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分子筛是一种三维微孔结构的硅铝酸盐晶体,具有灵活多变的骨架和组成、较高的物理和水热稳定性、无毒、高比表面积、离子可交换性以及很低的成本等特点,因而在油品精制、石油化学、农业、水和污水处理等众多领域中用作离子交换剂、催化剂和吸附剂.尽管分子筛的应用是基于其本身的微孔结构,但微孔也导致体积较大的反应物和产物分子的传质阻力高.通过制备纳米尺度和多级孔结构的分子筛等多种手段可克服常规分子筛所具有的传质限制.人们已经开发了多种方法制备了新型的分子筛材料,并考察了它们在各种催化反应和吸附反应中的性能.在反应体系中采用这种多级孔的纳米分子筛,有可能提高催化剂的使用寿命和催化性能,抑制积碳和失活.本综述概述了多级孔分子筛和纳米分子筛的高性能及其合成方法的最新进展,讨论了每个合成方法的优缺点,简述了纳米分子筛和二级孔结构分子筛的催化应用,并与常规分子筛进行了比较.
Molecular sieve is a three-dimensional porous aluminosilicate crystal with a flexible framework and composition, high physical and hydrothermal stability, non-toxic, high specific surface area, ion exchangeability and low cost , And are therefore used as ion exchangers, catalysts and adsorbents in many fields such as oil refining, petrochemistry, agriculture, water and wastewater treatment etc. Although the application of molecular sieves is based on their own microporous structure, Resulting in high volumetric reactants and product molecules of high mass transfer resistance through the preparation of nanoscale and multi-stage pore structure of molecular sieve and other means to overcome the conventional molecular sieve with the mass transfer limitations have been developed a variety of methods to prepare The new molecular sieve materials were investigated and their properties in various catalytic reactions and adsorption reactions were investigated.Using this multistage pore nano-molecular sieve in the reaction system, it is possible to improve the service life and catalytic performance of the catalyst, And inactivation.This review summarizes the recent advances in the high performance and synthesis methods of multi-stage molecular sieves and nano-molecular sieves, discusses the advantages and disadvantages of each synthesis method, The catalytic applications of nano-molecular sieves and secondary pore molecular sieves were briefly described and compared with conventional molecular sieves.