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Novel promoting effects of cerium on the activities of NO_x reduction by NH_3 over TiO_2-SiO_2-WO_3 monolith catalysts 认领 引用 被引量：15
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作者 房志涛 林涛 +3 位作者 徐海迪 吴干学 孙萌萌 陈耀强 《Journal of Rare Earths》 SCIE EI CAS CSCD 2014年第10期952-959,共8页
A series of catalysts were prepared by doping different loadings of CeO2 over TiO2-SiO2-WO3 and used for the selective catalytic reduction of NOx by NH3. The experimental results showed that the selective catalytic re... A series of catalysts were prepared by doping different loadings of CeO2 over TiO2-SiO2-WO3 and used for the selective catalytic reduction of NOx by NH3. The experimental results showed that the selective catalytic reduction（SCR） performance and SO2-resistant ability of TiO2-SiO2-WO3 were greatly enhanced by the introduction of cerium. The catalyst containing 10% CeO2 showed the highest NO conversion in a wide temperature range and good N2 selectivity with broad operation temperature window at the gas hourly space velocity（GHSV） of 30000 h–1, which was a very promising catalyst for NOx abatement from diesel engine exhaust. The catalysts were characterized by X-ray diffraction（XRD）, scanning electron microscopy with energy dispersive X-ray spectroscopy（SEM-EDS）, N2 adsorption-desorption（BET） and X-ray photoelectron spectroscopy（XPS）. The characterization results showed that the bigger pore radius, higher surface atomic concentration and dispersion of Ce and the abundant adsorbed oxygen on the surface of catalyst contributed to the best NH3-SCR performance of CeO2/TiO2-SiO2-WO3 catalyst containing 10% CeO2. 展开更多
关键词 NH3-SCR NO cerium CeO2/TiO2-SiO2-WO3 monolith catalyst rare earths
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Effect of SiO2 addition on NH4HSO4 decomposition and SO2 poisoning over V2O5-MoO3/TiO2-CeO2 catalyst 认领 引用 被引量：11
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作者 Chengqiang Zheng Teng Cheng +2 位作者 Linjun Yang Hao Wu Hongmei Fan 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2020年第5期279-291,共13页
The deposition of NH4 HSO4 and the poisoning effect of SO2 on SCR catalyst are the main obstacles that restrict the industrial application of CeO2-doped SCR catalysts.In this work,deposited NH4 HSO4 decomposition beha... The deposition of NH4 HSO4 and the poisoning effect of SO2 on SCR catalyst are the main obstacles that restrict the industrial application of CeO2-doped SCR catalysts.In this work,deposited NH4 HSO4 decomposition behavior and SO2 poisoning over V2 O5-MoO3/TiO2 catalysts modified with CeO2 and SiO2 were investigated.By the means of characterization analysis,it was found that the addition of SiO2 into VMo/Ti-Ce had an impact on the interaction existed between catalyst surface atoms and NH4 HSO4.Temperatureprogrammed methods and in situ diffused reflectance infrared Fourier transform spectroscopy(DRIFTS)experiments indicated that the doping of SiO2 promoted the decomposition of deposited NH4 HSO4 on VMo/Ti-Ce catalyst surface by reducing the thermal stability of NH4 HSO4 and enhancing the NH4 HSO4 reactivity with NO in low temperature.And this improvement may be the reason for the better catalytic activity than VMo/Ti-Ce in the case of NH4 HSO4 deposition.Accompanied with cerium sulfate species generated over catalyst surface,the conversion of SO2 to SO3 was inhibited in SiCe mixed catalyst.The addition of SiO2 could promote the decomposition of cerium sulfate,which may be a potential strategy to enhance the resistance of SO2 poisoning over CeO2-modifed catalysts. 展开更多
关键词 CeO2-doped SCR catalyst SiO2 addition NH4HSO4 decomposition SO2 poisoning Cerium sulfate
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Effect of TiO_2 surface properties on the SCR activity of NOx emission abatement catalyst 认领 引用 被引量：6
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作者 YEDai-qi TIANLiu-qing LIANGHong 《Journal of Environmental Sciences》 SCIE EI CAS 2002年第4期530-535,共6页
NOx emission abatement catalysts V 2O 5 supported on various TiO 2 including anatase, rutile and mixture of both were investigated with various physico\|chemical measurements such as BET, NH\-3\|TPD, NARP, XRD and so ... NOx emission abatement catalysts V 2O 5 supported on various TiO 2 including anatase, rutile and mixture of both were investigated with various physico\|chemical measurements such as BET, NH\-3\|TPD, NARP, XRD and so on, and the effect of TiO\-2 surface properties on the SCR(selective catalytic reduction) activity of V\-2O\-5/TiO\-2 catalysts was studied. It was found that the TiO\-2 surface properties had strong affect on the SCR activity of V\-2O\-5/TiO\-2 catalysts. The stronger acidic property resulted in the higher exposure of active sites as well as the higher SCR activity. 展开更多
关键词 NOx SCR(selective catalytic reduction) surface acidity V\-2O\-5/TiO\-2 catalyst
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The effect of ethanol on the performance of CrO_x/SiO_2 catalysts during propane dehydrogenation 认领 引用 被引量：5
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作者 李利娜 朱文良 +6 位作者 石磊 刘勇 刘红超 倪友明 刘世平 周慧 刘中民 《Chinese Journal of Catalysis》 SCIE EI CAS CSCD 北大核心 2016年第3期359-366,共8页
The effects of ethanol vapor pretreatment on the performance of CrOx/SiO2 catalysts during the dehydrogenation of propane to propylene were studied with and without the presence of CO2.The catalyst pretreated with eth... The effects of ethanol vapor pretreatment on the performance of CrOx/SiO2 catalysts during the dehydrogenation of propane to propylene were studied with and without the presence of CO2.The catalyst pretreated with ethanol vapor exhibited better catalytic activity than the pristine CrOx/SiO2,generating 41.4% propane conversion and 84.8% propylene selectivity.The various catalyst samples prepared were characterized by X-ray diffraction,transmission electron microscopy,temperature-programmed reduction,X-ray photoelectron spectroscopy and reflectance UV-Vis spectroscopy.The data show that coordinative Cr^3＋ species represent the active sites during the dehydrogenation of propane and that these species serve as precursors for the generation of Cr^3＋.Cr^3＋ is reduced during the reaction,leading to a decrease in catalytic activity.Following ethanol vapor pretreatment,the reduced CrOx in the catalyst is readily re-oxidized to Cr^6＋ by CO2.The pretreated catalyst thus exhibits high activity during the propane dehydrogenation reaction by maintaining the active Cr^3＋ states. 展开更多
关键词 Propane Dehydrogenation CrOx/SiO2 catalyst Ethanol vapor pretreatment Carbon dioxide
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Effect of calcination temperature on structure and performance of Ni/TiO_2-SiO_2 catalyst for CO_2 reforming of methane 认领 引用 被引量：6
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作者 Sanbing Zhang Jiankang Wang Xiaolai Wang 《Journal of Natural Gas Chemistry》 2008年第2期179-183,共5页
The influence of calcination temperature on the structure and catalytic behavior of Ni/TiO2-SiO2 catalyst, for CO2 reforming of methane to synthesis gas under atmospheric pressure, was investigated. The results showed... The influence of calcination temperature on the structure and catalytic behavior of Ni/TiO2-SiO2 catalyst, for CO2 reforming of methane to synthesis gas under atmospheric pressure, was investigated. The results showed that the Ni/TiO2-SiO2 catalyst calcined at 700 ℃ had high and stable activity while the catalysts calcined at 550 and 850 ℃ had low and unstable activity. Depending on the calcination temperature, one, two, or three of the following Ni-containing species, NiO, Ni2.44Ti0.72Si0.07O4, and NiTiO3 were identified by combining the temperature programmed reduction （TPR） and X-ray diffraction （XRD） results. Their reducibility decreased in the sequence： NiO〉Ni2.44Ti0.72Si0.07O4〉NiTiO3. It suggests that high and stable activities observed over the Ni/TiO2-SiO2 catalyst calcined at 700 ~C were induced by the formation of Ni2.44Ti0.72Si0.07O4 and smaller NiO species crystallite size. 展开更多
关键词 Ni/TiO2-SiO2 catalyst sol-gel CO2 reforming methane
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Construction of SiO2-TiO2/g-C3N4 composite photocatalyst for hydrogen production and pollutant degradation: Insight into the effect of SiO2 认领 引用 被引量：1
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作者 Sijia Sun Hao Ding +5 位作者 Lefu Mei Ying Chen Qiang Hao Wanting Chen Zhuoqun Xu Daimei Chen 《Chinese Chemical Letters》 SCIE CAS CSCD 2020年第9期2287-2294,共8页
Using low-cost precipitated silica(SiO2) as the carrier,a ternary SiO2-TiO2/g-C3N4 composite photocatalyst was prepared via the sol-gel method associated with a wet-grinding process.The asprepared composite exhibits p... Using low-cost precipitated silica(SiO2) as the carrier,a ternary SiO2-TiO2/g-C3N4 composite photocatalyst was prepared via the sol-gel method associated with a wet-grinding process.The asprepared composite exhibits photocatalytic hydrogen production and pollutant degradation performance under solar-like irradiation.The effect of SiO2 carrier on the properties of the heterostructure between TiO2 and g-C3N4(CN) was systematically studied.It is found that SiO2 has important effects on promoting the interaction between TiO2 and CN.The particle size of TiO2 and CN was obviously reduced during the calcination process due to the effects of SiO2.Especially,the TiO2 particles exhibit monodispersed state with particle size below 10 nm(quantum dots),resulting in the improvement of the contact area and the interaction betweenTiO2 and CN,and leading to the formation of efficient TiO2/CN Zscheme heterostructure in SiO2-TiO2/CN.Besides,the introduction of SiO2 can increase the specific surface area and light absorption of SiO2-TiO2/CN,further promoting the photocatalytic reaction.As expected,the optimum SiO2-TiO2/CN composite exhibits 12.3,3.1 and 2.9 times higher photocatalytic hydrogen production rate than that of SiO2-TiO2,CN and TiO2/CN under solar-like irradiation,while the photocatalytic active component in SiO2-TiO2/CN is only about 60 wt%.Moreover,the rhodamine B degradation rate of SiO2-TiO2/CN is also higher than that of SiO2-TiO2,CN and TiO2/CN. 展开更多
关键词 SiO2 carrier Heterostructure Photocatalyst g-C3N4 TiO2
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In-Situ FT-IR Investigation Methane to Syngas over of Partial Oxidation of Rh/SiO2 Catalyst 认领 引用 被引量：3
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作者 Tinghua Wu Dongmin Lin +4 位作者 Ying Wu Xiaoping Zhou Qiangu Yan Weizheng Weng Huilin Wan 《Journal of Natural Gas Chemistry》 2007年第3期316-321,共6页
Partial oxidation of methane to syngas （POM） over Rh/SiO2 catalyst was investigated using in-situ FT-IR. When methane interacted with 1.0wt%Rh/SiO2 catalyst, it was dissociated to adsorbed hydrogen and CHx species. ... Partial oxidation of methane to syngas （POM） over Rh/SiO2 catalyst was investigated using in-situ FT-IR. When methane interacted with 1.0wt%Rh/SiO2 catalyst, it was dissociated to adsorbed hydrogen and CHx species. The adsorbed hydrogen atoms were transferred to SiO2 surface by ＂spill-over＂ and reacted with lattice oxygen to form surface -OH species. POM mechanism was investigated over Rh/SiO2 catalyst using in-situ FT-IR. It was found that CO2 was formed before CO could be detected when CH4 and O2 were introduced over the preoxidized Rh/SiO2 catalyst, whereas CO was detected before CO2 was formed over the prereduced Rh/SiO2 catalyst. 展开更多
关键词 partial oxidation syngas Rh/SiO2 catalyst in-situ FT-IR
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Synthesis of Methyl Glycolate by Hydrogenation of Dimethyl Oxalate over Cu-Ag/SiO_2 Catalyst 认领 引用 被引量：26
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作者 Baowei Wang Qian Xu Hua Song Genhui Xu 《Journal of Natural Gas Chemistry》 2007年第1期78-80,共3页
Methyl glycolate is a good solvent and can be used as feedstock for the synthesis of some important organic chemicals. Catalytic hydrogenation of dimethyl oxalate （DMO） over copper-silver catalyst supported on silic... Methyl glycolate is a good solvent and can be used as feedstock for the synthesis of some important organic chemicals. Catalytic hydrogenation of dimethyl oxalate （DMO） over copper-silver catalyst supported on silica was studied. The Cu-Ag/SiO2 catalyst supported on silica sol was prepared by homogeneous deposition-precipitation of the mixture of aqueous euprammonia complex and silica sol. The proper active temperature of Cu-Ag/SiO2 catalyst for hydrogenation of DMO was 523-623 K. The most preferable reaction conditions for methyl glycolate （MG） were optimized： temperature at 468-478 K, 40-60 mesh catalyst diameter, H2/DMO ratio 40, and 1.0 h^-1 of LHSV. 展开更多
关键词 dimethyl oxalate methyl glycolate ethylene glycol hydrogenation Cu-Ag/SiO2 catalyst
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Photocatalytic oxidation of Rhodamine B in a three-phase internal circulating fluidized bed with TiO_2/SiO_2 as photocatalyst 认领 引用
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作者 尤宏 孙丽欣 +1 位作者 罗薇楠 刘婷 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2010年第5期651-656,共6页
A novel photoreactor of three-phase internal circulating fluidized bed was applied to the degradation of Rhodamine B with TiO2/SiO2 catalyst and TiO2 powder,respectively.The experimental results showed that the photoc... A novel photoreactor of three-phase internal circulating fluidized bed was applied to the degradation of Rhodamine B with TiO2/SiO2 catalyst and TiO2 powder,respectively.The experimental results showed that the photocatalytic activity of TiO2/SiO2 catalyst was much higher than that of TiO2 powder under the same condition,and the half life of Rhodamine B using TiO2/SiO2 was 9.5 min,much lower than 63 min when using TiO2 powder.Moreover,TiO2/SiO2 had a good adsorption capacity of Rhodamine B,which played an important role on degradation.In addition,it was found that the degradation kinetics of Rodamine B with TiO2/SiO2 catalyst did not follow the first order reaction.The degradation kinetics model in terms of the adsorption process of catalyst and the analytic solution of reactant degradation rate in liquid phase could be deduced,which consisted of two parts.The first part was due to the adsorption,while the second part was due to the photocatalysis.In the beginning of the reaction,the adsorption process was dominant.However,when the adsorption achieved a balance,the degradation of Rhodamine B in liquid phase and solid phase was mainly caused by photocatalysis and the degradation kinetics model conformed to the first order reaction. 展开更多
关键词 photocatalysis three-phase fluidized bed TiO2/SiO2 kinetics adsorption
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In_2O_3-modified Cu/SiO_2 as an active and stable catalyst for the hydrogenation of methyl acetate to ethanol 认领 引用 被引量：11
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作者 Yu Zhang Chenliang Ye +2 位作者 Cuili Guo Changna Gan Xinmeng Tong 《Chinese Journal of Catalysis》 SCIE EI CAS CSCD 北大核心 2018年第1期99-108,共10页
A series of indium oxide‐modified Cu/SiO2catalysts were synthesized and used to produce ethanol via methyl acetate hydrogenation.In‐Cu/SiO2catalyst containing1.0wt%In2O3exhibited the best catalytic activity and stab... A series of indium oxide‐modified Cu/SiO2catalysts were synthesized and used to produce ethanol via methyl acetate hydrogenation.In‐Cu/SiO2catalyst containing1.0wt%In2O3exhibited the best catalytic activity and stability.The physicochemical properties of the synthesized catalysts were investigated using several characterization methods and the results showed that introducing suitable indium to Cu/SiO2increased the copper dispersion,diminished the copper crystallite size,and enriched the surface Cu+concentration.Furthermore,the Cu/SiO2catalyst gradually deactivated during the stability test,which was mainly attributed to copper sintering and the valence change in surface copper species.In contrast,indium addition can inhibit the thermal transmigration and accumulation of copper nanoparticles to stabilize the catalyst.?2018,Dalian Institute of Chemical Physics,Chinese Academy of Sciences.Published by Elsevier B.V.All rights reserved. 展开更多
关键词 Methyl acetate Hydrogenation Indium Cu/SiO2 catalyst Ethanol
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Application of Li_2SiO_3 as a heterogeneous catalyst in the production of biodiesel from soybean oil 认领 引用 被引量：6
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作者 Jian Xun Wang Kung Tung Chen +1 位作者 Shiuh Tsuen Huang Chiing Chang Chen 《Chinese Chemical Letters》 SCIE CAS CSCD 2011年第11期1363-1366,共4页
Biodiesel was synthesized from soybean oil by transesterification over Li_2SiO_3 catalyst.The Li_2SiO_3 can be used for biodiesel production directly without further drying or thermal pretreatment,no obvious differenc... Biodiesel was synthesized from soybean oil by transesterification over Li_2SiO_3 catalyst.The Li_2SiO_3 can be used for biodiesel production directly without further drying or thermal pretreatment,no obvious difference in the FAME conversion（92.4-96.7%） between the air-exposed catalyst（24-72 h） and the fresh one（94.2%）.This leads to important benefits when considering industrial applications of Li_2SiO_3 as a solid catalyst for storing and handling catalyst without taking special actions. 展开更多
关键词 Biodiesel Solid catalyst Li2SiO3 Transesterification Triglyceride
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The nature of the deactivation of hydrothermally stable Ni/SiO2–Al2O3 catalyst in long-time aqueous phase hydrogenation of crude 1,4-butanediol 认领 引用 被引量：4
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作者 Haitao Li Yin Zhang +5 位作者 Hongxi Zhang Xiaoqin Qin Yalin Xu RuifangWu Zheng Jiang Yongxiang Zhao 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2019年第12期2960-2967,共8页
The deactivation of Ni/SiO2-Al2 O3 catalyst in hydrogenation of crude 1,4-butanediol was investigated.During the operation time of 2140 h,the catalyst showed slow activity decay.Characterization results,for four spent... The deactivation of Ni/SiO2-Al2 O3 catalyst in hydrogenation of crude 1,4-butanediol was investigated.During the operation time of 2140 h,the catalyst showed slow activity decay.Characterization results,for four spent catalysts used at different time,indicated that the main reason of the catalyst deactivation was the deposition of carbonaceous species that covered the active Ni and blocked mesopores of the catalyst.The TPO and SEM measurements revealed that the carbonaceous species included both oligomeric and polymeric species with high C/H ratio and showed sheet.Such carbonaceous species might be eliminated through either direct H2 reduction or the combined oxidation-reduction methodologies. 展开更多
关键词 1,4-Butanediol Hydrogenation Ni/SiO2–Al2O3 catalyst Deactivation Regeneration
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A pH-responsive TiO_2-based Pickering emulsion system for in situ catalyst recycling 认领 引用 被引量：6
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作者 Yajuan Hao Yanfang Liu +3 位作者 Rui Yang Xiaoming Zhang Jian Liu Hengquan Yang 《Chinese Chemical Letters》 SCIE CAS CSCD 2018年第6期778-782,共5页
Developing methods for efficient product/catalyst separation and catalyst recycling is meaningful in multi-phase catalytic reactions. Here, we reported a p H-responsive emulsion system stabilized by interfacially acti... Developing methods for efficient product/catalyst separation and catalyst recycling is meaningful in multi-phase catalytic reactions. Here, we reported a p H-responsive emulsion system stabilized by interfacially active TiO2 nanoparticles for achieving in situ product/catalyst separation and catalyst recycling. In this system, emulsification and demulsification process could be easily engineered through tuning the p H values. The emulsion droplets were destroyed completely at a p H value of 3–4, and the solid catalyst distributed in the aqueous phase could be used to the next reaction cycle after removal of the organic product and adjusting the p H to 7–8. Such a p H triggered switchable Pickering emulsion catalytic system not only shows good recyclability of the solid catalyst but also high catalytic efficiency,and could be recycled more than 10 cycles. 展开更多
关键词 Interfacially active TiO2 nanoparticles pH-responsive Pickering emulsion Catalyst recycling
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Partial oxidation of methane over SiO2 supported Ni and NiCe catalysts 认领 引用 被引量：4
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作者 A.Emamdoust V.La Parola +3 位作者 G.Pantaleo M.L.Testa S.Farjami Shayesteh A.M.Venezia 《Journal of Energy Chemistry》 SCIE EI CAS CSCD 2020年第8期1-9,I0001,共9页
Nickel and nickel-ceria catalysts supported on high surface area silica, with 6 wt% Ni and 20 wt% CeO2 were prepared by microwave assisted(co) precipitation method. The catalysts were investigated by XRD,TPR and XPS a... Nickel and nickel-ceria catalysts supported on high surface area silica, with 6 wt% Ni and 20 wt% CeO2 were prepared by microwave assisted(co) precipitation method. The catalysts were investigated by XRD,TPR and XPS analyses and they were tested in partial oxidation of methane(CPO). The catalytic reaction was carried out at atmospheric pressure in a temperature range of 400–800℃ with a feed gas mixture containing methane and oxygen in a molecular ratio CH4/O2=2. The Ni catalyst exhibited 60% methane conversion with 60% selectivity to CO already at 500℃. On the contrary, the Ni–Ce catalyst was inert to CPO up to 700℃. Moreover, the former catalyst reproduced its activity at the descending temperatures maintaining a good stability at 600℃, over a reaction time of 80 h, whereas the latter one completely deactivated. Test of CH4 temperature programmed surface reaction(CH4-TPSR) revealed a higher methane activation temperature(> 100℃) for the Ni–Ce catalyst as compared to the Ni one. Noticeable improvement of the ceria containing catalyst occurred when the reaction test started at a temperature higher than the methane decomposition temperature. In this case, the sample achieved the same catalytic behavior of the Ni catalyst. As confirmed by XPS analyses, the distinct electronic state of the supported nickel was responsible for the differences in catalytic behavior. 展开更多
关键词 Methane catalytic partial oxidation(CPO) Ni catalyst NiCe SiO2 supported catalysts
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Comparative study of fluidized-bed and fixed-bed reactor for syngas methanation over Ni-W/TiO_2-SiO_2 catalyst 认领 引用 被引量：9
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作者 Bo Liu Shengfu Ji 《Journal of Energy Chemistry》 SCIE EI CAS CSCD 2013年第5期740-746,共7页
In this work,syngas methanation over Ni-W/TiO2-SiO2catalyst was studied in a fluidized-bed reactor(FBR)and its performance was compared with a fixed-bed reactor(FIXBR).The effects of main operating variables including... In this work,syngas methanation over Ni-W/TiO2-SiO2catalyst was studied in a fluidized-bed reactor(FBR)and its performance was compared with a fixed-bed reactor(FIXBR).The effects of main operating variables including feedstock gases space velocity,coke content,bed temperature and sulfur-tolerant stability of 100 h life were investigated.The structure of the catalysts was characterized by XRD,N2adsorptiondesorption and TEM.It is found that under same space velocity from 5000 h 1to 25000 h 1FBR gave a higher CH4yield,lower coke content,and lower bed temperature than those obtained in FIXBR.Ni-W/TiO2-SiO2catalyst possessed excellent sulfur-tolerant stability on the feedstock gases less than 500 ppm H2S in FBR.The carbon deposits formed on the spent catalyst were in the form of carbon fibers in FBR,while in the form of dense accumulation distribution appearance in FIXBR. 展开更多
关键词 syngas methanation Ni-W/TiO2-SiO2catalyst fluidized bed fixed bed
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Effect of CO_2 on the structural variation of Na_2WO_4/Mn/SiO_2 catalyst for oxidative coupling of methane to ethylene 认领 引用 被引量：3
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作者 Jia Shi Lu Yao Changwei Hu 《Journal of Energy Chemistry》 SCIE EI CAS CSCD 2015年第4期394-400,共7页
In this work,the influence of CO2 on the structural variation and catalytic performance of Na2WO4/Mn/Si O2 for oxidative coupling of methane to ethylene was investigated. The catalyst was prepared by impregnation meth... In this work,the influence of CO2 on the structural variation and catalytic performance of Na2WO4/Mn/Si O2 for oxidative coupling of methane to ethylene was investigated. The catalyst was prepared by impregnation method and characterized by XRD,Raman and XPS techniques. Appropriate amount of CO2 in the reactant gases enhanced the formation of surface tetrahedral Na2WO4 species and promoted the migration of O in MOx,Na,W from the catalyst bulk to surface,which were favorable for oxidative coupling of methane. When the molar ratio of CH4/O2/CO2 was 3/1/2,enriched surface tetrahedral Na2WO4 species and high surface concentration of O in MOx,Na,W were detected,and then high CH4 conversion of 33.1% and high C2H4 selectivity of 56.2% were obtained. With further increase of CO2 in the reagent gases,the content of active surface tetrahedral Na2WO4 species and surface concentration of O in MOx,Na,W decreased,while that of inactive species（Mn WO4 and Mn2O3） increased dramatically,leading to low CH4 conversion and low C2H4 selectivity. It could be speculated that Na2WO4 crystal was transformed into Mn WO4 crystal with excessive CO2 added under the reaction conditions. Pretreatment of Na2WO4/Mn/Si O2 catalyst by moderate amount of CO2 before OCM also promoted the formation of Na2WO4 species. 展开更多
关键词 Oxidative coupling of methane CO2 C2H4 Na2WO4/Mn/SiO2catalyst Structural variation
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Active Fischer-Tropsch synthesis Fe-Cu-K/SiO_2 catalysts prepared by autocombustion method without a reduction step 认领 引用 被引量：1
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作者 Suthasinee Pengnarapat Peipei Ai +3 位作者 Prasert Reubroycharoen Tharapong Vitidsant Yoshiharu Yoneyama Noritatsu Tsubaki 《Journal of Energy Chemistry》 SCIE EI CAS CSCD 2018年第2期432-438,共7页
The purpose of this study was to prepare iron-based catalysts supported on silica by autocombustion method for directly using for Fischer-Tropsch synthesis（FTS） without a reduction step. The effect of different citr... The purpose of this study was to prepare iron-based catalysts supported on silica by autocombustion method for directly using for Fischer-Tropsch synthesis（FTS） without a reduction step. The effect of different citric acid（CA）：iron nitrate（N） molar ratios and acid types on the FTS performance of catalysts were investigated. The CA：N molar ratios had an important influence on the formation of iron active phases and FTS activity. The iron carbide（FexC）, which is known to be one of the iron active phases, was demonstrated by the X-ray diffraction and X-ray photoelectron spectroscopy. Increasing the CA：N molar ratios up to 0.1 increased CO conversion of catalyst to 86.5%, which was then decreased markedly at higher CA：N molar ratios. An excess of CA resulted in carbon residues covering the catalyst surface and declined FTS activity. The optimal catalyst（CA：N molar ratio = 0.1） achieved the highest CO conversion when compared with other autocombustion catalysts as well as reference catalyst prepared by impregnation method, followed by a reduction step. The autocombustion method had the advantage to synthesize more efficient catalysts without a reduction step. More interestingly, iron-based FTS catalysts need induction duration at the initial stage of FTS reaction even after reduction, because metallic iron species need time to be transformed to FexC. But here, even if without reduction, FexC was formed directly by autocombustion and induction period was eliminated during FTS reaction. 展开更多
关键词 Fischer-Tropsch synthesis Iron-based catalysts Autocombustion Iron carbide SiO2
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Influence of catalyst support structure on ethene/decene metathesis and coke formation over WO_3/SiO_2 catalyst 认领 引用 被引量：1
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作者 Zheng Min Chen Sheng-Li +4 位作者 Zhang Jun-Hui Liu Yan Sang Lei You Ju Wang Xiao-Dong 《Petroleum Science》 SCIE CAS CSCD 2013年第1期112-119,共8页
8wt%WO3/SiO2 metathesis （disproportionation） catalysts with different pore structures were prepared by the incipient-wetness-impregnation method. The as-synthesized catalysts were characterized by N2 adsorpfion-deso... 8wt%WO3/SiO2 metathesis （disproportionation） catalysts with different pore structures were prepared by the incipient-wetness-impregnation method. The as-synthesized catalysts were characterized by N2 adsorpfion-desorption, scanning electron microscopy （SEM）, X-ray diffraction （XRD）, UV-visible diffuse reflectance spectroscopy （DRS） and scanning transmission electron microscopy-high-angle annular dark field （STEM HAADF）. The results of STEM HAADF showed that WO3 species were not uniformly distributed on the SiO2 support. The experimental results of 8wt%WO3/SiO2 performance in ethene/decene metathesis revealed that the catalytic effect of 8wt%WO3/SiO2 catalyst and coke formation over it were closely related to the support pore structure： The 8wt%WO3/SiO2 catalyst with a more complicated pore structure showed better catalytic performance but the coke deposition rate was also faster. 展开更多
关键词 Metathesis WO3/SiO2 catalysts pore structure coke formation
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Characterization and catalytic performance of CeO_2-Co/SiO_2 catalyst for Fischer-Tropsch synthesis using nitrogen-diluted synthesis gas over a laboratory scale fixed-bed reactor 认领 引用 被引量：2
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作者 Xiaoping Dai Changchun Yu 《Journal of Natural Gas Chemistry》 2008年第1期17-23,共7页
The surface species of CO hydrogenation on CeO2-Co/SiO2 catalyst were investigated using the techniques of temperature programmed reaction and transient response method. The results indicated that the formation of H2O... The surface species of CO hydrogenation on CeO2-Co/SiO2 catalyst were investigated using the techniques of temperature programmed reaction and transient response method. The results indicated that the formation of H2O and CO2 was the competitive reaction for the surface oxygen species, CH4 was produced via the hydrogenation of carbon species step by step, and C2 products were formed by the polymerization of surface-active carbon species （-CH2-）. Hydrogen assisted the dissociation of CO. The hydrogenation of surface carbon species was the rate-limiting step in the hydrogenation of CO over CeO2-Co/SiO2 catalyst. The investigation of total pressure, gas hourly space velocity （GHSV）, and product distribution using nitrogen-rich synthesis gas as feedstock over a laboratory scale fixed-bed reactor indicated that total pressure and GHSV had a significant effect on the catalytic performance of CeO2-Co/SiO2 catalyst. The removal of heat and control of the reaction temperature were extremely critical steps, which required lower GHSV and appropriate CO conversion to avoid the deactivation of the catalyst. The feedstock of nitrogen-rich synthesis gas was favorable to increase the conversion of CO, but there was a shift of product distribution toward the light hydrocarbon. The nitrogen-rich synthesis gas was feasible for F-T synthesis for the utilization of remote natural gas. 展开更多
关键词 CeO2-Co/SiO2 catalyst Fischer-Tropsch synthesis surface species reaction condition nitrogen-rich synthesis gas product distribution
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Influence of V/P Ratio on the Catalytic Performance of VPO/SiO_2 Catalysts for Ammoxidation of Chloro-Substituted Toluenes 认领 引用
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作者 DONG Yanling XU Longlong +4 位作者 ZHANG Zhenguo LIU Wenhui LI Xiongjian ZHONG Yalan HUANG Chi 《Wuhan University Journal of Natural Sciences》 CAS CSCD 2019年第1期23-29,共7页
A series of vanadium phosphate oxide(VPO) catalysts supported on silica(VPO/Si O2) with various mole ratios of V/P(nV:nP=1:0.8-1:3) were prepared through impregnation method. The catalytic activity was evaluated by am... A series of vanadium phosphate oxide(VPO) catalysts supported on silica(VPO/Si O2) with various mole ratios of V/P(nV:nP=1:0.8-1:3) were prepared through impregnation method. The catalytic activity was evaluated by ammoxidation reactions of several kinds of chloro-substituted toluenes(CT) in a fixed-bed reactor. The catalyst presented the best performance when nV:nP is 1:1.6. The prepared catalysts were characterized by N2 adsorption, hydrogen temperature programmed reduction(TPR) and ammonia temperature programmed desorption(TPD) and etc. The results reveal that P can decrease the bonding energy of V=O and increase the mobility of lattice oxygen which was beneficial for the improvement of the catalysts, while too much P can greatly decrease the average oxidation number of V which leads to deactivation of the catalysts. The surface acidity of the VPO/Si O2 catalysts is affected by nV:nP and the catalyst had the highest surface acidity when nV:nP is 1:1.6. The selectivity of catalysts is proportional to the surface acidity when nV:nP is lower than 1:3.0. 展开更多
关键词 ammoxidation VPO/SiO2 catalyst substituted toluenes substituted benzonitriles
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