绿色路线合成多级孔沸石分子筛催化材料

Zeolites with their micropores providing a defined environment of active sites as well as shape selectivity at each single pore entrance, belong to the most important catalytic materials used today. However, their utilization in catalysis is limited due to the slow transport of the reacting species within their micropores. To circumvent these transport limitations, it is highly desirable to synthesize zeolites with hierarchically porous structures, where the diffusion path lengths can be greatly reduced by the introduced mesopores and/or macropores. Numerous strategies have been developed to reach this goal such as post-treatment and templating synthesis (hard templates, soft templates and bifunctional-templates). Despite the demonstrated positive effect of such additional mesopores and/or macropores on the catalytic performance, these strategies have yet been widely adopted by industrial production, because they are neither at expense of crystallinity nor high cost and tedious procedures. To overcome the limitations of existing strategies, in this proposal, two promising routes for targeting hierarchically porous zeolite are proposed: i) solvent-free synthesis without the assistance of large molecule templates; ii) organotemplate-free synthesis. Our efforts in this proposal will be concentrated on how to tailor the pore size and pore shape of zeolites followed by investigating of the role of solvents and templates and thereby revealing the mechanism of crystallizaion to understand the formation of hierarchically porous structures. To delineate the inimitable role of hierarchically porous structures on catalytic performance and to build the structure-property correlations, catalytic evaluation of MTO and catalytic crack of cumene will be carried out.

沸石分子筛的微孔孔道在催化反应中提供优异的催化活性，但其较小的孔道尺寸不利于扩散，影响催化性能。因此合成能显著提高传质的多级孔沸石分子筛显得尤为重要。传统合成多级孔沸石分子筛的方法包括后处理法、硬模板法、软模板法和双功能模板法等，但这些方法不是会破坏沸石分子筛骨架结构就是模板剂合成复杂且成本高，不利于工业化应用。针对上述问题，本项目提出无溶剂条件下不添加大分子模板法和无任何有机模板剂法等绿色路线制备系列多级孔沸石分子筛催化材料，调控其孔道结构与尺寸，深入探究晶化过程中溶剂和模板剂的作用机制，揭示多级孔沸石分子筛的孔道构筑机制，进一步研究其在甲醇制备低碳烯烃以及异丙苯裂化等反应中的活性，揭示多级孔道结构在上述反应中的核心作用，实现多级孔沸石分子筛催化性能的可控调变。

沸石分子筛的微孔孔道在催化反应中提供优异的催化活性，但其较小的孔道尺寸不利于扩散，影响催化性能。因此合成能显著提高传质的多级孔沸石分子筛显得尤为重要。传统合成多级孔沸石分子筛的方法包括后处理法、硬模板法、软模板法和双功能模板法等，但这些方法不是会破坏沸石分子筛骨架结构就是模板剂合成复杂且成本高，不利于工业化应用。针对上述问题，本项目提出无溶剂条件下不添加大分子模板法和无任何有机模板剂法等绿色路线制备多级孔沸石分子筛催化材料。通过调节初始原料配比，在接近室温的条件下，不添加任何有机模板剂成功得到介孔EMT分子筛，深入研究其晶化过程，阐述了孔道的形成机制和尺寸变化规律，揭示多级孔沸石分子筛的孔道构筑机制，催化结果表明，介孔的存在提高了传质效率从而提高了反应活性，揭示多级孔道结构在反应中的核心作用。同时，使用无溶剂法合成的核壳结构ZSM-5@Silicalite-1催化剂由于表面酸性位点被覆盖，因此在甲苯与甲醇烷基化反应中具有比ZSM-5分子筛更高的对二甲苯选择性以及更长的寿命，表明通过调节催化剂表面性质可以调控催化性能。考虑到工业上需要将粉末催化材料成型后再进行催化反应，所以该项目中进一步将该绿色合成路线应用于一锅法制备全结晶成型分子筛催化剂，无机粘合剂成功转化目标分子筛，获得系列无粘合剂的高结晶度成型催化剂，该催化剂在甲醇至烯烃反应中表现出良好的丙烯选择性，且显著延长了催化剂寿命，为绿色路线一锅法制备成型催化剂提供了理论指导和技术支撑。

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