(516d) Investigating Cation Effects for Deep Eutectic Solvents (DES)-Catalyzed PET Depolymerization and Recycling

Polyethylene Terephthalate (PET) polymer materials are broadly used in materials such as, clothing, packaging, and plastic storage containers. To mitigate the detrimental environmental and public health effects of plastic and microplastic pollution, new solutions are necessary for the recycling and upcycling of plastic waste. Currently, PET and other plastic wastes are primarily recycled mechanically through a series of processes including cutting, crushing, and melting resulting in material degradation over repeated use¹. Alternatively, chemical recycling via the depolymerization of PET to the bis(2-hydroxyethyl) terephthalate (BHET) monomer offers a promising avenue towards closing the plastic loop and mitigating plastic and microplastic pollution.

Recently, Deep Eutectic Solvents (DESs) have been demonstrated as a promising medium to catalyze PET depolymerization. These materials - which are a mixture of two or more components that form a eutectic mixture - offer several favorable properties including relatively low cost, high thermal and electrochemical stability, and low volatility. Furthermore, DESs offer high solubility for metal salts necessary for catalyzing the reaction in the absence of water. In this work, we focus on the application of type (I) DES materials comprised of metal chlorides and quaternary ammonium salts as catalysts for PET depolymerization. Specifically, we investigate the influence of a series of metal chlorides (MCl_n) for catalyzing PET depolymerization and characterize the depolymerization kinetics, reaction temperature, and the DES to PET mass ratios for batch depolymerization. This work provides important insights towards generating a sustainable and commercially viable process.

(1) Cao, F.; Wang, L.; Zheng, R.; Guo, L.; Chen, Y.; Qian, X. Research and Progress of Chemical Depolymerization of Waste PET and High-Value Application of Its Depolymerization Products. RSC Adv. 2022, 12, 31564–31576.