Polycarbonate ethanolysis with imidazolium-based ionic liquids: Recovery of high-purity BPA and value-added by-product

Depolymerization using ionic liquids (ILs) is an efficient and eco-friendly method for recycling waste poly(bisphenol A carbonate) (PC). To use IL for PC ethanolysis, the effect of IL structure on PC depolymerization should be investigated. In this study, we investigated PC ethanolysis using imidazolium-based ILs with different alkyl chain lengths (ethyl, butyl, and hexyl groups) as both the catalyst and solvent to afford the monomer bisphenol-A and a value-added byproduct, diethyl carbonate. 1-Ethyl-3-methyl imidazolium acetate ([EMIM][Ac]) exhibited the highest depolymerization efficiency, and an additional wash step increased the purity of the recovered BPA. A 100 % PC conversion rate, 90.9 % BPA yield, 99.9 % BPA purity, and 99 % [EMIM][Ac] reusability over five depolymerization cycles were observed in the PC ethanolysis using [EMIM][Ac]. In addition, recovered BPA behaved identically to commercially available BPA in the polymerization of PC. This strategy could help reduce the worldwide production of new BPA for PC synthesis.