Depolymerization of Polyethylene Terephthalate with Supercritical Methanol

We depolymerized PET in supercritical methanol and observed the yield of DMT at various reaction conditions. At subcritical state below , the yield of DMT was very low, about only 50%. It increased dramatically to 80% at supercritical state above , thereafter the increasing rate was reduced significantly. Similarly, at subcritical state of 6.89 MPa, the DMT yield was only 50%, but it increased abruptly to 85% at supercritical state of 10.34 MPa, yielding no further increase above the pressure. Within 10 minutes after the beginning of the reaction, the DMT yield reached 80%, indicating that the significant portion of the reaction has proceeded, and then, the yield increased slowly. The methanol/PET ratio of 8 showed the maximum DMT yield. We found the optimum depolymerization condition fur PET methanolysis is temperature , pressure 10.34 MPa, reaction time 40 minutes, and methanol/PET ratio of 8.