Preparation of Cu-Mg-Al-O catalyst for the hydrodeoxygenation of waste plastic PET monomer into p-xylene

Abstract

More than 400 million tonnes of plastics are produced annually, with PET representing a significant fraction of post-consumer waste. Converting PET-derived monomers into p -xylene (PX) via hydrodeoxygenation (HDO) provides a pathway to both plastic valorization and sustainable aromatics production. Here we report a low-cost Cu–Mg–Al–O catalyst, derived from hydrotalcite precursors, for selective HDO of bis(2-hydroxyethyl) terephthalate (BHET) to PX. Mg incorporation modulates the Cu–support interaction and reducibility of copper species. By systematically varying the Mg/Al ratio and reduction temperature, we identified CuMg 4 Al 1 -350 as the optimal formulation, which delivers complete BHET conversion with 94% PX selectivity at 230 °C and 4 MPa H 2 . This performance arises from a favorable Cu 0 /Cu + balance and high specific surface area. Poisoning tests reveal that Cu + activates the ester carbonyl, whereas Cu 0 facilitates H 2 dissociation. The catalyst gradually loses activity owing to a decline in the surface Cu + /Cu 0 ratio, but its performance is readily restored by calcination–reduction regeneration. This work demonstrates a practical approach for designing earth-abundant Cu-based catalysts for the upcycling of PET waste into valuable aromatic platform chemicals.