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2013, Vol. 22, No. 3　Online: 2013-05-20


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Prof. He and his coworkers in their article on 363–367 pages reported a free-radical initiated aerobic oxidation of alkynes to ynones in polyethylene glycol/dense CO₂/O₂ biphasic system without any catalyst or additive. In this study, dense CO₂ not only provides a safe reaction environment for oxidation, but also plays a role to improve the selectivity. The utilization of CO₂ can greatly benefit the environment and contribute to renewable clean energy.

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Communication

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Nb2O5-carbon core-shell nanocomposite as anode material for lithium ion battery Ge Li, Xiaolei Wang, Xueming Ma 2013, 22(3): 357-362.  摘要 ( 7507 )   Nb2O5-carbon nanocomposite is synthesized through a facile one-step hydrothermal reaction from sucrose as the carbon source, and studied as an anode material for high-performance lithium ion battery. The structural characterizations reveal that the nanocomposite possesses a core-shell structure with a thin layer of carbon shell homogeneously coated on the Nb2O5 nanocrystals. Such a unique structure enables the composite electrode with a long cycle life by preventing the Nb2O5 from volume change and pulverization during the charge-discharge process. In addition, the carbon shell efficiently improves the rate capability. Even at a current density of 500 mA·g-1, the composite electrode still exhibits a specific capacity of ～100 mAh·g-1. These results suggest the possibility to utilize the Nb2O5-carbon core-shell composite as a high performance anode material in the practical application of lithium ion battery.

Articles

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Polyethylene glycol radical-initiated aerobic propargylic oxidation in dense carbon dioxide Zhenfeng Diao, Bin Li, Bing Yu, Anhua Liu, Liangnian He 2013, 22(3): 363-367.  摘要 ( 7443 )   The selective aerobic oxidation of alkynes to corresponding α,β-acetylenic ketones was achieved in polyethylene glycol/dense CO2/O2 biphasic system without any catalyst or additive. The effects of reaction parameters, e.g. temperature, CO2 pressure, PEG molecular weight and loading on the reaction were carefully examined. Moreover, various substrates worked well in the presence of PEG1000 under 5 MPa of CO2 and 2 MPa of O2 at 100 ℃ for 12 to 24 h and acceptable yield and selectivity could be obtained in most cases. Preliminary mechanistic investigations were also discussed.

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Carbon dioxide conversion to valuable chemical products over composite catalytic systems Robert A. Dagle, Jianli Hu, Susanne B. Jones, Wayne Wilcox, John G. Frye, James F. White, Juyuan Jiang, Yong Wang 2013, 22(3): 368-374.  摘要 ( 8273 )   This paper reports an experimental study on catalytic conversion of carbon dioxide to methanol, ethanol and acetic acid. Catalysts having different catalytic functions were synthesized and combined in different ways to enhance the selectivity to desired products. The combined catalyst system possessed the following functions: methanol synthesis, Fischer-Tropsch synthesis, water-gas-shift and hydrogenation. Results showed that the methods of integrating these catalytic functions played an important role in achieving the desired product selectivity. We speculate that if methanol synthesis sites were located adjacent to the C-C chain growth sites, the formation rate of C2 oxygenates would be enhanced. The advantage of using a high temperature methanol catalyst PdZnAl in the combined catalyst system was demonstrated. In the presence of PdZnAl catalyst, the combined catalyst system was stable at 380 ℃. It was observed that, at high temperature, kinetics favored oxygenate formation. The results implied that the process can be intensified by operating at high temperature using Pd-based methanol synthesis catalyst. Steam reforming of the byproduct organics was demonstrated as a means to provide supplemental hydrogen. Preliminary process design, simulation, and economic analysis of the proposed CO2 conversion process were carried out. Economic analysis indicates how ethanol production cost was affected by the price of CO2 and hydrogen.

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Effect of initial precursor concentration on TiO2 thin film nanostructures prepared by PCVD system Hoang Hai Nguyen, Dong-Joo Kim, Dong-Wha Park, Kyo-Seon Kim 2013, 22(3): 375-381.  摘要 ( 6833 )   TiO2 thin film was prepared on Si substrate by plasma chemical vapor deposition (PCVD) system and the morphologies of TiO2 thin film were controlled by adjusting the initial precursor concentration. As the initial titanium tetra-isopropoxide (TTIP) concentration increases in PCVD reactor, the shapes of TiO2 particles generated in PCVD reactor change from the spherical small-sized particles around 20 nm and spherical large-sized particles around 60 nm to aggregate particles around 100 nm. The TiO2 particles with different shapes deposit on the substrate and become the main building blocks of resulting TiO2 thin film. We observed the TiO2 thin film with smooth morphology at low initial TTIP concentration, granular morphology at medium initial TTIP concentration, and columnar morphology at high initial TTIP concentration. It is proposed that we can prepare the TiO2 thin film with controlled morphologies in one-step process just by adjusting the initial precursor concentration in PCVD.

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Kinetics of hydrogen sulfide decomposition in a DBD plasma reactor operated at high temperature E. Linga Reddy, J. Karuppiah, Ch. Subrahmanyam 2013, 22(3): 382-386.  摘要 ( 6832 )   The present study investigates the kinetics of hydrogen sulfide (H2S) decomposition into hydrogen and sulfur carried out in a nonthermal plasma dielectric barrier discharge (NTP-DBD) reactor operated at ～430 K for in situ removal of sulfur condensed inside the reactor walls. The dissociation of H2S was primarily initiated by the excitation of carrier gas (Ar) through electron collisions which appeared to be the rate determining step. The experiments were carried out with initial concentration of H2S varied between 5 and 25 vol% at 150 mL/min (at standard temperature and pressure) flow rate in the input power range of 0.5 to 2 W. The reaction rate model based on continuous stirred tank reactor (CSTR) model failed to explain the global kinetics of H2S decomposition, probably due to the multiple complex reactions involved in H2S decomposition, whereas Michaelis-Menten model was satisfactory. Typical results indicated that the reaction order approached zero with increasing inlet concentration.

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Preparation of nanocrystalline Na2ZrO3 for high-temperature CO2 acceptors: chemistry and mechanism Tiejun Zhao, Magnus Rφnning, De Chen 2013, 22(3): 387-393.  摘要 ( 6175 )   Nanocrystalline Na2ZrO3 was demonstrated as a promising acceptor for CO2 capture at elevated temperatures. The mechanism of nanocrystalline Na2ZrO3 formation from the soft-chemistry route is elucidated by varying precursors, preparation methods, and calciantion temperatures, combining detailed characterizations by X-ray diffraction (XRD) and scanning electron microscope (SEM) at different steps in the process. The results revealed that the drying method such as spraying drying and simple evaporation-drying did not influence the final product properties. However both Na and Zr precursors had remarkable influences on the Na2ZrO3 formation. The solid reaction of Na intermediate and nanocrystalline ZrO2 in the calcination was identified as the key step for the Na2ZrO3 formation, where the formation of molten phase Na intermediate was found to be crucial to facilitate the solid reaction. We provided principles for rational design of the chemistry for the Na2ZrO3 formation where the formation of Na intermediate with low melting points is essential. Pure nanocrystalline Na2ZrO3 can be synthesized from a mixture containing sodium nitrate and zirconoxy citrate via the formation of NaNO3 with low melting point. However, it is not possible to form pure nanocrystalline Na2ZrO3 at relatively low temperatures from the mixtures of NaAc/ZrO(NO3)2 or NaCA/ZrOCl2 due to the formation of Na2CO3 and NaCl with high melting points.

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Regeneration of C4H10 dry reforming catalyst by nonthermal plasma Y. S. Mok, E. Jwa, Y. J. Hyun 2013, 22(3): 394-402.  摘要 ( 7017 )   Carbon deposition via coke formation is one of the critical problems causing catalyst deactivation during the reforming of hydrocarbons. An effort was made to regenerate the catalyst (Ni/γ-alumina) by oxidation methods. Two approaches were carried out for the regeneration of the deactivated catalyst. The first one involves the plasma treatment of the deactivated catalyst in the presence of dry air over a temperature range of 300～500 ℃, while the second one only the thermal treatment in the same temperature range. The performance of the regenerated catalyst was evaluated in terms of C4H10 and CO2 conversions and the physicochemical characteristics were examined using a surface area analyzer, an elemental analyzer, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was observed that the carbon deposit (coke) on the catalyst was about 9.89 wt% after reforming C4H10 for 5 h at 540 ℃. The simple thermal treatment at 400 ℃ reduced carbon content to 6.59 wt% whereas it was decreased to 3.25 wt% by the plasma and heat combination. The specific surface area was fully restored to the original state by the plasma-assisted regeneration at 500 ℃. As far as the catalytic activity is concerned, the fresh and regenerated catalysts exhibited similar C4H10 and CO2 conversion efficiencies.

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Plasma-enhanced atomic layer deposition of Co using Co(MeCp)2 precursor Jusang Park, Han-Bo-Ram Lee, Doyoung Kim, Jaehong Yoon, Clement Lansalot, Julien Gatineau, Henri Chevrel, Hyungjun Kim 2013, 22(3): 403-407.  摘要 ( 7260 )   Cobalt (Co) thermal or plasma enhanced atomic layer deposition (PE-ALD) was investigated using a novel metal organic precursor, Co(MeCp)2, and NH3 or H2 or their plasma as a reactant. The growth characteristics, electrical and microstructural properties were investigated. Especially, PE-ALD produced Co thin films at low growth temperature down to 100 ℃. Interestingly, the low temperature growth of Co films showed the formation of columnar structure at substrate temperature below 300 ℃. The growth characteristics and films properties of PE-ALD Co using bis(η-methylcyclopentadienyl) Co(II) (Co(MeCp)2) was compared with those of PE-ALD Co using other Cp based metal organic precursors, bis-cyclopentadienyl cobalt (II) (CoCp2) and cyclopentadienyl isopropyl acetamidinato-cobalt (Co(CpAMD)).

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Coronal multi-walled silicon nanotubes Yuanshuai Zhu, Zhibei Qu, Guilin Zhuang, Wulin Chen, Jianguo Wang 2013, 22(3): 408-412.  摘要 ( 6949 )   By means of first-principles density functional theory (DFT) calculations and molecular dynamics (MD) simulations, a series of coronal multi-walled silicon nanotubes (MWSiNTs) without or with hydrogen terminations are systematically identified. Notably, coronal MWSiNTs, where the interaction between the walls is preferable through covalent bonds rather than weak interaction, show better stability than CNT-like SiNTs. Moreover, they exhibit good elasticity with small Young's modulus. The investigation of the electronic structure demonstrates that they present metallic characteristics, which is in striking contrast to bulk silicon. Thus, the MWSiNTs may find important applications in electronic devices.

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Waste biomass from production process co-firing with coal in a steam boiler to reduce fossil fuel consumption: A case study Hongyan Gu, Kai Zhang, Yaodong Wang, Ye Huang, Neil Hewitt, Anthony P Roskilly 2013, 22(3): 413-419.  摘要 ( 7101 )   Waste biomass is always generated during the production process in industries. The ordinary way to get rid of the waste biomass is to send them to landfill or burn it in the open field. The waste may potentially be used for co-firing with coal to save fossil fuel consumption and also reduce net carbon emissions. In this case study, the bio-waste from a Nicotiana Tabacum (NT) pre-treatment plant is used as the biomass to co-fire with coal. The samples of NT wastes were analysed. It was found that the wastes were of the relatively high energy content which were suitable for co-firing with coal. To investigate the potential and benefits for adding NT wastes to a Fluidised Bed Combustion (FBC) boiler in the plant, detailed modelling and simulation are carried out using the European Coal Liquefaction Process Simulation and Evaluation (ECLIPSE) process simulation package. The feedstock blending ratios of NT waste to coal studied in this work are varied from 0% to 30%. The results show that the addition of NT wastes may decrease the emissions of CO2 and SOx without reducing the boiler performance.

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Plasma-assisted methane conversion in an atmospheric pressure dielectric barrier discharge reactor Chao Xu, Xin Tu 2013, 22(3): 420-425.  摘要 ( 7350 )   In this paper, a cylindrical dielectric barrier discharge (DBD) reactor has been developed for the conversion of methane into hydrogen and other valuable chemicals. The effects of a wide range of processing parameters including discharge power, residence time and frequency on the performance of plasma methane conversion reaction have been investigated. The results show that the CH4 DBD could be characterized as a typical filamentary discharge with a microdis-charge zone in each half-cycle of the applied voltage. The conversion of CH4 reaches a maximum of 25.2% at a feed flow rate of 50 mL·min-1, a discharge power of 45 W and an excitation frequency of 20 kHz. It is found that the residence time of methane in the discharge zone has the most significant effect on both methane conversion and hydrogen yield, which are significantly higher at higher residence time.

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Syngas cleaning with nano-structured micro-porous ion exchange polymers in biomass gasification using a novel downdraft gasifier Galip Akay, C. Andrea Jordan, Abdulaziz H. Mohamed 2013, 22(3): 426-435.  摘要 ( 8599 )   Sulphonated nano-structured micro-porous ion exchange polymers, known as sulphonated PolyHIPE Polymers (s-PHPs) were used in syngas cleaning to investigate their impact on tar composition, concentration and dew point depression during the gasification of fuel cane bagasse as a model biomass. The results showed that the s-PHPs used as a secondary syngas treatment system, was highly effective at adsorbing and reducing the concentration of all class of tars in syngas by 95%-80% which resulted in tar dew point depression from 90 ℃ to 73 ℃. It was shown that tars underwent chemical reactions within s-PHPs, indicating that tar diffusion from syngas was driven by chemical potential. It was also observed that s-PHPs also captured ash forming elements from syngas. The use of s-PHPs in gasification as well as in an integrated thermochemical biorefinery technology is discussed since the tar loaded s-PHPs can be used as natural herbicides in the form of soil additives to enhance the biomass growth and crop yield.

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Intrinsic properties of active sites for hydrogen production from alcohols without coke formation Zhong He, Xianqin Wang 2013, 22(3): 436-445.  摘要 ( 6680 )   The detailed reaction pathway and coke formation mechanism over Pt/metal oxide nanoparticles during the steam reforming of ethanol (SRE) at 300 ℃ were studied. The catalysts were prepared by incipient wetness impregnation method and were characterized with CO pulse chemisorption, BET surface measurement, oxygen adsorption, ethanol-TPD, NH3-TPD, and TPO. The SRE activity of the catalysts with steam/ethanol molar ratio of 3/1 was tested using a continuous fixed-bed reactor. Strong interaction between Pt and supports causes lower H2 production temperatures and no C2H4 formation, while weak interaction leads to C2H4 formation and strong bonded CO on Pt particles during ethanol-TPD. H2 production over Pt-based catalysts is mainly resulted from the decomposition and dehydrogenation of ethanol, and decarbonylation of acetaldehyde. Meanwhile, coke can be formed from acetaldehyde, acetone, C2H4 and CO. However, when the interaction between Pt and supports is weak, more coke is formed especially from acetone, C2H4 and CO. When the interaction is strong, no coke formation is observed due to high oxygen storage capacity of the catalyst.

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Methane conversion under cold plasma over Pd-containing ionic liquids immobilized on γ-Al2O3 Xiuling Zhang, Lanbo Di, Qian Zhou 2013, 22(3): 446-450.  摘要 ( 7637 )   Pd-containing ionic liquid (IL) l-hexyl-3-methylimidazolium tetrafluoroborate (C6MIMBF4) immobilized on γ-Al2O3 (Pd-IL/γ-Al2O3) was prepared and characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) analysis. The influences of C6MIMBF4 loading and Pd on methane conversion to C2 hydrocarbons under cold plasma were investigated. FTIR and SEM analyses indicated that C6MIMBF4 had been successfully immobilized on γ-Al2O3 and the C6MIMBF4 showed excellent stability under cold plasma. The results of BET and methane conversion showed that with the increase in immobilization amount of C6MIMBF4 onto γ-Al2O3, the specific surface area and pore volume of IL/γ-Al2O3 decreased, while the selectivity and yield of C2 hydrocarbons increased. The selectivity of C2 hydrocarbons was 94.6% when the loading of C6MIMBF4 was 40%, and the percentage of C2H4 in C2 hydrocarbons was as high as 64% when using Pd-IL/γ-Al2O3 as a catalyst with no conventional thermal reduction treatment. Optical emission spectra (OES) from the cold plasma reactor during methane conversion were also studied. The results indicated that the intensity of the C2, CH, H, and C active species from methane and hydrogen decomposition increased when IL/γ-Al2O3 or Pd-IL/γ-Al2O3 was introduced into the plasma system. Based on the analyses of the gas product and OES spectra, it can be concluded that the surface catalyzed reactions between plasma and ionic liquid were very important for the reduction of Pd2+ and the formation of C2H4.

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A design of experiments approach for the development of plasma synthesized Sn-silicate catalysts for the isomerization of glucose to fructose Toon Witvrouwen, Jan Dijkmans, Sabine Paulussen, Bert Sels 2013, 22(3): 451-458.  摘要 ( 6922 )   The use of non-equilibrium plasmas for the synthesis of heterogeneous catalysts is a field that has not been explored intensively. The main reasons for the recent increase of research activity in this field are related to the advantages that go with the technique of plasma enhanced chemical vapor deposition (PECVD). The most principal of these advantages are the possibility to avoid the use of environmentally harmful solvents and the one-step nature of the procedure, making it very time and labor efficient. Non-equilibrium plasma technology, more in particular dielectric barrier discharge (DBD) technology, has been applied in this work for the synthesis of hybrid tin-silicate materials to be used as a heterogeneous catalyst in the isomerization of glucose into fructose. Atomizers, innovative devices which make it possible to inject nanosized precursor liquids into the plasma zone, are used instead of applying vapor phase techniques, where the amount of precursor is limited by the vapor pressure of the liquid. A design of experiments approach has been employed to investigate the effect of the plasma parameters, namely gas flow, frequency and power density, on the catalytic properties of the catalysts within a well-defined parameter field. It has been found that indeed these parameters, together with the molar ratio of Si/Sn, have an important influence on the activity, selectivity, and thus yield of the produced chemicals.

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Effect of supercritical water on the stability and activity of alkaline carbonate catalysts in coal gasification Jinli Zhang, Xiaoxia Weng, You Han, Wei Li, Zhongxue Gan, Junjie Gu 2013, 22(3): 459-467.  摘要 ( 6939 )   The stability and activity of alkaline carbonate catalysts in supercritical water coal gasification has been investigated using density functional theory method. Our calculations present that the adsorption of Na2CO3 on coal are more stable than that of K2CO3, but the stability of Na2CO3 is strongly reduced as the cluster gets larger. In supercritical water system, the dispersion and stability of Na2CO3 catalyst on coal support is strongly improved. During coal gasification process, Na2CO3 transforms with supercritical water into NaOH and NaHCO3, which is beneficial for hydrogen production. The transformation process has been studied via thermodynamics and kinetics ways. The selectively catalytic mechanism of NaOH and the intermediate form of sodium-based catalyst in water-gas shift reaction for higher hydrogen production has also been investigated. Furthermore, NaOH can transform back to Na2CO3 after catalyzing the water-gas shift reaction. Thus, the cooperative effects between supercritical water and Na2CO3 catalyst form a benignant circle which greatly enhances the reaction rate of coal gasification and promotes the production of hydrogen.

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Coating of Al2O3 on layered Li(Mn1/3Ni1/3Co1/3)O2 using CO2 as green precipitant and their improved electrochemical performance for lithium ion batteries Yingqiang Wu, Linhai Zhuo, Jun Ming, Yancun Yu, Fengyu Zhao 2013, 22(3): 468-476.  摘要 ( 6643 )   Li(Mn1/3Ni1/3Co1/3)O2 cathode materials were fabricated by a hydroxide precursor method. Al2O3 was coated on the surface of the Li(Mn1/3Ni1/3Co1/3)O2 through a simple and effective one-step electrostatic self-assembly method. In the coating process, a NaHCO3-H2CO3 buffer was formed spontaneously when CO2 was introduced into the NaAlO2 solution. Compared with bare Li(Mn1/3Ni1/3Co1/3)O2, the surface-modified samples exhibited better cycling performance, rate capability and rate capability retention. The Al2O3-coated Li(Mn1/3Ni1/3Co1/3)O2 electrodes delivered a discharge capacity of about 115 mAh穏-1 at 2 A穏-1, but only 84 mAh穏-1 for the bare one. The capacity retention of the Al2O3-coated Li(Mn1/3Ni1/3Co1/3)O2 was 90.7% after 50 cycles, about 30% higher than that of the pristine one.

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In situ grown nanoscale platinum on carbon powder as catalyst layer in proton exchange membrane fuel cells (PEMFCs) Sheng Sui, Xiaolong Zhuo, Kaihua Su, Xianyong Yao, Junliang Zhang, Shangfeng Du, Kevin Kendall 2013, 22(3): 477-483.  摘要 ( 6296 )   An extensive study has been conducted on the proton exchange membrane fuel cells (PEMFCs) with reducing Pt loading. This is commonly achieved by developing methods to increase the utilization of the platinum in the catalyst layer of the electrodes. In this paper, a novel process of the catalyst layers was introduced and investigated. A mixture of carbon powder and Nafion solution was sprayed on the glassy carbon electrode (GCE) to form a thin carbon layer. Then Pt particles were deposited on the surface by reducing hexachloroplatinic (IV) acid hexahydrate with methanoic acid. SEM images showed a continuous Pt gradient profile among the thickness direction of the catalytic layer by the novel method. The Pt nanowires grown are in the size of 3 nm (diameter)?10 nm (length) by high solution TEM image. The novel catalyst layer was characterized by cyclic voltammetry (CV) and scanning electron microscope (SEM) as compared with commercial Pt/C black and Pt catalyst layer obtained from sputtering. The results showed that the platinum nanoparticles deposited on the carbon powder were highly utilized as they directly faced the gas diffusion layer and offered easy access to reactants (oxygen or hydrogen).

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Pathways of liquefied petroleum gas pyrolysis in hydrogen plasma: A density functional theory study Xiaoyuan Huang, Jiaming Gu, Dang-Guo Cheng, Fengqiu Chen, Xiaoli Zhan 2013, 22(3): 484-492.  摘要 ( 7260 )   A density functional theory (DFT) study has been conducted in this work to investigate the pyrolysis pathways of propane and n-butane, which are the main components of liquefied petroleum gas (LPG), for better understanding the pyrolysis behavior of LPG in hydrogen thermal plasma. Over 60 possible reactions are considered. The reaction enthalpies and activation energies of these reactions are calculated and analyzed with a Gaussian method of B3LYP and basic set of 6-31G (d,p). A most possible reaction pathway is brought up. According to this reaction pathway, the main products of LPG pyrolysis are acetylene, ethylene, methane, ethane and extra hydrogen. Acetylene mainly comes from the pyrolysis of propylene and ethylene, and hydrogen abstraction reactions are the main source of extra hydrogen gas. Active H? radicals are found to play a very important role in many reactions, and they can remarkably lower the energies needed for reactions.

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Effects of hydroxyl group on H2 dissociation on graphene: A density functional theory study Ning Wang, Likun Wang, Qinggang Tan, Yun-Xiang Pan 2013, 22(3): 493-497.  摘要 ( 8933 )   Graphene-based materials are promising for hydrogen production and storage. In this work, using density functional theory calculations, we explored how a hydroxyl group influences H2 dissociation on graphene. Presence of the hydroxyl group makes the binding of H atom with graphene stronger, as the binding energy of H atom with the hydroxyl-modified graphene is higher than that with the pristine graphene. The para-site is the most favorable site for H2 dissociation on both the pristine and hydroxyl-modified graphene. The energy barrier of H2 dissociation at para-site on the pristine graphene is 3.10 eV whereas that on the hydroxyl-modified graphene is 2.46 eV, indicating a more facile H2 dissociation on the hydroxyl-modified graphene.

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Optimization and statistical analysis of Au-ZnO/Al2O3 catalyst for CO oxidation Wenjin Yan, Xinli Jia, Tao Chen, Yanhui Yang 2013, 22(3): 498-505.  摘要 ( 7081 )   In our former work [Catal. Today 174 (2011) 127], 12 heterogeneous catalysts were screened for CO oxidation, and Au-ZnO/Al2O3 was chosen and optimized in terms of weight loadings of Au and ZnO. The present study follows on to consider the impact of process parameters (catalyst preparation and reaction conditions), in conjunction with catalyst composition (weight loadings of Au and ZnO, and the total weight of the catalyst), as the optimization of the process parameters simultaneously optimized the catalyst composition. The optimization target is the reactivity of this important reaction. These factors were first optimized using response surface methodology (RSM) with 25 experiments, to obtain the optimum: 100 mg of 1.0%Au-4.1%ZnO/Al2O3 catalyst with 220 ℃ calcination and 100 ℃ reduction. After optimization, the main effects and interactions of these five factors were studied using statistical sensitivity analysis (SA). Certain observations from SA were verified by reaction mechanism, reactivity test and/or characterization techniques, while others need further investigation.

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A zirconium modified Co/SiO2 Fischer-Tropsch catalyst prepared by dielectric-barrier discharge plasma Yunhui Jiang, Tingjun Fu, Jing Lü, Zhenhua Li 2013, 22(3): 506-511.  摘要 ( 9567 )   Co/SiO2 and zirconium promoted Co/Zr/SiO2 catalysts were prepared using dielectric-barrier discharge (DBD) plasma instead of the conventional thermal calcination method. Fischer-Tropsch Synthesis (FTS) performances of the catalyst were evaluated in a fixed bed reactor. The results indicated that the catalyst treated by DBD plasma shows the higher FTS activity and yield of heavy hydrocarbons as compared with that treated by the conventional thermal calcination method. Increase in CO conversion was unnoticeable on the Co/SiO2 catalyst, but significant on the Co/Zr/SiO2 catalyst, both prepared by DBD plasma. On the other hand, heavy hydrocarbon selectivity and chain growth probability (α value) were enhanced on all the catalysts prepared by the DBD plasma. In order to study the effect of the DBD plasma treatment on the FTS performance, the catalysts were characterized by N2-physisorption, H2-temperature programed reduction (H2-TPR), H2-temperature-programmed desorption (H2-TPD) and oxygen titration, transmission electron microscope (TEM) and X-ray diffraction (XRD). It was proved that, compared with the traditional calcination method, DBD plasma not only could shorten the precursor decomposition time, but also could achieve better cobalt dispersion, smaller Co3O4 cluster size and more uniform cobalt distribution. However, cobalt reducibility was hindered to some extent in the Co/SiO2 catalyst prepared by DBD plasma, while the zirconium additive prevented significantly the decrease in cobalt reducibility and increased cobalt dispersion as well as the FTS performance.

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Promoting effect of chloride ions on selective oxidation of methanol to methyl formate over zirconia-supported ruthenium oxide catalysts Weizhen Li, Hongpeng Zhang, Xiaohui He, Haichao Liu 2013, 22(3): 512-516.  摘要 ( 7378 )   The effect of chloride ions on a monoclinic ZrO2-supported RuOx (RuOx/m-ZrO2) catalyst with a Ru surface density of 0.3 Ru/nm2 was studied in the selective oxidation of methanol to methyl formate (MF) at a low temperature of 373 K. The m-ZrO2 support was Cl-free, and Cl- ions were introduced into the RuOx/m-ZrO2 catalyst by impregnation with zirconium oxychloride or ammonium chloride and subsequent thermal treatment in air at 673 K. The structures of these catalysts were characterized by X-ray diffraction, Raman and X-ray photoelectron spectroscopies. Their reducibility was probed by temperature-programmed reduction in H2. The RuOx domains were present as highly dispersed RuO42- structure on m-ZrO2 with similar reducibility for the RuOx/m-ZrO2 samples irrespective of modification with or without Cl- ions. Introduction of appropriate amounts of zirconium oxychloride into RuOx/m-ZrO2 led to a remarkable increase in the methanol oxidation rate and MF selectivity, whereas introduction of ammonium chloride or zirconyl nitrate significantly inhibited the catalytic performance of RuOx/m-ZrO2. The promoting effect of Cl- ions derived from zirconium oxychloride can be tentatively attributed to their roles in facilitating the adsorption of methanol and desorption of MF product or its intermediates. This finding provides novel insights into the promoting effect of Cl- ions on oxides-based catalysts for selective oxidation reactions.

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Effect of the support calcination temperature on selective hydrodesulfurization of TiO2 nanotubes supported CoMo catalysts Cuili Guo, Yuanyuan Wu, Xin Wang, Bo Yang 2013, 22(3): 517-523.  摘要 ( 6808 )   TiO2 nanotubes (TiO2-NTs) were synthesized by the hydrothermal method. Co and Mo active components were supported on a series of the as-prepared TiO2-NTs samples which were calcined at different temperatures. The effects of support calcination temperature of CoMo/TiO2-NTs catalysts on their catalytic performance were investigated for selective hydrodesulfurization (HDS). The samples were characterized by means of the scanning electron microscopy (SEM), the transmission electron microscopy (TEM), N2 adsorption-desorption, X-ray diffraction (XRD), Raman spectroscopy and H2 temperature-programmed reduction (H2-TPR). The experimental results revealed that TiO2-NTs support calcined under 500 ℃ can maintain the nanotubular structure with higher surface area and pore volume. Meanwhile, the obtained supported CoMo/TiO2-NTs catalysts exhibited weak metal-support interaction, more octahedral Mo6+ species and high catalytic performance in selective HDS.

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First-principles characterization of formate and carboxyl adsorption on stoichiometric CeO2(111) and CeO2(110) surfaces Donghai Mei 2013, 22(3): 524-532.  摘要 ( 7110 )   Molecular adsorption of formate and carboxyl on stoichiometric CeO2(111) and CeO2(110) surfaces was studied using periodic density functional theory (DFT+U) calculations. Two distinguishable adsorption modes (strong and weak) of formate are identified. The bidentate configuration is more stable than the monodentate adsorption configuration. Both formate and carboxyl bind at the more open CeO2(110) surface are stronger. The calculated vibrational frequencies of two adsorbed species are consistent with the experimental measurements. Finally, the effects of U parameters on the adsorption of formate and carboxyl over both CeO2 surfaces were investigated. We found that the geometrical configurations of two adsorbed species are not affected by different U parameters (U = 0, 5, and 7). However, the calculated adsorption energy of carboxyl pronouncedly increases with the U value while the adsorption energy of formate only slightly changes (<0.2 eV). The Bader charge analysis shows the opposite charge transfer occurs for formate and carboxyl adsorption where the adsorbed formate is negatively charge while the adsorbed carboxyl is positively charged. Interestingly, with the increasing U parameter, the amount of charge is also increased.

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Optimization strategy and procedure for coal bed methane separation Gaobo Zhang, Shuanshi Fan, Ben Hua, Yanhong Wang, Tianxu Huang, Yuhang Xie 2013, 22(3): 533-541.  摘要 ( 7015 )   Coal bed methane (CBM) has a huge potential to be purified to relieve the shortage of natural gas meanwhile to weaken the greenhouse effect. This paper proposed an optimal design strategy for CBM to obtain an integrated process configuration consisting of three each single separation units, membrane, pressure swing absorption, and cryogenics. A superstructure model was established including all possible network configurations which were solved by MINLP. The design strategy optimized the separation unit configuration and operating conditions to satisfy the target of minimum total annual process cost. An example was presented for the separation of CH4/N2 mixtures in coal bed methane (CBM) treatment. The key operation parameters were also studied and they showed the influence to process configurations.