Selective hydrocracking of polyolefin waste into branched liquid fuels over a non-noble metal bifunctional Ni–W/ZrO2 catalyst

Abstract

Catalytic upcycling of polyolefin (PO) waste into liquid fuels represents a promising strategy for closing the carbon loop but remains challenged by the reliance on noble-metal catalysts and the generation of low-value gaseous byproducts. Here we report a non-noble metal bifunctional catalyst, Ni–W/ZrO₂, featuring Ni metal sites for (de)hydrogenation and WO_x acid sites for C–C bond cleavage and isomerization. The catalyst enables complete conversion of low-density polyethylene (LDPE, M_w = 96.4 kDa, Đ = 4.6) under mild conditions (250 °C, 3 MPa H₂) within 10 h, affording a high liquid fuel yield of 75.6 wt%. The liquid products are dominated by branched alkanes (C5–C20) with a branching index of 85.6%, affording a high research octane number of 88.9, which is comparable to that of commercial gasoline (86.6). Compared to existing non-noble metal systems, Ni–W/ZrO₂ exhibits superior catalytic activity and effectively suppresses methane formation. Mechanistic analyses reveal the generation of partially electropositive Ni species that promote C–H bond activation. The catalyst also demonstrates excellent durability over five consecutive cycles and broad compatibility with various polyolefin wastes, providing a cost-effective and scalable strategy for sustainable plastic waste valorization.