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Chinese Journal of Catalysis
2008, Vol. 29, No. 6
Online: 25 June 2008

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Selective Catalytic Reduction of NO with Propene over Au/Fe2O3/Al2O3 Catalysts WANG Xinkui;*;ZHANG Wansheng;WANG Aiqin;WANG Xiaodong;YANG Xuefeng;ZHANG Tao 2008, 29 (6):  503-505.  Abstract ( 2075 )   [Full Text(HTML)] () PDF (227KB) ( 965 )   A series of Au/Fe2O3/Al2O3 catalysts were prepared by the homogeneous deposition-precipitation method. The catalytic activity of the catalyst samples for selective catalytic reduction of NO by propene under oxygen-rich atmosphere was evaluated. The results showed that 2%Au/10%Fe2O3/Al2O3 exhibited good low-temperature activity. The maximum of NO conversion reached 43% at 300 ℃, while it was only 21% over 2%Au/Al2O3 catalyst at the same temperature. The addition of 2% steam to the feed gas had little effect on the catalytic activity.X-raydiffraction results indicated that both Au and Fe2O3 particles were highly dispersed over Al2O3. H2-temperature-programmed reduction results indicated that there was strong interaction between Au and Fe2O3, which made the reduction of Fe2O3 easy. The synergistic effect between Au and Fe2O3 was probably responsible for the good catalytic performance of the Au/Fe2O3/Al2O3 catalyst at low temperature.

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Effect of LaFeO3 Decoration and Ozone Treatment on the Thermal Stability of Au/Al2O3 for CO Oxidation LIN Qingquan;AN Lidun*;CHEN Junyong;QIN Hua;QI Shixue;ZOU Xuhua 2008, 29 (6):  506-508.  Abstract ( 2253 )   [Full Text(HTML)] () PDF (222KB) ( 919 )   1.1%Au/LaFeOx/Al2O3 catalysts were prepared by the iso-volume impregnation method and activated with H2 and O3. The catalytic performance for CO oxidation at room temperature was investigated by accelerated deactivation tests in 1.0% CO reactant stream at 550 ℃. The introduction of La and Fe enhanced the thermal stability of Au/Al2O3 with a decrease in initial activity, probably due to the formation of LaFeO3 perovskite on Al2O3 surface. The 1.1%Au/2%LaFeO3/Al2O3 activated by H2 can transform 65% CO into CO2 at room temperature after pretreatment in 1.0% CO reactant stream at 550 ℃ for2 h, while 1.1%Au/Al2O3 activated by H2 totally loses its activity. O3 activation can always make 1.1%Au/LaFeO3/Al2O3 more active than that of H2 activation during the pretreatment process in 1.0% CO. After pretreatment for10 h, 1.1%Au/2%LaFeO3/Al2O3 activated by O3 still shows 40% conversion of 1.0% CO at room temperature, whereas those activated by H2 become inactive completely. The better thermal stability of the catalysts activated by O3 may be due to that O3 activation leads to the formation of partially oxidized state of Au in Au/FLA-O3, which may reinforce the interaction between metal and support.

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Epoxidation of Allyl Chloride to Epichlorohydrin by Reversibly Supported Catalyst Heteropolyphosphatotungstates/SiO2 ZHAO Gongda;LI Jun;ZHANG Hengyun;L Ying;XI Zuwei;GAO Shuang* 2008, 29 (6):  509-512.  Abstract ( 2263 )   [Full Text(HTML)] () PDF (157KB) ( 1312 )   The epoxidation of allyl chloride to epichlorohydrin was investigated using a new reversibly supported catalyst, heteropolyphosphatotungstates/silanized silica gel, which was generated in situ in the epoxidation reaction. The effects of reaction time, Na2HPO4 amount, ratio of allyl chloride to H2O2, and particle size of silanized silica gel were examined at a reaction temperature of 65 ℃. The results showed that the epichlorohydrin yield of the initial epoxidation reaction reached 86.5% under the optimized reaction conditions. The catalyst could be reused three times without significant loss of catalytic activity.

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1-Butene Metathesis over a MoO3/H-Mordenite-Alumina Catalyst LIU Huijuan;HUANG Shengjun;ZHANG Ling;LIU Shenglin;WANG Wei;XIN Wenjie;XIE Sujuan;XU Longya* 2008, 29 (6):  513-518.  Abstract ( 2105 )   [Full Text(HTML)] () PDF (357KB) ( 979 )   Metathesis reactions of 1-butene over a MoO3/H-mordenite-alumina (MoO3/HM-Al2O3) catalyst were investigated in a fixed-bed reactor. The catalysts were characterized by NH3 temperature-programmed desorption,X-raydiffraction, and H2 temperature-programmed reduction. The results indicate that under the reaction conditions of 110 ℃, 0.1 MPa, WHSV=1.5 h-1, and TOS=1 h, MoO3 shows no isomerization and metathesis activities. Al2O3, HM-Al2O3, and HM supports only possess suitable isomerization activity controlled by the acidity of the samples, and the isomerization products increase with the acid strength. The yields of products are close to each other on the MoO3/Al2O3 catalyst with less metathesis activity. MoO3/HM-Al2O3 has the best reaction performance, on which 1-butene conversion, propene yield, and pentene yield are 84.9%, 28.5%, and 20.6%, respectively. The acidity of the catalyst and the oxidation state of Mo species are the two key factors for the catalyst performance for 1-butenemetathesis.

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Preparation and Catalytic Activity of Carbon Nanotube-Supported Metallporphyrin Electrocatalyst DENG Xuanying;ZHANG Dongyun;WANG Xin;YUAN Xianxia;MA Zifeng* 2008, 29 (6):  519-523.  Abstract ( 2266 )   [Full Text(HTML)] () PDF (340KB) ( 1366 )   The multiwalled carbon nanotube-supported CoTMPP (CoTMPP/MWNT) electrocatalyst was prepared by the microwave synthesis method and its microstructure was characterized using transmission electron microscopy. The electrocatalytic performance of CoTMPP/MWNT for oxygen reduction reaction (ORR) was evaluated by rotating disc electrode and rotating ring disc electrode technique. Compared with the CoTMPP/MWNT electrocatalyst prepared by the traditional organic reflux method, the one prepared by the microwave synthesis method showed better performance for ORR and the half-wave potential exhibited a positive shift of 110 mV. Compared with CoTMPP/BP2000, the CoTMPP/MWNT electrocatalyst showed a 10 mV higher on-set potential and a 21% lower reduction current loss in ORR, indicating that the multiwalled carbon nanotube-supported CoTMPP electrocatalyst had higher catalytic activity and better stability than CoTMPP/BP2000. The number of exchanged electrons during ORR and the yield of peroxide were 3.6 and 18%, respectively. The high corrosion resistance and unique electronic property of MWNT, and the interaction between MWNT and active metal ions can efficiently improve the electrocatalytic performance of the CoTMPP/MWNT catalyst.

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Selective Catalytic Reduction of NOx by Ethanol and Removal of By-products over Combined Catalyst (Ag/Al2O3+Cu/Ce(x)/Al2O3) SONG Xiaoping;ZHANG Changbin;HE Hong* 2008, 29 (6):  524-530.  Abstract ( 2260 )   [Full Text(HTML)] () PDF (533KB) ( 1036 )   The selective catalytic reduction of NOx by ethanol and the removal of by-products (CO and unburned hydrocarbons) were studied over (Ag/Al2O3+Cu/Ce(x)/Al2O3) (x: molar ratio of Ce to Al) combined catalysts. The combined catalysts showed similar NOx reduction activity to Ag/Al2O3 in the temperature range of 200-350 ℃. CO oxidation capabilities of the oxidation catalysts were improved with increasing Ce/Al ratio. Cu/CeO2 showed the best oxidation activity of CO but caused obvious decrease of NOx conversion when it was directly placed after Ag/Al2O3. (Ag/Al2O3+Cu/Ce(0.15)/Al2O3) was the best in the combined catalysts considering the conversions of NOx, CO, and hydrocarbons. The Cu/Ce(x)/Al2O3 oxidation catalysts were characterized by BET surface area measurement,X-raydiffraction, H2 temperature-programmed reduction, andX-rayphotoelectron spectroscopy. The results showed that the interaction between Cu and Ce is the main factor causing the improvement of CO oxidation.

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MnOx-SnO2 Catalysts Synthesized by a Redox Coprecipitation Method for Selective Catalytic Reduction of NO by NH3 TANG Xingfu;LI Junhua;WEI Lisi;HAO Jiming* 2008, 29 (6):  531-536.  Abstract ( 2452 )   [Full Text(HTML)] () PDF (420KB) ( 1045 )   MnOx-SnO2 composite oxides prepared by a redox coprecipitation route were tested in selective catalytic reduction of NO by NH3 at low temperature. The results showed that the MnOx-SnO2 catalyst with a Mn/(Mn+Sn) molar ratio of 75% exhibted the best performance, on which NO conversion of 100% could be achieved at temperatures of 120-200 ℃. The characterization results of N2 adsorption-desorption,X-raydiffraction, andX-rayphotoelectron spectroscopy indicated that the higher surface area, the formation of solid solution between manganese and tin oxides, and the high oxidation state manganese species were responsible for the high catalytic activity of the MnOx-SnO2 catalyst.

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Asymmetric Reduction of β-Carbonyl Ester with Respiratory-Deficient Mutants of Baker’s Yeast NI Hongliang;YAO Shanjing* 2008, 29 (6):  537-541.  Abstract ( 2324 )   [Full Text(HTML)] () PDF (312KB) ( 1079 )   Asymmetric synthesis of ethyl (S)-4-choloro-3-hydroxybutanoate was studied using ethyl 4-chloro-3-oxobutanoate as the model substrate and glucose as the carbon source. Six respiratory deficient (RD) mutants of natural baker’s yeast were induced by ultraviolet radiation at 254 nm and were identified by 2,3,5-triphenyltetrazolium chloride plate and carbon sources without sugar. The characteristics of catalytic asymmetric reduction and the activity of four mitochondria complexes, Ⅰ, Ⅰ+Ⅲ, Ⅱ+Ⅲ, and Ⅳ, in the electron transfer chain of RD mutants were detected. The results showed that the substrate conversions catalyzed by RD mutants were49%-75%, and the yields were31%-68%, which were lower than that of natural baker’s yeast. The enantiomeric excess (ee) of RD mutants increased to 72%, being 18% higher than that of natural baker’s yeast. The activities ofⅠ-Ⅳmitochondrial complexes in RD mutants were all lower than that in natural baker’s yeast to various degrees.

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Graphite Nanofibers as Catalyst Support for Proton Exchange Membrane Fuel Cells XU Hongfeng*;LU Lu;ZHU Shaomin 2008, 29 (6):  542-546.  Abstract ( 2271 )   [Full Text(HTML)] () PDF (384KB) ( 1117 )   By a ball-milling method, graphite nanofibers (GNF) were prepared from used carbon paper in proton exchange membrane fuel cells. The surface area of GNF was 229.3 m2/g. 20% platinum was loaded on the GNF and XC-72 to fabricate Pt/GNF and Pt/XC-72 supported catalysts. The results of cyclic voltammetry showed that the Pt/GNF catalyst had the same electrochemical surface area (ESA) as the Pt/XC-72 catalyst. The morphology of these catalysts was charaterized by transmission electron microscopy. The electrochemical stability was measured for XC-72, GNF, Pt/XC-72, and Pt/GNF electrodes by the constant-potential oxidation. The peak current increased by 2% for GNF while 60% for XC-72. The corrosion current for Pt/XC-72 was 1.4 times of that for Pt/GNF. In addition, almost 84.7%ESA was lost for Pt/XC-72 catalyst after oxidation for60 h, while only 37.2%ESA was lost for Pt/GNF. The results indicated that GNF possessed much higher resistance to electrochemical oxidation than XC-72.

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Tungsta Promotion of Selective Catalytic Reduction of NOx by NH3 over Ceria-Zirconia Catalyst LI Ye;CHENG Hao;LI Deyi;QIN Yongsheng;WANG Shudong* 2008, 29 (6):  547-552.  Abstract ( 2225 )   [Full Text(HTML)] () PDF (417KB) ( 1313 )   CeO2-ZrO2 and 10%WO3/CeO2-ZrO2 catalysts were characterized by NH3 temperature-programmed desorption, H2-temperature-programmed reduction, and X-ray photoelectron spectroscopy. Their activity in the selective catalytic reduction (SCR) of NOx with NH3 was compared. The results show that the promotion effect of WO3 may be related to the increase of acidity and redox properties of the catalyst. CeO2-ZrO2 shows less than 65% and 10%WO3/CeO2-ZrO2 shows more than 80%NOx conversion in the temperature range of 220-420 ℃ at NH3/NO=1 and space velocity of90000h-1. The addition of 10%H2O and 10%CO2 decreases the catalyst activity at low temperature by competitive adsorption on the catalyst surface and improves the NOx conversion at high temperature. The CeO2-ZrO2 catalyst shows less than 46% and the 10%WO3/CeO2-ZrO2 catalyst shows more than 80%NOx conversion in the temperature range of 230-500 ℃.

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Hydroisomerization of Model Naphtha over Sulfided Co-Mo/SBA-15 Catalyst ZHANG Xiaoyan;SHI Guojun;ZHAO Yu;SHEN Jianyi* 2008, 29 (6):  553-558.  Abstract ( 2204 )   [Full Text(HTML)] () PDF (439KB) ( 921 )   The Co/SBA-15, Mo/SBA-15, and Co-Mo/SBA-15 catalysts were prepared by the incipient wetness impregnation method. Their textural properties and surface acidity were characterized. In addition, these sulfided catalysts were compared with an industrial Co-Mo/γ-Al2O3catalyst in the hydrodesulfurization (HDS) of thiophene and hydroisomerization of 1-hexene. The results showed that Co-Mo/SBA-15 catalyst exhibited comparable HDS reactivity to the Co-Mo/γ-Al2O3catalyst. The Co-Mo/SBA-15 catalyst exhibited strong Brnsted acidity whereas the Co-Mo/γ-Al2O3catalyst possessed mainly strong Lewis acidity. Although the Mo/SBA-15 catalyst also possessed strong Brnsted acidity, it showed lower catalytic activity for skeletal isomerization of 1-hexene owing to its higher hydrogenation activity. On the other hand, the Co-Mo/SBA-15 catalyst exhibited not only strong Brnsted acidity but also relatively low hydrogenation activity, and hence the skeletal isomerization of 1-hexene over the Co-Mo/SBA-15 catalyst was higher, showing the potential application in industry.

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Phase Transformation in Cu-Fe-Based Catalyst during CO Hydrogenation LIN Minggui;FANG Kegong;LI Debao;SUN Yuhan* 2008, 29 (6):  559-565.  Abstract ( 2808 )   [Full Text(HTML)] () PDF (575KB) ( 1214 )   Phase transformation, especially the state of iron, in the Cu-Fe-based catalyst during CO hydrogenation was investigated byX-raydiffraction, Mssbauer spectroscopy,X-rayphotoelectron spectroscopy, and laser Raman spectroscopy. Fe2O3 transformed into a mixture of Fe3O4 and χ-Fe5C2 upon syngas pretreatment at 300 ℃, and the percentage of χ-Fe5C2 went through a maximum during the reaction. The exposure of the reduced catalyst to the reaction conditions clearly influenced its morphology. However, no clear carburization of iron was observed on the surface of the reduced catalyst. The obvious discrepancy was due to the unique reduction characteristic of iron, leading to the enrichment of zinc and manganese atoms on the surface. Instead, iron atoms were enriched on the surface during the CO hydrogenation, which was resulted from the change of oxidation-reduction properties. After reduction, some free carbon deposited on the catalyst surface, and their graphitization took place when the reaction was carried out at 220 ℃ and was enhanced with increasing reaction temperature. This process significantly weakened the synergistic effect between copper and iron and therefore restrained the chain growth ability of the Cu-Fe-based catalyst.

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Use of Citric Acid in Synthesizing a Highly Dispersed Copper Catalyst for Selective Hydrogenolysis Ming-Hoong LOOI;Shuk-Tong LEE;Sharifah Bee ABD-HAMID 2008, 29 (6):  566-570.  Abstract ( 2354 )   [Full Text(HTML)] () A highly dispersed Cu catalyst supported on silica was prepared by an incipient wetness impregnation method with citric acid. The synthesis was studied by nitrogen physisorption, X-ray diffraction, and temperature programmed reduction by comparing with a reference prepared without citric acid. The catalyst precursor obtained after impregnation was X-ray amorphous. The precursor was readily transformed to crystalline CuO upon calcination. The CuO particles were of uniform size in a highly dispersed state and can be reduced to Cu at a lower temperature. The activity of the Cu catalyst obtained was an order of magnitude higher than that of the reference for the hydrogenolysis of methyl laurate to dodecanol.

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Catalytic activity of nano-V2O5/ZnO photocatalyst for degradation of nonylphenyl poly(oxyethylene)ether HU Lili;DU Zhiping*;TAI Xiumei;LI Qiuxiao;ZHAO Yonghong 2008, 29 (6):  571-576.  Abstract ( 2472 )   [Full Text(HTML)] () PDF (511KB) ( 1075 )   The nano-V2O5/ZnO photocatalyst samples with different V2O5 contents were prepared by the ammonia immersion method. The crystal structure, specific surface area, particle morphology, surface composition, and spectral characteristics were analyzed byX-raydiffraction, N2 adsorption, transmission electron microscopy,X-rayphotoelectron spectroscopy, and diffuse reflectance ultraviolet-visible spectroscopy, respectively. The catalytic activity of the V2O5/ZnO photocatalyst samples for degradation of nonylphenyl poly(oxyethylene)ether(NPE-10) was measured under the irradiation with ultraviolet light and visible light. The crystal size of V2O5/ZnO decreased but its specific surface area increased slightly with the increase of V2O5 content. Compared with the nano-ZnO, the binding energy of V 2p in V2O5/ZnO decreased, but the binding energy of Zn 2p and O 1s increased. The amounts of hydroxyl oxygen and adsorbed oxygen on the V2O5/ZnO surface increased remarkably in contrast to those of the ZnO sample. The catalytic activity of the 2.5% V2O5/ZnO photocatalyst (where 2.5% meansn(V)/n(Zn)value) was the highest, and the degradation rate of NPE-10 was about 79% and 61% under the irradiation of ultraviolet light and visible light for3 h, respectively.

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Asymmetric Reduction of Ethyl 4-Chloro-3-oxobutanoate to Ethyl (S)-4-Chloro-3-hydroxybutanoate Catalyzed by Aureobasidium pullulans in an Aqueous/Ionic Liquid Biphase System ZHANG Fan;NI Ye;SUN Zhihao*;ZHENG Pu;LIN Wenqing;ZHU Po;JU Nianfeng 2008, 29 (6):  577-582.  Abstract ( 2631 )   [Full Text(HTML)] () PDF (418KB) ( 1206 )   The asymmetric reduction of ethyl 4-chloro-3-oxobutanoate (COBE) to ethyl (S)-4-chloro-3-hydroxybutanoate ((S)-CHBE) catalyzed by Aureobasidium pullulans CGMCC 1244 was performed in an aqueous/ionic liquid biphase system to improve the productivity and optical purity of (S)-CHBE. The influences of reaction parameters such as shaking rate, phase volumetric ratio, reaction temperature, initial substrate concentration, and pH were studied. In the aqueous/[bmim]PF6 biphase system and under the optimum reaction conditions of 30 ℃, pH 6.6, rotation speed 180 r/min, and reaction time of8 h, the conversion of COBE, the enantiomeric excess, and the concentration of (S)-CHBE were 95.6%, 98.5%, and 47.1 g/L, respectively. When the substrate was fed in batches under the condition of pH 6.6, the accumulated product concentration could reach up to 75.1 g/L.

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Effect of Calcination Temperature on Properties of Fe2O3-K2O Catalyst for Dehydrogenation of Ethylbenzene LIAO Shijie;FAN Qin;CHEN Tong;MIAO Changxi;CHEN Qingling;* 2008, 29 (6):  583-587.  Abstract ( 2199 )   [Full Text(HTML)] () PDF (419KB) ( 960 )   The Fe2O3-K2O catalyst for ethylbenzene dehydrogenation was prepared by a mixing method. The structure and reduction properties of the catalyst calcined at different temperatures were characterized byX-raydiffraction, Mssbauer spectroscopy, mercury intrusion porosimetry, temperature-programmed reduction, and thermogravimetric analysis-differential thermal analysis. The results showed that, with the increase of calcination temperature, the specific surface area of the catalyst was decreased, but its average pore diameter increased. The calcination temperature also had effect on the structure of K2Fe22O34, the precursor of active phase of the catalyst, leading to the decrease in the content of Fe3+on tetrahedral site and the increase in the content of Fe3+on octahedral site, and the catalyst became more reducible. The induction period for the catalyst stationary activity was decreased with the increase in calcination temperature and too high calcination temperature would deteriorate the catalyst stability