Sustainable Valorization of Polyethylene into Liquid Fuels via Fe ⁰ /USY-Catalyzed Hydropyrolysis: Insights into Catalyst Design and Hydrogenation Mechanisms

Hydropyrolysis is a sustainable valorization approach for converting plastic waste into valuable fuels, driven by metal-acid bifunctional catalysts through tandem catalysis under a H2 atmosphere. This study presents a sustainable resource management approach for converting polyethylene (PE) waste into high-value liquid fuels through Fe0/USY-catalyzed hydropyrolysis, with a focus on elucidating catalyst design strategies and hydrogenation mechanisms. The developed Fe0/USY bifunctional catalyst synergistically integrates metallic Fe0 sites for efficient hydrogenation with USY acid sites for controlled cracking, achieving an oil yield of 58.1% rich in C6–C10 hydrocarbons at 500°C. The Fe0 sites exhibit excellent hydrogenation activity that suppresses coke formation by converting alkene intermediates into alkanes under a H2 atmosphere. Comparative studies under H2 and N2 revealed the critical role of H2 in enhancing oil yield and improving product quality, while mechanistic studies further clarified that H2 dissociation and hydrogenation occur predominantly on Fe0 sites, whereas H2 alone over USY acid sites shows limited hydrogenation activity. These findings provide foundational insights into metal-acid tandem catalysis for plastic valorization and establish Fe0/USY as a benchmark system, offering a scalable and economically viable route for sustainable waste-to-fuel conversion within a circular economy framework.