The effects of Ce-ZrOx, Ce-LaOx, Ce-SmOx and Ce-GdOx additions to Rh/Al2O3 catalysts on methane autothermal re-forming were investigated. Activity tests showed that the addition of Ce-ZrOx could significantly reduce t...The effects of Ce-ZrOx, Ce-LaOx, Ce-SmOx and Ce-GdOx additions to Rh/Al2O3 catalysts on methane autothermal re-forming were investigated. Activity tests showed that the addition of Ce-ZrOx could significantly reduce the concentration of CO in reformats. When Ce/Zr atomic ratio was 1：1, C%.5Zr0.5O2 solid solution with high thermal stability was obtained, which could effec- tively improve the catalytic performance effectively. The additives of alkaline-earth metals （Mg, K and Ca） on the catalytic properties were also studied. The results of experiments showed that the addition of MgO to Rh/Ce0.5Zr0.5O2/Al2O3 improved the stable per- formance and the carbon resistance of the catalyst. The optimized catalyst was 0.1%Rh/2.0%MgO/40%Ce0.5Zr0.5O2/Al2O3, which showed a highly stable performance for methane autothermal reforming.展开更多
A series of rhodium-modified Mo-K/Al2O3 catalyst samples was prepared by varying the rhodium loading between 0 and 1.0 wt% and maintaining molybdenum and potassium contents as constants.The structures of the samples w...A series of rhodium-modified Mo-K/Al2O3 catalyst samples was prepared by varying the rhodium loading between 0 and 1.0 wt% and maintaining molybdenum and potassium contents as constants.The structures of the samples were charaterized by techniques of XRD.LRS.TPR,XPS and EXAFS and correlated to the catalytic properties of the samples for alcohol synthesis from synthesis gas,It was found that.in the oxidic rhodium-modified samples.a strong interaction of the rhodium modifier with the supported K-Mo-O species occurs.This interaction facilitates the sulfidation and reduction of the supported oxo-molybdenum and leads to a decrease in the size of the molybdenum species and stabilization of the cationic rhodium species on the samples during sulfidation.Upon sulfidation.The sulfided molybdenum species in the rhodium-free sample is manly present as large pateches of MoS2-like slabs with their basal sulfur planes interacting with the support surface.With the modirication of rhodium to the samples.The supported MoS2-like species becomes highly dispersed.as revealed by the decrease in the average size of the sulfided molybdenum species.The interaction of the rhodium species with the molybdenum somponent may cause the basal planes of the MoS2-like species to become oriented perpendicular to the support surface due to favorable bonding of the MoS2edge planes to the support through Mo-O-Al bonds.In comparison with the sulfided sample free of rhodium.the properties of the rhodium-modified samples for alcohol synthesis from synthesis gas are much improved.It most probably results from the synergic interaction of the rhodium with the molybdenum species that gives rise to the appearance of the catalytically active surfaces of sites.The co-existence of cationic and metallic rhodium stabilized by this interaction may be responsible for the increased selectivity for the formation of C2+ alcohols.展开更多
Local structures of the molybdenum sulfide species in the sultided Rh-Mo-K/Al2O3 catalysts with various rhodium loadings have been investigated by XAFS.From the fitting results.the Mo-Mo coordination number for the sa...Local structures of the molybdenum sulfide species in the sultided Rh-Mo-K/Al2O3 catalysts with various rhodium loadings have been investigated by XAFS.From the fitting results.the Mo-Mo coordination number for the sample free of rhodium(ca.3.7) is similar to that for the crystalline MoS2,indicating that the supported sulfided molybdenum species mainly present as large pateches of MoS2-like slabs.For the rhodium-modified samples,however,the amplitudes of the Mo-S and Mo-Mo coordination shells are sharply reduced,revealing a high dispersion of the MoS2-like species in the catalysts,The scheme of the microstructures of the sulfided molybdenum species stabilized on the alumina support is discussed based upon the analysis of the EXAFS data.展开更多
基金supported by National Natural Science Foundation of China(21076206,21376237)National Key Foundational Research Project(973) of China(2010CB732302)National High Technology Research and Development Program(863) of China(2011AA050706)
文摘The effects of Ce-ZrOx, Ce-LaOx, Ce-SmOx and Ce-GdOx additions to Rh/Al2O3 catalysts on methane autothermal re-forming were investigated. Activity tests showed that the addition of Ce-ZrOx could significantly reduce the concentration of CO in reformats. When Ce/Zr atomic ratio was 1：1, C%.5Zr0.5O2 solid solution with high thermal stability was obtained, which could effec- tively improve the catalytic performance effectively. The additives of alkaline-earth metals （Mg, K and Ca） on the catalytic properties were also studied. The results of experiments showed that the addition of MgO to Rh/Ce0.5Zr0.5O2/Al2O3 improved the stable per- formance and the carbon resistance of the catalyst. The optimized catalyst was 0.1%Rh/2.0%MgO/40%Ce0.5Zr0.5O2/Al2O3, which showed a highly stable performance for methane autothermal reforming.
文摘A series of rhodium-modified Mo-K/Al2O3 catalyst samples was prepared by varying the rhodium loading between 0 and 1.0 wt% and maintaining molybdenum and potassium contents as constants.The structures of the samples were charaterized by techniques of XRD.LRS.TPR,XPS and EXAFS and correlated to the catalytic properties of the samples for alcohol synthesis from synthesis gas,It was found that.in the oxidic rhodium-modified samples.a strong interaction of the rhodium modifier with the supported K-Mo-O species occurs.This interaction facilitates the sulfidation and reduction of the supported oxo-molybdenum and leads to a decrease in the size of the molybdenum species and stabilization of the cationic rhodium species on the samples during sulfidation.Upon sulfidation.The sulfided molybdenum species in the rhodium-free sample is manly present as large pateches of MoS2-like slabs with their basal sulfur planes interacting with the support surface.With the modirication of rhodium to the samples.The supported MoS2-like species becomes highly dispersed.as revealed by the decrease in the average size of the sulfided molybdenum species.The interaction of the rhodium species with the molybdenum somponent may cause the basal planes of the MoS2-like species to become oriented perpendicular to the support surface due to favorable bonding of the MoS2edge planes to the support through Mo-O-Al bonds.In comparison with the sulfided sample free of rhodium.the properties of the rhodium-modified samples for alcohol synthesis from synthesis gas are much improved.It most probably results from the synergic interaction of the rhodium with the molybdenum species that gives rise to the appearance of the catalytically active surfaces of sites.The co-existence of cationic and metallic rhodium stabilized by this interaction may be responsible for the increased selectivity for the formation of C2+ alcohols.
文摘Local structures of the molybdenum sulfide species in the sultided Rh-Mo-K/Al2O3 catalysts with various rhodium loadings have been investigated by XAFS.From the fitting results.the Mo-Mo coordination number for the sample free of rhodium(ca.3.7) is similar to that for the crystalline MoS2,indicating that the supported sulfided molybdenum species mainly present as large pateches of MoS2-like slabs.For the rhodium-modified samples,however,the amplitudes of the Mo-S and Mo-Mo coordination shells are sharply reduced,revealing a high dispersion of the MoS2-like species in the catalysts,The scheme of the microstructures of the sulfided molybdenum species stabilized on the alumina support is discussed based upon the analysis of the EXAFS data.
基金Key Research and Development Program of Sichuan Science and Technology Department(2019YFS0513)National Natural Science Foundation of China(21962021)。
