Diols-Assisted Synthesis of ZSM-22 with Enhanced Catalytic Activity in n-Hexane Cracking

The investigation of the synthesis of pure-phase ZSM-22 zeolites and their catalytic performance in the n-hexane cracking reaction is of critical significance for industrial production. To enhance the crystallinity of ZSM-22, ethylene glycol was integrated into the synthesis gel, effectively suppressing the formation of quartz and ZSM-5 impurities. Due to the structure-directing effect of ethylene glycol, the ZSM-22 prepared demonstrates much more mesopores compared to the counterparts without ethylene glycol addition. Furthermore, the acid strength and density of the zeolite increased significantly. These pure-phase ZSM-22 samples exhibited enhanced performance in terms of both conversion efficiency and ethylene selectivity during n-hexane cracking, which is associated with the increased abundance of acid sites and a higher ratio of strong to weak acids. These findings highlight the beneficial effects of ethylene glycol modification on the regulation of crystal growth and the enhancement of catalytic performance in ZSM-22 catalysts.