基于非经典晶化过程的介观结构功能沸石构筑及应用研究

It is a huge challenge to construct zeolites with special meso/microstructures by simply controlling the thermodynamics of zeolite nucleation and growth. Meanwhile, the fine structure differences of zeolites, such as active site microenvironment, interfacial composition, pore structure and their connectivity, directly affect their catalytic and diffusive properties. Aiming at this challenge which has both important theoretical and practical value, the project will take the non-classical crystallization process involved in the MTW and MFI zeolites as the main research model to achieve effective control of the nucleation and growth of zeolite crystals at the nanoscale, mainly via the design of different structural template agents, the induction of specific seed surface, as well as the conditional control of composition and condition. Through the reasonable control of thermodynamics, lots of specific mesostructured zeolite structures will be constructed, the control methods of zeolite fine structures (such as composition, pore structure, interface properties, etc.) will be explored, and the understanding of new zeolite synthesis theory will be deepened. In view of the catalytic demand of important energy sources and chemicals, we will also focus on the space limitations and the synergistic catalysis of the guest molecules and transition states on the fine meso/microstructures, in order to form the new understanding of catalytic mechanism and develop new catalytic materials.

通过简单调控沸石成核与生长的热动力学来构造特殊介微观结构的沸石是一个巨大的挑战。同时，所得沸石分子筛的精细结构差异，如：活性位微环境、界面组成、孔道结构及其贯通性等，又直接影响其催化和扩散性能。瞄准这一既有挑战，又具有重要理论和实用价值的领域，项目将以MTW及MFI型沸石所涉及到的非经典晶化过程为主要研究模型，通过不同结构模板剂设计、晶种特定晶面诱导、以及条件控制等手段，实现在纳米尺度上有效控制沸石晶体颗粒的成核生长过程。通过合理的热动力学调控，进而构筑多种特异的介微观沸石结构，挖掘沸石精细结构（如：组成、孔道结构、界面性质等）的控制方法，深化对新结构沸石合成理论的认识。并针对重要能源和化学品的催化需求，重点研究介观结构沸石特有的精细结构对客体分子及其过渡态的空间限制和协同催化作用，形成对催化机理的新认识，发展新催化材料。

通过简单调控沸石成核与生长的热动力学来构造特殊介微观结构的沸石是一个巨大的挑战。本项目以MFI、MTW等骨架结构沸石为主要研究对象，从沸石的非经典晶化机理及其过程控制出发，开展了晶种和盐的协同作用对沸石晶体形貌和孔结构的调控、阳离子种类和用量对沸石结晶机制和晶体形貌的调控、硅铝前驱体颗粒自发组装-诱导晶化的动态分离透析、季铵盐模板剂的结构设计及其对沸石形貌的导控规律和机制、沸石剥离减薄造孔及多活性位后处理引入等方面的研究。通过多尺度的结晶过程和后处理控制，成果地调控了级配结构、孔道、组成的构筑机制，进而制备了多种介-微观级配结构、孔道、组成的沸石材料，如：具有丰富晶内介孔的单晶MFI沸石、纳米微晶定向组装的MFI沸石、多重纳米片十字交叉结构的MFI沸石、具有不同介孔结构和晶体致密度的MTW沸石、具有树枝状分形结构的MTW沸石、盘状或者纳米簇状的LTL沸石、碱性物种可调可控的Y型沸石、寡层单分散纳米片状MWW沸石等。并且通过这些沸石形貌、组成和孔结构的优化，发现其在低密度聚乙烯/聚丙烯裂解、二甲苯/三甲苯异构化和歧化、Knoevenagel缩合反应等扩散控制反应中的体现了明显优势。此外，创新性地将构筑的碱性功能沸石拓展应用于纸质文物的安全、高效、功能化保护；同时，为拓展沸石加氢脱硫反应适用性，还对涉氢转化的活性相创制及其负载和反应行为进行初步探索。