Facile synthesis of hierarchical porous ZSM-5 zeolite with tunable mesostructure and its application in catalytic cracking of LDPE

Abstract

ZSM-5 zeolites with hierarchical porosity have been an increasing attention due to their improvement in diffusion limitation issue. This work here reports that hierarchical porous ZSM-5 zeolites were synthesized using fumed silica and as-synthesized mesoporous silica nanoparticles (MSNs) as dual-silica source for the first time with the aid of silicate-1 seed. The effects of the amounts of silicate-1 seed and as-synthesized MSNs on crystallinity, morphology, mesoporous structure and acidity of the prepared ZSM-5 zeolites were systematically investigated by XRD, FT-IR, SEM, TEM, N2 adsorption-desorption and NH3-TPD techniques. The results showed that mesopores can be incorporated by introducing an appropriate amount of as-synthesized MSNs which also promote the crystallization of aluminosilicate at the same time. Moreover, the mesoporous structures of ZSM-5 zeolites can be flexibly regulated within a certain range via varying the dosage of as-synthesized MSNs. The obtained optimal sample Z-0.02–0.2 with high crystallinity and bi-modal mesopores centered at 2.1 nm and 3.4 nm exhibits significantly improved catalytic performance in LDPE cracking on a TG apparatus, compared with the conventional mono-modal microporous ZSM-5 zeolite. This approach constitutes a simple and low-cost pathway to synthesize ZSM-5 zeolites with controllable hierarchical porous architecture and might facilitate their industrial application.