Biobased dimethyl isosorbide as an efficient solvent for alkaline hydrolysis of waste polyethylene terephthalate to terephthalic acid

Recycling spent polyesters, a widely used type of plastic, is highly important for a circular economy but remains a great challenge. Herein, biomass-derived dimethyl isosorbide (DMI) was developed as an emerging solvent for recycling waste polyethylene terephthalate (PET). DMI showed a good ability to rapidly dissolve PET in 10 min at 170 °C to obtain a solubility of 0.3 gPET gDMI−1, originating from the matched Hansen solubility parameters between PET and DMI. Moreover, the dissolved PET in DMI could be regenerated with a PET degradation ratio of only 2.9% using water as an anti-solvent. More importantly, DMI-based solvents were highly effective for alkaline (KOH) hydrolysis of PET to generate terephthalic acid (TPA). In a solvent composed of DMI and ethylene glycol (EG) with a volume ratio of 6 : 4, complete conversion of PET could be achieved in 30 min at 100 °C, and the yield of TPA was nearly quantitative (99.6%). Systematic investigation revealed that the good performance of DMI/EG mixed solvents resulted from the formation of hydrogen-bonding interactions between DMI and EG. The renewability and good performance for PET recycling confirmed the great potential of DMI in practical applications of recycling waste plastics.