Depolymerization of polycarbonate with catalyst in hot compressed water in fused silica capillary and autoclave reactors

Abstract

Depolymerization of polycarbonate (PC) with the catalyst manganese acetate (Mn(Ac)₂) was studied in hot compressed water (HCW) using a stainless steel batch autoclave reactor and a fused silica capillary reactor (FSCR). The phase behavior of PC in water with or without Mn(Ac)₂ during the heating, reaction and cooling processes was observed. The phase behavior indicated that the dissolution time of PC in HCW to form a homogeneous liquid solution was effectively reduced by adding Mn(Ac)₂ as a catalyst. For the reaction in the autoclave reactor, the main liquid products were bisphenol A (BPA) and phenol. The effects of operating parameters such as catalyst concentration (ratio of Mn(Ac)₂ to PC) (0–2.5%), temperature (250–280 °C) and reaction time (5–60 min) on depolymerization of PC were investigated in the autoclave reactor. The optimal experimental conditions were found to be a temperature of 280 °C, reaction time of 20 min with the ratio of Mn(Ac)₂/PC of 2.0%, giving yields of BPA and phenol of 55.25% and 18.63%, respectively. The main gaseous product CO₂ in the FSCR was qualitatively and quantitatively analyzed by Raman spectroscopy. A reaction pathway for catalytic depolymerization of PC in HCW was proposed based on the experimental results.