红外光谱研究甲烷和氧与SrO-La2O3/CaO表面的相互作用

在甲烷氧化偶联（ＯＣＭ）反应条件下，用原位红外光谱研究ＳｒＯ－Ｌａ２Ｏ３／ＣａＯ催化剂，结果表明，晶格氧使甲深度氧化，Ｌａ２Ｏ３和ＣａＯ具有活泼的晶格氧，ＳｒＯ的晶格氧比较稳定，气相氧通过催化剂表面消耗掉的晶格氧，加速甲烷了深度氧化，另一方面，催化剂表面的碳酸根物种在氧气氛下分解，在Ｌａ２Ｏ３和ＬＣ催化剂中，催化剂表面Ｌａ２Ｏ２（ＣＯ３）的分解形成配位不饱和的晶格氧Ｏ＾２－，并为气相氧吸附提供氧空

A FT-IR Study on the Interaction of CH_4 and O_2 with the Surface of SrO-La_2O_3/CaO Catalysts

SrO-La2O3/CaO(SLC) catalysts have been found to be active for the oxidative coupling of methane (OCM), but the lattice oxygen of them is only active for total okidation as revealed by the studies of in - situ FT-IR on the interaction between CH4 and the oxide surface concerned.The results of an in - situ FT-IR study on the interaction of the milxture of CH4 and O2 with the catalyst surface show that the oxygen in gas phase can accelerate the total okidation of CH4 via replenishing the lattice oxygen consumed on one hand, and on the other hand, it will promote the decomposition of surface carbonates formed during the reaction. For La2O3 and LC catalysts, the decomposition of surface La2O2(CO3) carbonate results in the formation of coordination unsaturated oxygen species and oxygen vacancy, and then the oxygen in gas phase could be adsorbed on the oxygen vacancy and electron tranfer from coordination unsaturated oxygen species to the oxygen adspecies talles place to produce active oxygen species, probably in the form O2-, with the characteristic IR band at 1180cm-1. Meanwhile on the surfaces of CaO, SrO and SLC catalysts, although no any active oxygen species could be detected, the formation of c2H4 product stin is observed at high temperatures. Therefore, it is speculated that the decomposition of sarface carbonates directly leads to the formation of active oxygen species, O2-.