Concentrated Sulfuric Acid as a Catalyst for Chemical Recycling of Polycarbonate in Water

This work presents the chemical recycling of poly (bisphenol-a carbonate) (PC) pellets with a hydrolysis technique by using concentrated sulfuric acid (H2SO4) as the catalyst in water. The effects of H2SO4 concentration and reaction temperature on the rate of hydrolysis were explored. For that, the values of PC conversion as a function of reaction time were gathered by running PC hydrolysis experiments at H2SO4 concentrations within the range of 10M to 16M and reaction temperatures within the range of 110 to 150 °C. The kinetics of PC hydrolysis were described by considering a pseudo-first-order reaction model, which was consequently applied to calculate specific reaction rate constants. Afterward, the Arrhenius equation was used to determine the overall activation energy of PC hydrolysis. Distillation was used to recover the catalyst (H2SO4) after a PC hydrolysis test so that it is further characterized by titration and reused for PC hydrolysis to study the catalyst reusability. It was shown that H2SO4 can be recovered and reused up to 5 rounds by retaining its acid activity. Also, the effect of hydrolysis on the reduction of PC size was explored. Moreover, a hydrolysis mechanism of polycarbonate by aqueous H2SO4 solution was presented. Graphical Abstract: (Figure presented.)