Research Progress on Hierarchically Porous Zeolites: Structural Control, Synthesis and Catalytic Applications

Zeolite has an excellent ion-exchange property, rich acid sites and good structure and catalysis stability. Therefore, it has been widely used in many fields, i.e., industrial catalysis, separation and adsorption, etc. However, the application of zeolite is greatly limited in many catalytic reactions involved in the large molecules due to its smaller micropore size (<1.5 nm). The introduction of hierarchically porous structure into conventional zeolite crystals not only keeps their crystalline framework, acidic active sites and high thermal and hydrothermal stability, but also accelerates the diffusion/transfer of larger molecules and greatly decreases the formation of carbon residue, thus prolonging the catalyst life, which enables them more popular applications in the catalytic field. Herein, the recent research progresses of the control of pore structural, the synthesis strategy and mechanism of some typical kinds of hierarchically porous zeolites, including disordered mesoporous/macroporous structure, ordered mesoporous/macroporous structure, dual mesopore structure with certain orientation, hollow structure and macroporous-mesoporous-microporous structure, etc, are concluded. In addition, the application progresses of these hierarchically porous zeolites in catalytic fields are summarized. Compared with the conventional zeolites and amorphous mesopore materials, the novel hierarchically porous zeolites show more excellent catalytic performance due to the crystalline framework and the introduce of hierarchically pore structure. Finally, an outlook for the hierarchically porous zeolite promising development in the future is put forward.