Mn/W催化剂上甲烷氧化偶联反应机理的Monte Carlo模拟

Reaction mechanism of oxidative coupling of methane over Mn/W catalyst based on Monte Carlo simulations

通过对Mn-Na2WO4/SiO2催化剂的甲烷氧化偶联反应机理进行初步研究,以Mn/W双金属活性中心为基础,分析了CH4和O2共进料氧化偶联制C2烃的反应模型,并采用Monte Carlo方法对该反应的微观过程进行模拟,在与实验相近的条件下,得到了较准确的模拟结果.在模拟实验中,考察了活性位规模和原料气组成对反应结果的影响以及反应过程中表面吸附物种的变化规律.结果表明:活性位规模增大将减缓表面反应的速度,而不同进料烷氧比将对甲烷转化率以及C2烃收率产生影响;同时在对表面吸附物种的考察中发现,反应末期催化剂催化活性不高与晶格氧的补充不足有关,而C2H6和C2H4的反应更多地发生在气相主体.

The mechanism of oxidative coupling of methane over Mn-Na2WO4/SiO2 catalyst is studied.Base on the double-activity-site Mn / W catalytic centers,the reaction model of methane and oxygen co-feeding to product C2 hydrocarbon was simulated by means of Monte Carlo approach.The computer simulation results are in good agreement with experiment under similar conditions,which indicate that the complex surface model presented is reasonable.The influence of grid size and feeding ratio of methane to oxygen are also taken into account.Further analysis of the surface coverage with virtual reaction time is also discussed in the paper.The results show that the surface reaction is restrained by enlargement of grid size;feeding ratio of NCH4/NO2 has significant effect on the conversion of methane and selectivity of C2 hydrocarbon.Base on the research of the surface coverage with virtual reaction time,short of lattice oxygen supplement results in low activity of the catalyst;most of the oxidative reaction of ethane and ethylene occur in the gas-phase.