducibility originated from the interaction between small crystalline cobalt and silica. Such bi-modal structure catalysts showed a better FTS performance, and particularly the bi-modal mesopores catalyst presented the lowest methane selectivity, the highest activity and the highest selectivity to C5–C18 hydrocarbons, which might be due to the confinement of mesopore to the cobalt particles.The catalyst with a bi-modal distribution of 2.5–17 and 2.5–65 nm showed a better FTS activity, lower methane selectivity than mono-modal catalyst, particularly the bi-modal mesoporous catalyst presented the highest selectivity to C5–C18 hydrocarbons Open image in new window
Co-reporter:Ning Wang;Kegong Fang;Minggui Lin;Dong Jiang;Debao Li
Catalysis Letters 2010 Volume 136( Issue 1-2) pp:9-13
Publication Date(Web):2010 May
DOI:10.1007/s10562-010-0288-1
Fe/K/β-Mo2C catalysts were prepared by the temperature-programmed-reaction (TPRe) method and tested for higher alcohols synthesis (HAS). The catalysts exhibited high catalytic activity and selectivity to higher alcohols (C2+OH). The effect of Fe/Mo molar ratio on the catalytic performance of HAS was investigated and the best one was at Fe/Mo molar ratio of 1/14. It could be concluded that the Fe promoter exerted strong promotion for carbon chain growth, especially for the stage of C1OH to C2OH. The “Fe3Mo3C” and “Fe3C” phases formed over Fe promoted K/β-Mo2C catalysts, which might be responsible for the high activity of higher alcohols and hydrocarbons synthesis, respectively.
Co-reporter:Shuigang Liu, Jun Ma, Lianxiu Guan, Junping Li, Wei Wei, Yuhan Sun
Microporous and Mesoporous Materials 2009 Volume 117(1–2) pp:466-471
Publication Date(Web):1 January 2009
DOI:10.1016/j.micromeso.2008.07.026
Co-reporter:Xiaowei Su, Junping Li, Fukui Xiao, Wei Wei and Yuhan Sun
Industrial & Engineering Chemistry Research 2009 Volume 48(Issue 7) pp:3685
Publication Date(Web):March 3, 2009
DOI:10.1021/ie801148v
The synthesis of methyl salicylate (MS) from salicylic acid (SA) and dimethyl carbonate (DMC) was performed over a series of mesoporous aluminosilicates. The results showed that mesoporous aluminosilicate was an effective esterification catalyst for the reaction. It was also found that both SA conversion and MS selectivity were closely linked with the intermediate strong acidity and Lewis acidity of catalysts. As a result, the synergistic mechanism was proposed for the esterification of SA with DMC over a mesoporous aluminosilicate.
Co-reporter:Shifang Mu;Debao Li;Bo Hou;Jiangang Chen
Catalysis Letters 2009 Volume 133( Issue 3-4) pp:
Publication Date(Web):2009 December
DOI:10.1007/s10562-009-0193-7
TiO2-SiO2 supports were prepared by various methods including precipitation, impregnation, hydrolysis-reflux and sol–gel, and then cobalt was impregnated on those supports. The properties of various catalysts were characterized by N2 physisorption, XRD, XPS and TPR. The introduction of TiO2 led to stronger Co-support interaction, accompanying with the variation of dispersion and reduction degree of cobalt. The catalytic test for F-T synthesis revealed that the addition of TiO2 improved the performance of catalysts prepared by precipitation, impregnation and hydrolysis-reflux, but had a negative effect with sol–gel method.
Co-reporter:Jun Ma, Xuelan Zhang, Ning Zhao, Fukui Xiao, Wei Wei, Yuhan Sun
Journal of Molecular Structure: THEOCHEM 2009 Volume 911(1–3) pp:40-45
Publication Date(Web):15 October 2009
DOI:10.1016/j.theochem.2009.06.033
1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD) has recently been shown to be an effective organocatalyst for the hydrolysis reaction of acetonitrile. This reaction involves the acetamide-forming reaction of acetonitrile hydrolysis and the further hydrolysis of acetamide to form acetic acid and NH3. Density functional theory (DFT) and Hartree–Fock (HF) methods were employed to comprehensively investigate these two hydrolysis steps to elucidate the TBD-catalyzation mechanism. Structures and energies of the reactants, intermediates, transition states and products along the reaction path were presented. Charge population and bond orders were given by natural bond orbital (NBO) analysis to clarify the computed atomic and molecular behaviors. The results showed that compared with the noncatalyzed reaction, the TBD-catalyzed process had significantly lower energy barriers in both the hydration steps and the isomerization steps. As a result, the whole reaction process could be accelerated and the TBD-catalyzation mechanism was clarified.
Co-reporter:Dudu Wu, Wenming Chang, Xia Wen, Fukui Xiao, Junping Li, Ning Zhao, Wei Wei, Yuhan Sun
Fuel Processing Technology 2008 Volume 89(Issue 8) pp:803-807
Publication Date(Web):August 2008
DOI:10.1016/j.fuproc.2008.01.005
A convenient and simple route for synthesis of methyl benzoate from dimethyl carbonate and acetophenone has been exploited for the first time in the presence of solid base catalysts. The results showed that solid base with moderate strength, such as MgO, facilitated the formation of methyl benzoate and the function of basic catalysts could mainly be attributed to the activation of ketone via the abstraction of Hα by base sites.
Co-reporter:Wenbo Zhao, Feng Wang, Weicai Peng, Ning Zhao, Junping Li, Fukui Xiao, Wei Wei and Yuhan Sun
Industrial & Engineering Chemistry Research 2008 Volume 47(Issue 16) pp:5913
Publication Date(Web):June 28, 2008
DOI:10.1021/ie8003732
Various zinc compounds were used as the catalysts for the synthesis of dimethyl carbonate (DMC) from methyl carbamate (MC) and methanol in a batch reactor. Among them, ZnCl2 showed the highest catalytic activity and led to the DMC yield of 33.6% under the optimal conditions. In addition, a possible reaction mechanism was proposed based on Fourier transform infrared (FTIR) and X-ray diffraction (XRD) characterization results.
Co-reporter:Ping Liu, Jie Ren, Yuhan Sun
Microporous and Mesoporous Materials 2008 Volume 114(1–3) pp:365-372
Publication Date(Web):1 September 2008
DOI:10.1016/j.micromeso.2008.01.022
SAPO-11 molecular sieves were synthesized using single agent (i.e. diethylamine (DEA), di-iso-propylamine (DIPA) and di-n-propylamine (DPA)) or a mixture of DEA and DIPA (named DEPA) as the template under hydrothermal conditions. XRD indicated that the directing effect of different templates for AEL structure decreased in the order of DEPA > DPA > DIPA > DEA. 29Si MAS NMR showed that although all SAPO-11 samples synthesized at same Si content, that prepared with the mixed template contained more Si (4Al) sites, whereas Si (nAl, 4-nSi, 0 < n < 4) environments were predominant in the samples synthesized with single template. The results indicated that the mixed template led to a better Si dispersion and then increased the number of total acid sites of SAPO-11. In the isomerization of n-tetradecane over different Pt/SAPO-11 catalysts, the sample prepared with DEPA showed high catalytic activity and selectivity for i-C14, which were related to the most abundant weak acid sites of the sample.
Co-reporter:Dong Jiang, Yao Xu, Dong Wu, Yuhan Sun
Journal of Solid State Chemistry 2008 Volume 181(Issue 3) pp:593-602
Publication Date(Web):March 2008
DOI:10.1016/j.jssc.2008.01.004
A series of dye-modified TiO2 photocatalysts were synthesized using dye Chrysoidine G (CG), tolylene-2,4-diisocyanate (TDI), and commercial TiO2 (Degussa P25) as starting materials. TDI was used as a bridging molecule whose two –NCO groups reacted with Ti–OH of TiO2 and –NH2 groups of CG, respectively. As a result, special organic complexes were formed on the TiO2 surface via stable π-conjugated chemical bonds between TiO2 and dye molecules, confirmed by FT-IR, XPS, and UV–vis spectra. Due to the existence of π-conjugated surface organic complexes, the as-synthesized photocatalysts showed a great improvement in visible absorption (400–550 nm). Methylene blue, as a photodegradation target, was used to evaluate the photocatalytic performance, and the dye-modified TiO2 exhibited much better activity under the visible light irradiation than bare TiO2.Dye-modified TiO2 photocatalysts were synthesized via the reaction between Chrysoidine G (CG), Degussa P25 (TiO2), and tolylene-2,4-diisocyanate (TDI) as a bridging molecule. As a result, π-conjugated surface organic complexes were formed on TiO2 surface. Due to the existence of organic complexes, dye-modified TiO2 catalysts showed great visible absorption and high activity under the visible light irradiation.
Co-reporter:Lei Zhang, Yao Xu, Dong Wu, Yuhan Sun, Xiaodong Jiang, Xiaofeng Wei
Optics & Laser Technology 2008 Volume 40(Issue 2) pp:282-288
Publication Date(Web):March 2008
DOI:10.1016/j.optlastec.2007.05.002
The effect of polyvinylpyrrolidone (PVP) on the structure and laser-induced damage threshold (LIDT) of sol–gel silica anti-reflective films is investigated. The results of dynamic light scattering, transmission electron microscopy, and small angle X-ray scattering, show that the PVP molecules surrounded the silica sol particles through the strong hydrogen bonds between Si-OH groups and the PVP. As a result, the growth of silica particles was restricted and thus the interface layer between the silica particles and the solvent become thickened with PVP content. Furthermore, the PVP reduced the porosity of the film, so the anti-reflection properties of the film were weakened. A multi-fractal analysis showed that the appropriate addition of PVP, 1 weight percent (wt%), could improve the surface fractal structure of the film, but that higher PVP content resulted in reduced surface uniformity. The addition of PVP lead to improved LIDT.
Co-reporter:Lihong Shi, Jiangang Chen, Kegong Fang, Yuhan Sun
Fuel 2008 Volume 87(4–5) pp:521-526
Publication Date(Web):April 2008
DOI:10.1016/j.fuel.2007.03.018
CH3-modified Co/Ru/SiO2 catalysts were prepared and the catalytic performances for Fischer–Tropsch synthesis were investigated. The modified and unmodified catalysts were characterized by FT-IR, N2 physisorption, TG, XRD, TPR and DRIFTS. FT-IR indicated an effective surface organic modification. TG suggested that modified catalysts had good thermal stability. XRD and TPR showed that modified catalysts had similar reducibility and Co3O4 particle size with unmodified catalyst. During reaction tests in a fixed bed reactor it was found that compared with unmodified Co/Ru/SiO2 catalyst CH3-modified Co/Ru/SiO2 catalysts showed higher selectivity to C5–C11 hydrocarbons, which should be ascribed to hydrophobic surface of CH3-modified Co/Ru/SiO2 catalysts.
Co-reporter:Minglin Xiang, Debao Li, Haicheng Xiao, Jianli Zhang, Huijie Qi, Wenhuai Li, Bing Zhong, Yuhan Sun
Fuel 2008 Volume 87(4–5) pp:599-603
Publication Date(Web):April 2008
DOI:10.1016/j.fuel.2007.01.041
Fischer–Tropsch elements (Fe, Co and Ni) modified K/β-Mo2C catalysts were prepared and investigated for their performance in CO hydrogenation. The results revealed that Ni or Co modified K/β-Mo2C catalysts were shown to be highly active and selective towards the synthesis of mixed alcohols, especially for the C2+OH production, but Fe caused a negative effect. Ni or Co led to a decrease in apparent activation energies for C1–C4 alcohols, whereas Fe caused a slight increase for methanol and the decrease for C2–C4 alcohols. As a result, the promotion effects of Fischer–Tropsch elements were different and followed the sequence: Ni ≫ Co > Fe for the activity and Ni > Co > Fe for the C2+OH alcohol selectivity.
Co-reporter:Yachun Liu, Kegong Fang, Jiangang Chen and Yuhan Sun
Green Chemistry 2007 vol. 9(Issue 6) pp:611-615
Publication Date(Web):21 Feb 2007
DOI:10.1039/B614266D
Mesoporous zirconia with different pore sizes have been prepared and investigated as supports of cobalt catalysts for Fischer–Tropsch synthesis (FTS). It was found that the F–T catalytic performances were closely correlated to the pore sizes of the mesoporous zirconia. The average crystalline sizes of Co3O4 grew with increasing the pore size. Furthermore, their reduction degrees were enhanced, in that the Co–ZrO2 interaction decreased with the increase of pore size. The results from the catalyst testing showed that the FTS catalytic activity, C5+ selectivity, C18+ selectivity and the selectivity to C12–C18 paraffins were enhanced, whereas C1 selectivity decreased with increasing pore size. Based on the systemic study on the effects of the pore sizes of mesoporous zirconia on FTS, it was shown that the Co/PMZ-12 catalyst supported on the large pore size mesoporous zirconia exhibited the largest cobalt oxide particle size, the highest reducibility, and thus showed the highest FTS catalytic activity, with especially good selectivity to C12–C18 paraffins as the main component of the clean diesel oil fraction. The result was attributed to the combination of two factors. One was the improvement of the reducibility of the cobalt catalyst, the control of re-adsorption of the α-alkene and chain growth derived from the large pore size and narrow pore size distribution of the mesoporous support. The other was that the cobalt catalyst supported on zirconia displayed a high FTS catalytic activity and C5+ selectivity.
Co-reporter:Debao Li, Cheng Yang, Ning Zhao, Huijie Qi, Wenhuai Li, Yuhan Sun, Bing Zhong
Fuel Processing Technology 2007 Volume 88(Issue 2) pp:125-127
Publication Date(Web):February 2007
DOI:10.1016/j.fuproc.2004.10.008
Ni modified K2CO3/MoS2 catalyst was prepared and the performance of higher alcohol synthesis catalyst was investigated under the conditions: T = 280–340 °C, H2/CO (molar radio) = 2.0, GHSV = 3000 h− 1, and P = 10.0 MPa. Compared with conventional K2CO3/MoS2 catalyst, Ni/K2CO3/MoS2 catalyst showed higher activity and higher selectivity to C2+OH. The optimum temperature range was 320–340 °C and the maximum space-time yield (STY) of alcohol 0.30 g/ml h was obtained at 320 °C. The selectivity to hydrocarbons over Ni/K2CO3/MoS2 was higher, however, it was close to that of K2CO3/MoS2 catalyst as the temperature increased. The results indicated that nickel was an efficient promoter to improve the activity and selectivity of K2CO3/MoS2 catalyst.
Co-reporter:Shuigang Liu, Shiyong Huang, Lianxiu Guan, Junping Li, Ning Zhao, Wei Wei, Yuhan Sun
Microporous and Mesoporous Materials 2007 Volume 102(1–3) pp:304-309
Publication Date(Web):4 May 2007
DOI:10.1016/j.micromeso.2006.12.052
In the synthesis of mesoporous zirconia with a high thermal stability, NaOH solution post-treatment played dual roles: it remarkably improved the thermal stability of mesoporous zirconia, and led to the specific area of the as-made product reached nearly 200 m2 g−1 upon calcination at 700 °C for 4 h. At the same time, a mesoporous strong solid base, Na–ZrO2, was formed after the sodium ions incorporated into the zirconia network. As a result, such a material exhibited a high activity towards the synthesis of dimethyl carbonate (DMC) from methanol and propylene carbonate (PC).
Co-reporter:Dong Jiang, Yao Xu, Bo Hou, Dong Wu, Yuhan Sun
Journal of Solid State Chemistry 2007 Volume 180(Issue 5) pp:1787-1791
Publication Date(Web):May 2007
DOI:10.1016/j.jssc.2007.03.010
A visible light-activated TiO2 photocatalyst was successfully synthesized by the surface organic modification to sol–gel–hydrothermal synthesized TiO2. The surface hydroxyls of TiO2 nanoparticles reacted with the active –NCO groups of tolylene diisocyanate (TDI) to form a surface complex that was confirmed by the FT–IR and XPS spectra. Due to the existence of surface complex, the absorption edge of as-prepared TDI-modified TiO2 nanomaterial extended well into visible region. Compared with unmodified TiO2 and Degussa P25, the TDI-modified TiO2 photocatalysts showed higher activity for the photocatalytic degradation of methylene blue under visible light irradiation.A visible light-activated TiO2 photocatalyst was successfully synthesized by the surface organic modification to TiO2. The surface hydroxyls of TiO2 nanoparticles reacted with the active –NCO groups of tolylene diisocyanate (TDI) to form a surface complex. The TDI-modified TiO2 photocatalysts showed higher activity for the photocatalytic degradation of methylene blue under visible light irradiation.
Co-reporter:Xiaoli Wang;Gongde Wu;Junping Li;Ning Zhao;Wei Wei
Catalysis Letters 2007 Volume 119( Issue 1-2) pp:87-94
Publication Date(Web):2007/11/01
DOI:10.1007/s10562-007-9197-3
A series of typical methyl regulators were used to finely modify the Cr(salen) complex immobilized on MCM-41. Such immobilized complexes were effective catalysts for solvent-free selective oxidation of benzyl alcohol (BzOH) with 30% hydrogen peroxide (H2O2), and they all exhibited much higher catalytic performance than their homogeneous analogue. Simultaneously, the introduction of methyl regulators was found to significantly improve the catalytic performance of immobilized complexes by modifying their surface properties. The optimal BzOH conversion reached 65.0% with 100% selectivity to benzaldehyde (BzH).
Co-reporter:Minglin Xiang, Debao Li, Huijie Qi, Wenhuai Li, Bing Zhong, Yuhan Sun
Fuel 2007 Volume 86(Issue 9) pp:1298-1303
Publication Date(Web):June 2007
DOI:10.1016/j.fuel.2006.08.032
Potassium-promoted β-Mo2C catalysts were prepared and their performances in CO hydrogenation were investigated. The main products over β-Mo2C catalyst were C1–C4 hydrocarbons, only ∼4 C-atom% alcohols were obtained. The products of hydrocarbons and alcohols obeyed traditional linear Anderson–Schultz–Flory (A–S–F) distribution. However, modification with K2CO3 resulted in a remarkable selectivity shift from hydrocarbons to alcohols. Moreover, it was found that potassium promoter enhanced the ability of chain propagation of β-Mo2C catalysts and resulted in a higher selectivity to C2+OH. For K/β-Mo2C catalysts, the hydrocarbon products also obeyed traditional linear A–S–F plots, whereas alcohols gave a unique linear A–S–F distribution with remarkable deviation of methanol compared with that on β-Mo2C catalyst. It could be concluded that potassium promoter might exert a prominent function on the whole chain propagation to produce alcohols. A surface phase on the K/β-Mo2C catalysts such as the “K–Mo–C” explained the higher value for C2+OH, especially could promote the step of C1OH to C2OH, or could have a role in producing directly C2OH, but again this would be speculative. At the same time, the influence of the loadings of K2CO3 on the performances of β-Mo2C catalyst was investigated and the results revealed that the maximum yield of alcohol was obtained at K/Mo molar ratio of 0.2.
Co-reporter:Wei Zhou, Jian-Gang Chen, Ke-Gong Fang, Yu-Han Sun
Fuel Processing Technology 2006 Volume 87(Issue 7) pp:609-616
Publication Date(Web):July 2006
DOI:10.1016/j.fuproc.2006.01.008
The deactivation of Co/SiO2 catalyst for Fischer–Tropsch synthesis (FTS) at different H2 / CO ratios was investigated by XRD, FTIR, BET, XPS, TPR and H2 chemisorption. It was found that the deactivation rate of the catalyst increased with the rise of the H2 / CO ratio. The generation of silicates and/or hydrosilicates species was evidenced by TPR and XPS, and their amounts were monotonously enhanced with increasing H2 / CO ratio, which suggested that the deactivation was caused by the transformation of metallic cobalt into inactive silicates and the high partial pressure of H2 facilitated the formation of the silicates. Moreover, the percentage loss of the surface cobalt was larger than that of bulk cobalt, suggesting that the cobalt silicates and/or hydrosilicates species were formed mainly on the surface of the catalyst or in the small crystallites. For the catalyst run at H2 / CO ratio of 1, it was observed that the sintering also contributed to the catalyst deactivation, but it was a less important factor for the deactivation.
Co-reporter:Yan Zheng, Junping Li, Ning Zhao, Wei Wei, Yuhan Sun
Microporous and Mesoporous Materials 2006 Volume 92(1–3) pp:195-200
Publication Date(Web):20 June 2006
DOI:10.1016/j.micromeso.2006.01.011
Mesostructured AlSBA-15-SO3H materials with various Si/Al ratios were prepared by a one-pot method and characterized by XRD, N2 adsorption, NH3-TPD and Si, Al MAS-NMR techniques. With the incorporation of Al into SBA-15-SO3H, the total acid sites substantially increased. Such materials showed high activity in the esterification of dimethyl carbonate (DMC) with salicylic acid (SA), and the selectivity of methyl salicylate was correlated with the Bronsted acidity of the catalysts.
Co-reporter:Zhijie Li, Bo Hou, Yao Xu, Dong Wu, Yuhan Sun
Journal of Colloid and Interface Science 2005 Volume 288(Issue 1) pp:149-154
Publication Date(Web):1 August 2005
DOI:10.1016/j.jcis.2005.02.082
Silica-modified titanium dioxides were prepared by a hydrothermal method and then characterized by XRD, FT-IR, XPS, TEM, and UV–visible spectroscopy. The silica-modified titanium dioxides were in anatase phase and had large surface areas. There was strong interaction between SiO2 and TiO2, and TiOSi bonds formed during the hydrothermal process. The addition of silica in TiO2 particles could effectively suppress the formation of the rutile phase and the growth of titanium dioxide crystals. DRS spectra proved an increase in the band-gap transition with the increase of silica. The silica-modified TiO2 nanoparticles exhibited better photocatalytic activity, which increased with the silica amount, in comparison with pure TiO2 nanoparticles. Due to better thermal stability, the photocatalytic activity of the silica-modified TiO2 sample held good photocatalytic activity even after calcined at 1273 K.
Co-reporter:Shangru Zhai, Junlin Zheng, Junping Li, Dong Wu, Yuhan Sun, Feng Deng
Microporous and Mesoporous Materials 2005 Volume 83(1–3) pp:10-18
Publication Date(Web):1 September 2005
DOI:10.1016/j.micromeso.2005.03.016
A hydrothermal post-synthesis modification method is introduced as a convenient but efficient route to improve aluminum content and acid amount of hexagonal MSU-S by treatment of it with NaAlO2 solution in the presence of cationic cetyltrimethylammonium bromide (CTAB) under hydrothermal conditions. The speciality of this post-synthesis method, as compared with those reported studies on post-synthesis of Al-containing mesoporous materials, was that it took advantage of the hydrothermally unstable character of silica/aluminosilicate based mesoporous materials which would be partially dissolved in this highly-basic system and the templating function of CTAB. Indeed, characterization results based on a series of techniques (XRD, SEM, TEM, ICP elemental analysis, DSC, 27Al-NMR, FTIR and NH3-TPD) clearly proved that CTAB added in this modification process played a crucial role in the introduction of Al into the final solids via self-assembly with additionally introduced AlO2- and partly dissolved silicates from the parent MSU-S particles. In this way, Al amount determined by ICP and 27Al-NMR, acid content measured by NH3-TPD and therefore catalytic performance of the resultant samples characterized by cumene cracking were substantially improved in comparison with the parent MSU-S. It was also found that, if no CTAB in the modification procedure, the initial well-ordered MSU-S would be severely destroyed losing its mesoporous feature.
Co-reporter:Yao Xu, Dong Wu, Yu Han Sun, Zhi Hong Li, Bao Zhong Dong, Zhong Hua Wu
Journal of Non-Crystalline Solids 2005 Volume 351(Issue 3) pp:258-266
Publication Date(Web):1 February 2005
DOI:10.1016/j.jnoncrysol.2004.11.011
Methyl-modified silica sols were prepared with the polymer of methyltriethoxysilane (MTES), the polymer of dimethyldiethoxysiloxane (DDS), and hexamethydisizane (HMDS) as mono-, di-, and tri-methyl modifiers respectively. By comparing the size and the shape of clusters in three different methyl-modified silica sols, the special nature of the sol was found to be the key to the property of films. Different modal modification of methyl to silica particles led to different cluster fractal structures that influenced the morphology, the porosity of films and consequently the anti-reflection characteristics. The contribution of methyls in or on clusters directly determined the hydrophobicity. Using mono- or di-methyl-modified silica sol, the film/water contact angles were less than 120°. But it could reach 165° when using tri-methyl-modified silica sol. The lowest reflectivity of film could reach 0.0% for all the three modified sols. As a result of the comparative study, tri-methyl-modified silica sol was more suitable to prepare hydrophobic anti-reflective film with required high optical performance.
Co-reporter:Yao Xu, Ruili Liu, Dong Wu, Yuhan Sun, Hongchang Gao, Hanzhen Yuan, Feng Deng
Journal of Non-Crystalline Solids 2005 Volume 351(30–32) pp:2403-2413
Publication Date(Web):1 September 2005
DOI:10.1016/j.jnoncrysol.2005.07.003
In situ liquid 29Si NMR was used to investigate the ammonia-catalyzed hydrolysis and condensation of tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) mixed systems with methanol as solvent. Varying the molar ratio of TEOS, MTES, water and ammonia in original solution, the initial hydrolysis rate constants of TEOS and MTES were calculated as well as the corresponding reactive orders. Under ammonia catalysis, the hydrolysis of TEOS and MTES in mixed system all retained the first-order reaction, similar to the cases of their individual systems. The hydrolysis rate constant of TEOS in mixed system is larger than that in its single system. Meanwhile, the hydrolysis rate constant of MTES in mixed system was smaller than that in its single system. Furthermore the condensation rate constants of TEOS and MTES in mixed system all decreased when compared to the individual condensation rate constants of MTES and TEOS. Another important result was: the reactive orders of both ammonia and water increased to different extent for TEOS and MTES in mixed system. Hydrolysis kinetics shows more compatible hydrolysis–condensation relative rates between TEOS and MTES. Assisted by the solid 29Si MAS NMR and XPS, the obtained hybrid gel showed weak cross-condensation between TEOS and MTES. With the small angle X-ray scattering (SAXS), the double fractal structure in particulate networks was disclosed to be resulted from the more compatible hydrolysis–condensation relative rates between TEOS and MTES.
Co-reporter:Xue-Hong Zhang;Bing Chen;Wei Wei;Yu-Han Sun
Chinese Journal of Chemistry 2005 Volume 23(Issue 10) pp:
Publication Date(Web):4 NOV 2005
DOI:10.1002/cjoc.200591376
Porous silica modified with (CH2)3NH2 (primary amine), (CH2)3NHCH2CH2NH2 (secondary/primary amine) and (CH2)3N-cycl-(CH2)4 (tertiary amine) were synthesized by ultrasonic technique under mild conditions. The samples were characterized by BET, elemental analysis and TG, showing that the organosilane moieties were grafted onto the surface of porous silica by covalent bond. The structure of the organosilane moieties and ultrasonic treatment time were all significant for the quantities of grafted amino groups. The samples exhibited promising catalytic properties towards the methylation reaction of phenol with dimethyl carbonate (DMC). The methylation reaction with the modified samples featured high selectivity at high conversion. The samples were subjected to utilization for a few recycles without obvious loss of activity to indicate that ultrasonic technique was effective for the preparation of organically modified porous silica catalysts.
Co-reporter:Zhijie Li, Bo Hou, Yao Xu, Dong Wu, Yuhan Sun, Wei Hu, Feng Deng
Journal of Solid State Chemistry 2005 Volume 178(Issue 5) pp:1395-1405
Publication Date(Web):May 2005
DOI:10.1016/j.jssc.2004.12.034
Titania–silica composite nanoparticles were prepared by sol–gel-hydrothermal and sol–gel routes, respectively, and their physico-chemical and photocatalytic properties were compared. The results of XRD, TEM and BET surface areas showed that sol–gel-hydrothermal route led to anatase titania–silica composite nanoparticles with large specific surface area, but the sol–gel route tended to form mixture of anatase and rutile. The composite nanoparticles prepared by sol–gel-hydrothermal route had better thermal stability against phase transformation from anatase to rutile, agglomeration and particle growth than those prepared by sol–gel route. On the basis of XRD, FT-IR, XPS and 29Si MAS-NMR, a strong interaction was found between SiO2 and TiO2, and Ti–O–Si bonds formed during both the two routes. But more Ti–O–Si bonds formed in the composite nanoparticles prepared by sol–gel-hydrothermal route than those prepared by sol–gel route. As a result, the titania–silica composite nanoparticles prepared by sol–gel-hydrothermal route exhibited higher photocatalytic activity in decomposition of methylene blue than that prepared by sol–gel route, and it had excellent photocatalytic activity even after calcined at 1000 °C.Comparative study of sol–gel-hydrothermal and sol–gel synthesis of titania–silica composite nanoparticles.
Co-reporter:Shang-Ru Zhai, Jun-Lin Zheng, Dong Wu, Yu-Han Sun, Feng Deng
Journal of Solid State Chemistry 2005 Volume 178(Issue 1) pp:85-92
Publication Date(Web):January 2005
DOI:10.1016/j.jssc.2004.09.034
Novel mesoporous composites comprised of aluminosilicate shell with wormhole framework structure and well-ordered MSU-S core have been firstly prepared via treatment of MSU-S with NaAlO2 solution in the presence of cationic surfactant cetyltrimethylammonium bromide (CTAB). The obtained products were thoroughly characterized by XRD, HRTEM, N2 sorption isotherm, TG-DSC, 27Al MAS NMR and 29Si MAS NMR, etc. Characterization results based on these techniques revealed that the introduction of CTAB during the treatment process played a crucial role in the formation of mesoporous composite, otherwise the parent ordered MSU-S would be completely destroyed. Furthermore, aluminum content in the final product determined by ICP and EDAX was significantly increased compared to the parent MSU-S, thus assuming that CTAB added in this modification process led a key role in the introduction of Al into the final solid via self-assembly with additionally added AlO2− and partly dissolved silicate species from the parent MSU-S particles. In addition, acidity and catalytic performance of the prepared mesoporous composite were also substantially improved in comparison to the parent MSU-S sample.Novel mesoporous composites comprised of aluminosilicate shell with wormhole framework structure and well-ordered MSU-S core have been facilely prepared via treatment of MSU-S with NaAlO2 solution in the presence of cetyltrimethylammonium bromide.
Co-reporter:Wenyu Zhang, Hui Wang, Wei Wei, Yuhan Sun
Journal of Molecular Catalysis A: Chemical 2005 Volume 231(1–2) pp:83-88
Publication Date(Web):20 April 2005
DOI:10.1016/j.molcata.2004.12.025
The base strength and basicity of MgO, CaO and Mg–Al oxide were studied for the synthesis of propylene glycol methyl ether from methanol and propylene oxide. The results showed that solid base with moderate strength such as MgO facilitated the formation of propylene glycol methyl ether. FTIR illustrated that methanol dissociated to methoxide species on MgO surface, while no dissociation took place on CaO. The moderate base strength and weak Lewis acid sites on MgO were very important for the methanol dissociation and then the synthesis of propylene glycol methyl ether.1-Methoxy-2-propanol can be efficiently synthesized over MgO from methanol and propylene oxide due to its base sites with moderate strength, which was illustrated by using CO2-TPD and FTIR.
Co-reporter:Run Xu, Wei Wei, Wen-huai Li, Tian-dou Hu, Yu-han Sun
Journal of Molecular Catalysis A: Chemical 2005 Volume 234(1–2) pp:75-83
Publication Date(Web):14 June 2005
DOI:10.1016/j.molcata.2005.01.048
The structure and catalytic performance of CuMnZrO2 and Fe-CuMnZrO2 catalysts, which were calcined at different temperature, were investigated by BET, XRD, N2O-titration, XANES, EXAFS and TPR. It was found that the calcination temperature strongly influenced the interaction between the active species and support and hence the structure and catalytic performance. Low calcination temperature yielded poorly crystallized catalysts and favored the formation of a Cu(OH)2-like structure. The presence of iron could suppress crystallization of amorphous zirconia and increased the dispersion of copper due to the iron–zirconia interaction within the rise of calcination temperature from 623 to 873 K. However, the addition of iron resulted in the decrease of catalytic activity and selectivity. This could be explained by strong iron–zirconia interaction. It led to the decrease of copper–zirconia interaction, which was responsible for the methanol synthesis, and the decrease of copper–iron interaction, which was responsible for the formation of higher alcohols.The effect of iron on the structure and catalytic performance was investigated by comparison of iron-promoted and un-promoted catalysts calcined at different temperature. It was found that, when the catalysts were calcined at different temperature, the change of metal-support interaction strongly influenced the surface and crystal structure of the catalysts and hence its catalytic performance. Low calcination temperature yielded poorly crystallized catalysts and favored the formation of a Cu(OH)2-like structure, which was highly dispersed. For the CuMnZrO2 catalyst, with the rise of calcination temperature, surface area and dispersion of copper decreased, and the crystallization of zirconia occurred. Nevertheless, the TOF showed a maximum on the catalyst calcined at 873 K due to the increase of the copper–zirconia interaction. The presence of iron could suppress agglomeration of copper species and crystallization of amorphous zirconia. The dispersion of copper was enhanced. However, overall catalytic activity was suppressed. On the one hand, the increase of iron–zirconia interaction with the rise of calcination temperature suppressed the interaction between copper species and zirconia. On the other hand, the interaction between iron and zirconia hindered the reduction of iron oxide, and then copper–iron interaction weakened, which reduced the active sites for higher alcohol formation.
Co-reporter:Ningya Yu, Yanjun Gong, Dong Wu, Yuhan Sun, Qing Luo, Wuyang Liu, Feng Deng
Microporous and Mesoporous Materials 2004 Volume 72(1–3) pp:25-32
Publication Date(Web):8 July 2004
DOI:10.1016/j.micromeso.2004.04.013
Organic–inorganic hybrid mesoporous silicas of MSU with different sizes of organic functionalities of methyl, vinyl, or 3-mercaptopropyl were prepared by using inexpensive sodium silicate and organotrialkoxysilane as the silica precursor via fluoride-mediated co-condensation. The results indicated that both sodium silicate and organotrialkoxysilane could be translated quantitatively into organic–inorganic hybrid materials with high BET surface area (899–1042 m2/g) and pore volume (0.70–1.09 cm3/g). The key to the synthesis of such materials from sodium silicate–organotrialkoxysilane was the separation of hydrolysis and condensation of silica precursor to avoid phase separation due to the obvious difference of condensation rate between aqueous silicate (solution of sodium silicate) and organotrialkoxysilane. Compared with the materials prepared from tetraethoxysilane (TEOS)–organotrialkoxysilane under the same synthetic conditions, the derivatives from sodium silicate–organotrialkoxysilane owned more ordered framework structure and narrower pore diameter distribution due to faster condensation of aqueous silicate.
Co-reporter:Yao Xu, Zhihong Li, Wenhao Fan, Dong Wu, Yuhan Sun, Lixia Rong, Baozhong Dong
Applied Surface Science 2004 Volume 225(1–4) pp:116-123
Publication Date(Web):30 March 2004
DOI:10.1016/j.apsusc.2003.09.041
Abstract
A series of silica–polyvinyl alcohol (PVA) hybrids were prepared by acid-catalyzed hydrolysis of tetraethoxysilane (TEOS) in the mixture of ethanol and water containing dissolved polyvinyl alcohol via a sol–gel process. A small-angle X-ray scattering (SAXS) study on those hybrid gels has been performed utilizing synchrotron radiation. Intensive positive deviation from Porod’s law indicated that there existed density fluctuation within the matrix of silica–PVA hybrid gel. Using the differential d[q3I(q)]/d(q2) as a variant slo, plotting ln(slo) versus ln(q) can produce the dimension n and the amplitude Fl of density fluctuation. Density fluctuation resulted from both the micropores in gel and Si–O–PVA–O–Si bridge between SiO2 particle and PVA chain. When PVA increased in gel, the decreased micropores reduced the fluctuation but PVA enhanced the fluctuation. With the conjunction of correlation function C(r), it was clear that the bridge of Si–O–PVA–O–Si enlarged the compositional heterogeneity within gel matrix and made n increase with the increase of PVA. In addition, the fluctuation dimension n is a fraction rather than an integer that was formerly predicted by Ruland, which may relate to the fractal structure of hybrid gel.
Co-reporter:Ke-Gong Fang;Jie Ren;Yu-Han Sun
Chinese Journal of Chemistry 2004 Volume 22(Issue 11) pp:
Publication Date(Web):26 AUG 2010
DOI:10.1002/cjoc.20040221106
Several 2.0 wt% nickel catalysts supported on nanometer bimodal mesoporous aluminosilicate (NBMAS), AlHMS and AlMCM-41 were prepared by means of the wetness impregnation method. The characterization techniques such as Py-FTIR and H2 chemisorption showed that the amount of Brönsted acid sites decreased in the order of Ni/AlHMS > Ni/AlMCM-41> Ni/NBMAS, while the nickel dispersion differed a little. In the catalytic n-dodecane hydroconversion, the highest conversion was obtained over Ni/NBMAS, and the lowest isomerization selectivity occurred over Ni/AIHMS. For the cracked products, the symmetrical carbon number distribution centered at C6 was obtained on the Ni/AlMCM-41 catalyst due to the well balanced metall/acid functions, whereas the Ni/AlHMS and Ni/NBMAS catalysts led to more C3-C5 and C1+C11 products, respectively.
Co-reporter:Run Xu, Cheng Yang, Wei Wei, Wen-huai Li, Yu-han Sun, Tian-dou Hu
Journal of Molecular Catalysis A: Chemical 2004 Volume 221(1–2) pp:51-58
Publication Date(Web):1 November 2004
DOI:10.1016/j.molcata.2004.07.003
The effect of iron on the structural and catalytic properties of CuMnZrO2 catalysts used for higher alcohols synthesis has been investigated by several techniques (BET, X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS), temperature program reduction (TPR), CO-FTIR and CO hydrogenation). It was found that the presence of iron resulted in substantial changes in both structure properties and catalytic performance. The copper dispersion increased and the catalyst stabilization was improved. The role of iron was dependent on the method of catalyst preparation. The co-precipitation method produced highly dispersed copper species, which favored the synthesis of methanol and branched alcohols. However, the wetness impregnation method gave rise to highly dispersed copper and copper–iron phase, which showed a good performance for synthesis of straight-chain alcohols. Such differences in the performance of catalysts could be attributed to the extent of iron oxide-support interaction, which led to the presence of metallic iron phases in the reduced catalyst.The presence of iron in CuMnZrO2 catalyst resulted in substantial changes in both structure properties and catalytic performance. The dispersion of copper increased and the catalyst stabilization was improved. The role of iron was greatly influenced by catalyst preparation methods. For the Fe–CuMnZrO2 catalyst prepared by co-precipitation method, iron species acted as structural promoter, which increased copper dispersion and improved the formation the homogeneous copper phase. As a result, the introduction of iron by co-precipitation method was favorable to synthesis of methanol and branched products. For the catalyst prepared by wetness impregnation method, the iron oxide-support interaction was relatively weak. The iron oxide could be partially reduced, which led to increase of the interaction between highly dispersed copper and iron. Such interaction was in favor of carbon chain growth to form higher alcohols.
Co-reporter:Tong Wei, Mouhua Wang, Wei Wei, Yuhan Sun and Bing Zhong
Green Chemistry 2003 vol. 5(Issue 3) pp:343-346
Publication Date(Web):29 Apr 2003
DOI:10.1039/B210716N
A CaO/C composite, a new solid base catalyst, was prepared and served as a convenient and efficient heterogeneous catalyst for synthesis of DMC from methanol and propylene carbonate. Compared with pure CaO, the CaO/C shows the same basic properties and a high performance. In addition, the CaO/C catalyst, which is easily recovered, can be reused with little deactivation, if a suitable particle size is chosen.
Co-reporter:Tong Wei, Mouhua Wang, Wei Wei, Yuhan Sun, Bing Zhong
Fuel Processing Technology 2003 Volume 83(1–3) pp:175-182
Publication Date(Web):15 September 2003
DOI:10.1016/S0378-3820(03)00065-1
MgO and CaO prepared from the dissociation of basic magnesium carbonate and calcium carbonate at elevated temperature were used to investigate the effect of base strength and basicity on the synthesis of dimethyl carbonate (DMC) from propylene carbonate (PC) and methanol (MeOH). It was found that the rise of base strength could reduce the temperature needed for this reaction remarkably. On the other hand, with the increase of the amount of base site, the reaction rate rises but DMC selectivity decreases.
Co-reporter:Junling Zhang, Jiangang Chen, Jie Ren, Yongwang Li, Yuhan Sun
Fuel 2003 Volume 82(Issue 5) pp:581-586
Publication Date(Web):1 March 2003
DOI:10.1016/S0016-2361(02)00331-9
Cobalt supported on different γ-alumina carries prepared by incipient wetness impregnation are used to investigate the effect of support on the performance of cobalt catalysts for Fischer–Tropsch synthesis (FTS). It is found that the acidity of support has a great influence on the interaction between metallic cobalt and support and then the reducibility of cobalt. The support with low acidity leads to the higher active FTS catalysts. Furthermore, the high reducibility and more bridged type CO which is favored by γ-alumina with low acidity appears to be responsible for high C5+ hydrocarbon selectivity and low methane selectivity.
Co-reporter:Yan Jun Gong, Zhi Hong Li, Dong Wu, Yu Han Sun, Feng Deng, Qing Luo, Yong Yue
Microporous and Mesoporous Materials 2001 Volume 49(1–3) pp:95-102
Publication Date(Web):15 November 2001
DOI:10.1016/S1387-1811(01)00406-1
Ureidopropyl-incorporated MSU-X (U-MSU-X) and bi-functionalized MSU-X silica materials containing ureidopropyl along with methyl (M-U-MSU-X) or phenyl (Ph-U-MSU-X) were synthesized by a “one-pot” co-condensation from monomeric silicon sources such as tetraethylorthosilicate and ureidopropyltriethoxysilane (UTES), methyltriethoxysilane, phenyltriethoxysilane. The so-produced materials were characterized by X-ray diffraction, FT-IR, 29SiNMR, HRTEM, thermogravimetry analysis, N2 adsorption, bulk element analysis and synchrotron radiation small angle X-ray scattering. The surface and texture properties varied with the content of UTES and the change of organosiloxanes and the organic groups were distributed uniformly in the organo-MSU-X channels and formed interfacial layers.
Co-reporter:Z.H. Li, Y.J. Gong, D. Wu, Y.H. Sun, J. Wang, Y. Liu, B.Z. Dong
Microporous and Mesoporous Materials 2001 Volume 46(Issue 1) pp:75-80
Publication Date(Web):July 2001
DOI:10.1016/S1387-1811(01)00292-X
Small-angle X-ray scattering (SAXS) using synchrotron radiation as X-ray source has been employed to characterize the microscopic structure of organo-modified mesoporous molecular sieves (organo-MSU-X) prepared by a one-pot template-directed synthesis. It is shown that the SAXS profile is hardly constant with Porod's law showing a negative slope, i.e., negative deviation. This suggests that there is a diffuse interfacial layer located between the pores and the matrix. This suggests that the organic groups remain covalently linked to the matrix, as indicated by 29SiCP MAS NMR and FT-IR. The average thickness of the interfacial layer was found to be about 1 nm for each of the three samples with different kinds and the same amounts (20%) of organic groups. This kind of material has also been proved to possess both surface and mass fractal structures. The correction of the negative deviation from Porod's law is performed in order to obtain the pore structure of the amorphous porous silica materials.
Co-reporter:Shuguo Wang, Dong Wu, Yuhan Sun, Bing Zhong
Materials Research Bulletin 2001 Volume 36(Issue 9) pp:1717-1720
Publication Date(Web):July–August 2001
DOI:10.1016/S0025-5408(01)00645-6
Using tetraethyl orthosilicate as a silica source and cetyltrimethylammonium bromide as a template, MCM-48 mesoporous molecular sieves were synthesized with hydrothermal methods. Reducing the pH of the solution during synthesis improved the yield of MCM-48 and enhanced its stability. While the pH was adjusted to 5, a high yield of 98% was gained. XRD and N2 adsorption–desorption isotherms were used to characterize the synthesized samples. These mesoporous molecular sieves showed high specific surface areas and ordered channel systems.
Co-reporter:Peng Gao, Feng Li, Lina Zhang, Ning Zhao, Fukui Xiao, Wei Wei, Liangshu Zhong, Yuhan Sun
Journal of CO2 Utilization (September 2013) Volume 2() pp:16-23
Publication Date(Web):1 September 2013
DOI:10.1016/j.jcou.2013.06.003
•Introduction of fluorine shows a significant influence on properties of catalysts.•The lower CO2 conversion is attributed to the decrease of exposed Cu surface area.•The TOF increase significantly owing to the higher amount of easily reducible CuO.•The CH3OH selectivity highly increases due to the increase of strongly basic sites.•The introduction of fluorine is beneficial for the production of methanol.Fluorine-modified Cu/Zn/Al catalyst was prepared by calcination of the fluorine-containing Cu/Zn/Al hydrotalcite-like precursor and tested for CO2 hydrogenation to methanol. The introduction of fluorine into Cu/Zn/Al catalyst led to lower CO2 conversion mainly due to the decrease of the exposed copper surface area. However, the turnover frequency increased remarkably owing to the higher amount of easily reducible CuO. In addition, the CH3OH selectivity was greatly improved by the remarkable increase of the proportion of strongly basic sites to the total basic sites. As a result, the presence of fluorine in Cu/Zn/Al catalyst was favorable for CO2 hydrogenation to methanol, and the CH3OH yield for the fluorine-modified Cu/Zn/Al catalyst was higher than that for the fluorine-free Cu/Zn/Al catalyst.Download full-size image
Co-reporter:Ping LIU, Jie REN, Yu-han SUN
Journal of Fuel Chemistry and Technology (October 2008) Volume 36(Issue 5) pp:610-615
Publication Date(Web):1 October 2008
DOI:10.1016/S1872-5813(08)60035-3
Different SAPO-11 molecular sieves have been synthesized hydrothermally using mixed template of di-n-propylamine (DPA) and di-iso-propylamine (DIPA) by varying the template content or the ratio of DPA/DIPA. SAPO-11 samples were characterized using X-ray diffraction (XRD), N2 adsorption, NH3-temperature-programed desorption (TPD) and 29Si MAS NMR, and evaluated towards n-tetradecane skeletal isomerization. The results indicated that the template had strong influence on the crystallinity, the Si distribution and the acidity of SAPO-11. The samples prepared at template content of 1.5 and w (DPA) of 66% possessed small silicon domains and large amount of Si(n Al) (0 < n < 4) sites, and the catalysts prepared from these samples showed highest catalytic activity in the hydroisomerization of n-tetradecane because of its high acidity.
Co-reporter:Minglin Xiang, Debao Li, Juan Zou, Wenhuai Li, ... Xichun She
Journal of Natural Gas Chemistry (March 2010) Volume 19(Issue 2) pp:151-155
Publication Date(Web):1 March 2010
DOI:10.1016/S1003-9953(09)60051-7
The X-ray photoelectron spectroscopy (XPS) was used to investigate the surface characteristic of potassium-promoted or un-promoted both β-Mo2Cand α-MoC1−x pretreated by syngas at different temperatures, and the promotional effect of potassium on the catalytic performance was also studied. XPS results revealed that the content of surface Mo and its valence distribution between β-Mo2Cand α-MoC1−x were quite different. Promoted by potassium, the remarkable changes were observed for surface composition and valence of Mo distribution over β-Mo2C. Potassium had strong electronic effect on β-Mo2C, which led to a higher Mo4+ content. On the contrary, potassium had little electronic effect on α-MoC1−x, and K-Mo interaction was weak. Therefore, Mo0 and Mo2+ became the dominant species on the catalyst surface, and the Mo4+ content showed almost no increase as the pretreatment temperature enhanced. In terms of catalytic performance of molybdenum carbides, the increase in Mo0 most likely explained the increase in hydrocarbon selectivity, yet Mo4+ might be responsible for the alcohols synthesis.
Co-reporter:Minglin Xiang, Juan Zou, Debao Li, Wenhuai Li, ... Xichun She
Journal of Natural Gas Chemistry (June 2009) Volume 18(Issue 2) pp:183-186
Publication Date(Web):1 June 2009
DOI:10.1016/S1003-9953(08)60103-6
Nickel and potassium co-modified β-Mo2C catalysts were prepared and used for CO hydrogenation reaction. The major products over β-Mo2C were C1–C4 hydrocarbons, only few alcohols were obtained. Addition of potassium resulted in remarkable selectivity shift from hydrocarbons to alcohols at the expense of CO conversion over β-Mo2C. Moreover, it was found that potassium enhanced the ability of chain propagation with a higher C2+OH production. Modified by nickel, β-Mo2C showed a relatively high CO conversion, however, the products were similar to those of pure β-Mo2C. When co-modified by nickel and potassium, β-Mo2C exhibited high activity and selectivity towards mixed alcohols synthesis, and also the whole chain propagation to produce alcohols especially for the stage of C1OH to C2OH was remarkably enhanced. It was concluded that the Ni and K had, to some extent, synergistic effect on CO conversion.
Co-reporter:Peng Gao, Feng Li, Haijuan Zhan, Ning Zhao, Fukui Xiao, Wei Wei, Liangshu Zhong, Hui Wang, Yuhan Sun
Journal of Catalysis (February 2013) Volume 298() pp:51-60
Publication Date(Web):1 February 2013
DOI:10.1016/j.jcat.2012.10.030
A series of Cu/Zn/Al/Zr hydrotalcite-like precursors with Zr4+:(Al3++Zr4+) from 0 to 0.7 were synthesized by a co-precipitation method. X-ray diffraction and thermogravimetric measurements demonstrated that the yield of the hydrotalcite-like phase decreases with increased Zr content. The Cu/Zn/Al/Zr mixed oxides were then obtained by calcination of the hydrotalcite-like precursors and tested for methanol synthesis from CO2 hydrogenation. With increased Zr4+:(Al3++Zr4+) atomic ratio, the exposed Cu surface area and dispersion of Cu first increase until Zr4+:(Al3++Zr4+) = 0.3 and then decrease. However, the total number of basic sites on catalysts increases continuously. It is also found that the CO2 conversion is related to the exposed Cu surface area and the dispersion of Cu, while the CH3OH selectivity is related to the distribution of basic sites on the catalyst surface. The incorporation of a suitable amount of Zr is beneficial for the production of methanol, and the best catalytic performance is obtained when the Zr4+:(Al3++Zr4+) atomic ratio is 0.3.Graphical abstractWith increasing Zr content, the exposed Cu surface area first increases until Zr4+:(Al3++Zr4+) = 0.3 and then decreases, and the proportion of strongly basic sites shows a similar trend, except for Zr4+:(Al3++Zr4+) = 0.7. Both the CO2 conversion and the CH3OH selectivity exhibit a volcano trend with increasing Zr content.Download high-res image (72KB)Download full-size imageHighlights► The introduction of Zr affects the Cu surface area and Cu dispersion of catalyst. ► The introduction of Zr affects the surface basicity of the reduced catalyst. ► The CO2 conversion is related to the Cu surface area and Cu dispersion of catalyst. ► The methanol selectivity is related to the distribution of basic sites of catalyst. ► The incorporation of suitable amount of Zr is favor for the catalytic performance.
Co-reporter:Kegong Fang, Debao Li, Minggui Lin, Minglin Xiang, Wei Wei, Yuhan Sun
Catalysis Today (30 September 2009) Volume 147(Issue 2) pp:133-138
Publication Date(Web):30 September 2009
DOI:10.1016/j.cattod.2009.01.038
Mixed alcohol synthesis is an important process for the production of oxygenates fuels, fuel additives and other intermediates for chemical feedstocks via CO hydrogenation. The process is a highly exothermal reaction, which essentially needs the combination of carbon-chain growth and CO insertion functions over the catalysts. The key to the development of mixed alcohol synthesis is the selective control of alcohols and efficient removal of reaction heat via both catalyst and reactor innovation. ICC-CAS (Institute of Coal Chemistry, Chinese Academy of Sciences) has been worked on mixed alcohol synthesis over heterogeneous catalysts and gained some interesting results in the catalyst preparation and process engineering. This paper thus briefly introduced the recent research progresses at ICC-CAS.
Co-reporter:Junhua Li, Yao Xu, Dong Wu, Yuhan Sun
Catalysis Today (30 October 2009) Volume 148(Issues 1–2) pp:148-152
Publication Date(Web):30 October 2009
DOI:10.1016/j.cattod.2009.02.046
High dispersion Co3O4 nano-particles supported on hollow mesoporous silica spheres (HMSS) with bimodal pore distribution were prepared by “two-solvent” technique. As-synthesized catalysts were characterized by XRD, N2 adsorption–desorption, XPS, SEM, TEM, and H2-TPR. The results showed that Co3O4 nano-particles were present inside the pore system of HMSS and the particles sizes increased with the increasing loaded cobalt content. The catalysts show good performance and high selectivity of C5–C18 hydrocarbon in F–T synthesis, which should attribute to the unique bimodal pore distribution facilitating reactants to access the active sites and to transport higher hydrocarbon products.
Co-reporter:Dudu Wu, Xin Fu, Junping Li, Ning Zhao, Wei Wei, Yuhan Sun
Catalysis Today (29 February 2008) Volume 131(Issues 1–4) pp:372-377
Publication Date(Web):29 February 2008
DOI:10.1016/j.cattod.2007.10.047
A novel route for the synthesis of methyl acetoacetate by the methoxycarbonylation of acetone with dimethyl carbonate was developed in the presence of solid base catalysts. Solid bases with moderate strength (such as MgO) facilitated the formation of methyl acetoacetate, and the yield of methyl acetoacetate could be linearly correlated with the amount of moderate base sites. The in situ FTIR indicated that the reaction was mainly attributed to the activation of acetone via the abstraction of Hα by basic sites.
Co-reporter:Minglin Xiang, Debao Li, Haicheng Xiao, Jianli Zhang, Wenhuai Li, Bing Zhong, Yuhan Sun
Catalysis Today (29 February 2008) Volume 131(Issues 1–4) pp:489-495
Publication Date(Web):29 February 2008
DOI:10.1016/j.cattod.2007.10.083
Nickel and potassium promoted β-Mo2C catalysts were prepared for CO hydrogenation to higher alcohols synthesis. The results revealed that β-Mo2C produced mainly hydrocarbons, but the addition of potassium resulted in a remarkable selectivity shift from hydrocarbons to alcohols over β-Mo2C. Moreover, it was found that potassium enhanced the ability of chain propagation of β-Mo2C catalyst and led to a higher selectivity to C2+OH. The addition of nickel further enhanced higher alcohols synthesis, which showed the optimum at 1/8–1/6 of Ni/Mo molar ratios. The characterization suggested that there might be a synergistic effect of potassium and nickel on β-Mo2C, which favored the alcohols synthesis. The production of alcohols appeared to be relevant to the presence of Mo4+ species, whereas the formation of hydrocarbons was closely associated with Mo2+ and/or Mo0 species on the surface of β-Mo2C-based catalysts.
Co-reporter:Gongde Wu, Xiaoli Wang, Junping Li, Ning Zhao, Wei Wei, Yuhan Sun
Catalysis Today (29 February 2008) Volume 131(Issues 1–4) pp:402-407
Publication Date(Web):29 February 2008
DOI:10.1016/j.cattod.2007.10.085
The Mg–Al layered-double hydroxides (LDHs) intercalated by three kinds of sulphonato-salen-chromium(III) complexes were prepared and characterized by FTIR, UV–vis, XRD and elemental analysis. It was found that the homogeneous complexes were successfully intercalated into the LDH interlayer via the method of anion exchange followed by coordination with chromium(III) chloride. And the resulting LDH hosted chromium complexes were shown to be effective heterogeneous catalysts for the solvent-free oxidation of benzyl alcohol (BzOH) to benzaldehyde (BzH) using 30% H2O2 as oxidant. Furthermore, owing to the different local environment of the central metal ion chromium(III), the catalyst with the backbone of o-C6H4 displayed the highest catalytic performance followed by the NH(CH2CH2)2 with the (CH2)2 showing the lowest BzH yield. In addition, a tentative mechanism was also discussed.
Co-reporter:Xing Huang, Bo Hou, Jungang Wang, Debao Li, Litao Jia, Jiangang Chen, Yuhan Sun
Applied Catalysis A: General (28 November 2011) Volume 408(Issues 1–2) pp:38-46
Publication Date(Web):28 November 2011
DOI:10.1016/j.apcata.2011.09.004
Co-reporter:Haijun Zhao, Minggui Lin, Kegong Fang, Juan Zhou, Yuhan Sun
Applied Catalysis A: General (25 March 2016) Volume 514() pp:
Publication Date(Web):25 March 2016
DOI:10.1016/j.apcata.2016.01.029
•A novel catalyst of Cu-Mn/Ca-Zr for the MF synthesis from syngas is designed.•The different preparation methods of Cu-Mn/Ca-Zr are employed.•The catalyst prepared by mechanical mixing method shows the optimum catalytic activity.•14.2% CO conversion and 83.4% MF selectivity are obtained on MeM catalyst.•Catalytic activity and MF selectivity are strongly influenced by basic sites and reducibility.Cu-Mn/Ca-Zr catalysts were prepared by mechanical mixing, sol-gel and impregnation methods. The phase structure, surface morphology and the chemical states of catalysts were characterized by XRD, TEM, SEM and XPS. The basic property and reducibility of catalysts were investigated by CO2-TPD and H2-TPR techniques. Several types of basic sites with different basicity could be observed on the surface of catalysts. The sample prepared by impregnation method has the lowest reducibility, and the sample prepared by sol-gel method shows the highest reducibility. The catalytic performance was evaluated for the direct synthesis of methyl formate from syngas in a slurry phase. The catalyst prepared by mechanical mixing method shows the highest CO conversion of 14.2% and methyl formate selectivity of 83.4% among these catalysts, which could be attributed to the large amounts of strong basic sites and low reducibility of the catalyst.Download high-res image (170KB)Download full-size image
Co-reporter:Xuelan Zhang, Dengfeng Wang, Ning Zhao, Abdullah S.N. Al-Arifi, Taieb Aouak, Zeid Abdullah Al-Othman, Wei Wei, Yuhan Sun
Catalysis Communications (10 October 2009) Volume 11(Issue 1) pp:43-46
Publication Date(Web):10 October 2009
DOI:10.1016/j.catcom.2009.08.007
An ionic liquid 1-(triethoxysilyl)propyl-3-methylimidazolium hydroxide ([Smim]OH) was grafted on silica gel with different amount by post-grafting method. Such grafted ionic liquids (GILs), which were verified by means of FTIR, element analysis, 29Si MAS NMR and N2 adsorption–desorption could be used as highly effective heterogeneous catalysts toward propylene carbonate synthesis through cycloaddition of CO2 with propylene oxide under solventless and mild conditions.
Co-reporter:Rongyong Xie, Debao Li, Bo Hou, Jungang Wang, Litao Jia, Yuhan Sun
Catalysis Communications (10 March 2011) Volume 12(Issue 7) pp:589-592
Publication Date(Web):10 March 2011
DOI:10.1016/j.catcom.2010.12.013
Silylated Co3O4-mesoporous SiO2 catalysts were prepared by a surface organic modification to understand the influence of a hydrophobic surface on their performance in the Fischer–Tropsch synthesis (FTS). Fourier transform infra-red (FT-IR) spectra showed that the reaction of the surface silanol groups with hexamethyldisilazane (HMDS) took place effectively, and X-ray diffraction (XRD) indicated that such a modification did not affect Co3O4 crystallite size. Furthermore, hydrogen temperature programmed reduction (H2-TPR) illustrated a higher extent of reduction for silylated Co3O4-m-SiO2 catalysts. As a result, such a silylated core–shell structured Co catalyst showed the higher catalytic activity and better selectivity towards C5–C18 fraction than the unsilylated Co3O4-m-SiO2 catalyst in the FTS, which was likely favorable to the internal transportation and their hydrophobic shell.Download full-size imageResearch Highlights► Core–shell Co3O4-m-SiO2 catalyst could be prepared via the solvothermal method. ► Silylated Co3O4-m-SiO2 catalysts could be prepared using HMDS. ► Orangic modification of Co3O4-m-SiO2 catalysts could enhance reduction degree. ► Silylated Co3O4-m-SiO2 catalysts showed the better C5–C18 selectivity.
Co-reporter:Gongde Wu, Xiaoli Wang, Bing Chen, Junping Li, Ning Zhao, Wei Wei, Yuhan Sun
Applied Catalysis A: General (1 October 2007) Volume 329() pp:106-111
Publication Date(Web):1 October 2007
DOI:10.1016/j.apcata.2007.06.031
Co-reporter:Baoliang Lv, Yao Xu, Dong Wu and Yuhan Sun
Chemical Communications 2011 - vol. 47(Issue 3) pp:NaN969-969
Publication Date(Web):2010/11/12
DOI:10.1039/C0CC03632C
Single-crystal α-Fe2O3 hexagonal nanorings with hexagonal inner hole were synthesized under the stepwise influence of different anionic ligands (F− and SCN−). This is a new method to design and modify crystal structures of transition metal oxide nanoparticles.
Co-reporter:Peng Gao, Feng Li, Fukui Xiao, Ning Zhao, Nannan Sun, Wei Wei, Liangshu Zhong and Yuhan Sun
Catalysis Science & Technology (2011-Present) 2012 - vol. 2(Issue 7) pp:NaN1454-1454
Publication Date(Web):2012/03/20
DOI:10.1039/C2CY00481J
A series of Cu/Zn/Al/Zr catalysts were synthesized by calcination of hydrotalcite-containing precursors with different Cu2+/Zn2+ atomic ratios (n). Two other catalysts (n = 2) were also prepared via phase-pure hydrotalcite-like and conventional rosasite precursors for comparison. XRD and UV-Vis-NIR DRS characterizations demonstrate that most Cu2+ of hydrotalcite-containing materials did not enter the layer structure. The Cu dispersion of the catalysts decreases with the increase of Cu content, while both the exposed Cu surface area and the Cu+ and Cu0 content on the reduced surface reach a maximum when n is 2. The catalytic performance for the methanol synthesis from CO2 hydrogenation was also tested. The catalytic activity and selectivity of the catalysts (n = 0.5–4) via hydrotalcite-containing precursors rise first and then decrease with increasing Cu2+/Zn2+ ratios, and the optimum performance is obtained over the catalyst with Cu2+/Zn2+ = 2. Moreover, the Cu/Zn/Al/Zr catalyst (n = 2) via hydrotalcite-containing precursor exhibits the best catalytic performance, which is mainly due to the maximum content of active species compared with another two catalysts derived from different precursors.
Co-reporter:Mingwei Zhang ; Kegong Fang ; Minggui Lin ; Bo Hou ; Liangshu Zhong ; Yan Zhu ; Wei Wei
The Journal of Physical Chemistry C () pp:
Publication Date(Web):
DOI:10.1021/jp4049583
A simple and reproducible method for the preparation of well-defined iron oxide/mesoporous silica core–shell nanostructure is provided. Iron oxide nanocubes with a narrow size distribution were synthesized through a novel ethanol/acetic acid system using Fe(NO3)·9H2O as an iron source and polyvinylpyrrolidone as a capping agent under mild solvothermal conditions (200 °C). These monodisperse nanoparticles were used directly as the core for the deposition of a mesoporous silica shell via a sol–gel process, resulting in uniform core–shell Fe2O3@SiO2 composites with tailored silica shell thickness and controllable core morphology. In addition, composition as well as magnetization of the reduced core–shell composites could easily be controlled by a reduction process. Furthermore, the iron oxide core in Fe2O3@SiO2 could be completely etched to produce hollow SiO2 nanospheres. The mechanism of formation of the core–shell structure was also proposed by the aid of IR spectrum analysis.
Co-reporter:Changzhen Wang, Nannan Sun, Min Kang, Xia Wen, Ning Zhao, Fukui Xiao, Wei Wei, Tiejun Zhao and Yuhan Sun
Catalysis Science & Technology (2011-Present) 2013 - vol. 3(Issue 9) pp:NaN2443-2443
Publication Date(Web):2013/06/11
DOI:10.1039/C3CY00153A
A mesoporous Ni–CaO–ZrO2 catalyst which showed an excellent performance in the dry reforming of CH4 was thoroughly characterized by using a series of methods including N2 physical adsorption, temperature-programmed reduction (TPR), H2/CO chemisorptions, and so forth. Particularly, samples after different treatments such as calcination, reduction and different periods of reaction were subjected to X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis, by which changes in the phase structure and surface chemistry were followed. The results suggested that metallic Ni was gradually oxidized during the reaction, and a non-stoichiometric Ni–carbon compound was slowly formed. This latter species has a role as an important intermediate (or even active phase). Kinetic studies were then carried out based on these findings, according to which a Langmuir–Hinshelwood model was developed. Both the experimental results and the kinetic analysis provided novel evidence for the bi-functional mechanism of dry reforming over ZrO2-based catalysts.
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