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2007, Vol. 16, No. 1　Online: 2007-03-30

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Catalytic Conversion of Methanol by Oxidative Dehydrogenation Toshihito Ohtake;Tohru Mori;Yutaka Morikawa 2007, 16(1): 1-5.  DOI: 摘要 ( 13010 )   PDF   This study investigates the effects of addition of oxygen on the oxidative dehydrogenation (ODH) of methanol when a fluorotetrasilicic mica ion-exchanged with palladium (Pd2+-TSM) was used as the catalyst. The reaction proceeded at a very low temperature in the presence of oxygen, and HCOOCH3 was obtained at high selectivity. By calculating the equilibrium conversion, it has been shown that substan- tial ODH took place for HCOOCH3 production. Consequently, this reaction would make dehydrogenation the dominant reaction at equilibrium. Not all the H dissociated from CH3OH was converted to H2O by oxidation. It has been shown that the H2O was not produced from oxidative dehydrogenation by the direct reaction of CH3OH and O2 when an attempt was made to carry out oxidative dehydrogenation using an isotope oxygen trace method in the gas phase. Therefore, when CH3OH was converted to CO2 and dehydrogenated to HCOOCH3, the C bonds were not dissociated.

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CeO2 as the Oxygen Carrier for Partial Oxidation of Methane to Synthesis Gas in Molten Salts: Thermodynamic Analysis and Experimental Investigation Yonggang Wei;Hua Wang;Fang He;Xianquan Ao;Chiyuan Zhang 2007, 16(1): 6-11.  DOI: 摘要 ( 10906 )   PDF   A new technique the direct partial oxidation of methane to synthesis gas using lattice oxygen in molten salts medium has been introduced. Using CeO2 as the oxygen carrier, thermodynamic data were calculated in the reaction process, and the results indicated that direct partial oxidation of methane to synthesis gas using lattice oxygen of cerium oxide is feasible in theory. In a stainless steel reactor, the effects of temperature and varying amounts of γ-Al2O3 supported CeO2 on CH4 conversion, H2 and CO selectivity, were investigated, respectively. The results show that 10% CeO2/γ-Al2O3 has the maximal reaction activity at a temperature of 865 ℃ and above, the H2/CO ratio in the gas that has been produced reaches 2 and the CH4 conversion, H2 and CO selectivity reached the following percentages: i.e. 61%, 89%, and 91% at 870 ℃, respectively. In addition, increase of reaction temperature is favorable for the partial oxidation of methane.

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Study of CO2 Hydrogenation to Methanol over Cu-V/γ-Al2O3 Catalyst Yiping Zhang;Jinhua Fei;Yingmin Yu;Xiaoming Zheng 2007, 16(1): 12-15.  DOI: 摘要 ( 9445 )   PDF   The effect of vanadium addition to Cu/γ-Al2O3 catalyst used in the hydrogenation of CO2 to produce methanol was studied. It was found that the catalytic performance of the Cu-based catalyst improved after V addition. The influence of reaction temperature, space velocity and the molar ratio of H2 to CO2 on the performance of 12%Cu-6%V/γ-Al2O3 catalyst were also studied. The results indicated that the best conditions for reaction were as follows: 240 ℃, 3600 h-1 and a molar ratio of H2 to CO2 of 3:1. The results of XRD and TPR characterization demonstrated that the addition of V enhanced the dispersion of the supported CuO species, which resulted in the enhanced catalytic performance of Cu-V/γ-Al2O3 binary catalyst.

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A Numerical Approach for Multicomponent Vapor Solid Equilibrium Calculations in Gas Hydrate Formation Alireza Bahadori 2007, 16(1): 16-21.  DOI: 摘要 ( 7287 )   PDF   A new numerical approach has been developed for vapor solid equilibrium calculations and for predicting vapor solid equilibrium constant and composition of vapor and solid phases in gas hydrate formation. Equation of state methods generally do a good job of determining vapor phase properties, but for solid phase it is much more difficult and inaccurate. This proposed new model calculates vapor solid equilibrium constant and vapor and solid phase composition as a function of temperature and partial pressure. The results of this proposed numerical approach, for vapor solid equilibrium, have a good agreement with the available reported data. This new numerical model also has an advantage to tune coefficients, to cover different sets of experimental data accurately.

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Experimental and Theoretical Study of the Effect of Moisture on Methane Adsorption and Desorption by Activated Carbon at 273.5 K S. Farzad;V. Taghikhani;C. Ghotbi;B. Aminshahidi;E. Nemati Lay 2007, 16(1): 22-30.  DOI: 摘要 ( 9160 )   PDF   Adsorption and desorption of methane by activated carbon (AC) at constant temperature and at various pressures were investigated. The effect of moisture was also studied. A volumetric method was used, up to 40 bar, at a temperature of 273.5 K. Results of a dry AC sample were compared with those obtained from a moist sample and two different ACs with different physical and surface properties were used. As expected, the results showed that the existence of moisture, trapped in the AC pores, could lead to a decrease in the amount of methane adsorbed and a decrease in the amount of methane delivered during desorption. To model the experimental results, a large variety of adsorption isotherms were used. The regressed parameters for the adsorption isotherms were obtained using the experimental data generated in the present study. The accuracy of the results obtained from the different adsorption isotherms was favorably compared.

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Effect of Transition Metals (Cu, Co and Fe) on the Autothermal Reforming of Methane over Ni/Ce0.2Zr0.1Al0.7Oδ Catalyst Xinfa Dong;Xiulan Cai;Yibing Song;Weiming Lin 2007, 16(1): 31-36.  DOI: 摘要 ( 9922 )   PDF   The transition metals (Cu, Co, and Fe) were applied to modify Ni/Ce0.2Zr0.1Al0.7Oδ catalyst. The effects of transition metals on the catalytic properties of Ni/Ce0.2Zr0.1Al0.7Oδ autothermal reforming of methane were investigated. The Ni-supported catalysts were characterized by XRD, TPR and XPS. Tests in autothermal reforming of methane to hydrogen showed that the addition of transition metals (Cu and Co) significantly increased the activity of catalyst under the conditions of lower reaction temperature, and Ni/Cu0.05Ce0.2Zr0.1Al0.65Oδ was found to have the highest conversion of CH4 among all catalysts in the operation temperatures ranging from 923 K to 1023 K. TPR, XRD and XPS measurements indicated that the cubic phases of CexZr1-xO2 solid solution were formed in the preparation process of catalysts. Strong interaction was found to exist between NiO and CexZr1-xO2 solid solution. The addition of Cu improved the dispersion of NiO, inhibited the formation of NiAl2O4, and thus significantly promoted the activity of the catalyst Ni/Cu0.05Ce0.2Zr0.1Al0.65Oδ

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Toluene Alkylation to Selective Formation of p-Xylene over Co-Crystalline ZSM-12/ZSM-5 Catalyst P. N. Joshi;P. S. Niphadkar;P. A. Desai;R. Patil;V. V. Bokade 2007, 16(1): 37-41.  DOI: 摘要 ( 11897 )   PDF   The alkylation of toluene with methanol to selective formation of p-xylene has been system- atically studied. ZSM-12 (MTW)/ZSM-5 co-crystalline zeolite in 40:60 proportions have been synthesized by the same molar gel composition, but at different temperatures and periods than that of ZSM-12 and ZSM-5, separately. All the prepared samples are characterized by XRD, SEM, BET, and XRF. The activity of toluene alkylation was investigated with a mixture of toluene and methanol as a feed over the ZSM-12, ZSM-12/ZSM-5 co-crystalline, ZSM-5, and physical mixture of ZSM-12/ZSM-5. From characterization, it is observed that the ZSM-12/ZSM-5 co-crystalline material is different from that of ZSM-12, ZSM-5, and their physical mixture. Further, the ZSM-12/ZSM-5 co-crystalline zeolite produces the highest content of xylene and has better selectivity for p-xylene than ZSM-12, ZSM-5, and their physical mixture.

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Toluene Alkylation with Methanol to p-Xylene over Heteropoly Acids Supported by Clay V. V. Bokade;S. S. Deshpande;R. Patil;S. Jain;G. D. Yadav 2007, 16(1): 42-45.  DOI: 摘要 ( 9886 )   PDF   The alkylation of toluene with methanol for the selective formation of p-xylene was system- atically studied. Very few studies have been reported on the use of superacids such as heteropolyacids on cheap supports, such as clay. This article deals with the use of different heteropoly acids (HPAs), viz, Dodeca-Tungstophosphoric acid [H3PO4·12WO3·xH2O] (TPA), Dodeca-Molybdo phosphoric acid am- monium salt hydrate [H12Mo12N3O40P+aq] (DMAA), Dodeca-Molybdo Phosphoric acid (PMA) on clay (Montmorillonite, K-10) and as such plain clay. This comparative study reveals that 20%PMA/Clay shows 62% toluene conversion and 100% selectivity toward p-xylene.

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Preparation of Nano-Sized γ-Al2O3 Supported Iron Catalyst for Fischer-Tropsch Synthesis by Solvated Metal Atom Impregnation Methods Lihua Yu;Xiaoxiang Zhang;Zongjie Du;Da Wang;Shurong Wang;Shihua Wu 2007, 16(1): 46-52.  DOI: 摘要 ( 12741 )   PDF   Two types of small iron clusters supported on γ-Al2O3-RT(dehydroxylated at room temper- ature) and γ-Al2O3-800 (dehydroxylated at 800 ℃) were prepared by solvated metal atom impregnation (SMAI) techniques. The iron atom precursor complex, bis(toluene)iron(0) formed in the metal atom reac- tor, was impregnated into γ-Al2O3 having different concentrations of surface hydroxyl groups to study the effect of surface hydroxylation on the crucial stage of iron cluster formation. Catalysts prepared in this way were characterized by TEM, Moessbauer, and chemisorption measurements, and the results show that higher concentration of surface hydroxyl groups of γ-Al2O3-RT favors the formation of more positively charged supported iron cluster Fen/γ-Al2O3-RT, and the lower concentration of surface hydroxyl groups of γ-Al2O3-800 favors the formation of basically neutral supported iron cluster Fen/γ-Al2O3-800. The measured results also indicate that the higher concentration of surface hydroxyl groups causes the rapid decomposition of precursor complex, bis(toluene)iron(0), and favors the formation of relatively large iron cluster. Consequently, these two types of catalysts show different catalytic properties in Fischer-Tropsch reaction. The catalytic pattern of Fen/γ-Al2O3-RT in F-T reaction is similar to that of the unreduced α-Fe2O3 and that of Fen/γ-Al2O3-800 is similar to that of the reduced α-Fe2O3.

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Influence of Gas Components on the Formation of Carbonyl Sulfide over Water-Gas Shift Catalyst B303Q Ju Shangguan;Litong Liang;Huiling Fan;Fang Shen 2007, 16(1): 53-59.  DOI: 摘要 ( 13879 )   PDF   Water-gas shift reaction catalyst at lower temperature (200-400 ℃) may improve the con- version of carbon monoxide. But carbonyl sulfide was found to be present over the sulfided cobalt- molybdenum/alumina catalyst for water-gas shift reaction. The influences of temperature, space velocity, and gas components on the formation of carbonyl sulfide over sulfided cobalt-molybdenum/alumina cat- alyst B303Q at 200-400 ℃ were studied in a tubular fixed-bed quartz-glass reactor under simulated water-gas shift conditions. The experimental results showed that the yield of carbonyl sulfide over B303Q catalyst reached a maximum at 220 ℃ with the increase in temperature, sharply decreased with the in- crease in space velocity and the content of water vapor, increased with the increase in the content of carbon monoxide and carbon dioxide, and its yield increased and then reached a stable value with the increase in the content of hydrogen and hydrogen sulfide. The formation mechanism of carbonyl sulfide over B303Q catalyst at 200-400 ℃ was discussed on the basis of how these factors influence the formation of COS. The yield of carbonyl sulfide over B303Q catalyst at 200-400 ℃ was the combined result of two reactions, that is, COS was first produced by the reaction of carbon monoxide with hydrogen sulfide, and then the as-produced COS was converted to hydrogen sulfide and carbon dioxide by hydrolysis. The mechanism of COS formation is assumed as follows: sulfur atoms in the Co9S8-MoS2/Al2O3 crystal lattice were easily removed and formed carbonyl sulfide with CO, and then hydrogen sulfide in the water-gas shift gas reacted with the crystal lattice oxygen atoms in CoO-MoO3/Al2O3 to form Co9S8-MoS2/Al2O3. This mechanism for the formation of COS over water-gas shift catalyst B303Q is in accordance with the Mars-Van Krevelen's redox mechanism over metal sulfide.

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Partial Oxidation of Methane to Synthesis Gas over Hexaaluminates LaMAl11O19-δ Catalysts Zhanlin Xu;Lina Zhao;Fang Pang;Liang Wang;Chunyan Niu 2007, 16(1): 60-63.  DOI: 摘要 ( 8781 )   PDF   A series of M-substituted hexaaluminates LaMAl11O19-δ(M=Fe, Co, Ni, Mn, and Cu) were prepared and characterized by XRD, XPS, TPR and TGA techniques, respectively. They exhibited different reducibility and catalytic activity for partial oxidation of methane (POM) to synthesis gas. Among the LaMAl11O19-δsamples, LaMAl11O19-δ showed the best catalytic activity for the topic reaction and selectivity for synthesis gas at 780 ℃ for 2 h. The conversion of CH4 was over 99.2%, and the product selectivity for both CO and H2 was above 90.3%.

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Oligomerization and Polymerization of Ethylene Initiated by a Novel Ni(II)-Based Acetyliminopyridine Complexes as Single-Site Catalysts Baojun Zhang;Yanji Wang;Gang Wang;Jun Cao;Shukun Sun;Lihua Xing;Yongcheng Sun;Yunguang Han 2007, 16(1): 64-69.  DOI: 摘要 ( 8875 )   PDF   Novel Ni(II)-based acetyliminopyridine complexes 1b, 2b, 3b (1-3b), which are synthesized from ligands 1a, 2a, 3a (1-3a) and [NiCl2(DME)], are suitable precursors for the catalysts that are neces- sary for ethylene oligomerization and polymerization reactions, activated by methylaluminoxane (MAO). The MAO-treated 1-3b presents an active catalytic center, which may oligomerize and polymerize ethylene to produce linear α-olefins and polyethylene, respectively. The molecular weight distributions of oligomers that are obtained are in good agreement with the Schulz-Flory rules for oligomers>C4. The activity of 3b-MAO complex is 6.3E7 g/(molNi·h) at 50 ℃. The activities and molecular weight distributions of oligomers show significant reliance on the structures of catalyst precursors.

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Ab Initio Calculation of Room Temperature Ionic Liquid 1-Ethyl-3-Methyl-Imidazolium Chlorocuprate (I) Renqing Lü;Hejin Tangbo;Zuogang Cao 2007, 16(1): 70-77.  DOI: 摘要 ( 9014 )   PDF   The Hartree-Fock method has been employed to investigate the electronic structures of EMIM+(1-ethyl-3-methyl-imidazolium+), CuCl2-, Cu2Cl3-, CuCl32- , EMIM+-CuCl2-, EMIM+-Cu2Cl3-, and EMIM+-CuCl32- pairs. Full optimization and frequency analyses of EMIM+, CuCl2-, Cu2Cl3- , CuCl32-, eight initial EMIM+-CuCl2-, six EMIM+-Cu2Cl3-, and four EMIM+-CuCl32- geometries have been carried out using Gaussian-94 soft-package at 6-31+G(d,p) basis set level for hydrogen, carbon, nitrogen, chlorine atoms and Hay-Wadt effective core potential for copper atom. The electronic structures of lowest energy of EMIM+-CuCl2-, EMIM+-Cu2Cl3-, EMIM+-CuCl32- , single EMIM+, CuCl2-, Cu2Cl3-, and CuCl32- have been comparatively studied. The calculated results showed that EMIM+-CuCl2- pair conformer of lowest energy was five ring parallel to Cl-Cu-Cl with 3.2 A distance, EMIM+-CuCl32- pair conformer of lowest energy was five ring parallel to CuCl32- plane with 3.4 A distance, and the optimized EMIM+-Cu2Cl3- pair conformer of lowest energy was five ring perpendicular to Cl-Cu-Cl-Cu-Cl plane with 3.0 A distance between the terminal Cl atoms and the 5-ring of EMIM+. The cohesion between cations and anions is brought about by C-H-Cl hydrogen bonds that are reinforced by charge assistance. The frequency analyses suggested that all stationary points are minimum because of no appearing of imaginary frequency. The assigned frequencies were in agreement with the experimental report. The low energy of interaction because of the bulky asymmetry of EMIM+ and the charge dispersion of cation and anion leads to the low melting point of the ionic liquids, EMIM+-CuCl2- , EMIM+-Cu2Cl3- , and EMIM+-CuCl32- . The interac- tion energy of EMIM+-CuCl2- , EMIM+-Cu2Cl3- , and EMIM+-CuCl32- is 309.0 kJ/mol, 316.8 kJ/mol, and 320.2 kJ/mol, respectively. The relationship of interaction energy via distance between cations and anions was also investigated by single point energy scan.

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Synthesis of Methyl Glycolate by Hydrogenation of Dimethyl Oxalate over Cu-Ag/SiO2 Catalyst Baowei Wang;Qian Xu;Hua Song;Genhui Xu 2007, 16(1): 78-80.  DOI: 摘要 ( 11937 )   PDF   Methyl glycolate is a good solvent and can be used as feedstock for the synthesis of some important organic chemicals. Catalytic hydrogenation of dimethyl oxalate (DMO) over copper-silver cat- alyst supported on silica was studied. The Cu-Ag/SiO2 catalyst supported on silica sol was prepared by homogeneous deposition-precipitation of the mixture of aqueous cuprammonia complex and silica sol. The proper active temperature of Cu-Ag/SiO2 catalyst for hydrogenation of DMO was 523-623 K. The most preferable reaction conditions for methyl glycolate (MG) were optimized: temperature at 468K-478 K, 40-60 mesh catalyst diameter, H2/DMO ratio 40, and 1.0 h-1 of LHSV.

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A Study on Inhibitors for the Prevention of Hydrate Formation in Gas Transmission Pipeline Ming Wu;Shumiao Wang;Hongbo Liu 2007, 16(1): 81-85.  DOI: 摘要 ( 9979 )   PDF   Gas Hydrate is usually formed during the transportation and treatment of oil and gas, resulting in the plugging of gas pipeline and equipment. Three thermodynamic calculation formulas are analyzed to deal with this problem. The lowering of the freezing point of the inhibitors ΔT is used to calculate the formation temperature of natural gas hydrates. This is considered to be a good approach because it is not limited by what kind and what concentration of inhibitors one uses. Besides, the rate of lowering of the freezing point could be easily measured. The result of testing methanol and mono-ethylene glycol in a reactor shows that adding 10% inhibitors to the reactor can prevent the hydrates formation. Kinetic inhibitors are favored in the present research. They are divided into two types, polymer and surface-active agents. Their characteristics, mechanisms, and application prospect are separately discussed. Polymer inhibitors exhibit better efficiency. The result of field application of VC-713 inhibiter is also given in this article. In practice, the combination of thermodynamic inhibitors and kinetic inhibitors gives better result.

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Kinetic Model of Fixed Bed Reactor with Immobilized Microorganisms for Removing Low-Concentration SO2 Bing Huang;Yanyan Wang;Shiling Zhang;Yong Ao 2007, 16(1): 86-91.  DOI: 摘要 ( 9538 )   PDF   On the basis of the analysis of the process of treating low concentrations of sulfur dioxide (SO2) gas in a fixed bed reactor, a kinetic model is proposed for this process after taking into consideration the effects of internal diffusion, cell concentration, and production yield of microorganisms but ignoring the effect of external diffusion. The results obtained from the model simulation show that this model can indicate the influence of the process factors, Cin,η,μmax, Cx, A, h, Km, and Q, on the removal of SO2 and that the prediction of the results by this model is also satisfactory. This kinetic model can also provide some very important indications regarding the preparation of immobilized microorganisms, selection and domestication of proper species of microorganisms, as well as the design of bioreactors.

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Effects of Temperature and Catalyst to Oil Weight Ratio on the Catalytic Conversion of Heavy Oil to Propylene Using ZSM-5 and USY Catalysts Xiaohong Li;Chunyi Li;Jianfang Zhang;Chaohe Yang;Honghong Shan 2007, 16(1): 92-99.  DOI: 摘要 ( 10503 )   PDF   It is useful for practical operation to study the rules of production of propylene by the catalytic conversion of heavy oil in FCC (fluid catalytic cracking). The effects of temperature and C/O ratio (catalyst to oil weight ratio) on the distribution of the product and the yield of propylene were investigated on a micro reactor unit with two model catalysts, namely ZSM-5/Al2O3 and USY/Al2O3, and Fushun vacuum gas oil (VGO) was used as the feedstock. The conversion of heavy oil over ZSM-5 catalyst can be comparable to that of USY catalyst at high temperature and high C/O ratio. The rate of conversion of heavy oil using the ZSM-5 equilibrium catalyst is lower compared with the USY equilibrium catalyst under the general FCC conditions and this can be attributed to the poor steam ability of the ZSM-5 equilibrium catalyst. The difference in pore topologies of USY and ZSM-5 is the reason why the principal products for the above two catalysts is different, namely gasoline and liquid petroleum gas (LPG), repspectively. So the LPG selectivity, especially the propylene selectivity, may decline if USY is added into the FCC catalyst for maximizing the production of propylene. Increasing the C/O ratio is the most economical method for the increase of LPG yield than the increase of the temperature of the two model catalysts, because the loss of light oil is less in the former case. There is an inverse correlation between HTC (hydrogen transfer coefficient) and the yield of propylene, and restricting the hydrogen transfer reaction is the more important measure in increasing the yield of propylene of the ZSM-5 catalyst. The ethylene yield of ZSM-5/Al2O3 is higher, but the gaseous side products with low value are not enhanced when ZSM-5 catalyst is used. Moreover, for LPG and the end products, dry gas and coke, their ranges of reaction conditions to which their yields are dependent are different, and that of end products is more severe than that of LPG. So it is clear that maximizing LPG and propylene and restricting dry gas and coke can be both achieved via increasing the severity of reaction conditions among the range of reaction conditions which LPG yield is sensitive to.

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Preparation and Characterization of Nano-ZnFe2O4/TiO2 Films Kejing Xu 2007, 16(1): 100-105.  DOI: 摘要 ( 9829 )   PDF   The nano-ZnFe2O4/TiO2 films possess the functions of desulfurization and degradation for organic pollutants. The sols of ZnFe2O4/TiO2 were prepared by sol-gel method and coated on glass and porous ceramic by vertical coating and dipping-lift processes, respectively, and the samples were obtained after drying and sintering. The composition, appearance, absorption spectrum of the films, and the influence of the film on porous ceramic performances were analyzed using SEM, AFM, UV- Vis spectrometer, and mercury porosimeter, respectively, to determine the operation parameters of the multifunction porous ceramic elements for gas-purification.