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Chinese Journal of Catalysis
2008, Vol. 29, No. 8
Online: 25 August 2008

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A Three-Way Catalyst Meeting Euro Ⅲ Emission Standards for Motorcycles HU Chunming;ZHAO Ming;WANG Hairong;CHEN Shanhu;GONG Maochu;SHI Zhonghua;CHEN Yaoqiang* 2008, 29 (8):  677-679.  Abstract ( 2121 )   [Full Text(HTML)] () PDF (215KB) ( 1017 )

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Preparation of Titania Nanotube Arrays by Hydrothermal Reaction in Combination with Anodic Aluminum Oxide Template Attached to Aluminum Substrate LI Gang;LIU Zhongqing*;YAN Xin;ZHANG Zhao* 2008, 29 (8):  680-682.  Abstract ( 2319 )   [Full Text(HTML)] () PDF (347KB) ( 987 )   TiO2 nanotube arrays were prepared in situ on aluminum substrate via hydrothermal reaction, using ammonium hexafluorotitanate as treatment solution and anodic aluminum oxide attached to aluminum substrate as template. Field emission scanning electron microscopy andX-raydiffraction were carried out to characterize the as-synthesized product. The experimental results show that TiO2 nanotube arrays obtained through hydrothermal synthesis exhibit an especial morphology. The surface of the TiO2 nanotube arrays has continuous porous structure, while the cross-section has discrete and unattached tubular structure constituted of densely packed titania nanoparticles with an average particle size of 45 and 25 nm, respectively. Without any further heat treatment, anatase phase crystalline structure of the as-prepared nanotube arrays using this method has already occurred.

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Density Functional Theory Study of CO Catalytic Oxidation on Pt(111) and Pt3Ni(111) Surfaces SU Haiyan;LI Weixue*;BAO Xinhe* 2008, 29 (8):  683-686.  Abstract ( 2470 )   [Full Text(HTML)] () PDF (241KB) ( 898 )   CO and O adsorption and co-adsorption and CO oxidation on Pt(111) and Pt3Ni(111) surfaces were studied systematically by density functional theory calculations. Compared with CO and O adsorption on the Pt(111) surface, adsorption on the Pt3Ni(111) surface is slightly destabilized for CO but stabilized significantly for O. Both surfaces have similar reactivity for CO oxidation. The presence of surface Ni atoms stabilizes oxygen not only at the initial state but also at the transition state on the Pt3Ni(111) surface.

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Physicochemical, surface, and catalytic properties of pure and ceria-doped manganese/alumina catalysts Nasr Allah M. DERAZ 2008, 29 (8):  687-695.  Abstract ( 2178 )   [Full Text(HTML)] () PDF (542KB) ( 808 )   Pure and CeO2-doped Mn/Al mixed oxides were prepared by the wet impregnation method using finely powdered alumina, manganese, and cerium nitrates. The physicochemical, surface, and catalytic properties of the thermally treated solids (at 500, 800, and 900 ℃) were investigated using XRD, nitrogen adsorption at -196 ℃, and hydrogen peroxide decomposition in an aqueous solution at 30~50 ℃. The Mn oxidation state changed from Mn4+ to Mn2+ on increasing the calcination temperature. There were two unique features associated with CeO2 that are of interest. The first was that it favored the dispersion of manganese oxides deposited on the γ-Al2O3 catalyst calcined at 500 ℃. The second was that it enhanced the formation of Mn3O4 species from Mn2O3 deposited initially on the alumina support calcined at 800 and 900 ℃. Consequently, the specific surface area of the Mn/Al mixed oxides calcined at 500 ℃ was increased by increasing the amount of dopant added. An opposite effect was observed by increasing the calcination temperature from 500 to 900 ℃. The doping followed by calcination at different temperatures brought about an increase in the catalytic activity of mixed oxides. Pretreatments did not modify the mechanism of the catalyzed reaction but changed the number of catalytically active sites without changing the nature of these sites.

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Enantioconvergent Hydrolysis of p-Nitrostyrene Oxide Catalyzed by Mung Bean Epoxide Hydrolase JU Xin;PAN Jiang;XU Jianhe* 2008, 29 (8):  696-700.  Abstract ( 2402 )   [Full Text(HTML)] () PDF (239KB) ( 1012 )   Mung bean epoxide hydrolase was used for enzymatic preparation of (R)-p-nitrophenyl glycol by enantioconvergent hydrolysis of p-nitrostyrene oxide. Enzyme forms and reaction conditions were examined, and an efficient process and high product yield were obtained for this biocatalyst. Tween-80 was found to be an ideal dispersant. Various immobilized biocatalysts were prepared by different methods, and the biocatalyst adsorbed on diatomite powder showed better stability. Gram-scale preparation was performed, giving a yield of 73.3% and an optical purity higher than 99% ee.

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Dehydration of 2-(4′-Ethylbenzoyl)benzoic Acid to 2-Ethylanthra-quinone over H-β Zeolite Impregnated with Citric Acid ZHAI Lingjuan;LIU Min;DONG Xiangmei;SONG Chunshan;GUO Xinwen* 2008, 29 (8):  701-704.  Abstract ( 2197 )   [Full Text(HTML)] () PDF (278KB) ( 1043 )   H-β zeolite catalyst samples were prepared by impregnation with citric acid and were characterized byX-raydiffraction,X-rayfluorescence, Fourier transform infrared spectroscopy, nuclear magnetic resonance, and temperature-programmed desorption. The catalytic performance of the catalyst samples for dehydration of 2-(4′-ethylbenzoyl)benzoic acid (EBA) to 2-ethylanthraquinone (EAQ) was measured. The results showed that the impregnated samples remained the topological structure of H-β zeolite. There was more residual extra-framework aluminum and citric acid on the unwashed sample after impregnation. The sample washed with deionized water after impregnation exhibited high activity and selectivity in the reaction of EBA dehydration. The conversion of EBA was 96.5%, and the selectivity for EAQ was 96.0%

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Hydrodesulfurization Activity of Nano-sized HZSM-5 Catalyst Modified by NiO or NiSO4 WANG Wenshou;GUO Hongchen;LIU Hai'ou;WANG Xiangsheng* 2008, 29 (8):  705-709.  Abstract ( 2257 )   [Full Text(HTML)] () PDF (354KB) ( 877 )   The hydrodesulfurization (HDS) activity of nano-sized HZSM-5 catalyst modified by different nickel species was measured with full-range FCC gasoline as feedstock. The results indicated that the nano-sized HZSM-5 catalyst modified by NiSO4 showed more stable HDS activity than the nano-sized HZSM-5 catalyst modified by NiO. The characterization of FT-IR spectra before and after pyridine adsorption, ammonium temperature-programmed desorption, and differential thermogravimetry showed that there was a strong interaction between SO2-4 and Al2O3 in the catalyst modified by NiSO4. The interaction increased both the amount and the strength of acid sites by creating a kind of acidity, being like super acid.

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Hydrazine Decomposition and CO Adsorption Microcalorimetry on Tungsten Carbide Catalysts with Different Phases SUN Jun;WANG Xingtang;WANG Xiaodong;ZHENG Mingyuan;WANG Aiqin;ZHANG Tao* 2008, 29 (8):  710-714.  Abstract ( 2385 )   [Full Text(HTML)] () PDF (339KB) ( 1090 )   Tungsten carbides with different crystal phases were prepared by temperature-programmed reaction of WO3 in a CH4/H2 atmosphere, and the phase transition occurring during this process was described. The catalytic activity of the tungsten carbides for hydrazine decomposition was investigated, and the active sites were determined by CO adsorption microcalorimetry. The results showed that the CO adsorption became strong with the formation of a W2C crystal phase, and the W2C exhibited the best catalytic performance for N2H4 decomposition. However, when the preparation temperature was higher than 750 ℃, there was a significant amount of carbonaceous species deposited on the catalyst surface, which resulted in severe deactivation. The surface-clean WC possessed a higher intrinsic activity for N2H4 than the W2C owing to its stronger noble metallic properties.

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Investigation on Ethylene Dimerization over H-ZSM-5 Zeolite by Theoretical Calculation ZHANG Jia;ZHOU Danhong*;NI Dan 2008, 29 (8):  715-719.  Abstract ( 2406 )   [Full Text(HTML)] () PDF (337KB) ( 894 )   By the QM/MM hydride ONIOM2(B3LYP/6-31G(d,p): UFF) method, the reaction mechanism of ethylene dimerization over H-ZSM-5 zeolite was investigated. A 40T cluster model was used to simulate the acidic sites located at the intersection of channels in ZSM-5 zeolite. Both stepwise and concerted reaction pathways were examined. For the stepwise mechanism, the ethylene molecule was firstly adsorbed at the Brnsted acid site via π-hydrogen bonding to form a stable complex, which then went through the protonation, leading to the formation of the ethoxide intermediate. Furthermore, the ethoxide reacted with the second ethylene molecule to form the butoxide product. The calculated activation energies for the first and second steps were 152.88 and 119.45 kJ/mol, respectively. The ethylene protonation step was confirmed as the rate-limiting step. For the concerted mechanism, the protonation,C-CandC-Obonds formation proceeded simultaneously to produce butoxide. The calculated activation energy of 162.30 kJ/mol was slightly higher than that of the rate-limiting step in the stepwise mechanism. It was proposed that there should be a competition between the two reaction mechanisms.

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Selective Oxidation of Methane to Methanol in Oleum over Pd/C Catalyst WEI Xin;YE Linmin;ZHU Mingxia;YUAN Youzhu* 2008, 29 (8):  720-726.  Abstract ( 2482 )   [Full Text(HTML)] () PDF (503KB) ( 1097 )   The selective oxidation of methane to methanol over Pd/C catalysts generated from a PdCl2 precursor was investigated in oleum. Characterization of the catalysts was performed byX-raydiffraction,X-rayphotoelectron spectroscopy, high-resolution transmission electron microscopy, and CO adsorption. The major product in the oxidation reaction was methyl bisulfate, which was then hydrolyzed into methanol. Methane conversion of 23.6% with methanol selectivity of 69.5% and yield of 16.4% was achieved under the optimum conditions of 5%Pd/C, 30 μmol Pd, reaction temperature 180 ℃, methane pressure 4.0 MPa, reaction time4 h, and 50% sulfur trioxide concentration. After facile separation with the reactants and pretreatment, the catalyst could be reused several times with considerable stability. The selective oxidation of methane catalyzed by Pd/C catalysts in oleum possibly involved an electrophilic substitute mechanism. The catalytic performance was related to the Pd loading, dispersion, and particle size.

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Synthesis of SAPO-34 with Rich Si(4Al) Coordination Environment in the Framework and Its Catalytic Performance in Methanol-to-Olefins Reaction XU Lei;DU Aiping;WEI Yingxu;MENG Shuanghe;HE Yanli;WANG Yingli;YU Zhengxi;ZHANG Xinzhi;LIU Zhongmin* 2008, 29 (8):  727-732.  Abstract ( 2393 )   [Full Text(HTML)] () PDF (374KB) ( 1100 )   SAPO-34 molecular sieve samples with rich Si(4Al) coordination environment were synthesized by adding HF in the initial gel. The crystalline phase, crystal morphology, elemental composition, and Si coordination environment of the as-synthesized samples were determined by means ofX-raydiffraction, scanning electron microscopy,X-rayfluorescence spectroscopy, and nuclear magnetic resonance. The crystallization of SAPO-34 molecular sieve can be adjusted by adding HF in the initial gel, and correspondingly, the Si coordination modeling can be controlled. The proportion of Si(4Al) species in the as-synthesized SAPO-34 increased, and that of Si(nAl)(n=3-0) decreased with increasing fluorine ion content in the initial gel. The catalytic performance of the SAPO-34 catalysts with various Si coordination was investigated in the methanol-to-olefins reaction. The results showed that SAPO-34 catalysts with rich Si(4Al) coordination structure had higher selectivity to ethylene and longer life time.

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Double-Templating Synthesis of Hierarchical Meso-macroporous Silica Monolith LIU Qian;LI Hongxu;QIAN Bin;GAO Huanxin;WANG Yangdong;TANG Yi;XIE Zaiku* 2008, 29 (8):  733-740.  Abstract ( 2348 )   [Full Text(HTML)] () PDF (929KB) ( 1452 )   Hierarchical meso-macroporous materials have attracted much attention due to their potential applications in catalysis, sorption, and separation. The incorporation of interconnected macropores in mesoporous materials is very useful because macropores can favor mass transfer and reduce transport limitations. However, it still remains a challenge to fabricate ordered mesoporous channels in the bicontinuous macroporous framework walls. This paper reports a double-templating route based on a sol-gel method to prepare hierarchical meso-macroporous silica monoliths. The obtained material shows a bicontinuous macroporous structure with highly ordered meso-channels distributing inside the macroporous skeleton walls. The bimodal pore structure was formed under the action of the two templates. The organic polymer was added to induce a phase separation taking place at the sol-gel transition and thus form the bicontinuous macroporous structure. Meanwhile, a nonionic surfactant was introduced to template the formation of ordered mesostructure inside the macroporous skeleton walls. As characterization by scanning electron microscopy, transmittance electron microscopy, N2 physisorption, andX-raydiffraction, the resulting silica monolith exhibits specific surface area as high as 880 m2/g and pore volume as large as 1.2 cm3/g. The hexagonally ordered mesopores are highly centered at 5.8 nm. Besides, through optimizing the synthesis procedure, the monolith morphology of the resulting materials can be perfectly preserved during the wet gel drying process, and thus a crack-free hierarchical silica monolith with centimeter scale can be obtained.

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Synthesis of α-Tetralone from Tetralin by Metalloporphyrin and Transition Metal Salt Tandem Catalysis and the Reaction Mechanism YANG Weijun*;CAO Jun;YIN Bijun;GUO Cancheng 2008, 29 (8):  741-747.  Abstract ( 2194 )   [Full Text(HTML)] () PDF (368KB) ( 1247 )   An efficient two-step preparation of α-tetralone from tetralin was studied. First, tetralin was oxidized to α-tetralin hydroperoxide with air in the presence of a metalloporphyrin catalyst. Second, a catalytic amount of either water-soluble iron salts or copper salts was added to the resultant α-tetralin hydroperoxide solution to convert α-tetralin hydroperoxide into α-tetralone. The major product of oxidation catalyzed by metalloporphyrin was α-tetralin hydroperoxide, and only a minor amount of α-tetralone and trace of α-tetralol were formed. Simple salts such as CuⅠand FeⅡcould efficiently decompose α-tetralin hydroperoxide to α-tetralone, and best result was obtained with ferrous ion. The influence of the metal ions, catalyst amount, and reaction temperature on both the tetralin aerobic oxidation and the decomposition of α-tetralin hydroperoxide was studied. Possible mechanisms for the oxidation of tetralin and the decomposition of α-tetralin hydroperoxide were proposed.

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Density Functional Theory Study of Benzene Adsorption on CuCl(111) Surface CHEN Wenkai*;WANG Xia;CHEN Zhanhong;LU Chunhai;ZHENG Jinde 2008, 29 (8):  748-752.  Abstract ( 1790 )   [Full Text(HTML)] () PDF (291KB) ( 875 )   The adsorption of benzene on CuCl(111) surface has been studied by density functional theory calculation with the GGA Perdew-Wang method. The calculated results indicate that benzene adsorption on surface Cl site is the most favorable. The smaller the coverage is, the more stable the adsorption is. The predicted adsorption energy for benzene adsorption on Cl site is 74 kJ/mol, in fair agreement with the experimental results. The benzene adsorption on top and hollow sites is physical adsorption. The density of states and the charge population before and after the adsorption have also been analyzed. The calculated results show the back donation of Cu 3d electrons to the π* anti-bonding orbital of benzene, which weakens the aromatic bond.

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Activity and Stability of LaFeO3 Catalyst in Lignin Catalytic Wet Oxidation to Aromatic Aldehydes DENG Haibo;LIN Lu*;SUN Yong;PANG Chunsheng;ZHUANG Junping;OUYANG Pingkai;LI Jingjiang 2008, 29 (8):  753-757.  Abstract ( 2303 )   [Full Text(HTML)] () PDF (427KB) ( 1216 )   The perovskit-type oxide LaFeO3 catalyst was prepared by the sol-gel method. The structure, shape, particle size, surface species, and specific surface aera of the catalyst were characterized byX-raydiffraction, scanning electron microscopy,X-rayphotoelectron spectroscopy, and N2 adsorption. The catalyst was used for wet oxidation of lignin to aromatic aldehydes and showed high activity and stability. Compared with a non-catalytic process, lignin conversion and yield of each aromatic aldehyde increased significantly, among which the yield of syringaldehyde was the highest. The maximum yield of syringaldehyde was 1.85 times that of the non-catalytic process. The activity and perovskite-type structure of the LaFeO3 catalyst almost remained unchanged after five successive operations.

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Effect of Vanadium Modification on Structure and Catalytic Properties of SO2-4/ZrO2-Al2O3 Solid Acid Catalyst WANG Yuhong*;WANG Yuemin;LI Jun 2008, 29 (8):  758-764.  Abstract ( 2398 )   [Full Text(HTML)] () PDF (539KB) ( 1213 )   The V-promoted SO2-4/ZrO2-Al2O3 solid superacid catalyst was prepared by the coprecipitation and impregnation method under different conditions. The catalytic properties of the samples were evaluated through esterification of acetic acid and n-butanol and characterized by thermogravimetry (TG),X-raydiffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), BET surface area measurement, andX-rayphotoelectron spectroscopy (XPS). The results show that among all the prepared samples the one that was calcined at 600 ℃, aged at 0 ℃, and impregnated with a solution containing 0.005 mol/L NH4VO3 after impregnation with sulfuric acid has the highest esterification rate of 99.71%. For this sample there was no significant change in the catalytic activity after being recycled 5 times (averaged 98.59%). An analysis of XRD patterns reveals that the incorporation of vanadium into tetragonal zirconia stabilizes the compound, the aging facilitates the formation of tetragonal zirconia microcrystals, and the calcination increases the reactivity of the catalyst by producing a greater fraction of active tetragonal zirconia with a larger surface area. It can be seen from the FT-IR spectra that superacid structures are formed in the catalysts and the absorption peak for theS=Obond is strengthened remarkably. The XPS results indicate that there are strong interactions between the V(Ⅴ) ions and their surroundings. The TG plots show that the samples aged at 0 ℃ exhibited less stability in despite of better catalytic activity.

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Effect of the Sn(Ⅱ)/Sn(Ⅳ) Redox Couple on the Activity of PtSn/C for Ethanol Electro-oxidation ZHU Mingyuan;SUN Gongquan*;LI Huanqiao;CAO Lei;XIN Qin 2008, 29 (8):  765-770.  Abstract ( 2080 )   [Full Text(HTML)] () PDF (473KB) ( 909 )   The PtSn/C-Ni catalyst was prepared by adding Ni(NO3)2 in the reduction process of SnCl2 and H2PtCl6 with ethylene glycol. The coexistence of the Sn(Ⅱ)/Sn(Ⅳ) redox couple was detected in the catalyst by temperature-programmed reduction experiments. Linear sweep voltammetry, single cell test, and CO stripping voltammetry experiments showed that the ethanol electro-oxidation activity and CO tolerance can be obviously enhanced by increasing the Sn(Ⅱ)/Sn(Ⅳ) ratio in the catalyst. The reason might be attributed to that the Sn(Ⅱ)/Sn(Ⅳ) redox couple accelerates the transfer rate of (OH)adsand then promotes the consequent oxidation of CO-like intermediates that are produced in the ethanol electro-oxidation process on the surface of Pt.

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Synergistic Effect of an Ionic Liquid Catalyst with Two Kinds of Basic Sites on Knoevenagel Condensation LIU Wei;LIU Ye* 2008, 29 (8):  771-776.  Abstract ( 2234 )   [Full Text(HTML)] () PDF (301KB) ( 1039 )   1-(2-piperidyl-ethyl)-3-methylimidazolium 2-morpholinyl-4-ethane sulfonate ([Pemim]Mes) with two basic groups individually located in cation and anion exhibited synergistically catalytic behavior for Knoevenagel condensation. Under non-acidic conditions, [Pemim]Mes proved to be an active, stable, and universal catalyst for Knoevenagel condensation between aromatic aldehydes and active methylene compounds. The catalytic mechanism of Knoevenagel condensation synergistically catalyzed by the basic ion pair existing in [Pemim]Mes was tentatively proposed.

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Influence of Chemical States of Au on CO Oxidation over Au/CoCeOx Catalyst TA Na;ZHANG Milin;LI Juan;LI Huaju;SHEN Wenjie* 2008, 29 (8):  777-782.  Abstract ( 2042 )   [Full Text(HTML)] () PDF (496KB) ( 1031 )   Au/CoCeOx catalysts were prepared by a deposition-precipitation method. Au chemical states were controlled by varying the temperature of pretreatment in an oxygen-containing atmosphere. The catalysts were characterized by powderX-raydiffraction, high-resolution transmission electron microscopy, temperature-programmed reduction, andX-rayphotoelectron spectroscopy. The catalytic performance for CO oxidation was investigated at ambient temperature. It was found that the conversion of CO increased with increasing amount of Au+ in the catalyst, and thus the cationic gold (Au+) was considered the main active species. Addition of water vapor to the feed gas promoted CO conversion to some degree, but the catalytic performance decreased rapidly due to the disproportionation of Au+ to Au3+and Au0, particularly for the catalyst that contained relatively large amounts of Au+ species.

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Synthesis of Nanosized Ag3VO4 Particles and Their Photocatalytic Activity for Degradation of Rhodamine-B under Visible Light ZHANG Yonglai;DING Hong;LIU Fujian;WEI Shu;LIU Sen;HE Dongliang;XIAO Fengshou* 2008, 29 (8):  783-787.  Abstract ( 2517 )   [Full Text(HTML)] () PDF (549KB) ( 1185 )   By a simple coprecipitation process, a series of Ag3VO4 samples with crystalline particles from 100 nm to 5 μm were successfully synthesized at temperatures of0-80 ℃. The addition of polyethyleneglycol in the synthetic system resulted in the formation of nanosized particles with50-100 nm. The photocatalytic degradation of rhodamine B under visible light irradiation showed that the Ag3VO4 samples, particularly the nanosized Ag3VO4 sample, were much more active than the commercial photocatalyst titania P25. In addition, after 4 recycles, there was no significant decrease in the photocatalytic activity of Ag3VO4 samples, indicating that the Ag3VO4 was a stable photocatalyst for degradation of rhodamine B under visible light irradiation.