Defect-Engineered Pd/ZSM-5 for Hydroconversion of LDPE to Light Alkanes

Abstract

Bifunctional metal–zeolite catalysts are promising for polyolefin hydroconversion, yet random C–C scission and complex depolymerization pathways complicate catalyst design. Desilication provides an interfacial engineering approach to facilitate the coupling between hydrogen activation and macromolecular C–C bond cleavage. Pd/ZSM-5-DSI selectively converted LDPE into a narrow C3–C6 alkane fraction (∼90% selectivity) with negligible methane formation, while maintaining near-quantitative LDPE conversion at 240 °C and 1 MPa H2 for 4 h. The results suggest a plausible metal–acid bifunctional pathway in which Pd sites likely activate H2 and mediate dehydrogenation/hydrogenation of hydrocarbon chains, while accessible acid sites promote skeletal rearrangement and β-scission. Desilication improves the spatial proximity and accessibility of these metal and acid sites, thereby accelerating chain fragmentation. These findings highlight defect-regulated nanoconfinement combined with low Pd loading as an effective strategy for strengthening metal–acid cooperation in bifunctional zeolite catalysts.