High gravity hydrothermal synthesis of hierarchical ZSM-5 for Friedel–Crafts alkylation of toluene with benzyl chloride

Hierarchical ZSM-5 zeolite was prepared via high gravity hydrothermal by a salt-aided seed-induced route. XRD, SEM, TEM, the laser particle size analyzer, N₂ adsorption–desorption and NH₃-TPD were used to characterize the physicochemical properties of the hierarchical ZSM-5 materials. The prepared hierarchical ZSM-5 was compared with sample synthesized by traditional hydrothermal method, and their catalytic performances in the alkylation of toluene with benzyl chloride were investigated. The experimental results indicated that the optimum conditions was the high gravity factor of 94.06, colloidal silica flow rate of 30 ml min⁻¹ and aluminate source mixture flow rate of 20 L h⁻¹. Under this condition, the hierarchical ZSM-5 was rough quasi-spherical particles with narrow particle size distribution and large S_BET of 432.4 m² g⁻¹. The catalyst had superior catalytic activity and was highly reusable preserving its catalytic activity after three reuses. This work showed that sufficient micro-mixing, which affected their catalytic properties, was beneficial for the crystal seed dissolution, recrystallization and mesoporous formation.