Catalytically transforming legacy phthalate esters from plastic waste into benzoic acid and benzoate plasticizers

Abstract

In order to manage legacy additives in plastic waste streams, several extraction processes are under development to enable safe reuse of the polymer matrix. Equally important in such closing-the-loop approaches is the formulation of revalorisation strategies for the extracted components, particularly in the context of high-volume additives such as phthalate plasticizers. This study demonstrates the catalytic conversion of real plastic waste-extracted phthalate esters into benzoic acid (BA), via a one-pot hydrolysis-decarboxylation process based on inexpensive Cu2O and H-Beta zeolite, in water as a safe and environmentally benign solvent. As a result of the excellent product selectivity in both reactions, BA was obtained in quantitative yields (> 99%). Esterification of the purified carboxylic acid resulted in the production of an alternative benzoate plasticizer, with a total process yield up to 94%, illustrating a potential revalorisation route for end-of-life legacy phthalate plasticizers.