分子筛（MFI）封装单原子铂催化剂构建及用于甲烷选择性氧化性能研究

Increasing metal atom dispersity at the surface of noble metal catalyst and exposing more active sites are an effective strategy to improve catalytic performance of selective oxidation of methane (SOM). In order to overcome the instability drawback of highly dispersed metal atoms in nature, and improve the utilization efficiency of noble metal materials, synthetic technique of zeolite encapsulating noble metal single atom was combined with the SOM reaction in the study and the single atom Pt encapsulated within MFI zeolite catalyst was constructed. The size effect of single atom Pt is cooperated with confinement effect of zeolite to catalyze SOM reaction economically, efficiently and stably. According to hierarchical structure of the prepared catalysts comprised of Pt atom and zeolite, the supported metal content, space structure and enhancing effect on splitting C-H bond will be studied by the aid of modern spectral characterization and catalytic activity test. The confinement effect of pore channel in zeolite on catalytic reaction at the surface of single atom Pt and the enhanced synergistic effects of the composite catalyst will be thoroughly investigated. The dependencies and change regulations between molecule structure-effect and catalytic activity will be also understood. The process parameters will be optimized. The obtained results will provide new ideas and theoretical basis for the research and development of highly active catalysts for selective oxidation of methane.

增大贵金属催化剂上金属原子的分散性、暴露更多活性位点是提高其催化甲烷选择性氧化（SOM）性能的一种有效手段。为了克服高度分散的金属原子不稳定的本质缺陷，提高贵金属材料的利用效率，本研究将分子筛封装贵金属单原子新技术与SOM反应相结合，在MFI分子筛内部构建呈单原子分布的Pt，利用单原子Pt的小尺寸效应与分子筛限域效应协同作用，达到经济、高效、稳定催化甲烷选择性氧化之目的；依据催化剂中Pt原子与分子筛之间的结构层次，采用现代光谱表征和活性测试相结合，重点研究单原子Pt在分子筛孔道内的负载量、空间构造、存在方式以及对碳氢键裂解的强化作用；深入了解孔道限域对单原子Pt表面催化反应的影响，强化复合催化剂之间的协同效应，认识微观分子构效与宏观催化活性的依赖关系和变化规律，优化操作参数，为高效甲烷选择性氧化催化剂的研究和开发提供新的思路和理论依据。

本研究目标在于构筑MFI分子筛内部高度分散Pt金属催化剂，利用单原子Pt的小尺寸效应与分子筛限域效应协同作用，应用于甲烷选择性氧化制合成气的反应中。首先利用水热合成、晶相转变等组合技术制备分子筛封装的Pt原子催化剂，如Pt@S-1和Pt@ZSM-5；采用现代光谱表征技术分析了MFI分子筛内部配位环境、工艺条件对于封装Pt金属分散性的影响，研究了复合催化剂中金属原子的分布规律、存在形式、催化性能等，并初步揭示了催化剂结构与性能之间的关系，实现经济、高效、稳定催化甲烷选择性氧化。研究表明：（1）分子筛封装可提高金属原子分散性和稳定性；（2）限域效应下的Pt原子具有优异的催化甲烷转化性能；（3）高温氧气气氛下金属原子存在分散和团聚的动态平衡。