Supercritical carbon dioxide assisted extraction from the polycarbonate depolymerization mixture

Chemical recycling of polycarbonate by depolymerization with phenol produces a mixture of phenol, diphenyl carbonate (DPC) and bisphenol A (BPA). We simulate a semibatch extraction process to separate these components. A supercritical carbon dioxide stream flows into an autoclave containing the depolymerization products. The liquid–vapor two-phase system is considered to be in equilibrium during the isobaric isothermal process as the vapor phase is withdrawn sufficiently slowly, maintaining the autoclave temperature and pressure. The VLE behavior is described by the Peng–Robinson equation of state (PR-EOS), using the interaction parameters of the involved six binary systems as determined in our previous work. PR-EOS is coupled with the molar balance equations to calculate the phase fractions and compositions in the investigated systems. The predictions of the simulations are compared with the experimental measurements during extractions from binary systems phenol–CO2 and DPC–CO2, ternary systems phenol–DPC–CO2 and phenol–BPA–CO2, and quaternary system phenol–DPC–BPA–CO2. We find a reasonable agreement between our predictions and experimental results.