Rapid hydrolysis of PET in high-concentration alcohol aqueous solution by pore formation and spontaneous separation of terephthalate

Abstract

Recovery of terephthalic acid (TPA) from waste polyethylene terephthalate (PET) should overcome the long-existing issues of low operation efficiency or massive wastewater generation during the hydrolysis and subsequent separation process to balance economics and environmental friendliness. Here, a high-concentration ethanol aqueous solution of 90 vol% is developed to achieve high-efficiency hydrolysis of PET by selectively cleaving C-O bonds and spontaneous separation of terephthalate using KOH as catalyst at 80 °C for 60 min. More than 98 % of TPA is recovered. It was attributed to the accelerated diffusion of the solvent in a reflux state due to the pore formation in PET and improved wettability between the solvent and PET. Notably, the terephthalate precipitated automatically from the reaction system due to low solubility in the solvent and separated by simple filtration, which avoids a large amount of waste water and acid in the following neutralization of terephthalate. The high efficiency of recycled reaction solution remained within several successive runs. The hydrolysis system is also applicable for degradation of other polymers containing ester groups and shows combined advantages of simplicity, high efficiency and eco-friendliness.