The effect of alkaline treatment on the properties of hierarchical ZSM-5 prepared by post-synthesis desilication

The effect of alkaline treatment on properties of hierarchical ZSM-5 was investigated in this work. The ZSM-5 zeolite was treated by aqueous solution of NaOHwith variation concentration of 0.25, 0.5, 1.0 and 2.0 M. The properties of hierarchical ZSM-5 were characterized by XRD, FTIR, SEM, and isothermal N₂-sorption. The XRD analysis shows that all samples consist of ZSM-5 and tridymite phase. The NaOH treatment doesn’t have a significant effect on the structural phase but greatly influence the crystallinity. The higher NaOH concentration, the lower the relative crystallinity. FTIR analysis confirms the presence of ZSM-5 structure without any new bonding formation. SEM examination revealed that NaOH treatment could change the morphology of the particles indicatedby the formation ofthe hole and crack in the ZSM-5 particle’s surface as a result of desilication. The N₂-sorption shows that increasing NaOH concentration can reduce the particle’s surface area. The treatment succeeds to form mesopore in the initial ZSM-5 with a diameter of mesopore lies around 36-38Å. The presence of micropore and mesopore in all samples confirms the formation of hierarchical ZSM-5 after alkaline treatment using NaOH solution.