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2011, Vol. 20, No. 2　Online: 2011-03-21

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Influence of reduction energy match among CuO species in CuO-CeO2 catalysts on the catalytic performance for preferential oxidation of CO in excess hydrogen Zhigang Liu, Yunlong Xie, Wensheng Li, Renxian Zhou*, Xiaoming Zheng 2011, 20(2): 111-116.  DOI: 10.1016/S1003-9953(10)60170-3 摘要 ( 9765 )   Although there are many studies focused on the synergistic effect between CuO and CeO2, the cooperation among CuO species has received relatively less attention. In the present study, we have investigated the reducibility of CuO species on CuO-CeO2 catalysts and the influence of CuO species on the catalytic performance for preferential oxidation of CO (PROX) in excess hydrogen. It is revealed that the smaller the difference of reduction temperature (denoted as ?T) for two adjacent CuO species is, the higher the catalytic activity of CuO-CeO2 for the PROX in excess hydrogen may be obtained. That is, the reduction energy of Cu0-Cu2+ pairs matched better, and the reduction-oxidation recycle of Cu0-Cu2+ pairs went on more easily, then the transferring energy of Cu0-Cu2+ pairs would be lowered more. Therefore, the CuO-CeO2 catalysts will be largely improved their catalytic performance if the different CuO species on the catalysts have matched the reduction energy, which would allows them to cooperate effectively.

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Synthesis of Ni2P promoted trimetallic NiMoW/γ-Al2O3 catalysts for diesel oil hydrotreatment Ling Lan*, Shaohui Ge, Kunhong Liu, Yuandong Hou, Xiaojun Bao* 2011, 20(2): 117-122.  DOI: 10.1016/S1003-9953(10)60173-9 摘要 ( 9722 )   The Ni2P promoted and γ-Al2O3 supported NiMoW sulfide catalyst consisting of 4 wt% Mo, 22 wt% W, 2 wt% Ni and 2.5 wt% Ni2P was synthesized by a co-impregnation method. The catalysts were characterized by N2 adsorption-desorption, X-ray diffraction (XRD), diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, NH3 temperature-programmed desorption (NH3-TPD) and transmission electron microscopy (TEM). The results showed that Ni2P, Ni, Mo and W species were highly dispersed over the supports. The hydrodesulfurization (HDS) of dibenzothiophene (DBT) showed that the presence of Ni2P brought a strong promotional effect, which was confirmed by the HDS and hydrodenitrogenation (HDN) of diesel oil under industrial conditions. The enhancement in HDN activity and stability by Ni2P addition could be attributed more to the effect of new active sites of Ni2P than that of acidity. The as-prepared Ni2P-NiMoW/γ-Al2O3 catalyst showed better hydrotreating performance than NiMoW/γ-Al2O3 and commercial catalysts.

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Pd-gate MOS sensor for detection of methanol and propanol Preeti Pandey*, J. K. Srivastava, V. N. Mishra, R. Dwivedi 2011, 20(2): 123-127.  DOI: 10.1016/S1003-9953(10)60165-X 摘要 ( 10811 )   The present paper focused on the detection of methanol and propanol using Pd-gate metal-oxide-semiconductor (MOS) sensor. Surface morphology and composition of the gate film were studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The response of the sensor for propanol and methanol was measured as shift in capacitance-voltage (C-V) and conductance-voltage (G-V) curves of the MOS structure. The sensitivity of the sensor towards methanol was found to be greater than that towards propanol. It was 58.2% for methanol and 32% for propanol (at 0.6 V, 1 MHz) in terms of capacitance measurements, while in terms of conductance results the sensitivity was found to be 57.2% for methanol and 38.9% for propanol at 1 kHz. The discontinuities or cracks present in the microstructure of the gate material are believed to be mainly responsible for the high sensitivity of the sensor, going with the decomposition of gas molecules and subsequent hydrogen permeation through Pd.

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Synthesis of nanocrystalline γ-Al2O3 by sol-gel and precipitation methods for methanol dehydration to dimethyl ether Zahra Hosseini, Majid Taghizadeh*, Fereydoon Yaripour 2011, 20(2): 128-134.  DOI: 10.1016/S1003-9953(10)60172-7 摘要 ( 13694 )   The capability of sol-gel and conventional precipitation techniques for the synthesis of nanocrystalline γ-alumina was investigated. These catalysts were used for vapor-phase dehydration of methanol to dimethyl ether in a fixed-bed reactor under the same operating conditions (T = 300 ℃, P = 1 bar, LHSV = 2.8, 11.7, 26.1 h-1) and characterized by means of N2 adsorption-desorption, NH3-TPD, XRD, TGA and SEM techniques. According to the experimental results, the catalysts prepared using sol-gel method in non-aqueous medium showed better performance compared to those prepared by other methods.

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Additive effects of alkaline-earth metals and nickel on the performance of Co/γ-Al2O3 in methane catalytic partial oxidation Changlin Yu*, Weizheng Weng, Qing Shu, Xiangjie Meng, Bin Zhang, Xirong Chen, Xiaochun Zhou 2011, 20(2): 135-139.  DOI: 10.1016/S1003-9953(10)60175-2 摘要 ( 11900 )   Nano-sized γ-alumina (γ-Al2O3) was first prepared by a precipitation method. Then, active component of cobalt and a series of alkaline-earth metal promoters or nickel (Ni) with different contents were loaded on the γ-Al2O3 support. The catalysts were characterized by N2 adsorption-desorption, X-ray diffraction (XRD) and thermogravimetry analysis (TGA). The activity and selectivity of the catalysts in catalytic partial oxidation (CPO) of methane have been compared with Co/γ-Al2O3, and it is found that the catalytic activity, selectivity, and stability are enhanced by the addition of alkaline-earth metals and nickel. The optimal loadings of strontium (Sr) and Ni were 6 and 4 wt%, respectively. This finding will be helpful in designing the trimetallic Co-Ni-Sr/γ-Al2O3 catalysts with high performance in CPO of methane.

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Relation between soil matrix potential changes and water conversion ratios during methane hydrate formation processes in loess Peng Zhang*, Qingbai Wu, Guanli Jiang, Yibin Pu 2011, 20(2): 140-144.  DOI: 10.1016/S1003-9953(10)60174-0 摘要 ( 10461 )   With a new apparatus designed and assembled by ourselves, the matrix potential of non-saturated loess was firstly measured and studied during methane hydrate formation processes. The experimental results showed that during two formation processes, the matrix potential changes of the loess all presented a good linear relationship with water conversion ratios. In addition, although it was well known that the secondary gas hydrate formation was easier than the initial, our experimental results showed that the initial hydrate formation efficiency in non-saturated loess was higher than that of the secondary.

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Photocatalytic reduction of carbon dioxide to methanol by Cu2O/SiC nanocrystallite under visible light irradiation Huiling Li, Yonggen Lei, Ying Huang, Yueping Fang, Yuehua Xu, Li Zhu, Xin Li* 2011, 20(2): 145-150.  DOI: 10.1016/S1003-9953(10)60166-1 摘要 ( 11986 )   The Cu2O/SiC photocatalyst was obtained from SiC nanoparticles (NPs) modified by Cu2O. Their photocatalytic activities for reducing CO2 to CH3OH under visible light irradiation have been investigated. The results indicated that besides a small quantity of 6H-SiC, SiC NPs mainly consisted of 3C-SiC. The band gaps of SiC and Cu2O were estimated to be about 1.95 and 2.23 eV from UV-Vis spectra, respectively. The Cu2O modification can enhance the photocatalytic performance of SiC NPs, and the largest yields of methanol on SiC, Cu2O and Cu2O/SiC photocatalysts under visible light irradiation were 153, 104 and 191μmol/g, respectively.

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Hydrogen generation from steam reforming of ethanol in dielectric barrier discharge Baowei Wang*, Yijun Lü, Xu Zhang, Shuanghui Hu 2011, 20(2): 151-154.  DOI: 10.1016/S1003-9953(10)60160-0 摘要 ( 10929 )   Dielectric barrier discharge (DBD) was used for the generation of hydrogen from ethanol reforming. Effects of reaction conditions, such as vaporization temperature, ethanol flow rate, water/ethanol ratio, and addition of oxygen, on the ethanol conversion and hydrogen yield, were studied. The results showed that the increase of ethanol flow rate decreased ethanol conversion and hydrogen yield, and high water/ethanol ratio and addition of oxygen were advantageous. Ethanol conversion and hydrogen yield increased up to the maximum at first and then decreased slightly with increase of the vaporization temperature. The maximum of 88.4% for ethanol conversion with hydrogen yield for 31.8% was obtained at the optimum operation conditions as vaporization room temperature of 120 ℃, ethanol flux of 0.18 mL/min, water/ethanol ratio of 7.7, oxygen volume concentration of 13.3%, respectively.

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Adsorption and dissociation of H2O on Cu2O(100): A computational study Yun Li, Lifen Yan, Guichang Wang* 2011, 20(2): 155-161.  DOI: 10.1016/S1003-9953(10)60162-4 摘要 ( 11684 )   The adsorption and dissociation of water on Cu2O(100) have been investigated by the density functional theory-generalized gradient approximation (DFT-GGA) method. The corresponding reaction energies, the structures of the transition states and the activation energies were determined. Calculations with and without dipole correction were both studied to get an understanding of the effect of the dipole moment on the adsorption and reaction of water on dipole surface Cu2O(100). When dipole correction was added, the adsorption energies of H2O on different sites generally decreased. The calculated activation barriers for HxO (x = 1, 2) dehydrogenation are 0.42 eV (1.01 eV without the dipole correction) and 1.86 eV, respectively, including the zero point energy correction. The first dehydrogenation outcome is energetically the most stable product.

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Effects of P content in a P/HZSM-5 catalyst on the conversion of ethanol to hydrocarbons Jiangyin Lu*, Yancong Liu 2011, 20(2): 162-166.  DOI: 10.1016/S1003-9953(10)60163-6 摘要 ( 11732 )   A series of P/HZSM-5 catalysts prepared by impregnation method were used for ethanol conversion to lower olefins. The catalysts were characterized by X-ray diffraction (XRD), NH3-temperature-programmed desorption (NH3-TPD) and N2 adsorption-desorption measurements. It was found that the P/HZSM-5 catalysts showed high activity and selectivity toward light olefins. The selectivities of propylene and butylene can be improved with the introduction of phosphorus (P). When the content of P reached 3.0 wt%, more than 18.9% propylene in the gaseous products was obtained over the P/HZSM-5 catalyst at 450 ℃. The introduction of P tempered the strong Brønsted acid sites of the original HZSM-5 catalysts. P/HZSM-5 catalysts resisted coke formation and kept good stability.

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Simultaneous removal of ethanol, acetaldehyde and nitrogen oxides over V-Pd/γ-Al2O3-TiO2 catalyst Zhe Li*, Jing Wang, Kai He, Xia An, Wei Huang, Kechang Xie 2011, 20(2): 167-172.  DOI: 10.1016/S1003-9953(10)60159-4 摘要 ( 9881 )   V-Pd/γ-Al2O3-TiO2 catalysts with different vanadium contents were prepared by a combined sol-gel and impregnation method. X-ray diffraction (XRD), N2 adsorption-desorption (BET), X-ray photoelectron spectroscopy (XPS) and catalytic removal of ethanol, acetaldehyde and nitrogen oxides at low temperature (<300 ℃) were used to assess the properties of the catalysts. The results showed that the sample with 1wt% vanadium exhibited an excellent catalytic performance for simultaneous removal of ethanol, acetaldehyde and nitrogen oxides. The conversions of ethanol, acetaldehyde and nitrogen oxides at 250 ℃ were 100%, 74.4% and 98.7%, respectively. V-Pd/γ-Al2O3-TiO2 catalyst with 1 wt% vanadium showed the largest surface area and higher dispersion of vanadium oxide on the surface of catalyst, and possessed a larger mole fraction of V4+ species and unique PdO species on the surface, which can be attributed to the strong synergistic effect among palladium, vanadium and the carriers. The higher activity of V-Pd/γ-Al2O3-TiO2 catalyst is related to the V4+ and Pd2+ species on the surface, which might be favorable for the formation of active sites.

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DFT study on the selective oxidation of vinyl chloride on different metal surfaces Ruipeng Ren, Ruixin Xi, Xianyong Pang, Yongkang Lü* 2011, 20(2): 173-178.  DOI: 10.1016/S1003-9953(10)60164-8 摘要 ( 8878 )    Selective epoxidation of vinyl chloride Ag(111), Pt(111) and Rh(111) with pre-adsorbed atomic oxygen has been studied by density functional theory (DFT) calculation with the periodic slab model. The reaction energies and activation energies of the epoxidation reaction are determined. Because of the asymmetry of vinyl chloride three competitive reaction pathways are investigated. The results indicate that the most possible reaction pathway is pathway III. Compared the activation energies of the epoxidation reaction on Ag(111), Pt(111) and Rh(111), it is obvious that the reaction via OMMC(3) on Ag(111) is the most possible process. However, the selectivity to the target product over Ag(111) is the lowest among the three metals. The results also indicate that the formation of chloroacetaldehyde is more favorable than that of chloroepoxide.

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Structural and micro structural studies of PbO-doped SnO2 sensor for detection of methanol, propanol and acetone J. K. Srivastava?, Preeti Pandey, V. N. Mishra, R. Dwivedi 2011, 20(2): 179-183.  DOI: 10.1016/S1003-9953(10)60168-5 摘要 ( 11908 )   In the present work the structural information of PbO-doped SnO2 thick film sensor has been investigated with X-ray diffractometer (XRD) and Scanning Electron Microscope (SEM). Initially, SnO2 powder was derived using sol-gel process and was subsequently doped with PbO and ground up to nanosized particles. A suitable gas sensor structure was fabricated on 1′ ′×1′ ′ alumina substrate using thick film technology. The necessary paste for screen printing was also developed. SEM results showed sol-gel derived powder gets more agglomerated in the thick film form. The sensitivity of the sensor has been investigated at different temperatures (150 ?C−350 ?C) upon exposure to methanol, propanol and acetone, yielding a maximum at 250 ?C for acetone with 1 wt% PbO-doping while at 350 ?C for propanol with 3 wt% PbO-doping of the sensor. The reduction of particle size to nanometers (validated through XRD) leads to a dramatic improvement in sensitivity of sensors for the chosen organic vapors. The results also correlate well with the microstructural properties of the material and the dopant.

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Carbon dioxide reforming of methane on monolithic Ni/Al2O3-based catalysts S. O. Soloviev*, A. Yu. Kapran, S. N. Orlyk, E. V. Gubareni 2011, 20(2): 184-190.  DOI: 10.1016/S1003-9953(10)60149-1 摘要 ( 13751 )   Nickel-alumina catalysts supported on cordierite monoliths of honeycomb structure surpass essentially the conventional granulated ones with respect to the output in carbon dioxide reforming of methane. Adjusting the surface acid-base properties of catalysts by introduction of alkali metal (Na, K) oxides inhibits the carbonization and as a result, improves the operational stability of these catalysts. An effect of promotion of nickel-alumina based composite doped by lanthanum oxide is found. This effect, caused by an additional route for the CO2 activation on Ni-La2O3/Al2O3/cordierite catalyst, is displayed in increase of methane conversion under conditions of an oxidant excess.

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Preparation and characterization of Mn/MgAlFe as transfer catalyst for SOx abatement Ruiyu Jiang, Honghong Shan, Chunyi Li*, Chaohe Yang 2011, 20(2): 191-197.  DOI: 10.1016/S1003-9953(10)60171-5 摘要 ( 10842 )   A series of manganese-promoted MgAlFe mixed oxides, used as sulfur transfer catalysts, were prepared by acid-processed gelatin method and characterized by TGA-DTA, XRD, N2 adsorption-desorption, and FT-IR techniques. It was found that the sulfur transfer catalysts with 0.5-3.0 wt% manganese showed a good dispersion of manganese in the precursor. The novel Mn/MgAlFe catalysts with 0.5-5.0 wt% manganese oxide showed a high oxidative adsorption rate and sulfur adsorption capacity, and 5.0 wt% Mn/MgAlFe sample was superior to the others for SO2 removal. Moreover, the presence of CO had no obvious effect on the adsorption activity of sulfur transfer catalysts for SO2 uptake.

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Ni catalysts supported on nanocrystalline magnesium oxide for syngas production by CO2 reforming of CH4 Fereshteh Meshkani, Mehran Rezaei* 2011, 20(2): 198-203.  DOI: 10.1016/S1003-9953(10)60169-7 摘要 ( 11147 )   CO2 reforming of methane (CDRM) was carried out over MgO supported Ni catalysts with various Ni loadings. The preparation of MgO supported Ni catalysts via surfactant-assisted precipitation method led to the formation of a nanocrystalline carrier for nickel catalysts. The synthesized samples were characterized by XRD, N2 adsorption-desorption, H2 chemisorption, TPR, TPO and SEM techniques. It was found that the high catalytic activity and stability of the prepared catalysts could be attributable to high dispersion of reduced Ni species and basicity of support surface. In addition, the effect of feed ratio, nickel loading and GHSV on the catalytic performance of CDRM over the catalysts were investigated.

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Effects of operating parameters on oxidative coupling of methane over Na-W-Mn/SiO2 catalyst at elevated pressures Jafar Sadeghzadeh Ahari, Mohammad Taghi Sadeghi*, Saeed Zarrinpashne 2011, 20(2): 204-213.  DOI: 10.1016/S1003-9953(10)60167-3 摘要 ( 9625 )   The effects of operating parameters on oxidative coupling of methane (OCM) over Na-W-Mn/SiO2 catalyst have been studied at elevated pressures of 0.2, 0.3 and 0.4 MPa under low gaseous hourly space velocity (GHSV) and low temperature conditions. Experimental results show that when the operating pressure is increased, C2+ yield slightly decreases, while the maximum ratio of ethylene to ethane remains unchanged. Moreover, it has been found empirically that increase of pressure does not affect the catalyst behavior permanently, the catalyst recovers its original low pressure performance without hysteresis behavior by reducing the pressure. Under the investigated conditions, when oxygen is completely consumed, the increase of GHSV leads to improvement in C2 selectivity, while C3+ and COx selectivities decrease slightly. The C2+ selectivity increases by increase of nitrogen diluent in the feed, but the C3+ hydrocarbons selectivities decrease with increase of nitrogen since it is possible that further dilution at high pressure may reduce the probability of collision between CH3 and C2+ hydrocarbons. During the stability test at high pressure, the catalyst performance remains unchanged throughout the 20 h running. The fresh and used catalysts were characterized using XRD, SEM and BET methods. It was found that the phase transformation of the support from α-cristobalite to tridymite and quartz does not have obvious effect on catalyst performance at high pressure.

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Synergetic effect between sulfurized Mo/γ-Al2O3 and Ni/γ-Al2O3 catalysts in hydrodenitrogenation of quinoline Lihua Liu, Bin Liu, Yongming Chai, Yunqi Liu, Chenguang Liu* 2011, 20(2): 214-217.  DOI: 10.1016/S1003-9953(10)60177-6 摘要 ( 9873 )   An evidence for the synergetic effect between the stacked bed of Mo/γ-Al2O3 and Ni/γ-Al2O3 in the hydrodenitrogenation (HDN) reaction of quinoline has been provided in this paper. The synergism factor decreases when the reaction temperature increases (280-340 ℃). The synergetic effect leads to improve the hydrogenation activity for the stacked bed compared with the single Mo/γ-Al2O3 bed, which may be attributed to the generation of hydrogen spillover over the Ni/γ-Al2O3 catalyst.