Boosting the kinetics of PET glycolysis†

Glycolysis is the most promising chemical recycling method to depolymerize poly(ethylene terephthalate) (PET) with ethylene glycol (EG) into the monomer bis(2-hydroxyethyl) terephthalate (BHET). Boosting the depolymerization kinetics while staying under comparatively mild and green reaction conditions is required to bring glycolysis to industrial scale utilization. This work suggests achieving this goal by a combined pressure, temperature and co-solvent addition approach. By using the environmentally friendly γ-valerolactone (GVL) as a suitable co-solvent in the traditional PET glycolysis system, and slight temperature and pressure elevation, the kinetics was boosted by almost two orders of magnitude compared to the standard literature process. A kinetic model was employed to describe the kinetics as a function of temperature and GVL concentration. The optimized condition allowed nearly full conversion after 2 minutes only.