Effect of anion structure on the ethanolysis of poly(ethylene terephthalate) in imidazolium-based ionic liquids

초록

Depolymerizing waste poly(ethylene terephthalate) (PET) in ionic liquids (ILs) offers an efficient and sustainable route for chemical recycling. In this study, PET was depolymerized using imidazolium-based ILs containing various anions, including acetate, chloride, dimethyl phosphate, methyl sulfate, and nitrate, to elucidate the role of anion structure in depolymerization. Among them, 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc]) exhibited remarkable catalytic activity, achieving complete PET conversion and a diethyl terephthalate (DET) yield of 67 % under optimized conditions, with over 95 % IL recovery after three reuse cycles. The catalytic behavior was rationalized by density functional theory (DFT) and COSMO-RS calculations, which revealed that anion-dependent O-H bond activation and hydrogen-bonding strength strongly influence PET depolymerization. These findings highlight the critical role of IL anion design in promoting efficient and recyclable PET ethanolysis systems.

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