Semi-continuous hydrothermal waste valorization: Facile protocol for monomer recovery from poly(bisphenol A carbonate)

This study introduces a novel semi-continuous hydrothermal process for the chemical recycling of poly(bisphenol A carbonate) (PC), focusing on the selective cleavage of bisphenol A (BPA) while minimizing its decomposition. Key operational parameters and reactor design were established through calculations using available kinetic and phase equilibrium data, ensuring that BPA residence time remained within acceptable limits. The design features continuous BPA removal to prevent secondary decomposition. Flow patterns of the system were analyzed using residence time distribution and mathematical deconvolution. At a temperature of 300 °C, pressure of 10 MPa, and a decomposition time of 70 min, the process achieved a 95 % yield of BPA within an average water residence time of approximately 1 minute. High purity of BPA was confirmed through chromatography, NMR spectroscopy, and thermal analysis. The results support a pseudo-solid kinetic behavior for PC hydrolysis, besides establishing a sustainable and efficient pathway for chemical recycling of PC. • Novel back-to-monomer semi-continuous process with neat hydrothermal medium. • Preliminary reactor design successfully hinders bisphenol A decomposition. • Bisphenol A yield curves show conformity to the modified shrinking core model. • Crystalline bisphenol A product only contains low level of phenol as contaminant.