Continuous Flow Depolymerization of Polycarbonates and Poly(lactic acid) Promoted by Supported Organocatalysts

Abstract

Mechanical recycling methods are a simple and effective approach to recycling plastics, but they often result in a direct reduction in the quality of the virgin polymer. Alternatively, chemical recycling of plastic waste provides a closed-loop pathway that could offer a solution to the current end-of-life mismanagement of plastics. However, harsh reaction conditions, scalability, and product purification can limit the applicability of this process on a large scale. Here, an organocatalyzed continuous flow depolymerization strategy is proposed for two soluble, commonly used plastics, poly(lactic acid) (PLA) and bisphenol A polycarbonate (BPA-PC). This process used glycolysis to upcycle PLA to alkyl lactate and BPA-PC to bisphenol A and ethylene carbonate under mild reaction conditions (up to 60 °C). The complete depolymerization of both polymers is initially performed under batch conditions, allowing the solvents and catalysts to be screened. The process is further extended under continuous flow to explore catalyst stability and process scalability. Finally, it is demonstrated that alkyl lactate, bisphenol A and ethylene carbonate can be produced from waste polycarbonate and PLA, thus providing safe and economical access to these species through continuous flow depolymerization of plastic waste.