CH_(4)和CO_(2)共转化反应机理研究进展  

Progress in the mechanism of CH_(4)and CO_(2)co-conversion reactions

作　　者：成昊霖 年瑶 韩优[1,2] CHENG Haolin;NIAN Yao;HAN You(College of Chemical Engineering,Tianjin University,Tianjin 300072,China;Haihe Laboratory of Sustainable Chemical Transformations,Tianjin 300192,China)

机构地区：[1]天津大学化工学院,天津300072 [2]物质绿色创造与制造海河实验室,天津300192

出　　处：《化工进展》2024年第1期60-75,共16页Chemical Industry and Engineering Progress

基　　金：国家自然科学基金(21978210,U20A20151);中国博士后科学基金(2022M722360);天津大学自主创新基金(2023XQM-0012)。

摘　　要：综述了CH_(4)和CO_(2)共转化生成合成气、乙酸和C2烃3种反应路径的反应步骤、关键中间体及反应产物选择性的影响因素。当生成合成气时,CH_(4)与CO_(2)的活化解离是关键步骤,催化剂载体表面为酸性或中性时反应遵循单功能机理,CH_(4)和CO_(2)在同一活性中心被活化,当载体为表面碱性时,CH_(4)和CO_(2)遵循双功能机理,在不同活性中心被活化,通常双功能机理的催化效率更高。当生成乙酸时,C-C耦合过程应被重点关注,该过程中气相CO_(2)可能直接插入M—CH3键(Eley-Rideal机理)或先被吸附活化后再插入(Langmuir-Hinshelwood机理),后者反应能垒更低。当生成C2烃时,活性氧物种被认为是反应过程中的关键中间体,其可能来源于催化剂中的晶格氧或CO_(2)的活化与解离。因此,在催化剂表面构建多个独立活性位点,以分别对CH_(4)和CO_(2)进行多位点协同催化被认为是良好的催化剂改性策略。另外,先进的模拟计算方法和原位表征手段能够深入揭示反应过程中催化剂和反应中间体的动态演变过程及机理,从而为真实CH_(4)和CO_(2)共转化反应过程中催化剂的设计提供理论指导。This review provides a comprehensive overview of the reaction pathways involved in the coconversion of CH_(4)and CO_(2)to produce syngas,acetic acid,and C2 hydrocarbons.The focus is on elucidating the key reaction steps,intermediates,and the influencing factors on reaction selectivity.For the production of syngas,the activation and dissociation of CO_(2)and CH_(4)are identified as key steps.The mechanism depends on the acidity of the catalyst support.Acidic or neutral support follow a mono-functional mechanism,where both CH_(4)and CO_(2)are activated at the same active center.In contrast,a basic support leads to a bi-functional mechanism,involving the activation of CH_(4)and CO_(2)at different active centers.For acetic acid production,the C-C coupling process assumes to be significant.Two mechanisms are considered:the direct insertion of gasphase CO_(2)into the M—CH3 bond(Eley-Rideal mechanism),and the prior adsorption of CO_(2)followed by insertion(Langmuir-Hinshelwood mechanism),with a lower reaction energy barrier for the latter.For producing C2 hydrocarbons,reactive oxygen species are considered to be key intermediates in the reaction,which may be derived from the activation and dissociation of lattice oxygen or CO_(2)in the catalyst.To enhance the catalytic performance,constructing multiple active sites on the catalyst surface for the co-catalysis of CH_(4)and CO_(2)is regarded as a promising catalyst modification strategy.Furthermore,advanced simulation calculation methods and in-situ characterization techniques can help to reveal the dynamic evolution of reaction process and the catalytic mechanism,thus providing the theoretical guidance for the design of catalysts in the CH_(4)and CO_(2)co-conversion reaction.

关 键 词：甲烷 二氧化碳 反应机理 合成气 乙酸 C2烃 

分 类 号：O643.3[理学—物理化学] TQ426[理学—化学]