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2009, Vol. 18, No. 1　Online: 2009-01-30

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Natural gas pyrolysis in double-walled reactor tubes using thermal plasma or concentrated solar radiation as external heating source Stephane Abanades;Stefania Tescari;Sylvain Rodat;Gilles Flamant 2009, 18(1): 1-8.  DOI: 摘要 ( 9468 )   PDF   The thermal pyrolysis of natural gas as a clean hydrogen production route is examined. The concept of a double-walled reactor tube is proposed and implemented. Preliminary experiments using an external plasma heating source are carried out to validate this concept. The results point out the efficient CH4 dissociation above 1850 K (CH4 conversion over 90%) and the key influence of the gas residence time. Simulations are performed to predict the conversion rate of CH4 at the reactor outlet, and are consistent with experimental tendencies. A solar reactor prototype featuring four independent double-walled tubes is then developed. The heat in high temperature process required for the endothermic reaction of natural gas pyrolysis is supplied by concentrated solar energy. The tubes are heated uniformly by radiation using the blackbody effect of a cavity-receiver absorbing the concentrated solar irradiation through a quartz window. The gas composition at the reactor outlet, the chemical conversion of CH4, and the yield to H2 are determined with respect to reaction temperature, inlet gas flow-rates, and feed gas composition. The longer the gas residence time, the higher the CH4 conversion and H2 yield, whereas the lower the amount of acetylene. A CH4 conversion of 99% and H2 yield of about 85% are measured at 1880 K with 30% CH4 in the feed gas (6 L/min injected and residence time of 18 ms). A temperature increase from 1870 K to 1970 K does not improve the H2 yield.

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Natural gas and biofuel as feedstock for hydrogen production on Ni catalysts Pasquale Corbo&#;Fortunato Migliardini 2009, 18(1): 9-14.  DOI: 摘要 ( 9063 )   PDF   In this article, the aptitude of natural gas as feedstock in steam reforming process for hydrogen production is compared with that of different liquid fuels (pure compounds and commercial fuels), with the aim to investigate the potentialities of biofuels to overcome the CO2 emission problems deriving from fossil fuel processing. The performances of a nickel based catalyst (commercially used in steam reforming of natural gas) were evaluated in terms of feed conversion and yield to the different products as function of temperature, space velocity and water/fuel ratio. Furthermore, a preliminary evaluation of catalyst durability was effected by monitoring yield to H2 versus time on stream and measuring coke formation at the end of experimental tests. High yields to hydrogen were obtained with all fuels investigated, whereas the deactivation phenomena, which are correlated to carbon deposition on the catalyst, were observed with all tested fuels, except for methane and biofuel.

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CO2 capture from binary mixture via forming hydrate with the help of tetra-n-butyl ammonium bromide Shifeng Li;Shuanshi Fan*;JingquWang;Xuemei Lang;Deqing Liang 2009, 18(1): 15-20.  DOI: 摘要 ( 8539 )   PDF   Hydrate formation rate and separation effect on the capture of CO2 from binary mixture via forming hydrate with 5 wt% tetra-n-butyl ammonium bromide (TBAB) solution were studied. The results showed that the induction time was 5 min, and the hydrate formation process finished in 1 h at 4.5 ◦C and 4.01 MPa. The hydrate formation rate constant reached the maximum of 1.84×10−7 mol2/(s·J) with the feed pressure of 7.30 MPa. The CO2 recovery was about 45%in the feed pressure range from 4.30 to 7.30 MPa. Under the feed pressure of 4.30 MPa, the maximum separation factor and CO2 concentration in hydrate phase were 7.3 and 38.2 mol%, respectively. The results demonstrated that TBAB accelerated hydrate formation and enriched CO2 in hydrate phase under the gentle condition.

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High selective ethylbenzene obtainment through alkylation of dilute ethene with gas phase-liquid phase benzene and transalkylation feed Shenglin Liu;Fucun Chen;Sujuan Xie;Peng Zeng;Longya Xu 2009, 18(1): 21-24.  DOI: 摘要 ( 9604 )   PDF   A novel industrial process was designed for the production of highly selective ethylbenzene. It comprised of a reactor vessel, vapor phase ethylene feed stream, benzene and transalkylation feed stream. Especially the product stream containing ethylbenzene was used to excite the reactor vessel, which consisted of an alkylation section, an upper heat exchange section, and a bottom heat exchange section. In such a novel reactor, vapor phase benzene and liquid phase benzene were maintained via the heat produced by isothermal reaction between the upper heat exchange section and the bottom heat exchange section. The process was demonstrated by the thermodynamic analysis and experimental results. In fact, during the 1010 hourlife-test of gas phase ethene with gas phase-liquid phase benzene alkylation reaction, the ethene conversion was above 95%, and the ethylbenzene selectivity was above 83% (only benzene feed) and even higher than 99% (benzene plus transalkylation feed). At the same time, the xylene content in the ethylbenzene was less than 100 ppm when the reaction conditions were as follows: 140?185 ?C of temperature, 1.6?2.1 MPa of pressure, 3.0?5.5 of benzene/ethylene mole ratio, 4?6 v% of transalkylation feed/(benzene+transalkylation feed), 0.19?0.27 h?1 of ethene space velocity, and 1000 g of 3998 catalyst loaded. Thus, compared with the normal ethylbenzene synthesis route, the transalkylation reactor could be omitted in this novel industrial process.

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Kinetic studies of the oxidative coupling of methane over the Mn/Na2WO4/SiO2 catalyst Seyed Mehdi Kamali Shahri;Seyed Mehdi Alavi 2009, 18(1): 25-34.  DOI: 摘要 ( 7732 )   PDF   Oxidative coupling of methane is a direct way to obtain C2 hydrocarbon, and Mn-Na-W/SiO2 catalyst is the most promising among all the catalysts. The 2%Mn/5%Na2WO4/SiO2 catalyst was prepared by the incipient wetness impregnation method. A 7-step heterogeneous reaction model of the oxidative coupling of methane to C2 hydrocarbons was conducted by co-feeding methane and oxygen at a total pressure of 1 bar over the catalyst. The kinetic measurements were carried out in a micro-catalytic fixed bed reactor. The kinetic data were obtained at the appropriate range of reaction conditions (4 kPa

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Preparation of novel Ni-Ir/r-Al2O3 catalyst via high-frequency cold plasma direct reduction process Liqiong Huang;Wei Chu*;Tao Zhang;Yongxiang Yin;Xumei Tao 2009, 18(1): 35-38.  DOI: 摘要 ( 7447 )   PDF   The novel Ni-Ir/γ-Al2O3 catalyst was prepared by high-frequency cold plasma direct reduction method (NIA-P) under ambient conditions without thermal treatment, and the conventional sample was prepared by impregnation, thermal calcination, and then by H2 reduction method (NIA-CR). The effects of reduction methods on catalysts for ammonia decomposition were studied, and the catalysts were characterized by XRD, N2 adsorption, XPS, and H2-TPD. It was found that the plasma-reduced NIA-P sample showed a better catalytic performance, over which ammonia conversion was 68.9%, at T = 450 ℃, P = 1 atm, and GHSV = 30, 000 h−1. It was 31.7% higher than that of the conventional NIA-CR sample. XRD results showed that the crystallite size decreased for the sample with plasma reduction, and the dispersion of active components was improved. There were more active components on the surface of the NIA-P sample from the XPS results. This effect resulted in the higher activity for decomposition of ammonia. Meanwhile, the plasma process significantly decreased the time of preparing catalyst.

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Modeling the oxidative coupling of methane: Heterogeneous chemistry coupled with 3D flow field simulation Yaghobi Nakisa*;Ghoreishy Mir Hamid Reza 2009, 18(1): 39-44.  DOI: 摘要 ( 7228 )   PDF   The oxidative coupling of methane (OCM) over titanate perovskite catalyst has been developed by three-dimensional numerical simulations of flow field coupled with heat transfer as well as heterogeneous kinetic model. The reaction was assumed to take place both in the gas phase and on the catalytic surface. Kinetic rate constants were experimentally obtained using a ten step kinetic model. The simulation results agree quite well with the data of OCM experiments, which were used to investigate the effect of temperature on the selectivity and conversion obtained in the methane oxidative coupling process. The conversion of methane linearly increased with temperature and the selectivity of C2 was practically constant in the temperature range of 973–1073 K. The study shows that CFD tools make it possible to implement the heterogeneous kinetic model even for high exothermic reaction such as OCM.

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Preparation and oxygen permeation properties of SrFe(Cu)O3 dense ceramic membranes Heng Zhang*;TingtingWang;Xinfa Dong;Weiming Lin 2009, 18(1): 45-49.  DOI: 摘要 ( 7150 )   PDF   Mixed oxygen-ionic and electronic conducting membranes of SrFe(Cu)O3−δ were prepared by solid-state reaction method. The crystal structure, oxygen nonstoichiometry, and phase stability of the materials were studied by TGA and XRD. Oxygen permeation fluxes through these membranes were studied at operating temperature ranging from 750 to 950 ℃. Results showed that doping Cu in SrFeO3−δ compound had a significant effect on the formation of single-phased perovskite structure. For SrFe1−xCuxO3−δ series materials, the oxygen nonstoichiometry and the oxygen permeation flux increased considerably with the increase of Cu-doping content (x = 0.1–0.3). The sintering property of the membrane decreased significantly when the Cu substitution amount reached 40%. SrFe0.7Cu0.3O3−δ showed high oxygen permeation flux, but SrCuO2 and Sr2Fe2O5 phases formed in the compound after oxygen permeation test induced cracks in the membrane.

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Photolysis studies on HCOOH and HCOO− in presence of TiO2 photocatalyst as suspension in aqueous medium G. R. Dey;K. N. R. Nair;K. K. Pushpa 2009, 18(1): 50-54.  DOI: 摘要 ( 7934 )   PDF   Photolysis studies on formic acid (HCOOH) and formate ion (HCOO−) in presence of TiO2, a photocatalyst, as suspension in water were carried out separately using 350 nm ultraviolet light. The products, such as H2, CO, CO2 and CH4, generated during the experiments were monitored with varying the ambient, light exposure time, and the concentration of HCOOH/HCOO−. The yields of CO in all these systems increased with light exposure time. In aerated systems, CO yields were higher in contrast to the deoxygenated (Ar-purged) systems under identical conditions. It is proposed apparently that the formation of CO is taking place during the chemical reduction of in-situ generated CO2, a photo-mineralized product of HCOOH/HCOO−, but not through the direct photodecomposition or photodehydration (CO+H2O) of solute molecules. The rates of CO formation during 1.3 M HCOOH photolysis in presence of TiO2 photocatalyst were evaluated to be 0.21 and 0.13 μl/min in aerated and Ar-purged systems, respectively. As compared with HCOOH systems, the CO yields are lower when 0.2 M HCOONa was exposed to light under identical conditions. The CO growth rates were evaluated to be 0.07 and 0.046 μl·min−1 for aerated and deoxygenated HCOONa systems, respectively; moreover, the trend is quite similar to that of the HCOOH system. Under these conditions, the emission of H2 was also observed, and its yield was significantly higher in Ar-purged system as compared with the CO yields. However, in aerated system, the yields of these products were just opposite. The formation of low yield of methane was observed during photolysis of HCOOH/HCOO− ions. In CO2 ambient, the yields of CO and H2 varied drastically with time.

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Ethanol steam reforming over Ni-Cu/Al2O3-MyOz (M=Si, La, Mg,and Zn) catalysts Lifeng Zhang;Jie Liu;Wei Li;Cuili Guo;Jinli Zhang* 2009, 18(1): 55-65.  DOI: 摘要 ( 8273 )   PDF   Ni-based catalysts doped with copper additives were studied on their role in ethanol steam reforming reaction. The effects of Cu content, support species involving Al2O3-SiO2, Al2O3-MgO, Al2O3-ZnO, and Al2O3-La2O3, on the catalytic performance were studied. Characterizations by TPR, XRD, NH3-TPD, XPS, and TGA indicated that catalysts 30Ni5Cu/Al2O3-MgO and 30Ni5Cu/Al2O3-ZnO have much higher H2 selectivity than 30Ni5Cu/Al2O3-SiO2, as well as good coke resistance. H2 selectivity for 30Ni5Cu/Al2O3-MgO catalyst was 73.3% at 450 ◦C and increased to 94.0% at 600 ◦C, whereas for 30Ni5Cu/Al2O3-ZnO catalyst, the H2 selectivity was 63.6% at 450 ◦C and 95.2% at 600 ◦C. These Al2O3-MgO and Al2O3-ZnO supported Ni-Cu bimetallic catalysts have important applications in the production of hydrogen by ethanol steam reforming reactions.

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Study on methane selective catalytic reduction of NO on Pt/Ce0.67Zr0.33O2 and its application Zhimin Liu;Kangcai Wang;Xiaoyu Zhang;Jianli Wang;Hongyan Cao;Maochu Gong;Yaoqiang Chen* 2009, 18(1): 66-70.  DOI: 摘要 ( 6821 )   PDF   Monolithic catalysts of Pt/La-Al2O3 and Pt/Ce0.67Zr0.33O2 were prepared to investigate methane selective catalytic reduction (SCR) of NO. The activity results indicate that Pt/Ce0.67Zr0.33O2 shows high activity. Both NO and CH4 can be converted completely at 450 ◦C on Pt/Ce0.67Zr0.33O2. Meanwhile, NO and CH4 can be converted completely when there exists excess oxygen. Using methane as reducing agent to SCR NO in a novel equipment which combined the CH4 selective catalytic reduction of NO with methane combustion, the catalysts were investigated. The result shows that the catalysts and the novel equipment have high activity. The conversion of NO is above 92% under the present condition. The prepared burner and catalysts have great potential for application.

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Effect of combining the metals of group VI supported on H-ZSM-5 zeolite as catalysts for non-oxidative conversion of natural gas to petrochemicals A. K. Aboul-Gheit&#;A. E. Awadallah 2009, 18(1): 71-77.  DOI: 摘要 ( 7527 )   PDF   The most prestigious catalyst applied in natural gas (methane) non-oxidative conversion to petrochemicals is 6%Mo/H-ZSM-5. Chromium, molybdenum and tungsten are the group VI metals. Hence, in this work, 6%Mo/H-ZSM-5 was correlated with 3%Cr+3%Mo/H-ZSM-5 and 3%W+3%Mo/H-ZSM-5 as catalysts to examine their promoting or inhibiting effects on the various reactions taking place during methane conversion. The catalytic activities of these catalysts were tested in a continuous flow fixed bed reactor at 700 ◦C and a GHSV of 1500 ml·g−1·h−1. Characterization of the catalysts using XRD, TGA and TPD were investigated. XRD and NH3-TPD showed greater interaction between the W-phase and the Bronsted acid sites in the channels of the zeolite than between Cr-phase and the acid sites in the zeolite.

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A DFT study on the interaction of Co with an anatase TiO2 (001)-(1×4) surface Zhijun Zuo;Wei Huang;Peide Han;Zhihong Li;Jian Huang 2009, 18(1): 78-82.  DOI: 摘要 ( 7110 )   PDF   The substitution/adsorption structures of Co on an anatase TiO2 (001)-(1×4) surface are investigated using the DFT/local density approximation (LDA) method. Theoretical calculation shows that the Co ion prefers to be adsorbed on the surface of anatase TiO2. The density of states (DOS) analysis finds that the Co 3d is located mainly in the energy gap region. The Co 3d partial density of states (PDOS) indicates that there is a substantial degree of hybridization between O 2s and Co 3d in valence band (VB) regions in the substitution models. The conclusion is that the mode of substitution is more active when the catalyst is a higher-energy surface.

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MnOx/Al2O3/Ce0.45Zr0.45M0.10Oy (M= Mn, Y, La) catalysts used for ethanol catalytic combustion Hongyan Cao;Weicong Song;Maochu Gong;Jianli Wang;Shenghui Yan;Zhimin Liu;Yaoqiang Chen* 2009, 18(1): 83-87.  DOI: 摘要 ( 8248 )   PDF   MnOx/Al2O3/Ce0.45Zr0.45M0.10Oy (M= Mn, Y, La) catalysts were prepared by impregnation method and characterized by BET, TPR and XRD analyses. The catalytic activities toward ethanol combustion were investigated in a microreactor. The results demonstrated that the catalytic activity of MnOx/Al2O3/Ce0.50Zr0.50O2 monolithic catalyst could be improved by doping Mn, Y and La into Ce0.50Zr0.50O2. When doping Y into Ce0.50Zr0.50O2, the catalyst MnOx/Al2O3/Ce0.45Zr0.45Y0.10O1.95 showed the highest activity. The 100% conversion temperature of ethanol was 230 ◦C. Furthermore, once the conversion of ethanol started, the complete conversion was quickly achieved. The doping of Mn, Y and La led to better activity for ethanol combustion and lower temperature reduction peaks in TPR profiles. The doping of Mn resulted in enhanced oxygen storage capacity (OSC), larger area of the reduction peaks, and excellent reactivity, and the doping of Y resulted in the lowest reduction temperature and the best activity.

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Dehydrogenation of n-butane over vanadia catalysts supported on silica gel Yuebing Xu;Jiangyin Lu*;Mei Zhong;Jide Wang 2009, 18(1): 88-93.  DOI: 摘要 ( 7848 )   PDF   VOx/SiO2 catalysts prepared by impregnation method were used for catalytic dehydrogenation of n-butane to butenes and characterized by x-ray diffraction, FT-IR, UV-vis, Raman, and BET measurements. The effects of VOx loading and the reaction temperature on the VOx/SiO2 catalysts and their catalytic performances for the dehydrogenation of n-butane were studied. When the VOx loading was 12% g/gcat and reaction temperature was between 590 ◦C and 600 ◦C, n-butane conversion and butenes yields reached the highest value under H2 flux of 10 ml/min and n-butane flux of 10 ml/min. Product distribution, such as the ratio of 2-butene to 1-butene and the ratio cis-2-butene to trans-2-butene, was mainly influenced by the reaction temperatures.

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Conversion of CH4, steam and O2 to syngas and hydrocarbons via dielectric barrier discharge Baowei Wang*;Xu Zhang;Yongwei Liu;Genhui XU 2009, 18(1): 94-97.  DOI: 摘要 ( 7884 )   PDF   The conversion of CH4 with oxygen and steam in a dielectric barrier discharge (DBD) was studied in the paper to discuss the effects of different factors, such as the content of feed-in gas, the applied voltage and frequency. The results showed that a lower ratio of CH4 to O2 always resulted in a higher conversion of CH4. When it was 2, the conversion reached 32.43% without steam introduced into the system. The main effect of steam was increasing the selectivity to CO. The reaction was accelerated and the selectivities to CO and hydrocarbons were enhanced by increasing the applied voltage. It was also observed that a higher frequency led to a lower current and then restrained the reaction.

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Partial oxidation of methane to syngas catalyzed by a nickel nanowire catalyst Xuebin Hong*;Yaquan Wang 2009, 18(1): 98-103.  DOI: 摘要 ( 8521 )   PDF   A nickel nanowire catalyst was prepared by a hard template method, and characterized by transmission electron microscopy (TEM), N2 physical adsorption, X-ray photoelectron spectrometry (XPS), X-ray diffraction (XRD) and H2 temperature-programmed reduction (H2-TPR). The catalytic properties of the nanowire catalyst in the partial oxidation of methane to syngas were compared with a metallic Ni catalyst which was prepared with nickel sponge. The characterization results showed that the nickel nanowire catalyst had high specific surface area and there was more NiO phase in the nickel nanowire catalyst than in the metallic Ni catalyst. The reaction results showed that the nickel nanowire catalyst had high CH4 conversion and selectivities for H2 and CO under low space velocity.

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Investigation on deactivation cause of lead-zinc double oxide for synthesis of diphenyl carbonate by transesterification Zhihui Li;Yanji Wang;Xiaoshu Ding;Xinqiang Zhao 2009, 18(1): 104-109.  DOI: 摘要 ( 8693 )   PDF   The deactivation reason of lead-zinc double oxide for synthesis of diphenyl carbonate (DPC) by transesterification of dimethyl carbonate (DMC) with phenol has been investigated. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (IR), thermogravimetry analysis (TG), atomic absorption spectroscopy and elementary analysis are employed for the catalyst characterization. Results show that, the formation of Pb4O(OC6H5)6 through the reaction of phenol and lead species in the catalyst leads to the crystal phase change of active component and serious leaching of lead, which is the reason for catalyst deactivation. In addition, the composition of the leached lead is ascertained to be a mixture of Pb4O(OC6H5)6 and PbO, and the weight percentage is 62.7% and 37.3%, respectively.

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Comparison of reduction behavior of Fe2O3, ZnO and ZnFe2O4 by TPR technique Meisheng Liang*;Wenkai Kang;Kechang Xie 2009, 18(1): 110-113.  DOI: 摘要 ( 9394 )   PDF   Advanced integrated gasification combined cycle (IGCC) power generation systems require the development of high-temperature, regenerable, desulfurization sorbents capable of removing hydrogen sulfide from coal gasifier gas to very low levels. As a sort of effective desufurizer, such as Fe2O3, ZnO and ZnFe2O4, it will endure strong reducing atmosphere in desulfurization process. The reduced degree of desufurizer can have an effect on its desulfurization reactivity. In this paper, Fe2O3, ZnO and ZnFe2O4 were synthesized by precipitation or co-precipitation at constant pH. After aging, washing and drying, the solids were calcined at 800 ◦C. The reduction behaviors of sample were characterized by temperature-programmed reduction (TPR). It is found that there are two reduction peaks for Fe2O3 in TPR, and whereas no reduction peaks for ZnO are found. The reduction process of ZnFe2O4 prepared by co-precipitation is different from that of Fe2O3. ZnFe2O4 is easier to be reduced than Fe2O3. The activation energy of reduction process for Fe2O3 and ZnFe2O4 is obtained at different reduction periods.