Effect of Cellulose and Polypropylene on Hydrolysis of Polyethylene Terephthalate for Chemical Recycling

We examined the hydrolysis of polyethylene terephthalate (PET) with added polypropylene or cellulose and measured the yield of the terephthalic acid (TPA) monomer recovered. The TPA yield from hydrolysis at 250 °C for 30 min nearly doubled from 40 to 75% with the addition of polypropylene (PP). It increased to 55% with the addition of cellulose. There were no statistically significant increases in TPA yield from hydrolysis with the added plastic or biomass at 300 or 350 °C. The solid material recovered from the hydrolytic depolymerization, after first recovering water- and dichloromethane-soluble compounds, was largely TPA, and the amounts of the other reaction products present with it were largely the same irrespective of the presence or absence of PP or cellulose in the reactor. The TPA yield was affected strongly by the reaction time, reaction temperature, and PET type (fiber-reinforced pellet vs chips from a water bottle). The addition of PP or cellulose to the reactor reduces the influence of reaction time on TPA yield from PET hydrolysis.