Imidazolium‐Based Ionic Liquids for PET Glycolysis: A Sustainable Approach for Plastic Waste

The chemical recycling of polyethylene terephthalate (PET) offers a promising route for recovering valuable monomers from postconsumer plastic waste. This study investigates imidazolium‐based ionic liquids as facilitators for the glycolytic depolymerization of PET and evaluates their performance under systematically varied reaction conditions. Two ionic liquids, 1,3‐dimethylimidazolium methyl sulfate (D2) and 1‐vinylimidazolium dimethyl sulfate (V2), were synthesized and characterized using Fourier‐transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance ( 1 H NMR), and thermogravimetric analysis (TGA). The effects of ionic‐liquid concentration, reaction temperature, and reaction time on PET conversion and bis(2‐hydroxyethyl) terephthalate (BHET) yield were investigated. Among the tested ionic liquids, D2 exhibited superior performance to V2, achieving complete PET conversion (100%) and a BHET yield of 75% at 5 wt% D2, 200°C, and 2 h. TGA demonstrated greater thermal stability of D2 compared with V2, while FTIR analysis confirmed the formation of BHET following PET depolymerization. Scanning electron microscopy revealed distinct surface morphologies for the two ionic liquids, with D2 exhibiting a more uniform and compact structure. The results demonstrate that the performance of imidazolium‐based ionic liquids is strongly influenced by their structure and reaction conditions. The glycolysis by D2 provides an effective route for PET depolymerization and BHET recovery, offering a potential strategy for integrating chemical recycling into circular polymer production.