Predicting Kinetics of the PET Glycolysis Reaction Using an Activity-Based Model and Experimental Validation

Currently, only empirical methods are available for modeling the polyethylene terephthalate (PET) glycolysis reaction, which do not have any predictive power, and thus, these rely heavily on experimental data and are limited to a certain operation window. This causes extensive experimental efforts to explore the optimal operation window by varying reactant ratio, catalyst concentration, temperature, and cosolvent effects. Experimental data regarding the temperature and cosolvent (γ-valerolactone (GVL)) effects were presented in our previous work (M. Schlüter et al., Boosting the kinetics of PET Glycolysis, Reaction Chemistry & Engineering). In the present work, new experimental data on reactant ratio and catalyst concentration were provided. These data served as the foundation for developing and validating a predictive model that aims to ascertain the impact of reactant ratio, catalyst concentration, temperature, and GVL effects on the kinetics of the PET glycolysis. To this end, the ePC-SAFT thermodynamic equation of state was employed to develop an activity-based model for the PET glycolysis reaction. Additionally, the thermodynamic activity of the catalyst zinc acetate (ZnAc2) was included, enabling the incorporation of catalyst interactions in the liquid reaction phase. Furthermore, the influence of temperature on the reaction equilibrium and kinetics was embedded into the activity-based model by applying the linear form of the Van't Hoff equation and the Arrhenius approach. As a result, ΔRh0 = 57 kJ mol–1, ΔRs0 = 98 J mol–1 K–1, and EA = 105 kJ mol–1 were identified.