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2005, Vol. 14, No. 1　Online: 2005-03-30

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研究快报

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Plasma Treatment of Ni Catalyst for Partial Oxidation of Methane Yanru Zhu;Zhenhua Li;Yuhong Zhou;Haitao Wang 2005, 14 (1): 1-3.  摘要 ( 10509 )   PDF(1104KB) ( 2039 )   The 10%Ni/Al2O3 catalyst for partial oxidation of methane was treated by DBD (dielectric barrier discharge) plasma in a continuous system under atmospheric pressure and room temperature by flowing He. It was found that 10%Ni/Al2O3 catalyst treated by plasma presents a higher catalytic activity and an enhanced stability than the catalysts prepared without plasma treatment. The methane conversion over the catalyst treated by plasma is 3%-5% higher than the catalysts untreated by plasma. Moreover, the enhanced dispersion of the catalyst can be achieved by plasma treatment, which can improve the interaction between active species and supports, catalytic activity and the resistance to carbon deposition.

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Influence of Pretreatment on the Interaction of Oxygen with Silver and the Catalytic Activity of Ag/SiO2 Catalysts for CO Selective Oxidation in H2 Zhenping Qu;Mojie Cheng;Chuan Shi;Xinhe Bao 2005, 14 (1): 4-12.  摘要 ( 9590 )   PDF(1750KB) ( 2208 )   The interactions of oxygen with pre-reduced silver catalysts as well as their catalytic properties for CO selective oxidation in H2 after oxygen pre-treatment are studied in this paper. It is found that the pretreatment exerts a strong influence on the activity and selectivity of the silver catalyst. A drop in activity and selectivity is observed after treating a pre-reduced catalyst with oxygen at low temperatures, whereas a converse result is obtained after an oxidizing treatment at high temperatures (T≥350oC). O2- TPD results show that surface oxygen species adsorbs on silver surface after the oxygen treatment at low temperatures. However, penetration of oxygen into the silver is enhanced by a high temperature treatment, meanwhile the surface oxygen species disappear. No other silver species except metallic silver are observed on all the catalysts by XRD, and the size of silver particle is not changed after the treatment with oxygen at low temperatures. The surface oxygen species formed by oxygen treatment can also be removed by hydrogen reduction. The strongly-adsorbed surface oxygen species prohibit the adsorption and diffusion of oxygen species in reaction gas on the surface of silver catalyst, causing the decrease in CO oxidation activity, in other words, it is important to obtain a clean silver surface for increasing the catalyst activity in CO removal from H2-rich feed gas. The differences in activity and selectivity due to the oxygen pretreatment at different temperatures are discussed in terms of the changes in the surface/subsurface oxygen species of the silver particles.

Articles

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Kinetic Modeling of Plasma Methane Conversion Using Gliding Arc Antonius Indarto;Jae-Wook Choi;Hwaung Lee;Hyung Keun Song 2005, 14 (1): 13-21.  摘要 ( 11270 )   PDF(3518KB) ( 1662 )   Plasma methane (CH4) conversion in gliding arc discharge was examined. The result data of experiments regarding the performance of gliding arc discharge were presented in this paper. A simulation which is consisted some chemical kinetic mechanisms has been provided to analyze and describe the plasma process. The effect of total gas flow rate and input frequency refers to power consumption have been studied to evaluate the performance of gliding arc plasma system and the reaction mechanism of decomposition. Experiment results indicated that the maximum conversion of CH4 reached 50% at the total gas flow rate of 1 L/min. The plasma reaction was occurred at the atmospheric pressure and the main products were C (solid), hydrogen, and acetylene (C2H2). The plasma reaction of methane conversion was exothermic reaction which increased the product stream temperature around 30{50 .

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Intrinsic Kinetics of Dimethyl Ether Synthesis from Syngas Zhaoguang Nie;Hongwei Liu;Dianhua Liu;Weiyong Ying;Dingye Fang 2005, 14 (1): 22-28.  摘要 ( 12941 )   PDF(334KB) ( 4842 )   The intrinsic kinetics of dimethyl ether (DME) synthesis from syngas over a methanol synthesis catalyst mixed with methanol dehydration catalyst has been investigated in a tubular integral reactor at 3-7 MPa and 220-260oC. The three reactions including methanol synthesis from CO and H2, CO2 and H2, and methanol dehydration were chosen as the independent reactions. The L-H kinetic model was presented for dimethyl ether synthesis and the parameters of the model were obtained by using simplex method combined with genetic algorithm. The model is reliable according to statistical analysis and residual error analysis. The synergy effect of the reactions over the bifunctional catalyst was compared with the effect for methanol synthesis catalyst under the same conditions based on the model. The effects of syngas containing N2 on the reactions were also simulated.

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CO Selective Oxidation in Hydrogen-Rich Gas over Copper-Series Catalysts Hanbo Zou;Xinfa Dong;Weiming Lin 2005, 14 (1): 29-34.  摘要 ( 8766 )   PDF(876KB) ( 2400 )   The performances of CO selective oxidation in hydrogen-rich gas over four catalytic systems of CuO/ZrO2, CuO/MnO2, CuO/CoO and CuO/CeO2 were compared. The reducibility of these catalysts and the effect of CuO and CeO2 molar ratio of CuO/CeO2 catalysts on the activity of selective CO oxidation are investigated by XRD and TPR methods. The results show that the catalysts with the exception of CuO/ZrO2 have the interactions between CuO and CoO, CeO2 or MnO2, which result in a decrease in the reduction temperature. Among the catalysts studied, CuO/ZrO2 catalyst shows the lowest catalytic activity while CuO/CeO2 catalyst exhibits the best catalytic performance. The CuO(10%)/CeO2 catalyst attains the highest CO conversion and selectivity at 140 and 160oC. The addition of 9% H2O in the reactant feed decreases the activity of CuO/CeO2 catalyst but increases its CO selectivity.

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Synthesis and Characterization of Self-Assembled V2O5 Mesostructures Intercalated by Polyaniline Li Li;Zifeng Yan 2005, 14 (1): 35-39.  摘要 ( 8304 )   PDF(640KB) ( 2622 )   A new nanocomposite of vanadium pentoxide (V2O5) and polyaniline (PANI) were synthesized by in situ oxidative polymerization/intercalation on V2O5 powder at room temperature. The reaction was facile and topotactic, forming polyaniline as the emeraldine salt. It was indicated that V2O5 itself can catalyze the oxidative polymerization of aniline and that layered structure could make aniline intercalate into the V2O5 framework. It makes the in situ polymerization feasible to occur in the layer of V2O5 structure. XRD results showed PANI/V2O5 nanocomposite possessed lamellar mesostructure, which was determined by an X-ray diffraction peak at 6.5o and SEM photograph. And FT-IR spectrum suggested that there was interaction between PANI and V2O5. The hybrid had better thermal stability in N2 and air ambience.

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Study on the Synthesis of Phenylacetic Acid by Carbonylation of Benzyl Chloride under Normal Pressure Zumin Qiu;Yunbing He;Dianmo Zheng;Fufang Liu 2005, 14 (1): 40-46.  摘要 ( 10266 )   PDF(462KB) ( 2436 )   The influences of some factors on the yield of phenylacetic acid in the carbonylation of benzyl chloride were studied in this paper. These factors included the variety and content of catalyst, and that of solvent, way of material feeding, reaction temperature, sodium hydrate concentration, triphenylphosphine content, presence of surfactant, the ratio of organic phase volume to aqueous phase volume etc. The optimum reaction conditions were found to be: with a one-time pour of 0.15 g Pd(PPh3)2Cl2, 0.24 g PPh3, 75 ml NaOH of 3.5 mol/L, 20 ml benzyl chloride and 55 ml n-butyl alcohol, and the reaction was carried out at 50 for about 3 hours. The as-obtained yield of phenylacetic acid was as high as 97.6%. In addition, the influences of the presence of phenylacetic acid and air in the reaction system were also studied. The results showed that the presence of air in the system and the entrainment of phenylacetic acid in the circulating organic phase had great influence on the reaction rate, the stability and performance of catalyst and the yield of phenylacetic acid.

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Synthesis of Dimethyl Ether from CO Hydrogenation: a Thermodynamic Analysis of the Influence of Water Gas Shift Reaction Guangxin Jia;Yisheng Tan;Yizhuo Han 2005, 14 (1): 47-53.  摘要 ( 9363 )   PDF(426KB) ( 2834 )   Three reactions involved in dimethyl ether (DME) synthesis from CO hydrogenation: methanol synthesis reaction (MSR), methanol dehydration reaction (MDR) and water gas shift reaction (WGSR) are studied by thermodynamic calculation. For demonstrating this process in detail, three models, MSR, MSR+MDR, MSR+MDR+WGSR, are used. Their basic characteristics can be obtained by varying widely the ratios of H2 to CO in the feed (no CO2). Through thermodynamic analysis a chemical synergic effect obviously exists in the second and third models. By comparison between two models it is found that WGSR plays a special role in dimethyl ether synthesis. It is possible for the two models to shift one to the other by regulating CO2 concentration in feed. For Model 2, the selectivity for DME in oxygenates (DME+methanol) does not change with the ratio of H2 to CO.

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Selective Oxidation of Isobutane over NH4CsFePVMoAs Heteropolycompound Catalysts Tiejun Cai;Zhengjun Fang;Qian Deng;Zhenshan Peng 2005, 14 (1): 54-60.  摘要 ( 9310 )   PDF(913KB) ( 2252 )   A series of NH4Cs1:5Fe0:08HxPVMo11AsaOy heteropolycompound catalysts for the selective oxidation of isobutane, having Keggin structure, were synthesized by using co-precipitation method. The catalysts were characterized by FT-IR, H2-TPR, TG-DTA, SEM and XRD. Effects of the As content, reaction time, reaction temperature and molar ratio of isobutane to oxygen in feedstock on the activity and selectivity of the catalyst were investigated. The activation energy of the catalysts was measured by kinetics researches. Results showed the introduction of Cs+ into the catalysts shortened the stable period of them and enhanced their catalytic activity for the selective oxidation of isobutane. The highest conversion of isobutane and the total selectivity to liquid products were 18.6% and 81.2%, respectively, which were obtained at 380oC with a space velocity of 975 h over the NH4Cs1:5Fe0:08HxPVMo11As0:3Oy heteropolycompound catalyst. It is confirmed that completely oxidized products were controlled well.