Catalyst‐Free Upcycling of Polyethylene Waste Into Oxidized Polyethylene Wax

Abstract

ABSTRACT Polyethylene (PE) accounts for 36% of the total plastic waste by mass. However, its inherent chemical stability poses significant challenges for chemical recycling, including energy‐intensive processing, costly catalysts, and thermodynamic constraints that result in low‐value hydrocarbon products. Herein, we present a catalyst‐free, one‐pot hydrothermal oxidation strategy for the efficient upcycling of waste PE into high‐value oxidized polyethylene wax (OPEW). Notably, under optimized conditions (160°C, 1.5 MPa O 2 ), low‐density polyethylene (LDPE, 1.0 g) is converted to OPEW within 0.5 h, achieving an OPEW/PE mass ratio of 103.3% and a carbon yield of 99.8%. The resulting OPEW exhibits a tunable acid number (20–70 mg KOH/g) and saponification number (5–80 mg KOH/g), covering industrial specifications for commercial wax products. Mechanistic studies reveal that the superoxide radical (·O 2 − ) plays a key role in mediating the reaction. Furthermore, 30‐fold scale‐up trials and successful application to various types of PE waste feedstocks demonstrate the great potential of this methodology for industrial viability. This strategy establishes a sustainable, catalyst‐free pathway for upcycling plastic waste into functional materials.