Kinetics of catalytic degradation of polycarbonate in benzene

Abstract

The degradation kinetics of polycarbonate [poly(bisphenol A carbonate)] in benzene catalyzed by commercial (rutile) TiO₂ (BET surface area = 11 m²/g), anatase TiO₂ (156 m²/g), and 1 atom % Pt/TiO₂ (111 m²/g), prepared by the solution combustion technique, was investigated at various temperatures (230-280 °C) and 50 atm. The time evolution of the molecular weight distribution (MWD) was determined by gel permeation chromatography (GPC) and modeled with continuous distribution kinetics to obtain the degradation rate coefficients. The rate coefficients for the catalytic degradation of polycarbonate increased by factors of 20, 3.5, and 1.3 compared to the rate coefficients for thermal degradation when catalyzed by nanosized TiO₂ anatase, Pt/TiO₂ anatase, and commercial TiO₂, respectively, at 280 °C. The increased catalytic activity of combustion for synthesized TiO₂ and 1% Pt/TiO₂ might be due to the increased acidity and BET surface area. The activation energies, determined from the temperature dependencies of the rate coefficients, were 16.3, 21.5, and 39.1 kcal/mol for commercial TiO₂, combustion-synthesized Pt/TiO₂, and anatase TiO₂, respectively.