中孔硅铝分子筛的组装及原位沸石化研究

Zeolitization of mesoporous aluminosilicate molecular sieves is investigated by supporting action of mesoporous carbon materials growing into the mesopores of molecular sieves to obtain ordered mesoporous zeolites with uniform mesoporus structures, and a universal in situ crystallization mechanism is acquired too. By improving the structural and surface properties of mesoporous templates, to increase the wall thickness and adjust mesoporous diameter of the molecular sieves. By introducing partly silanized silica, to increase the mesoporosity of the wall of the molecular sieves by producing 1-2 nm submesoporous structures. Then porous carbon materials are in situ assembled in the mesopores to form porous thin wall carbon nanotubes, and/or porous thin film, and/or porous carbon foam. The key technology is to creat micrio-and mesoporous structures in the carbon wall/film in order to decrease mass-transfer resistance of liquid molecules. The hierachical porous sturcture in the wall of mesoporous molecular sieves and mesoporous structure in the thin wall/film of carbon nanotubes, or/as well as carbon foam both provide advantages for increasing mass-transfer rate and accessibility of reaction molecules during in-situ crystallization to come into the ordered mesoporous zeolite molecular sieves. The sturctural and textural properties, diffusion and site accessibility, and catalysis by benzene alkylation with benzyl alcohol or ethylene and polyethylene pyrolysis. The new ordered mesoprous molecular sieves will be effectively used in catalytic conversion of heavier feedstocks and biomacromolecules to give the aid of clean energy development.

该课题的研究目的在于借助多孔碳材料的支撑作用将中孔硅铝分子筛在水热体系中实现沸石化，制备具有规整和单一中孔孔道结构的沸石分子筛材料，并研究其晶化的普遍机理。拟优化中孔硅铝分子筛的有机模板分子以提高孔壁厚度3-5nm，适当减少中孔直径；引入硅烷化剂提高中孔分子筛孔壁的孔隙率，创造1-2nm的二次中孔。原位引入多孔碳材料于分子筛的中孔之中，以薄壁碳纳米管、碳膜和泡沫碳等多孔道碳材料为研究主体，解决碳材料孔壁的多孔性问题。从中孔分子筛孔壁和碳材料孔壁两方面为中孔分子筛的原位沸石化减少液体的传质阻力并提高反应液体的可接近性，从而生成高度有序的中孔沸石分子筛材料。以原位表征技术研究特定条件下的沸石晶化机理，以苯的烷基化、聚乙烯热解等模型反应，研究中孔沸石分子筛材料的吸附、扩散和反应性能。新的中孔沸石分子筛的合成将对解决重油大分子反应和生物大分子反应提供新的思路，为清洁能源的发展提供可靠保障。

本课题本着制备具有二次发达孔隙结构且孔径分布窄的中孔沸石为目标，探索了在水热合成沸石体系中有机硅烷作为部分硅源或以表面硅烷化的MCM-41（纳米二氧化硅）作为硅源，利用其有机硅烷中有机基团这种“软炭”的造孔作用制备中孔沸石的方法，并成功地制备了具有多种骨架结构的低硅（LTA，FAU），中硅（丝光沸石）和高硅（EU-1，ZSM-5）中孔沸石和中孔SAPO-34分子筛，并获得了合成规律和晶化机理。与此同时，在对各种中孔沸石进行基础表征的基础上，重点对其中孔结构（位置、形状和相互连通性）和酸性（酸性点的分布和可接近性）进行了考察，并对沸石内二次中孔的引入对碳氢化合物的可接近性和扩散能力的促进作用，以及表面酸性的改变对吸附和扩散的影响进行了深入研究，并结合其在芳香烃的苄基化大分子反应中的催化行为，揭示了多级孔沸石催化剂在大分子反应中应用的可能性及其优越性。其研究成果为多级孔沸石的制备和应用奠定了基础。