Upcycling polyolefins to methane-free liquid fuel by a Ru1-ZrO2 catalyst

Abstract

Upcycling waste plastics into liquid fuels presents significant potential for advancing the circular economy but is hindered by poor selectivity and low-value methane byproduct formation. In this work, we report that atomic Ru-doped ZrO2 can selectively convert 100 grams of post-consumer polyethylene and polypropylene, yielding 85 mL of liquid in a solvent-free hydrocracking. The liquid (C5-C20) comprises ~70% jet-fuel-ranged branched hydrocarbons (C8-C16), while the gas product is liquefied-petroleum-gas (C3-C6) without methane and ethane. We found that the atomic Ru dopant in the Ru-O-Zr moiety functionalizes its neighboring O atom, originally inert, to create a Brønsted acid site. This Brønsted acid site, rather than the atomic Ru dopant itself, selectively governs the internal C−C bond cleavage in polyolefins through a carbonium ion mechanism, thereby enhancing the yield of jet-fuel-ranged hydrocarbons and suppressing methane formation. This oxide modulation strategy provides a paradigm shift in catalyst design for hydrocracking waste plastics and holds potential for a broad spectrum of applications.