The decomposition and CO2 reforming of methane,respectively,are promising alternatives to industrial steam methane reforming. In recent years,research has been focused on the development of catalysts that can operate ...The decomposition and CO2 reforming of methane,respectively,are promising alternatives to industrial steam methane reforming. In recent years,research has been focused on the development of catalysts that can operate without getting deactivated by carbon deposition,where,in particular,carbon catalysts have shown positive results. In this work,the role of carbon materials in heterogeneous catalysis is assessed and publications on methane decomposition and CO2 reforming of methane over carbon materials are reviewed. The influence of textural properties(BET surface area and micropore volume,etc.) and oxygen surface groups on the catalytic activity of carbon materials are discussed. In addition,this review examines how activated carbon and carbon black catalysts,which are the most commonly used carbon catalysts,are deactivated. Characteristics of the carbon deposits from methane are discussed and the influence of the reactivity to CO2 of fresh carbon and carbonaceous deposits for high and steady conversion during CO2 reforming of CH4 are also considered.展开更多
Nowadays,combined steam and dry reforming of methane(CSDRM)is viewed as a new alternative for the production of high-quality syngas(termed as"metgas",H2:CO of 2.0)suitable for subsequent synthesis of methano...Nowadays,combined steam and dry reforming of methane(CSDRM)is viewed as a new alternative for the production of high-quality syngas(termed as"metgas",H2:CO of 2.0)suitable for subsequent synthesis of methanol,considered as a promising renewable energy vector to substitute fossil fuel resources.Adequate operation conditions(molar feed composition,temperature and pressure)are required for the sole production of"metgas"while achieving high CH4,CO2 and H2O conversion levels.In this work,thermodynamic equilibrium analysis of CSDRM has been performed using Gibbs free energy minimization where;(i)the effect of temperature(range:200-1000℃),(ii)feed composition(stoichiometric ratio as compared to a feed under excess steam or excess carbon dioxide),(iii)pressure(range:1-20 bar)and,(iv)the presence of a gaseous diluent on coke yields,reactivity levels and selectivity towards"metgas"were investigated.Running CSDRM at a temperature of at least 800℃,a pressure of 1 bar and under a feed composition where CO2-H2O/CH4 is around 1.0,are optimum conditions for the theoretical production of"metgas"while minimizing C(S)formation for longer experimental catalytic runs.A second part of this work presents a review of the recent progresses in the design of(principally)Ni-based catalysts along with some mechanistic and kinetic modeling aspects for the targeted CSDRM reaction.As compared to noble metals,their high availability,low cost and good intrinsic activity levels are main reasons for increasing research dedications in understanding deactivation potentials and providing amelioration strategies for further development.Deactivation causes and main orientations towards designing deactivationresistant supported Ni nanoparticles are clearly addressed and analyzed.Reported procedures based on salient catalytic features(i.e.,acidity/basicity character,redox properties,oxygen mobility,metal-support interaction)and recently employed innovative tactics(such as confinement within mesoporous systems,stabilization through core shell structure展开更多
Steam reforming of methanol was carried out on the copper-silica aerogel catalyst.The effects of reaction temperature,feed rate,water to methanol molar ratio and carrier gas flowrate on the H_2 production rate and CO ...Steam reforming of methanol was carried out on the copper-silica aerogel catalyst.The effects of reaction temperature,feed rate,water to methanol molar ratio and carrier gas flowrate on the H_2 production rate and CO selectivity were investigated.M ethanol conversion was increased considerably in the range of about 240-300,after which it increased at a slightly lower rate.The used feed flowrate,steam to methanol molar ratio and carrier gas flowwere 1.2-9.0 m L/h,1.2-5.0 and 20-80 m L/min,respectively.Reducing the feed flowrate increased the H_2 production rate.It was found that an increase in the water to methanol ratio and decreasing the carrier gas flowrate slightly increases the H2production rate.Increasing the water to methanol ratio causes the lowest temperature in which CO formation was observed to rise,so that for the ratio of 5.0 no CO formation was detected in temperatures lower than 375℃.In all conditions,by approaching the complete conversion,increasing the main product concentration,increasing the temperature and contact time,and decreasing the steam to methanol ratio,the CO selectivity was increased.These results suggested that CO was formed as a secondary product through reverse water-gas shift reaction and did not participate in the methanol steam reforming reaction mechanism.展开更多
Indium oxide(In_2O_3) has demonstrated to be an effective non-noble metal catalyst for methanol steam reforming reaction(MSR).However, the reaction mechanism of MSR and crucial structure-activity relations determining...Indium oxide(In_2O_3) has demonstrated to be an effective non-noble metal catalyst for methanol steam reforming reaction(MSR).However, the reaction mechanism of MSR and crucial structure-activity relations determining the catalytic performance of In_2O_3 are still not fully understood yet. Using density functional theory(DFT) calculation, we systematically investigate the MSR process over a high-index In_2O_3(211) and a favoured catalytic cycle of MSR is determined. The results show that In_2O_3(211) possesses excellent dehydrogenation and oxidizing ability, on which CH_3 OH can readily adsorb on the In4 c site and be easily activated by the reactive lattice oxygens, resulting in a total oxidation into CO_2 rather than CO, while the H_2 formation through surface H–H coupling limits the overall MSR activity because of the strong H adsorption on the two-coordinated lattice O(O_(2c)). Our analyses show that the relatively inert three-coordinated lattice O(O_(3c)) could play an important catalytic role. To uncover the influence of the local coordination of surface In atoms and lattice O on the catalytic activity, we evaluate the activity trend of several types of In_2O_3 surfaces including(211),(111), and(100) by examining the rate-limiting, which reveals the following activity order:(211)>(111)>(100). These findings provide an in-depth understanding on the MSR reaction mechanism over In_2O_3 catalysts and some basic structure-activity relations at the atomic scale, could facilitate the rational design of In_2O_3-based catalysts for MSR by controlling the local coordination environment of surface active sites.展开更多
基金supported by the Cultivation Project of Major Achievements Transformation of Sichuan Provincial Education Department(#14CZ0005)supported by the Natural Science Foundation of China(#21406184)
基金Supported by Carburos Metálicos-Air Products Group (Project CEN-2008-1027,Program Ingenio 2010,CDTI)
文摘The decomposition and CO2 reforming of methane,respectively,are promising alternatives to industrial steam methane reforming. In recent years,research has been focused on the development of catalysts that can operate without getting deactivated by carbon deposition,where,in particular,carbon catalysts have shown positive results. In this work,the role of carbon materials in heterogeneous catalysis is assessed and publications on methane decomposition and CO2 reforming of methane over carbon materials are reviewed. The influence of textural properties(BET surface area and micropore volume,etc.) and oxygen surface groups on the catalytic activity of carbon materials are discussed. In addition,this review examines how activated carbon and carbon black catalysts,which are the most commonly used carbon catalysts,are deactivated. Characteristics of the carbon deposits from methane are discussed and the influence of the reactivity to CO2 of fresh carbon and carbonaceous deposits for high and steady conversion during CO2 reforming of CH4 are also considered.
基金financial support through the SOL-CARE(Energy-065,2016–2019)project(JC-ENERGY-2014 first call)。
文摘Nowadays,combined steam and dry reforming of methane(CSDRM)is viewed as a new alternative for the production of high-quality syngas(termed as"metgas",H2:CO of 2.0)suitable for subsequent synthesis of methanol,considered as a promising renewable energy vector to substitute fossil fuel resources.Adequate operation conditions(molar feed composition,temperature and pressure)are required for the sole production of"metgas"while achieving high CH4,CO2 and H2O conversion levels.In this work,thermodynamic equilibrium analysis of CSDRM has been performed using Gibbs free energy minimization where;(i)the effect of temperature(range:200-1000℃),(ii)feed composition(stoichiometric ratio as compared to a feed under excess steam or excess carbon dioxide),(iii)pressure(range:1-20 bar)and,(iv)the presence of a gaseous diluent on coke yields,reactivity levels and selectivity towards"metgas"were investigated.Running CSDRM at a temperature of at least 800℃,a pressure of 1 bar and under a feed composition where CO2-H2O/CH4 is around 1.0,are optimum conditions for the theoretical production of"metgas"while minimizing C(S)formation for longer experimental catalytic runs.A second part of this work presents a review of the recent progresses in the design of(principally)Ni-based catalysts along with some mechanistic and kinetic modeling aspects for the targeted CSDRM reaction.As compared to noble metals,their high availability,low cost and good intrinsic activity levels are main reasons for increasing research dedications in understanding deactivation potentials and providing amelioration strategies for further development.Deactivation causes and main orientations towards designing deactivationresistant supported Ni nanoparticles are clearly addressed and analyzed.Reported procedures based on salient catalytic features(i.e.,acidity/basicity character,redox properties,oxygen mobility,metal-support interaction)and recently employed innovative tactics(such as confinement within mesoporous systems,stabilization through core shell structure
文摘Steam reforming of methanol was carried out on the copper-silica aerogel catalyst.The effects of reaction temperature,feed rate,water to methanol molar ratio and carrier gas flowrate on the H_2 production rate and CO selectivity were investigated.M ethanol conversion was increased considerably in the range of about 240-300,after which it increased at a slightly lower rate.The used feed flowrate,steam to methanol molar ratio and carrier gas flowwere 1.2-9.0 m L/h,1.2-5.0 and 20-80 m L/min,respectively.Reducing the feed flowrate increased the H_2 production rate.It was found that an increase in the water to methanol ratio and decreasing the carrier gas flowrate slightly increases the H2production rate.Increasing the water to methanol ratio causes the lowest temperature in which CO formation was observed to rise,so that for the ratio of 5.0 no CO formation was detected in temperatures lower than 375℃.In all conditions,by approaching the complete conversion,increasing the main product concentration,increasing the temperature and contact time,and decreasing the steam to methanol ratio,the CO selectivity was increased.These results suggested that CO was formed as a secondary product through reverse water-gas shift reaction and did not participate in the methanol steam reforming reaction mechanism.
基金supported by the National Natural Science Foundation of China(21333003,21622305)Young Elite Scientist Sponsorship Program by China Association for Science and Technology(YESS20150131)+1 种基金"Shu Guang"project supported by Shanghai Municipal Education Commission and Shanghai Education Development Foundation(13SG30)the Fundamental Research Funds for the Central Universities(WJ616007)
文摘Indium oxide(In_2O_3) has demonstrated to be an effective non-noble metal catalyst for methanol steam reforming reaction(MSR).However, the reaction mechanism of MSR and crucial structure-activity relations determining the catalytic performance of In_2O_3 are still not fully understood yet. Using density functional theory(DFT) calculation, we systematically investigate the MSR process over a high-index In_2O_3(211) and a favoured catalytic cycle of MSR is determined. The results show that In_2O_3(211) possesses excellent dehydrogenation and oxidizing ability, on which CH_3 OH can readily adsorb on the In4 c site and be easily activated by the reactive lattice oxygens, resulting in a total oxidation into CO_2 rather than CO, while the H_2 formation through surface H–H coupling limits the overall MSR activity because of the strong H adsorption on the two-coordinated lattice O(O_(2c)). Our analyses show that the relatively inert three-coordinated lattice O(O_(3c)) could play an important catalytic role. To uncover the influence of the local coordination of surface In atoms and lattice O on the catalytic activity, we evaluate the activity trend of several types of In_2O_3 surfaces including(211),(111), and(100) by examining the rate-limiting, which reveals the following activity order:(211)>(111)>(100). These findings provide an in-depth understanding on the MSR reaction mechanism over In_2O_3 catalysts and some basic structure-activity relations at the atomic scale, could facilitate the rational design of In_2O_3-based catalysts for MSR by controlling the local coordination environment of surface active sites.
