Depolymerization of poly(ethylene terephthalate) recycled from post‐consumer soft‐drink bottles

TLDR

Poly(ethylene terephthalate) from post‑consumer soft‑drink bottles is depolymerized by glycolysis in excess ethylene glycol at 190 °C using a metal acetate catalyst. Glycolysis yields mainly bis(hydroxyethyl) terephthalate and its dimer, reaching equilibrium after ≥8 h, with no higher oligomers detected; zinc acetate gives the highest monomer yield, and green pigment does not affect the reaction.

Abstract

Abstract Poly(ethylene terephthalate), recycled from post‐consumer soft‐drink bottles, is depolymerized by glycolysis in excess ethylene glycol at 190°C in the presence of a metal acetate catalyst. The glycolyzed products consist mostly of the PET monomer, bis(hydroxyethyl) terephthalate, and the dimer, and after long reaction time (up to and longer than 8 h), an equilibrium is attained between these two species. No other higher PET oligomers were detected in the study. Of the four metal acetates (lead, zinc, cobalt, and manganese) tested, zinc acetate is the best in terms of the extent of depolymerization, that is, the relative amount of monomer formed. The presence of green pigment in one type of recycled PET apparently has no effects on the glycolysis reaction.