Highly-Efficient Recycling of Poly(ethylene terephthalate)/Polyethylene Film through Low-Temperature Methanolysis Catalyzed by Nonmetallic Deep Eutectic Solvent.

Abstract

While the poly(ethylene terephthalate) (PET)/polyethylene (PE) multilayer films find extensive applications, particularly in packaging, the recovery of single PE layer or high-purity monomers from these films is seriously hindered by their complex compositions. Herein, a novel low-temperature methanolysis strategy for the highly efficient recycling PET/PE multilayer films with nonmetallic deep eutectic solvent (DES) is developed, where PET can be depolymerized to dimethyl terephthalate (DMT) and ethylene glycol (EG) monomers at 115 °C and 0.45 MPa for 60 min with 100% PET conversion and up to 97.1% DMT yield while PE maintains its stability. The process flow for the high-efficient recycling of PET/PE multilayer films is proposed, consisting of the methanolysis step and two solid-liquid separation ones to obtain the PE, DMT, and EG products. The process optimization, catalyzed mechanism, and swelling behaviors of DES for the PET methanolysis are studied. Finally, the kilogram-scale experiments under best conditions also can obtain 100% PET conversion and 87.8% DMT yield with complete recovery of PE, which efficiently confirms scalability of the proposed recycling pathway. This work establishes a sustainable pathway for closed-loop recycling of multilayer plastics by integrating PE material recovery with PET chemical upcycling.