Complete Recycling of Polyester Wastes with Dialkyl Carbonates.

Abstract

Chemical and biological recycling of spent polyesters is of great significance for solving problems caused by their accumulation, but generally suffering from requirements for high temperature, specific catalysts or enzymes, and incomplete depolymerization in most cases. Here, we report a novel strategy for complete depolymerization of polyesters (e.g., poly(ethylene terephthalate), PET) with dialkyl carbonates (e.g., dimethyl carbonate, DMC) into monomers over halide salts (e.g., tetrabutylammonium chloride, [N4444]Cl) under mild conditions. We demonstrate that PET can be completely degraded into dimethyl terephthalate (DMT) using DMC over [N4444]Cl at temperatures of 80∼120 °C. Based on this reaction, we have achieved highly efficient and complete depolymerization of PET in various PET blend textiles into DMT while preserving the structural integrity of other components including natural and synthetic components. Mechanistic studies reveal the key role of methoxy anion derived from DMC in cleaving the acyl C─O bond of polyesters. Techno-economic assessment for recycling of spent PET wastes demonstrates excellent economic profit.