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Chinese Journal of Catalysis
2006, Vol. 27, No. 6
Online: 25 June 2006

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Hydration of Cyclohexene in a Fixed-Bed Reactor with Micromixer YANG Fu1, CHEN Guangwen1, LI Hengqiang1, GUO Xinwen2, WANG Xiangsheng2 2006, 27 (6):  459-461.  Abstract ( 1762 )   [Full Text(HTML)] () PDF (228KB) ( 698 )   Cyclohexene hydration was investigated in a fixed-bed reactor with a micromixer. The results showed that the use of the micromixer increased the solubility of cyclohexene in the aqueous phase and thus promoted the reaction. The conversion of cyclohexene and selectivity for cyclohexanol reached 9% and 99%, respectively. The reaction time was shortened to 0.3 h.

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Methane Partial Oxidation in Liquid Phase Using Vanadium-Containing Heteropolyacid Catalysts in Oleum CHEN Liyu1,2, YANG Bolun1, ZHANG Xiucheng2, DONG Wu2, ZHANG Xiaoping2 2006, 27 (6):  462-464.  Abstract ( 1943 )   [Full Text(HTML)] () PDF (170KB) ( 683 )   The partial oxidation of methane by the H5PV2Mo10O40 catalyst in oleum was studied. The effects of catalyst amount, reaction temperature, reaction time, and sulfur trioxide concentration on the methane conversion and methanol yield were investigated. Methane was transformed to methyl bisulfate first, and then methyl bisulfate was hydrolyzed to methanol. Sulfur trioxide in oleum was necessary for the reaction system. The maximum methane conversion of 48.5% and methanol yield of 41.5% were obtained under the conditions of 7.0 mmol catalyst, methane pressure of 3.5 MPa, reaction temperature of 473 K, reaction time of 3 h, and 50% sulfur trioxide concentration.

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Catalyst-Enhanced Chemical Vapor Deposition of Palladium-Platinum Bilayer Films on Polyimide ZHENG Jianhua1, ZHOU Jinlan2, YU Kaichao2, GE Xuegui1, YU Shuyan3 2006, 27 (6):  465-467.  Abstract ( 1775 )   [Full Text(HTML)] () PDF (305KB) ( 688 )   Catalyst-enhanced chemical vapor deposition of Pt and Pd-Pt bilayer films on polyimide using N2 and O2 as the carrier gases was studied. When the mixture of Pt complex and Pd complex was used as precursors in the same chamber for co-deposition of Pd and Pt, only Pt was deposited. Sequential deposition of Pd and Pt metals formed Pd-Pt bilayer films.

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Low-Temperature Catalytic Combustion of Trichloroethylene over La, Ce, and Pt Catalysts Supported on MCM-41 WANG Xingyi*, DAI Qiguang, ZHENG Yi 2006, 27 (6):  468-470.  Abstract ( 1875 )   [Full Text(HTML)] () PDF (165KB) ( 766 )   La- and Ce-incorporated Si-MCM-41 and Pt catalysts supported on these materials were prepared. The samples were characterized by small angle X-ray diffraction, N2 adsorption, extended X-ray adsorption fine structure, andtemperature-programmed desorption of NH3. The results showed that La and Ce were incorporated into the Si-MCM-41. No acidity was detected on the La- and Ce-containing catalysts. The obtained catalysts had high activity for the trichloroethylene catalytic combustion and high selectivity for CO2 and HCl.

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Mesoporous Mixed Oxide La-Co-Ce-O Catalysts Prepared by Citric Acid Complexation-Organic Template Decomposition Method LUO Jinyong, MENG Ming*, QIAN Ying, ZHA Yuqing 2006, 27 (6):  471-473.  Abstract ( 1863 )   [Full Text(HTML)] () PDF (218KB) ( 713 )   A series of La-Co-Ce-O mixed oxide catalysts with different bulk compositions were synthesized using a citric acid complexation-organic template decomposition method. The samples have high specific surface area (above 100 m2/g), very uniform pore diameter (3.7～3.9 nm), and good thermal stability. The dispersion of CeO2 and Co3O4 crystallites in the samples prepared by the organic template decomposition is much higher than that by the conventional coprecipitation method. The samples prepared using this new method display much a higher activity for CO and propane oxidation than that by coprecipitation. The catalytic oxidation activity of the catalysts is not proportional to the number of the surface cobalt atoms, but is closely related to the synergism between the surface cobalt and cerium species. The catalytic synergetic effect is exhibited when the surface cobalt and cerium are in an atomic ratio nearly to one.

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Effect of Rhodium Particle Size in Rh/SiO2 Catalyst Prepared by Microemulsion Method on Reaction Performance of CO Hydrogenation ZHOU Shutian1,2, PAN Xiulian1, BAO Xinhe1* 2006, 27 (6):  474-478.  Abstract ( 1827 )   [Full Text(HTML)] () PDF (283KB) ( 893 )   Controllable synthesis of the silica-supported rhodium catalyst with uniform particle size has been achieved through microemulsion technique by manipulating the W0 value (molar ratio of water to surfactant in the precursor). The catalyst shows a core-shell morphology, in which rhodium is encapsulated by a silica shell. The characterization of the catalyst morphology by TEM and the catalytic performance of the catalyst for CO hydrogenation indicated significant influence of the rhodium particle size. There was a minimum value of the CO conversion over the catalyst with the average rhodium particle size of 3 nm in the range of 1.8～5.0 nm. With increasing the rhodium particle size from 3 to 5.0 nm, the reactivity increased. Compared with the Rh/SiO2 catalyst prepared by the conventional impregnation method, the present catalyst had more uniform distribution of rhodium particle size and showed superior catalytic activity for CO hydrogenation, when the catalyst samples had the same loading and average particle size.

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Effects of Promoter La2O3 and Supports on Kinetic Parameters of Dissociation Activation of CH4 over Ni-Based Catalysts CUI Yuehua, XU Hengyong*, GE Qingjie, WANG Yuzhong, HOU Shoufu, LI Wenzhao 2006, 27 (6):  479-484.  Abstract ( 1875 )   [Full Text(HTML)] () PDF (388KB) ( 880 )   The influence of MgAl2O4 and α-Al2O3 supports, and La2O3 promoter on the CH4 dissociation was studied by pulsing CH4 over catalysts Ni/α-Al2O3(A), Ni/La2O3/α-Al2O3(A-L), Ni/MgAl2O4(M), and Ni/La2O3/MgAl2O4(M-L). In these unsteady pulse reactions, the carbon species coverage on the catalysts was kept less than 100% and the information about CH4 dissociation on the fresh Ni active sites was disclosed. Kinetic parameters for the CH4 dissociation over these catalysts were obtained under reaction conditions free from heat and mass transfer limitations. The CH4 dissociation activation energy (Ea) on catalysts A, A-L, M, and M-L is 90.9, 111.8, 79.5, and 85.9 kJ/mol, respectively. The Ea values on catalysts M and M-L are lower than those on catalysts A and A-L. The La2O3 promoter increases the Ea of CH4 dissociation. There is a compensation effect between the activation energy and the pre-exponential factor in the CH4 dissociation on the Ni-based catalysts, which reduces the influence of the supports and promoter on the CH4 dissociation.

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One-Pot Synthesis of Dimethyl Carbonate Catalyzedby ［bmim］BF4/CH3ONa CHEN Xiuzhi1, HU Changwen1*, SU Junhua1, YU Tao2, GAO Zhiming1 2006, 27 (6):  485-488.  Abstract ( 1850 )   [Full Text(HTML)] () PDF (256KB) ( 879 )   The one-pot synthesis of dimethyl carbonate from propylene oxide, carbon dioxide, and methanol was investigated. The catalyst adopted was a mixture of 1-butyl-3-methylimidazolium tetrafluoroborate (［bmim］-BF4) and sodium methoxide. Under the reaction conditions of 4 MPa, 5 h, and 150 ℃, the conversion of propylene oxide was above 95%, the selectivity for propylene carbonate was 87.1%. More importantly, the yield of dimethyl carbonate reached 67.6%, which is higher than the results of the previous literature using the one-pot synthesis method.

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Pd-Chitosan Complex Supported on MCM-48 for AsymmetricTransfer Hydrogenation of Prochiral Ketone XUE Ping*, WU Tao 2006, 27 (6):  489-494.  Abstract ( 1906 )   [Full Text(HTML)] () PDF (337KB) ( 791 )   A new chiral heterogeneous catalyst, Pd-chitosan(CS) complex supported on mesoporous molecular sieve MCM-48 was prepared and characterized by X-ray photoelectron spectroscopy, X-ray diffraction, and N2 adsorption-desorption measurements. The specific surface area, average pore diameter, and pore volume of the Pd-CS/MCM-48 catalyst were 527 m2/g, 2.1 nm, and 0.63 cm3/g, respectively. The asymmetric transfer hydrogenation of two prochiral ketones, acetophenone and 4-methyl-2-pentanone, was catalyzed by Pd-CS/MCM-48 using 2-propanol as the H-donor. The enantiomeric excess (ee) of (R)-1-phenylethanol reached 99.0% with a conversion of 61.9% after reaction for 4 h at 50 ℃, and the ee of (R)-4-methyl-2-pentanol was 82.4% with a conversion of 48.7% after reaction for 8 h at 50 ℃. The results indicated that the Pd-CS/MCM-48 catalyst possessed a high catalytic activity and enantioselectivity for the asymmetric transfer hydrogenation of these two prochiral ketones. Moreover, the effects of Pd content, reaction temperature, reaction time, and KOH concentration on the conversion and enantioselectivity for the asymmetric transfer hydrogenation of the prochiral ketones were investigated.

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Preparation of MCM-41 with High Nitrogen Content and Its Catalytic Performance for Knoevenagal Condensation JIANG Shaoliang, SONG Yingjun, ZHANG Fuxiang, WU Guangjun, GUAN Naijia* 2006, 27 (6):  495-500.  Abstract ( 1704 )   [Full Text(HTML)] () PDF (425KB) ( 649 )   MCM-41 with high nitrogen content was prepared by nitridation of MCM-41 with NH3 at high flow rate and low temperature. The highest nitrogen content (mass fraction) of about 26.0% was achieved in NH3 with a flow rate of 400 ml/min at 950 ℃ for 12 h. The NH3 flow rate and nitridation temperature were the key factors that influenced the nitrogen content of the nitrided MCM-41 samples, whereas the silicon source and alkali source had little effect. The nitrogen content of the nitrided samples was stable when the nitridation time was over 12 h. X-ray diffraction, N2 adsorption, transmission electron microscopy, X-ray photoelectron spectroscopy, and 29Si MAS NMR results indicated that the mesopore framework of parent MCM-41 was well preserved after nitridation. Moreover, nitrogen was incorporated into the framework of MCM-41. The nitrided MCM-41 with high nitrogen content exhibited high basic catalytic activity for Knoevenagal condensation of malononitrile and benzaldehyde owing to the slight damage of nitridation at low temperature to the framework of MCM-41.

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Synthesis of Cobalt Tetraphenylporphyrin and Its Electrocatalytic Performance for Oxygen Reduction TANG Jie, TANG Yougen*, LIU Dongren 2006, 27 (6):  501-505.  Abstract ( 1865 )   [Full Text(HTML)] () PDF (321KB) ( 1372 )   Tetraphenylporphyrin and its cobalt complex were synthesized under different conditions and characterized by infrared spectroscopy and 1H nuclear magnetic resonance. The influences of catalyst, solvent, and temperature on the yield of tetraphenylporphyrin were investigated. The effect of heat treatment on structure of cobalt tetraphenylporphyrin at different temperatures was investigated using X-ray photoelectron spectroscopy. Cathodic polarization curves of air electrode loaded with cobalt tetraphenylporphyrin were measured to evaluate the performance of heat-treated catalysts. The results showed that using p-nitrobenzoic acid as catalyst and nitrobenzene as solvent, the yield of tetraphenylporphyrin was about 32% at 200 ℃. The moiety Co[KG-45x]-[KG-20x]N4 of cobalt tetraphenylporphyrin was in a critical state under 600 ℃ heat treatment but was destroyed partly at 800 ℃. Thus the catalytic activity of cobalt tetraphenylporphyrin heat-treated at 600 ℃ was higher than that heat-treated at 800 ℃.

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In Situ Synthesis of MCM-22 Zeolite Membrane on an Alloy Foil by Hydrothermal Method ZOU Xinhua, LI Yingxia*, ZENG Jianling, CHEN Biaohua 2006, 27 (6):  506-510.  Abstract ( 1849 )   [Full Text(HTML)] () PDF (665KB) ( 853 )   The MCM-22 zeolite membrane was synthesized on an iron-chromium-aluminum alloy foil by the hydrothermal method and characterized by X-ray diffraction and scanning electron microscopy. The results showed that the surface properties of the support had an important effect on the formation of the MCM-22 zeolite membrane. The MCM-22 zeolite membrane grew much better on the alloy foil treated with acid. The precoating of Al2O3 colloid on the alloy foil could enhance the interaction between the MCM-22 zeolite membrane and the support. The amount of the mother liquid was also an important factor affecting the formation of the MCM-22 zeolite membrane, and a high quality MCM-22 zeolite membrane could be obatined with more mother liquid. If the mother liquid was not enough, there was no MCM-22 zeolite membrane formed.

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Effect of Ultrasonic Frequency on Structure of Activated Carbon and Activity of Ru/AC Catalyst for Ammonia Synthesis YU Fengwen, JI Jianbing, HUO Chao, HAN Wenfeng, LI Xiaonian, LIU Huazhang* 2006, 27 (6):  511-514.  Abstract ( 2062 )   [Full Text(HTML)] () PDF (309KB) ( 946 )   The effect of ultrasonic frequency on the structure, surface texture, and surface groups of activated carbon (AC) was investigated by field-emission scanning electron microscopy, N2 adsorption, and temperature-programmed desorption. The results showed that increasing the ultrasonic frequency could effectively remove the impurities in AC, enhance the mesopore surface area, and decrease the amount of decomposable surface groups on AC. Furthermore, the ultrasonic treatment made the surface and holes of AC clean. Under the treatment of ultrasound with a power of 100 W and a frequency of 39.0 kHz for 30 min, the ash content in AC was lower, and the mesopore surface area was moderate. The catalytic activity of a series of barium-potassium-promoted Ru/AC catalysts for ammonia synthesis was evaluated under the conditions of GHSV=10?000 h-1, 10.0 MPa, and 425 ℃. The results showed that the rate of the catalytic reaction was increased from 90.1 to 101.0 mmol/(g•h) with the increase of ultrasonic frequency from 19.7 to 39.0 kHz.

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Modification of Alumina and Its Application in the Direct Synthesis of Dimethyl Ether from Syngas MAO Dongsen1,2*, YANG Weimin2, ZHANG Bin2, LU Guanzhong1 2006, 27 (6):  515-521.  Abstract ( 1685 )   [Full Text(HTML)] () PDF (365KB) ( 826 )   A series of γ-Al2O3 samples modified with borate, phosphate, and sulfate were prepared by the impregnation technique and physically mixed with a methanol synthesis component (CuO-ZnO-Al2O3) at a mass ratio of 1∶2 to form hybrid catalysts. The direct synthesis of dimethyl ether (DME) from syngas was carried out over the prepared hybrid catalysts under pressurized fixed-bed continuous flow conditions. The results indicated that the modification of γ-Al2O3 with SO2-4 could significantly enhance the activity for methanol dehydration and hence remarkably increase the selectivity for DME and the conversion of CO. The effects of SO2-4 content, calcination temperature, and type of SO2-4 precursor on the performance of the SO2-4/γ-Al2O3 hybrid catalyst were further investigated. The results revealed that the selectivity for methanol decreased when the content of SO2-4 increased from 5% to 10%, resulting in the increase in both the selectivity for DME and the conversion of CO. However, when the SO2-4 content was further increased to 15%, although the activity for methanol dehydration was increased continuously, the selectivity for DME decreased slightly due to the increased formation of byproducts hydrocarbons and CO2. Moreover, when the calcination temperature of SO2-4/γ-Al2O3 increased from 350 to 550 ℃, both the CO conversion and the DME selectivity increased gradually, resulting from the decreased formation of CO2. Nevertheless, a further increase in calcination temperature of SO2-4/γ-Al2O3 to 750 ℃ resulted in a significant decline in both DME selectivity and CO conversion because of the decreased activity for methanol dehydration. On the other hand, the type of SO2-4 precursors exerted no noticeable influence on the performance of the prepared hybrid catalysts.

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Preparation of Fe-Al-P-O Catalyst and Its Catalytic Performance for Epoxidation of Propylene SUN Feifei1, ZHONG Shunhe2* 2006, 27 (6):  522-526.  Abstract ( 1835 )   [Full Text(HTML)] () PDF (337KB) ( 919 )   Fe-Al-P-O catalysts were prepared by the sol-gel method and characterized using N2 adsorption, transmission electron microscopy, X-ray diffraction, infrared spectroscopy, and temperature-programmed desorption (TPD). The Fe-Al-P-O catalysts are highly dispersed and homogenous particles with diameter of 20～40 nm. There are Lewis acid sites, Fe3+ and Al3+, and Lewis base sites, terminal oxygen of the P=O double bond, on the surface of the Fe-Al-P-O catalysts. TPD results show that propylene is adsorbed on the Lewis acid sites and the Lewis base sites with C=C double bonds and allylic hydrogen, respectively. H2O can also be adsorbed on Fe3+ and P=O with hydrogen and oxygen atoms. The catalytic performance of Fe-Al-P-O for the epoxidation of propylene was tested in a microreactor. The main selective oxidation product is acrolein with a feed gas composed of C3H6, O2, and N2, whereas the main selective oxidation product is propylene oxide if the feed stream is composed of C3H6, O2, H2, and N2. Under the conditions of atmospheric pressure and 100～300 ℃, the conversion of propylene is 5.9%～9.6% and the selectivity for propylene oxide is over 63%. The epoxidation of propylene to propylene oxide is parallel with the oxidation of propylene to acrolein. The propylene adsorbed on the P=O sites with allylic hydrogen is oxidized into acrolein, whereas the propylene adsorbed on the Lewis acid sites, Fe3+, with C=C double bonds transforms into propylene oxide. Adding H2O to the feed gas can inhibit the formation of acrolein because water decreases the adsorption amount of propylene.

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Synthesis of Chiral Diamine Ligands Derived from Cinchona Alkaloids and Their Catalytic Performance for Asymmetric Transfer Hydrogenation HE Wei, ZHANG Bangle, LIU Peng, SUN Xiaoli, ZHANG Shengyong* 2006, 27 (6):  527-531.  Abstract ( 2163 )   [Full Text(HTML)] () PDF (282KB) ( 1335 )   The asymmetric transfer hydrogenation using 2-propanol as the hydrogen source is a practical and versatile method for obtaining secondary alcohols because of the inexpensive reagents and operational simplicity. Six chiral diamine ligands were synthesized from natural Cinchona alkaloids, quinine and cinchonine, under mild conditions. These were first tested by asymmetric transfer hydrogenation of acetophenone in iridium and rhodium catalytic systems using 2-propanol as the hydrogen source. Both the iridium and rhodium complexes of these ligands showed high activity for this reaction, and the enantioselectivity was influenced deeply by the structure of the chiral ligands. The complexes of 9-amino(9-deoxy)epiquinine and 9-amino(9-deoxy)epicinchonine proved to be effective catalysts, whereas their benzamides and 4-chlorobenzamides provided only moderate ee. The Ir-complex of 9-amino(9-deoxy)epicinchonine was also applied in the hydrogenation of seven aromatic ketone substrates, resulting in a high catalytic activity (80%～90%) and high enantioselectivity (95%～97% ee, except 72% ee for 4-chloroacetophenone). This is the first case using Cinchona alkaloids skeleton in the iridium catalyzed asymmetric reactions.

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Preparation of Au/TiO2 Film and Its Photocatalytic Performance for Oxidation of p-Nitrophenol LIU Xiuhua1*, FU Yibei1, XIE Yun2, DENG Yi1, ZHONG Zhijing1, LIANG Xia1 2006, 27 (6):  532-536.  Abstract ( 1956 )   [Full Text(HTML)] () PDF (396KB) ( 730 )   The Au-doped TiO2 thin film was prepared by the sol-gel method and characterized with atomic force microscopy, X-ray photoelectron spectroscopy, thermogravimetry, differential scanning calorimetry, and X-ray diffraction. The results showed that there were Ti, O, Au, and C elements in the Au/TiO2 film, and the Au existed in a metallic state. The Au/TiO2 film surface became more coarse, the grain size grew gradually, and the photocatalytic activity decreased with the increase in the calcination temperature. Compared with the pure TiO2 film, the photocatalytic activity of Au/TiO2 thin film improved. The Au/TiO2 film calcined at 673 K showed a higher photocatalytic activity, and the degradation rate of p-nitrophenol was 51.4% after 1 h reaction.

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Ethyl Lactate Synthesis by Lipase in Organic Media ZHAO Tiantao1,2, GAO Jing2*, ZHANG Lijie1, QUAN Xuejun1 2006, 27 (6):  537-540.  Abstract ( 1662 )   [Full Text(HTML)] () PDF (218KB) ( 1104 )   Esterification of lactic acid and ethanol by lipase under double substrate inhibition was studied. The best solvent is tert-butyl alcohol and the best lipase is Novozym 435 (immobilized on a macroporous acrylic resin) for this reaction system. The optimization of reaction conditions was studied in detail. When the molar ratio of acid to alcohol is 1∶8, the temperature is 60 ℃, the concentration of acid and lipase is 0.3 mol/L and 45 g/mol, and the revolution is 200 r/min, a yield of 77% was reached. Novozym 435 has a high stability. A yield of 60% for ethyl lactate can be obtained with Novozym 435 even after it was used continuously six times.