Enhancing liquified petroleum gas selectivity through hierarchical porosity in MWW-type MCM-49 zeolite for polyethylene hydrocracking

Abstract

Zeolite-based catalysts show their potential in selective hydrocracking of polyethylene (PE) into liquid alkanes under mild conditions. However, achieving selective C–C bond scission toward value-added propane or liquified petroleum gas (LPG) over zeolite-based systems remains underexplored. This work highlights the critical role of hierarchical porosity in enhancing hydrocracking activity for LPG formation via zeolite-supported Pt catalysts. By leveraging Pt's hydrogen activation capability, 0.5 wt% Pt-loaded MCM-49 (MCM-49/Pt) enables full PE conversion with 92.7% LPG selectivity at 300 °C and 3 MPa H₂. Moreover, it maintains >85% LPG yield after five consecutive cycles. This performance discrepancy arises from MCM-49's hierarchical porosity, where mesopores facilitate rapid diffusion of macromolecules to acidic sites, while micropores impose shape-selective constraints favoring gaseous products through spatial confinement, as evidenced by contrasting the catalytic property of MWW-type zeolites MCM-22 (microporous) and MCM-49 (micro-mesoporous). This dual-functional catalyst design enables efficient plastic-to-fuel conversion, offering a sustainable pathway for hydrocarbon resource recovery.