La_2O_3/BaCO_3上甲烷氧化偶联反应动力学与历程

KINETICS AND PATHWAY OF OXIDATIVE COUPLING OF METHANE OVER La_2O_3/BaCO_3 CATALYST

以8％La_2O_3/BaCO_3为催化剂,用无梯度反应器,在720～800℃温度范围内,通过改变甲烷与氧分压进行了一系列的甲烷氧化偶联反应动力学测量,确定了该反应的反应历程。乙烷和大部分CO_x(主要是CO_2)是甲烷氧化的一次产物。乙烯是乙烷串行反应的产物。用幂式动力学方程拟合动力学试验数据,估算了各步反应速度方程的动力学参数。还用脉冲反应技术与过渡应答技术证明了参与活化甲烷的是催化剂表面上的可逆吸附氧。

The reaction kinetics of the oxidative coupling of methane over a 8% La2O3/BaCO3 catalyst has been determined in a gradientless reactor by varying the partial pressure and residence time in the temperature range of 720-800℃. The reaction network for the title reaction is defined. The oxidation of methane yields directly ethane and great part of COX as primary products. Etbylene is consecutively formed from ethane dehydrogenation. Some of CO, is also formed from complete oxidation of ethane and ethylene. The overall kinetics of methane oxidation was determined by fitting the experimental data using linear regression analysis to power law rate equations according to the reaction scheme. Low oxygen pressure and high reaction temperature are favourable to the formation of ethane and ethylene, while high oxygen pressure and low reaction temperature favour the formation of CO,.In combination with the pulse reaction and transient response experiments, it is verified that the reversible adsorbed oxygen on the La2O3/BaCO3 catalyst is responsible for the activation of methane.