多相催化过程中甲烷C-H键活化机理的理论研究

Selective activate of methane to produce ethylene, methanol, ethanol, and benzene is a catalysis challenging, and how to prevent the carbon deposition of catalyst and overoxidation catalyst to generate CO2 are the two key issues which need to be addressed. In this project, the first principle density functional method and slab model with periodic boundary conditions were performed to study the effect of surface structures as well as the different additive atoms (alkali metal atoms, halogen atoms, transition metal atoms and so on) for several typical catalysts such as Ni, Pd, Pt, Rh on the selective oxidation of methane, to reveal the mechanism of additive atoms and the reasons for how to suppress carbon deposition on the catalyst surface; and to explore the Mo / ZSM-5 catalyzed methane reaction to form ethylene and benzene under anaerobic conditions, to clarify the essential difference with that of partial oxidation. These theoretical calculations may help people to understand the physical nature of selective activation of methane further, and may give a theoretical guide in the design of the efficient catalyst for the active of methane.

甲烷选择性活化生成乙烯、甲醇、乙醇以及苯是催化领域一个具有挑战的研究课题。如何防止催化剂表面积碳以及过度氧化生成CO2是其中需要解决的两个关键问题。本申请项目拟采用基于第一性原理的密度泛函方法和周期性边界条件的平板模型，研究几种典型甲烷催化剂如Ni、Pd、Pt、Rh等的不同晶面以及不同助剂原子（碱金属原子，卤素原子，过渡金属原子等）的改性对甲烷选择性氧化的影响，揭示助剂原子的作用机制以及如何抑制催化剂表面积碳的原因；同时探讨无氧条件下Mo/ZSM-5催化甲烷生成乙烯及苯的反应过程，阐明其与有氧活化的本质区别。通过这些理论计算研究有望对甲烷选择性活化的本质有更加深入的了解，并为高效甲烷活化催化剂的分子设计提供理论指导。

经由甲烷制合成气或直接生成乙烯、甲醇或苯是催化领域一个具有挑战的研究课题，如何 防止催化剂表面积碳以及过度氧化生成CO2是其中需要解决的两个关键问题。我们采用第一性原理的密度泛函方法以及具有周期性边界条件的平板模型，研究了过渡金属催化的甲烷活化反应机理，发现增强金属-载体之间的相互作用强弱，减小催化剂的颗粒大小（特别是单原子催化剂），碱金属助剂如K的添加等均有利于提高催化剂的抗积碳能力，从而提高形成合成气的选择性。同时我们还探讨了无氧条件下Mo/ZSM-5催化甲烷生成乙烯及苯的反应过程，阐明了其反应机理，积碳机理，获得了催化活性位的相关信息。通过这些理论计算研究有望对甲烷选择性活化的本质有更加深入的了解，并为高效甲烷活化催化剂的分子设计提供理论指导。