Kinetics and Thermodynamics of Neutral Hydrolytic Depolymerization of Polyurethane Foam Waste Using Different Catalysts at Higher Temperature and Autogenious Pressures

Abstract

Neutral hydrolytic depolymerization of the polyurethane (PU) foam waste was done using 0.5 L high pressure autoclave at temperatures of 150°, 180°, 200° and 240°C, the autogenious pressures of 75, 160, 220 and 480 psi and time intervals of 30, 45, 60 and 90 min. The obtained product was characterized by measuring its amine value. The optimum amount of catalysts such as zinc acetate and lead acetate was found to be 1 g. Zinc acetate was more effective catalyst than lead acetate for the depolymerization of PU foam reaction. On the basis of amine value and residual weight of the depolymerized product, the velocity constant was obtained and found to be in order of 10−3 min−1; and the reaction was found to be first order. The energy of activation and frequency factor obtained by an Arrhenius plot were 36.86 kJ mole−1 and 1.349 × 102 mi−1, respectively. The enthalpy of activation at 150°C, 180°C, 200°C, and 240°C was recorded as 43.89, 44.39, 44.72 and 45.37 kJ mole−1, respectively. The entropy of activation at the respective temperatures were recorded as 10.37 × 10−2, 9.79 × 10−2, 9.45 × 10−2 and 8.84 × 10−2 kJ mole−1. The amine was recovered from products of depolymerization reactions.