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2009, Vol. 18, No. 4　Online: 2009-05-21

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Size control synthesis of sulfur doped titanium dioxide (anatase) nanoparticles, its optical property and its photo catalytic reactivity for CO2 + H2O conversion and phenol degradation S. Tajammul Hussain*;Khaiber Khan;R. Hussain 2009, 18(4): 383-391.  DOI: 摘要 ( 9955 )   PDF   Sulfur doped anatase TiO2 nanoparticles (3 nm−12 nm) were synthesized by the reaction of titanium tetrachloride, water and sulfuric acid with addition of 3M NaOH at room temperature. The electro-optical and photocatalytic properties of the synthesized sulfur doped TiO2 nanoparticles were studied along with Degussa commercial TiO2 particles (24 nm). The results show that band gap of TiO2 particles decreases from 3.31 to 3.25 eV and for that of commercial TiO2 to 3.2 eV when the particle sizes increased from 3 nm to 12 nm with increase in sulfur doping. The results of the photocatalytic activity under UV and sun radiation show maximum phenol conversion at the particle size of 4 nm at 4.80% S-doping. Similar results are obtained using UV energy for both phenol conversion and conversion of CO2+H2O in which formation of methanol, ethanol and proponal is observed. Production of methanol is also achieved on samples with a particle size of 8 and 12 nm and sulfur doping of 4.80% and 5.26%. For TiO2 particle of 4 nm without S doping, the production of methanol, ethanol and proponal was lower as compared to the S-doped particles. This is attributed to the combined electronic effect and band gap change, S dopant, specific surface area and the light source used.

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Effect of Cu promoter on Ni-based SBA-15 catalysts for partial oxidation of methane to syngas Fabien Habimana;Xiujin Li;Shengfu Ji*;Bao Lang;Daoan Sun;Chengyue Li 2009, 18(4): 392-398.  DOI: 摘要 ( 9408 )   PDF   A series of Ni/SBA-15 catalysts with 5wt% to 15wt% Ni content as well as a series of 12.5%Ni/Cu/SBA-15 catalysts with 1% to 10% copper content were prepared by the impregnation method. The catalytic performance for partial oxidation of methane was investigated in a continuous flow microreactor under atmospheric pressure. The textural and chemical properties of the catalysts were characterized by XRD, TEM, BET and H2-TPR techniques. The results indicated that the catalysts modified with Cu promoter showed better performance than those without modification. For the 12.5%Ni/2.5%/Cu/SBA-15 catalyst, at 850 ◦C the conversion of CH4 reached 97.9% and the selectivity of CO and H2 reached 98.0% and 96.0%, respectively. In XRD patterns of the Ni/Cu/SBA-15 catalyst with 7.5 to 10% Cu contents there were CuO characteristic peaks beside NiO characteristic peaks. The mesoporous structure of SBA-15 was retained in all of the catalysts. TPR analysis of the catalysts revealed that a strong interaction between Ni, Cu promoter and SBA-15 support may be existed. This interaction enhanced significantly the redox properties of the catalysts resulting in the higher catalytic activity.

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Catalytic perfomance of rhodium chalcogen halides and rhodium chalcogenides over silica supports in methane oxidative carbonylation S. V. Volkov;G. R. Kosmambetova*;L. B. Kharkova;O. V. Shvets;O. G. Yanko;V. I. Gritsenko;P. E. Strizhak 2009, 18(4): 399-406.  DOI: 摘要 ( 8040 )   PDF   The gas phase methane oxidative carbonylation was studied in the presence of molecular oxygen over silica materials including their mechanical mixtures with rhodium chalcogen chlorides obtained in non-aqueous inorganic media. The formation of Rh4SCl7, Rh4S9Cl2, Rh4Se5Cl3 and Rh3Se3Cl solids was confirmed by elemental analysis, IR absorption spectroscopy, XPS and X-ray diffraction. Silica, vanadium-, and molybdenum-containing mesoporous molecular sieves have been used as supports. It was found that productivity of oxygenates (methanol, methyl acetate and acetic acid) depends mainly on the method of the catalyst preparation and the type of the support.

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Hydrogen production from coke oven gas over LiNi/r-Al2O3 catalyst modified by rare earth metal oxide in a membrane reactor Zhibin Yang;Yunyan Zhang;Weizhong Ding*;Yuwen Zhang;Peijun Shen;Yuding Zhou;Yong Liu;Shaoqing Huang;Xionggang Lu 2009, 18(4): 407-414.  DOI: 摘要 ( 8459 )   PDF   The performance of LiNi/r-Al2O3 catalysts modified by rare earth metal oxide (La2O3 or CeO2) packed on BCFNO membrane reactor was discussed for the partial oxidation of methane (POM) in coke oven gas (COG) at 875 ◦C. The NiO/r-Al2O3 catalysts with different amounts of La2O3 and CeO2 were prepared with the same preparation method and under the same condition in order to compare the reaction performance (oxygen permeation, CH4 conversion, H2 and CO selectivity) on the membrane reactor. The results show that the oxygen permeation flux increased significantly with LiNiREOx/r-Al2O3 (RE = La or Ce) catalysts by adding the element of rare earth especially the Ce during the POM in COG. Such as, the Li15wt%CeO29wt%NiO/ -Al2O3 catalyst with an oxygen permeation flux of 24.71 ml·cm−2·min−1 and a high CH4 conversion was obtained in 875 ◦C. The resulted high oxygen permeation flux may be due to the added Ce that inhibited the strong interaction between Ni and Al2O3 to form the NiAl2O4 phase. In addition, the introduction of Ce leads up to an important property of storing and releasing oxygen.

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Influence of CeO2 and La2O3 on properties of palladium catalysts used for emission control of natural gas vehicles Yile Li;Xiaoyu Zhang;Enyan Long;Hongmei Li;Dongdong Wu;Li Cai;Maochu Gong;Yaoqiang Chen 2009, 18(4): 415-420.  DOI: 摘要 ( 8294 )   PDF   Pd/YZ-Al2O3 (Y and Zr modified Al2O3, and hereafter, labelled as Al) catalysts with 4 wt% additive CeO2 and/or La2O3 were prepared and characterized by X-ray photoelectron spectroscopy (XPS), NO-temperature programmed desorption (NO-TPD), N2-adsorption/desorption (Brunauer-Emmet-Teller BET method), X-ray diffraction (XRD) and CO-chemisorption. Catalytic activities for CH4, CO and NO conversion were tested in a gas mixture simulated the emissions from natural gas vehicles (NGVs) operated under stoichiometric conditions. The results indicated that all catalysts exhibited excellent catalytic performances for CH4 and CO oxidation and the promoting effect of CeO2 or La2O3 was significant for NO conversion. XPS results showed that the electron density around Pd was increased by CeO2 and/or La2O3, the binding energy of Pd 3d decreased as the order: Pd/Al>Pd/Ce/Al>Pd/La/Al>Pd/CeLa/Al. The electron-rich Pd showed Rh-like catalytic properties which exhibited good activity for the reduction of NO. NO-TPD results showed that the addition of CeO2 and/or La2O3 increased NO adsorption on surface, and promoted the conversion of NO.

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Oxidation of NO over cobalt oxide supported on esoporous silica Yan Huang*;Dongmei Gao;Zhiquan Tong;Junfeng Zhang;He Luo 2009, 18(4): 421-428.  DOI: 摘要 ( 10154 )   PDF   Cobalt oxide catalysts supported on mesoporous silica (Co3O4/MPS) were prepared, characterized and applied for catalytic oxidation of NO. Effects of catalyst supports, calcination temperatures, H2O and SO2 on NO conversion were investigated. The samples were also characterized by BET, XRD, FTIR and TG/DTG. The results suggested that Co3O4/MPS catalyst calcined at 573 K had the smallest crystal particles and the best surface dispersion. This catalyst had the highest activity and yielded 82% NO conversion at 573 K, at a space velocity of 12000 h−1. Although the conversion of NO decreased with the introduction of H2O, it could be restored completely after removing residual H2O from Co3O4/MPS catalyst by heating at 573 K. In the presence of SO2, the oxidation activity decreased and CoSO4 was detected on the catalyst. The NO conversion decreased to 30.2% in the presence of SO2 and H2O. It could not be restored completely after cutting off H2O and SO2. The deactivation of the catalyst in the presence of SO2 and H2O was attributed to the formation of cobalt sulfate species.

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Activation pressure studies with an iron-based catalyst for slurry Fischer-Tropsch synthesis Qinglan Hao;*;Liang Bai;Hongwei Xiang;Yongwang Li 2009, 18(4): 429-435.  DOI: 摘要 ( 8241 )   PDF   Fischer-Tropsch synthesis (FTS) was carried out with an industrial iron-based catalyst (100Fe/5Cu/6K/16SiO2, by weight) under the baseline conditions in a stirred tank slurry reactor (STSR). The effects of activation pressure on the catalyst activity and selectivity were investigated. It was found that iron phase compositions, textural properties, and FTS performances of the catalysts were strongly dependent on activation pressure. The high activation pressure retards the carburization. Møssbauer effect spectroscopy (MES) results indicated that the contents of the iron carbides clearly decrease with the increase of activation pressure, especially for the activation pressure increasing from 1.0 MPa to 1.5 MPa, and the reverse trend is observed for superparamagnetic Fe3+ (spm). The higher content of Fe3+ (spm) results in the higher amount of CO2 in tail gas when the catalyst is reduced at higher pressure. The catalyst activity decreases with the increase of activation pressure. The high quantity of iron carbides is necessary to obtain high FTS activity. However, the activity of the catalyst activated in syngas can not be predicted solely from the fraction of the carbides. It is concluded that activation with syngas at the lower pressure would be the most desirable for the better activity and stability on the iron-based catalyst.

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Monolithic macroporous catalysts--a new route for miniaturization of water-gas shift reactor Hao Liang;Yuan Zhang;Yuan Liu* 2009, 18(4): 436-440.  DOI: 摘要 ( 7419 )   PDF   Monolithic macroporous Pt/CeO2/Al2O3 catalysts were prepared using concentrated emulsions synthesis route, and the obtained samples were characterized with SEM, TG, TEM, XRD and TPR techniques. These monolithic catalysts were applied to water gas shift (WGS) reaction in reformed gases. The SEM and TEM results indicated that the monoliths possessed macroporosity, and that the platinum particles homogeneously dispersed on the supports with the particle size in the range of 1−2 nm. The reducibility of the catalysts was characterized by TPR method, and it was shown that the monolithic PtOx/CeO2/Al2O3 exhibited the similar reducibility property to that of the particle PtOx/CeO2 reported in literatures. The CO conversion over the monolithic catalysts is higher than that over micro-reactor catalysts for WGS reaction in the reformed gases conditions, indicating that the monolithic macroporous catalysts is a potential new route for miniaturization of WGS reactor.

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Effects of additive gases on dimethyl ether conversion through dielectric barrier discharge Baowei Wang*;Xiaolei Cao;Yigang Yan;Genhui Xu 2009, 18(4): 441-444.  DOI: 摘要 ( 7814 )   PDF   Effects of additive gases on dimethyl ether (DME) conversion through dielectric barrier discharge (DBD) were investigated. Most of the additive gases tested in this work increased the conversion of DME, but decreased the yield of liquid product. However, the addition of O2 markedly increased both the conversion of DME and the yield of liquid product. The results show that when O2 volume fraction was 39.95%, the conversion of DME was close to 100% and the yield of liquid product reached 34.43%. Different additive gases resulted in different mass fractions variation of components in liquid products.

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Effect of ZnO on the performance of Ag/SiO2 catalyst for the vapor-phase synthesis of 3-methylindole Yang Hu;Wenhui Lv;Dongyan Liu;Jing Liu;Lei Shi*;Qi Sun 2009, 18(4): 445-448.  DOI: 摘要 ( 7898 )   PDF   The vapor-phase synthesis of 3-methylindole over Ag/SiO2 doped with ZnO was investigated. The catalysts were characterized by XRD, H2- TPR, NH3-TPD and TG techniques. The results indicated that ZnO promoter greatly enhanced the initial activity of the catalyst but disfavored its stability. H2-TPR and XRD results showed that the reduction peak of Ag2O shifted to higher temperature and the intensity of silver diffraction peaks was much weaker after the addition of ZnO promoter to Ag/SiO2. This indicated that there existed the interaction between Ag2O and SiO2-ZnO which promoted the silver particles dispersing on the support and inhibited the sintering of silver during the reaction. NH3-TPD and TG results revealed that the acid amounts of the catalyst and coking increased after adding ZnO to Ag/SiO2, which resulted in the deactivation of Ag/SiO2-ZnO catalyst rapidly.

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A comparative study of CuO/TiO2-SnO2, CuO/TiO2 and CuO/SnO2 catalysts for low-temperature CO oxidation Kairong Li;Yaojie Wang;Shurong Wang*;Baolin Zhu;Shoumin Zhang;Weiping Huang;Shihua Wu 2009, 18(4): 449-452.  DOI: 摘要 ( 8567 )   PDF   Nanometer SnO2 particles were synthesized by sol-gel dialytic processes and used as a support to prepare CuO supported catalysts via a deposition-precipitation method. The samples were characterized by means of TG-DTA, XRD, H2-TPR and XPS. The catalytic activity of the CuO/TiO2-SnO2 catalysts was markedly depended on the loading of CuO, and the optimum CuO loading was 8 wt.% (T100 = 80 ◦C). The CuO/TiO2-SnO2 catalysts exhibited much higher catalytic activity than the CuO/TiO2 and CuO/SnO2 catalysts. H2-TPR result indicated that a large amount of CuO formed the active site for CO oxidation in 8 wt.% CuO/TiO2-SnO2 catalyst.

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A novel correlation for estimation of hydrate forming condition of natural gases Alireza Bahadori*;Hari. B. Vuthaluru 2009, 18(4): 453-457.  DOI: 摘要 ( 8998 )   PDF   An inherent problem with natural gas production or transmission is the formation of gas hydrates, which can lead to safety hazards to production/ transportation systems and to substantial economic risks. Therefore, an understanding of conditions where hydrates form is necessary to overcome hydrate related issues. Over the years, several models requiring more complicated and longer computations have been proposed for the prediction of hydrate formation conditions of natural gases. For these reasons, it is essential to develop a reliable and simple-to-use method for oil and gas practitioners. The purpose of this study is to formulate a novel empirical correlation for rapid estimation of hydrate formation condition of sweet natural gases. The developed correlation holds for wide range of temperatures (265–298 K), pressures (1200 to 40000 kPa) and molecular weights (16−29). New proposed correlation shows consistently accurate results across proposed pressure, temperature and molecular weight ranges. This consistency could not be matched by any of the widely accepted existing correlations within the investigated range. For all conditions, new correlation showed average absolute deviation to be less than 0.2% and provided much better results than the widely accepted existing correlations.

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Effect of CeO2 preparation method and Cu loading on CuO/CeO2 catalysts for methane combustion Weiling Yang;Dao Li*;Dongmei Xu;Xingyi Wang 2009, 18(4): 458-466.  DOI: 摘要 ( 8813 )   PDF   CeO2 was synthesized by sol-gel, hydrothermal, nitrate thermal decomposition methods, respectively, and used as support to prepare CuO/CeO2 catalysts. According to characterization and reaction results, preparation method of CeO2 had a great influence on the physicochemical properties and activities of CuO/CeO2 catalysts. CuO with high dispersion and strong interaction with CeO2 was highly active in methane combustion, while CuO particles less associated with CeO2 showed less activity. The CuO catalyst supported on CeO2 which was prepared via nitrate thermal decomposition method showed the largest area, the smallest particle size, the highest dispersion of copper species and strong support metal interactions. Therefore, it presented the highest redox ability and activity for methane combustion. Activities of the catalysts with different copper content kept increasing until 5% Cu loading and from then on kept constant. Moreover, methane conversion decreased as methane space velocities increased on CuO/CeO2 catalyst. Addition of CO2 to the feed did not produce a significant effect on the catalytic activity, but the presence of H2O provoked a remarkable decrease on the activity of CuO/CeO2 catalyst.

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Partial oxidation of simulated hot coke oven gas to syngas over Ru-Ni/Mg(Al)O catalyst in a ceramic membrane reactor Hongwei Cheng;Xionggang Lu;Xu Liu;Yuwen Zhang;Weizhong Ding* 2009, 18(4): 467-473.  DOI: 摘要 ( 10194 )   PDF   Hydrogen amplification from simulated hot coke oven gas (HCOG) was investigated in a BaCo0.7Fe0.2Nb0.1O3−δ (BCFNO) membrane reactor combined with a Ru-Ni/Mg(Al)O catalyst by the partial oxidation of hydrocarbon compounds under atmospheric pressure. Under optimized reaction conditions, the dense oxygen permeable membrane had an oxygen permeation flux around 13.3 ml/(cm2·min). By reforming of the toluene and methane, the amount of H2 in the reaction effluent gas was about 2 times more than that of original H2 in simulated HCOG. The Ru-Ni/Mg(Al)O catalyst used in the membrane reactor possessed good catalytic activity and resistance to coking. After the activity test, a small amount of whisker carbon was observed on the used catalyst, and most of them could be removed in the hydrogen-rich atmosphere, implying that the carbon deposition formed on the catalyst might be a reversible process.