Chemical kinetic model and thermodynamic compensation effect of alkaline hydrolysis of waste poly(ethylene terephthalate) in nonaqueous ethylene glycol solution

The depolymerization of waste poly(ethylene terephthalate) (PETW) flakes from bottles was investigated using a nonaqueous NaOH in ethylene glycol solution and was carried out at p(atm) from 150 to 185 degrees C, using a NaOH: PET molar ratio of 4:1. The increasing amount of water taken up by the flakes and after submitting them to thermopressing at 260 degrees C increased the reactivity of the rectangular specimens thermopressed during the depolymerization. At a stirring rate value of 1360 rpm, the product was removed from the unreacted PET surface and the chemical reaction was rate-determining. Using the kinetic model of shrinking core of heterogeneous chemical reaction control, considering the formation and growth of cracks and pores on the polymer surface, the E-a value was 172.7 kJ(.)mol(-1), which was relatively high. However, in the thermodynamic analysis it was shown that the compensation effect of the Delta S-double dagger over the Delta H-double dagger is sufficiently high to compensate for the high Ea.