甲烷在SrO-La_2O_3/CaO催化剂上的氧化偶联 Ⅲ.动力学处理及其反应机理

OXIDATIVE COUPLING OF METHANE OVER SrO-La_2O_3/CaO CATALYSTS Ⅲ.REACTION MECHANISM

动力学的比较研究发现,在20％La_2O_3/CaO(LC)催化剂中添加SrO(SLC),改变了甲烷氧化偶联的反应机制。根据前文的动力学实验结果,提出了简化的反应网络和几种反应机理,并且进行了动力学处理。结果表明,在LC催化剂上的甲烷氧化偶联满足Langmuir-Hin-shelwood机理,反应的活性氧物种为分子态吸附氧物种O_2~*,CO_x来源于[CH_3·]同气相分子氧的相互作用;而SLC催化剂的甲烷氧化偶联却满足修正的Rideal-Redox机理,反应的活性氧物种为表面氧物种O^-,CO_x由[CH_3·]同O^-的相互作用产生。

There were several differences in the reaction behavior and the formation of COX between the 20% La2O3/CaO(LC) catalyst and SrO promoted LC catalyst(SLC).In this work, several mechanisms were tested.It is found that the oxidative coupling of methane over the LC catalyst follows Langmuir-Hinshelwood mechanism and an adspecies of oxygen in its molecular form is active species, CO is a primary product and CO2 is the secondary product.While the reaction over the SLC catalyst follows a modified Rideal-Redox mechanism and an adspecies of oxygen in O- is active species, CO2 and CO come simultaneously from the reaction between CH3 and O-.