分子筛微-微孔道的限域协同作用对甲醇制烯烃反应路径和产物选择性的调控

Methanol to olefins (MTO) technology has gained great success. However, single pass selectivity for propene or ethene is still unsatisfied. Understanding the reaction rules and further fabricating effective catalyst are the major directions. The steric confinement of micropores plays an important role in the regulation of the active species, reaction path and product distribution in the MTO reaction. In this proposal, HBeta with three-dimensional 12-MR (12-membered ring) channel，HMOR with 8-MR and 12-MR channel as well as HCON-1 with 10-MR and 12-MR channel are employed to investigated the spatial confinement and synergy effect of the different micropore channels. The acid in specific pore channel are selectivity deactivated by Na+ introduction, SiO2 deposition and pre-coking by which effective methods of acid regulation will be developed. And then, the steric confinement of single 8-MR, 10-MR and 12-MR and synergy effect of micro-micro composite channels on ethene and propene selectivity will be investigated. 13C MAS NMR, steady-state, transient, co-feed, and isotopic labelling techniques will be used to identify the reaction pathway and further illustrate the steric confinement and synergy effect of micropores on reaction pathway and product distribution. Finally, the intrinsic correlation of catalyst pore structure, acidity, reaction path and product distribution will be established. This project can give a clear understanding of steric confinement and synergy effect of micro-micro channels on MTO reaction and provide a new idea for the design of high-propylene selective catalyst.

甲醇制烯烃（MTO）技术已取得巨大进展，然而目前仍存在单一产物选择性低的问题。理解选择性控制原理，构建高效催化剂是目前该领域要解决的核心问题。分子筛的孔道限域效应对MTO反应中活性物种生成、反应路径和产物分布的调控具有重要作用。本项目拟以三维十二元环孔道HBeta、八元环和十二元环孔道结构的HMOR、十元环和十二元环孔道结构的HCON分子筛为研究对象，通过定向引入Na+、选择性沉积SiO2、预积碳等手段定向调控不同孔道中的酸位，开发酸位定向调控的有效手段；探索八元、十元环和十二元环及微-微复合孔道的限域效应对乙烯丙烯选择性的影响规律；采用核磁，稳态、瞬态、同位素切换、共进料实验等手段阐明分子筛的微-微复合孔道限域协同效应对反应路径和产物分布的调控机制，建立催化剂的孔道结构-酸性-反应路径-产物分布的内在关联。本项目可以深化对MTO反应孔道限域效应的理解，为设计高丙烯选择性催化剂提供新思路。

甲醇制烯烃反应中分子筛的酸性和孔道限域效应对MTO反应中活性物种生成、反应路径和产物分布的调控具有重要作用。理解选择性控制原理，构建高效催化剂是目前该领域要解决的核心问题。本研究中有机模板剂限域的转晶策略，实现了具有不同硅铝比的纳米ZSM-5分子筛的快速合成；发展了无有机模板剂无氟离子导向方法制备了低硅SAPO-34分子筛并实现硅含量的可控调节；开发了蒸汽辅助晶化法构建了Beta@Silicalite-1复合孔道分子筛，通过水热合成方法制备了具备不同硅铝比的ZSM-48分子筛。通过表征手段，对分子筛的晶化机理进行了深入研究，同时精准控制晶化条件，有效实现了分子筛组成、孔道结构和酸性的调变。研究八元环、十元环和十二元环孔道空间限域作用对乙烯丙烯选择性的影响规律，并探究了分子筛微孔道和酸性对反应路径和产物分布的调控机制。