Alkali Depolymerization of Poly(ethylene terephthalate) in a Quasi-solid-solid Kneading Reaction

The alkaline depolymerization reaction of poly(ethylene terephthalate) (PET) under quasi-solvent-free conditions was investigated. This is a new approach for recycling PET waste to its monomer building blocks: terephthalic acid and ethylene glycol. The influence of base particle size, reaction temperature, and rotational speed of the employed laboratory kneader on terephthalic acid yield in the quasi-solid-solid reaction was investigated. PET is depolymerized almost quantitatively in a reaction time of 5 min at moderate reaction temperatures, with intense mixing affecting the yield of terephthalic acid. The quality of the terephthalic acid monomer, assessed by color index measurements, indicated that the reaction temperature primarily influences the color index of the monomer. By balancing terephthalic acid yield versus color index, optimum reaction conditions were proposed.

Automated summary

The study investigated the alkaline depolymerization reaction of PET under quasi-solvent-free conditions, providing a new approach for recycling PET waste. Adjustment of base particle size, reaction temperature, and mixing speed can influence the yield of terephthalic acid. PET can be depolymerized almost quantitatively at moderate reaction temperatures, with the quality of the terephthalic acid monomer primarily influenced by the reaction temperature.