Biocompatible Ionic Liquids for Sustainable Poly(ethylene terephthalate) Degradation: Conventional vs Microwave Heating Approaches

This study examines three choline-based ionic liquids─choline glycinate, choline phosphate, and choline acetate─as catalysts for poly(ethylene terephthalate) (PET) depolymerization under conventional and microwave heating. Choline glycinate maintained 88–90% PET conversion across both heating methods through its dual-functionality hydrogen bonding network. Choline phosphate and acetate showed method-dependent performance: 90% conversion under conventional heating versus 45–60% under microwave conditions due to viscosity and bonding limitations. All three ionic liquids tolerated up to 30 wt % water under conventional heating and 10 wt % under microwave heating, eliminating dehydration requirements. The heating method controlled product selectivity: conventional heating produced terephthalic acid exclusively, while microwave conditions yielded mixed terephthalic acid and bis(2-hydroxyethyl) terephthalate potentially through water nanodroplets creating localized hotspots. Ionic liquid basicity controls conversion efficiency while heating rate determines product distribution. These results provide a framework for designing rapid, predictable PET recycling processes using biocompatible catalysts.