Synthesis of Hierarchical Porous Materials via Sol-gel Method for Green Catalysis Process

Guoxing Xiong
State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences

Yuxin *Jia
State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics,Graduate School of the Chinese Academy of Sciences

Wei *Han

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     Last modified: January 18, 2006

Abstract
Zeolites have been used as catalysts contributing to the “greening” of process technology in two ways: first, by replacing many hazardous acidic catalysts such as HF, HCl and H2SO4; second, by eliminating some intermediate steps in certain processes to reduce overall waste output and energy use1. However, their small pore size brings diffusion and mass transfer limitations on some industrial processes, especially those reactions involving large molecules. The rational approach to overcome such a limitation would be to prepare hierarchical porous materials containing zeolite structures by using soft2 or rigid3 templates.
Based on our previous study4,5, we develop two novel methods to prepare hierarchical porous materials containing ZSM-5 or TS-1 zeolite structures as catalysts for cracking of crude oil, hydroisomerization of long-chain hydrocarbon or hydroxylation of phenol. The first method involves solvthermal recrystallization of xerogel converted from uniform ZSM-5 precursor sol by using vacuum drying method. We have prepared series hierarchical porous materials containing ZSM-5 micropore structures and uniform intercrystalline pore sizes which varied with different temperature, time or solvents of recrystallization. Another way is zeolitization of diatomite which has natural macroporous structures achieved by in situ seeding. The diatomite has been zeolitized by introducing zeolite nano-precursor sol on the surface of diatomite followed by steam-assisted crystallization.
The zeolite sol and the hierarchical materials were characterized by laser light scattering, XRD, FTIR, N2 adsorption/desorption isotherm，SEM and TEM. Work has been undertaken to evaluate catalysis performance of these hierarchical porous materials above-mentioned.





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