A green route for the synthesis of nano-sized hierarchical ZSM-5 zeolite with excellent DTO catalytic performance

Abstract

Nano-sized hierarchical ZSM-5 zeolite with high crystallization was prepared by a novel green strategy, that is, the consecutive freezing and vacuum drying route. In comparison with the traditional synthesis process, only 1/5 amount of TPAOH (tetrapropylammonium hydroxide) template was involved. Moreover, hierarchical structured zeolites can be formed even in the absence of mesoporous template (e. g. cetyltrimethylammonium bromide, CTAB). Moreover, the hierarchical ZSM-5 with a wide range of SiO2/Al2O3 ratio (25–200) can be modulated. The effects of the consecutive freezing and vacuum drying methods on the formation process, pore characteristics, crystallinity, morphology and acidity of the ZSM-5 zeolites were explored. It is noted that the abundant intra-crystal mesopores and nanoparticles structure were generated from the porous structure on the surface of the freeze-dried powder. The constructed nano-sized and hierarchical ZSM-5 catalyst exhibits a prolonged lifetime of 110 h in dimethyl ether-to-olefin (DTO) reaction, which is around 3.7-fold lifetime compared to the conventional microporous ZSM-5.