Depolymerization of waste poly(ethylene terephthalate) into bis (2-hydroxyethyl) terephthalate: Catalytic glycolysis mechanism and kinetics

Polyethylene terephthalate (PET) does not readily degrade in nature, leading to the accumulation of large quantities of PET waste in the ecosystem, posing a threat to both terrestrial and aquatic life. Consequently, proper recycling of post-consumer PET has become imperative for our society. This review focuses on PET glycolysis, emphasizing its associated mechanisms and kinetics. The degradation mechanisms are systematically summarized from the perspectives of homogeneous, pseudohomogeneous, and heterogeneous catalytic systems. Homogeneous catalysts demonstrate effective degradation but lack environmental friendliness, and are challenging to separate from the product for subsequent reuse. Conversely, pseudohomogeneous and heterogeneous catalysts offer greater stability and recyclability, rendering them advantageous for sustainable industrial-scale production. Moreover, this review surveys kinetic studies of PET glycolysis, categorizing them into homogeneous and heterogeneous systems. A comprehensive understanding of the kinetic modeling of various degradation processes is deemed essential for the design of efficient glycolytic reaction systems in the future.