Chemical Recycling of PET to Its Monomers via Heterogeneous ZnO-Catalysed Ethanolysis

Polyethylene terephthalate (PET) is among the most used plastics in domestic and industrial applications, particularly packaging, food containers and textiles. However, its recalcitrance to decomposition and biodegradation mostly results in landfilling and accumulation of PET waste in the environment if not processed. Chemical recycling of PET via selective depolymerization into its monomers may represent a pivotal step in the development of a truly circular economy of PET, which is still limited by economic and environmental sustainability issues. In this work, the depolymerization of PET is reported using ZnO as an insoluble catalyst, and ethanol as both a lytic agent and green solvent. A detailed investigation of reaction parameters, including reaction temperature, time and catalyst loading, showed that complete conversion of PET to diethyl terephthalate (DET) can be achieved with 92.5% selectivity at 180 °C and 48 h, with the potential for full DET selectivity at longer reaction times. The solid catalyst could be recovered and reused by simple centrifugation, with no loss of conversion or selectivity over three consecutive reuses.