基于甲醇转化烃池机理微微双孔道分子筛制备及其促进丙烯生成机制研究

Coal-based Methanol to Propylene (MTP) is an effective way to tackle the problem of natural gas and petroleum crisis and the rapid growth of propylene demand in China. The key problem of existing MTP process is to improve the ratio of propylene to ethylene and propylene yield without circulation system through the development of high performance catalysts. With the method of Chemical-Vapor-Deposition and electrostatic matching, this project will prepare a nuclei (12-Ring channel)-shell (10-Ring channel) composite molecular sieve with the orientation of nuclear pore. In the methanol conversion reaction, 12-Ring channels in nuclear phase promote the formation of the polymethyl benzene as active hydrocarbon-pool species, which would improve the ratio of propylene to ethylene; 10-Ring channels in shell phase enhance the diffusion limitation and methylation cracking process of heavy hydrocarbon, which would improve the propylene yield. Based on the crystal surface control method of molecular sieve membrane, silicon microwires act as “hard template” deposited on the surface of nuclear phase molecular sieve, on which the shell phase molecular sieve follows oriented crystallization. Through multiple pulse reaction and the residue species analysis, we can deduce the transformation way of methanol and heavy olefins on this special topological micro-micro double-channels molecular sieve, and we will explore the correlation of the active species and the composite channels. Finally, core-shell synergy model would be optimized. The intensive exploration in this project will be significant in the development of product-selectivity regulation ideas and MTP catalyst with high performance.

煤基甲醇制丙烯（MTP）是增产丙烯的有效途径之一，通过高效催化剂的研究开发提高单程丙烯乙烯比和丙烯收率仍然是MTP技术的核心问题。基于甲醇转化烃池机理丙烯生成途径以及分子筛孔道择形特征，制备12-10元环微微双孔道分子筛以及具有孔道择形取向的核（12元环孔道）-壳（10元环孔道）复合分子筛材料用于甲醇转化反应——十二元环孔道促进多甲基取代苯活性烃池物种的生成以提高丙烯乙烯比，十元环孔道增强大分子烃类的扩散限制及其甲基化裂化反应历程来改善丙烯收率。借鉴分子筛膜的晶面调控技术，采用化学气相沉积法和静电匹配法，使壳相分子筛在经表面沉积“硬模板”（硅微米线）的核相分子筛上取向生长；并通过脉冲进料反应和存留物种分析，探讨活性烃池物种性质与复合孔道特征的构效关联，优化核-壳协同作用模式。本申请的完成将为甲醇转化反应开辟崭新的催化剂类型，有助于完善产物选择性调控思路，对开发新型MTP催化剂意义重大。

煤基甲醇制丙烯（MTP）是增产丙烯的有效途径之一。基于“烃池机理”研究分子筛结构特征与甲醇反应机理、烯烃产物生成机制的关联，基于“结构导向作用”有目的性地进行分子筛合成，对于指导开发特殊拓扑结构的催化剂具有重要意义。本项目中，研究了分子筛孔道尺寸的变化，对甲醇转化反应中烃池物种、反应路径和产物分布的影响，发现12元环孔道内高甲基苯为主的芳烃循环和10元环孔道内烯烃循环的双循环反应路径是获得高丙烯乙烯比的根本原因；以不同长度亚甲基链连接得到链状咪唑基双阳离子（nBDMI）为结构导向剂，研究阳离子几何尺寸-分子筛骨架之间的作用形式，发现大尺寸的咪唑阳离子有利于大孔道分子筛的生成，直链状结构有利于十元环孔道的导向生成；并分别采用双阳离子的咪唑衍生物和有机胺为导向剂，在低的水硅比、适中的高晶化温度下强化介稳相12-10双孔道分子筛的合成，经后处理改性后，可实现丙烯/乙烯比超过27。