(2025) Polymer Testing_Thermochemical methanolysis-based recyclability of polyethylene terephthalate (PET) via pseudo-catalytic depolymerisation

Kwon D.; Lee D.; Lee J.; Kim J.Y.; Kwon E.E.

(Elsevier Ltd) Polymer Testing ISSN: 1429418 Vol.153 Issue. Article No.109051 DOI: 10.1016/j.polymertesting.2025.109051

The global production and consumption of polyethylene terephthalate (PET) have continued to rise, accounting for approximately one-quarter of total plastic output. Currently, PET is derived from fossil-based resources, and the majority of used PET follows a linear, single-use trajectory, ultimately contributing to environmental burdens. While PET has contributed to modern convenience, the alarming statistic that nearly one million PET bottles are discarded every minute emphasises the urgent need to reassess the sustainability of its current production and disposal practices. In this study, a catalyst-free depolymerisation technology, termed pseudo-catalytic transesterification, was developed as a sustainable valorisation approach for the recovery of resources from PET. This approach enabled rapid depolymerisation, achieving high yields of dimethyl terephthalate (DMT, 75.0 %) and ethylene glycol (EG, 17.0 %) within 1 min at 400 °C. Dimethyl carbonate (DMC) was introduced as a (co) solvent to enhance monomer recovery. A 1:1 M ratio of methanol:DMC yielded the highest DMT and EG recoveries outperforming methanol alone. However, excessive DMC promoted ethylene carbonate (EC) formation, thereby reducing the EG yield. Under optimised conditions, the process achieved a recycled PET (rPET) conversion of 68 % with an estimated economic value of $4392 per tonne of rPET. Although the production cost remains higher than that of fossil-based PET, this approach offers substantial environmental benefits by reducing 2 tonnes of CO₂ emissions per tonne of recycled PET waste. © 2025 The Authors.

This study was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean Government (MSIT) (No. RS-2025-00556963 and RS-2023-NR077231 ). Dohee Kwon acknowledges financial support from the Hyundai Motor Chung Mong-Koo Foundation .