Synthesis of hierarchical ZSM-5 by cetyltrimethylammonium bromide assisted self-assembly of zeolite seeds and its catalytic performances

Abstract

Hierarchical ZSM-5 zeolites with controllable structure were hydrothermally synthesized through self-assembly of zeolite seeds by the assistance of cetyltrimethylammonium bromide (CTAB) without other organic co-solvent or additive, and characterized by XRD, FT-IR, SEM, TEM and N2 adsorption. The results show that the synthesized samples are of pure MFI structure with high crystallization, and the crystal sizes of hierarchical ZSM-5 are primary nanoparticles. The addition of CTAB can decrease the primary nanoparticle sizes to 10 nm and hinder further aggregation of nanoparticles into zeolite crystal. The BET surface area, total pore volume and external surface area of hierarchical ZSM-5 samples can be tuned by the amount of CTAB. It is thought that the addition of NaOH and CTAB plays an important role in crystallization and self-assembly of zeolite seeds. Compared with ZSM-5 prepared without CTAB, the hierarchical ZSM-5 shows better stability and 2,6-dimethylnaphthalene yield in the methylation of 2-methylnaphthalene with methanol.