Glycolysis is the transesterification of a polyester with a glycol, and in polymer chemistry it is the most established route for depolymerising poly(ethylene terephthalate) back to monomers. The reaction cleaves the ester linkage with an excess of ethylene glycol and gives bis(2-hydroxyethyl) terephthalate, which can be repolymerised directly [1]. A catalyst is required to reach a useful rate, and zinc, manganese, and titanium compounds are the usual choices, while an ionic liquid can replace the conventional system [2]. The product is a mixture of oligomers whose composition depends on the glycol-to-polymer ratio and on the temperature, so the reaction has to be driven to completion before the monomer can be recovered [3]. The process tolerates coloured and slightly contaminated feedstock, which distinguishes it from mechanical recycling, but the purification of the product stream adds cost [4]. The same chemistry applied to polyurethane and to polycarbonate is less developed, because the alcohol has to be separated from a more complex mixture [5].
- transesterification
- depolymerization
- ethylene glycol
- bis(2-hydroxyethyl) terephthalate
- catalyst
- pet recycling
- oligomer
Recycling and Waste Management Techniques·Industrial and Manufacturing Engineering·Environmental Science·Physical Sciences
References
- Viana, M.E.; Riul, A.; Carvalho, G.M.; Rubira, A.F.; Muniz, E.C. Chemical recycling of PET by catalyzed glycolysis: Kinetics of the heterogeneous reaction. Chemical Engineering Journal 2011, 173, 210-219. [CrossRef]
- Li, Y.; Zheng, J.; Lu, J.; Tang, L.; Zhou, J.; Zhou, X.; Dong, W.; Jiang, M. Magnetic and glycolysis-compatible immobilized Kubu-PM12 for chemoenzymatic cascade depolymerization of PET. Journal of Environmental Chemical Engineering 2026, 14, 123538. [CrossRef]
- Asueta, A.; Arnaiz, S.; Miguel-Fernández, R.; Leivar, J.; Amundarain, I.; Aramburu, B.; Gutiérrez-Ortiz, J.I.; López-Fonseca, R. Viability of Glycolysis for the Chemical Recycling of Highly Coloured and Multi-Layered Actual PET Wastes. Polymers 2023, 15, 4196. [CrossRef]
- Schlüter, M.; Zimmer, J.; Held, C.; Wohlgemuth, K. Enhancing sustainability in PET glycolysis by closed-loop recycling. Chemical Engineering Science 2025, 307, 121337. [CrossRef]
- Bai, Z.; Bao, Z.; Hu, H. Chemical Recycling of Catalytic Glycolysis of Polyethylene Terephthalate with Potassium-Rich Biomass. Recycling 2025, 10, 85. [CrossRef]