Facile synthesis and mechanistic insights into ZSM-5 aggregates via a mesoporogen-free route

Developing hierarchical zeolites is highly important for catalytic applications. In this study, micro- and submicron-sized hierarchical ZSM-5 zeolites, composed of aggregated nanosized ZSM-5 crystals, were facilely synthesized without any mesoporogen. The effects of the gel composition in a mesoporogen-free system on the formation of ZSM-5 aggregates were studied. The results revealed that the Na2O/SiO2 molar ratio and the aluminum source exerted significant impacts. Furthermore, we demonstrated that the morphology and size of the ZSM-5 aggregate could be easily adjusted by varying the gel composition. Mechanistic insights indicated that the formation of hierarchical ZSM-5 aggregates in the mesoporogen-free system likely followed a space-confined growth mechanism.