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 o C within 1 hour and selective production of C5-C22 liquid hydrocarbons (95.0%). Structural, spectroscopic, and kinetic analyses identify hydroxylated W 5+ -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⁻¹surpassing 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.