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Chinese Journal of Catalysis
2007, Vol. 28, No. 12
Online: 25 December 2007

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Amorphous Manganese Oxide for Catalytic Aerobic Oxidation of Benzyl Alcohol HU Jing;SUN Keqiang;HE Daiping;XU Boqing* 2007, 28 (12):  1025-1027.  Abstract ( 2046 )   [Full Text(HTML)] () PDF (156KB) ( 1617 )   The effect of calcination temperature on the textual structure and catalytic properties of amorphous MnOx for the liquid-phase aerobic oxidation of benzyl alcohol was studied. The amorphous nature of the synthesized MnOx was retained when the calcination temperature was lower than 400 ℃, and calcination temperatures higher than 500 ℃ led to the transformation of amorphous MnOx to crystalline OMS-2 and Mn2O3. Catalytic reaction studies revealed that the amorphous MnOx exhibited higher mass specific activity than OMS-2, Mn2O3, and γ-MnO2, and MnOx calcined at 110 ℃ showed the highest activity. An inverse linear correlation between the onset reduction temperature in H2-TPR and the mass specific activity of the various manganese oxides was observed. This suggested that the reducibility of manganese oxide is the key factor responsible for its activity for the aerobic oxidation of benzyl alcohol.

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Mo-Co-K Sulfide-Based Catalysts Promoted by Rare Earth Salts for Selective Synthesis of Ethanol and Mixed Alcohols from Syngas YANG Yong*;WANG Yangdong;LIU Su;SONG Qingying;XIE Zaiku;GAO Zi 2007, 28 (12):  1028-1030.  Abstract ( 2136 )   [Full Text(HTML)] () PDF (258KB) ( 1013 )   Mo-Co-K sulfide-based catalysts promoted by rare earth metal salts (La, Ce, and Y) were prepared by an ultrasonic technology in a non-aqueous medium. The catalytic performance for the selective synthesis of ethanol and mixed alcohols from syngas was evaluated and compared with that of the unpromoted catalyst Mo-Co-K. Under the reaction conditions of 3.0 MPa, 330 ℃, H2/CO(V/V)=2.0, and GHSV=2225h-1, the CO conversion and ethanol distribution over the La-promoted catalyst were 17.2% and 53.4%, respectively. The results of SEM, TEM, XRD, Raman, and XPS characterization indicated that the morphology and electronic structure of the catalysts changed, and the CO conversion and ethanol distribution increased after the addition of rare earth promoters.

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Preparation of Phenylalanine from Phenylpyruvic Acid by Hydrogenation over Ni-B Amorphous Alloy LI Lin*;LIANG Qunfang;ZHANG Aiqing 2007, 28 (12):  1031-1033.  Abstract ( 2043 )   [Full Text(HTML)] () PDF (268KB) ( 946 )   The preparation of phenylalanine from phenylpyruvic acid by amination and hydrogenation was investigated over amorphous Ni-B alloy catalysts prepared by chemical reduction. The amorphous Ni-B alloy showed better activity and selectivity than the commercial Raney Ni and Urushibara Ni catalysts. After the Ni-B alloy was supported on SiO2, the activity and selectivity of Ni-B/SiO2 were further improved to 97.67%. The higher activity and selectivity of the amorphous alloy catalysts were mainly ascribed to the electron-rich Ni due to electron donation from B and the larger specific surface area of the amorphous alloys.

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Facile Synthesis of Ag-Hollandite Nanofibers and Their Catalytic Activity for Ethanol Selective Oxidation CHEN Junli;LI Juan;LIU Qiying;HUANG Xiumin;SHEN Wenjie* 2007, 28 (12):  1034-1036.  Abstract ( 1904 )   [Full Text(HTML)] () PDF (265KB) ( 829 )   Ag-hollandite nanofibers were synthesized by refluxing a mixture of AgMnO4 and Mn(NO3)2 in nitrate acid solution at 373 K and used for ethanol selective oxidation. TheX-raydiffraction pattern showed that the main crystalline phase was Ag-hollandite, but a small amount of pyrolusite was also formed. The N2 adsorption-desorption isotherms confirmed the presence of a microporous structure. Field emission scanning electron microscopy and transmission electron microscopy showed that the lengths of the nanofibers were0.5-4.0μm, and the diameters were 10-20 nm. The Ag-hollandite nanofibers gave a promising catalytic performance for ethanol selective oxidation to acetaldehyde, with an ethanol conversion of 82% and acetaldehyde selectivity of 95% at 503 K for 120 h time-on-stream.

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Synthesis and Characterization of Ni-Doped Vanadium Phosphorus Oxide Catalysts TAUFIQ-YAP Yun Hin*;ABDUL GHANI Abdul Aziz 2007, 28 (12):  1037-1040.  Abstract ( 2012 )   [Full Text(HTML)] () PDF (281KB) ( 925 )   The effect of Ni doping (1%, 2%, and 5%) on vanadium phosphate catalysts prepared via VOPO4•2H2O was described and discussed. At low levels, the Ni dopant significantly enhanced the amount of the active lattice oxygen species O- and lowered the reduction peak temperature corresponding to the reduction of V5+and V4+phases. A combination of powderX-raydiffraction, temperature-programmed reduction, and chemical analysis data shows that at higher levels, Ni doping induced the formation of the V5+phase and suppressed the presence of the V4+phase. Previous studies have indicated that a large amount of oxygen species associated with V5+ inhibit the n-butane conversion but promote the selectivity for maleic anhydride.

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Isomerization of n-Hexane over Silica-Supported Heteropolyoxometallates Promoted by Pt-Ce Oxides Abdelaziz GHERIB*;Ahmed AOUISSI;Alain RIVES;Michel FOURNIER;Robert HUBAUT 2007, 28 (12):  1041-1046.  Abstract ( 2040 )   [Full Text(HTML)] () PDF (296KB) ( 804 )   Catalysts based on Keggin-type heteropolyacids and reduced Pt-Ce oxides supported on silica were prepared for their use in isomerization of n-hexane in the presence of hydrogen. These mixed oxides were either used alone or mixed with silica-supported heteropolyacids. The catalysts after oxidation, reduction, and catalytic tests were characterized byX-raydiffraction, Fourier transform infrared spectroscopy, Fourier transform Raman spectroscopy, thermogravimetry, and N2 adsorption. The objective of the present study is the selection of the catalyst having the best isomer (branched) yield under optimum operating conditions (reaction temperature, reduction temperature, flow duration, etc.). The results show that the presence of the reduced oxides is not only beneficial for eliminating coke deposition but also effective for maintaining the structure of silica-supported heteropolyacids during reaction. Moreover, the better activity and the higher selectivity for isomers can be found with these samples.

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Deactivation of CeO2-Promoted Co/SiO2 Fischer-Tropsch Catalysts DAI Xiaoping;YU Changchun*;LI Ranjia 2007, 28 (12):  1047-1052.  Abstract ( 2059 )   [Full Text(HTML)] () PDF (363KB) ( 1323 )   The catalytic performance of the CeO2-Co/SiO2 catalyst was investigated for Fischer-Tropsch synthesis on a lab-scale fixed-bed reactor filled with1.5 Lcatalyst(1-3mm) for 300 h under the reaction conditions of 1.5 MPa, 488 K, 400 h-1. The catalyst was characterized by temperature-programmed reduction,X-raydiffraction (XRD), andX-rayphotoelectron spectroscopy. The catalyst exhibited a CO conversion of 41%, a C5+selectivity of 85%, and a CH4 selectivity of 10%. XRD results revealed the presence of CoO and cobalt silicate species on the catalyst that was located near the outlet of the reactor after reaction. It was proposed that the cobalt silicate species was formed through the reaction 2Co+SiO2+2H2O→Co2SiO4+2H2 via a CoO intermediate, which was kinetically restricted under typical Fischer-Tropsch synthesis conditions.

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Selective Synthesis of Gem-Diacetates from Aldehydes and Acetic Anhydride Catalyzed by Acetic Acid-Assisted Copper o-Toluenesulfonate WANG Min*;SONG Zhiguo;GONG Hong;JIANG Heng 2007, 28 (12):  1053-1056.  Abstract ( 2813 )   [Full Text(HTML)] () PDF (179KB) ( 1095 )   Gem-diacetates were synthesized from corresponding aromatic or aliphatic aldehydes and acetic anhydride catalysed by acetic acid-assisted copper o-toluenesulfonate as synergistic catalysts at room temperature under solvent-free conditions. The catalytic activity of acetic acid-assisted copper o-toluenesulfonate was much higher than that without acetic acid under the same conditions. Only a molar ratio of 0.3% of copper o-toluenesulfonate to aldehyde was needed to complete the reaction in short time. After reaction, the copper o-toluenesulfonate could be easily recovered by phase separation and could be reused five times without distinct decrease in its catalytic activity.

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Asymmetric Hydrogenation of Benzalacetone Catalyzed by Chiral Diamine-Modified Ru-TPP/γ-Al2O3 MING Fangyong;WANG Jinbo;FU Haiyan;CHEN Jun;CHEN Hua*;LI Xianjun 2007, 28 (12):  1057-1061.  Abstract ( 2210 )   [Full Text(HTML)] () PDF (256KB) ( 850 )   The enantioselective hydrogenation of benzalacetone was catalyzed by chiral diamine-modified Ru-TPP/γ-Al2O3(TPP=triphenylphosphine), and the effect of chiral diamines, such as (1S,2S)-DPEN ((1S,2S)-1,2-diphenyl-1,2-ethylenediamine), (S)-1,1-di(4-anisyl)-2-isopropyl-1,2-ethylenediamine, (8S,9S)-9-amino (9-deoxy) dihydrocinchonidine, and (1S,2S)-1,2-diaminocyclohexane on the hydrogenation was investigated. The results showed that (1S,2S)-DPEN could efficiently improve the hydrogenation activity and the selectivity for benzalacetone. Under the optimum reaction conditions of 40 ℃, H2 pressure of 4.0 MPa in K2CO3/i-PrOH+H2O solution, and (1S,2S)-DPEN as the chiral modifier, the conversion and the selectivity for the unsaturated alcohol reached 99% and 98%, respectively, and the ee value of the unsaturated alcohol was up to 47%.

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Effect of Composition of Raw Materials on Structure and Dimethyl Ether Synthesis Activity of Cu-Zn-Al Catalyst Prepared by Complete Liquid Phase Method FAN Jinchuan;WU Hui;HUANG Wei*;SHI Yu;XIE Kechang 2007, 28 (12):  1062-1066.  Abstract ( 2047 )   [Full Text(HTML)] () PDF (330KB) ( 1077 )   The Cu-Zn-Al bifunctional slurry catalyst was prepared by a complete liquid phase method and characterized byX-raydiffraction,N2 adsorption,X-rayphotoelectron spectroscopy, and H2 temperature-programmed reduction. The effects of Al content and Cu/Zn molar ratio on the catalytic activity of the catalyst for dimethyl ether synthesis from syngas were investigated. The competitive enrichment of Zn and Al on the catalyst surface was dominating, and increasing the Cu content could not obviously increase the Cu amount on the catalyst surface. This is because Al was enriched faster on the catalyst surface than Cu under the reaction conditions in the case of the catalyst with higher Cu content. The catalyst withn(Cu)∶n(Zn)∶n(Al)=2∶1∶4 had the most favorable bulk structure and surface properties, such as the least Cu particle size, the highest dispersion degree, the excellent reductive character, the most strong interaction between metals, and the biggest probable pore radius. Therefore, this catalyst showed the best catalytic performance.

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Influence of Surfactant on Performance of CeZrYO Oxygen Storage Material SHEN Mei;GONG Maochu;YUAN Shuhua;GUO Jiaxiu;CHEN Yaoqiang* 2007, 28 (12):  1067-1071.  Abstract ( 2129 )   [Full Text(HTML)] () PDF (321KB) ( 978 )   A CeO2-ZrO2-Y2O3 oxygen storage material was prepared by a surfactant polyethylene glycol-modified coprecipitation method. The influence of the surfactant amount and addition manner on the performance of the oxygen storage material was investigated in detail. The crystal structure, oxygen storage capacity (OSC), reduction performance, and textural properties of the material were characterized usingX-raydiffraction, oxygen pulse adsorption, H2 temperature-programmed reduction, and N2 adsorption. The surfactant amount and addition manner significantly influenced the performance of the oxygen storage material. With the increase of the surfactant amount, the OSC of the material first increased and then decreased,and reached the highest value when the surfactant amount was 50%. Compared with the material prepared by adding all the surfactant before the precipitation step, the material prepared by adding the surfactant in twice (before the precipitation step and before the dryness step) had larger specific surface area and pore volume and better anti-high temperature aging. When the surfactant was added by once, the material lost the pores smaller than 10 nm after calcination at1000℃, but when the surfactant was added in twice, the material still maintained these pores after calcination.

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Low-Temperature Preparation of Phthalocyanine-Sensitized Mischcrystal TiO2 Film and Its Catalysis for Degradation of Rhodamine B YANG Hui;*;SHEN Qianhong;GAO Jiwei; 2007, 28 (12):  1072-1076.  Abstract ( 2376 )   [Full Text(HTML)] () PDF (335KB) ( 930 )   Phthalocyanine-sensitized TiO2 sol samples were prepared through a sol-gel method using copper(Ⅱ) phthalocyanine tetrasulfonic acid (CuPcTs) as a sensitizer. Phthalocyanine-sensitized TiO2 (CuPcTs-TiO2) film samples were obtained from the as-prepared TiO2 sol by a dip-coating technique at room temperature. XRD, UV-Vis, and SEM were adopted to characterize the samples, and the degradation of rhodamine B was employed as the model reaction to evaluate the photocatalytic activity of CuPcTs-TiO2 film under the visible light. The results indicated that the TiO2 film is composed of the anatase-brookite-rutile mischcrystal phase, and thus the CuPcTs-TiO2 film samples have higher catalytic activity. The sensitization of CuPcTs can enhance visible-light catalytic activity of the TiO2 film, but too much CuPcTs can decrease its catalytic activity. Under the visible light illumination, rhodamine B first turns into rhodamine via the N-de-ethylation, and the intermediate product is subsequently degraded. The catalytic activity of the CuPcTs-TiO2 film samples becomes stable after being used2-3times. The preparation method is favorable for the firm loading of CuPcTs in TiO2 film, and thus ensures the stability for repeated use of the CuPcTs-TiO2 film.

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Preferential CO Oxidation on Ce-Promoted Pt/γ-Al2O3Catalysts under H2-Rich Atmosphere LIU Huanling;MA Lei*;SHAO Saibing;LI Zenghe;WANG Aiqin;HUANG Yanqiang;ZHANG Tao* 2007, 28 (12):  1077-1082.  Abstract ( 2214 )   [Full Text(HTML)] () PDF (378KB) ( 803 )   Preferential CO oxidation (PROX) under hydrogen-rich atmosphere was investigated over Ce-promoted Pt/γ-Al2O3catalysts. The preparation procedures and conditions,including co-deposition-precipitation (CP), sequential deposition-precipitation (SP), and deposition-precipitation temperature, had great impacts on the catalytic activity. Among the catalysts investigated, the Pt-Ce/γ-Al2O3-CP-80 catalyst prepared by co-deposition-precipitation at 80 ℃ showed the best catalytic performance with the maximum CO conversion of 85% at 120 ℃. The catalysts prepared under different conditions were further characterized by temperature-programmed reduction (H2-TPR) and in situ DRIFTS, and the promoting role of Ce was clarified.

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Highly Efficient Photocatalyst InVO4/CNTs for Water Decomposition to Produce Hydrogen under Visible Light Irradiation XU Lixian;MA Chongfang;SANG Lixia*;LI Qunwei;DAI Hongxing*;HE Hong 2007, 28 (12):  1083-1088.  Abstract ( 2375 )   [Full Text(HTML)] () PDF (411KB) ( 1198 )   The InVO4/CNTs photocatalyst was prepared by the ethanol thermal method using cetyltrimethylammonium bromide (CTAB) as the template and carbon nanotubes (CNTs) as the support. The morphology, crystal structure, surface area, and photon absorption properties of the synthesized InVO4/CNTs were characterized by transmission electron microscopy, high-resolution scanning electron microscopy,X-raydiffraction, N2 adsorption, and UV-Vis spectroscopy. The water decomposition photoactivity of the catalyst was investigated using a 300 W Xe lamp as light source. The results show that InVO4 particles are homogeneously dispersed on the surface of CNTs. The particle size is about 10 nm, and the surface area of InVO4/CNTs reaches 102 m2/g. The visible light (λ＞420 nm) response of InVO4/CNTs is greatly improved as compared with the bulk InVO4. The average H2 evolution rates from pure H2O and 20% aqueous methanol solution within4 hare 156 and 217 μmol/(g•h), respectively, under Xe lamp irradiation. The high photocatalytic activity of InVO4/CNTs is related to the electronic properties of the CNTs support.

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Influence of Environmental Humidity on the Photocatalytic Oxidation of Toluene by TiO2 Loaded on Activated Carbon Fibers GUO Ting;BAI Zhipeng*;WU Can;ZHU Tan 2007, 28 (12):  1089-1095.  Abstract ( 2361 )   [Full Text(HTML)] () PDF (490KB) ( 1129 )   Photocatalytic oxidation (PCO) of toluene by TiO2 loaded on activated carbon fibers (ACF) in an environmental conditions-controlled chamber was investigated. The TiO2/ACF catalyst was characterized by N2 adsorption for pore structure and scanning electron microscopy for morphology. The remnant of toluene and the accumulation of intermediates on the TiO2/ACF catalyst under different relative humidity (RH) were determined by GC-MS and GC-FID. The results showed that the PCO conversion rate of toluene increased with the increase of RH in the chamber. The species of intermediates were the same at all RH levels. However, the accumulation amounts of side chain oxidation intermediates (benzyl alcohol, benzaldehyde, and benzoic acid) were much more than that of aromatic ring oxidation intermediates (cresol and p-toluquinone). Elevated RH increased the accumulation of all intermediates except benzaldehyde. These results suggested that environmental humidity plays an important role in the PCO of toluene, which affects both the PCO rate and the PCO process. Although methyl group oxidation is the major path, aromatic ring oxidation, which is not the expected path for the PCO of toluene, is enhanced when the RH increases. The roles of water in the PCO of toluene were discussed.

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Preparation and Characterization of Presulfidation-Free MoNiP/Al2O3 Catalyst for Thiophene Hydrodesulfurization LIN Ling;YI Xiaodong*;QIU Bo;WANG Yuemin;LI Tianfu;FANG Weiping*;WAN Huilin 2007, 28 (12):  1096-1100.  Abstract ( 2147 )   [Full Text(HTML)] () PDF (264KB) ( 837 )   A new type of MoNiP/Al2O3 catalyst for thiophene hydrodesulfurization was prepared by the co-impregnation method, wherein a suitable amount of citric acid was added in the Mo-Ni-P-O impregnation solution. The catalyst exhibits high activity for thiophene hydrodesulfurization under presulfidation- and calcination-free conditions. The catalyst was characterized by N2 adsorption, temperature-programmed reduction,X-rayphotoelectron spectroscopy, infrared spectroscopy, and elemental analysis methods. The effects of citric acid on the structure and activity of the MoNiP/Al2O3 catalyst were studied. The results show that the addition of citric acid weakens the interaction between the active metal components and support, improves dispersion of active metal components on the support surface, and promotes the reduction and sulfidation of the catalyst by sulfur-containing feedstocks. Therefore, the hydrodesulfurization activity of the catalyst is improved.

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Oxidation of Benzyl Alcohol to Benzaldehyde Catalyzed by Chromium Schiff Base Complexes Immobilized on Mesoporous Supports WANG Xiaoli;WU Gongde;LI Junping;XIAO Fukui;WEI Wei*;SUN Yuhan 2007, 28 (12):  1101-1106.  Abstract ( 2221 )   [Full Text(HTML)] () PDF (348KB) ( 1074 )   In order to investigate the effect of different mesoporous supports on the catalytic performance of heterogeneous complexes, three representative siliceous mesoporous materials (SiO2, MCM-41, and SBA-15) were selected as supports to immobilize the same chromium salen Schiff base complex. The coordination structure and textural properties of the heterogeneous complexes were characterized by various physico-chemical measurements such as FT-IR, UV-Vis, XRD, N2 adsorption, and elemental analysis. The heterogeneous complexes were effective catalysts for the selective oxidation of benzyl alcohol to benzaldehyde using 30%H2O2 as the oxidant, and they all exhibited much better catalytic performance than their homogeneous analogues. Simultaneously, the catalytic performance of the heterogeneous complexes was also closely related to the used supports, and the complex Cr(salen)/MCM-41 exhibited the best catalytic performance. Under the optimal reaction conditions, the conversion of benzyl alcohol could reach 52.5% with 100% of selectivity for benzaldehyde. In addition, the catalytic performance was remained after being reused 4 times.

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Density Functional Theory Study of Hydrogen Dissociation on Ni-Doped Magnesium (0001) Surface JIANG Tao;CHU Hailiang;QI Yanni;LI Weixue*;SUN Lixian* 2007, 28 (12):  1107-1111.  Abstract ( 2021 )   [Full Text(HTML)] () PDF (320KB) ( 960 )   Hydrogen dissociation on Ni-doped Mg(0001) surface was studied by density functional theory calculations. Using the fixed-bond method, a dissociation barrier of 0.09 eV was obtained in contrast to 1.15 eV on a clean Mg(0001) surface reported in the literature. Electronic structure analysis shows that the decrease of the dissociation barrier comes from filling of the σ* orbital due to the back donation through the doped Ni atom. The results indicate that the kinetics of hydrogen uptake is dramatically enhanced by doping transition metal catalysts.

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Properties of MgAlCuFe Complex Oxides for FCC Desulfurization: Effect of Metal Salt Precursors CHENG Wenping;WANG Wenjuan;LIU Ling;ZHAO Yuechang;YANG Jianguo*;HE Mingyuan 2007, 28 (12):  1112-1116.  Abstract ( 2001 )   [Full Text(HTML)] () PDF (358KB) ( 985 )   A series of MgAlCuFe complex oxides used for the removal of SOx from FCC flue gas were prepared by decomposition of MgAlCuFe hydrotalcite precursors at 700 ℃ for 6 h. The influence of different metal salts in the sulfur transfer catalyst was investigated.X-raydiffraction, thermogravimetric analysis, N2 adsorption, and infrared spectroscopy showed that all the sulfur transfer catalysts exhibited a better dispersion of metal oxides in the matrix. The results of the SO2 adsorption-reduction test showed that the novel catalyst MgAlCuFe prepared from nitrates reached 1.54 g/g of total saturation adsorption capacity in6 minunder the conditions similar to those of typical FCC. These catalysts achieved high oxidative adsorption rate, short saturation time, and large reductive capacity.

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Photocatalytic Degradation of Persistent and Toxic Organic Pollutants TARIQ MAHMOOD;WANG Xuesong;CHEN Chuncheng;MA Wanhong;ZHAO Jincai* 2007, 28 (12):  1117-1122.  Abstract ( 2157 )   [Full Text(HTML)] () PDF (262KB) ( 2286 )   Studies on photocatalytic degradation of toxic and non-biodegradable organic pollutants remain a great challenge in principles, processes, and efficiencies. The main attention has been focused on the relationship between structure and efficiencies, the utilization of visible light, and the mechanisms for dioxygen activation and pollutants decomposition and/or mineralization of pollutants. Recent advances in the photocatalytic degradation by TiO2 and supported iron complexes were discussed in this review.