【摘要】 采用溶胶-凝胶法制备了纳米钙钛矿型复合氧化物SrTiO3催化剂,并用X射线粉末衍射、透射电子显微镜、原位电子自旋共振和程序升温表面反应等技术对催化剂进行了表征,测定了催化剂对甲烷氧化偶联(OCM)反应的催化性能.结果表明,与相同组成的常规SrTiO3催化剂相比,纳米SrTiO3催化剂具有较好的低温(～650℃)催化性能.通过增大Sr/Ti比可进一步优化纳米SrTiO3的催化性能.纳米SrTiO3催化剂表面的吸附氧物种和F中心均具有活化及催化甲烷分子生成C2烃产物的活性,但吸附氧物种易使OCM反应中间体和产物深度氧化,而F中心具有低温活化甲烷分子及高选择性生成C2烃产物的特性.纳米氧化物粒子因表面原子配位不饱和(配位数低),其表面存在较多的F中心。更多还原

【Abstract】 The perovskite-type nanosized SrTiO3 catalyst was prepared by the sol-gel method.Its structure was characterized by X-ray diffraction,transmission electron microscopy,in situ electron spin resonance,and temperature-programmed surface reaction techniques,and its catalytic performance for oxidative coupling of methane(OCM) was measured in a microreactor.The nanosized SrTiO3 catalyst exhibited better catalytic performance for OCM reaction at low temperature(～650 ℃) than the conventional SrTiO3 catalyst with the same composition.The catalytic performance of the nanosized SrTiO3 catalyst was improved with the increase of Sr/Ti atomic ratios.Both the surface adsorption oxygen species and F centers of the perovskite-type complex oxide could activate CH4 and form C2 hydrocarbons.However,the oxygen species on the catalyst surface eventually resulted in the complete oxidation of the reaction intermediates and C2 hydrocarbons.In contrast,the F centers could activate CH4 at lower temperature and led to formation of C2 hydrocarbons with higher selectivity.The better catalytic performance of the nanosized SrTiO3 catalyst was correlated to the higher concentration of F centers owing to low coordination numbers on the nanosized oxide particles.更多还原