Hierarchical FAU Zeolites Boosting the Hydrocracking of Polyolefin Waste into Liquid Fuels

Abstract

Conventional metal-zeolite catalysts struggle with hydrocracking polyolefin wastes due to a significant mismatch between the size of large polymer molecules and the micropores of zeolites. This severely constrains diffusion and site accessibility, resulting in low efficiency. Here, we unveil a simple hydrothermal treatment of commercial Y zeolite that creates hierarchical Y zeolite (Y−H), which possesses substantial layers of mesoporous nanoflakes on its surface, constructing a unique pore architecture. This pore network integrates large (ca. 13 nm) and medium (ca. 4 nm) mesopores with the original micropores (<1 nm) critically without altering the zeolite's topology, crystallinity, or acidity. Compared with commercial Y and Pt/Al 2 O 3 , Y−H and Pt/Al 2 O 3 exhibit a remarkable 4-fold increase in activity, which is attributed to enhanced accessibility of acid sites, providing sufficient cascade cracking space for macromolecular polyolefins to be efficiently converted into small, branched alkanes. Notably, the catalyst achieves an impressive 96.8% PE conversion with 90.8% selectivity toward value-added gasoline and diesel fuels (C 5−20 ) within 4 h at 280 °C. This work not only demonstrates the pivotal role of hierarchical pore networks in polyolefin hydrocracking but also highlights their broader applicability in plastic waste upcycling.