Abstract: A series of hierarchical micro-meso-pore structure ZSM-5 zeolites were synthesized by NaOH treatment. The structural and acidity properties of as-synthesized zeolites were characterized by XRD, N2 adsorption, SEM, NH3-TPD, and Py-FTIR. The adsorption and diffusion performances of benzene on the treated ZSM-5 zeolites were investigated by an Intelligent Gravimetric Analyzer (IGA). The structure-activity relationship of hierarchical ZSM-5 zeolites was related with the mass transfer, adsorption sites, and acid amount. It is found that the structure of ZSM-5 zeolites is not changed by suitable alkali treatment except crystallinity. After alkali treatment, the meso and micro-porous structures are formed in the hierarchical ZSM-5 zeolites. The acidity of hierarchical ZSM-5 zeolites is improved, which produces more adsorption sites and thus increases the adsorption of benzene on the hierarchical ZSM-5. The adsorption performance of benzene on hierarchical ZSM-5 not only is correlated with the acidity, but also with pore structure of ZSM-5. As a result, the connectivity in the meso-porous ZSM-5 is improved with the increasing of meso-porous in hierarchical ZSM-5, which contributes to the adsorption of active sites and catalytic performance of the treated ZSM-5.

Key words: NaOH, hierarchical pore, ZSM-5, adsorption sites, diffusion rate