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Chinese Journal of Catalysis
2007, Vol. 28, No. 11
Online: 25 November 2007

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A Microreactor Based on Sinter-Locked Microfibrous Media with Open Porous Structure for Nitration of Benzene LI Jianfeng;YANG Jiulong;WANG Miaomiao;LU Yong*;HE Mingyuan 2007, 28 (11):  931-933.  Abstract ( 1707 )   [Full Text(HTML)] () PDF (217KB) ( 1170 )   A microreactor with an integrated heat-exchanger has been developed for strongly exothermic liquid-liquid reactions on the basis of novel metallic microfibrous structure. The microreactor was made from simply inserting quadrate pieces of the microfibrous media in the reaction and heat-exchange chambers. This microreactor was examined in the use with the nitration of benzene. This new approach facilitates mass and heat transfer by taking the beneficial properties in terms of large void volume, three-dimensional micron-grade pore structure, and large surface area to volume ratio. Note that three-dimensional network structure acts as a micromixer thereby leading to micronic segmentation and fast mixing of fluids. The results showed that nitration of benzene could proceed completely in this novel microreactor with high selectivity at a short residence time. The selectivity of 99.4% to nitrobenzene was achieved with a benzene conversion of 91.7% at a residence time of30 sand 60 ℃.

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Asymmetric Cyclopropanation of β-(-)-Pinene Catalyzed by Copper Complexes LI Zhengning*;JIANG Lan;LIU Gailing;CHEN Huilin 2007, 28 (11):  934-936.  Abstract ( 1814 )   [Full Text(HTML)] () PDF (189KB) ( 1022 )   The asymmetric cyclopropanation of β-(-)-pinene with diazoacetate was performed in the presence of copper salicylaldehydate, copper diketonates, and copper-Schiff base complexes as the catalyst, respectively. The relationship between the stereoselectivity for the reaction and structure of the copper-Schiff base was studied, and high stereoselectivity was achieved.

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Synthesis of Diphenyl Carbonate via Transesterification Catalyzed by HMS Mesoporous Molecular Sieves Containing Heteroelements LUO Shuwen;CHEN Tong*;TONG Dongshen;ZENG Yi;LEI Yongcheng;WANG Gongying 2007, 28 (11):  937-939.  Abstract ( 2027 )   [Full Text(HTML)] () PDF (174KB) ( 1039 )   Heteroelements-containing mesoporous molecular sieves Me-HMS (Me=the incorporated metal) were prepared by the hydrothermal synthesis mothod and used for the synthesis of diphenyl carbonate (DPC) via transesterification between dimethyl carbonate (DMC) and phenol. Low angleX-raydiffraction patterns showed that all samples have typical of hexagonal phase structure. Among all tested Me-HMS samples, Ti-HMS exhibited the best catalytic performance, and the activity was closely related to the intra-framework Ti species content. When the molar ratio of Ti/Si in sol-gel reached 1/30, the amount of intra-framework Ti species in Ti-HMS was closed to saturation, and the maximum phenol conversion of 31.4% and the transesterification selectivity of 99.9% were obtained.

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Oxidative Decarboxylation of Carboxylic Acids with Tetrabutyl-ammonium Periodate Catalyzed by Manganese (Ⅲ) Meso-Tetraarylporphyrins: Effect of Metals, Meso-Substituents, and Anionic Axial Ligands Gholam Reza KARIMIPOUR*;Bahador KARAMI;Morteza MONTAZEROZOHORI;Saeed ZAKAVI 2007, 28 (11):  940-946.  Abstract ( 2163 )   [Full Text(HTML)] () PDF (370KB) ( 840 )   In association with tetrabutylammonium periodate (n-Bu4NIO4) and imidazole (ImH), manganese meso-tetraarylporphyrins have provided an effective catalytic system for the oxidative decarboxylation of carboxylic acids. Meso-tetraarylporphyrins bearing electron withdrawing and/or bulky aryl groups at meso-positions lowered the catalytic activity of the metalloporphyrins. Although the presence of ImH and the choice of the metal center are crucial for the catalytic properties of the metalloporphyrins, the counter ion plays an important role in this catalytic system. However, the best catalytic activity has been observed for the Mn(TPP)CN/n-Bu4NIO4/ImH system. A catalytic cycle is postulated, in which the oxidative decarboxylation of diphenylacetic acid involves the interaction of a high-valent Mn-oxo species with the substrate. Attempts have been made to visualize the possible interactions and electronic changes responsible for the formation of the corresponding carbonyl products.

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A Novel Glass Fiber-Supported Platinum Catalyst for Self-healing Polymer Composites: Structure and Reactivity YANG Haitang;FANG Zhengping;*;FU Xiaoyun;TONG Lifang; 2007, 28 (11):  947-952.  Abstract ( 1873 )   [Full Text(HTML)] () PDF (396KB) ( 1055 )   A platinum-based catalyst supported on glass fiber grafted with1,3,5,7-tetramethyl-1,3,5,7-tetravinyl cyclotetrasiloxane (D4Vi) was prepared and evaluated for the hydrosilylation reaction of styrene and methyldiethoxysilane. The silanization of the glass fiber was carried out with methyldichlorosilane. D4Vi was then anchored on the modified fiber withSi-Hbonds through a hydrosilylation reaction mediated by a Pt(0)-D4Vi complex solution catalyst. Fourier transform infrared spectroscopy, field emission scanning electron microscopy,X-rayenergy dispersion spectroscopy, and thermogravimetric data showed that D4Vi was covalently bonded onto the fiber surface. The very high density of D4Vi grafting confers a strong hydrophobic character to the modified fiber surface. Fairly good catalytic activity for the hydrosilylation reaction between styrene and methyldiethoxysilane was observed on this catalyst.

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Mesoporous CeO2-Supported Co3O4 Catalysts for CO Preferential Oxidation in H2-Rich Gases GUO Qiang;WU Meiling;LIU Yuan*;BAI Xue 2007, 28 (11):  953-957.  Abstract ( 2192 )   [Full Text(HTML)] () PDF (426KB) ( 924 )   Mesoporous ceria (meso-CeO2) and the mesoporous ceria-supported cobalt catalyst (Co3O4/meso-CeO2) were synthesized through a surfactant-templated method and used for CO preferential oxidation (PROX) in H2-rich gases. The N2 physical adsorption andX-raydiffraction techniques were used to study the textural properties and crystalline structure of the meso-CeO2 and Co3O4/meso-CeO2. It was found that Co3O4/meso-CeO2 exhibited very good catalytic performance for the PROX reaction at high space velocity, whereas CO2 and water had negative effects on CO conversion. In addition, the Co3O4/meso-CeO2 catalyst had a much wider temperature window for the complete conversion of CO than the Co3O4/non-mesoporous CeO2 catalyst.

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Effect of Crystal Form of TiO2 on Photocatalytic Decomposition of Gaseous Ozone over Au/TiO2 DONG Fang;YANG Dongmei;ZHANG Min;YANG Jianjun* 2007, 28 (11):  958-962.  Abstract ( 2316 )   [Full Text(HTML)] () PDF (310KB) ( 833 )   The Au/TiO2 photocatalysts were prepared by the deposition-precipitation method. Three different crystal forms of TiO2 were used as supports. The influence of crystal form of TiO2 on photocatalytic decomposition of gaseous ozone over Au/TiO2 was studied. The photocatalysts were characterized by ultraviolet-visible diffuse reflectance spectroscopy,X-rayphotoelectron spectroscopy (XPS), and surface photovoltage spectroscopy (SPS). The results showed that the photocatalytic activity of the catalysts was in the order Au/P25>Au/Anatase>Au/Rutile, in agreement with the order of the photocatalytic activity of pure TiO2. The photocatalytic activity of the catalysts increased obviously by loading Au. The results of Au 4f XPS showed that the ability of transferring electron from TiO2 to Au clusters was obviously different in three kinds of TiO2. The synergistic effect was responsible for the different activity of Au/TiO2. The SPS signals were consistent with photocatalytic activity: the stronger the SPS signal, the faster the separation rate of photoinduced electron-hole pairs, the higher the photocatalytic activity.

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Hydrothermal Synthesis and Crystallization Mechanism of a Novel Microporous Phosphate with Submicron Holes ZHANG Ying;TIAN Peng;ZHOU Fan;LIU Guangyu;LIU Zhongmin* 2007, 28 (11):  963-969.  Abstract ( 1973 )   [Full Text(HTML)] () PDF (653KB) ( 751 )   Microporous phosphate crystals with submicron holes, HAP-TAP, was hydrothermally prepared. HAP-TAP is composed of two different crystals, the hexagonal prism crystals and the layer crystals. Its morphology was characterized by abundant submicron holes (0.4-0.8 μm) distributing on the surface of hexagonal prism crystals and the layer crystals growing in the holes. The process of crystallization was investigated by scanning electronic microscopy, powderX-raydiffraction (XRD), infrared spectroscopy, and energy dispersiveX-ray(EDX) spectroscopy. The hexagonal prism single-crystal HAP was obtained by adjusting the crystallization time. The single-crystal XRD results showed that HAP is a novel microporous aluminum phosphate with a formula of Al5(OH)2(PO4)7(C2N2H10)3•0.5H2O and two-dimensional open-framework structure. EDX results showed that the layer crystals located in submicron holes were titanic aluminum phosphates.

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Effect of Support Composition on Catalytic Performance of PtSn/ZSM-5 Catalyst for Propane Dehydrogenation QIU Anding;LI Enxia;FAN Yining* 2007, 28 (11):  970-974.  Abstract ( 2006 )   [Full Text(HTML)] () PDF (307KB) ( 958 )   The effect of ZSM-5 composition on catalytic performance of the supported PtSn/ZSM-5 catalyst for propane dehydrogenation was studied using a microreactor combined with infrared spectroscopy of adsorbed pyridine, temperature-programmed desorption of NH3, thermogravimetry, H2 chemisorption, and temperature-programmed reduction. The results showed that the ZSM-5 composition exerted great influence on the catalytic performance of PtSn/ZSM-5 for propane dehydrogenation. With the increase of SiO2/Al2O3 molar ratio in theZSM-5support, the numbers of both total and stronger acidic sites decreased. When the SiO2/Al2O3 molar ratio in the ZSM-5 support increased from 45 to 108, the catalytic activity increased, and the amount of coke formed on the catalyst surface decreased. When the SiO2/Al2O3 molar ratio in the ZSM-5 support was higher than 304, the interaction of Sn species with the ZSM-5 support became weaker, and the ratio of Sn0 species in the catalyst increased after reduction in H2, resulting in the decrease of H2 uptake and catalytic activity of the PtSn/ZSM-5 catalyst for propane dehydrogenation.

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Hydrogenation of Quinoline Catalyzed by Ru Nanoparticle Catalyst CHEN Jun;XUE Fang;FU Haiyan;FAN Guangyin;YUAN Maolin;CHEN Hua*;LI Xianjun 2007, 28 (11):  975-979.  Abstract ( 2253 )   [Full Text(HTML)] () PDF (326KB) ( 1391 )   A highly dispersed Ru-containing catalyst (5%Ru/C) was prepared and characterized byX-raydiffraction,X-rayphotoelectron spectroscopy, and high resolution transmission electron microscopy. The results showed that ruthenium was reduced to zero valence, and the average particle diameter of Ru crystallites was smaller than 5 nm. The ruthenium-based catalyst exhibited the highest activity for the hydrogenation of quinoline compared with other activated carbon-supported catalyst. Under the optimum reaction conditions of 100 ℃,p(H2)=3.0 MPa, and Ru/quinoline molar ratio of 4/1000, the main product obtained was the partially hydrogenated1,2,3,4-tetrahydroquinoline, and the selectivity was up to 98.5%. The decahydroquinoline was not found in the products. However, after the fresh 5%Ru/C catalyst was added,1,2,3,4-tertrahydroquinoline was completely transformed to decahydroquinoline. The mechanism of quinoline hydrogenation was also discussed.

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Surface Acidity and Hydroxyl Groups of SBA-15 Mesoporous Silica Catalysts Containing Tungsten Species HU Linhua;JI Shengfu*;LIU Qianqian;WU Pingyi;ZHU Jiqin;LI Chengyue 2007, 28 (11):  980-986.  Abstract ( 2240 )   [Full Text(HTML)] () PDF (476KB) ( 1023 )   A series of SBA-15 mesoporous silica catalysts containing tungsten oxide were prepared by impregnation and hydrothermal methods, respectively. After temperature-programmed carburization in flowing CH4/H2, the SBA-15 mesoporous silica catalysts containing tungsten oxide are converted to the corresponding catalysts containing tungsten carbides. The surface acidity and hydroxyl groups of the catalysts were characterized using NH3-TPD and FT-IR spectroscopy, respectively. The NH3-TPD results show that the SBA-15 mesoporous silica catalysts containing tungsten oxide prepared by the impregnation method have weak acid sites of SBA-15 mesoporous silica, whereas the SBA-15 mesoporous silica catalysts containing tungsten carbides have strong acid sites of W2C besides the weak acid sites of SBA-15. However, the SBA-15 mesoporous silica catalysts containing tungsten oxide prepared by the hydrothermal method have increasing weak acid sites of SBA-15, whereas the SBA-15 mesoporous silica catalysts containing tungsten carbides have strong acid sites of W2C with lower W contents and strong acid sites of W2C and WC with higher W contents. The results of FT-IR show that there are α-, β-, and γ-hydrogen bond hydroxyl groups besides free silica hydroxyl groups in the SBA-15 mesoporous silica catalysts containing tungsten oxide and tungsten carbides. Moreover, the distribution of hydrogen bond hydroxyl groups is dependent upon the preparation process and tungsten content of the catalysts.

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Preparation of Chromium and Sulfur Co-doped TiO2 Photocatalysts and Their Photocatalytic Activity under Visible Irradiation Lv Yuan;NI Lingli;YANG Ping*;CAO Yong 2007, 28 (11):  987-992.  Abstract ( 2336 )   [Full Text(HTML)] () PDF (341KB) ( 1561 )   Pure and doped or co-doped TiO2 catalysts with various amounts of chromium and sulfur were obtained by the sol-gel process, in which tetrabutyl titanate was used as the precursor and chromium nitrate and thiourea as ion donors. Indigo carmine photodegradation experiments showed that the co-doped catalyst has higher photocatalytic activity than that of pure and single-doped ones. The co-doped catalyst with 0.60% (atomic ratio) chromium and 1.2% (atomic ratio) sulfur calcined at 500 ℃ has the highest catalytic efficiency under visible irradiation. The catalysts were characterized byX-raydiffraction, N2 adsorption,X-rayphotoelectron spectroscopy, and ultraviolet-visible diffuse reflectance spectroscopy. The results showed that the co-doped catalysts have anatase phase, higher specific area, and wide range of visible response. The higher visible light photocatalytic activity of the co-doped TiO2 is attributed to the doped chromium and sulfur. The doped chromium lowers the band gap and expands the absorption of visible light region, and the doped sulfur maintains the charge balance and enhances visible light absorption.

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Biocatalytic Synthesis of 2-Phenylethanol by Yeast Cells MEI Jianfeng;MIN Hang*;L Zhenmei 2007, 28 (11):  993-998.  Abstract ( 2322 )   [Full Text(HTML)] () PDF (318KB) ( 1339 )   The biocatalytic activity of 13 yeast strains was compared for the synthesis of 2-phenylethanol, and a Saccharomyces cerevisiae strain that had high biocatalytic activity was screened out. The experiments of single factor and orthogonal design were carried out to optimize the composition of the medium for the biosynthesis of 2-phenylethanol. The results showed that the concentration of 2-phenylethanol could reach 4.654 g/L with a molar yield of 0.63 in the optimized medium. Furthermore, a model of polynomial regressive equation between the 2-phenylethanol concentration and main components in the medium was established after the Box-Behnken central composite design and response surface methodology were put into practice. The model exhibited fine exactitude and provided a predictive model for optimizing the medium in the biocatalytic synthesis of 2-phenylethanol. Response surface analysis was applied to optimize the medium constituents, and upon applying the optimized medium, the maximum 2-phenylethanol concentration of 4.815 g/L was achieved in testing experiment.

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Organic Modification of SiO2 and Its Influence on the Properties of Co-Based Catalysts for Fischer-Tropsch Synthesis SHI Lihong;LI Debao;HOU Bo;SUN Yuhan* 2007, 28 (11):  999-1002.  Abstract ( 2057 )   [Full Text(HTML)] () PDF (264KB) ( 1238 )   SiO2 was modified by various organic groups before the impregnation of the cobalt precursor. These modified supports and the corresponding catalysts were characterized by IR spectroscopy,X-raydiffraction, and temperature-programmed reduction. The results showed that the organic modification of SiO2 reduced the surface silanol (Si-OH) concentration of SiO2 support, suppressed the interaction between cobalt and silica, enhanced the reduction of the supported cobalt, and thus increased the catalytic activity of Co catalysts for Fischer-Tropsch synthesis. Moreover, SiO2 modified by different organic groups had different surface silanol concentration due to steric hindrance and the catalytic activity increased with the decrease of surface silanol concentration.

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Liquid-Phase Selective Oxidation of Styrene under Mild Conditions over Modified VPO Catalyst LIU Junhua;WANG Fang;LIU Yanxia;XU Xianlun* 2007, 28 (11):  1003-1008.  Abstract ( 1928 )   [Full Text(HTML)] () PDF (363KB) ( 985 )   Styrene epoxidation was carried out using styrene as the row material, molecular oxygen as the oxidant, and modified vanadium phosphorus oxide as the catalyst. The results showed that sliver significantly increased the overall activity for the selective oxidation of styrene to styrene oxide. To investigate the silver effect, the catalysts were characterized usingX-raydiffraction, Fourier transform infrared spectroscopy,X-rayphotoelectron spectroscopy, and electron microscopy. The P/V ratio plays a crucial role in the activity and the selectivity of the catalyst. Other factors, such as the metallic constituent, solvent, and reaction temperature, were also studied. Under the optimal conditions (i.e., Ag-VPO as the catalyst, CH3CN as the solvent, 65 ℃), the conversion of styrene is 47.3%, and the selectivity for styrene oxide is up to 98.0%.

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Condensation of iso-Butanal and tert-Butyl Alcohol Catalyzed by Brønsted Acidic Ionic Liquids SHEN Jianghan;WANG Hua;SUN Ying;LIU Hongchao;LIU Zhongmin* 2007, 28 (11):  1009-1012.  Abstract ( 2140 )   [Full Text(HTML)] () PDF (250KB) ( 700 )   Catalytic synthesis of2,5-dimethyl-2,4-hexadiene by Prins condensation of iso-butanal and tert-butyl alcohol was investigated using Brønsted acidic ionic liquids as both catalyst and solvent. It was found that all the ionic liquids were active for Prins condensation. After reaction, the upper organic phase could be easily separated from the ionic liquid by decantation. The ionic liquids could be reused in the next run by heat treatment under vacuum. Manipulating the structure of ionic liquids with respect to the organic cation or the organic/inorganic anion had great effects on the catalytic performance of the ionic liquids.

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Influence of CO2 Addition on Catalytic Performance of Fe-Mn Catalyst for Fischer-Tropsch Synthesis LIU Ying;WANG Yu;HAO Xu;LI Ying;BAI Liang;XIANG Hongwei;XU Yuanyuan*;ZHONG Bing;LI Yongwang 2007, 28 (11):  1013-1018.  Abstract ( 1907 )   [Full Text(HTML)] () PDF (280KB) ( 920 )   The effect of CO2 addition during Fischer-Tropsch synthesis was investigated over the Fe-Mn catalyst in a fixed-bed reactor. The CO2 addition enhanced the reverse reaction rate of the water-gas shift and inhibited the CO2 formation rate. The CO2 selectivity decreased rapidly when a large amount of CO2 was added into the feed gas (n(H2)/n(CO)=2.03, GHSV (H2+CO)=4010h-1, p(total)=1.50 MPa, T=533 K), while the hydrocarbon formation rate decreased slightly and the overall oxygenate formation rate decreased. Under the reaction conditions ofn(H2)/n(CO)=1.00, GHSV (H2+CO)=8000h-1, p(H2+CO)=1.50 MPa, and T=593 K, the CO2 addition decreased the surface hydrogen concentration, leading to an increase in olefin/paraffin ratio and higher C5+selectivity in reaction products. The hydrocarbon formation rate appreciably increased with increasing CO2 partial pressure, and the hydrocarbon yield also gradually increased. In addition, the oxygenate formation rate also increased with CO2 partial pressure.

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CO2 Reforming of CH4 over Mesoporous Ni/CaO-ZrO2 Nanocomposite LIU Shuigang;LI Junping;ZHAO Ning;WEI Wei;SUN Yuhan* 2007, 28 (11):  1019-1023.  Abstract ( 1945 )   [Full Text(HTML)] () PDF (349KB) ( 880 )   A novel mesoporous Ni/CaO-ZrO2 nanocomposite was prepared by a the sol-gel method. The nanocomposite was used for CO2 reforming of CH4, and it exhibited high catalytic activity, thermal stability, and resistance to coking. After running in the fixed-bed reactor for50 h, its catalytic activity hardly decreased, and only a small amount of carbon formed on the catalyst, meaning that the catalyst stability was better than Ni/Al2O3 or Ni/SiO2 catalyst. The nickel particles almost kept their original nanometer size during the reaction owing to that the size growth was inhibited by other components in the nanocomposite. In addition, CaO was favorable for the chemisorption of CO2 in the reaction and consequently improved the resistance to carbon deposition on the mesoporous Ni/CaO-ZrO2 nanocomposite.