Zero-Waste Chemical Recycling Process of Polyethylene Terephthalate with Closed-Loop Glycolysis and Separation System

This study introduces a sustainable closed-loop glycolysis process for recycling poly(ethylene terephthalate) (PET). Using ethylene glycol (EG) and a zinc methoxide catalyst, PET was effectively depolymerized at 180 °C to produce high-purity bis(2-hydroxyethyl) terephthalate (BHET). Incorporating ethyl acetate (EtOAc) as a cosolvent enhanced BHET solubility at low temperatures, enabling isolation at 25 °C, far lower than conventional water-based methods. This simplified solid–liquid separation yielded BHET with up to 97.8% purity without extensive purification steps. EtOAc, EG, and the catalyst were recovered through vacuum distillation and reused over five cycles with minimal losses, achieving an overall BHET yield of ∼70%. Additionally, isolated byproduct oligomers were converted into dimethyl terephthalate via low-temperature methanolysis at 65 °C, ensuring further valorization of waste materials. Detailed analysis using 1H NMR confirmed product purity and process consistency. This zero-waste strategy reduces energy demand and environmental impact, advancing circular economy approaches for the recycling of PET.