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2011, Vol. 20, No. 6　Online: 2011-11-20

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Communication

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Performance assessment of an inline horizontal swirl tube cyclone for gas-liquid separation at high pressure Nurhayati Mellon*, Azmi M. Shariff 2011, 20(6): 565-567.  DOI: 10.1016/S1003-9953(10)60245-9 摘要 ( 9735 )   The application of swirl tube cyclone for gas-liquid separation is attractive due to its small size and weight. However, very scarce information on the performance of the swirl tube cyclone especially at high operating pressure emulating actual field condition was published in journals. Performance assessment was usually done at a low operating pressure using either air-water, air-fine particle mixtures or dense gas such as SF6. This paper fills the existing gaps and reports the initial findings on the performance assessment of a horizontal swirl tube cyclone for gas-liquid separation operating at a flow rate of 5 MMSCFD at 40--60 bar operating pressure.

Articles

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Thermodynamic analysis of mixed and dry reforming of methane for solar thermal applications Y. Sun*, T. Ritchie, S. S. Hla, S. McEvoy, W. Stein, J. H. Edwards 2011, 20(6): 568-576.  DOI: 10.1016/S1003-9953(10)60235-6 摘要 ( 11920 )   Thermodynamic analysis of the reforming of methane with carbon dioxide alone ("dry reforming") and with carbon dioxide and steam together ("mixed reforming") is performed as part of a project which investigates the suitability of these endothermic reactions for the storage of solar thermal energy. The Gibbs free energy minimization method was employed to identify thermodynamically optimal operating conditions for dry reforming as well as mixed reforming with a desired H2/CO molar ratio of 2. The non-stoichiometric equilibrium model was developed using FactSage software to conduct the thermodynamic calculations for carbon formation, H2/CO ratio, CH4 conversion and H2 yield as a function of reaction temperature, pressure and reactant molar ratios. Thermodynamic calculations demonstrate that in the mixed reforming process, optimal operating conditions in a carbon-free zone are under H2O/CH4/CO2 = 1.0/1.0/0.5, p = 1 to 10 bar andT = 800 to 850 ℃ for the production of syngas with a H2/CO molar ratio of 2. Under the optimal conditions, the maximum H2 yield of 88.0% is achieved at 1 bar and 850 ℃ with a maximum CH4 conversion of 99.3%. In the dry reforming process, a carbon formation regime is always present at a CO2/CH4 molar ratio of 1 forT = 700-1000 ℃ andp = 1-30 bar, whereas a carbon-free regime can be obtained at a CO2/CH4 molar ratio greater than 1.5 andT≥800 ℃.

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Molecular dynamics simulation of structure H clathrate-hydrates of binary guest molecules Hamid Erfan-Niya, Hamid Modarress* 2011, 20(6): 577-584.  DOI: 10.1016/S1003-9953(10)60242-3 摘要 ( 11391 )   Molecular dynamics (MD) simulations are performed to study the stability of structure H clathrate-hydrates of methane+large-molecule guest substance (LMGS) at temperatures of 270, 273, 278 and 280 K under canonical (NVT-) ensemble condition in a 3×3×3 structure H unit cell replica with 918 TIP4P water molecules. The studied LMGS are 2-methylbutane (2-MB), 2, 3-dimethylbutane (2, 3-DMB), neohexane (NH), methylcyclohexane (MCH), adamantane and tert-butyl methyl ether (TBME). In the process of MD simulation, achieving equilibrium of the studied system is recognized by stability in calculated pressure for NVT- ensemble. So, for the accuracy of MD simulations, the obtained pressures are compared with the experimental phase diagrams. Therefore, the obtained equilibrium pressures by MD simulations are presented for studying the structure H clathrate-hydrates. The results show that the calculated temperature and pressure conditions by MD simulations are consistent with the experimental phase diagrams. Also, the radial distribution functions (RDFs) of host-host, host-guest and guest-guest molecules are used to analysis the characteristic configurations of the structure H clathrate-hydrate.

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Catalytic methanation reaction over supported nickel-rhodium oxide for purification of simulated natural gas Wan Azelee Wan Abu Bakar*, Rusmidah Ali, Susilawati Toemen 2011, 20(6): 585-594.  DOI: 10.1016/S1003-9953(10)60236-8 摘要 ( 10944 )   In this research, new catalyst with high industrial impact is developed, which can catalyze the conversion of CO2 to methane through methanation reaction. A series of catalysts based on nickel oxide were prepared using wetness impregnation technique and ageing, followed by calcination at 400 ℃. Rh/Ni (30 : 70)/Al2O3 catalyst was revealed as the most potential catalyst based on the results of catalytic activity measurement monitored by Fourier Transform Infrared Spectroscopy (FTIR) and Gas Chromatography (GC). The results showed 90.1% CO2 conversion and 70.8% yield at 400 ℃.

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Theoretical studies of adsorption property on Ir4/MgO and Ir4/γ-Al2O3 Xianyong Pang*, Duichun Li, Zizhang Wei, Jinmo Zhao, Guichang Wang* 2011, 20(6): 595-602.  DOI: 10.1016/S1003-9953(10)60237-X 摘要 ( 9882 )   The adsorption properties of atomic and molecular species on Ir4/MgO and Ir4/γ-Al2O3 have been systematically studied by means of plane-wave density functional theory (DFT) calculations using the periodic boundary conditions. The binding energies of these species were ordered as follows: H2O<C2H4<H<OH<S< N<O<C. The adsorption energies of adatoms on Ir4/MgO were larger than those on Ir4/γ-Al2O3 except hydrogen atom, but were in reverse for the molecules calculated. In addition, the difference of adsorption energies on MgO and γ-Al2O3 supports has been elucidated by analyzing the electronic properties. A detailed investigation on state density clarifies the nature of the magnitude of adsorption energy. These calculated results are consistent well with the available experimental and theoretical results.

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Fuzzy model prediction of Co (III)/Al2O3 catalytic behavior in Fischer-Tropsch synthesis Mohammad Ali Takassi, Mahdi Koolivand Salooki*, Morteza Esfandyari 2011, 20(6): 603-610.  DOI: 10.1016/S1003-9953(10)60240-X 摘要 ( 10446 )   The application of Co (III)/Al2O3 catalyst in Fischer-Tropsch synthesis (FTS) was studied in a wide range of synthesis gas conversions and compared with Fuzzy Simulation results. Present study applies fuzzy model to predicting the product composition of CH4, CO2 and CO in Fischer-Tropsch process for natural gas synthesis, in which the input vector was 4-dimension including four variables (operating pressure, operating temperature, time and CO/H2 ratio) of 70 different experiments and the output product is a composition of CO2, CO and CH4. The Mamdani algorithm has been applied to the training of the fuzzy system and the test set was used to evaluate the performance of the system includingR2, ARE, AARE and SD. The results demonstrated that the predicted values from the model were in good consistency with the experimental data. The work indicates how fuzzy inference system (FIS), as a promising predicting technique, would be effectively used in FTS.

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A DFT theoretical study of CH4 dissociation on gold-alloyed Ni(111) surface Hongyan Liu, Ruixia Yan, Riguang Zhang, Baojun Wang*, Kechang Xie 2011, 20(6): 611-617.  DOI: 10.1016/S1003-9953(10)60252-6 摘要 ( 10581 )   A density-functional theory (DFT) method has been conducted to systematically investigate the adsorption of CHx (x = 0~4) as well as the dissociation of CHx (x = 1~4) on (111) facets of gold-alloyed Ni surface. The results have been compared with those obtained on pure Ni(111) surface. It shows that the adsorption energies of CHx(x = 1~3) are lower, and the reaction barriers of CH4 dissociation are higher in the first and the fourth steps on gold-alloyed Ni(111) compared with those on pure Ni(111). In particular, the rate-determining step for CH4 dissociation is considered as the first step of dehydrogenation on gold-alloyed Ni(111), while it is the fourth step of dehydrogenation on pure Ni(111). Furthermore, the activation barrier in rate-determining step is higher by 0.41 eV on gold-alloyed Ni(111) than that on pure Ni(111). From above results, it can be concluded that carbon is not easy to form on gold-alloyed Ni(111) compared with that on pure Ni(111).

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Preparation, characterization and catalytic behavior of hierachically porous CuO/α-Fe2O3/SiO2 composite material for CO and o-DCB oxidation Xiaodong Ma*, Xi Feng, Xuan He, Hongwen Guo, Lu Lü 2011, 20(6): 618-622.  DOI: 10.1016/S1003-9953(10)60253-8 摘要 ( 9386 )   Hierachically porous (HP) CuO/α-Fe2O3/SiO2 composite material was fabricated by sol-gel method and multi-hydrothermal processes using HP-SiO2 as support. The resulting material was characterized by N2 adsorption-desorption, X-ray diffraction and scanning electron microscopy. The as-prepared CuO/Fe2O3/HP-SiO2 sample, with α-Fe2O3 and CuO nanocrystals, possessed a co-continuous skeleton, through-macroporous and mesoporous structure. Its catalytic behavior for CO and o-DCB oxidation was investigated. The result showed that CuO/Fe2O3/HP-SiO2 catalyst exhibited high catalytic activity for both CO and o-DCB oxidation, indicating its potential application in combined abatement of CO and chlorinated volatile organic compounds.

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Catalytic combustion of ethyl acetate over CeMnOx and CeMnZrOx compounds synthesized by coprecipitation method Xiaoshuang Li, Jianli Wang, Chuanwen Liao, Hongyan Cao, Yaoqiang Chen, Maochu Gong* 2011, 20(6): 623-628.  DOI: 10.1016/S1003-9953(10)60249-6 摘要 ( 9703 )   Ce0.6Mn0.4O2 catalysts with different sources of manganese and Ce0.6-xZrxMn0.4O2 mixed oxide catalysts were prepared by coprecipitation method and were characterized by N2 adsorption-desorption, TPR, XRD, and XPS techniques. The activities of the prepared catalysts for ethyl acetate combustion, and the effects of calcination temperature and space velocity on catalytic activity were investigated. The results showed that partial replacement of Mn(NO3)2 with KMnO4 as sources of manganese could improve activities of catalysts. Ce0.45Zr0.15Mn0.4O2 catalyst exhibited the best catalytic activity and high thermal stability, e.g., T90 could be still below 210 ℃ even if space velocity was up to 20000 h-1.

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Characterization and performance of Cu/ZnO/Al2O3 catalysts prepared via decomposition of M(Cu, Zn)-ammonia complexes under sub-atmospheric pressure for methanol synthesis from H2 and CO2 Danjun Wang, Jun Zhao, Huanling Song, Lingjun Chou* 2011, 20(6): 629-634.  摘要 ( 9998 )    Methanol synthesis from hydrogenation of CO2 is investigated over Cu/ZnO/Al2O3 catalysts prepared by decomposition of M(Cu, Zn)-ammonia complexes (DMAC) at various temperatures. The catalysts were characterized in detail, including X-ray diffraction, N2 adsorption-desorption, N2O chemisorption, temperature-programmed reduction and evolved gas analyses. The influences of DMAC temperature, reaction temperature and specific Cu surface area on catalytic performance are investigated. It is considered that the aurichalcite phase in the precursor plays a key role in improving the physiochemical properties and activities of the final catalysts. The catalyst from rich-aurichalcite precursor exhibits large specific Cu surface area and high space time yield of methanol (212 g/(Lcat•h);T = 513 K, p = 3 MPa, SV = 12000 h-1).

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Effect of tellurium promoter on vanadium phosphate catalyst for partial oxidation of n-butane Y. H. Taufiq-Yap*, S. Nor Asrina, G. J. Hutchings, N. F. Dummer, J. K. Bartley 2011, 20(6): 635-638.  DOI: 10.1016/S1003-9953(10)60251-4 摘要 ( 10011 )   Te-promoted (1%) vanadium phosphate catalyst (VPDTe) was prepared via VOPO4•2H2O by calcining its precursor VOHPO4•0.5H2O in a flow of n-butane/air. VPDTe catalyst has resulted a higher existence of V5+ phase with V5+/V4+ ratio of 0.23. SEM micrographs show that Te addition altered the arrangement of the platelets from ``rose-like'' clusters to layer with irregular shape. Te addition has also markedly lowered the reduction activation energies of the vanadium phosphate catalyst as revealed by TPR profile. The amount of active oxygen species associated with V4+ phase of the Te promoted catalyst was significantly higher than those of the unpromoted catalyst. These observations suggest that high mobility and availability of reactive oxygen species contributed to the enhancement of n-butane conversion up to 80% at 673 K, while only 47% over unpromoted catalyst (2400 h-1, 1.7% n-butane in air).

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Synergistic effect between Sn and K promoters on supported platinum catalyst for isobutane dehydrogenation Yiwei Zhang, Yuming Zhou*, Lihui Wan, Mengwei Xue, Yongzheng Duan, Xuan Liu 2011, 20(6): 639-646.  DOI: 10.1016/S1003-9953(10)60250-2 摘要 ( 9765 )   Catalytic dehydrogenation of isobutane has recently received considerable attention because of the increasing demand for isobutene. In this study, the synergistic effect between Sn and K on PtSnK/γ-Al2O3 catalysts has been investigated by changing the content of Sn. It was found that with the presence of potassium, suitable addition of Sn could not only increase the metal dispersion, but also reduce the catalyst acidity. In these cases, the synergistic effect could also strengthen the interactions between the metal and support, which resulted in an increase in both catalytic activity and stability. In our experiments, Pt-0.6SnK/Al catalyst exhibited the lowest deactivation rate (12.4%) and showed a selectivity to isobutene higher than 94% at the isobutane conversion of about 45.3% after running the reaction for 6 h. However, with the excessive loading of Sn, surface property of active sites and the interactions between metal and support were changed. As a result, the initial optimal ratio between the metallic function and acid function would be destroyed, which was disadvantageous to the reaction.

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Effect of temperature fluctuation on hydrate-based CO2 separation from fuel gas Xiaosen Li*, Chungang Xu, Zhaoyang Chen, Huijie Wu, Jing Cai 2011, 20(6): 647-653.  DOI: 10.1016/S1003-9953(10)60254-X 摘要 ( 9494 )   A new method of temperature fluctuation is proposed to promote the process of hydrate-based CO2 separation from fuel gas in this work according to the dual nature of CO2 solubility in hydrate forming and non-hydrate forming regions [1]. The temperature fluctuation operated in the process of hydrate formation improves the formation of gas hydrate observably. The amount of the gas consumed with temperature fluctuation is approximately 35% more than that without temperature fluctuation. It is found that only the temperature fluctuation operated in the period of forming hydrate leads to a good effect on CO2 separation. Meanwhile, with the proceeding of hydrate formation, the effect of temperature fluctuation on the gas hydrate gradually reduces, and little effect is left in the completion term. The CO2 separation efficiencies in the separation processes with the effective temperature fluctuations are improved remarkably.

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An accurate empirical correlation for predicting natural gas viscosity Ehsan Sanjari, Ebrahim Nemati Lay*, Mohammad Peymani 2011, 20(6): 654-658.  DOI: 10.1016/S1003-9953(10)60244-7 摘要 ( 10096 )   Natural gas viscosity is an important parameter in many gas and petroleum engineering calculations. This study presents a new empirical model for quickly calculating the natural gas viscosity. The model was derived from 4089 experimental viscosity data with varieties ranging from 0.01 to 21, and 1 to 3 of pseudo reduced pressure and temperature, respectively. The accuracy of this new empirical correlation has been compared with commonly used empirical models, including Lee et al., Heidaryan et al., Carr et al., and Adel Elsharkawy correlations. The comparison indicates that this new empirical model can predict viscosity of natural gas with average absolute relative deviation percentage AARD (%) of 2.173.

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Development of niobium-promoted cobalt catalysts on carbon nanotubes for Fischer-Tropsch synthesis Sardar Ali, Noor Asmawati Mohd Zabidi*, Duvvuri Subbarao 2011, 20(6): 659-663.  DOI: 10.1016/S1003-9953(10)60243-5 摘要 ( 14322 )   Cobalt-based catalysts were prepared by a wet impregnation method on carbon nanotubes (CNTs) support and promoted with niobium. Samples were characterized by nitrogen adsorption, TEM, XRD, TPR, TPO and H2-TPD. Addition of niobium increased the dispersion of cobalt but decreased the catalyst’s reducibility. Fischer-Tropsch synthesis (FTS) was carried out in a fixed-bed microreactor at 543 K, 1 atm and H2/CO = 2 for 5 h. Addition of niobium enhanced the C5+ hydrocarbons selectivity by 39% and reduced methane selectivity by 59%. These effects were more pronounced for 0.04%Nb/Co/CNTs catalyst, compared with those observed for other niobium compositions.

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Nanoporous carbons as promising novel methane adsorbents for natural gas technology Ali Morad Rashidi*, Roghaye Lotfi, Amideddin Nouralishahi, Mohammad Ali Khodagholi, Masoud Zare, Faeghe Eslamipour 2011, 20(6): 664-668.  DOI: 10.1016/S1003-9953(10)60239-3 摘要 ( 10032 )   Nanoporous carbons were synthesized using furfuryl alcohol and sucrose as precursors and MCM-41 and mordenite as nanoporous templates. The produced nanoporous carbons were used as adsorbent for methane storage. The average pore diameter of the samples varied from 3.9 nm to 5.9 nm and the BET surface area varied from 320 m2/g to 824 m2/g. The volumetric adsorption experiments revealed that MCM-41 and sucrose had better performance compared with mordenite and furfuryl alcohol, correspondingly. Also, the effect of precursor to template ratio on the structure of nanoporous carbons and their adsorption capacities was investigated. The nanoporous carbon produced from MCM-41 mesoporous molecular sieve partially filled by sucrose shows the best methane adsorption capacity among the tested samples.

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Synthesis of porous hematite nanorods loaded with CuO nanocrystals as catalysts for CO oxidation Jianliang Cao, Yan Wang, Tianyi Ma, Yuping Liu, Zhongyong Yuan* 2011, 20(6): 669-676.  DOI: 10.1016/S1003-9953(10)60238-1 摘要 ( 11518 )   Porous hematite (α-Fe2O3) nanorods with the diameter of 20--40 nm and the length of 80--300 nm were synthesized by a simple surfactant-assisted method in the presence of cetyltrimethylammonium bromide (CTAB). The α-Fe2O3 nanorods possess a mesostructure with a pore size distribution in the range of 5-12 nm and high surface area, exhibiting high catalytic activity for CO oxidation. CuO nanocrystals were loaded on the surface of porous α-Fe2O3 nanorods by a deposition-precipitation method, and the catalysts exhibited superior activity for catalytic oxidation of CO, as compared with commercial α-Fe2O3 powders supported CuO catalyst. The enhanced catalytic activity was attributed to the strong interaction between the CuO nanocrystals and the support of porous α-Fe2O3 nanorods.

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Synthesis, characterization and catalytic performance of nanosized iron-cobalt catalysts for light olefins production Mostafa Feyzi*, Asadollah Hassankhani 2011, 20(6): 677-686.  DOI: 10.1016/S1003-9953(10)60241-1 摘要 ( 11038 )   Nanosized Fe-Co catalysts were prepared by co-precipitation method and studied for the conversion of synthesis gas to light olefins. In particular, the effects of a range of preparation variables such as Co/Fe molar ratios of the precipitation solution, pH value of precipitate, temperature of precipitation, promoters and loading of optimum promoter on the structure and catalytic performance are investigated. The optimal nano catalyst for light olefins (C2–C4) production was obtained over the catalyst with Co/Fe molar ratio of 3/1 which promoted with 2 wt% K. The results show that the best operational conditions were GHSV = 2200 h-1 (H2/CO = 2/1) at 260 ℃ under atmospheric pressure. Characterization of catalysts were carried out using X-ray diffraction (XRD), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N2 physisorption measurements such as Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) methods.

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Precipitation of hematite nanoparticles via reverse microemulsion process Mohammad Reza Housaindokht1*, Ali Nakhaei Pour 2011, 20(6): 687-692.  DOI: 10.1016/S1003-9953(10)60234-4 摘要 ( 8230 )   Hematite nanoparticles have been successfully synthesized via two processing routes: (i) conventional precipitation route and (ii) reverse microemulsion route. The particle precipitation was carried out in a semibatch reactor. A microemulsion system consisting of water, chloroform, 1-butanol and surfactant was loaded with iron nitrates to form iron nanoparticles precipitation. The precipitation was performed in the single-phase microemulsion operating region. Three technical surfactants, with different structure and HLB value are employed. The influence of surfactant characterization on the size of produced iron oxide particle has been studied to gain a deeper understanding of the important controlling mechanisms in the formation of nanoparticles in a microemulsion. Transmission electron microscopy (TEM), surface area, pore volume, average pore diameter, pore size distribution and XRD were used to analyze the size, size distribution, shape and structure of precipitated iron nanoparticles.