化学链甲烷氧化偶联界面反应路径和晶格氧传递的分子动力学模拟  

Surface reaction and lattice oxygen transfer in chemical looping oxidative coupling of methane:Molecular dynamics simulations

作　　者：李婉莹 陈良勇[1] LI Wanying;CHEN Liangyong(Key Laboratory of Energy Thermal Conversion and Control,School of Energy and Environment,Southeast University,Nanjing 210096,China)

机构地区：[1]东南大学能源与环境学院能源转换及其过程测控教育部重点实验室,江苏南京210096

出　　处：《燃料化学学报（中英文）》2024年第6期820-830,共11页Journal of Fuel Chemistry and Technology

基　　金：国家自然科学基金(52076042)资助。

摘　　要：本研究采用分子动力学模拟的方法计算八种金属氧化物催化剂-载氧体CL-OCM反应性能,并对性能最优的Mn_(2)O_(3)开展反应时间和颗粒尺寸的研究。结果表明,适当延长反应时间有利于提高C_(2)H_(4)选择性;C/O=1是Mn_(2)O_(3)的理想尺寸。基于以上结果分析了Mn_(2)O_(3)CL-OCM界面反应路径和晶格氧传递问题,以揭示反应机理。CH_(3)^(*)气相二聚化生成C_(2)H6的是CL-OCM最主要的碳偶联路径。除此之外,还存在两条碳偶联路径,均由CH2^(*)引发。CH_(3)^(*)与OH^(*)表面结合生成甲醇是CL-OCM副反应的先决步骤,抑制甲醇生成是提高CL-OCM反应C_(2)选择性的关键。晶格氧存在转化,表面晶格氧是甲烷活化的活性氧。晶格氧数量差异及体相晶格氧迁移阻力差异是导致CH_(4)转化率和C_(2)选择性不同的主要原因。该研究为CL-OCM催化剂-载氧体的机理探究提供新的方法。Chemical looping oxidative coupling of methane(CL-OCM)is a promising methodology for ethylene production from methane.This article utilizes molecular dynamic(MD)simulation to assess the performance of eight metal oxide catalytic oxygen carriers in CL-OCM reactions.It also investigates the impact of reaction time and particle size on the efficiency of the most effective Mn_(2)O_(3) COC.The results indicate that extending the reaction time appropriately enhances C_(2)H_(4) selectivity and a C/O ratio of 1 is found to be the optimal size for Mn_(2)O_(3)-based CLOCM.Furthermore,surface reactions and lattice oxygen transfer are analyzed by MD simulation in Mn_(2)O_(3)-based CL-OCM,providing deeply insights into the reaction mechanism.The findings reveal that the gas-phase dimerization of CH_(3)^(*)to form C_(2)H6 serves as the primary carbon coupling pathway in CL-OCM.In addition,there are two other carbon coupling pathways,both initiated by CH2^(*).Methanol formation through surface combination of CH_(3)^(*)and OH^(*)represents an initial step in CL-OCM side reactions.Therefore,inhibiting methanol formation is crucial for enhancing C_(2) selectivity in CL-OCM.There exists a transformation of lattice oxygen and surface lattice oxygen plays a key role in methane activation.The quantity of lattice oxygen and difference in bulk lattice oxygen migration resistance are major factors influencing variations CH_(4) conversion and C_(2) selectivity.This study provides a new way to reaction mechanism exploration related to CL-OCM catalytic oxygen carriers.

关 键 词：化学链甲烷氧化偶联 催化剂-载氧体 分子动力学模拟 界面反应 晶格氧 

分 类 号：TQ038[化学工程]