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2002, Vol. 11, No. 3　Online: 2002-09-30

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Recent Technological Developments in Cobalt Catalysts for Fischer-Tropsch Synthesis Junling Zhang;Jiangang Chen;Yongwang Li;Yuhan Sun 2002, 11 (3): 99-108.  摘要 ( 8833 )   PDF(287KB) ( 2576 )   Co-based catalysts are often utilized due to their high Fischer-Tropsch synthesis (FT) activity, C+ 5 hydrocarbon selectivity, low water-gas shift reaction (WGS) activity and relatively low cost. Selec- tive control of C+ 5 hydrocarbons and the catalyst longevity are critical in the design of cobalt catalysts. Thus, various methods to improve the performance of Co catalysts have been suggested. The progress in cobalt catalysts reviewed in the last few decades, mainly involved the support, promoter, preparation and deactivation of Co-based catalysts.

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New Advances in Catalytic Systems for Conversion of CH4 and CO2 Gengliang Chen 2002, 11 (3): 109-116.  摘要 ( 9865 )   PDF(353KB) ( 2314 )   One of the main goals for developing the C1 chemical industry is the direct conversion of methane and carbon dioxide to useful products. To realize this goal, researches on new catalytic systems are being globally focused. The exploration has been evolved from traditional heterogeneous catalysis into homogeneous catalysis. Coordinate complexes, biochemical and bionics, and photo- and electrochemical catalysis have been extensively studied in recent years. Tests in laboratories have veried for the direct conversion of CH4 to CH3OH that single-pass converstion of CH4 can reach over 70% in both Hg(II) salt and Pt(II) complex systems. The main problem of these systems is the obstacles involving reaction kinetics, so they must be solved before moving to pilot tests. Other catalytic systems discussed in the present article include explorations in the early stage. Among them, features of photo and enzymatic catalyst systems, such as mild reaction conditions, better selectivity and environmentally friendliness have been explored, and these researches are signicant both in theory and in practical application.

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Stereoselective Synthesis of (Z)-α-Alkylidene-γ-Butyrolactones via Pd-Catalyzed CO Lijun Liu;Fentair Luo 2002, 11 (3): 117-119.  摘要 ( 7197 )   PDF(217KB) ( 2068 )   Four new (Z)-2-phenoxymethylene-4-pentanolide derivatives and four (Z)-2-phenoxymethyl-2- penten-r-lactone derivatives were prepared via Pd-catalyzed carbon monoxide insertion and intramolecular cyclization. All compounds were characterized by IR, 1H NMR, 13C NMR, MS spectra and elemental analysis. The plausible mechanism of the reaction was discussed.

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Selective Oxidation of Isobutane to Methacrylic Acid over Supported V-Mo-P Based Feifei Sun;Yunfeng Geng;Shunhe Zhong 2002, 11 (3): 120-126.  摘要 ( 9035 )   PDF(264KB) ( 2033 )   Heteropolyacid, the most popular catalyst for the direct oxidation of isobutane, exhibits high catalytic activity, poor thermal stability and a short lifetime. Therefore, the catalyst requires further research to improve its performance. Catalysts composed of mixed oxides (V2O5, P2O5, or MoO3) sup- ported on silica were prepared by the sol-gel method to catalyze the reaction. Results of XRD, IR, and BET corroborated that the mixed oxides were dispersed homogeneously on the surface of support. The activity of lattice oxygen in the catalysts was studied by TPR, and the chemisorption property of isobutane on the surface of the catalysts was investigated by the TPD method. H2-TPR of the catalysts revealed that the lattice oxygen of the vanadium-based catalysts is more active than that of the molybdenum-based catalysts. The redox property of V or Mo species is slightly aected by other compositions of the series catalysts. The TPD curves illustrate that there are two kinds of adsorptive species of isobutane on the surface of the V and Mo based catalysts. The adsorbing species on the VMoP/SiO2 catalyst are identical to the main adsorbing species on VP/SiO2 and MoP/SiO2. The catalyst VMoP/SiO2 is more active than others in the selective oxidation of isobutane.

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Preparation of AgBiVMoO/-Al2O3 Catalysts for the Partial Oxidation of Propane Hongbo Li;Jianhua Tong;Hongjuan Zhu;Baichun Zhu;Ping Yang;Weishen Yang 2002, 11 (3): 127-130.  摘要 ( 8634 )   PDF(270KB) ( 1769 )   A novel mixed sol method was developed for the preparation of supported catalysts. Analyses by means of XRD and BET show that a 40%AgBiVMoO/ r-Al2O3 catalyst prepared by this method possessed high specific surface area and high dispersion of the active phase. As a result, high acrylic acid selectivity of 8.5% was obtained when the catalyst was used in the reaction of propane partial oxidation to acrylic acid in a fixed-bed reactor.

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Oxidative Coupling of Methane over Na-W-Mn/SiO2 Catalysts at Elevated Pressures Lingjun Chou;Yingchun Cai;Bing Zhang;Jianzhong Niu;Shengfu Ji;Shuben Li 2002, 11 (3): 131-136.  摘要 ( 8539 )   PDF(331KB) ( 2147 )   Na-Mn-W/SiO2 catalysts were studied for the oxidative coupling of methane (OCM) in a micro fixed bed reactor made of stainless steel reactor at elevated pressures. The eect of operating conditions, such as GHSV, pressure, temperature and CH4/O2 ratio on the catalytic performance of OCM was investigated. The C2+ selectivity of 80.3% was obtained at a CH4 conversion of 16.1% at 750oC, 1.5.105h-1 GHSV, and 0.6 MPa. Also, there is a small output of C3 and C4 hydrocarbons in the tail gas. The results show that unfavorable eects due to elevated pressure can be overcome by increasing GHSV, and the OCM reaction is strongly dependent on the operating conditions at elevated pressures, particularly GHSV and the CH4/O2 ratio.

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Partial Oxidation of Methane to Syngas Using Lattice Oxygen of La1-xSrxFeO3 Ranjia Li;Changchun Yu;Shikong Shen 2002, 11 (3): 137-144.  摘要 ( 8697 )   PDF(411KB) ( 2985 )   Catalytic partial oxidation of methane to syngas using the lattice oxygen of La1-xSrxFeO3 samples have a single-phase perovskite-type oxide. The redox properties of the catalysts were investigated by temperature programmed reduction with hydrogen (H2-TPR). Reducibility of the catalysts increase with the increasing of the Sr2+ content. The oxygen species of the catalysts and their reaction with CH4 were studied by the temperature programmed surface reaction (CH4-TPSR). In the absence of gas phase oxygen, there exist two kinds of oxygen species on the catalysts. One kind of the oxygen species with strong oxidative ability is produced first, which can oxidize CH4 completely to CO2 and H2O. Then, the second oxygen species with weak oxidative ability is formed, which can oxidize CH4 partially to CO and H2 with high selectivity. The number of the oxygen species with strong oxidative ability in the CH4-TPSR tends to become zero at low x values (x<0.1). 4-TPSR tends to become zero at low x values (x<0.1). Under suitable reaction conditions, switching alternatively the reactions of 11% O2-Ar and 11% CH4-He over a La0:8Sr0:2FeO3 catalyst at 900oC allows methane to be selectively converted to synthesis gas (CH4 conversion ~90%, CO selectivity >93%) using the lattice oxygen of the perovskite oxide catalyst in a redox mode.

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Chemical Reactions and Kinetics of the Carbon Monoxide Coupling in the Presence of Fandong Meng;Genhui Xu;Zhenhua Li;Pa Du 2002, 11 (3): 145-150.  摘要 ( 8172 )   PDF(268KB) ( 2039 )   The chemical reactions and kinetics of the catalytic coupling reaction of carbon monoxide to diethyl oxalate were studied in the presence of hydrogen over a supported palladium catalyst in the gaseous phase at the typical coupling reaction conditions. The experiments were performed in a continuous flow fixed-bed reactor. The results indicated that hydrogen only reacts with ethyl nitrite to form ethanol, and kinetic studies revealed that the rate-determining step is the surface reaction of adsorbed hydrogen and the ethoxy radical (EtO-). A kinetic model is proposed and a comparison of the observed and calculated conversions showed that the rate expressions are of rather high confidence.

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Studies on the Adsorption and Dissociation of Methane and Carbon Dioxide on Nickel Ling Qian;Zifeng Yan 2002, 11 (3): 151-158.  摘要 ( 8978 )   PDF(389KB) ( 1946 )   The adsorption and dissociation of methane and carbon dioxide for reforming on nickel catalysts were extensively investigated by TPSR, TPD, XPS and pulse reaction methods. These studies showed that the decomposition of methane results in the formation of at least three kinds of surface carbon species on supported nickel catalysts. Carbidic Ca, carbonaceous Cb and carbidic clusters Cr surface carbon species formed by the decomposition of methane demonstrated dierent surface mobility, thermal stability and reactivity. Carbidic Ca is a very active and important intermediate in carbon dioxide reforming with methane, and the carbidic clusters Cr species might be the precursor of surface carbon deposition. The partially dehydrogenated Cb species can react with H2 or CO2 to form CH4 or CO. On the other hand, it was proven that CO2 can be weakly adsorbed on supported nickel catalysts, and only one kind of CO2 adsorption state is formed. The interaction mechanism between the species dissociated from CH4 and CO2 during reforming was then hypothesized.

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Studies on the Performance and Structure of　Supported Catalysts for the Partial TinghuaWu;Mingqiao Zhu;Zhenjiang Niu;Yijun Zhong;Yan Guan;Ya Liu;Qiangu Yan;Zelin Li;Huilin Wan 2002, 11 (3): 159-164.  摘要 ( 7626 )   PDF(303KB) ( 2067 )   The catalytic properties of several supported metal catalysts on dierent carriers were studied in the partial oxidation of methane (POM) to syngas. In our experiment, supported noble metal catalysts exhibited better performance than the other supported transition metal catalysts. The catalyst perfor- mances were significantly in uenced by the d-electron configuration of the active metal components and the dispersion of active metal components on the support. A catalyst with a moderate number of unpaired electrons in the d-orbital of the active metal support without obvious acidity or redox activity (e.g. MgO) was suitable for POM performance. The Rh/SiO2 catalyst was the best in the POM reaction, among those investigated. Reaction conditions apparently also aected the POM performance of the catalyst. The conversion of methane and the selectivity for CO increased with the reaction temperature, and a high CH4/O2 ratio was not beneficial for POM performance.

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Deactivation Mechanism for COS Hydrolysis　over TGH Catalyst --- FT-IR Study of the Meisheng Liang;Chunhu Li;Hanxian Guo;Kechang Xie 2002, 11(3): 165-170.  DOI: 摘要 ( 9473 )   PDF(347KB) ( 2099 )   Abstract: The adsorptions of COS, H2S and O2 were investigated over the TGH catalyst in this paper. It was found that the numbers of basic centers and basic intensities were reduced over the deactivated TGH catalyst. The FT-IR results of COS+H2S+O2 co-adsorption on the TGH catalyst show that the main causes of catalyst deactivation is the formation of element sulfur and trace sulfate.

研究快报

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Preparation of Zeolite X Membranes on Porous Ceramic Substrates with Zeolite Seeds Zhongqiang Xu;Qingling Chen;Guanzhong Lu 2002, 11 (3): 171-179.  摘要 ( 8987 )   PDF(2432KB) ( 1525 )   Zeolite X membranes were investigated by in-situ hydrothermal synthesis on porous ceramic tubes precoated with zeolite X seeds or precursor amorphous aluminosilicate, and porous a-Al2O3 ceramic tubes with a pore size of 50-200 nm were employed as supports. Zeolite X crystals were synthesized by the classic method and mixed into deionized water as a slurry with a concentration of 0.2-0.5wt%, having a range of crystal sizes from 0.2 to 2 um. Crystal seeds were pressed into the pores near the inner surface of the ceramic tubes, and crystallization took place at 95oC for 24-96 h. It was also investigated that Boehmite sol added with zeolite X seeds was precoated on ceramic supports to form a layer of r-Al2O3 by heating, and hydrothermal crystallization could then take place to prepare the zeolite membranes on the composite ceramic tubes. The crystal species were characterized by XRD, and the morphology of the supports subjected to crystallization was characterized by SEM. The composite zeolite membranes have zeolitic top-layers with a thickness of 10-25 um, and zeolite crystals can be intruded into pores of the supports as deeply as 100 um. The experimental results indicate that the precoating of zeolitic seeds on supports is beneficial to crystallization by shortening the synthesis time and improving the membrane strength. The resulting zeolite X membrane shows permselectivity to tri-n-butylamine((C4H9)3N) over per uro-tributyl-amine ((C4F9)3N), and a permeance ratio of 57 for ((C4H9)3N to (C4F9)3N could be reached at 350oC Permeances of BZ, EB and TIPB through the zeolite membrane were also measured and were found to slightly increase with temperature.

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Liquid-Phase Selective Oxidation of Propane on Silica-Supported Nafion Catalysts Francesco Frusteri;Lorenzo Spadaro;Claudia Espro;Adolfo Parmaliana;Francesco 2002, 11 (3): 180-185.  摘要 ( 8061 )   PDF(263KB) ( 1883 )   The liquid-phase partial oxidation of propane in the presence of the Fen+/H2O2 Fenton system at 70oC and 1.4 atm on silica supported Nafion catalysts has been investigated. The reaction proceeds via a radical reaction path the efficiency of which is improved by silica-supported Nafion catalysts. Because of the direct relationship between reaction rate and concentration of sulphonic acid sites of Nafion catalysts, it is inferred that the active phase enahnces the kinetics of propane conversion by promoting the rate of active radicals generation.