One-pot Hydrogenolysis of Polyethylene Terephthalate (PET) to p-xylene over CuZn/Al2O3 Catalyst.

Abstract

Chemical upcycling of plastic wastes into valuable chemicals is a promising strategy for resolving plastic pollution, but economically viable methods currently are still lacking. Here, we report one-pot hydrogenolysis of PET plastic into p-xylene with an excellent yield (99.8 %) over a robust non-precious Cu-based catalyst, CuZn/Al₂O₃, in the absence of alcohol solvents. The presence of Zn species promotes the dispersion of Cu⁰ and increases the ratio of Cu⁺/Cu⁰, whereas the synergistic effect of Cu⁰ and Cu⁺ leads to a superior performance in the conversion of PET. The combination of GC-MS, ¹³C CP MAS NMR, 2D ¹H-¹³C CP HETCOR NMR spectroscopy and kinetic studies for the first time demonstrates 4-methyl benzyl alcohol as an important reaction intermediate in the hydrogenolysis of PET. Mechanistic studies indicate that the conversion of PET mainly follows a hydrogenolysis process, involving the cleavage of ester bonds to alcohols and the C-O bond cleavage of alcohols to alkanes. This work not only brings new insight for understanding the upgrading pathway of PET, but also provides a guidance for the design of high-performance non-precious catalysts for the chemical upcycling of plastic wastes.