Measurement and PC-SAFT Modeling of the Solubility of the BHET Monomer, the BHET Dimer, and PET in Single Solvents

Poly(ethylene terephthalate) (PET) glycolysis is a chemical recycling method to depolymerize PET with ethylene glycol (EG) into the monomer bis(2-hydroxyethyl) terephthalate (BHET). The BHET monomer to BHET dimer formation might occur as well. Solubility is a key property for the depolymerization process, but comprehensive investigations on the solubilities of the BHET monomer, the BHET dimer, and PET are still scarce. Therefore, this study aimed at determining the solubility of the BHET monomer in dimethyl sulfoxide (DMSO), γ-valerolactone (GVL), EG, and H2O between 20 and 86 °C. Additionally, the solubility of the BHET dimer was measured in DMSO, GVL, and EG between 23 and 125 °C, while the solubility of PET was determined in DMSO and GVL between 168 and 192 °C. These measurements were conducted at 1 bar. Besides, the solubility of PET in EG was measured at 4 bar between 225 and 235 °C. Perturbed-chain statistical associating fluid theory (PC-SAFT) was used to model the solubilities accurately. In summary, this research seeks to shed light on the solubility behavior of key components involved in PET glycolysis, whereby PC-SAFT turned out to be a reliable tool with semipredictive character toward PET modeling.