Sn/HZSM-5分子筛中Sn-Lewis酸性的调控及其乙烷氨氧化作用机制的研究

乙烷氨氧化反应催化剂能将来源广泛的乙烷，经由氧化脱氢、氨化脱氢等反应路径，转化为我国国民经济中必需的大宗化工品-乙腈，有一定应用潜力。HZSM-5分子筛载体对Sn-Lewis酸（L酸）位的结构调变、酸性调控作用，使得Sn/HZSM-5分子筛催化剂在乙烷氨氧化反应中表现出良好的催化性能。但是，由于存在Sn-L酸活性位结构不明确、各种Sn-L酸位催化反应的作用机制不清晰、乙烷氨氧化反应机理认识不足等瓶颈问题，制约了Sn/HZSM-5分子筛催化乙烷转化性能的进一步提升。本项目拟通过改变Sn-L酸的引入方式或定向改变分子筛的骨架铝分布，调变Sn物种的精细结构性质，从而调控Sn-L酸的酸性；结合催化剂表征和评价、同位素实验、动力学研究等技术手段，定性Sn-L酸活性位、理解其产生乙烷氨氧化反应催化作用的本质规律，为定向可控地合成高乙烷转化活性、高乙腈选择性的Sn/HZSM-5分子筛催化剂提供理论依据。

Catalysts for ethane ammoxidation reaction can convert abundant ethane into acetonitrile, which is an indispensable bulk chemical in our national economy, through oxidative dehydrogenation and ammonia oxydehydrogenation. HZSM-5 molecular sieve supports can adjust the structure and acidity of Sn-Lewis acid (L acid) site, which guarantees Sn/HZSM-5 molecular sieve catalyst with good catalytic performance in ethane ammoxidation. However, the further improvement of catalytic performance of Sn/HZSM-5 molecular sieves in ethane conversion reaction is restricted due to the unclear structure of Sn-L acid active sites, unclear catalytic role of various Sn-L acid sites in reactions, and insufficient understanding of ethane ammoxidation reaction mechanism. This project intends to adjust the Sn-L acidity by changing the introduction mode of Sn-L acid sites or regulating the framework-aluminum distribution in zeolite channels directionally, so as to adjust the fine structure properties of Sn species; combined with the technical means of catalyst characterization and evaluation, isotopic experiment, kinetics research, etc., this project intends to characterize the catalytic active sites among various Sn-L acids and understand the essential law of their catalytic role in ethane ammoxidation reaction. The theoretical basis is then established for the directionally controllable synthesis of Sn/HZSM-5 molecular sieve catalyst with high ethane conversion activity and high acetonitrile selectivity.