具有三维有序结构的多级孔分子筛的设计合成与构效关系研究

Hierarchical zeolites are attracting considerable attentions from both academic and industrial points of view due to their promising integrated superiorities of acidic property and shape selectivity from the microporous structure of zeolites and facilitated access and improved transport benefitted from the complementary hierarchical network. However, it is subjected to the complexity of microstructure and the uncertainty of formation mechanism, which seriously hinder the application of hierarchical zeolites. Here, we propose a systematic study on oriented synthesis and structure-property relationship investigation of hierarchical zeolites with three-dimensionally ordered mesoporous-imprinted (3DOm-i) structure. An atomistic model will be built to particularly analyse the microstructure, and further employed to investigate the structure effects, especially the hierarchical network, on the performance in reactions involving bulky molecules. Confined growth method along with multiple hydrothermal treatments and seeded growth, which provides a versatile means for introducing ordered mesoporosity to zeolites with controllable topology and morphology, will be used for the synthesis, and based on the simulation results, systematical control of crystalline, hierarchical network and acidic property will be proceeded. Furthermore, the catalytic performances (rates, apparent activation energies and effectiveness factors) of 3DOm-i hierarchical zeolites will be comparable to conventional porous materials with single pore system by probe reactions involving bulky molecules, such as catalytic conversion of C4 hydrocarbons and olefin epoxidations. It can be expected that the research we propose here will not only promote the practical process of hierarchical zeolites, but also demonstrate a proven strategy in the exploitation of novel catalysts for bulky molecular reactions involved in heavy oil upgrading, coal utilization,and also biomass conversion.

具有三维有序结构的多级孔分子筛是一类适用于大分子反应的新型催化剂材料。然而，由于其结构的复杂性及形成机理的不确定性，阻碍了对其微结构解析、合成设计以及构效关系的研究，严重影响了其实用化进程。本项目拟通过建立准确的原子级模型，强化对其微观结构与大分子吸附、催化性能之间关系的理论解析，指导设计制备与结构调控；基于限制域生长法，引入多次水热生长循环与晶种二次生长，合成具有三维高度有序结构的多级孔分子筛，并根据模拟数据定向调控其晶相结构、孔结构以及酸结构；以C4烃类催化转化、大分子烯烃环氧化为特征反应，评价多级孔分子筛参与大分子反应的催化效率、剖析多级孔道的结构优势以及综合利用外表面活性位。本项目的实施不仅可以提供出一套从"功能-结构-合成"之间的关系入手，设计合成适用于大分子催化反应的新型多级孔分子筛的新方法和基础理论，还为多级孔分子筛微结构解析与定量构效关系建立提供新思路和理论依据。

多级孔分子筛兼具沸石分子筛晶态骨架和有序中孔分子筛大孔径传质优势，是参与VOCs气体捕集、重质油加工、煤炭转化以及生物质利用等大分子吸附、催化反应过程中的理想吸附剂和催化剂材料，本项目按照申报书中的研究计划从理论建模、合成设计和构-效关系三方面入手，对多级孔分子筛进行了系统、深入的理论与实验研究。.设计并构建多级孔分子筛（MFI纳米片层）的全原子结构模型并对其微观结构进行了原子层面上的解析；成功制备出三种结构新颖的多级孔材料（具有层状Silicalite-1外壳的中空沸石微球、三维有序多级孔的SAPO-34分子筛和具有三维有序堆积结构的二氧化硅纳米小球）；对三维有序多级孔分子筛进行了晶相调控与孔结构调控，以及骨架间相互复合；通过杂原子同晶置换，合成出两种具有多级孔结构的钛硅分子筛（三维有序结构的钛硅分子筛和具有层状自柱撑结构的钛硅分子筛）；将分子模拟与实验相结合，建立起多级孔分子筛参与大分子吸附/催化过程的定量构效关系，系统评价了MFI纳米片层及具有三维有序多级孔结构的BEA分子筛对有机大分子（苯和甲苯）的吸附性能，开发出了高寿命、高选择性的甲醇制烯烃催化剂（具有三维有序多级孔结构的SAPO-34分子筛）。