The roles of adsorbed oxygen and lattice oxygen on the surface of VPO catalyst for n butane selective oxidation were experimentally studied by using on line mass spectroscopy (MS) transient response measurement in a f...The roles of adsorbed oxygen and lattice oxygen on the surface of VPO catalyst for n butane selective oxidation were experimentally studied by using on line mass spectroscopy (MS) transient response measurement in a fixed bed micro reactor. The results showed that the lattice oxygen led to selective oxidation,while adsorbed oxygen led to deep oxidation. Gaseous oxygen could be adsorbed on the surface of the VPO catalyst and transformed to lattice oxygen but did not directly participate in selective oxidation. The diffusion of lattice oxygen from the bulk phase to the surface might be the rate controlling step of unsteady state oxidation when n butane selective oxidation and VPO catalyst re oxidation were performed separately.Increasing the diffusion rate of the lattice oxygen and usable lattice oxygen capacity in VPO catalyst could remarkably improve the reaction performance in a fixed bed reactor.展开更多
The structure and catalytic properties of SrTi0.9M0.1O3- δ (M=Mg,Al, Zr) perovskite type catalysts for oxidative coupling of methane (OCM) have been studied by using X ray diffraction (XRD),X ray photoelectron spectr...The structure and catalytic properties of SrTi0.9M0.1O3- δ (M=Mg,Al, Zr) perovskite type catalysts for oxidative coupling of methane (OCM) have been studied by using X ray diffraction (XRD),X ray photoelectron spectroscopy (XPS) and temperature programmed desorption of oxygen(O2 TPD) methods. It has been shown that doping the cations of lower valence (e.g. Mg2+ , Al3+ ) to the B site of SrTi0.9M0.1O3- δ perovskite type catalysts results in the higher content of adsorbed oxygen species on the surface of catalysts and thus higher C2 selectivity for OCM reaction. It is suggested that the oxygen vacancies of SrTi0.9M0.1O3- δ (M=Mg, Al, Zr) perovskite type catalysts are the sites responsible for oxygen activation, and the adsorbed oxygen species on the surface of SrTi0.9M0.1O3- δ catalysts are the main active species for OCM reaction.展开更多
Nanometer perovskite-type oxides MgTiO3,CaTiO3,SrTiO3 were prepared using tetrabutyl titanate,alkaline earth metal nitrates as raw materials by sol-gel method.The samples were characterized by thermogravimetry-differe...Nanometer perovskite-type oxides MgTiO3,CaTiO3,SrTiO3 were prepared using tetrabutyl titanate,alkaline earth metal nitrates as raw materials by sol-gel method.The samples were characterized by thermogravimetry-differential thermal(TG-DTA),X-ray diffraction(XRD),UV-Vis spectrophotometer(UV-Vis)and X-ray photoelectron spectroscopy(XPS).Using methylene blue as a degradation target,we studied that calcination temperature had an impact on photocatalytic activity of three different photocatalysts.Through the photocatalytic degradation of methylene blue,photocatalytic activity of the three perovskite-type catalysts was compared.The results showed that different crystal structure resulted in different temperature of optimum activity.The temperature of best photocatalytic activity for MgTiO3 was 700 ℃,CaTiO3 and SrTiO3 were 800 ℃.In the above-mentioned catalyst,CaTiO3 had the highest photocatalytic activity.XPS analysis and catalytic reaction with O2 show that the surface oxygen absorbed capacity is the most important factor which has an influence on photocatalytic activity of three perovskite-type photocatalysts.展开更多
基金国家自然科学基金委中国石油化工集团公司联合资助重大基金项目 (No 2 9792 0 70 )~~
文摘The roles of adsorbed oxygen and lattice oxygen on the surface of VPO catalyst for n butane selective oxidation were experimentally studied by using on line mass spectroscopy (MS) transient response measurement in a fixed bed micro reactor. The results showed that the lattice oxygen led to selective oxidation,while adsorbed oxygen led to deep oxidation. Gaseous oxygen could be adsorbed on the surface of the VPO catalyst and transformed to lattice oxygen but did not directly participate in selective oxidation. The diffusion of lattice oxygen from the bulk phase to the surface might be the rate controlling step of unsteady state oxidation when n butane selective oxidation and VPO catalyst re oxidation were performed separately.Increasing the diffusion rate of the lattice oxygen and usable lattice oxygen capacity in VPO catalyst could remarkably improve the reaction performance in a fixed bed reactor.
文摘The structure and catalytic properties of SrTi0.9M0.1O3- δ (M=Mg,Al, Zr) perovskite type catalysts for oxidative coupling of methane (OCM) have been studied by using X ray diffraction (XRD),X ray photoelectron spectroscopy (XPS) and temperature programmed desorption of oxygen(O2 TPD) methods. It has been shown that doping the cations of lower valence (e.g. Mg2+ , Al3+ ) to the B site of SrTi0.9M0.1O3- δ perovskite type catalysts results in the higher content of adsorbed oxygen species on the surface of catalysts and thus higher C2 selectivity for OCM reaction. It is suggested that the oxygen vacancies of SrTi0.9M0.1O3- δ (M=Mg, Al, Zr) perovskite type catalysts are the sites responsible for oxygen activation, and the adsorbed oxygen species on the surface of SrTi0.9M0.1O3- δ catalysts are the main active species for OCM reaction.
文摘Nanometer perovskite-type oxides MgTiO3,CaTiO3,SrTiO3 were prepared using tetrabutyl titanate,alkaline earth metal nitrates as raw materials by sol-gel method.The samples were characterized by thermogravimetry-differential thermal(TG-DTA),X-ray diffraction(XRD),UV-Vis spectrophotometer(UV-Vis)and X-ray photoelectron spectroscopy(XPS).Using methylene blue as a degradation target,we studied that calcination temperature had an impact on photocatalytic activity of three different photocatalysts.Through the photocatalytic degradation of methylene blue,photocatalytic activity of the three perovskite-type catalysts was compared.The results showed that different crystal structure resulted in different temperature of optimum activity.The temperature of best photocatalytic activity for MgTiO3 was 700 ℃,CaTiO3 and SrTiO3 were 800 ℃.In the above-mentioned catalyst,CaTiO3 had the highest photocatalytic activity.XPS analysis and catalytic reaction with O2 show that the surface oxygen absorbed capacity is the most important factor which has an influence on photocatalytic activity of three perovskite-type photocatalysts.
