High Atom-Economy Low-Temperature Depolymerization of Polyethylene Terephthalate Using Choline Hydroxide

Abstract

This study investigates the low-temperature depolymerization of polyethylene terephthalate (PET) using near-stoichiometric choline hydroxide (ChOH) in methanol, assisted by dichloromethane (DCM) or dimethoxymethane (DMM) as co-solvents. The DCM-assisted system enables rapid apparent PET depolymerization within 30 min under mild conditions, whereas the DMM-assisted system achieves hydrolysis within 20 h at room temperature, yielding choline terephthalate and ethylene glycol. Although slower, the DMM-assisted process proceeds more smoothly, as supported by spectroscopic and microscopic analyses, while the DCM-assisted route leads to accumulation of partially hydrolysed intermediates and transient micro/nanoplastic residues during the early stages of hydrolysis. The studied processes exhibit high atom economy due to the near-stoichiometric use of choline hydroxide and simplified product isolation without acid neutralization or extensive purification steps. In addition, benchmarking based on energy and environmental metrics was extended to account for multistage operations such as solvent removal, drying, and metathesis processes, enabling more comprehensive comparison with previously reported PET depolymerization methods. The results highlight the importance of balanced benchmarking when evaluating sustainability claims in chemical plastic recycling and demonstrate the potential of choline hydroxide-mediated PET hydrolysis as a low-temperature and resource-efficient depolymerization strategy.