磷酸盐的添加对甲烷氧化偶联反应镧基催化剂的影响

Influence of Phosphate on La-based Catalysts for Oxidative Coupling of Methane

采用柠檬酸法制备了不同含量磷酸盐修饰的镧基催化剂,考察了磷酸盐的添加对镧基催化剂甲烷氧化偶联反应(OCM)活性的影响,并借助X射线衍射(XRD)、O_2-程序升温脱附(O_2-TPD)及X射线光电子能谱(XPS)等手段对催化剂的理化性质进行了表征.结果表明,随着磷酸盐加入量的增大,催化剂样品的粒径逐渐减少,催化剂的物相由La_2O_3向La_3PO_7和LaPO_4逐步转变.当催化剂的物相由La_2O_3和适量的La_3PO_7构成时,催化剂具有较多的表面缺陷位点数和较大的亲电氧物种/晶格氧物种比值,并呈现出良好的OCM反应性能.

A series of La-based catalysts promoted by different contents of PO_4^（3-）was synthesized by the citric acid method and their catalytic performance for oxidative coupling of methane（OCM）was investigated to clarify the effect of PO_4^（3-）on La-based catalyst.With characterizations such as X-ray powder diffraction（XRD）,O_2-temperature programmed desorption（O_2-TPD）and X-ray photoelectron spectroscopy（XPS）,we studied the physicochemical properties of the catalysts.The results showed that the phases of the catalysts were changed from La_2O_3,La_3PO_7 to La PO_4 along with the decreased size when phosphate added.If the catalyst was composed of two phases（La_2O_3 and right amount of La_3PO_7）,it showed better performances in OCM,which corresponded to the more quantities of surface defect sites and the larger ratio of electrophilic oxygen species/lattice oxygen species than other samples.