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2005, Vol. 14, No. 3　Online: 2005-09-30

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Hydrogen Effect on Coke Removal and Catalytic Performance in Pre-carburization and Methane Dehydro-aromatization Reaction on Mo/HZSM-5 Hongtao Ma;Ryoichi Kojima;Satoshi Kikuchi;Masaru Ichikawa 2005, 14(3): 129-139.  DOI: 摘要 ( 12391 )   PDF(662KB) ( 3995 )   In this study, the effects of pre-carburization of catalyst, hydrogen addition to methane feed and the space velocity of methane on the catalytic performance in methane to benzene (MTB) reaction were discussed in detail over Mo/HZSM-5 catalyst at 1023 K and 0.3 MPa. Compared with the non- pre-carburized catalyst, the Mo catalyst pre-carburized under the flow of CH4+4H2 at 973 K was found to have the higher activity and better stability of the catalyst. Further 6% H2 addition to the methane feed suppressed the aromatic type of coke formation effectively, and improved the stability of catalyst markedly, moreover gave a much longer reaction life of catalyst (53 h at 1023 K and 5400 ml/(g·h)) and much more formation amounts of benzene and hydrogen. With increase of methane space velocity, both the naphthalene formation selectivity and the coke formation selectivity were decreased by the shortened contact time; the benzene formation selectivity and total formation amount before the complete deactiva- tion of catalyst were increased markedly, while the total naphthalene and coke formation amounts did not change much. At high methane space velocity (5400 ml/(g·h)), a new middle temperature coke derived from the high temperature aromatic coke was formed on the catalyst; all the coke formed could be burnt off at lower temperature in oxygen, compared with those obtained at low space velocity. Considering the benzene formation amount and catalyst stability together, 5400 ml/(g·h) was proved to be the most efficient methane space velocity for benzene production.

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Co-generation of C2 Hydrocarbons and Synthesis Gases from Methaneand Carbon Dioxide: Istadi;Nor Aishah Saidina Amin 2005, 14(3): 140-150.  DOI: 摘要 ( 12240 )   PDF(561KB) ( 3319 )   A thermodynamic analysis using the method of direct minimization of Gibbs free energy examines the possibility of all CH4 and CO2 reactions. The effects of CO2/CH4 feed ratio, reaction temperature, and system pressure on equilibrium composition, conversion, selectivity and yield were studied. The reaction temperature above 1100 K and CO2/CH4 ratio = 1 are favourable for synthesis gas production with H2/CO ratio unity via CORM reaction. However, the CO2 OCM reaction to produce ethane and ethylene is less favourable thermodynamically. With the direct Gibbs free energy minimization, the feasibility of all possible CH4 and CO2 reactions could be analyzed theoretically.

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A Study on the Effects of Carrier Gases on the Structure and Morphology of Carbon Nanotubes Prepared by Pyrolysisof Ferrocene and C2H2 Mixture 米万良;Jerry Yuesheng Lin;Qian Mao;Yongdan Li;Baoquan Zhang 2005, 14(3): 151-155.  DOI: 摘要 ( 10410 )   PDF(1327KB) ( 3299 )   Carbon nanotubes (CNTs) were prepared using different carrier gases, with ferrocene as the catalyst precusor and acetylene as the carbon source. The effects of ammonia and nitrogen as carrier gases on the structure and morphology of CNTs were investigated. Transmission electron microscope (TEM), high-resolution electron microscope (HRTEM), scanning electron microscope (SEM) and X-ray diffraction (XRD) were employed to characterize the products and the catalyst. Experiment results show that the CNTs grown in N2 gas exhibited cylindrical and tubular structure, while a bamboo-like structure was observed for the CNTs grown in NH3 gas. Moreover, vertically aligned CNTs were obtained on an Al2O3 disk when NH3 was used as the carrier gas. The carrier gas also exerted influence on the shape of the catalyst. Based on the theory of active centers of catalysis and combined with the particle shape of the catalyst, a growth model for the vertically aligned CNTs on the substrate is given.

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Al2O3 Effect on the Catalytic Activity of Cu-ZnO-Al2O3-SiO2 Catalysts for Dimethyl Ether Synthesis from CO2 Hydrogenation Jiyuan Wang;Chongyu Zeng 2005, 14(3): 156-162.  DOI: 摘要 ( 11231 )   PDF(434KB) ( 3841 )   The effect of Al2O3 on the Cu-ZnO-Al2O3-SiO2 catalysts prepared by a pseudo sol-gel method has been investigated and these catalysts were characterized by XRD, H2-TPR, XPS, NH3-TPD and CO2- TPD techniques. As revealed by XRD and H2-TPR, the added aluminum produces high dispersion of CuO and makes the reduction of CuO difficult. XPS analysis detects a remarkably high Al3+ enrichment at the surface of calcined samples, along with a decrease of Eb of Cu 2p3/2, which confirms the Cu-Al interaction. Another important role of Al2O3 would be to incorporate into the SiO2 structure to form the acid-base sites for ether formation. The reaction results shows that the addition of Al2O3 exhibits a promoting effect on the CO2 conversion only when its content is below 1.4%, and an optimal DME selectivity is obtained when 4.0%Al2O3 is added, indicating a better ‘synergistic effect’ is present between the methanol forming component and the acidic component in bifunctional catalysts. Possible relationship between the catalytic activity and the Cu-Al interaction as well as the surface acidity is discussed.

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Study of Carbon Nanotube Supported Co-Mo Selective Hydrodesulphurization Catalysts for Fluid Catalytic Cracking Gasoline Wenkui Yin;Mei Li;商红岩;刘晨光;魏飞 2005, 14(3): 163-167.  DOI: 摘要 ( 12662 )   PDF(280KB) ( 2494 )   In this paper, carbon nanotube supported Co-Mo catalysts for selective hydrodesulphurization (HDS) of fluid catalytic cracking (FCC) gasoline were studied, using di-isobutylene, cyclohexene, 1-octene and thiophene as model compounds to simulate FCC gasoline. The results show that the Co-Mo/CNT has very high HDS activity and HDS/hydrogenation selectivity comparing with the Co-Mo/ -Al2O3 and Co-Mo/AC catalyst systems. The saturation ratio of cyclohexene was lower than 50%, and the saturation ratio of 1,3-di-isobutylene lower than 60% for the Co-Mo/CNT catalysts. Co/Mo atomic ratio was found to be one of the most important key factors in influencing the hydrogenation selectivity and HDS activity, and the most suitable Co/Mo atomic ratio was 0.4. Co/CNT and Mo/CNT mono-metallic catalysts showed lower HDS activity and selectivity than the Co-Mo/CNT bi-metallic catalysts.

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Preparation and Characterizatioon of Nanotitanium Dioxide Coating Film Doped with Fe3+ Ions on Porous Ceramic 许可敬 2005, 14(3): 168-172.  DOI: 摘要 ( 10496 )   PDF(594KB) ( 2644 )   The nanotitanium dioxide (TiO2) photocatalytic and porous ceramic filtering technique is one of the advanced methods to effectively treat organic wastewater. The TiO2 sol doped with Fe3+ ions was prepared by sol-gel processing. The influences of the process conditions of coating nanophotocatalytic material—Fe3+-TiO2 film on the surface of porous ceramic filter by dipping-lift method on the performance of porous ceramic filter were studied. The porous ceramic filters have two functions at the same time, filtration and photocatalytic degradation. The results of this study showed that the pH and viscosity of the sol, amount of Fe3+ ions doped as well as the coating times greatly affect the quality of coating film, the performance parameters and the photocatalytic activity of the porous ceramic filter. When the pH of the sol is 3–4, the viscosity is about 6 mPa·S, the amount of doped Fe3+ ions is about 2.0 g/L, the porous ceramic filter has been shown to have the best filtering performance and photocatalytic activity. In this condition, the porosity of porous ceramic is about 42.5%, the pore diameter is 8–10 μm. The degradation of methyl-orange is 74.76% under lighting for 120 min.

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Preparation of Carbon Nanotubes from Methane on Ni/Cu/Al Catalyst Renzhong Wei;李凤仪;Yan Ju 2005, 14(3): 173-176.  DOI: 摘要 ( 9369 )   PDF(521KB) ( 3262 )   A series of Ni/Cu/Al catalyst samples were prepared by the co-precipitation method. Carbon nanotubes with large inner diameters are successfully synthesized from methane on Ni/Cu/Al catalyst by adding sodium carbonate. The effects of the copper content and amounts of sodium carbonate on the morphology and microstructures of carbon nanotubes were investigated by CO adsorption and TEM technique. The experimental results showed that copper can influence both the catalytic activity and catalyst life. Best result was obtained when the copper content was 15%. Addition of sodium carbonate favors the formation of carbon nanotubes with large inner diameters. The growth mechanism of carbon nanotubes with large inner diameter is discussed.

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Selective Oxidation of n-Butane over VPO Catalyst Modified by Different Additives 梁红;Daiqi Ye 2005, 14(3): 177-180.  DOI: 摘要 ( 7576 )   PDF(336KB) ( 2592 )   A series of vanadyl pyrophosphate catalyst (VPO) modified by different additives have been prepared with the aim to study the performance for selective conversion of n-butane to maleic anhy- dride(MA). The addition of various promoters improved the catalytic performance remarkably on both activity and selectivity. The correlation of activity and selectivity of the catalysts with their structure has been discussed. The increase in BET surface areas and surface redox sites leads to an enhanced activity. However, good selectivity can only be obtained on those surfaces with suitable surface acid sites.

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Influence of Successive Washing on Porous Structure of Pseudoboehmite Yuefeng Yan;支建平;Gaoyong Zhang 2005, 14(3): 181-188.  DOI: 摘要 ( 6837 )   PDF(714KB) ( 2572 )   The effect of successive washing instead of traditional intermittent washing on the porous structure of pseudoboehmite was investigated by mercury porosimetry, N2 adsorption and thermal analysis, while the stabilities of different types of crystals were investigated by X-ray diffractometer. Experimental results show that successive washing is a continuation of the aging process of intermittent washing. After a successive washing, the pore types showed no difference with the intermittent washing. During successive washing, the characteristics of the pores in the range of 2–15 nm changed only very little. However, the distributions of the pore radius for pores of 20–50 and 300–1000 nm were obviously influenced. It was shown that the volume of larger pores decreased only to a smaller extent after the successive washing, as compared with that of the intermittent washing, and the pore size was affected by the condition of the successive washing. The roles of physisorbed water, intermicellar liquid, weakly bonded water, as well as the role of stirring, have been discussed.