Selective recovery of para-xylene from polyethylene terephthalate plastic

Abstract

The conversion of polyethylene terephthalate (PET) plastic into low-boiling monomers like para-xylene (PX) that can be purified easier with lower energy consumption represents a promising strategy for circular economy that seamlessly integrating into current prevailing high-quality PET production chain. Herein, a selective bimetallic RuFe catalyst was successfully fabricated for hydrodeoxygenation (HDO) of dimethyl terephthalate (DMT) (a model compound of PET) and PET plastics to PX with yield as high as 88.9 % and 82.6 %, respectively, comparable to state-of-the-art examples. H2-TPR and EXAFS combined with benchmark test over model catalysts confirmed that small Ru clusters and Ru-Nx coordination are responsible for the high aromatics selectivity, on which vertical adsorption of carbonyl group (CO) is preferred. This study not only shows a promising PX-based PET recycling route, the highly selective C–O bond cleavage on Ru catalyst and corresponding structure-selectivity relationship also guide the catalyst design for other value-added biomass-based HDO reactions.