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Chinese Journal of Catalysis
2009, Vol. 30, No. 10
Online: 25 October 2009

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Promotional Effect of Cr on the Activity of In/WO3/ZrO2 for Selective Reduction of NO with Methane JING Guohua;LI Junhua;*;HAO Jiming 2009, 30 (10):  973-975.  Abstract ( 1826 )   [Full Text(HTML)] () PDF (344KB) ( 666 )   Cr-modified In/WO3/ZrO2 (In/WZr) catalysts were prepared by impregnation and mechanical mixing methods. Their activity for selective catalytic reduction of NO with CH4 was investigated. The results showed that the catalyst activity was enhanced by mixing Cr2O3 with In/WZr. The enhancement of the activity was due to the oxidation ability of Cr2O3, which improved the conversion of NO to NO2. However, for the catalysts prepared by impregnation, some of the trivalent chromium (Cr3+) was converted to Cr6+, which resulted in the lower activity than the initial In/WZr catalyst by the complete oxidation of CH4 to CO2 and H2O.

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Effect of Pore Structure of SiO2 on Catalytic Performance of Pd-SiW12/SiO2 for Direct Oxidation of Ethylene to Acetic Acid XU Shuliang;;WANG Lixia;;CHU Wenling;*;YANG Weishen;* 2009, 30 (10):  976-980.  Abstract ( 1997 )   [Full Text(HTML)] () PDF (476KB) ( 978 )   The Pd-SiW12/SiO2 catalysts with different pore structure of SiO2 were prepared for direct oxidation of ethylene to acetic acid. The catalysts were characterized by X-ray diffraction, N2 physical adsorption, infrared spectroscopy of adsorbed pyridine, and H2-pulse chemical adsorption. The results showed that the pore structure of SiO2 had an important influence on the catalytic performance of the catalysts. The Pd-SiW12/SiO2 catalyst prepared by the SiO2 support with larger pore size and pore distribution exhibited the highest catalytic activity, on which 145.2 g/(L·h) of acetic acid yield was obtained. Pd dispersion was responsible for the catalytic activity of the Pd-SiW12/SiO2 catalyst.

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Catalytic Oxidative Removal of Dimethylsulfoxide by Hexadentate 8-Quinolinolato Manganese(III) Complexes XIE Fang;FU Zaihui*;ZHONG Sheng;YE Zhengpei;ZHOU Xiaoping;LIU Fenglan;LU Chunli;RONG Chunying;MAO Liqiu;YIN Dulin 2009, 30 (10):  981-985.  Abstract ( 2228 )   [Full Text(HTML)] () PDF (20927KB) ( 492 )   A series of hexadentate 8-quinolinolato manganese(III) complexes (Q3MnIII), with NH4OAc and HOAc as additives, were highly efficient catalysts for the oxidation of dimethylsulfoxide (DMSO) with aqueous hydrogen peroxide in an environmentally friendly acetone-water medium. The halogen substituents on the ligand improved the catalytic efficiency of Q3MnIII complexes, which was likely due to their strong distortion effect on Q3MnIII as indicated by the B3LYP/6-311G+(d) calculation. Various parameters were investigated and a reaction mechanism was proposed.

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Hydrogen Permeation and Chemical Stability of a Ni-BaCe0.6Zr0.2Nd0.2O3-δ Cer-met Membrane ZHAN Shijing;ZHU Xuefeng;*;WANG Weiping;JI Baofeng;YANG Weishen;*;LIN Liwu 2009, 30 (10):  986-990.  Abstract ( 1920 )   [Full Text(HTML)] () PDF (2908KB) ( 733 )   A new Ni-BaCe0.6Zr0.2Nd0.2O3-δ (Ni-BZCN6) cermet membrane was investigated to separate hydrogen from hydrogen-containing mixtures. Hydrogen permeation properties of the membrane and permeation stability under atmospheres containing CO2 and H2O were investigated under different conditions. Hydrogen permeation flux increases with increasing temperature. When the feed gas was moistened by 3% H2O, the flux was about 2–5 times that not moistened. It reached 0.073 cm3/(min cm2) at 900 °C when a wet feed gas of 80% H2/He was used. After 100 h operation under 30% CO2, the membrane still keeps a steady permeation flux. These results suggest that the Ni-BZCN6 membrane is suitable for hydrogen separation from mixed gas containing H2 and CO2.

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Preparation of V2O5/NiO Catalysts by Solid Phase Ball Milling for Oxidative Dehydrogenation of Propane SIQINTANA B;XU Aiju;ZHANG Yu;ZHAORIGETU B* 2009, 30 (10):  991-996.  Abstract ( 1804 )   [Full Text(HTML)] () PDF (3539KB) ( 1031 )   V2O5/NiO catalysts were prepared by a solid phase ball milling method using NiO and V2O5 calcined at different temperatures as precursors.The influence of precursor calcination temperature on the catalytic performance of the V2O5/NiO catalysts for oxidative dehydrogenation of propane to propene was investigated. The catalysts were characterized by X-ray diffraction, nitrogen physisorption, inductively-coupled plasma atomic emission spectroscopy, transmission electron microscopy, hydrogen temperature-programmed reduction, and X-ray photoelectron spectroscopy. The results showed that the prerared V2O5/NiO catalysts exhibited better catalytic performance and the catalyst obtained from the precursor calcined at 400 oC exhibited high selectivity for propene, which is due to their more noncomplete reduction oxygen species Oδ- existed on the surface of V2O5/NiO. At 475 oC, 20.1% of C3H8 conversion and 71.2% of C3H6 selectivity were observed over V2O5/NiO catalyst when the precursors were calcined at 400 oC.

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Application of Cerium-Zirconium Solid Solution Prepared by a Micro-wave-Assisted Method to CO Low-Temperature Oxidation YANG Zhiqiang;MAO Dongsen*;ZHU Huilin;LU Guanzhong 2009, 30 (10):  997-1000.  Abstract ( 2154 )   [Full Text(HTML)] () PDF (428KB) ( 1059 )   Three different Ce0.6Zr0.4O2 solid solutions were prepared by the co-precipitation method combined with room temperature aging, conventional heating reflux, and microwave-assisted heating reflux and used as the supports to prepare CuO catalysts by an impregnation method. The textural and reductive properties of the Ce0.6Zr0.4O2 supports and CuO/Ce0.6Zr0.4O2 catalysts were characterized by N2 adsorption, X-ray diffraction, and temperature-programmed reduction by hydrogen. In addition, the catalytic activity of the catalysts for CO low-temperature oxidation was tested. The results showed that the support prepared by the microwave-assisted method has the largest surface area and pore volume (170.8 m2/g and 0.408 cm3/g, respectively), and the CuO species loaded exhibited good dispersion and reducibility, which resulted in a high catalytic activity of the corresponding CuO/Ce0.6Zr0.4O2 catalyst for CO low-temperature oxidation.

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Support Effect on Catalytic Oxidation of Formaldehyde over Supported Gold Catalysts LI Hongfang;LIU Xuesong;GUO Cunxia;LIU Tong;LUO Mengfei;LU Jiqing* 2009, 30 (10):  1001-1006.  Abstract ( 2100 )   [Full Text(HTML)] () PDF (4078KB) ( 1472 )   Au catalysts supported on Al2O3, TiO2, CeO2, and SiO2 were tested for HCHO oxidation. The reactivity was influenced by the chemical state of Au and the properties of the supports. The highest activity obtained on the Au/CeO2 catalyst was due to cationic Au species in the catalyst and the formation of AuCeO2 solid solution, by which oxygen vacancies could activate the oxygen species for the reaction.

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Mechanism of Selective Catalytic Reduction of NO at Low Temperature over V2O5/ACF Catalysts HOU Yaqin;HUANG Zhanggen;*;MA Jianrong;GUO Shijie 2009, 30 (10):  1007-1011.  Abstract ( 2290 )   [Full Text(HTML)] () PDF (1602KB) ( 1103 )   A novel V2O5/activated carbon fiber (ACF) catalyst for NO removal was prepared. The mechanism of selective catalytic reduction of NO was carried out by a transient response experiment and NH3 adsorption and oxidation. The results show that NH3 adsorption is necessary and is a fast process. The active sites can be easily formed in the presence of O2. Adsorption and temperature-programmed desorption with online mass spectroscopy analysis were used to study the adsorption and oxidation behavior of NH3 at 120 oC over the V2O5/ACF catalyst. The adsorbed NH3 can be oxidized to N2H2 on the catalyst surface, and N2H2 is an intermediate of oxidized NH3.

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Preparation and Characterization of Methanol Tolerant Pd-Co/C Electrocata-lysts for Direct Methanol Fuel Cells LIU Ying;;ZHAO Hong;*;YAN Shiyou;QI Jing;SUN Gongquan;* 2009, 30 (10):  1012-1016.  Abstract ( 2239 )   [Full Text(HTML)] () PDF (3515KB) ( 1366 )   Pd/C and Pd-Co/C electrocatalysts were prepared by sodium borohydride co-reduction and successive reduction. X-ray diffraction,?transmission electron microscopy, cyclic voltammetry, and rotating disk electrode were carried out to characterize these electrocatalysts. The results showed that the Pd-Co/C electrocatalysts have a single-phase face-centered-cubic disordered structure and the lattice constant is obviously smaller than that of Pd/C electrocatalyst. The Pd-Co/C electrocatalyst prepared by the successive reduction method not only has the highest oxygen reduction reaction activity but also shows good methanol tolerant capability.

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Preparation of MoO3-CeO2-SiO2 Oxidative Desulfurization Catalysts by a Sol-Gel Procedure ZHANG Jian;BAI Xiumei;LI Xiang;WANG Anjie;*;MA Xuehu 2009, 30 (10):  1017-1021.  Abstract ( 2488 )   [Full Text(HTML)] () PDF (477KB) ( 943 )   MoO3-CeO2-SiO2 mixed oxides were prepared by the sol-gel method. The catalysts were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The catalyst activity for the oxidative desulfurization of dibenzothiophene (DBT) with cumene hydroperoxide as the oxidant in toluene was investigated at 40 oC and atmospheric pressure. The optimum Mo/Si and Ce/Si molar ratios were 0.1 and 0.02, respectively. Crystalline MoO3 was observed in the MoO3-CeO2-SiO2 catalysts. The introduction of CeO2 promoted the high dispersion of MoO3 over SiO2. Mo6+ was the predominant species in MoO3/SiO2, and Mo5+ species appeared after the introduction of CeO2. The presence of Mo5+ may be responsible for the good performance of MoO3-CeO2-SiO2 in the oxidative desulfurization of DBT.

Research papers

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Reaction Coupling of Methane Steam Reforming and Methane Dehydroaroma-tization for Improving Durability of Mo/MCM-49 Catalyst YAO Songdong;SUN Changyong;LI Juan;GU Lijun;SHEN Wenjie* 2009, 30 (10):  1022-1028.  Abstract ( 1940 )   [Full Text(HTML)] () PDF (369KB) ( 741 )   The durability of methane dehydroaromatization (MDA) has been improved by its combination with methane steam reforming (MSR). The methane conversion in the combined MSR/MDA system decreases very slowly from 11.5% at 12.5 h to 6.5% at 60 h, whereas it decreases rapidly from 14.5% at 0.5 h to 3.5% at 15 h for the MDA reaction alone. CO and H2 produced in-situ through the MSR reaction may reduce the amount of CHx species during the reaction, which in turn reduces the formation of coke deposited on the catalyst, prolonging the durability of the MDA reaction. High content of H2 from the MSR process plays a major role in suppressing coke accumulation on the catalyst, especially the coke associated with the Brönsted acidic sites that are mainly responsible for the deactivation.

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Effect of CNT Surface Modification on Catalytic Performance of Pt/CNT for Selective Hydrogenation of o-Chloronitrobenzene JIA Yongtao;WANG Chuang;LIANG Changhai;QIU Jieshan;* 2009, 30 (10):  1029-1034.  Abstract ( 2300 )   [Full Text(HTML)] () PDF (12774KB) ( 890 )   Pt/CNT (carbon nanotube) catalysts were prepared by the ethylene glycol reduction method through chemical modification and physical modification of CNT. The catalytic performance of the Pt/CNT for hydrogenation of o-chloronitrobenzene was tested. An acid mixture of H2SO4-HNO3 was used for chemical modification and sodium dodecyl sulfate (SDS) was used for physical modification. The catalysts were characterized by X-ray diffraction, transmission electron microscopy, inductively coupled plasma-atomic emission spectroscopy, H2-temperature programmed desorption, Fourier transform infrared spectroscopy, and elemental analysis. Both chemical modification and physical modification of CNT can result in functional groups that are beneficial to the dispersion and the nucleation of Pt particles, leading to improved catalytic performance of the catalyst. In the case of SDS modification, SDS formed micellar structure first, in which the nucleation and growth of Pt particles took place, leading to the formation of Pt particles with controllable morphology.

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Synthesis of Hierarchical ZSM-5 Zeolite and Performance of Its Mo-Based Catalyst for Methane Dehydroaromatization YU Suxia;YANG Jianhua*;CHU Naibo;LI Gang;LU Jinming;WANG Jinqu* 2009, 30 (10):  1035-1040.  Abstract ( 2260 )   [Full Text(HTML)] () PDF (5535KB) ( 1208 )   A hierarchical spherical-like ZSM-5 zeolite was synthesized using multiwall carbon nanotubes as secondary template. First, the nanotubes were purified by reflux with concentrated hydrochloric acid for 24 h. This purification step was repeated until the hydrochloric acid was no longer colored by impurities from the nanotubes (typically 3–4 times). Then the disposed nanotubes were added into the synthesis solution of ZSM-5, which was obtained by mixing H2O, tetraethylorthosilicate, Al(C3H8O)3, and tetrapropylammonium hydroxide (TPAOH). Afterward, this mixture was subjected to crystallization at varying temperatures. The obtained products were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, and nitrogen adsorption analysis. The results indicated that ZSM-5 zeolite with uniform size of 300–400 nm was synthesized, and it was spherical-like aggregates and has hierarchical structure constructed by many ZSM-5 nanotubes of 20–40 nm. The hierarchical ZSM-5 zeolite was modified to form a Mo/HZSM-5 catalyst, and its catalytic performance for methane dehydroaromatization was investigated. The modified Mo/HZSM-5 catalyst exhibited CH4 conversion as high as 19% and better life time. The CH4 conversion was kept at 10% even when the reaction time was 24 h. It is suggested that hierarchical structure was favorable for the enhancement of catalyst performance, which is due to the presence of both micropores and mesopores.

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Distribution of Cu Ions in Lanthanum-Modified CuHY Zeolite and Its Influence on Adsorption Desulfurization Performance FAN Minguang;LI Bin;*;ZHANG Feiyue;FANG Jinlong;LI Wangliang;XING Jianmin;LIU Zili 2009, 30 (10):  1041-1048.  Abstract ( 1985 )   [Full Text(HTML)] () PDF (509KB) ( 871 )   The Cu-loaded CuHY and CuLaHY zeolites were prepared by an incipient wetness method under nitrogen gas atmosphere. The samples were characterized by X-ray diffraction (XRD), N2 adsorption, NH3 temperature-programmed desorption, and X-ray photoelectron spectroscopy. The crystalline structure and the distribution of Cu2+ cations in the cages of Y zeolite were determined by XRD. The adsorption desulfurization performance of the zeolites was investigated for model diesel containing dibenzothiophene (DBT). The results showed that most of Cu species from the precursor CuCl2 was ion-exchanged with the HY and LaHY zeolites. For the La3+-modified CuHY zeolite (CuLaHY), the Cu2+ cations entering the supercages of the zeolite coordinated with both skeleton-oxygen atoms and water molecules, and thus being firmly situated at the sites SII and SIII in the supercages. For the CuHY zeolite, however, Cu2+ cations entering the supercages were only near the sites SII and SIII in the supercages. A very small percentage of CuCl molecules was highly scattered in the cages of the Y zeolite, with no definite position. The Cu2+ cations at the sites SII and SIII in the supercages adsorbed DBT molecules in the model diesel were the centers of adsorption desulfurization. The desulfurization capacity of the CuLaHY zeolite was better as compared with the CuHY zeolite. However, naphthalene molecules will result in competitive adsorption with DBT molecules if there are naphthalene molecules in the model diesel.

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Catalytic Cracking of 1-Hexene to Propylene Using SAPO-34 Catalysts with Different Bulk Topologies Zeeshan NAWAZ;TANG Xiaoping;ZHU Jie;WEI Fei;*;Shahid NAVEED 2009, 30 (10):  1049-1057.  Abstract ( 2152 )   [Full Text(HTML)] () PDF (3462KB) ( 1127 )   Three SAPO-34 catalysts, 100% SAPO-34, 30% SAPO-34, and meso-SAPO-34, with different bulk topologies were prepared. The catalysts were characterized by N2 adsorption, scanning electron microscopy, X-ray diffraction, and infrared spectroscopy techniques. The pore size, total acidity, and internal cage structure of the catalysts were almost identical, but they had different bulk appearances. The role of the bulk topology/structure of the catalysts was studied using 1-hexene cracking. On 30% SAPO-34, the surface acidity and diffusion rate decreased due to blocking by binder, which adversely affected catalytic activity. 100% SAPO-34 gave better cracking ability and higher propylene selectivity because of suitable acid sites and effective shape selectivity, respectively. In order to study the effect of diffusion, meso-SAPO-34 was used. The different bulk structure gave different feed conversion and selectivity profiles. A superior control of the stereochemistry was observed in the cracking by the meso-SAPO-34 and 100% SAPO-34 catalysts, in which enhanced diffusion mass transport played an appreciable role. Most of the propylene was produced by the direct cracking pathway by the β-scission carbenium ion mechanism. Hydrogen transfer reactions became significant at higher conversions. Decreasing the residence time to a certain extend is an appropriate way to obtain high propylene yield and selectivity. Activity and selectivity patterns for 1-hexene cracking to propylene were compared to justify superior SAPO-34 topology for 1-hexene cracking to propylene.

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Optical Properties of ZnO Nanotubes and Their Photocatalytic Activity for Degradation of Methyl Orange LI Changquan;LUO Laitao;*;XIONG Guangwei 2009, 30 (10):  1058-1062.  Abstract ( 2525 )   [Full Text(HTML)] () PDF (2563KB) ( 1274 )   ZnO nanotubes were synthesized by the hydrothermal method using sodium dodecyl sulfate as the template, and ZnO nanopartides were prepared with urea and ZnSO4 as raw materials. The optical properties and photocatalytic activity of ZnO nanotubes and nanoparticles were studied, and the samples were characterized by transmission electron microscopy, X-ray diffraction, photoluminescence spectroscopy, Raman spectroscopy, specific surface area determination, Fourier transform infrared spectroscopy, and ultraviolet-visual diffuse reflection spectroscopy. The ZnO nanotubes had larger specific surface area than the ZnO nanoparticles. The absorption peak of ZnO nanotubes began to appear at λ ≈ 650 nm, but the ZnO nanoparticles nearly had no absorptive capacity in the visible band. ZnO nanotubes and nanoparticles can degradate methyl orange under ultraviolet light, and the catalytic activity of ZnO nanotubes was greater than that of ZnO nanoparticles. With the increase in the catalyst amount and illumination time, the degradation rate of methyl orange increased. Increasing the methyl orange concentration reduced the degradation rate.

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Effect of Pt/C-RuO2 on Improvement of Dynamic Response of Proton Exchange Membrane Fuel Cells HAN Yakun;XU Hongfeng*;LU Lu 2009, 30 (10):  1063-1067.  Abstract ( 1799 )   [Full Text(HTML)] () PDF (2586KB) ( 954 )   The Pt/C-RuO2 catalyst samples were prapared by deposition of hydrated RuO2 on the carbon-supported Pt (Pt/C) catalyst. The cyclic voltammetry and multi-potential steps chronoamperometry results showed that the double layer capacitance of the catalyst samples increased after adding RuO2. The test result of single cell for proton exchange membrane fuel cell (PEMFC) showed that, compared with the Pt/C catalyst, there was a slight loss in cell performance when the mass fraction of RuO2 was lower than 8%. The result of voltage dynamic response to different current steps showed that the voltage of the Pt/C-RuO2 catalyst single cell for PEMFC was more steady than that of Pt/C catalyst, which indicated that RuO2 could buffer the voltage falling when the current increased instantly.

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Catalytic Performance of Cu2(OH)3Cl Catalysts Supported on Various Supports for Methanol Oxidative Carbonylation WANG Ruiyu;LI Zhong*;ZHENG Huayan;XIE Kechang 2009, 30 (10):  1068-1072.  Abstract ( 2450 )   [Full Text(HTML)] () PDF (1338KB) ( 965 )   Supported Cu2(OH)3Cl catalysts were prepared by the slurry impregnantion method and used in MeOH oxidative carbonylation to dimethyl carbonate (DMC). The catalytic activity of Cu2(OH)3Cl supported on various supports was higher than that of supported CuCl2, and active carbon (AC) was the suitable support because of its larger specific surface area. Cu2(OH)3Cl/AC (w(Cu) = 18.71%) exhibited excellent catalytic performance. MeOH conversion, DMC selectivity, and DMC space time yield were 6.93%, 67.3%, and 139.13 mg/(g·h), respectively, and the catalyst was more stable. The supported catalysts were characterized by CO-temperature programmed desorption, X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy, showing that the higher dispersion of Cu2(OH)3Cl in Cu2(OH)3Cl/AC was getting worse and transformed to CuCl2 and CuO during the reaction, resulting in the decrease of catalytic activity. The unique CuⅡ species in the fresh catalyst transferred into CuI species partially during the reaction.