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2010, Vol. 19, No. 2　Online: 2010-03-30

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Development and testing of a detailed kinetic mechanism of natural gas combustion in internal combustion engine M. Mansha*;A. R. Saleemi;Badar M. Ghauri;Naveed Ramzan 2010, 19(2): 97-106.  DOI: 摘要 ( 10170 )   PDF   A detailed chemical mechanism to describe the combustion of natural gas in internal combustion (IC) engine has been developed, which is consisting of 233 reversible reactions and 79 species. This mechanism accounts for the oxidation of methane, ethane, propane and nitrogen. It has been tested using IC engine model of CHEMKIN 4.1.1 and experimental measurements. The performance of the proposed mechanism was evaluated at various equivalence ratios (φ = 0.6 to φ = 1.3), initial reactor conditions (Tini = 500 to 3500  ℃ ; Pini = 1.0 to 10 atm) and engine speed (2000-7000 rpm). The proposed kinetic mechanism shows good concordances with GRI3.0 mechanism especially in the prediction of temperature, pressure and major product species (H2O, CO2) profiles at stoichiometric conditions (φ = 1.0). The experimental results of measured cylinder pressure, species fractions were also in agreement with simulation results derived from the proposed kinetic mechanism. The proposed mechanism successfully predicts the formation of gaseous pollutants (CO, NO, NO2, NH3) in the engine exhaust. Although there are some discrepancies among each simulation profile, the proposed detailed mechanism is good to represent the combustion of natural gas in IC engine.

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Effect of nano-particle size on product distribution and kinetic parameters of Fe/Cu/La catalyst in Fischer-Tropsch synthesis Ali Nakhaei Pour;*;Mohammad Reza Housaindokht;Sayyed Faramarz Tayyari;Jamshid Zarkesh 2010, 19(2): 107-116.  DOI: 摘要 ( 9272 )   PDF   Effects of nano-particle size on hydrocarbon production rates and distributions for precipitated Fe/Cu/La catalysts in Fischer-Tropsch synthesis were investigated. Nano-structured iron catalyst was prepared by micro-emulsion method. The concept of two superimposed Anderson-Schulz-Flory (ASF) distributions has been applied for the representation of the effects of reaction conditions and nano-particles size on kinetics parameters and product distributions. These results reveal that by reducing the particle size of catalyst, the break in ASF distributions was decreased. Also useful different kinetics equations for synthesis of C3 to C9 and C10 to C22 were determined by using α1 and α2 chain growth probabilities.

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Effects of Ce/Zr ratio on the structure and performances of Co-Ce1-xZrxO2 catalysts for carbon dioxide reforming of methane Ning Wang;Wei Chu*;Liqiong Huang;Tao Zhang 2010, 19(2): 117-122.  DOI: 摘要 ( 9674 )   PDF   The Co-incorporated Ce1-xZrxO2 catalysts were prepared by co-precipitation for carbon dioxide reforming of methane. The ratio of Ce to Zr was varied to optimize the performances of co-precipitated Co-Ce-Zr-Ox catalysts. The prepared catalysts were characterized by various physico-chemical characterization techniques including TPR, X-ray diffraction, N2 adsorption at low temperature, XPS and CO2-TPSR. The co-precipitated Co-Ce0.8Zr0.2O2 sample containing 16% CoO exhibited a higher catalytic activity among the five catalysts, and the activity was maintained without significant loss during the reaction for 60 h. Under the conditions of 750 ℃, 0.1 MPa, 36000 ml/(h·g{cat}), and CO2/CH4 molar ratio of 1 : 1, the CO2 conversion over this catalyst was 75% while the CH4 conversion was 67%. The cubic Ce0.8Zr0.2O2 facilitated a higher dispersion and a higher reducibility of the cobalt component, and the apparent activation energy for Co-Ce0.8Zr0.2O2 sample was 49.1 kJ/mol in the CO2/CH4 reforming reaction. As a result, the Co-Ce0.8Zr0.2O2 sample exhibited a higher activity and stability for the reforming of CH4 with CO2.

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Oxidative dehydrogenation of propane under steady-state and transient regimes over alumina-supported catalysts prepared from mixed V2W4O4-19 hexametalate precursors Sebastien Paul;*;Elise Berrier;;Marcia Cristina Kaezer França;Jean-Guillaume Eon 2010, 19(2): 123-133.  DOI: 摘要 ( 8904 )   PDF   An integrated approach combining the development of an innovative catalyst and the research of a set of adequate operating conditions for the propane oxidative dehydrogenation (ODH) is described. The experimental set-up, specially designed for steady-state and transient studies is presented. The preparation method, the characterization and the performances in steady-state and transient regimes of catalysts based on V2W4O4-19 Lindqvist isopolyanion used as a precursor and supported on alumina are reported. The influence of the preparation method of the catalyst and the role of water in the feed gas are more particularly discussed.

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Effect of cobalt oxide on performance of Pd catalysts for lean-burn natural gas vehicles in the presence and absence of water vapor Enyan Long;Xiaoyu Zhang;Yile Li;Zhimin Liu;Yun Wang;Maochu Gong;Yaoqiang Chen* 2010, 19(2): 134-138.  DOI: 摘要 ( 211 )   PDF   Pd-based catalysts modified by cobalt were prepared by co-impregnation and sequential impregnation methods, and characterized by X-ray powder diffraction (XRD), N2 adsorption/desorption (Brunauer-Emmet-Teller method), CO-chemisorption and X-ray photoelectron spectroscopy (XPS). The activity of Pd catalysts was tested in the simulated exhaust gas from lean-burn natural gas vehicles. The effect of Co on the performance of water poisoning resistance for Pd catalysts was estimated in the simulated exhaust gas with and without the presence of water vapor. It was found that the effect of Co significantly depended on the preparation process. PdCo/La-Al2O3 catalyst prepared by co-impregnation exhibited better water-resistant performance. The results of XPS indicated that both CoAl2O4 and Co3O4 were present in the Pd catalysts modified by Co. For the catalyst prepared by sequential impregnation method, the ratio of CoAl2O4/Co3O4 was higher than that of the catalyst prepared by co-impregnation method. It could be concluded that Co3O4 played an important role in improving water-resistant performance.

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Water transfer characteristics in the vertical direction during methane hydrate formation and dissociation processes inside non-saturated media Peng Zhang*;Qingbai Wu;Guanli Jiang;Jing Zhan;Yingmei Wang 2010, 19(2): 139-145.  DOI: 摘要 ( 216 )   PDF   In order to study water transfer characteristics inside non-saturated media during methane hydrate formation and dissociation processes, water changes on the top, middle and bottom locations of experimental media during the reaction processes were continuously followed with a novel apparatus with three pF-meter sensors. Coarse sand, fine sand and loess were chosen as experimental media. It was experimentally observed that methane hydrate was easier formed inside coarse sand and fine sand than inside loess. Methane hydrate formation configuration and water transfer characteristics during methane hydrate formation processes were very different among the different non-saturated media, which were important for understanding methane hydrate formation and dissociation mechanism inside sediments in nature.

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Novel predictive tool for accurate estimation of packed column size Alireza Bahadori*;Hari B. Vuthaluru 2010, 19(2): 146-150.  DOI: 摘要 ( 215 )   PDF   Traditionally the majority of fractionation columns in natural gas processing plants were equipped with trays. However an option to trayed columns is to use packing. Packed columns offer a larger surface area per unit volume for mass transfer and the continuous gas to liquid contact throughout the column rather than at specific levels (such as in tray columns). For process design purposes, it is essential to estimate the pressure drop for enabling the proper operation of packed columns. In this study, a simple generalized pressure drop correlation (GPDC) which is easier than existing approaches requiring more complicated and longer computations is developed for sizing randomly packed fractionation columns for pressure drops up to 150 mm water per meter of packing. This correlation can be used to estimate pressure drop for a given loading and column diameter. Alternatively, for a given pressure drop the diameter can be determined. The predictions from the proposed correlation have been compared with reported data and found good agreement with average absolute deviation hovering around 4.9%. The proposed predictive tool is superior owing to its accuracy and clear numerical background, wherein the relevant coefficients can be retuned quickly if new and more accurate data are available in the future. This proposed simple-to-use approach can be of immense practical value for the engineers and scientists to have a quick check on the pressure drop in packed columns for a given loading and column diameter. In particular, gas engineers would find the proposed approach can be used very friendly involving no complex expressions with transparent and easy-to-handle calculation steps.

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XPS study of potassium-promoted molybdenum carbides for mixed alcohols synthesis via CO hydrogenation Minglin Xiang;*;Debao Li;Juan Zou;Wenhuai Li;Yuhan Sun*;Xichun She 2010, 19(2): 151-155.  DOI: 摘要 ( 251 )   PDF   The X-ray photoelectron spectroscopy (XPS) was used to investigate the surface characteristic of potassium-promoted or un-promoted both β-Mo2C and α-MoC1-x pretreated by syngas at different temperatures, and the promotional effect of potassium on the catalytic performance was also studied. XPS results revealed that the content of surface Mo and its valence distribution between β-Mo2C and α-MoC1-x were quite different. Promoted by potassium, the remarkable changes were observed for surface composition and valence of Mo distribution over β-Mo2C . Potassium had strong electronic effect on β-Mo2C, which led to a higher Mo4+ content. On the contrary, potassium had little electronic effect on α-MoC1-x, and K-Mo interaction was weak. Therefore, Mo0 and Mo2+ became the dominant species on the catalyst surface, and the Mo4+ content showed almost no increase as the pretreatment temperature enhanced. In terms of catalytic performance of molybdenum carbides, the increase in Mo0 most likely explained the increase in hydrocarbon selectivity, yet Mo4+ might be responsible for the alcohols synthesis.

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Growth of carbon nanotubes on the novel FeCo-Al2O3 catalyst prepared by ultrasonic coprecipitation Jie Wen;Wei Chu*;Chengfa Jiang;Dongge Tong 2010, 19(2): 156-160.  DOI: 摘要 ( 10378 )   PDF   FeCo-Al2O3 catalyst was prepared by an ultrasonic coprecipitation (UC) method for the growth of carbon nanotubes (CNTs) from catalytic decomposition of methane. Its catalytic performance was compared with that of the FeCo-Al2O3 catalyst counterparts prepared by stepwise impregnation (I) and conventional coprecipitation (C) methods, respectively. The structure and properties of the catalysts and the CNTs as produced thereon were investigated by means of XRD, XPS, TEM and N2 adsorption techniques. It was found that the catalyst prepared by the ultrasonic coprecipitation method was more active, and the yield and purity of the synthesized CNTs were promoted evidently. The XPS results revealed that there were more active components on the surface of the catalyst prepared by the ultrasonic coprecipitation method. On the other hand, N2 adsorption demonstrated that the catalyst prepared by the ultrasonic coprecipitation method conferred larger specific surface area, which was beneficial to dispersion of active components. TEM images further confirmed its higher dispersion. These factors could be responsible for its higher activity for the growth of CNTs from catalytic decomposition of methane.

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Synthesis of ethyl acetate by esterification of acetic acid with ethanol over a heteropolyacid on montmorillonite K10 Hanumant Gurav;Vijay V. Bokade* 2010, 19(2): 161-164.  DOI: 摘要 ( 14009 )   PDF   In present work, liquid phase esterification of acetic acid with ethanol over dodecatungestophosphoric acid (DTPA) supported on K10 montmorillonite was systematically studied and optimization of process parameters was carried out. The 20% m/m DTPA/K10 was found to be the optimum catalyst with 90% acetic acid conversion and 100% ethyl acetate selectivity. The study was also explored to see the feasibility of 20% m/m DTPA/K10 as a catalyst for the alkylation of acetic acid with other alcohols like methanol, iso-propanol and n-butanol. The 20% m/m DTPA/K10 has shown increased activity with the increase in carbon number, at the same alcohol reflux. The results are novel.

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Synthesis of ethylidene diacetate from dimethyl ether, CO and H2 Dianhua Liu*;Xin Huang;Lei Hu;Dingye Fang;Weiyong Ying;Dasheng Chen 2010, 19(2): 165-168.  DOI: 摘要 ( 8891 )   PDF   Ethylidene diacetate was prepared by reacting dimethyl ether, acetic acid and syngas in the presence of a catalytic system comprising RhI3, PPh3 and CH3I. The effects of reaction temperature, pressure, time and the CO/H2 molar ratio on the conversion of dimethyl ether and the product selectivity were investigated under the same catalyst formulation. Results showed that a maximum conversion of dimethyl ether was obtained when a mixture consisting of 0.3 mol dimethyl ether and 120 ml acetic acid was reacted at 180 ℃ and 3.0 MPa for 10 h at a stirring speed of 600 rpm under a syngas flow with a CO/H2 molar ratio of 2.5, which was catalyzed by a catalyst mixture comprising 0.3 g RhI3, 6 g PPh3 and 1.3 g CH3I. The selectivity of ethylidene diacetate increased with temperature, decreased with the CO/H2 molar ratio and exhibited a maximum with pressure.

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Effect of binder on the properties of iron oxide sorbent for hot gas desulfurization Fang Zhu;*;Chunhu Li;Huilin Fan 2010, 19(2): 169-172.  DOI: 摘要 ( 205 )   PDF   The most difficult problem in hot gas desulfurization in Integrated Coal Gasification Combined Cycle (IGCC) is the pulverization of sulfur removal sorbents. Appropriate binders for hot gas sulfur removal sorbents can solve the pulverization problem. In this paper, six sorbents with binders of different argillaceous minerals were prepared by mechanical mixing method. Desulfurization behavior for hot gas desulfurization sorbents was investigated in a fixed-bed reactor. Result showed that sorbent NTKW2 with binder of clay had a better sulfidation performance. NTKW2 had a more stable performance than other sorbents in the continuous sulfidation-regeneration cycles. Sulfur capacity of sorbent remained the same in each cycle. The desulfurization efficiency and mechanical strength of NTKW2 were the best among the tested sorbents. The behavior of NTKW2 at different temperatures showed different performances, and the best reaction temperature was 550 ℃. Higher heat stability, sulfur capacity and desulfurization efficiency were found on NTKW2 in six continuous sulfidation-regeneration cycles.

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Suppressed formation of CO2 and H2O in the oxidative coupling of methane over La2O3/MgO catalyst by surface modification Zhiming Gao*;Yingxiao Shi 2010, 19(2): 173-178.  DOI: 摘要 ( 8318 )   PDF   Oxidative coupling of methane (OCM) is a promising way to convert methane into C2 hydrocarbons. However, CO2 and H2O are by-products of the reaction. To utilize the higher activity of lanthanum oxide and save its usage, MgO supported La2O3 catalyst was prepared. Surface modification of the catalyst with nitric acid was made to suppress the formation of the by-products. Experimental results indicated that the addition of nitric acid increased the surface oxygen species with binding energy of ca. 531.7 eV and at the same time reduced the pore volume of the catalyst. These effects of nitric acid finally led to the increase of C2 selectivity and the decrease of the by-products formation. Hydrogen selectivity was found about 14%-18% over the catalysts adopted in this work.

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Study on electronic density topology of various cluster models of Mg/Al hydrotalcite by density functional theory Renqing Lv*;Nina Zhang 2010, 19(2): 179-184.  DOI: 摘要 ( 8164 )   PDF   The geometry and electronic topology properties of Mg/Al hydrotalcite cluster models were comparatively investigated by means of density functional theory at GGA/DND levels. The results suggested that cluster model containing seven octahedral cations was the smallest size to be employed to simulate other properties. The fact that then+ charge of cluster models containingnaluminum atoms can reflect electronic properties of anionic clay layer sheet. The bond lengths of clusters can be modified by terminating with or without OH-/H2O groups in terms of principle of bond order conservation.

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Effect of H2S on the transformation of 1-hexene over NiMoS/r-Al2O3 with hydrogen Xiqiang Si;Daohong Xia*;Yuzhi Xiang;Yulu Zhou 2010, 19(2): 185-188.  DOI: 摘要 ( 8708 )   PDF   The effect of H2S contents on the transformation of 1-hexene with hydrogen over NiMoS/γ-Al2O3 catalyst was investigated. Inhibition of H2S on both hydrogenation and isomerization reactions of olefin has been demonstrated. And the promotion effect of H2S on the formation of C6 thiols and C12 thioethers has also been observed. It was found out that there was only one type of active site on the NiMoS/γ-Al2O3 for reactions which include hydrogenation reaction, isomerization reaction and sulfides formation reaction, and the formation reactions of sulfides were superior to both hydrogenation and isomerization reactions. The reaction network for the conversion of 1-hexene in the presence of H2S was proposed.

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A novel correlation approach for prediction of natural gas compressibility factor Ehsan Heidaryan*;Amir Salarabadi;Jamshid Moghadasi 2010, 19(2): 189-192.  DOI: 摘要 ( 9072 )   PDF   Gas compressibility factor (z-Factor) is one of the most important parameters in upstream and downstream calculations of petroleum industries. The importance of z-Factor cannot be overemphasized in oil and gas engineering calculations. The experimental measurements, Equations of State (EoS) and empirical correlations are the most common sources of z-Factor calculations. There are more than twenty correlations available with two variables for calculating the z-Factor from fitting in an EoS or just through fitting techniques. However, these correlations are too complex, which require initial value and more complicated and longer computations or have magnitude error. The purpose of this study is to develop a new accurate correlation to rapidly estimate z-Factor. Result of this correlation is compared with large scale of database and experimental data also. Proposed correlation has 1.660 of Absolute Percent Relative Error (E{ABS}) versus Standing and Katz chart and has also 3.221 of E{ABS} versus experimental data. The output of this correlation can be directly assumed or be used as an initial value of other implicit correlations. This correlation is valid for gas coefficient of isothermal compressibility (cg) calculations also.

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Promoter effect on the CO2-H2O formation during Fischer-Tropsch synthesis on iron-based catalysts Ali Nakhaei Pour*;Seyed Mehdi Kamali Shahri;Yahya Zamani;Akbar Zamanian 2010, 19(2): 193-197.  DOI: 摘要 ( 10818 )   PDF   The effects of Mg, La and Ca promoters on primary and secondary CO2 and H2O formation pathways during Fischer-Tropsch synthesis on precipitated Fe/Cu/SiO2 catalysts are investigated. The chemisorbed oxygen atoms in the primary pathway formed in the CO dissociation steps reacted with co-adsorbed hydrogen or carbon monoxide to produce H2O and CO2, respectively. The secondary pathway was the water-gas shift reaction. The results indicated that the CO2 production led to an increase in both primary and secondary pathways, and H2O production decreased when surface basicity of the catalyst increased in the order Ca > Mg > La.

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Fast- and ultra-fast laser pulse induced reactions between carbon dioxide and methane F. Jaco Kotze;Christien A. Strydom*;Anton du Plessis;Thulani L. Dlamini 2010, 19(2): 198-202.  DOI: 摘要 ( 8761 )   PDF   The direct excitation of CO2 using fast (nanosecond) and ultrafast (femtosecond) pulsed lasers was investigated. A gas reaction cell was used to excite CO2 in a 50 : 50 mixture of CO2 and CH4 using nano- and femtosecond laser systems, to induce a reaction between these two compounds. FT-IR spectra showed that CO was formed using the nanosecond and femtosecond laser systems. It was also found that hydrocarbons, containing C--C bonds were formed. For both the nanosecond and femtosecond laser, it was found that more C-C higher hydrocarbons were formed after 5 h compared to 3 h of irradiation. Irradiation at pressures of 250, 350 and 500 kPa with the femtosecond laser system showed the expected increase in the amount of CO formed with an increase in pressure. Results from this study showed that carbon dioxide and methane can be activated successfully using nanosecond laser pulses at 2000 nm and femtosecond laser pulses at 795 or 2000 nm and that these activated species react to form CO and C-C containing products.