Co-reporter:Chao Sui, Fulong Yuan, Zhiping Zhang, Dong Wang, Xiaoyu Niu, Yujun Zhu
Molecular Catalysis 2017 Volume 437(Volume 437) pp:
Publication Date(Web):1 August 2017
DOI:10.1016/j.mcat.2017.05.004
•Strong interaction between Ru and La1.6Ba0.4NiO4.•Enhancing reducibility and mobility of oxygen species for Ru/La1.6Ba0.4NiO4.•Increasing the amount of the surface adsorbed oxygen and the adsorption capacity of CO and NO of Ru/La1.6Ba0.4NiO4.•Ru3+ species as an effective active site for NO + CO reaction.•High active absorbed species of NO and CO was formed on the surface of Ru/La1.6Ba0.4NiO4.In this paper, the activity of La1.6Ba0.4NiO4 (LBN) and Ru/La1.6Ba0.4NiO4 (Ru/LBN) perovskite-like catalysts was investigated for NO + CO reaction. Meanwhile, Ru/LBN exhibited much higher activity than LBN. The catalysts were fully characterized by means of XRD, elemental analysis, N2-physisorption, H2-TPR, XPS, O2-TPD, NO-TPD and CO-TPD. These results demonstrated that the excellent catalytic performance of Ru/LBN catalyst was associated with the strong interaction between Ru and LBN, leading to enhancing reducibility and mobility of oxygen species and increasing the amount of the surface adsorbed oxygen. In addition, the amount of adsorbed CO and NO increased largely for Ru/LBN. And Ru3+ species on the surface of Ru/LBN was considered as an effective active site for NO + CO reaction. In-situ DRIFTS was used for studying the relationship between catalytic activity and NO, CO adsorption ability, species and sites. The results indicated that the new active species were formed on the surface of Ru/LBN compared with LBN including inorganic carboxylate, monodentate carbonate, Ru-NO, bridged nitrate and nitrite.Ru/LBN exhibited good activity, reducibility, mobility of oxygen species, the amount and species of adsorbed CO and NO, which was associated with the strong interaction between Ru and LBN.Download full-size image
Co-reporter:Liqiang Chen;Rui Li;Zhibin Li;Fulong Yuan;Xiaoyu Niu
Catalysis Science & Technology (2011-Present) 2017 vol. 7(Issue 15) pp:3243-3257
Publication Date(Web):2017/07/31
DOI:10.1039/C7CY00672A
In this work, a series of NixMn1−xTi10 (x = 0.0–0.5) catalysts were synthesized using a one-pot sol–gel method for selective catalytic reduction (SCR) of NO with NH3. The effects of Ni doping on the catalytic activity and SO2 resistance were investigated by XRD, TEM-EDS, XPS, NH3-TPD, H2-TPR, SO2-TPD and in situ DRIFTS. It is found that the higher the amounts of surface Mn4+ and Oα species existing on the catalyst surface, the greater the oxidation ability that they present for NO and NH3, which results in better activity at low temperature and worse selectivity to N2 at high temperature due to the overoxidation of NH3. Among NixMn1−xTi10 (x = 0.0–0.5), the Ni0.4Mn0.6Ti10 catalyst exhibited excellent NH3-SCR activity, a wide temperature window (190–360 °C) and good H2O and SO2 durability even in the presence of 100 ppm SO2 and 15% H2O under a GHSV of 40 000 h−1, which is very competitive for the practical application in controlling the NOx emission from stationary sources. It is concluded that more surface Lewis acid sites and the appropriate contents of surface active Mn4+ and surface oxygen species on the surface of Ni0.4Mn0.6Ti10 play key roles in the special SCR performance due to the interactions among Mn, Ni and Ti oxides. The SO2-TPD and in situ DRIFTS results confirm the reason for the good SO2 resistance of the Ni0.4Mn0.6Ti10 catalyst. Moreover, in situ DRIFTS results reveal that the NH3-SCR reaction over Ni0.4Mn0.6Ti10 mainly follows the Eley–Rideal (E–R)-type mechanism.
Co-reporter:Rui Li;Zhibin Li;Liqiang Chen;Yongli Dong;Shibo Ma;Fulong Yuan
Catalysis Science & Technology (2011-Present) 2017 vol. 7(Issue 21) pp:4984-4995
Publication Date(Web):2017/10/30
DOI:10.1039/C7CY01507K
Mn- or/and Ni-modified SAPO-34 molecular sieves (Mn–SAPO-34, Ni–SAPO-34, and MnNi–SAPO-34) were synthesized by a one-pot hydrothermal synthesis method using morpholine as a structure directing agent. XRD, XRF, SEM, TEM-EDX, UV-vis-DRS, NH3-TPD, XPS, NMR, and in situ DRIFTS analyses were performed to study the properties of the samples. The MnNi–SAPO-34 catalyst demonstrated much better NOx conversion (>95%) and N2 selectivity (>98%) for the selective catalytic reduction (SCR) of NOx by NH3 than those of the other catalysts from 320 °C to 470 °C. Moreover, NOx conversion could still be maintained at about 100% at 380 °C even after 80 h over MnNi–SAPO-34. Its excellent activity can be ascribed to the strong interaction between the Mn and Ni species in the framework of MnNi–SAPO-34, leading to the suitable redox ability of MnNi–SAPO-34 by the reaction Ni3+ + Mn3+ ↔ Ni2+ + Mn4+. The in situ DRIFTS results suggested that the NH3-SCR reaction was mainly performed by an Eley–Rideal (E–R) reaction pathway at 300 °C for the MnNi–SAPO-34 catalyst. Thus, MnNi–SAPO-34 is considered as a promising candidate for controlling NOx emissions at middle temperatures.
Co-reporter:Dong Wang, Yujun Zhu, Chungui Tian, Lei Wang, Wei Zhou, Yongli Dong, Qing Han, Yunfei Liu, Fulong Yuan and Honggang Fu
Catalysis Science & Technology 2016 vol. 6(Issue 7) pp:2403-2412
Publication Date(Web):12 Nov 2015
DOI:10.1039/C5CY01654A
The introduction of a suitable co-catalyst is a promising way to improve the catalytic efficiency of Pt catalysts. Herein, SBA-15 modified with well-dispersed Mo2N nanoparticles (NPs) is synthesized by anchoring phosphomolybdic acid (HPM) on aminated SBA-15 (SBA-15-NH2) primarily, followed by nitridation treatment under NH3. After loading of Pt, the Pt–Mo2N/SBA-15 catalyst with close-contact Pt and Mo2N NPs can be formed. The intensive interaction of Pt and Mo2N benefited from the close contact is verified by XRD and XPS tests. As a result, the ternary Pt–Mo2N/SBA-15 catalysts have shown superior performance to Pt/SBA-15 catalysts for the selective hydrogenation of cinnamaldehyde to cinnamyl alcohol. The TOF over the 1 wt% Pt–Mo2N/SBA-15 catalyst is close to that over the 3 wt% Pt/SBA-15 catalyst, but its selectivity to cinnamyl alcohol (COL) is 2.5 times that of 3 wt% Pt/SBA-15. The promoted activity of Pt–Mo2N/SBA-15 is mainly attributed to the synergistic effect of Pt and Mo2N NPs, which can cause the full development of the catalytic ability of Pt, thus reducing the Pt usage, through increasing the dispersion of Pt NPs and the fraction of Pt0 species in the catalyst.
Co-reporter:Lina Wang, Fulong Yuan, Xiaoyu Niu, Chuanhong Kang, Pengying Li, Zhibin Li and Yujun Zhu
RSC Advances 2016 vol. 6(Issue 46) pp:40175-40184
Publication Date(Web):07 Apr 2016
DOI:10.1039/C6RA02602H
A series of cerous phosphate (CP) catalysts with different crystal structures were synthesized by a hydrothermal method at different temperatures (120, 140, 160, 180 and 200 °C) and their performances for the dehydration of glucose into 5-(hydroxymethyl)furfural (HMF) were also thoroughly investigated. These catalysts were characterized by XRD, N2 adsorption–desorption, SEM, in situ DRIFT, NH3-TPD and XPS. The results indicate that changing the temperature of synthesis will lead to a transformation of the crystal phase and morphology from 120 °C (nanoparticles, hexagonal structure) to 200 °C (nanorods, monoclinic structure); also, the different crystal phases possess different surface Ce4+ amounts and acidities. A good linear correlation is found between the Lewis acid content and the surface Ce4+ amount among these CP catalysts, and very good linearity is also displayed between the Lewis acid amount and the conversion of glucose or the selectivity of HMF, which indicates that Lewis acidity plays an important role in the dehydration of glucose to HMF. CP120, which has a hexagonal crystal structure, exhibits the best catalytic activity (97% conversion of glucose and 61% yield of HMF) because it has the highest amounts of Lewis acid and total acid.
Co-reporter:Liqiang Chen, Xiaoyu Niu, Zhibin Li, Yongli Dong, Dong Wang, Fulong Yuan, Yujun Zhu
Journal of Molecular Catalysis A: Chemical 2016 Volume 423() pp:277-284
Publication Date(Web):November 2016
DOI:10.1016/j.molcata.2016.07.022
•La1.6Ba0.4NiO4-x%BaO(x = 5–20) composites are in-situ prepared and used for NO decomposition.•La1.6Ba0.4NiO4-20%BaO shows N2 yield of 57% at 923 K and can last for at least 500 h.•La1.6Ba0.4NiO4-20%BaO shows N2 yield of 51% at 923 K at molar ratio of O2 to NO equals 1:5.•BaO plays an important role in NOx transportation and storage, favoring the progress of the reaction.The La1.6Ba0.4NiO4-x%BaO (x = 0, 5, 10, 15, 20, 25, 30) catalysts were prepared by heating the mixture of Ba(NO3)2 and La1.6Ba0.4NiO4 in situ, and their catalytic performances were evaluated for NO direct decomposition. The results showed that the activities of the La1.6Ba0.4NiO4-x%BaO catalysts had been improved with the increasing of BaO amount. Among these catalysts, the La1.6Ba0.4NiO4-20%BaO exhibited the best catalytic performance for NO direct decomposition, and the yield of N2 kept 57% during 500 h at 923 K in the absence of O2, even the concentration of O2 was 0.2% in the feed, the N2 yield still up to 57% at 923 K. So much higher activity for the perovskite(-like) oxides catalysts at such reaction temperature was first observed. In order to understand the role of BaO, a serial of experiments and characterizations were carried out on the La1.6Ba0.4NiO4-x%BaO catalysts. The results revealed that the number of chemical adsorption oxygen adsorbed on the oxygen vacancies increased and the mobility of the lattice oxygen could be improved due to the BaO addition. Moreover, BaO may play an important role in NOx transportation and storage, which is favorable for the regeneration of the active sites.
Co-reporter:Wen Jiang, Xiaoyu Niu, Fulong Yuan, Yujun Zhu and Honggang Fu
Catalysis Science & Technology 2014 vol. 4(Issue 9) pp:2957-2968
Publication Date(Web):22 Apr 2014
DOI:10.1039/C4CY00167B
A series of 25% KF–La2O2CO3 catalysts (25-KF–LOC-x, x = 673, 723 and 773) were prepared at different calcination temperatures, which were tested as basic catalysts for the transesterification of tributyrin with methanol to produce methyl butyrate and characterized by means of XRD, SEM, CO2-TPD, FTIR, XPS and XRF. It was found that the calcination temperature greatly influences the catalytic activity, and its order is 25-KF–LOC-673 < 25-KF–LOC-723 < 25-KF–LOC-773. Especially, the 25-KF–LOC-773 catalyst exhibits a very high activity, and the conversion of tributyrin is nearly 100%, the yield of methyl butyrate reaches 94% at 308 K. The activation energy of the 25-KF–LOC-773 catalyst is as low as 55.03 kJ mol−1. The excellent catalytic activity of the 25-KF–LOC-773 catalyst can be attributed to the largest amount of surface hydroxyl among these 25-KF–LOC-x catalysts. The results indicate that the Brønsted base is the main active site at low reaction temperature. The recycling use and stability have been investigated over the 25-KF–LOC-773 catalyst. The results indicate that the 25-KF–LOC-773 catalyst has a high stability after being stored for 90 days. The deactivation of the used 25-KF–LOC-773 catalyst at 308 K is due to the loss of hydroxyl on the surface. However, the conversion of tributyrin can reach 91%, and the yield of methyl butyrate also can achieve 64% when the transesterification reaction is performed at 338 K over the second used 25-KF–LOC-773 catalyst. It indicates that the second used 25-KF–LOC-773 catalyst still possesses good catalytic activity at the higher reaction temperature due to the unchanged strong Lewis basic sites provided with surface oxygen anions.
Co-reporter:Yongli Dong, Xinlin Zhan, Xiaoyu Niu, Jing Li, Fulong Yuan, Yujun Zhu, Honggang Fu
Microporous and Mesoporous Materials 2014 Volume 185() pp:97-106
Publication Date(Web):1 February 2014
DOI:10.1016/j.micromeso.2013.09.037
•Facile synthesis of Co-SBA-16 mesoporous molecular sieves by EISA method.•Cobalt species exists as isolated Co(II) species in tetrahedral coordination.•The excellent catalytic activity for the hydroxylation of benzene to phenol.•Isolated Co(II) species results in the excellent catalytic activity.A series of cobalt-doped SBA-16 (Co-SBA-16) mesoporous molecular sieves with different Co/Si ratio have been directly synthesized by the evaporation induced self-assembly (EISA) method. Characterizations with XRF, XRD, TEM and N2 adsorption–desorption measurements demonstrate that the resultant materials remain a relative ordered cubic cage-like (Im3m) mesostructure wherein a certain amount of cobalt is introduced. Not only the mesostructure of SBA-16, but also the nature and distribution of Co species are strongly affected by the Co/Si ratio in the synthesis of Co-SBA-16. The results of XRD, FT-IR, 29Si MAS NMR, XPS, H2-TPR and DRUV–vis spectra suggest that the introduced cobalt species in Co-SBA-16 mainly exist as isolated Co(II) species in tetrahedral coordination. Most of them are incorporated into silica wall as single framework Co2+ site while other isolated Co(II) species locate on the surface of SBA-16 silica. The excellent catalytic activity has been obtained for the hydroxylation of benzene to phenol due to the presence of these isolated Co(II) species. The highest phenol yield of 28.8% and selectivity of 96.6% with the TON of 51.8 are obtained over Co-SBA-16 catalyst (CS-0.12) using acetic acid as solvent. The reuse and the leaching behavior of cobalt of CS-0.12 catalyst are also investigated.
Co-reporter:Xiwang Ji;Dr. Xiaoyu Niu;Dr. Bo Li;Qing Han; Fulong Yuan; Francisco Zaera; Yujun Zhu;Honggang Fu
ChemCatChem 2014 Volume 6( Issue 11) pp:3246-3253
Publication Date(Web):
DOI:10.1002/cctc.201402573
Abstract
Catalysts made of Pt nanoparticles dispersed on graphene (X wt %Pt/G, X=2.0, 3.5, and 5.0) were prepared and characterized by XRD, Raman spectroscopy, BET surface area measurements, TEM, and X-ray photoelectron spectroscopy (XPS), and a 3.5 wt % Pt supported on Vulcan Carbon catalyst (3.5 wt %Pt/VC) was included as a reference. Although the mean Pt nanoparticle size is approximately 4.4 nm for all X wt %Pt/G and 3.5 wt %Pt/VC catalysts, cinnamal alcohol was produced with high selectivity only with the graphene-supported catalysts: 92 % conversion and 88 % selectivity toward cinnamal alcohol were obtained with 3.5 wt %Pt/G. This catalyst also showed good stability in recycling tests. The good selectivity observed with the graphene-based catalysts is attributed to the higher fraction of reduced surface Pt0 atoms seen on the surface of the Pt nanoparticles (determined by XPS). This interpretation is consistent with DFT calculations. Additional π–π interactions between cinnamaldehyde and graphene may also play a role in the selective hydrogenation of cinnamaldehyde.
Co-reporter:Yi Cheng;Xiaoyu Niu;Tieying Zhao;Fulong Yuan;Honggang Fu
European Journal of Inorganic Chemistry 2013 Volume 2013( Issue 28) pp:4988-4997
Publication Date(Web):
DOI:10.1002/ejic.201300624
Abstract
Cu@C composite spheres with copper nanoparticles dispersed in the carbonaceous matter have been synthesized by a one-step hydrothermal method by using different copper salts mixed with an aqueous glucose solution. The spheres have been characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric–differential thermal analysis, inductively coupled plasma atomic emission spectrometry, Fourier transform infrared spectroscopy, and Raman spectrocopy. The results show that Cu(NO3)2, CuSO4,and CuCl2 exhibit an accelerating effect on the size of the composite spheres, and microsized composites were obtained. However, a morphological change from irregular cubes and spheres to uniform spheres with a narrow size distribution of 340–400 nm was observed when cupric acetate [Cu(Ac)2] was used. Interestingly, Cu2O, generated in situ from Cu(ac)2, plays an important role in the size of the composite spheres. Moreover, a CuO@SiO2 core–shell structure has been synthesized by using the Cu@C composite spheres as a sacrificial template, and the CO + NO reaction was used as a probe reaction to evaluate its catalytic performance. CuO@SiO2 exhibits excellent catalytic performance in the CO + NO reaction.
Co-reporter:Xiaoyu Niu;Chunmei Xing;Wen Jiang
Reaction Kinetics, Mechanisms and Catalysis 2013 Volume 109( Issue 1) pp:167-179
Publication Date(Web):2013 June
DOI:10.1007/s11144-013-0543-8
A series of solid base catalysts of 5–20 % KF/La2O3 were prepared via an impregnation method and used in the transesterification of methanol with tributyrin to produce methyl butyrate. Under the suitable reaction conditions (catalyst amount of 30 mg; reaction temperature of 338 K; reaction time of 1.5 h; the molar ratio of methanol to tributyrin of 30), the tributyrin conversion of 99.9 % and the methyl butyrate selectivity of 98.1 % are obtained over 15 % KF/La2O3 catalyst. Furthermore, the recycling experiment was adopted to investigate the stability of the catalyst, and the surface active site of KF/La2O3 catalyst was also discussed. The X-ray diffraction, CO2-TPD and X-ray fluorescence characterization results indicated that LaOF were generated by the interaction of KF with La2O3, which was good for the transesterification of methanol with tributyrin, and the LaOF may be an effective component to reduce the loss of active site, retaining a certain stability of catalyst.
Co-reporter:Lina Zhao;Yongli Dong;Xinlin Zhan;Yi Cheng;Fulong Yuan
Catalysis Letters 2012 Volume 142( Issue 5) pp:619-626
Publication Date(Web):2012 May
DOI:10.1007/s10562-012-0773-9
V-SBA-16 catalysts with uniform cubic mesoporous structure were prepared by direct hydrothermal method as a function of the pH of the initial gel and characterized by ICP, XRD, TEM, N2 adsorption–desorption, DRUV—vis and Raman spectra. The pH of the initial gel in synthesis of V-SBA-16 show important effects on the maintenance of well ordered mesoporous structure, introduced vanadium content and the incorporation of vanadium into the network of SBA-16 type mesoporous material. The initial gel system with a pH value of 2.0 was found to be a suitable for incorporation of vanadium and retaining the mesostructure of SBA-16. The catalytic activities of V-SBA-16 catalysts were evaluated for the hydroxylation of benzene using molecular O2 as the oxidant. The highest phenol yield of 30.4% with a selectivity of 90% and turnover number of 105 were obtained over the VS-2.0 (1.67) sample prepared at the initial gel system with pH value of 2.0, which is attributed to its high V content and uniform framework V species that highly dispersed on the well ordered SBA-16 type mesoporous materials.
Co-reporter:Yongli Dong;Xiaoyu Niu;Fulong Yuan;Honggang Fu
Catalysis Letters 2011 Volume 141( Issue 2) pp:242-250
Publication Date(Web):2011 February
DOI:10.1007/s10562-010-0490-1
Cu-SBA-16 has been prepared by one-pot synthesis method, and Characterized by XRD, TEM, and N2 adsorption measurements. An extended study about the nature of copper species in the Cu-SBA-16 has been performed by FT-IR, UV-DRS, H2-TPR and XPS. The copper species is mainly present on the mesoporous SBA-16 in the form of isolated mononuclear Cu2+ ions and highly dispersive CuO nanoclusters. The excellent catalytic activity has been obtained for phenol hydroxylation due to the presence of high amount of highly dispersive Cu species. The conversion to phenol and selectivity to diphenol are 29.4 and 91.5%, respectively.A simple EISA strategy for direct synthesis of mesoporous Cu-SBA-16 containing isolated mononuclear Cu2+ ions and highly dispersive CuO clusters which shows an excellent catalytic performance for phenol hydroxylation. Open image in new window
Co-reporter:Yujun Zhu, Yongli Dong, Lina Zhao, Fulong Yuan
Journal of Molecular Catalysis A: Chemical 2010 315(2) pp: 205-212
Publication Date(Web):
DOI:10.1016/j.molcata.2009.09.013
Co-reporter:Liqiang Chen, Rui Li, Zhibin Li, Fulong Yuan, Xiaoyu Niu and Yujun Zhu
Catalysis Science & Technology (2011-Present) 2017 - vol. 7(Issue 15) pp:NaN3257-3257
Publication Date(Web):2017/06/15
DOI:10.1039/C7CY00672A
In this work, a series of NixMn1−xTi10 (x = 0.0–0.5) catalysts were synthesized using a one-pot sol–gel method for selective catalytic reduction (SCR) of NO with NH3. The effects of Ni doping on the catalytic activity and SO2 resistance were investigated by XRD, TEM-EDS, XPS, NH3-TPD, H2-TPR, SO2-TPD and in situ DRIFTS. It is found that the higher the amounts of surface Mn4+ and Oα species existing on the catalyst surface, the greater the oxidation ability that they present for NO and NH3, which results in better activity at low temperature and worse selectivity to N2 at high temperature due to the overoxidation of NH3. Among NixMn1−xTi10 (x = 0.0–0.5), the Ni0.4Mn0.6Ti10 catalyst exhibited excellent NH3-SCR activity, a wide temperature window (190–360 °C) and good H2O and SO2 durability even in the presence of 100 ppm SO2 and 15% H2O under a GHSV of 40000 h−1, which is very competitive for the practical application in controlling the NOx emission from stationary sources. It is concluded that more surface Lewis acid sites and the appropriate contents of surface active Mn4+ and surface oxygen species on the surface of Ni0.4Mn0.6Ti10 play key roles in the special SCR performance due to the interactions among Mn, Ni and Ti oxides. The SO2-TPD and in situ DRIFTS results confirm the reason for the good SO2 resistance of the Ni0.4Mn0.6Ti10 catalyst. Moreover, in situ DRIFTS results reveal that the NH3-SCR reaction over Ni0.4Mn0.6Ti10 mainly follows the Eley–Rideal (E–R)-type mechanism.
Co-reporter:Dong Wang, Yujun Zhu, Chungui Tian, Lei Wang, Wei Zhou, Yongli Dong, Qing Han, Yunfei Liu, Fulong Yuan and Honggang Fu
Catalysis Science & Technology (2011-Present) 2016 - vol. 6(Issue 7) pp:NaN2412-2412
Publication Date(Web):2015/11/12
DOI:10.1039/C5CY01654A
The introduction of a suitable co-catalyst is a promising way to improve the catalytic efficiency of Pt catalysts. Herein, SBA-15 modified with well-dispersed Mo2N nanoparticles (NPs) is synthesized by anchoring phosphomolybdic acid (HPM) on aminated SBA-15 (SBA-15-NH2) primarily, followed by nitridation treatment under NH3. After loading of Pt, the Pt–Mo2N/SBA-15 catalyst with close-contact Pt and Mo2N NPs can be formed. The intensive interaction of Pt and Mo2N benefited from the close contact is verified by XRD and XPS tests. As a result, the ternary Pt–Mo2N/SBA-15 catalysts have shown superior performance to Pt/SBA-15 catalysts for the selective hydrogenation of cinnamaldehyde to cinnamyl alcohol. The TOF over the 1 wt% Pt–Mo2N/SBA-15 catalyst is close to that over the 3 wt% Pt/SBA-15 catalyst, but its selectivity to cinnamyl alcohol (COL) is 2.5 times that of 3 wt% Pt/SBA-15. The promoted activity of Pt–Mo2N/SBA-15 is mainly attributed to the synergistic effect of Pt and Mo2N NPs, which can cause the full development of the catalytic ability of Pt, thus reducing the Pt usage, through increasing the dispersion of Pt NPs and the fraction of Pt0 species in the catalyst.
Co-reporter:Wen Jiang, Xiaoyu Niu, Fulong Yuan, Yujun Zhu and Honggang Fu
Catalysis Science & Technology (2011-Present) 2014 - vol. 4(Issue 9) pp:NaN2968-2968
Publication Date(Web):2014/04/22
DOI:10.1039/C4CY00167B
A series of 25% KF–La2O2CO3 catalysts (25-KF–LOC-x, x = 673, 723 and 773) were prepared at different calcination temperatures, which were tested as basic catalysts for the transesterification of tributyrin with methanol to produce methyl butyrate and characterized by means of XRD, SEM, CO2-TPD, FTIR, XPS and XRF. It was found that the calcination temperature greatly influences the catalytic activity, and its order is 25-KF–LOC-673 < 25-KF–LOC-723 < 25-KF–LOC-773. Especially, the 25-KF–LOC-773 catalyst exhibits a very high activity, and the conversion of tributyrin is nearly 100%, the yield of methyl butyrate reaches 94% at 308 K. The activation energy of the 25-KF–LOC-773 catalyst is as low as 55.03 kJ mol−1. The excellent catalytic activity of the 25-KF–LOC-773 catalyst can be attributed to the largest amount of surface hydroxyl among these 25-KF–LOC-x catalysts. The results indicate that the Brønsted base is the main active site at low reaction temperature. The recycling use and stability have been investigated over the 25-KF–LOC-773 catalyst. The results indicate that the 25-KF–LOC-773 catalyst has a high stability after being stored for 90 days. The deactivation of the used 25-KF–LOC-773 catalyst at 308 K is due to the loss of hydroxyl on the surface. However, the conversion of tributyrin can reach 91%, and the yield of methyl butyrate also can achieve 64% when the transesterification reaction is performed at 338 K over the second used 25-KF–LOC-773 catalyst. It indicates that the second used 25-KF–LOC-773 catalyst still possesses good catalytic activity at the higher reaction temperature due to the unchanged strong Lewis basic sites provided with surface oxygen anions.
