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2008, Vol. 17, No. 1　Online: 2008-03-30

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Methane oxidative carbonylation catalyzed by rhodium chalcogen halides over carbon supports G. R. Kosmambetova*;P. E. Strizhak;V. I. Gritsenko*;S. V. Volkov;L. B. Kharkova;O. G.Yanko;O. M. Korduban 2008, 17(1): 1-7.  DOI: 摘要 ( 10508 )   PDF   Gas phase carbonylation of methane is studied in the presence of molecular oxygen over pure carbon carriers and carbon supported rhodium chalcogen halides. Activated carbons and fullerene blacks have been used as carbon supports. XPS and IR-spectroscopy data show the formation of rhodium chalcogen halides in solids prepared by different methods. We have found that the productivity of acetic acid by carbon supported rhodium chalcogen halides depends strongly on the carbon carrier and the method of the catalyst preparation. Namely, the catalyst with highest productivity for the acetic acid is prepared by synthesizing the rhodium chalcogen halide over the carbon support followed by thermal destruction. We have also found that rhodium chalcogen halides over activated carbons are more active compared with fullerene supported catalysts.

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Oxidative coupling of methane in a fixed bed reactor over perovskite catalyst: A simulation study using experimental kinetic model Nakisa Yaghobi;Mir Hamid Reza Ghoreishy* 2008, 17(1): 8-16.  DOI: 摘要 ( 10894 )   PDF   The oxidative coupling of methane (OCM) to ethylene over a perovskite titanate catalyst in a fixed bed reactor was studied experimentally and numerically. The two-dimensional steady state model accounted for separate energy equations for the gas and solid phases coupled with an experimental kinetic model. A lumped kinetic model containing four main species CH4, O2, COx (CO2, CO), and C2 (C2H4 and C2H6) was used with a plug flow reactor model as well. The results from the model agreed with the experimental data. The model was used to analyze the influence of temperature and feed gas composition on the conversion and selectivity of the reactor performance. The analytical results indicate that the conversion decreases, whereas, C2 selectivity increases by increasing gas hourly space velocity (GHSV) and the methane conversion also decreases by increasing the methane to oxygen ratio.

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Characterization and catalytic performance of CeO2-Co/SiO2 catalyst for Fischer-Tropsch synthesis using nitrogen-diluted synthesis gas over a laboratory scale fixed-bed reactor Xiaoping Dai;Changchun Yu* 2008, 17(1): 17-23.  DOI: 摘要 ( 11179 )   PDF   The surface species of CO hydrogenation on CeO2-Co/SiO2 catalyst were investigated using the techniques of temperature programmed reaction and transient response method. The results indicated that the formation of H2O and CO2 was the competitive reaction for the surface oxygen species, CH4 was producedviathe hydrogenation of carbon species step by step, and C2 products were formed by the polymerization of surface-active carbon species (--CH2--). Hydrogen assisted the dissociation of CO. The hydrogenation of surface carbon species was the rate-limiting step in the hydrogenation of CO over CeO2-Co/SiO2 catalyst. The investigation of total pressure, gas hourly space velocity (GHSV), and product distribution using nitrogen-rich synthesis gas as feedstock over a laboratory scale fixed-bed reactor indicated that total pressure and GHSV had a significant effect on the catalytic performance of CeO2-Co/SiO2 catalyst. The removal of heat and control of the reaction temperature were extremely critical steps, which required lower GHSV and appropriate CO conversion to avoid the deactivation of the catalyst. The feedstock of nitrogen-rich synthesis gas was favorable to increase the conversion of CO, but there was a shift of product distribution toward the light hydrocarbon. The nitrogen-rich synthesis gas was feasible for F-T synthesis for the utilization of remote natural gas.

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Direct partial oxidation of methane to methanol: Reaction zones and role of catalyst location Qijian Zhang*;Dehua He;Qiming Zhu 2008, 17(1): 24-28.  DOI: 摘要 ( 10639 )   PDF   Direct partial oxidation of methane to methanol was investigated in a specially designed reactor. Methanol yield of about 7%-8% was obtained in gas phase partial oxidation. It was proposed that the reactor could be divided into three reaction zones, namely pre-reaction zone, fierce reaction zone, and post-reaction zone, when the temperature was high enough to initiate a reaction. The oxidation of methane proceeded and was completed mostly in the fierce reaction zone. When the reactant mixture entered the post-reaction zone, only a small amount of produced methanol would bring about secondary reactions, because molecular oxygen had been exhausted in the fierce reaction zone. A catalyst, if necessary, should be placed either in the pre-reaction zone, to initiate a partial oxidation reaction at a lower temperature, or in the fierce reaction zone to control the homogeneous free radical reaction.

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Sorption of methane and CO2 for enhanced coalbed methane recovery and carbon dioxide sequestration Basanta Kumar Prusty* 2008, 17(1): 29-38.  DOI: 摘要 ( 10506 )   PDF   Sequestration of CO2 in deep and unmineable coal seams is one of the attractive alternatives to reduce its atmospheric concentration. Injection of CO2 in coal seams may help in enhancing the recovery of coalbed methane. An experimental study has been carried out using coal samples from three different coal seams, to evaluate the enhanced gas recovery and sequestration potential of these coals. The coals were first saturated with methane and then by depressurization some of the adsorbed methane was desorbed. After partial desorption, CO2 was injected into the coals and subsequently they were depressurized again. Desorption of methane after the injections was studied, to investigate the ability of CO2 to displace and enhance the recovery of methane from the coals. The coals exhibited varying behavior of adsorption of CO2 and release of methane. For one coal, the release of methane was enhanced by injection of CO2, suggesting preferential adsorption of CO2 and desorption of methane. For the other two coals, CO2 injection did not produce incremental methane initially, as there was initial resistance to methane release. However with continued CO2 injection, most of the remaining methane was produced. The study suggested that preferential sorption behavior of coal and enhanced gas recovery pattern could not be generalized for all coals.

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Optimization of methane conversion to liquid fuels over W-Cu/ZSM-5 catalysts by response surface methodology Didi Dwi Anggoro*;Istadi 2008, 17(1): 39-44.  DOI: 摘要 ( 9727 )   PDF   The conversion of methane to liquid fuels is still in the development process. The modified HZSM-5 by loading with Tungsten (W) enhanced its heat resistant performance, and the high reaction temperature (800 0C) did not lead to the loss of W component by sublimation. The loading of HZSM-5 with Tungsten and Copper (Cu) resulted in an increment in the methane conversion, CO2, and C5+ selectivities. The high methane conversion and C5+ selectivity, and low H2O selectivity are obtained by using W/3.0Cu/HZSM. The optimization of methane conversion over 3.0W/3.0Cu/ZSM-5 under different temperature and oxygen concentration using Response Surface Methodology (RSM) are studied. The optimum point for methane conversion is 19% when temperature is 753 0C, and oxygen concentration is 12%. The highest C5+ selectivity is 27% when temperature is 751 0C, and oxygen concentration is 11%.

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Acidity effects of H zeolite on olefin alkylation of thiophenic sulfur in gasoline Zekai Zhang;Dong Liu;Xiangxue Zhu;Haiwei Yu;;Shenglin Liu;Longya Xu* 2008, 17(1): 45-50.  DOI: 摘要 ( 9610 )   PDF   Olefin alkylation of thiophenic sulfur process was carried out in model gasoline, using Hβ zeolites with different Si/Al2 ratios as catalysts. In particular, the influence of acid properties of Hβ zeolites on its catalytic ability for the thiophene alkylation, xylene alkylation and hexene oligomerization was investigated. The results showed that the acidity of the Hβ zeolite was increased with the decrease of Si/Al2 ratio, but its catalytic ability was not always increased. In fact, it reached the maximal catalytic ability at Si/Al2 ratio of 66, and under the reaction conditions of 60 ℃, 1.5 MPa, WHSV 3.0 h-1 and time on stream 2 h. At the ratio, the conversion of thiophene, xylene, and oligomerized hexene were 96.6%, 2.7% and 2.8%, respectively. An optimal Si/Al2 ratio exists for the catalytic performance of Hβ zeolite. By investigating the coke deposition of the used Hβ zeolite catalysts, it has been found that the optimal Si/Al2 ratio is attributed to the combined effect of the carbocation activation capability and the hydrogen transformation capability of the Hβ zeolite catalyst.

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Analyzing solubility of acid gas and light alkanes in triethylene glycol Alireza Bahadori*;Hari B. Vuthaluru;Saeid Mokhatab 2008, 17(1): 51-58.  DOI: 摘要 ( 10223 )   PDF   Physical solvents such as ethylene glycol (EG), diethylene glycol (DEG), and triethylene glycol (TEG) are commonly used in wet gas dehydration processes with TEG being the most popular due to ease of regeneration and low solvent losses. Unfortunately, TEG absorbs significantly more hydrocarbons and acid gases than EG or DEG. Quantifying this amount of absorption is therefore critical in order to minimize hydrocarbon losses or to optimize hydrocarbon recovery depending on the objective of the process. In this article, a new correlation that fully covers the operating ranges of TEG dehydration units is developed in order to determine the solubility of light alkanes and acid gases in TEG solvent. The influence of several parameters on hydrocarbon and acid gas solubility including temperature, pressure, and solvent content is also examined.

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Scale up and stability test for oxidative coupling of methane over Na2WO4-Mn/SiO2 catalyst in a 200 ml fixed-bed reactor Haitao Liu;Xiaolai Wang*;Dexin Yang;Runxiong Gao;Zhonglai Wang;Jian Yang 2008, 17(1): 59-63.  DOI: 摘要 ( 10801 )   PDF   The study of scale up for the oxidative coupling of methane (OCM) has been carried out in a 200 ml stainless steel fixed-bed reactor over a 5wt% Na2WO4-1.9wt% Mn/SiO2 (W-Mn/SiO2) catalyst. The effects of reaction conditions were investigated in detail. The results showed that, with increasing reaction temperature, the gas-phase reaction was enhanced and a significant amount of methane was converted into COx; with the CH4/O2 molar ratio of 5, the highest C2 (ethylene and ethane) yield of 25% was achieved; the presence of steam (as diluent) had a positive effect on the C2 selectivity and yield. Under lower methane gaseous hourly space velocity (GHSV), higher selectivity and yield of C2 were obtained as the result of the decrease of released heat energy. In 100 h reaction time, the C2 selectivity of 66%-61% and C2 yield of 24.2%-25.4% were achieved by a single pass without any significant loss in catalytic performance.

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Intrinsic kinetics of methane aromatization under non-oxidative conditions over modified Mo/HZSM-5 catalysts Benzhen Yao;Jin Chen;Dianhua Liu;Dingye Fang* 2008, 17(1): 64-68.  DOI: 摘要 ( 11538 )   PDF   The intrinsic reaction kinetics of methane aromatization under non-oxidative conditions over modified Mo/HZSM-5 catalysts was studied in the quartz pipe-reactor under ordinary pressure with the temperature ranging from 913.15 to 973.15 K and the space velocity from 700 to 2100 ml/(g·h). The Langmuir-Hinshelwood model was chosen to describe the intrinsic kinetics while Levenberg-Marquardt method was selected to determine the parameters in the kinetic model. Statistical test and residual error distribution diagrams showed that experimental data were in good agreement with calculated data, and Langmuir-Hinshelwood model was suitable for the description of the intrinsic kinetics of methane aromatization under the reaction conditions discussed in this article.

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Thermal and hydrothermal stabilities of the alkali-treated HZSM-5 zeolites Yuning Li;Dong Liu;Shenglin Liu;Wei Wang;Sujuan Xie;Xiangxue Zhu;Longya Xu* 2008, 17(1): 69-74.  DOI: 摘要 ( 10018 )   PDF   HZSM-5 zeolites with the micro-mesopore hierarchical porosity have been prepared by the post-synthesis of alkali-treatment, and their thermal and hydrothermal stabilities were studied using DTA, XRD, and NH3-TPD characterization techniques. Compared to the unmodified zeolite, the thermal and hydrothermal stabilities of the alkali-treated ZSM-5 zeolites were slightly deteriorated because of the introduction of mesopores caused by the desilication. Nevertheless, the alkali-treated zeolite framework could be maintained until the temperature increased to 1175 0C.

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Partial oxidation of dimethyl ether to H2/syngas over supported Pt catalyst Yazhong Chen;Zongping Shao*;Nanping Xu 2008, 17(1): 75-80.  DOI: 摘要 ( 13316 )   PDF   Dimethyl ether (DME) is a non-toxic fuel with high H/C ratio and high volumetric energy density, and could be served as an ideal source of H2/syngas production for application in solid oxide fuel cells (SOFC). This study presents results of DME partial oxidation over a 1.5 wt% Pt/Ce0.4Zr0.6O2 catalyst under the condition of gas hourly space velocity (GHSV) of 15000-60000\: ml/(g·h), molar ratio of O2/DME of 0.5 and 500-700 0C, and this temperature range was also the operation temperature range for intermediate temperature SOFC. The results indicated that the catalyst showed good activity for the selective partial oxidation of DME to H2/syngas. Under the working conditions investigated, DME was completely converted. Increase in reaction temperature enhanced the amount of syngas, but lowered the H2/CO ratio and yield of methane; while increase in reaction GHSV resulted in only slight variation in the distribution of products. The good catalytic activity of Pt supported on Ce0.4Zr0.6O2 for the partial oxidation of DME may be directly associated with the good oxygen storage capacity of the support, which is worth of further investigation to develop materials for application in SOFC.

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Comparative study on the reaction of methane over a ZnO bed in the absence and presence of CO2 Xianquan Ao;Hua Wang*;Yonggang Wei 2008, 17(1): 81-86.  DOI: 摘要 ( 11515 )   PDF   The reaction of zinc oxide with methane in the absence and presence of CO2 were theoretically and experimentally investigated using HSC Chemistry 5.1 software and a fixed bed reactor, respectively. In the absence of CO2 at 1193 K, the reduction of ZnO was accompanied with methane cracking, and metallic zinc, CO, and H2 were the main reaction products. This system could be utilized for the co-production of metallic zinc and synthesis gas, in which ZnO was a donor of oxygen. In the presence of CO2, ZnO plays as a catalyst in the CO2 reforming of methane and produces syngas with the average H2/CO ratio of 0.88 at 1193 K, which was close to the total reaction theoretic value of 1. It was also found that higher temperature favored high CH4 and CO2 conversions. XRD technique was used to characterize the ZnO species. The result showed that there were no differences in the peak profiles of the XRD patterns of the ZnO powder obtained before and after passing the CH4/CO2 mixed gases for 6 h at 1193 K. It is suggested that ZnO functions as a catalyst according to the redox cycle and metallic zinc plays the role of intermediate product in this process.

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Effect of water on the performance of Pd-ZSM-5 catalysts for the combustion of methane Bo Zhang;Xingyi Wang*;Ogtour M'Ramadj;Dao Li;Hua Zhang;Guanzhong Lu 2008, 17(1): 87-92.  DOI: 摘要 ( 10112 )   PDF   Palladium-based catalysts were prepared using impregnation (I) and ion-exchange method (E) with ZSM-5 as support. Pd-ZSM-5(I) and Pd-ZSM-5(E) catalysts presented the high activity for the combustion of methane. The order of activity was consistent with Br\onsted acidity of the catalysts: Pd-ZSM-5(I)>Pd-ZSM-5(E). It was shown by FT-IR that methane was adsorbed on the acidic bridging hydroxyl groups of ZSM-5-supported Pd catalysts. The effect of water on the activity of Pd-ZSM-5 was investigated. The inhibition effect of water on the conversion of methane was observed. However, water promoted the stability of Pd-ZSM-5 obviously during extended time periods. XPS measurement showed that Pd/Si ratio near the surface of Pd-ZSM-5(E) decreased more pronouncedly with time in dry stream than that of Pd-ZSM-5(I), this is attributed to the dispersion of Pd into the micropores. The addition of water, however, retarded Pd dispersion. And high partial pressure of methane reduced this effect of water vapor. The decrease in activity during the stability test can be explained on the basis of the reduction of Pd/Si ratio.

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COS hydrolysis in the presence of oxygen: Experiment and modeling Li Wang*;Shudong Wang;Quan Yuan;Guanzhong Lu 2008, 17(1): 93-97.  DOI: 摘要 ( 11236 )   PDF   A mathematical model of COS hydrolysis on Al2O3, with fouling of catalyst, has been developed. Kinetic studies were carried out in a fixed bed reactor under atmospheric pressure and low temperature (40-70 ℃). The effects of the COS inlet concentration, temperature, and relative humidity were analyzed. Experimental results of breakthrough curves were used to obtain kinetic parameters, which accounted for effects of S deposition on the inner-face of the catalyst. The model described the experimental breakthrough curves satisfactorily and well explained the performance of COS hydrolysis in the presence of oxygen. The exothermic heat of adsorption and activation energy, assuming Arrhenius type of temperature dependence of the equilibrium constant, were determined. Activation energy of COS hydrolysis and H2S oxidation were 35.9 kJ/mol, 19.6 kJ/mol; adsorption heat of H2O and H2S on Al2O3 were 45.1 and 60.1 kJ/mol respectively. Deactivation coefficient (α) was used to quantify the behavior of COS hydrolysis at different operating conditions. The effect of relative humidity on α is significant in the relative humidity range under study. Experimental data accorded well with model data in the studied range.

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Effect of CeO2 on the catalytic performance of Ni/Al2O3 for autothermal reforming of methane Xiulan Cai*;Xinfa Dong;Weiming Lin 2008, 17(1): 98-102.  DOI: 摘要 ( 10231 )   PDF   The effect of promoter Ce on the catalytic performance of Ni/Al2O3 catalyst for autothermal reforming of methane to hydrogen was investigated. The catalysts were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS). The results indicated that the catalytic performance of the catalysts was improved with the addition of Ce. Ni/Ce30Al70Oδ showed the highest CH4 conversion in operation temperatures ranging from 650 0Cto 850 0C. At the same time, the decrease in H2/CO ratio with increasing reaction temperature was consistent with the fact that water-gas shift reaction was thermodynamically unfavorable at higher temperatures. The XRD result indicated that adding Ce to Ni/Al2O3 catalyst prevented the formation of NiAl2O4 and facilitated the formation of NiO. The formation of NiO increased the number of active sites, resulting in higher activity. Comparing the TPR profiles of Ni/Ce30Al70Oδ with Ni/Al2O3, it could be clearly observed that with the addition of Ce, the total reduction peak areas in the middle and low temperatures increased. It was most probably that the addition of Ce inhibited the stronger interaction between Ni and Al2O3 to form the phase of NiAl2O4, and favored the formation of the strong interaction between NiO species and CeO2. Therefore, the addition of Ce to the Ni/Al2O3 catalyst increased the active surface that promoted the activity of the catalyst.

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Biosynthesis of poly-3-hydroxybutyrate with a high molecular weight by methanotroph from methane and methanol Yingxin Zhang;Jiaying Xin;Linlin Chen;Hao Song;Chungu Xia* 2008, 17(1): 103-109.  DOI: 摘要 ( 10627 )   PDF   Poly-3-hydroxybutyrate (PHB) can be produced by various species of bacteria. Among the possible carbon sources, both methane and methanol could be a suitable substrate for the production of PHB. Methane is cheap and plentiful not only as natural gas, but also as biogas. Methanol can also maintain methanotrophic activity in some conditions. The methanotrophic strain Methylosinus trichosporium IMV3011 can accumulate PHB with methane and methanol in a brief nonsterile process. Liquid methanol (0.1%) was added to improve the oxidization of methane. The studies were carried out using shake flasks. Cultivation was performed in two stages: a continuous growth phase and a PHB accumulation phase under the conditions short of essential nutrients (ammonium, nitrate, phosphorus, copper, iron (III), magnesium or ethylenediamine tetraacetate (EDTA)) in batch culture. It was found that the most suitable growth time for the cell is 144 h. Then an optimized culture condition for second stage was determined, in which the PHB concentration could be much increased to 0.6 g/L. In order to increase PHB content, citric acid was added as an inhibitor of tricarboxylic acid cycle (TCA). It was found that citric acid is favorable for the PHB accumulation, and the PHB yield was increased to 40% (w/w) from the initial yield of 12% (w/w) after nutrient deficiency cultivation. The PHB produced is of very high quality with molecular weight up to 1.5×106Da.

Communctions

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Vapor-phase synthesis of N-butylaniline from aniline and 1-butanol over Cu/SiO2 catalyst Xue Dong;Jing Liu;Lei Shi*;Qi Sun 2008, 17(1): 110-111.  DOI: 摘要 ( 8344 )   PDF   The Cu/SiO2 catalyst prepared by incipient wetness method exhibited very high activity and selectivity for the vapor-phase synthesis of N-butylaniline from aniline and 1-butanol. When Cu loading was 0.70 mmol/g-SiO2 and the catalyst precursor was calcined at 500 0C, 1-butanol conversion reached 99%, and the selectivity of N-butylaniline exceeded 97%.