GPU加速密度泛函计算研究甲烷氧化偶联反应催化循环机制

This project focuses on the studies of the methane oxidative coupling reaction as catalyzed by lanthanum oxide-based catalysts, which are promising for industrial applications. Considering the involvement of both homogeneous and heterogeneous processes in this reaction as well as radical reaction processes, large metal oxide clusters displaying the typical surface structures of the catalyst will be constructed for realistic catalyst models. GPU-accelerated density functional theory calculations will be carried out to make reliable predictions. Together with the relevant experimental studies on the surface structures and catalytic mechanisms of these catalysts, catalytic activation mechanisms of methane by various surface active oxygen species as well as the further conversion mechanisms of the intermediates by catalytic and non-catatlytic routes will be thoroughly investigated. The flexibility of cluster-based density functional calculations will be explored, and the key reaction steps will also be studied using periodic slab model for comparison, enabling the construction of comprehensive and reliable catalytic mechanisms for this complex reaction. The effects of catalyst structures on the catalytic activity and product selectivity will be studied, and the effects of metal doping will be investigated for catalyst catalyst rational design. The project will be of great academic value and of general applicability for methane activation and conversion mechanisms on oxide catalysts, surface structures and reactivities of metal oxides, and complex catalytic reaction mechanisms for catalyst rational design.

本项目以具有重要应用价值的基于La2O3催化剂作用下的甲烷氧化偶联反应为研究对象，针对该反应同时设计同相反应和异相反应及自由基反应的特性，通过构建具有典型催化剂表面结构的团簇模型，采用GPU加速密度泛函计算方法，紧密结合对相关催化剂表面结构和作用机理的实验研究工作，深入研究催化剂表面活性氧物种对甲烷的催化活化及中间产物的进一步催化和非催化转化，充分利用团簇模型量子化学计算的特点，并结合对关键反应步骤的周期性表面模型计算和对比研究，建立完整、可靠的甲烷氧化偶联反应催化循环机制，在此基础上研究掺杂元素对催化剂表面结构及催化性能包括催化活性和产物选择性的影响，对催化剂进行理性设计。项目对于氧化物表面甲烷的活化及转化机制、氧化物表面的结构及催化反应机制及复杂催化反应循环机理及催化剂的理性设计均具有普遍的指导意义，具有重要的学术价值和良好的应用前景。

甲烷氧化偶联反应是甲烷直接高效利用的主要途径之一，可以将甲烷一步转化为具有高附加值的乙烯等产品，因此具有重要的工业应用价值。然而，由于该反应中甲烷转化率和乙烯选择性之间存在竞争关系，导致乙烯的收率有限，从而影响该过程的工业化。本项目采用氧化镧团簇和表面模型，通过GPU加速的密度泛函理论计算，揭示甲烷在氧化镧团簇和表面上的活化机制，深入考察反应中间物种可能的转化途径，构建较为全面的微观反应动力学模型。基于团簇和表面模型计算，我们揭示了氧化镧催化甲烷氧化偶联反应的循环机制：甲烷首先在催化剂表面镧氧键位点断裂，所生成的甲基与气相中氧气分子反应生成甲基自由基，而表面上所生成的超氧位点可以活化另一分子甲烷从而生成第二个甲基自由基，最后所生成的过氧位点可以与甲烷反应生成甲醇，使得氧化镧催化剂得以复原。而甲醇亦可进一步被过氧位点所氧化最终生成二氧化碳，从而导致乙烯选择性降低。项目的研究成果对于理解氧化物表面甲烷的活化及转化机制、构效关系、催化反应的循环机制及催化剂的理性设计具有一定的指导意义，具有重要的学术价值。