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2010, Vol. 19, No. 1　Online: 2010-01-30

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A 13CO isotopic study on the CO promotion effect in methane dehydroaromatization reaction over a Mo/HMCM-49 catalyst Songdong Yao;Changyong Sun;Juan Li;Xiumin Huang;Wenjie Shen* 2010, 19(1): 1-5.  DOI: 摘要 ( 8072 )   PDF   The promotion effect of CO in methane dehydroaromatization was investigated using 13CO probe molecules. By alternative injection of 13CO to the methane feed, the distribution of 13CxC6−xH6 (x = 0–3) products changed significantly, confirming the participation of 13CO in the reaction network. The addition of 13CO did not change the conversion of CH4 but improved slightly the durability of the methane dehydroaromatization (MDA) reaction, which might be caused by the interaction of the dissociated oxygen species and the deposited carbon species. The ratio of 13CxC6−xH6 (x = 0–3) varied with the time on stream, which was determined by the competitive reactions of methane decomposition and 13CO dissociation.

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Kinetic models of natural gas combustion in an internal combustion engine M. Mansha*;A. R Saleemi; Badar M. Ghauri 2010, 19(1): 6-14.  DOI: 摘要 ( 9574 )   PDF   In this study, combustion of methane was simulated using four kinetic models of methane in CHEMKIN 4.1.1 for 0-D closed internal combustion (IC) engine reactor. Two detailed (GRIMECH3.0 & UBC MECH2.0) and two reduced (One step & Four steps) models were examined for various IC engine designs. The detailed models (GRIMECH3.0, & UBC MECH2.0) and 4-step models successfully predicted the combustion while global model was unable to predict any combustion reaction. This study illustrated that the detailed model showed good concordances in the prediction of chamber pressure, temperature and major combustion species profiles. The detailed models also exhibited the capabilities to predict the pollutants formation in an IC engine while the reduced schemes showed failure in the prediction of pollutants emissions. Although, there are discrepancies among the profiles of four considered model, the detailed models (GRIMECH3.0 & UBC MECH2.0) produced the acceptable agreement in the species prediction and formation of pollutants.

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Studies on the structure and catalytic performance of S and P promoted Na-W-Mn-Zr/SiO2 catalyst for oxidative coupling of methane Wen Zheng;Dangguo Cheng;Ning Zhu;Fengqiu Chen*;Xiaoli Zhan 2010, 19(1): 15-20.  DOI: 摘要 ( 11820 )   PDF   A series of Na-W-Mn-Zr/SiO2 catalysts promoted by different contents of S or/and P were prepared and investigated in oxidative coupling of methane to clarify the effect of S and P on the Na-W-Mn-Zr/SiO2 catalyst. From the characterization results, it is found that the addition of S and P to the Na-W-Mn-Zr/SiO2 catalyst helps the formation of active phases, such as -cristobalite, Na2WO4, ZrO2, and Na2SO4. Moreover, the addition of S and P increases the concentration of surface-active oxygen species by improving the migration of active components from the bulk phase to the surface of the catalyst. According to the activity test, impressive methane conversion and C2 hydrocarbons yield were obtained at a low temperature of 1023 K over the six-component Na-W-Mn-Zr-S-P/SiO2 catalyst, which contained 2 wt% S and 0.4 wt% P simultaneously. The deactivation of Na-W-Mn-Zr-S-P/SiO2 was due to the loss of surface active components.

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Density functional theory for adsorption of HCHO on the FeO(100) surface LinglingWang;Wenkai Chen* 2010, 19(1): 21-24.  DOI: 摘要 ( 9224 )   PDF   The density functional theory (DFT) and periodic slab model were used to get information concerning the adsorption of HCHO on the FeO(100) surface. A preferred _ 2-(C,O)-di-_ four-membered ring adsorption conformation on the Fe-top site was found to be the most favorable structure with the predicted adsorption energy of 210.7 kJ/mol. The analysis of density of states, Mulliken population, and vibrational frequencies before and after adsorption showed clear weakening of the carbonyl bond, and high sp 3 character on the carbon atom.

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Oxidative coupling of methane over La-promoted CaO catalysts: Influence of precursors and catalyst preparation method Vilas H. Rane*;Sopan T. Chaudhari;Vasant R. Choudhary 2010, 19(1): 25-30.  DOI: 摘要 ( 10724 )   PDF   The oxidative coupling of methane to C2 hydrocarbons has been studied over a series of La-promoted CaO (La/Ca = 0.05) catalysts, prepared using different precursor salts for CaO and La2O3 (viz. acetates, carbonates, nitrates and hydroxides) and catalyst preparation methods (viz. physical mixing of precursors, co-precipitation using ammonium carbonate/sodium carbonate as a precipitating agent), under different reaction conditions (temperature: 700–850 ◦C, CH4/O2 ratio: 4.0 and 8.0, and GHSV: 51360 cm3.g−1.h−1). The surface area and surface basicity/base strength distribution of the catalysts have also been investigated. The surface properties and catalytic activity/selectivity of the La-promoted CaO catalysts vary from catalyst to catalyst depending on the catalyst precursors used and catalyst preparation method. The basicity/base strength distribution is strongly influenced by the precursors (for CaO and La2O3) and catalyst preparation method. Basicity (total and strong basic sites measured in terms of CO2 chemisorbed at 50 ◦C and 500 ◦C, respectively) observed for the catalyst prepared by co-precipitation method is higher than that of the catalysts prepared by physical mixing method. The catalysts prepared by the nitrates of La- and Ca- and coprecipitated by the solution of sodium carbonate and ammonium carbonate exhibit different catalytic performance in OCM. The finding that no direct relationship between the surface basicity and catalytic activity/selectivity in OCM exists indicates that basicity is not solely responsible for obtaining high selectivity to C2 hydrocarbons.

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Studies on product distribution of alkali promoted iron catalyst in Fischer-Tropsch synthesis Ali Nakhaei Pour*;Masoud Zare;Yahya Zamani 2010, 19(1): 31-34.  DOI: 摘要 ( 9301 )   PDF   The dependencies of hydrocarbon product distributions of alkali promoted iron catalyst in Fischer-Tropsch synthesis have been studied. The concept of two superimposed Anderson-Schulz-Flory distributions has been applied for the representation of the effects of Mg, La and Ca promoters on product distributions. The FTS performance of the catalysts was tested in a fixed bed reactor under the conditions 563 K, 1.7 MPa, H2/CO = 1 and space velocities 4.86 and 13.28 nl·h−1·g−1 Fe . The results indicate that appropriate amounts of these promoters enhance the break in ASF distributions in the order Ca>Mg>La because of the rising of the catalyst surface basicity.

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Oxidative coupling of methane over (Na2WO4+Mn or Ce)/SiO2 catalysts: In situ measurement of electrical conductivity Zeinab Gholipour;Azim Malekzadeh*;Reza Hatami;Yadollah Mortazavi;Abasali Khodadadi 2010, 19(1): 35-42.  DOI: 摘要 ( 9348 )   PDF   The effects of manganese oxide or ceria promoters on the performance of Na2WO4/SiO2 catalysts for oxidative coupling of methane (OCM) are reported. The OCM reaction was performed in a continuous-flow microreactor at 800 ◦C, atmospheric pressure and under GHSV = 13200 ml·g−1 Cat·h−1. Catalysts were characterized by in situ conductivity measurement, FT-IR spectroscopy, XRD, SEMand temperature programmed reduction analysis. Manganese oxide promoted Na2WO4/SiO2 is considered as one of the active and selective catalysts for OCMreaction. Ceria with high oxygen storage capacity is selected as a proper oxygen activator, providing a higher concentration of the oxy-anion species which is suitable for OCM reaction and compared with manganese oxide. Electrical conductivity of the catalysts was measured in OCM reaction under oxidizing atmosphere, i.e. in the absence of methane. It was found that the trimetallic catalysts, i.e. the catalysts having sodium, tungsten and Mn or Ce species, exhibited similar crystalline structures and morphologies, which lead to suitable bulk properties for the formation of an active and selective catalyst. However, tungsten had significant effect on the texture and redox properties of the catalysts. It was also shown that the crystalline structure of the bimetallic (Na+Mn or Ce)/SiO2 samples was quite different. This reveals that the metal oxides have significant effect on the extent of crystallization, taking place in the course of interaction of sodium with silica support. Similar conductivities and catalytic performances of (Na2WO4+Mn or Ce)/SiO2 catalysts propose that the ability of Na2WO4/SiO2 for utilizing oxy-anions formed in presence of different metal oxides is limited.

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Lattice dynamical simulation of methane hydrate Lin Wang*;Shunle Dong 2010, 19(1): 43-46.  DOI: 摘要 ( 8553 )   PDF   INS (Inelastic Neutron Scattering) spectrum of methane hydrate was measured on MARI (a direct-geometry chopper spectrometer) at Rutherford Appleton Laboratory, UK. Compared with ice Ih, it is found that the whole spectrum of methane hydrate moves toward high-energy by about 1.5meV. Using lattice dynamical (LD) technique, computer simulations of methane hydrate were carried out. In the simulations, four potential models (BF, TIP3P, TIP4P, MCY) were employed to calculate the phonon density of states (PDOS). Comparing the calculated PDOS spectrum with the experimental spectrum, it is found that BF, TIP4P, and TIP3P potential lattices give out well-separated translational and librational bands while MCY potential lattice is unstable to do so and this model is not suitable to describe hydrate system.

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Ce-promoted Mn/Na2WO4/SiO2 catalyst for oxidative coupling of methane at atmospheric pressure Seyed Mehdi Kamali Shahri*;Ali Nakhaei Pour 2010, 19(1): 47-53.  DOI: 摘要 ( 9576 )   PDF   A series of Ce-promoted Mn-Na2WO4/SiO2 catalysts were prepared by incipient wetness impregnation method, and their catalytic performance for oxidative coupling of methane (OCM) was investigated at atmospheric pressure in a micro-quartz-tube reactor. The catalysts were characterized by X-ray diffraction (XRD), temperature program reduction (TPR) and BET surface area. Ce promoter increased surface area and Na2WO4 species dispersion, which enriched the amount of the surface species. In addition, Ce promoter increased the Na/W species reduction, but the reduction peak shifted to higher temperature. Stability test of 5wt%Ce catalyst indicated suitable performance and stability. The selectivity and yield of C2+ hydrocarbons after 50 h operation reached 65.5% and 19.6%, respectively, at 840 ◦C over 5wt%Ce-2wt%Mn- 5wt%Na2WO4/SiO2 catalyst.

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Oxidation of propane over ammonium-transition metal mixed keggin phosphomolybdate salts T. Mazari;C. Roch. Marchal;S. Hocine;N. Salhi;C. Rabia* 2010, 19(1): 54-60.  DOI: 摘要 ( 8057 )   PDF   Mixed ammonium-transition metal salts with formula of (NH4)xMyHzPMo12O40 (M= Ni2+, Co2+ or Fe 3+) denoted as MPMo12 have been investigated for the oxidation of propane, with molecular oxygen, at temperature range between 380 ◦C and 420 ◦C after in-situ pre-treatment performed at two heating rate of 5 or 9 ◦C/min. They were characterized by BET method, XRD, UV-Vis and IR techniques. The catalysts were found to be active in the propane oxidation and selective to propene or acrolein, in particular for samples pre-treated with the heating rate of 9 ◦C/min. FePMo12 was found the more active catalyst for propene (17.2% yield) with minimal over deep oxidation (0.3% yield in COx).

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Water gas shift activity of Co-Mo/MgO-Al2O3 catalysts presulfided with ammonium sulfide Yixin Lian;Huifang Wang;Weiping Fang;Yiquan Yang* 2010, 19(1): 61-66.  DOI: 摘要 ( 7881 )   PDF   Co-Mo/MgO-Al2O3 catalyst was presulfided with ammonium sulfide in aqueous solution and activated with synthesis gas for water gas shift reaction. The assay results indicate that the presulfided Co-Mo/MgO-Al2O3 catalyst exhibits an excellent catalytic activity and stability. XRD and EPR characterization results show that the O-S exchange might occur during the impregnation, leading to the formation of (NH4)2MoS4 (or (NH4)2MoxSy) precursor, which was then thermally decomposed and reduced to MoS2. The higher catalytic performance is attributed to an optimization formation of active Co-Mo sulfides, consisting of well dispersed MoS2 and Co-Mo-S phase due to the redispersion of Co sulfide particles over the edges of newly formed MoS2 crystallites.

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Vapor phase synthesis of N-butylaniline over copper-based catalysts Haiyan Zhu;Xue Dong;Lei Shi*;Qi Sun 2010, 19(1): 67-70.  DOI: 摘要 ( 9631 )   PDF   Cu-based catalysts, such as Cu/SiO2, Cu/-Al2O3 and Cu/SiO2-Al2O3, for the vapor phase synthesis of N-butylaniline from aniline and 1-butanol were investigated and the catalysts were characterized by BET, H2-TPR, XRD and NH3-TPD techniques. The results indicated that the dispersion of copper on support was greatly influenced by the interaction between Cu and the support. Copper-based catalyst with larger amounts of acidic sites did not favor the synthesis of N-butylaniline because more by-products were produced. Among the tested catalysts, Cu/SiO2 showed excellent catalytic activity and stability with a yield of N-butylaniline above 90% during the reaction time of 200 h.

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Water transfer characteristics during methane hydrate formation and dissociation processes inside saturated sand Peng Zhang*;Qingbai Wu;Yibin Pu;Guanli Jiang;Jing Zhan;Yingmei Wang 2010, 19(1): 71-76.  DOI: 摘要 ( 7462 )   PDF   Gas hydrates formation and dissociation processes inside porous media are always accompanied by water transfer behavior, which is similar to the water behavior of ice freezing and thawing processes. These processes have been studied by many researchers, but all the studies are so far on the water transfer characteristics outside porous media and the water transfer characteristics inside porous media have been little known. In this study, in order to study the water transfer characteristics inside porous media during methane hydrate formation and dissociation processes, a novel apparatus with three pF-meter sensors which can detect water content changes inside porous media was applied. It was experimentally observed that methane hydrate formation processes were accompanied by water transfer from bottom to top inside porous media, however, the water behavior during hydrate dissociation processes was abnormal, for which more studies are needed to find out the real reason in our future work.

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A new way to synthesize benzoin isopropyl ether on Cu-Fe-hydrotalcite Xianmei Xie*;Xia An;Kai Yan;Xu Wu;Jianling Song;ZhizhongWang 2010, 19(1): 77-80.  DOI: 摘要 ( 7719 )   PDF   An efficient synthesis of benzoin isopropyl ether with benzaldehyde and propanol in the presence of heterogeneous recyclable Cu-Fe-hydrotalcite catalyst has been explored. Cu-Fe-hydrotalcite was firstly successfully synthesized over Jahn-Teller effect of Cu2+. The catalytic test result showed that Cu-Fe-hydrotalcite could be used as a good catalyst in the synthesis of benzoin isopropyl ether. The highest conversion of benzaldehyde was 59.7% and the selectivity of benzoin isopropyl ether was nearly 100%. By this new method, not only was the cyanide poisoning avoided, but also the synthesis of benzoin isopropyl ether could be completed in one step instead of the traditional two steps with both condensation and etherification.

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Separation of ionic liquids from dilute aqueous solutions using the method based on CO2 hydrates Xiaoming Peng;Yufeng Hu*;Chuanwei Jin;Yingguo Liang 2010, 19(1): 81-85.  DOI: 摘要 ( 10592 )   PDF   Ionic liquids (ILs) have been regarded as the potential novel solvents for improved analytical- and process-scale separation methods. The development of methods for the recovery of ILs from aqueous solutions to escape contamination and recycle samples will ultimately govern the viability of ILs in the future industrial applications. Therefore, in this paper a new method for separation of ILs from their dilute aqueous solutions and simultaneously purification of water was proposed on the basis of the CO2 hydrate formation. For illustration, the dilute aqueous solutions with concentrations of ILs ranging from 2×10−3 mol% to 2×10−1 mol% were concentrated. The results show that the separation efficiency is very impressive and that the new method is applicable to aqueous solutions of both hydrophobic and hydrophilic ILs. Compared to the literature separation method based on the supercritical CO2, the new method is applicable to lower concentrations, and more importantly, its operation condition is gentler.

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Catalytic oxidation of soot particulates over MnOx-CeO2 oxides prepared by complexation-combustion method Wenjuan Shan*;Na Ma;Jiali Yang;Xiaowei Dong;Chang Liu;Lingling Wei 2010, 19(1): 86-90.  DOI: 摘要 ( 8811 )   PDF   MnOx-CeO2 oxides prepared by complexation-combustion method were used for soot oxidation. The highest conversion rate of soot was obtained on aMnOx-CeO2(4) oxide prepared under mild acid condition of pH = 4, where the oxidation temperature corresponding to maximum activity was decreased more than 150 ◦C compared with that of un-catalytic soot oxidation. The structure and property of the catalysts were investigated by X-ray powder diffraction (XRD) and temperature programmed reduction (TPR). The results indicated that there were at least two kinds of Mn species present in MnOx-CeO2 catalysts, i.e. Mn ions within CeO2 lattice and high dispersion MnOx on the surface of CeO2. The presence of Mn ions in the CeO2 lattice improved the oxygen vacancy due to the charge difference, and the CeO2 considerably decreased the reduction temperature of MnOx. The capability to activate oxygen by the oxygen exchange between gas phase O2 and oxygen into the oxide contributed to the high catalytic activity for the reaction.

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Support effects on the chemical property and catalytic activity of Co-Mo HDS catalyst in sulfur recovery Ali Nakhaei Pour;Ali Morad Rashidi*;Kherolah Jafari Jozani;Ali Mohajeri;Payman Khorami 2010, 19(1): 91-95.  DOI: 摘要 ( 9649 )   PDF   Effects of carbon nanotubes (CNT) and alumina (-Al2O3) supports on the catalytic activities of hydrodesulfurization (HDS) process over Co-Mo catalyst have been studied. XRD results indicated that the main active phases in CNT and -Al2O3 supported Co-Mo catalysts are MoO2 and MoO3, respectively. The TPR results reveal that the reduction peak temperatures of the active species on CNT supported Co-Mo catalyst is lower than those on alumina supported Co-Mo catalyst, indicating that the CNT supports favor the reduction of active species. Catalytic evaluation results displayed that the sulfur content in the reaction products on the CNT supported Co-Mo catalyst is lower than that on the alumina supported Co-Mo catalyst if the HDS reaction was carried out at a temperature above 583 K.