Cu-based catalysts have been extensively used in methanol steam reforming(MSR)reactions because of their low cost and high effi ciency.ZnO is often used in commercial Cu-based catalysts as both a structural and an ele...Cu-based catalysts have been extensively used in methanol steam reforming(MSR)reactions because of their low cost and high effi ciency.ZnO is often used in commercial Cu-based catalysts as both a structural and an electronic promoter to stabilize metal Cu nanoparticles and modify metal–support interfaces.Still,the further addition of chemical promoters is essential to further enhance the MSR reaction performance of the Cu/ZnO catalyst.In this work,CeO_(2)-doped Cu/ZnO catalysts were prepared using the coprecipitation method,and the eff ects of CeO_(2)on Cu-based catalysts were systematically investigated.Doping with appropriate CeO_(2)amounts could stabilize small Cu nanoparticles through a strong interaction between CeO_(2)and Cu,leading to the formation of more Cu+–ZnO x interfacial sites.However,higher CeO_(2)contents resulted in the formation of larger Cu nanoparticles and an excess of Cu+–CeO x interfacial sites.Consequently,the Cu/5CeO_(2)/ZnO catalyst with maximal Cu–ZnO interfaces exhibited the highest H 2 production rate of 94.6 mmolH2/(gcat·h),which was 1.5 and 10.2 times higher than those of Cu/ZnO and Cu/CeO_(2),respectively.展开更多
Cu/ZrO2 catalysts for methanol synthesis from CO2/H2 were respectively prepared by deposition coprecipitation （DP） and solid state reaction （SR） methods. There is an intimate interaction between copper and zirconi...Cu/ZrO2 catalysts for methanol synthesis from CO2/H2 were respectively prepared by deposition coprecipitation （DP） and solid state reaction （SR） methods. There is an intimate interaction between copper and zirconia, which strongly affects the reduction property and catalytic performance of the catalysts. The stronger the interaction, the lower the reduction temperature and the better the performance of the catalysts. Surface area, pore structure and crystal structure of the catalysts are mainly controlled by preparation methods and alkalinity of synthesis system. The conversion of CO2 and selectivity of methanol are higher for DP catalysts than for SP catalysts.展开更多
Cu/CeO2-ZrO2 catalysts for water-gas shift （WGS） reaction were prepared with co-precipitation method, and the influence of ZrO2 content on the catalytic structure and properties was investigated by the techniques of...Cu/CeO2-ZrO2 catalysts for water-gas shift （WGS） reaction were prepared with co-precipitation method, and the influence of ZrO2 content on the catalytic structure and properties was investigated by the techniques of N2 physical adsorption analysis, XRD and H2-TPR. The results indicate that the BET surface areas of the catalysts are increased in varying degrees due to the presence of ZrO2. With increasing ZrO2 content, the pore size distribution is centered on 1.9 nm. ZrO2 can efficiently restrain the growth of Cu crystal particles. The appropriate amount of ZrO2 in the Cu/CeO2 catalysts can help the catalyst keep better copper dispersion in the WGS reaction, which can lead to both higher catalytic activity and better thermal stability. When ZrO2 content is 10% （atom fraction）, Cu/CeO2-Zr02 catalyst reaches a CO conversion rate of 73.7% at the reaction temperature of 200℃.展开更多
Cu/ZrO2/SiO2 are efficient catalysts for the selective hydrogenation of CO2 to CH3OH. In order to understand the role of ZrO2 in these mixed-oxides based catalysts, in situ X-ray absorption spectroscopy has been carri...Cu/ZrO2/SiO2 are efficient catalysts for the selective hydrogenation of CO2 to CH3OH. In order to understand the role of ZrO2 in these mixed-oxides based catalysts, in situ X-ray absorption spectroscopy has been carried out on the Cu and Zr K-edge. Under reaction conditions, Cu remains metallic, while Zr is present in three types of coordination environment associated with 1) bulk ZrO2, 2) coordinatively saturated and 3) unsaturated Zr(Ⅳ) surface sites. The amount of coordinatively unsaturated Zr surface sites can be quantified by linear combination fit of reference X-Ray absorption near edge structure (XANES) spectra and its amount correlates with CH3OH formation rates, thus indicating the importance of Zr(Ⅳ) Lewis acid surface sites in driving the selectivity toward CH3OH. This finding is consistent with the proposed mechanism, where CO2 is hydrogenated at the interface between the Cu nanoparticles that split H2 and Zr(Ⅳ) surface sites that stabilizes reaction intermediates.展开更多
A novel pH gradient methodology was used to synthesise a series of Cu–ZrO2 catalysts containing different quantities of Cu and Zr.All of the catalysts were highly selective to the desired product,γ-valerolactone, an...A novel pH gradient methodology was used to synthesise a series of Cu–ZrO2 catalysts containing different quantities of Cu and Zr.All of the catalysts were highly selective to the desired product,γ-valerolactone, and are considerably more stable than Cu–ZrO2 catalysts prepared by other co-precipitation methods for this reaction.Characterisation and further investigation of these catalysts by XRD, BET, SEM and XPS provided insight into the nature of the catalytic active site and the physicochemical properties that lead to catalyst stability.We consider the active site to be the interface between Cu/CuOxand ZrOx and that lattice Cu species assist with the dispersion of surface Cu through the promotion of a strong metal support interaction.This enhanced understanding of the active site and roles of lattice and surface Cu will assist with future catalyst design.As such, we conclude that the activity of Cu–ZrO2 catalysts in this reaction is dictated by the quantity of Cu–Zr interface sites.展开更多
A series of hybrid catalysts were made by physically mixing Cu-ZrO2 and γ-A12O3, for former it was modified with different loadings of La2O3 prepared by co-precipitation method. The catalysts were characterized by BE...A series of hybrid catalysts were made by physically mixing Cu-ZrO2 and γ-A12O3, for former it was modified with different loadings of La2O3 prepared by co-precipitation method. The catalysts were characterized by BET, XRD, N2O-adsorption, EXAFS, H2-TPR, NH3-TPD techniques and evaluated in the synthesis of dimethyl ether from syngas. The results show that La2O3 promoted catalysts displayed a significantly better catalytic performance compared with Cu-ZrO2#y-A12O3 catalyst in CO conversion and DME selectivity, and the optimum catalytic activity was obtained when the content of La2O3 was 12 wt%. The characterizations reveal that high copper dispersion, facile reducibility of copper particles and appropriate amount of acidic sites are responsible for the superior catalytic performance.展开更多
基金This work was supported by the National Key R&D Program of China(2022YFB3805504),National Natural Science Foundation of China(22078089)China Postdoctoral Science Foundation(2023M731081)+3 种基金Shanghai Pilot Program for Basic Research(22TQ1400100-7)the Basic Research Program of Science and Technology Commission of Shanghai Municipality(22JC1400600)Open Foundation of Shanghai Jiao Tong University Shaoxing Research Institute of Renewable Energy and Molecular Engineering(Grant No.JDSX2022046)Shanghai Super Postdoctoral Fellow.
文摘Cu-based catalysts have been extensively used in methanol steam reforming(MSR)reactions because of their low cost and high effi ciency.ZnO is often used in commercial Cu-based catalysts as both a structural and an electronic promoter to stabilize metal Cu nanoparticles and modify metal–support interfaces.Still,the further addition of chemical promoters is essential to further enhance the MSR reaction performance of the Cu/ZnO catalyst.In this work,CeO_(2)-doped Cu/ZnO catalysts were prepared using the coprecipitation method,and the eff ects of CeO_(2)on Cu-based catalysts were systematically investigated.Doping with appropriate CeO_(2)amounts could stabilize small Cu nanoparticles through a strong interaction between CeO_(2)and Cu,leading to the formation of more Cu+–ZnO x interfacial sites.However,higher CeO_(2)contents resulted in the formation of larger Cu nanoparticles and an excess of Cu+–CeO x interfacial sites.Consequently,the Cu/5CeO_(2)/ZnO catalyst with maximal Cu–ZnO interfaces exhibited the highest H 2 production rate of 94.6 mmolH2/(gcat·h),which was 1.5 and 10.2 times higher than those of Cu/ZnO and Cu/CeO_(2),respectively.
文摘Cu/ZrO2 catalysts for methanol synthesis from CO2/H2 were respectively prepared by deposition coprecipitation （DP） and solid state reaction （SR） methods. There is an intimate interaction between copper and zirconia, which strongly affects the reduction property and catalytic performance of the catalysts. The stronger the interaction, the lower the reduction temperature and the better the performance of the catalysts. Surface area, pore structure and crystal structure of the catalysts are mainly controlled by preparation methods and alkalinity of synthesis system. The conversion of CO2 and selectivity of methanol are higher for DP catalysts than for SP catalysts.
文摘Cu/CeO2-ZrO2 catalysts for water-gas shift （WGS） reaction were prepared with co-precipitation method, and the influence of ZrO2 content on the catalytic structure and properties was investigated by the techniques of N2 physical adsorption analysis, XRD and H2-TPR. The results indicate that the BET surface areas of the catalysts are increased in varying degrees due to the presence of ZrO2. With increasing ZrO2 content, the pore size distribution is centered on 1.9 nm. ZrO2 can efficiently restrain the growth of Cu crystal particles. The appropriate amount of ZrO2 in the Cu/CeO2 catalysts can help the catalyst keep better copper dispersion in the WGS reaction, which can lead to both higher catalytic activity and better thermal stability. When ZrO2 content is 10% （atom fraction）, Cu/CeO2-Zr02 catalyst reaches a CO conversion rate of 73.7% at the reaction temperature of 200℃.
基金E.L.,K.L.,P.W.,and S.T.are supported by the SCCER-Heat and Energy Storage program
文摘Cu/ZrO2/SiO2 are efficient catalysts for the selective hydrogenation of CO2 to CH3OH. In order to understand the role of ZrO2 in these mixed-oxides based catalysts, in situ X-ray absorption spectroscopy has been carried out on the Cu and Zr K-edge. Under reaction conditions, Cu remains metallic, while Zr is present in three types of coordination environment associated with 1) bulk ZrO2, 2) coordinatively saturated and 3) unsaturated Zr(Ⅳ) surface sites. The amount of coordinatively unsaturated Zr surface sites can be quantified by linear combination fit of reference X-Ray absorption near edge structure (XANES) spectra and its amount correlates with CH3OH formation rates, thus indicating the importance of Zr(Ⅳ) Lewis acid surface sites in driving the selectivity toward CH3OH. This finding is consistent with the proposed mechanism, where CO2 is hydrogenated at the interface between the Cu nanoparticles that split H2 and Zr(Ⅳ) surface sites that stabilizes reaction intermediates.
基金financially supported by the European Union FP7 NMP project NOVACAM (Novel cheap and abundant EU-Japan604319)
文摘A novel pH gradient methodology was used to synthesise a series of Cu–ZrO2 catalysts containing different quantities of Cu and Zr.All of the catalysts were highly selective to the desired product,γ-valerolactone, and are considerably more stable than Cu–ZrO2 catalysts prepared by other co-precipitation methods for this reaction.Characterisation and further investigation of these catalysts by XRD, BET, SEM and XPS provided insight into the nature of the catalytic active site and the physicochemical properties that lead to catalyst stability.We consider the active site to be the interface between Cu/CuOxand ZrOx and that lattice Cu species assist with the dispersion of surface Cu through the promotion of a strong metal support interaction.This enhanced understanding of the active site and roles of lattice and surface Cu will assist with future catalyst design.As such, we conclude that the activity of Cu–ZrO2 catalysts in this reaction is dictated by the quantity of Cu–Zr interface sites.
基金supported by the Ministry of Science and Technology of the People’s Republic of China (No. 2011BAD22B06)the Chinese Academy of Sciences (No. GJHZ1025,Y2010022,KGCX2-YW-329)
文摘A series of hybrid catalysts were made by physically mixing Cu-ZrO2 and γ-A12O3, for former it was modified with different loadings of La2O3 prepared by co-precipitation method. The catalysts were characterized by BET, XRD, N2O-adsorption, EXAFS, H2-TPR, NH3-TPD techniques and evaluated in the synthesis of dimethyl ether from syngas. The results show that La2O3 promoted catalysts displayed a significantly better catalytic performance compared with Cu-ZrO2#y-A12O3 catalyst in CO conversion and DME selectivity, and the optimum catalytic activity was obtained when the content of La2O3 was 12 wt%. The characterizations reveal that high copper dispersion, facile reducibility of copper particles and appropriate amount of acidic sites are responsible for the superior catalytic performance.
