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Chinese Journal of Catalysis
2006, Vol. 27, No. 8
Online: 25 August 2006

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Preparation of a Pt-Rh Close Coupled Catalyst and Its Catalytic Performance for Controlling AutomobileExhaust Emission SHI Zhonghua, GONG Maochu, CHEN Yaoqiang 2006, 27 (8):  647-649.  Abstract ( 1722 )   [Full Text(HTML)] () PDF (192KB) ( 683 )   A noble Pt-Rh close coupled catalyst supported on a novel high surface area alumina was prepared to control the exhaust gas emission of automobiles. The results indicated that the prepared catalyst has good activity at low temperature and good stability at high temperature, which can satisfy the requirements of a high performance close coupled catalyst.

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Low-Temperature Hydrolysis of Dimethyl Ether over Cu-Pd/MCM-22 Catalyst FANG Yiwen1,2, SONG Yibing2, SUN Changyong2, WANG Wenjin2, GUO Ruihua2, LIN Weiming1 2006, 27 (8):  650-652.  Abstract ( 2226 )   [Full Text(HTML)] () PDF (232KB) ( 712 )   The catalytic performance of various zeolite catalysts for dimethyl ether (DME) hydrolysis was investigated. The aim is to obtain a highly active catalyst for hydrolysis of DME at low temperature, which can be coupled with the Cu-Pd/AC catalyst to construct a bifunctional catalyst for coupling the DME hydrolysis with methanol carbonylation. The results showed that the acidic zeolite catalysts HZSM-5 and MCM-22 exhibited DME hydrolysis activity at relatively low temperatures. Compared with HZSM-5, the good accessibility of the strong Bronsted acid sites located in MCM-22 super cages was responsible for higher conversion of DME. Further improvement in the catalytic activity was found on the MCM-22 catalyst modified by transition metals Pd and Cu.

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Low Temperature Oxidative Coupling of Methane over a La2O3 Catalyst WANG Lihua, YI Xiaodong, WENG Weizheng, WAN Huilin 2006, 27 (8):  653-655.  Abstract ( 2133 )   [Full Text(HTML)] () PDF (195KB) ( 679 )   The oxidative coupling of methane could take place at 723 K over the La2O3 catalyst prepared by the precipitation method, which was about 100 K lower than the startup temperature over the commercial La2O3 catalyst. Under the conditions of 723 K, CH4/O2 molar ratio of 3, and GHSV=7?500 ml/(g•h), the conversion of methane and selectivity for C2 hydrocarbons reached 26.6% and 40.8%, respectively. The characterization results showed that there was only hexagonal La2O3 over the two catalyst samples, but the catalyst prepared by precipitation had a larger specific surface area and a distinct desorption peak of adsorbed O2 at 598 K.

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Highly Efficient Synthesis of Epichlorohydrin by Epoxidation of Allyl Chloride over Titanosilicate Ti-MWW WANG Lingling, LIU Yueming, ZHANG Haijiao, WU Haihong, JIANG Yongwen, WU Peng*, HE Mingyuan 2006, 27 (8):  656-658.  Abstract ( 1913 )   [Full Text(HTML)] () PDF (157KB) ( 933 )   Liquid-phase epoxidation of allyl chloride with hydrogen peroxide was carried out over Ti-MWW, a novel titanosilicate with the MWW structure, to synthesize epichlorohydrin selectively and effectively. Ti-MWW proved to be superior to the conventional TS-1 catalyst in both catalytic activity and product selectivity. Ti-MWW prefers aprotic solvents of acetone and acetonitrile, both of which can restrain the solvolysis of epichlorohydrin, whereas TS-1 favors a protic solvent of methanol. It is possible to achieve the conversion of allyl chloride and selectivity for epichlorohydrin as high as 99% on Ti-MWW.

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High Temperature Desorbed Hydrogen in Ni/La2O3/α-Al2O3 Improves the Initial Reaction Rate of CH4/CO2 Reforming CUI Yuehua, XU Hengyong*, GE Qingjie, BI Yadong, WANG Yuzhong, HOU Shoufu, LI Wenzhao 2006, 27 (8):  659-663.  Abstract ( 2287 )   [Full Text(HTML)] () PDF (316KB) ( 912 )   The hydrogen desorbed at high temperature (high-temperature hydrogen) over the hydrogen reduced catalyst Ni/La2O3/α-Al2O3 was observed by H2 temperature-programmed desorption. Kinetic experiments show that the activity of the reforming reaction is initially increased with the amount of high-temperature hydrogen in Ni/La2O3/α-Al2O3 and finally reaches a constant value due to the in situ generation of the high-temperature hydrogen. Pulse results indicate that the high-temperature hydrogen in Ni/La2O3/α-Al2O3 is prone to form CHx species with high x values, which has higher activity for the reaction of CHx with CO2. The Ni/La2O3/α-Al2O3 catalyst with plenty of high-temperature hydrogen can increase the x values of CHx species and decrease the activation energy for the reaction between CHx and CO2, leading to a higher reaction rate. The addition of La2O3 on the Ni/α-Al2O3 catalyst promotes the reverse water-gas shift reaction and slightly improves the activation of CO2. La2O3 also increases the amount of high-temperature hydrogen and its stability, resulting in higher x values of CHx species and improving the reforming reaction rate.

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Study on Pyridine Adsorption in H-MOR by Quantum Chemistry YUAN Shuping1, 2*, DUAN Yunbo1, WANG Jianguo2, LI Yongwang2, JIAO Haijun2 2006, 27 (8):  664-670.  Abstract ( 1994 )   [Full Text(HTML)] () PDF (422KB) ( 958 )   The structure and Bronsted acidity of H-AlMOR and H-BMOR as well as their adsorption for pyridine probe molecule were investigated by using a 24T cluster containing a two-layered 12-membered ring and ONIOM2 (QM/QM and QM/MM) hybride methods. The Bronsted acidity of H-AlMOR is stronger than that of H-BMOR. Pyridine adsorption energy on H-AlMOR of 219.3 kJ/mol calculated by ONIOM2 (QM/QM) method compares well with the experimental result of 200 kJ/mol. In addition, the structure and IR stretching frequencies of the adsorption complexes shows that proton transfer occurrs during the pyridine adsorption, and the PyH+…ZeO- ion pairs are further stabilized by multiple hydrogen bonding between the hydrogen atoms of pyridine and the framework oxygen atoms of the zeolite.

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Hydrothermal Synthesis of V-MCM-41 Mesoporous Molecular Sieves and Synthesis Mechanism XU Junqiang1, CHU Wei1*, CHEN Muhua1, LUO Shizhong1, ZHANG Tao2 2006, 27 (8):  671-677.  Abstract ( 2301 )   [Full Text(HTML)] () PDF (485KB) ( 954 )   V-MCM-41 mesoporous materials were synthesized by the hydrothermal method using cetyltrimethylammonium bromide (CTAB) as the template and industrial Na2O•3.3SiO2 as the silica source, which is much cheaper than conventional organic precursors. The effects of synthesis conditions on the structure of V-MCM-41 were investigated and the synthesis mechanism was studied by N2 adsorption. The results indicated that many factors affected the synthesis, including the molar ratio of Si source and CTAB, pH value, crystallization temperature and time, aging time, calcination atmosphere, and feeding mode. The most important factors involved crystallization temperature, pH value, and molar ratio of Si to CTAB. X-ray diffraction results showed that the samples had a highly ordered hexagonal structure. Fourier transform infrared and ultraviolet visible spectra provided strong evidence that most vanadium ions were incorporated into the framework of mesoporous siliceous MCM-41.

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Effect of Na2SO4 on Structure and Catalytic Properties of Mn/SiO2 for the Oxidative Coupling of Methane HOU Sicong, XIONG Wei, LIU Lingtao, CAO Yuan, LIU Haichao*, KOU Yuan* 2006, 27 (8):  678-682.  Abstract ( 2406 )   [Full Text(HTML)] () PDF (324KB) ( 852 )   The oxidative coupling of methane to C2 hydrocarbons (C2H4 and C2H6) was examined on Mn-Na2SO4/SiO2. The catalysts were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, laser Raman spectroscopy, and temperature-programmed reduction with H2. The addition of Na2SO4 to Mn/SiO2 led to the exclusive transformation of amorphous SiO2 to α-cristobalite and the concurrent oxidation of Mn3O4 to Mn2O3. The observed effects on the structure and catalytic performance suggest that Mn2O3 species act as the active sites for the methane activation, which may provide the basis for the rational design of new efficient catalysts for the oxidative coupling of methane.

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Preparation of Chiral Oligomeric Cyclic salen-Mn(Ⅲ) Complex and Its Catalytic Performance for Asymmetric Epoxidation of Olefin HE Leqin, ZHAO Jiquan*, ZHANG Yaran, ZHAO Dongmin, ZHAO Shanshan 2006, 27 (8):  683-689.  Abstract ( 1897 )   [Full Text(HTML)] () PDF (439KB) ( 894 )   A novel chiral oligomeric cyclic salen ligand was synthesized by the reaction of a novel dialdehyde with (1R,2R)-1,2-diaminocyclohexane. From this ligand, the chiral oligomeric cyclic salen-Mn(Ⅲ) complex was prepared. The ligand and complex were characterized by nuclear magnetic resonance spectroscopy, Fourier-transform infrared spectroscopy, UV-Vis spectroscopy, gel permeation chromatography, and elemental analysis. The complex was used as a catalyst for the asymmetric epoxidation of olefin using NaClO and m-chloroperoxybenzoic acid as the oxidants, respectively. In the asymmetric epoxidation of cis-β-methylstyrene, the selectivity and enantiometric excess for the epoxides reached 96% and 78%, respectively. The recyclability of the catalyst was also studied.

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Preparation of Ni-B/MgO Catalyst by Ultrasonic Wave-Assisted Electroless Plating and Its Catalytic Hydrogenation Performance GE Shaohui1, WU Zhijie1, ZHANG Minghui1*, LI Wei1, MOU Shicheng2, TAO Keyi1 2006, 27 (8):  690-696.  Abstract ( 2224 )   [Full Text(HTML)] () PDF (587KB) ( 1004 )   A series of amorphous Ni-B alloy and supported Ni-B/MgO catalyst samples were prepared by silver-catalyzed electroless plating under different ultrasonic conditions. The effects of ultrasonic wave on the structure, composition, surface texture, and dispersion of Ni-B particles on MgO were characterized by inductively coupled plasma, X-ray diffraction, transmission electron microscope, selected area electron diffraction, and scanning electron microscopy. The activity of the as-prepared catalyst was tested by hydrogenation of sulfolene to sulfolane. In comparison with the catalyst prepared without ultrasonication, the presence of proper ultrasonic wave during the preparation led to the improvement of silver-catalyzed electroless plating, homogeneous dispersion of Ni-B particles, narrow range of Ni-B particle size, and superior catalytic hydrogenation performance. The amorphous structure of Ni-B particles was not influenced by the ultrasonic wave. The optimal output power of ultrasonic wave was 80 W and the temperature was 50 ℃.

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Preparation of N-Doped Visible-Light Response Nanosize TiO2 Photocatalyst Using the Acid-Catalyzed Hydrolysis Method LIU Shouxin*, CHEN Xiaoyun, CHEN Xi 2006, 27 (8):  697-702.  Abstract ( 2027 )   [Full Text(HTML)] () PDF (505KB) ( 866 )   The N-doped visible-light response nanosize TiO2 photocatalyst was prepared using the acid-catalyzed hydrolysis method followed by calcination in an NH3/N2 atmosphere. The photocatalytic activity of the prepared N-doped TiO2 for phenol degradation was investigated under visible and UV light irradiation, respectively. X-ray diffraction, UV-Vis diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, and N2 adsorption were used to characterize the catalyst. The results showed that the N-doped TiO2 catalyst displayed obvious photocatalytic activity under visible light irradiation. The N-doped TiO2[KG20x] catalyst calcined at 500 ℃ for 5 h exhibited the highest activity in both UV and visible light regions. N-doping showed little effect on the crystalline structure, surface area, and crystal size of TiO2. The Ti-O-N bond formed on the surface of the catalyst could extend the absorption edge to the visible light region (490-550 nm) and also benefit the photocatalytic acitivity of TiO2 under UV irradiation. The newly formed Ti-O-N bonds and the reduced agglomeration of the single crystals were mainly responsible for the high activity of the N-doped TiO2 in both UV and visible light regions.

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Preparation and Photocatalytic Properties of Titania Nanowire Arrays with Shape of String of Candied Haws TIAN Yuming, XU Mingxia*, LIU Xiangzhi, GE Lei, ZHANG Ping 2006, 27 (8):  703-707.  Abstract ( 1956 )   [Full Text(HTML)] () PDF (345KB) ( 1044 )   The titania nanowire arrays with good orientation and a shape of strings of candied haws were prepared using a highly ordered porous anodic alumina (PAA) template by the sol-electrophoresis method. X-ray diffraction and scanning electron microscopy were applied to characterize the titania nanowire arrays. The crystalline phase of the titania nanowires is anatase. The diameter of the nanowires is uniformly distributed and is consistent with the pore size of PAA. The periodic concave-convex structure was found in each nanowire. The photocatalytic activity of the titania nanowires was measured by degradation of a methyl orange solution. Compared with the TiO2 film on glass, the titania nanowire arrays have higher photocatalytic activity. Under the condition of 1 h irradiation, the degradation ratio of methyl orange increases to 93.6%, much higher than that of TiO2 film on glass (53.4%). Using this method, the self-immobilization of the titania photocatalyst can be easily achieved. In addition, the mechanism of the high photocatalytic activity is discussed.

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Synthesis and Characterization of Carbon Nanoribbons as Electrocatalyst Supports for Direct Methanol Fuel Cells QI Jing1,2, GAO Ying2, TANG Shuihua1, JIANG Luhua1, YAN Shiyou1, GUO Junsong1, XIN Qin1,3, SUN Gongquan1* 2006, 27 (8):  708-712.  Abstract ( 2048 )   [Full Text(HTML)] () PDF (392KB) ( 897 )   Carbon nanoribbons (CNRs) were synthesized using the resorcinol-formaldehyde gel as a precursor and were characterized by X-ray diffraction, transmission electron microscopy, and nitrogen adsorption-desorption. CNRs are highly graphitized and the width of the ribbon is 8-20 nm. The BET surface area of CNRs is 283 m2/g, and the nitrogen isotherm for the CNRs with an average pore size of 8.2 nm is classified as type-Ⅳ. A platinum-based binary electrocatalyst, PtRu/CNRs, using CNRs as the support and having a metal loading of 45% was prepared using a modified polyol process. The performance of the single cell using PtRu/CNRs as the anode electrocatalyst is significantly improved when compared with that using Vulcan XC-72R as the support, indicating that CNRs are promising electrocatalyst supports for direct methanol fuel cells.

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Effect of Reaction Conditions on Catalytic Performance of Cu/Al-Ce-PILC for Selective Catalytic Reduction of NO by Propylene LIN Qichun1, LIN Weiming2, HAO Jiming1, LI Junhua1 2006, 27 (8):  713-718.  Abstract ( 1881 )   [Full Text(HTML)] () PDF (377KB) ( 709 )   Montmorillonite was pillared by multi-oligomeric hydroxyl cations to synthesize Al-Ce-PILC (PILC[CD1]pillared interlayer clay), which was modified by SO2-4 and then was used as a catalyst support to prepare the Cu/Al-Ce-PILC catalyst by impregnation. The influence of pretreatment atmosphere, concentration of O2 and C3H6, space velocity, water vapor, and SO2 on the conversion of NO and C3H6 over Cu/Al-Ce-PILC was investigated. The results showed that both Cu+and Cu2+ species were observed on Cu/Al-Ce-PILC pretreated in He, while only Cu+ existed after being pretreated in H2, and the maximum NO conversion was enhanced from 23% to 56%. Proper concentration of O2 and C3H6 promoted the reduction of NO to N2, and the formation of coke was distinctly suppressed by excess oxygen. NO conversion decreased with increasing space velocity. The presence of 10% water vapor in the feed restrained the selective catalytic reduction (SCR) of NO, the temperature for the maximum conversion increased, and the maximum conversion of NO and C3H6 decreased by 13% and 5%, respectively. Compared with Cu-ZSM-5, Cu/Al-Ce-PILC showed better resistance to water vapor owing to the hydrophobic nature of the oxide pillar surface. SO2 greatly inhibited the SCR activity of Cu/Al-Ce-PILC at low temperature and slightly promoted it at high temperature.

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Effect of Calcination Temperature of TiO2-Al2O3 Composite Oxide Support on Catalytic Performance of Au-Pd Catalyst for Hydrodesulfurization of Thiophene GU Zhonghua, LUO Laitao*, XIA Mengjun, LI Maokang 2006, 27 (8):  719-724.  Abstract ( 1929 )   [Full Text(HTML)] () PDF (416KB) ( 871 )   TiO2-Al2O3 composite oxides were prepared by the sol-gel method and calcined at 773-1?073 K. The influence of calcination temperature of the composite oxide on the catalytic performance of Au-Pd/TiO2-Al2O3 catalyst for the hydrodesulfurization of thiophene was studied. The prepared samples were characterized by X-ray diffraction, temperature-programmed desorption of adsorbed pyridine, temperature-programmed reduction, infrared spectroscopy, and nitrogen adsorption. The results showed that all the TiO2-Al2O3 samples were mesoporous materials, and the TiO2-Al2O3 calcined at 773 K had larger BET surface area and pore volume, and more Bronsted acid centers. Au-Pd/TiO2-Al2O3 catalysts showed good activity for the hydrodesulfurization of thiophene. The Au-Pd supported on the TiO2-Al2O3 calcined at 773 K showed the highest activity because of the stronger metal-support interaction, the more AuxPdy active centers formed on the catalyst surface and Bronsted acid sites, the higher metal dispersion, and the lower apparent activation energy.

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Catalytic Performance of Supported KNO3 Solid Bases for Methylation of Cyclopentadiene SUN Linbing1, WU Zhengying1, KOU Jiahui2, CHUN Yuan1*, WANG Ying1, ZHU Jianhua1, ZOU Zhigang2 2006, 27 (8):  725-731.  Abstract ( 1843 )   [Full Text(HTML)] () PDF (425KB) ( 986 )   The catalytic performance of a series of supported KNO3 solid bases for the synthesis of methylcyclopentadiene via cyclopentadiene methylation with methanol was investigated. X-ray diffraction and N2 adsorption were applied to study the characteristics of different supports and the decomposition of KNO3 on them. The base strength of samples was measured using Hammett indicator. Significant difference in base strength of different oxides-supported KNO3 was observed. A base strength (H-) of 27.0 was detected in KNO3 supported on ZrO2, γ-Al2O3, hydrotalcite (HT), and MgO, which showed the characteristics of solid superbases; while a base strength (H-) of only 9.3 was examined in SiO2- and TiO2- supported KNO3. Such difference in base strength could be ascribed to the differences in surface nature of supports. A suitable basicity was necessary for catalyzing the methylation of cyclopentadiene with methanol, since only small amounts of cyclopentadiene molecules were converted over catalysts with low basicity, such as KNO3/SiO2 and KNO3/TiO2 as well as most oxide supports. However, the acidity and surface area of catalysts also had certain effects on the reaction. The conversion of cyclopentadiene and selectivity for methylcyclopentadiene were around 32% and 86%, respectively, over KNO3/γ-Al2O3 and KNO3/HT at 450 ℃. Such catalytic activity was higher than that on MgO.

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Synthesis and Photocatalytic Activity of Macroporous TiO2 Photocatalyst with Three-Dimensional Structure XU Zhibing1*, GUO Chang1, LONG Xingxing1, TANG Yecang2, WEI Xianwen2 2006, 27 (8):  732-736.  Abstract ( 1809 )   [Full Text(HTML)] () PDF (383KB) ( 840 )   The macroporous TiO2 photocatalyst was synthesized using spherical polymethyl methacrylate particles as the template and Ti(OBu)4 as the raw material by the sol-gel method. The samples were characterized by differential scanning calorimetry, thermogravimetry-differential thermogravimetry, scanning electron microscopy, infrared spectroscopy, X-ray diffraction, and N2 adsorption. The characteristic pore structure with about 200 nm spherical voids was obtained after calcination. The contents of anatase and rutile in the TiO2 nanocrystals of the macroporous TiO2 photocatalyst were 82% and 18%, respectively. The experiment of photocatalytic degradation of methyl orange showed that the macroporous TiO2 photocatalyst has a high photocatalytic activity.

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Preparation of Amphiphilic Zeolites with Various Pore Structure and Their Catalytic Performance for Phase-Boundary Reaction MA Bingli, CHUN Yuan*, XU Qinhua, DONG Jialu 2006, 27 (8):  737-742.  Abstract ( 1676 )   [Full Text(HTML)] () PDF (339KB) ( 774 )   Amphiphilic TMS-Hβ, TMS-HY, and TMS-HZSM-5 zeolite samples were prepared by modification of the surface of their parent zeolites with trimethylchlorosilane (TMS). X-ray diffraction, infrared spectroscopy, water adsorption, and titration experiments were used to characterize the surface properties of these modified samples. The modification results by TMS were different on these three zeolites. TMS molecules only covered the external surface of the HZSM-5 zeolite, while part of TMS entered the channels of the Hβ and HY zeolites and even partly destroyed the framework of HY. The amphiphilic TMS-HZSM-5 and TMS-Hβ zeolites exhibited catalytic activity for hydrolysis of isoamyl acetate obviously superior to their parent zeolites. The stability of the alkylsilane on the zeolite surface had an effect on the phase-boundary catalytic performance of the amphiphilic zeolites. TMS molecules covered on TMS-Hβ were more stable than that covered on TMS-HZSM-5. Thus, the TMS-Hβ zeolite maintained its amphiphilic properties at a higher reaction temperature and exhibited a higher phase-boundary catalytic activity than the TMS-HZSM-5 zeolite.

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Asymmetric Oxidation of Sulfides Catalyzed by Vanadium(Ⅳ) Complexes of Dibromo- and Diiodo-Functionalized Chiral Schiff Bases GAO Aiping1, WANG Mei1*, WANG Dongping1, ZHANG Lu1, LIU Haibin1, TIAN Wei1,2, SUN Licheng1,3* 2006, 27 (8):  743-748.  Abstract ( 2066 )   [Full Text(HTML)] () PDF (285KB) ( 1039 )   The catalyst system of VO(acac)2 and Schiff base ligands derived from 3,5-dibromo- or 3,5-diiodosalicylaldehyde and inexpensive chiral amino alcohols was prepared. This catalyst displayed good yields and moderate to high enantioselectivity for the asymmetric oxidation of aryl methyl sulfides at room temperature when 1% catalyst (VO(acac)2/ligand molar ratio of 1∶2) and H2O2 oxidant were used. The ligands derived from (S)-valinol exhibited considerably higher enantioselectivity than those ligands derived from (S)-phenylalaninol and (R)-leucinol. The enantiomeric excess values were improved up to 88% for methyl phenyl sulfoxide and 92% for methyl p-bromophenyl sulfoxide by slow dropwise addition of H2O2 with the ligand prepared from 3,5-diiodosalicylaldehyde and (S)-valinol. The present study showed that the catalytic efficiency of VO(acac)2/Schiff base systems could not be improved by the addition of carboxylic acids or carboxylate salts.