Towards efficient PET recycling via MHET repolymerization with catalyst-free esterification

The extensive global utilization of polyethylene terephthalate (PET) has generated substantial post-consumer waste, leading to severe resource waste and environmental pollution that make efficient PET recycling an urgent scientific priority. Biological recycling of PET has gained widespread attention owing to mild reaction conditions, but current research predominantly targets the recovery of terephthalic acid, overlooking other key intermediates. This study focuses on the repolymerization of mono(2-hydroxyethyl) terephthalate (MHET), a distinctive intermediate derived from enzymatic depolymerization of PET, into high-quality PET. Under mild, catalyst-free conditions (180 °C, 6 h, atmospheric pressure), the process achieves a high esterification degree (>98%) while effectively suppressing the formation of diethylene glycol (DEG) as a by-product. Compared to PET's traditional polymerization routes, the route provided in this work demonstrates higher atom economy with an atomic utilization of 68.12%. And the resulting PET exhibits comparable properties to commercially available PET. By integrating experimental optimization, kinetic analysis, and environmental assessment, this work advances the practical optimization for the polymerization of PET from MHET, providing effective support for the closed-loop biological recycling of PET.