Selective Asymmetric Hydrogenation of Waste Polyethylene Terephthalate via Controlled Sorption through Precisely Tuned Moderate Acid Sites

Abstract

The partial hydrogenation of waste polyethylene terephthalate (PET) offers a great opportunity to produce valuable chemicals, yet achieving precise catalytic control remains challenging. Herein, for the first time, we realized one-pot selective hydrogenation of waste PET to p-toluic acid (p-TA) with a record-high yield of 53.4%, alongside a 36.4% yield of p-xylene (PX), using a specially designed PtW/MCM-48 catalyst. Mechanistic investigations revealed that the exceptional catalytic performance arises from synergistic interaction between Pt nanoparticles and WO_x species. Low-valent WO_x enhances Pt dispersion, while Pt stabilizes WO_x as low-polymerized polytungstates. The moderate acidity of PtW_1.5/MCM-48 ensures controlled desorption of p-TA, preventing overhydrogenation to PX. The catalyst demonstrated robust performance with real-world PET waste. Life cycle assessment and technical and economic evaluation further highlight its practical feasibility. This study establishes a sustainable pathway for PET chemical upcycling and provides a framework for designing advanced catalysts for selective hydrogenation reactions, addressing critical challenges in circular chemistry and plastic waste management.