PROCESS FOR DEPOLYMERIZING POLYETHYLENE TEREPHTHALATE (PET) BY GLYCOLYSIS WITH ETHYLENE GLYCOL, AND PLANT FOR CARRYING OUT THE SAME

摘要

Process for depolymerizing a polyethylene terephthalate (PET) by glycolysis with ethylene glycol (EG), and plant for carrying out the same. Initially, PET is mixed in the solid state with EG at a temperature from 60°C to 120°C, so as to form a heterogeneous mixture with an EG:PET weight ratio (R1) between 0.1 and 3.0, which is then pressed so as to squeeze out an aliquot of EG. The compressed mixture is then fed to a reactor, preferably a paddle reactor, wherein the mixture is heated and kept under mixing at a temperature from 170°C to 270°C, with an EG:PET weight ratio (R2) from 0.1 to 4.0, so as to glycolize the PET and obtain a glycolyzed product containing bis(2-hydroxyethyl) terephthalate (BHET) and/or oligomers thereof. This process has many advantages, including the possibility of treating waste PET as such, the reduction of the EG to PET ratio necessary for glycolysis that allows the reaction to be carried out at relatively high temperatures (230°C and above) so as to obtain an increase in the speed of the process.