Sufficient Metal–Acid Site Matching in Co-Loaded WO x -ZrO2 Catalysts for Polyethylene Hydrocracking

Abstract

Chemical upcycling via catalytic hydrocracking to produce liquid fuels represents a promising strategy for addressing the pressing environmental challenges associated with plastic waste. In this study, we reported a non-noble-metal cobalt catalyst supported on tungstate-zirconia (Co/WOx-ZrO2) for the efficient hydrocracking of low-density polyethylene (LDPE). The matching between acid sites and active metal centers, particularly the Brønsted/Lewis (B/L) acid ratio, was systematically tuned by varying the Co loading. Notably, the optimized Co10/WOx-ZrO2 catalyst achieved a complete conversion of LDPE with a high liquid hydrocarbon yield of 76.6%, including 67% naphtha (C5–C12) and 59% jet-fuel-range (C8–C16) products. Its performance was comparable to that of a noble-metal-based catalyst (Pt) and superior to those of other non-noble-metal catalysts (Mo and Cu). Insufficient Co loading provided inadequate dehydrogenation/hydrogenation sites, leading to over cracking and increased formation of solid and gaseous products. In contrast, excessive Co loading afforded a lower B/L ratio, which suppressed cracking and reduced liquid yields in the naphtha and jet-fuel ranges. This work provides a guidance for the rational design of non-noble-metal catalyst for efficient LDPE hydrocracking.