A self-regenerative Sn–W/γ-Al2O3 catalyst for low-carbon and scalable polyolefin upcycling via tandem dehydrogenation–metathesis

Abstract

Polyolefin plastics, though highly resistant to degradation due to their thermodynamic stability and chemical inertness, can be catalytically depolymerized into liquid fuels, offering a promising route to mitigate white pollution and fossil fuel dependency. Here, a sustainable catalytic route for closed-loop polyolefin upcycling is achieved using a bifunctional Sn₁W₉/γ-Al₂O₃ catalyst that integrates redox and acidic functionalities within a self-regenerative hydrogen relay cycle. The optimized interface between Sn and W species promotes simultaneous C–H dehydrogenation and C–C metathesis via dynamic Sn–H ↔ W–OH coupling, enabling quantitative conversion of polypropylene at 250 °C within 1 hour and selective production of C₅–C₂₂ liquid hydrocarbons (95.0%). Structural, spectroscopic, and kinetic analyses identify hydroxylated W⁵⁺–OH sites as the principal active centers, stabilized by Sn-mediated hydrogen spillover. The catalyst achieves exceptional stability and reusability across multiple degradation cycles and diverse commercial plastics. Life cycle and techno-economic assessments reveal 16-fold enhanced thermal efficiency, >85% solvent recyclability, and a carbon footprint of 7.3 kg CO₂ e kg⁻¹—surpassing benchmark catalysts in both sustainability and energy utilization. This self-sustaining redox–hydroxyl loop establishes a scalable, low-carbon paradigm for circular plastic valorization. Under mild conditions, the system delivers excellent degradation performance and stability, demonstrating scalability for kilogram-scale recovery.