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Chinese Journal of Catalysis
2008, Vol. 29, No. 2
Online: 25 February 2008

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Methanol Steam Reforming over Metal Wall-Coated PdZn/Al2O3/FeCrAl Catalyst for Hydrogen Production WANG Xinxin;JIA Jingsheng;MU Xin;PAN Liwei;WANG Shudong* 2008, 29 (2):  99-101.  Abstract ( 1813 )   [Full Text(HTML)] () PDF (224KB) ( 769 )   Methanol steam reforming for hydrogen production over metal wall-coated PdZn/Al2O3/FeCrAl catalyst was investigated in a stainless steel microreformer. The results showed that the methanol conversion of 100%, selectivity of 99% to H2, outlet CO molar fraction of 0.5%, and high stability were achieved over the PdZn/Al2O3/FeCrAl catalyst under the reaction conditions of 350 ℃, methanol GHSV of 1.600 L/(g·h), and H2O/methanol molar ratio of 1.2.

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Epoxidation of Various Functionalized Olefins by a Ti-MWW/H2O2 Catalytic System LI Ningning;LIU Yueming;WU Haihong;LI Xiaohong;XIE Wei;ZHAO Zhonglin;WU Peng*;HE Mingyuan 2008, 29 (2):  102-104.  Abstract ( 2060 )   [Full Text(HTML)] () PDF (158KB) ( 738 )   The catalytic properties of Ti-MWW catalysts for the epoxidation of olefins with different functional groups using hydrogen peroxide as an oxidant were studied. Ti-MWW shows higher olefin conversion and epoxide selectivity than the conventional titanosilicate TS-1. Solvents influence the catalytic activity of Ti-MWW, and water is the best one in the epoxidation of ethyl acrylate and allyl acetate. The functional groups with high eletrophilicity and adjacent to the C=C bonds retard the catalytic activity for olefin epoxidation.

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In Situ FT-IR Study of Photocatalytic Decomposition of Formic Acid to Hydrogen on Pt/TiO2 Catalyst CHEN Tao;WU Guopeng;FENG Zhaochi;HU Gengshen;SU Weiguang;YING Pinliang;LI Can* 2008, 29 (2):  105-107.  Abstract ( 2219 )   [Full Text(HTML)] () PDF (204KB) ( 1077 )   The anaerobic photocatalytic decomposition of formic acid to hydrogen on Pt/TiO2 was studied by in situ FT-IR spectroscopy. The molecularly adsorbed formic acid species is transformed to a formate species, and the formate species is transformed to carbonates during this reaction. The addition of water vapor in the reaction system strongly accelerates this photocatalytic reaction and promotes the H2 production efficiency. The possible mechanism of the reaction is proposed.

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Preparation of Ce-Zr-La-Al2O3 and Supported Single Palladium Three-Way Catalysts CAI Li;ZHAO Ming;PI Zhan;GONG Maochu;CHEN Yaoqiang* 2008, 29 (2):  108-112.  Abstract ( 2679 )   [Full Text(HTML)] () PDF (287KB) ( 867 )   Ce-Zr-La-Al2O3 (CZLA) was prepared by co-precipitation and incipient wet impregnation methods and characterized by N2 adsorption andX-raydiffraction. 2%Pd/CZLA catalysts were prepared and studied by temperature-programmed reduction and activity tests. The CZLA supports prepared by the two methods showed good structural, textural, and oxygen storage properties, and the CZLA prepared by co-precipitation was more resistant to aging. The single Pd catalysts showed low light-off temperature and high three-way catalytic activity, especially the excellent NO conversion and aging resistance.

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Effect of Hydrohalogenation of Metal/Zeolite Catalysts for Cyclohexene Hydroconversion Ⅱ. Rhenium/H-ZSM-5 Catalysts Ahmed K. ABOUL-GHEIT*;Noha A. K. ABOUL-GHEIT;Ahmed E. AWADALLAH 2008, 29 (2):  113-122.  Abstract ( 2061 )   [Full Text(HTML)] () PDF (660KB) ( 1087 )   A post-preparation treatment of the Re/H-ZSM-5 catalyst with HCl or HF was performed, and its effect on cyclohexene hydroconversion reactions at 50-400℃ in a continuous flow reactor was investigated. The HF treatment significantly improved the catalytic activity for cyclohexene hydrogenation to cyclohexane and methylcyclopentenes to methylcyclopentane in comparison to the HCl treatment. This is principally attributed to the higher Re dispersion and enhancement of the acid site number and strength. Thereupon occurs the highest hydrocracking activity and the lowest dehydrogenation activity for cyclohexene to cyclohexadienes on Re/H-ZSM-5(HF) by virtue of the highest strength of acid sites. The untreated Re/H-ZSM-5 catalyst exhibited the highest dehydrogenation activity for aromatics production, which may be attributed to the lowest quantity of extraframework Al and Si depositing in the pores and cavities of the zeolite support. Industrially, the relative amounts of xylene isomers produced on the hydrohalogenated catalysts are of interest. The amount of p-xylenewas higher thanm-xyleneon the HF-treated catalyst;m- andp-xylenespresented almost equal values on the HCl-treated catalyst;m-xyleneexceededp-xyleneon the untreated catalyst.O-xyleneis almost equal to the sum ofp- andm-xylenesin all cases.

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Epoxidation of Styrene and Its Derivatives Catalyzed by a Multi-component Ionic Liquid Functionalized with Manganese Porphyrin ZHANG Hongjiao;LIU Ye*;CAI Yueqin;WU Haihong;LIU Xiuli 2008, 29 (2):  127-133.  Abstract ( 2125 )   [Full Text(HTML)] () PDF (327KB) ( 1041 )   The ionic manganese porphyrin bearing trimethylbenzylammonium cation and PF-6 anion ([MnTTMAPP][PF6]5) was mixed with the ionic liquids of [bzmim]BF4 and [bmim]BF4 to build up a manganese porphyrin-functionalized multi-component ionic liquid (MnPy-MIL), which was used as a catalytic system for expoxidation of styrene and its derivatives with oxidant PhIO. Compared with the traditional neutral manganese porphyrin, the MnPy-MIL system has advantages of suppression of oxidation degradation and self-aggregation, recyclability, and no requirements of additional axial ligands and organic solvents. The presence of a small amount of water could improve the catalytic performance of MnPy-MIL.

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Preparation and Characterization of Au/ Ce1-xZrxO2 Catalysts and Their Catalytic Performance for CO Oxidation and Water-Gas Shift Reaction LIAO Weiping;DONG Yuanyuan;JIN Mingshan;HE Tao;SUO Zhanghuai* 2008, 29 (2):  134-140.  Abstract ( 2126 )   [Full Text(HTML)] () PDF (487KB) ( 977 )   A series of Ce1-xZrxO2 (x=0, 0.1, 0.3, 0.5, 0.7, 0.9, 1.0) composite oxides were prepared by the co-precipitation method. Gold catalysts with 1% loading supported on CeO2, ZrO2, and Ce1-xZrxO2 were prepared by the modified impregnation method. The effect of Zr/Ce molar ratios on the activity for low-temperature CO oxidation and water-gas shift reaction was studied. All samples were characterized by nitrogen adsorption, X-ray diffraction, transmission electron microscopy, and H2 temperature-programmed reduction. The results showed that compared with pure CeO2 and ZrO2, the surface area of Ce1-xZrxO2 increases and its pore diameter decreases slightly. The presence of zirconium oxide in cerium oxide makes the reduction of cerium ions on the surface more difficult whereas it makes the reduction of the cerium ions in the phase easier. Loading gold particles onto Ce1-xZrxO2 support improves the reduction of the support, and good dispersion of gold particles is found on ZrO2 and Ce1-xZrxO2 supports due to the strong interaction between the gold particles and the oxide supports. These catalysts show good activity for low-temperature CO oxidation and water-gas shift reaction in the order Au/ZrO2>Au/ Ce1-xZrxO2>Au/CeO2. However, Au/Ce0.5Zr0.5O2 gives higher activity with 80% CO conversion at 623 K for water-gas shift reaction. Large pore diameter of ZrO2 and Ce1-xZrxO2 with respect to CeO2 is responsible for the high activity.

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Reaction Kinetics of Ethyl Lactate Synthesis from Lactic Acid and Ethanol Catalyzed by Lipase ZHAO Tiantao;;ZHANG Lijie;GAO Jing*;HUANG Zhihong;QUAN Xuejun 2008, 29 (2):  141-144.  Abstract ( 2430 )   [Full Text(HTML)] () PDF (244KB) ( 1197 )   The reaction kinetics of lipase-catalyzed esterification of lactic acid and ethanol was studied. The reaction rate could be described in terms of a ping-pong bi-bi mechanism and double-substrate inhibition. No evidence of any diffusion limitation that affected the kinetics was detected by the comparison between the time constants for the reaction (tR) and diffusion (tD). The predicted values of the corresponding mechanism reaction fitted the experimental data very well, and the rate constants were obtained by non-linear fitting analysis. The inhibition constants for lactic acid (A) and ethanol (B) were KiA=10.7 mmol/L and KiB=275.0 mmol/L, respectively, which suggested that lactic acid, being a short-chain polar acid, caused the enzyme inactivation more seriously than ethanol. The lactic acid was concentrated in the micro-aqueous layer and caused a pH drop, leading to the enzyme inactivation in its microenvironment, and the competitive inhibition of enzyme by lactic acid existed during the lipase-catalyzed esterification reaction.

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Equilibrium Uptake and Adsorption State of Pd Precursor in Preparation of Pd/C Catalyst by Impregnation LIANG Qiuxia;MA Lei;ZHENG Yifan;LU Chunshan;ZHANG Qunfeng;LI Xiaonian* 2008, 29 (2):  145-152.  Abstract ( 2176 )   [Full Text(HTML)] () PDF (546KB) ( 1182 )   A series of activated carbon used as supports were pretreated with different concentrations of HNO3. Pd/C catalysts were then prepared by impregnation using H2PdCl4 solution as the Pd precursor. The results of adsorption experiments in the impregnation process indicated that the equilibrium uptake of the Pd precursor on the surface of activated carbon decreased with increasing HNO3 concentration for the pretreatment. When undiluted HNO3 was used, only 62.54% of Pd precursor was adsorbed on the surface of activated carbon, and about 37.46% of Pd precursor was still reserved in the slurry. The Pd precursor equilibrium uptake was highly dependent upon the point-of-zero charge of the activated carbon. Compared with the surface oxygen anchoring mechanism, the surface charge model gives a better explanation of the adsorption experimental results. Pd particle size was initially decreased with increasing HNO3 concentration (≤5%) and then increased with further increasing HNO3 concentration (>10%). No obvious correlation between the Pd precursor equilibrium uptake and the Pd particle size was found because the particle size of Pd was also affected by Pd precursor adsorption species and their amounts. Formation of PdCly-x adsorption species was inhibited by the increase of oxygen-containing groups on the activated carbon surface. When a low HNO3 concentration (≤5%) was used for the pretreatment of activated carbon, PdCly-x and Pd0 were the main adsorption states of Pd precursor, whereas when the HNO3 concentration was high (>5%), PdCly-x was not detected.

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H2 Production from Steam Reforming of High Energy Density Motor Fuel with SulfurII. In Situ DRIFTS Studies on Pt/Ce0.8Gd0.2O1.9 Catalyst CHEN Jinchun;XUE Qingsong;LU Yong*;HE Mingyuan 2008, 29 (2):  153-158.  Abstract ( 2192 )   [Full Text(HTML)] () PDF (522KB) ( 952 )   Sulfur-tolerant Pt/Ce0.8Gd0.2O1.9 (Pt/CGO) and Pt/Al2O3 catalysts were characterized by means of in situ diffuse reflectance infrared fourier transform spectroscopy (DRIFTS) for adsorption of CO and co-adsorption of CO with thiophene and hydrogen sulfide. CO adsorbed on the surface of 1.6%Pt/CGO-800 catalyst (calcined at 800 ℃) showed an IR peak at 2104cm-1, which is 34 cm-1higher than that (2070cm-1) on the surface of 1.6%Pt/Al2O3-500 catalyst. CO adsorbed on the surface of 1.6%Pt/CGO-600 catalyst exhibited two IR peaks, a main peak likewise at 2108cm-1 and a shoulder peak at 2085cm-1. For 1.6%Pt/CGO-800, co-adsorbed thiophene caused a shift of the CO peak from 2104cm-1to 2090cm-1. For 1.6%Pt/CGO-600, the main peak was shifted from 2108cm-1 to 2096cm-1 with a slight reduction of peak intensity, and the shoulder CO peak at2085cm-1disappeared. For 1.6%Pt/Al2O3-500, after thiophene was co-adsorbed, the CO peak at 2070cm-1 shifted about 30 cm-1to a lower wavenumbers and the peak intensity significantly decreased. Subsequently adsorbed H2S only caused a 2-4 cm-1red shift of CO peaks at 2104cm-1 for 1.6%Pt/CGO-800 and 2108cm-1 for 1.6%Pt/CGO-600 but led to a complete loss of the CO adsorption ability of 1.6%Pt/Al2O3-500. These results indicated that strong electron-deficient Pt sites that were resistant to sulfur poison were formed on the Pt/CGO catalysts and calcination at 800 ℃ of Pt/CGO resulted in the formation of unique Pt sites that had the highest sulfur tolerance.

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Direct Vapor-Phase Synthesis of Indole: Effect of MgO on the Performance of Cu/SiO2 Catalyst LIU Jing;LI Chunmei;HUO Xiaomin;SHI Lei*;SUN Qi 2008, 29 (2):  159-162.  Abstract ( 2057 )   [Full Text(HTML)] () PDF (279KB) ( 734 )   Magnesia was used as the promoter in the Cu/SiO2 catalyst for direct vapor-phase synthesis of indole from aniline and ethylene glycol. The catalyst was characterized by XRD, H2-TPR, and TG. The results showed that a suitable amount of MgO (i.e., 0.17 mmol/g) remarkably increased the stability and activity of the catalyst. The MgO additive improved the dispersion of copper phases on the silica and prevented them from sintering in the reaction process. There existed an interaction between CuO and MgO, which inhibited the sintering of copper. The MgO promoter could suppress the coking of this copper-based catalyst.

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Effect of Rare Earth Ion Doping on the Photocatalytic Activity of TiO2 for Hydrogen Evolution HUANG Cuiying*;ZHANG Lancui;LI Xiaohui 2008, 29 (2):  163-166.  Abstract ( 2555 )   [Full Text(HTML)] () PDF (272KB) ( 935 )   TiO2 catalysts doped with different rare earth ions were prepared by the sol-gel method and characterized by X-ray diffraction, transmission electron microscopy, and N2 adsorption. The photocatalytic activity for hydrogen evolution from water decomposition under UV light irradiation was investigated. Doping with rare earth ions restrained the growth of TiO2 particles, improved the particle dispersion, increased the BET surface area, and thus significantly enhanced the photocatalytic activity of TiO2 for H2 evolution. Among the catalysts, Gd3+/TiO2 had the smallest particle size, the best particle dispersion, and the highest BET surface area (35 times higher than that of the undoped TiO2). The gelling time varied with different rare earth ions. The longer the gelling time, the larger the BET surface area. A comparison between La3+/TiO2 and Gd3+/TiO2 indicated that the photocatalytic activity was not linear with the surface area. Moreover, the electronic configuration of rare earth ions had a significant effect on the photocatalytic activity of RE3+/TiO2. TiO2 samples doped with La3+ having a full-empty electronic configuration and Gd3+having a half-filled electronic configuration had higher photocatalytic activity for hydrogen evolution (3.69 and 3.72 times higher) than that of the undoped TiO2.

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Characterization and Slurry Fischer-Tropsch Synthesis Performance of Fe/Cu/K/SiO2 Catalysts with Different Scaled Up Levels HOU Wenjuan;WU Baoshan*;BAI Liang;XIANG Hongwei;LI Yongwang 2008, 29 (2):  167-173.  Abstract ( 2161 )   [Full Text(HTML)] () PDF (534KB) ( 885 )   Two spherical Fe/Cu/K/SiO2 catalysts with different preparation scale for slurry Fischer-Tropsch (FT) synthesis were prepared by a combination of co-precipitated and spray drying method. The pellet size of the catalyst with a laboratory scale is 5-15μm, whereas that is 40-60μm for the scaled-up catalyst. N2 physical adsorption, H2 temperature-programmed reduction, CO2 temperature-programmed desorption, Mössbauer spectroscopy, and X-ray diffraction were used to characterize the textural properties, reduction and carburization behavior, and phase transformation of the two catalysts. The results show that the scaled-up catalyst has larger crystallize size and pore volume, lower BET surface area, and lower surface basicity than the laboratory-scale catalyst. Moreover, the scaled-up catalyst was more difficult to be reduced and carburized. However, the results of FT synthesis in a slurry bed indicate that the scaled-up catalyst exhibits comparative activity, better reaction stability, and higher selectivity for olefin and heavy hydrocarbons. Scanning electron microscopy results suggest a better attrition resistance of the scaled-up catalyst during the FT reaction tests.

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Supercritical Phase Fischer-Tropsch Synthesis Reaction over Highly Active Fused Iron Catalyst at Low Temperature TANG Haodong;LIU Huazhang*;YANG Xiazhen;LI Ying 2008, 29 (2):  174-178.  Abstract ( 2476 )   [Full Text(HTML)] () PDF (213KB) ( 958 )   The Fischer-Tropsch synthesis (FTS) reaction over the fused iron catalyst in the presence of supercritical media was investigated in a fixed-bed reactor. Compared with the gas-phase FTS reaction, the presence of supercritical media resulted in an increase in CO conversion, olefin selectivity, and C5+selectivity, but a decrease in CH4 selectivity owing to the fact that diffusion was easier in the supercritical media and less inactive carbon was deposited on the catalyst surface. The effects of supercritical media, temperature, pressure, H2/CO ratio, and syngas flow rate on the supercritical phase FTS reaction were investigated. The n-pentane, n-hexane, n-heptane, and n-octane had similar effects on the FTS reaction. The performance of FTS reaction could be improved when the reaction temperature and pressure were higher than the critical points of the media owing to the better mass and heat transportation in supercritical media.

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Deactivation of the Industrial Catalyst for Ethylbenzene Dehydrogenation to Styrene LIAO Shijie;CHEN Tong;MIAO Changxi;YANG Weimin;XIE Zaiku;CHEN Qingling;* 2008, 29 (2):  179-184.  Abstract ( 2453 )   [Full Text(HTML)] () PDF (541KB) ( 1367 )   The deactivation of the prepared industrial Fe-K catalyst for ethylbenzene dehydrogenation to styrene was characterized by X-ray powder diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, temperature-programmed reduction, and Mossbauer spectroscopy. The activity of fresh and spent catalyst samples was evaluated in a fixed-bed reactor. The results showed that regeneration of the spent catalyst by coke burning could improve activity, but the activity was reduced to the level of the spent catalyst after a short time of reaction. The characterization results indicated that coke deposition, catalyst sintering, and potassium loss were not responsible for the catalyst deactivation. However, the migration and uneven redistribution of potassium and reduction of Fe3+were the major reasons for the deactivation.

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Heck and Suzuki Reactions of Aryl Halides Catalyzed by 1,3-Dialkylimidazolinium/Palladium Sedat YAS;AR;smail ZDEMR*BekirC;ETNKAYA 2008, 29 (2):  185-190.  Abstract ( 2019 )   [Full Text(HTML)] () PDF (315KB) ( 898 )   New, sterically demanding1,3-dialkylimidazolinium salts used as N-heterocyclic carbene precursors were synthesized and characterized. These salts, combined with palladium acetate, provided active catalysts for Heck and suzuki cross-coupling of aryl chlorides and bromides under mild conditions.

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Catalytic Activity of Pt/SAPO-34 for Selective Catalytic Reduction of NO by H2 at Low Temperature WU Peng;LIU Yunxia;ZHANG Fuxiang;WU Guangjun;L?Baocheng;GUAN Naijia* 2008, 29 (2):  191-196.  Abstract ( 2798 )   [Full Text(HTML)] () PDF (434KB) ( 931 )   Selective catalytic reduction of NO by H2 (H2-SCR) under lean burn conditions at low temperature(60-260 ℃) was studied over the SAPO-34-supported platinum catalyst. The effects of supports, Pt loading, and reaction conditions on the catalyst activity were investigated. The NO conversion of 78.8% and N2 selectivity of 75.2% were achieved on the 0.5%Pt/SAPO-34 catalyst at GHSV of80000h-1and 120 ℃, superior to that on the Pt/SiO2 and Pt/ZSM-5 catalysts. The decrease in GHSV further enhanced the NO conversion to as high as 100% at GHSV of 10000h-1. The reaction mechanism of NO in H2-SCR over 0.5%Pt/SAPO-34 was investigated using in situ DRIFTS. The results showed that nitrate species were the main reaction intermediates of NO reduction.

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Hollow Graphitic Cabon as Electrocatalyst Support for Direct Ethanol Fuel Cells JIA Ziqi;SUN Gongquan*;CAO Lei;WANG Guoxiong;XIN Qin 2008, 29 (2):  197-201.  Abstract ( 2380 )   [Full Text(HTML)] () PDF (377KB) ( 1083 )   A hollow graphitic carbon (HGC) material was synthesized using resorcinol, phenol, and formaldehyde. The characterization by transmission electron microscopy (TEM), N2 adsorption-desorption, and Raman spectroscopy showed that the highly graphitized HGC is a mesoporous material with an average pore size of 36 nm. Compared with the commercial Vulcan XC-72R carbon, HGC has more mesopore volume and higher graphitic character. The 45%PtSn/C electrocatalysts were prepared using HGC and XC-72R as supports and characterized by X-ray diffraction and TEM. These two kinds of electrocatalysts have similar particle size and lattice parameter. The single cell test of DEFCs (direct alcohol fuel cells) showed that the peak power density is increased from 54 mW/cm2 of PtSn/XC-72R to 62 mW/cm2 of PtSn/HGC.