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2007, Vol. 16, No. 4　Online: 2007-12-30

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Reviews

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Influence of the Feed Gas Composition on the Fischer-Tropsch Synthesis in Commercial Operations Yijun Lu*;Theo Lee 2007, 16(4): 329-341.  DOI: 摘要 ( 9584 )   PDF   Key technical challenges relating to the Fischer-Tropsch (F-T) synthesis applied in the commercialization of coal/gas-to-liquids (CTL/GTL) technologies have been reviewed. Based on the experiences accumulated from pilot plant, semi-work test and lab researches, the influences of the H2/CO ratio and the CO2 in the feed gas on the F-T process as well as on CTL/GTL complex in terms of product yields, energy efficiency and carbon utilization efficiency have been studied. Being contrary to the current design schemes for F-T process using the coal derived syngas and the iron-based catalyst, it is suggested to feed the F-T synthesis unit with a syngas having a H2/CO ratio of 0.5 and then adjusting to 1.4 via the recycling process. As a result, the carbon efficiency of the whole plant could be reached to as high as 50%. For the issue of CO2 addition to the feed gas, it is proved that only a diluting role is played under the current commercial slurry phase F-T process.

Articles

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Complete Oxidation of Methane over Palladium Supported on Alumina Modified with Calcium, Lanthanum, and Cerium Ions Beata Stasinska*;Wojciech Gac;Theophilos Ioannides;Andrzej Machocki 2007, 16(4): 342-348.  DOI: 摘要 ( 9865 )   PDF   The activity and thermal stability of Pd/Al2O3 and Pd/(Al2O3+MOx) (M=Ca, La, Ce) palladium catalysts in the reaction of complete oxidation of methane are presented in this study. The catalyst supports were prepared by sol-gel method and they were dried either conventionally or with supercritical carbon dioxide. Then they were impregnated with palladium nitrate solution. The catalysts with unmodified alumina had a high surface area. The activity and thermal stability of the alumina-supported catalyst was also very high. The introduction of calcium, lanthanum, or cerium oxide into alumina support caused a decrease of the surface area in the way dependent on the support precursor drying method. These modifiers decreased the activity of palladium catalysts, and they required higher temperatures for the complete oxidation of methane than unmodified Pd/Al2O3. The improvement of the palladium activity by lanthanum and cerium support modifier was observed only at low temperatures of the reaction.

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Rapidly Estimating Natural Gas Compressibility Factor Alireza Bahadori*;Saeid Mokhatab;Brian F. Towler 2007, 16(4): 349-353.  DOI: 摘要 ( 11419 )   PDF   Natural gases containing sour components exhibit different gas compressibility factor (Z) behavior than do sweet gases. Therefore, a new accurate method should be developed to account for these differences. Several methods are available today for calculating the Z-factor from an equation of state. However, these equations are more complex than the foregoing correlations, involving a large number of parameters, which require more complicated and longer computations. The aim of this study is to develop a simplified calculation method for a rapid estimating Z-factor for sour natural gases containing as much as 90% total acid gas. In this article, two new correlations are first presented for calculating the pseudo-critical pressure and temperature of the gas mixture as a function of the gas specific gravity. Then, a simple correlation on the basis of the standard gas compressibility factor chart is introduced for a quick estimation of sweet gases' compressibility factor as a function of reduced pressure and temperature. Finally, a new corrective term related to the mole fractions of carbon dioxide and hydrogen sulfide is developed.

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Effect of Sulfate on an Iron Manganese Catalyst for Fischer-Tropsch Synthesis Tingzhen Li;Yong Yang*;Zhichao Tao;Haijun Wan;Xia An;Chenghua Zhang;Hongwei Xiang;Yongwang Li 2007, 16(4): 354-362.  DOI: 摘要 ( 9583 )   PDF   The effect of sulfate on Fischer-Tropsch synthesis performance was investigated in a slurry-phase continuously stirred tank reactor (CSTR) over a Fe-Mn catalyst. The physiochemical properties of the catalyst impregnated with different levels of sulfate were characterized by N2 physisorption, X-ray photoelectron spectroscopy (XPS), H2 (or CO) temperature-programmed reduction (TPR), M\ossbauer spectroscopy, and CO2 temperature-programmed desorption (TPD). The characterization results indicated that the impregnated sulfate slightly decreased the BET surface area and pore volume of the catalyst, suppressed the catalyst reduction and carburization in CO and syngas, and decreased the catalyst surface basicity. At the same time, the addition of small amounts of sulfate improved the activities of Fischer-Tropsch synthesis (FTS) and water gas shift (WGS), shifted the product to light hydrocarbons (C1--C11) and suppressed the formation of heavy products (C12+). Addition of SO2-4 to the catalyst improved the FTS activity at a sulfur loading of 0.05-0.80 gper100 g Fe, and S-05 catalyst gave the highest CO conversion (62.3%), and beyond this sulfur level the activity of the catalyst decreased.

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Porous Silicon Carbide/Carbon Composite Microspherules for Methane Storage Fengbo Li;Qingli Qian;Shufeng Zhang;Fang Yan;Guoqing Yuan* 2007, 16(4): 363-370.  DOI: 摘要 ( 9521 )   PDF   Porous silicon carbide/carbon (SiC/C) microspherules were prepared by the controlled heating treatment of polymer and silica hybrid precursors over 1000 ℃ in Ar/H2 stream. The resultant SiC/C composite shows improved physical properties such as excellent mechanical strength, regular physical form, and high packing density. Such improvement overcomes the main inherent problems encountered when using activated carbons as absorbents without sacrificing porosity properties. N2 sorption analysis shows that the SiC/C composite has a BET surface area of 1793 m2/g and a pore volume of 0.92 ml/g. Methane adsorption isotherm is determined by the conventional volumetric method at 25 ℃ and up to 7.0 MPa. On volumetric basis, the SiC/C composite microspherules show methane storage of 145 (V/V) at 3.5 MPa and 25 ℃. The combination of excellent physical properties and porosity properties in this SiC/C composite lends a great possibility to develop a competitive storage system for natural gas.

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Preparation, Characterization, and Catalytical Application of MgCoAl-Hydrotalcite-Like Compounds Kai Yan;Xianmei Xie*;Jinping Li;Xiulan Wang;Zhizhong Wang 2007, 16(4): 371-376.  DOI: 摘要 ( 11525 )   PDF   MgCoAl-hydrotalcite-like compounds (MgCoAl-HTLcs) were synthesized using the coprecipitation method of variable pH values. The effect of each factor on the preparation of HTLcs was discussed systematically, which included pH values, mole ratios of Mg2+ to Co2+, the concentrations of the solution, and the temperature and time of the hydrothermal treatment. Besides, the thermal decomposition of MgCoAl-HTLcs was discussed. X-ray diffraction, thermogravimetric analysis, and FT-IR spectroscopy were performed to characterize the MgCoAl-HTLcs samples. The results showed that when the pH = 7.6-8.5 or 5.5-6.2, atomic ratios of (Mg2++Co2+)/Al3+ = 2 and Mg2+/Co2+ ranging from 1.00 to 2.00, temperature and time of hydrothermal treatment being 110 ℃ and 6 h, unique MgCoAl-HTLcs with high crystallinity could be obtained. When the calcination temperature was up to 250 ℃, the MgO phase was detected coexisting with Al2O3 and MgAl2O4 was highly spreaded on the derived mixed oxides. The synthesis reaction of benzoin methyl ether with methanol and benzaldehyde was chosen to study the catalytic activity of MgCoAl-HTLcs. The catalyst showed high activity and high stability in the synthesis of benzoin methyl ether in the feasible condition.

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Effect of Several Anions on Fe-Based Catalyst for Fischer-Tropsch Synthesis Jingchang Zhang*;Xuehua Guo;Weiliang Cao 2007, 16(4): 377-381.  DOI: 摘要 ( 12417 )   PDF   The influence of several anions on Fe-based Fischer-Tropsch catalyst, used in the synthesis of light olefins from synthesis gas, was studied. The results indicated that the addition of anions resulted in the reduction of catalytic activity. When the anion content in the catalyst was 500 ppm, the influence of different anions on the catalysis activity was as follows: S2->Cl->SO2-4>NO-3. The addition of S2- improved the selectivity of total hydrocarbons in the products, and Cl- reduced this selectivity but increased the olefin content in the total hydrocarbons at the same time. When the contents of S2- and Cl- in the catalyst were less than 50 ppm, their influence could be ignored. The XRD results indicated that the addition of anions reduced the contents of α-Fe and Fe3C, which were the active components in the catalyst.

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Growth of Aligned Carbon Nanotubes on Large Scale by Methane Decomposition with Deactivation Inhibitor Hao Yu*;Zhili Li;Cheng Zhang;Feng Peng*;Hongjuan Wang 2007, 16(4): 382-388.  DOI: 摘要 ( 10232 )   PDF   The effects of additives containing iron or nickel during chemical vapor deposition (CVD) on the growth of carbon nanotubes (CNTs) by methane decomposition on Mo/MgO catalyst were investigated. Ferrocene and nickel nitrate were introduced as deactivation inhibitors by in-situ evaporation during CVD. The precisely controlled in-situ introduction of these inhibitors increased the surface renewal of catalyst, and therefore prevented the catalyst from deactivation. Using this method, aligned multi-walled CNTs with parallel mesopores can be produced on a large scale.

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Effects of ZrO2 on the Performance of CuO-ZnO-Al2O3/HZSM-5 Catalyst for Dimethyl Ether Synthesis from CO2 Hydrogenation Yanqiao Zhao;*;Jixiang Chen;Jiyan Zhang 2007, 16(4): 389-392.  DOI: 摘要 ( 11051 )   PDF   A series of composite catalysts were prepared by the wet mixing method, and the mass ratio of CuO-ZnO-Al2O3-ZrO2 component to HZSM-5 zeolite (molar ratio of SiO2 to Al2O3 being 25) was 2: 1. The CuO-ZnO-Al2O3-ZrO2 (CuO/ZnO/Al2O3=3/6/1 by weight) component was prepared by a modified `two-step' co-precipitation method. The effects of ZrO2 on the performance of CuO-ZnO-Al2O3/HZSM-5 catalyst for dimethyl ether synthesis from CO2 hydrogenation were investigated. It was found that ZrO2 improved the properties of CuO-ZnO-Al2O3/HZSM-5 as a structural promoter.

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Cumene Liquid Oxidation to Cumene Hydroperoxide over CuO Nanoparticle with Molecular Oxygen under Mild Condition Meiying Zhang*;Lefu Wang;Hongbing Ji;Bing Wu;Xiaoping Zeng 2007, 16(4): 393-398.  DOI: 摘要 ( 8942 )   PDF   CuO nanoparticle was synthesized via wet chemical method and was characterized by X-ray diffraction (XRD), nitrogen adsorption-desorption, and scanning electron microscopy (SEM). Catalytic oxidation of cumene with molecular oxygen was studied over CuO nanoparticle. The catalysts showed markedly higher activities as compared to CuO prepared by conventional method, CuO/Al2O3, or homogeneous copper catalyst under comparable reaction conditions. The cumene conversion, cumene hydroperoxide (CHP) yield, and selectivity using 0.25 g CuO nanoparticle catalyst and 0.1 mol cumene at 358 K for 7 h were 44.2%, 41.2% and 93.2%, respectively. The catalyst can be recycled. After 6 recycled experiments, no loss of catalytic activity was observed.

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Use of Electrical Resistance to Detect the Formation and Decomposition of Methane Hydrate Xitang Zhou;;Shuanshi Fan;Deqing Liang;Donglei Wang;Ningsheng Huang 2007, 16(4): 399-403.  DOI: 摘要 ( 9524 )   PDF   The changes of electrical resistance (R) were studied experimentally in the process of CH4 hydrate formation and decomposition, using temperature and pressure as the auxiliary detecting methods simultaneously. The experiment results show thatRincreases with hydrate formation and decreases with hydrate decompositon. Ris more sensitive to hydrate formation and decompositon than temperature or pressure, which indicates that the detection ofRwill be an effective means for detecting natural gas hydrate (NGH) quantitatively.

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Effect of Calcium Oxide Additive on the Performance of Iron Oxide Sorbent for High-Temperature Coal Gas Desulfurization Huiling Fan*;Kechang Xie;Ju Shangguan;Fang Shen;Chunhu Li 2007, 16(4): 404-408.  DOI: 摘要 ( 9905 )   PDF   The effect of calcium oxide additive in iron oxide sorbent for hot gas desulfurization was investigated by XRD and TPR techniques. XRD characterization showed that CaO was highly dispersed after the calcination of sorbents. Calcium sulfate formed in the desulfurization was decomposed and regenerated to CaO by reacting with CO before the next sulfidation process. Calcium participated in every sulfidation/regeneration cycle and contributed to the enhancement of sulfur capacity. The TPR results showed that the reduction temperature of the sorbent increased with the increase of the content of calcium. Calcium played a role of retarding reduction. Therefore, the addition of calcium oxide additive will benefit the utilization of iron oxide sorbent in strongly reducing atmospheres.

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Selective Oxidation of CO in Excess H2 over Ru/Al2O3 Catalysts Modified with Metal Oxide Xirong Chen;Hanbo Zou;Shengzhou Chen;Xinfa Dong*;Weiming Lin; 2007, 16(4): 409-414.  DOI: 摘要 ( 10215 )   PDF   The Ru/Al2O3 catalysts modified with metal oxide (K2O and La2O3) were preparedviaincipient wetness impregnation method from RuCl3·nH2O mixed with nitrate loading on Al2O3 support. The activity of catalysts was evaluated under simulative conditions for the preferential oxidation of CO (CO-PROX) from the hydrogen-rich gas streams produced by reforming gas, and the performances of catalysts were investigated by XRD and TPR. The results showed that the activity temperature of the modified catalysts Ru-K2O/Al2O3 and Ru-La2O3/Al2O3 were lowered approximately 30 ℃ compared with pure Ru/Al2O3, and the activity temperature range was widened. The conversion of CO on Ru-K2O/Al2O3 and Ru-La2O3/Al2O3 was above 99% at 140-160 ℃, suitable to remove CO in a hydrogen-rich gas and the selectivity of Ru-La2O3/Al2O3 was higher than that of Ru-K2O/Al2O3 in the active temperature range. Slight methanation reaction was detected at 220 ℃ and above.

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Theoretical and Experimental Study on the Adsorption and Desorption of Methane by Granular Activated Carbon at 25 ℃ E. Salehi;V. Taghikhani*;C. Ghotbi;E. Nemati Lay;A. Shojaei 2007, 16(4): 415-422.  DOI: 摘要 ( 9791 )   PDF   A theoretical and experimental study was conducted to accurately determine the amount of adsorption and desorption of methane by various Granular Activated Carbon (GAC) under different physical conditions. To carry out the experiments, the volumetric method was used up to 500 psia at constant temperature of 25 ℃. In these experiments, adsorption as well as desorption capacities of four different GAC in the adsorption of methane, the major constituent of natural gas, at various equilibrium pressures and a constant temperature were studied. Also, various adsorption isotherm models were used to model the experimental data collected from the experiments. The accuracy of the results obtained from the adsorption isotherm models was compared and the values for the regressed parameters were reported. The results shows that the physical characteristics of activated carbons such as BET surface area, micropore volume, packing density, and pore size distribution play an important role in the amount of methane to be adsorbed and desorbed.

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Interaction Study of Guest with Host in Clathrate Hydrate Lin Wang*;Shunle Dong 2007, 16(4): 423-427.  DOI: 摘要 ( 8132 )   PDF   Lattice dynamical simulations of noble gas hydrate structures I and II have been performed. Potential energies were investigated to study the influence of guest species on the stability of the hydrate structure. Results show that when the diameter of inclusion molecules is between 3\AA and 4.2\AA, such as Ar and Kr, the critical role of the 512 cage in the stabilization of hydrates becomes effective. For Xe hydrates SI and SII, with the help of lattice dynamical calculations, the modes attributions are identified directly. We proposed the resonant effect of the fingerprint frequency at about 7 meV and 10 meV which arise from the coupling of Xe molecules in the 512 cage with the host lattice.

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Theoretical Study on Ionic Liquid Based on 1-Ethyl-3-Methyl-Imidazolium Cation and Hexafluorophosphate or Tetrafluoroborate Renqing Lü;Zuogang Cao;Guoping Shen 2007, 16(4): 428-436.  DOI: 摘要 ( 10069 )   PDF   The Hartree-Fock and DFT/B3LYP methods have been employed to investigate the electronic structures of 1-ethyl-3-methyl-imidazolium cation (EMIM+), BF-4, PF-6, EMIM+-BF-4, and EMIM+-PF-6 using the Gaussian-94 soft-package at 6-31+G(d, p) basis set level for hydrogen, carbon, nitrogen, boron, phosphorus, and fluorine atoms. Comparison of the electronic structures of the lowest energy of EMIM+-BF-4 and EMIM+-PF-6 pairs, and single EMIM+, BF-4 and PF-6 showed that the optimized EMIM+-BF-4 and EMIM+-PF-6 pair conformers were BF-4 and PF-6 outside the 5-ring plane between the ethyl group and the methyl group. The cohesion of C---H…F hydrogen bond between cation and anion is reinforced by charge assistance. The interaction energy between EMIM+ and PF-6 is 328.8 kJ/mol at the B3LYP level and 326.6 kJ/mol at the Hartree-Fock level, whereas that between EMIM+ and BF-4 is 353.5 kJ/mol at the B3LYP level and 350.5 kJ/mol at the Hartree-Fock level. The low energy interactions caused by bulky asymmetric EMIM+, and charge dispersion of cation and anion give rise to the low melting point of ionic liquid EMIM+-BF-4 and EMIM+-PF-6. The two hydrogen bonding models of single hydrogen bond formation, and the hydrogen transfer between C2 in EMIM+ and F in BF-4 or PF-6 were principally depicted.

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Effect of Oxygen and Bacteria on the Property of Polymer Gel Weidong Jiang;Xiangguo Lu*;Xinxia Xu 2007, 16(4): 437-441.  DOI: 摘要 ( 8313 )   PDF   The viscosity property of Cr3+, Al3+, and compound ion cross-linked polymer gel solution in the anaerobic and aerobic environment was investigated aiming at meeting the practical demand of the oil field. The viscosity reserving effect after adding the biocide and the gelation in the anaerobic and aerobic environments was also studied in the paper. The results indicate that the viscosity of the cross-linked polymer gel solution caused by the water produced in aerobic environment is higher than that in anaerobic environment, and that the viscosity value of the cross-linked polymer gel solutions after adding biocides has improved to some extent and polymer gel has gelated well in anaerobic environment.