The structure and catalytic properties of SrTi1- xMgxO3- δ perovskite type catalysts for oxidative coupling of methane (OCM) have been studied by using X ray diffraction (XRD), X ray photoelectron spectroscopy (XPS) ...The structure and catalytic properties of SrTi1- xMgxO3- δ 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 (O2 TPD) methods. It has been shown that doping Mg2+ cations to the B site of SrTi1- xMgxO3- δ perovskite type catalysts results in the formation of oxygen vacancies in the lattices of oxide catalysts. With increasing the amount of Mg2+ doped in the B site of SrTi1- xMgxO3- δ , methane conversion and C2 selectivity first increase and then decrease remarkably. The SrTi1- xMgxO3- δ catalyst with x=0.1 has the highest methane conversion and C2 yield. It is suggested that the oxygen vacancies produced by Mg2+ cations doping are the sites responsible for oxygen activation, and the adsorbed oxygen species on the surface of SrTi1- xMgxO3- δ catalysts are the main active species for OCM reaction. However, the over high content of the adsorbed oxygen species on the surface results in the complete oxidation of methane. Introducing water steam into feedstock can improve the catalytic properties of SrTi1- xMgxO3- δ perovskite type catalysts for OCM reaction at lower temperature. The SrTi0.9Mg0.1O3- δ catalyst has the methane conversion of 28.0 % with C2 hydrocarbons selectivity of 36.8 % under reaction temperature of 550 ℃ .展开更多
文摘The structure and catalytic properties of SrTi1- xMgxO3- δ 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 (O2 TPD) methods. It has been shown that doping Mg2+ cations to the B site of SrTi1- xMgxO3- δ perovskite type catalysts results in the formation of oxygen vacancies in the lattices of oxide catalysts. With increasing the amount of Mg2+ doped in the B site of SrTi1- xMgxO3- δ , methane conversion and C2 selectivity first increase and then decrease remarkably. The SrTi1- xMgxO3- δ catalyst with x=0.1 has the highest methane conversion and C2 yield. It is suggested that the oxygen vacancies produced by Mg2+ cations doping are the sites responsible for oxygen activation, and the adsorbed oxygen species on the surface of SrTi1- xMgxO3- δ catalysts are the main active species for OCM reaction. However, the over high content of the adsorbed oxygen species on the surface results in the complete oxidation of methane. Introducing water steam into feedstock can improve the catalytic properties of SrTi1- xMgxO3- δ perovskite type catalysts for OCM reaction at lower temperature. The SrTi0.9Mg0.1O3- δ catalyst has the methane conversion of 28.0 % with C2 hydrocarbons selectivity of 36.8 % under reaction temperature of 550 ℃ .
