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Chinese Journal of Catalysis
2008, Vol. 29, No. 4
Online: 25 April 2008

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Photocatalytic Splitting of H2S to Produce Hydrogen by Gas-Solid Phase Reaction MA Guijun;YAN Hongjian;ZONG Xu;MA Baojun;JIANG Hongfu;WEN Fuyu;LI Can* 2008, 29 (4):  313-315.  Abstract ( 2101 )   [Full Text(HTML)] () PDF (200KB) ( 1118 )   Hydrogen production by gas-solid phase photocatalytic splitting of H2S was investigated on five semiconductor photocatalysts including TiO2, CdS, ZnS, ZnO, and ZnIn2S4. ZnS shows the highest rate of hydrogen production under the identical conditions. Loading Ir on ZnS can effectively promote the hydrogen production. The addition of Cu2+during the ZnS preparation significantly enhances the photocatalytic activity of the catalyst for hydrogen production.

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Medium-Coupled Catalysts that Meet the Euro V Emission Standard for Gasoline Vehicles YAO Yanling;SHI Zhonghua*;SONG Weicong;YUAN Shuhua;GONG Maochu;CHEN Yaoqiang 2008, 29 (4):  316-318.  Abstract ( 2223 )   [Full Text(HTML)] () PDF (192KB) ( 958 )   The Ce0.65Zr0.25Y0.07La0.03O1.95oxygen storage material and La-stabilized alumina (La-Al2O3) were prepared. After aging at1000℃ for5 h, Ce0.65Zr0.25Y0.07La0.03O1.95maintains excellent textural and oxygen storage properties, and after calcination at 900 ℃ for4 h, La-Al2O3 has superior textural properties. Medium-coupled Pt-Pd-Rh monolithic catalysts were prepared by impregnating Ce0.65Zr0.25Y0.07La0.03O1.95and La-Al2O3 with Pt(NO3)2, Pd(NO3)2, and Rh(NO3)3 solutions and then washcoating on the cordierite honeycomb. The medium-coupled catalysts show high low-temperature activity and good thermal stability. The results from the emission test of a JETTA-MT vehicle show that the catalysts can meet EuroⅤ emission requirements.

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Oligomerization of Butene-2 over HZSM-5 Zeolite LIU Shu;;LI Chunlin;LIU Guangyu;ZHANG Dazhi;ZHANG Yangyang;SUN Xinde;LIU Zhongmin* 2008, 29 (4):  319-324.  Abstract ( 2158 )   [Full Text(HTML)] () PDF (397KB) ( 956 )   Oligomerization of butene-2 over HZSM-5 zeolite was carried out in a continuous flow fixed-bed reactor at210-300℃,3-5MPa, and0.5-1.5h-1of LHSV. The results showed that the reactions of butene-2 over the HZSM-5 zeolite and the content of higher molecular weight olefins in liquid products were influenced by temperature, pressure, and space velocity. The product was dominantly olefins at the reaction temperatures below 300 ℃, and the less branched structure of the product suggested shape-selective catalysis over HZSM-5. The acidity of the HZSM-5 zeolite influenced the activity and selectivity, and the zeolite with lower silica/alumina ratio enhanced the liquid yield and selectivity for higher olefins.

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Mechanism of CO Coupling to Dimethyl Oxalate over Pd/α-Al2O3 LIN Qian;JI Yang;TAN Junqing;XIAO Wende* 2008, 29 (4):  325-329.  Abstract ( 2481 )   [Full Text(HTML)] () PDF (359KB) ( 950 )   The reaction mechanism of CO coupling to dimethyl oxalate over Pd/α-Al2O3 was studied by in situ FT-IR spectroscopy. The adsorption of two reactants, CO and methyl nitrite, on the catalyst was observed. Methyl nitrite can easily catalytically dissociate into methanol, formaldehyde, and methyl formate. By changing the addition sequence of the two reactants into the in situ reactor, the process of the coupling reaction was clearly observed. The results show that bridged adsorbed CO reacts with free methyl nitrite gas, and the key step of the whole reaction is the CO adsorption.

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Effect of Graphitic Carbon on Stability of Pt/C Catalysts for Proton Exchange Membrane Fuel Cells LUO Xuan;HOU Zhongjun*;MING Pingwen;SHAO Zhigang;YI Baolian 2008, 29 (4):  330-334.  Abstract ( 2410 )   [Full Text(HTML)] () PDF (307KB) ( 1230 )   The effect of graphitic carbon on the stability of Pt/C catalysts for proton exchange membrane fuel cells was investigated. Vulcan XC-72 carbon black was graphitized at different temperatures, and the catalyst having a platinum loading of 20% was prepared by HCHO reduction-impregnation using the graphitic carbon as the support. Graphitic carbons were characterized byX-raydiffraction and nitrogen adsorption-desorption methods. The catalysts were characterized by an accelerated aging test and TG analyses. The results showed that the graphitization process started at1500℃, and the degree of graphitization increased with temperature, but the specific surface area of the carbons decreased gradually. The catalysts using the graphitic carbons as the support showed better electrochemical stability.

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Decomposition of Low-Level Ozone in Air over Activated Carbon-Supported Gold Catalyst ZHANG Jingjie;ZHANG Pengyi*;ZHANG Bo;WANG Junwei 2008, 29 (4):  335-340.  Abstract ( 2098 )   [Full Text(HTML)] () PDF (359KB) ( 1224 )   Activated carbon-supported gold catalysts were prepared by the incipient wetness method and characterized by N2 adsorption andX-rayphotoelectron spectroscopy. The catalyst activity for the decomposition of low-level ozone was evaluated, and the effects of pretreatment of activated carbon and post-treatment methods were investigated. Pretreatment of the activated carbon with dilute nitric acid and NaBH4 reduction could improve activity for ozone decomposition. The catalytic activity tests were conducted with feed gas of 45 mg/m3 ozone in air and relative humidity 60% at room temperature. The contact time was controlled at 0.06 s. The ozone removal ratio was maintained at 100% in the beginning1000min when the support was pretreated with HNO3 and NaBH4 and the catalyst was reduced with H2. Then it slowly dropped off to 97% in the following5000min. After pretreatment of the support by NaBH4, the specific surface area, pore volume, and elemental C fraction increased, but oxygen-containing groups decreased. This might be responsible for the improvement of catalytic activity. After gold was supported on the activated carbon, the catalyst surface area and pore volume further increased. However, the graphitic carbon fraction decreased whileC-Oand COO-groups increased. After reaction with ozone, the surface area and pore volume of samples as well as graphitic C content decreased, while the amount of C-O, COO-, andC=Ogroups increased. This indicated that activated carbon was catalyzed by gold to react with ozone and thereby ozone was decomposed.

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Acetylation Catalyzed by Functionalized Ionic Liquid [bmim]OTs LIU Lu;LIU Ye*;CAI Yueqin 2008, 29 (4):  341-345.  Abstract ( 2321 )   [Full Text(HTML)] () PDF (218KB) ( 923 )   The functionalized ionic liquid of 1-butyl-3-methylimidazolium toluene-p-sulfonate ([bmim]OTs) dissolved in 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF4) can efficiently catalyze the acetylation of benzyl alcohol under neutral reaction conditions. It shows high activity and stability even after recycling use ten times. A multicomponent ionic liquid system, [bmim]OTs-[bmim]BF4, exhibits good universality to various substrates such as alcohols (primary, secondary, and tertiary), phenols, and amines. The formed intermediate of AcOTs derived from the reaction between [bmim]OTs and acetic anhydride (Ac2O) is the catalytically active species with the supportive information from13CNMR analysis.

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Au/Fe2O3 Water-Gas Shift Catalyst Prepared by Modified Deposition-Precipitation Method LI Jinwei;ZHAN Yingying;ZHANG Fengli;LIN Xingyi;ZHENG Qi 2008, 29 (4):  346-350.  Abstract ( 2806 )   [Full Text(HTML)] () PDF (401KB) ( 913 )   The Au/Fe2O3 catalyst was prepared by co-precipitation, deposition-precipitation, and modified deposition-precipitation methods and was characterized byX-raydiffraction,X-rayphotoelectron spectroscopy, and transmission electron microscopy. The catalyst activity for the water-gas shift (WGS) reaction was discussed. Under strictly controlled conditions, the Au/Fe2O3 catalyst prepared by modified deposition-precipitation displayed higher activity for the WGS reaction than that prepared by co-precipitation and deposition-precipitation. In the former case, the CO conversion of 82.3% was obtained with a feed gas of 10%CO/N2 at 150 ℃. Wherein, gold particles of 3-5 nm were highly dispersed on the surface of the Fe2O3 support that existed in an amorphous and crystalline state. A relatively strong interaction between gold particles and the support occurred, which was beneficial for the WGS reaction.

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Immobilization of L-Proline on SBA-15 and Its Application in Asymmetric Mannich Reaction SUN Caixia;LI Haigang;WU Haihong*;LIU Yueming;WU Peng 2008, 29 (4):  351-355.  Abstract ( 2095 )   [Full Text(HTML)] () PDF (351KB) ( 809 )   The novel Pro/SBA-15 catalyst was prepared using SBA-15 zeolite as the support to immobilize L-proline (Pro) derivatives, which was synthesized from 4-hydroxy-L-proline. The Pro/SBA-15 catalyst was characterized byX-raydiffraction, N2 adsorption-desorption, scanning electron microscopy, and infrared spectroscopy. The catalytic performance of the catalyst was measured for asymmetric Mannich reaction. The results indicated that the mesoporous structure of SBA-15 was not affected by immobilization, however, the pore diameter, pore volume, and BET surface area were decreased. The Pro/SBA-15 catalyst had higher catalytic activity and enantioselectivity. Using 4-nitrobenzaldehyde as the reactant, the Mannich reaction product was obtained with high yield (80%) and moderate enantioselectivity (ee=60%). The supported catalyst could be easily separated from the reaction system and reused at least four times without loss of activity and enantioselectivity.

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Synthesis and Characterization of Silicon-Doped Mesoporous SO2-4/TiO2 without Using Organic Templates CHEN Yaohan;SHEN Jun;ZHANG Zhao* 2008, 29 (4):  356-360.  Abstract ( 2239 )   [Full Text(HTML)] () PDF (355KB) ( 793 )   Mesoporous metatitanic acid was prepared from industrial TiOSO4 solution without using templates. Then Si-doped mesoporous SO2-4/TiO2 with high thermal stability was synthesized by impregnating mesoporous metatitanic acid with tetraethylorthosilicate solution and calcination. The calcined samples were characterized usingX-raydiffraction, N2 adsorption and desorption, scanning electron microscopy,X-rayphotoelectron spectroscopy, and infrared spectroscopy. The photocatalytic activity of Si-doped SO2-4/TiO2 for the degradation of methylene blue was tested. Tetraethylorthosilicate that was adsorbed in the pores of metatitanic acid formedTi-O-Sibond by reaction withfree-OHon the pore walls of metatitanic acid during calcination. Silicon atoms introduced into the framework of TiO2 act as the pore structure support, and thus the thermal stability of mesoporous SO2-4/TiO2 was improved. The sample calcined at 700 ℃ for2 hhad a surface area of 189 m2/g and an average pore diameter of 2.8 nm. The photocatalytic activity of the sample calcined at 400 ℃ was excellent.

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Preferential Selective Oxidation of CO in H2-Rich Gas: Effect of Interaction between Au and Supports ZHANG Qijian*;QI Ping;ZHOU Yingchun 2008, 29 (4):  361-365.  Abstract ( 2441 )   [Full Text(HTML)] () PDF (347KB) ( 951 )   The catalytic performance of Au/Fe2O3, Au/Co3O4, Au/ZrO2, and Au/ZrO2-CeO2 catalysts for preferential oxidation of CO (CO PROX) was investigated, and the catalysts were characterized by high resolution transmission electron microscopy,X-raydiffraction, andX-rayphotoelectron spectroscopy. The effect of the interaction between Au and the supports on the electronic properties of Au was discussed. CO was totally converted at the temperature not higher than 60 ℃ over Au/Fe2O3 catalyst, and the selectivity for CO PROX was about 50%; while the other catalysts showed worse catalytic performance. The positive inductive effect of supports (such as Fe2O3 and Co3O4), which could make Au bearing some positive charge, was supposed to be the key factor for the catalyst activity in CO PROX. The catalyst activity could be improved by choosing or modifying the supports to get suitable positive charge of Au.

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Study of Ethylene and Benzene Adsorption on Brnsted Acid Sites in MCM-22 Zeolites by Theoretical Calculation NI Dan;ZHOU Danhong*;ZHANG Jia 2008, 29 (4):  366-372.  Abstract ( 2187 )   [Full Text(HTML)] () PDF (422KB) ( 955 )   The ONIOM method was used to perform the computational study on the acid strength of double acid sites in the 12 member-ring of MCM-22 zeolite. The calculation was carried out by the B3LYP/6-31G**/MNDO method based on the 52T cluster model. The dependency of the acid strength on the interval distance of the framework Al atoms was examined, and the adsorption of ethylene and benzene on the adjacent acid sites was investigated. The calculation results indicated that when two acid sites existed near each other and spaced out by one Si atom, the acidity descends obviously with respect to the isolated acid site. If the Si atom number between two framework Al atoms increases, the acidity rises up. When the Si atom number is more than three, the acid strength reaches a steady value, being equivalent to the isolated system. For C2H4 adsorption, its adsorption energy in all cases is 31-35 kJ/mol, independent on the interval distance between the framework Al atoms. For C6H6 benzene adsorption, its adsorption energy on next nearest neighbour acid sites is higher than that on single acid site, and when the Si atom number is more than three, its adsorption energy is 21-29 kJ/mol. The adsorption energy of either two C2H4 molecules or two C6H6 molecules at the adjacent acid sites is equivalent to that of single molecule on the isolated acid site. The natural bond orbital analysis for the adsorption complexes ascertained their electronic structure, and the nature of C2H4 and C6H6 adsorption on the acid sites was explored.

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Pd/Ce0.8Zr0.2O2/Substrate Monolithic Catalyst for Toluene Catalytic Combustion ZHANG Qingbao;ZHAO Leihong*;TENG Botao;XIE Yunlong;YUE Lei 2008, 29 (4):  373-378.  Abstract ( 2188 )   [Full Text(HTML)] () PDF (507KB) ( 891 )   A novel Ce0.8Zr0.2O2 washcoat has been prepared by an impregnation method and used as a host for the active Pd component to prepare a Pd/Ce0.8Zr0.2O2/substrate monolithic catalyst for toluene catalytic combustion. Thermogravimetry and differential scanning calorimetry, scanning electron microscopy,X-raypowder diffraction, N2 adsorption, Raman spectroscopy, and CO temperature-programmed reduction have been used to characterize the catalyst. The washcoat is uniform and shows strong adhesion to the substrate according to an ultrasonic test. A toluene conversion of 97% is obtained at a temperature as low as 210 ℃ over the Pd/Ce0.8Zr0.2-O2/substrate monolithic catalyst calcined at 400 ℃. The formation of CeO2-ZrO2 solid solution and the presence of the stable PdO phase at high temperatures are primarily responsible for the good thermal stability of the monolithic catalyst.

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Acidity and Isomerization Activity of SAPO-11 Synthesized by an Improved Hydrothermal Method LIU Ping;REN Jie;SUN Yuhan* 2008, 29 (4):  379-384.  Abstract ( 2439 )   [Full Text(HTML)] () PDF (387KB) ( 1017 )   Medium-pore molecular sieve SAPO-11 was synthesized using an improved hydrothermal method, which involves programmed heating of the synthesis gel in the presence of isopropanol. Products were characterized usingX-raydiffraction, scanning electron microscopy, N2 adsorption, ammonia temperature-programmed desorption, infrared spectroscopy of adsorbed pyridine, and29Sisolid-state MAS NMR. The results indicated that the SAPO-11 sample synthesized by this method showed higher crystallinity, smaller particle size, and larger micropore volume than that prepared by the conventional hydrothermal method. Furthermore, the numbers of total acid sites and medium strength acid sites were also enhanced. In the hydroisomerization of n-tetradecane, the Pt/SAPO-11 catalyst thus exhibited high activity and selectivity for isomers.

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Effect of Promoters on the Catalytic Activity of MCM-41 with High Copper Content in Benzene Hydroxylation KONG Yan*;XU Xinjie;WU Yong;ZHANG Rui;WANG Jun* 2008, 29 (4):  385-390.  Abstract ( 2202 )   [Full Text(HTML)] () PDF (314KB) ( 764 )   Cu-MCM-41 with a high copper content up to 26.0% showed excellent catalytic activity in the direct hydroxylation of benzene with hydroperoxide. The effects of various kinds of heteroatoms on the catalytic activity were studied. The introduction of a small amount of acidic promoters such as B and Al can enhance phenol selectivity to 100%. Some redox promoters such as V and Cr increase the conversion of benzene slightly, whereas other elements such as Ti and Zr inhibit the catalytic activity of catalysts. The reasons for these influences were briefly discussed according to the radical mechanism.

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Preparation, Characterization and Photocatalytic Performance of Porous TiO2 Micro-beads WANG Xiaojing;LIU Chao;HU Zhonghua*;LIU Yafei;CHEN Yujuan;WEN Zubiao 2008, 29 (4):  391-396.  Abstract ( 2538 )   [Full Text(HTML)] () PDF (382KB) ( 1586 )   Nanocrystal and porous TiO2 microbeads with high surface area and narrow pore size distribution were prepared by sol-gel technique in the presence of Lutensol TO series (iso-tridecanol) polyoxyethylene ether nonionic surfactants. The resultant TiO2 microbeads were characterized by TEM, SEM, TG-DSC, XRD, and N2 adsorption. The photocatalytic performance of TiO2 microbeads was evaluated through degradation of methylene blue and compared with the commercial Degussa P25 nano-TiO2. The results showed that at optimal treatment temperature of 425 ℃, anatase-type TiO2 microbeads with particle size of0.7-1.0μm were obtained. The microbeads have porous structure with a BET specific surface area of 70.5 m2/g, total pore volume of 0.12 cm3/g, average pore diameter of 4.26 nm, and crystal size of 12 nm. The TiO2 microbeads exhibited similar photocatalytic activity to Degussa P25 for the degradation of methylene blue.

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Reaction Factors and Kinetics of Degradation of Malachite Green with Novel Biomimetic Photocatalyst HMS-FePcS GAO Guandao;ZHANG Aiyong;ZHANG Meng;CHEN Jinlong;ZHANG Quanxing 2008, 29 (4):  397-402.  Abstract ( 2118 )   [Full Text(HTML)] () PDF (343KB) ( 852 )   A novel catalyst, HMS-FePcS, prepared by modifying HMS molecular sieve with iron sulfophthalocyanine (FePcS) was found to be highly effective for the degradation of nonbiodegradable malachite green upon visible light irradiation in the presence of H2O2. Influencing factors including temperature, light energy, dosages of the catalyst and H2O2, and active centers were investigated. The experimental data of kinetics from optimum conditions indicated that the reaction is zero order in the initial stage and first order in the second stage. A rational explanation was suggested according to the Langmuir-Hinshelwood model.

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Kinetic Resolution of 2-Octanol by Esterification with Mycelium-Bound Lipase from Rhizopus chinensis SHAN Tianyu;WANG Dong;XU Yan*;HE Junyao 2008, 29 (4):  403-408.  Abstract ( 2336 )   [Full Text(HTML)] () PDF (294KB) ( 956 )   The application of mycelium-bound lipase from Rhizopus chinensis CCTCC M201021 (RCL) to the kinetic resolution of 2-octanol by esterification in nonaqueous media was studied using octanoic acid and isooctane as the acyl donor and solvent, respectively. Water activity did not obviously affect the enantioselectivity of lipase but could notablely improve the initial velocity of the reaction. At the same conversion, the initial velocity of production of (R)-ester was increased by 7.3 times by the addition of3Amolecular sieves to reduce the water content of the system. When the substrate concentration was increased to 0.230 mol/L, (R)-ester was obtained with 44.4% conversion and 94.7% enantiomeric excess after reaction for40 h. Compared with three commercial lipases, RCL showed not only high enantioselectivity (E=103.1) but also more satisfied initial velocity and conversion.

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Catalytic Performance of MoVBiTeO/SiO2 for Selective Oxidation of Propane to Acrolein HE Yiming;YI Xiaodong;HUANG Chuanjing;WENG Weizheng*;WAN Huilin* 2008, 29 (4):  409-414.  Abstract ( 2068 )   [Full Text(HTML)] () PDF (381KB) ( 682 )   A series of MoVBiTeO/SiO2 catalyst samples with different Mo/V ratios were prepared by the impregnation method. The catalyst structure, reducibility, and acidity were characterized by XRD, Raman, XPS, TPR, and FT-IR techniques, and the catalytic performance of the catalyst for selective oxidation of propane to acrolein was evaluated. The results indicated that the interaction between Mo and V components modified the catalyst structure, and the redox cycle of V5++Mo5+V4++Mo6+was formed. The improvement in the reducibility of the catalyst might be responsible for the increase in propane conversion. The V and Mo components were responsible for B acid and L acid, respectively. When the Mo/V ratio increased, the amount of B acid decreased, and the catalyst selectivity for acrolein increased. Among the investigated catalyst samples, the sample with a Mo/V molar ratio of 6 exhibited the best catalytic performance.