Influence of the catalytic system on the methanolysis of polyethylene terephthalate at mild conditions: A systematic investigation

• The huge production volume of plastics imposes a sustainable management of the waste. • PET methanolysis to monomers is applied in industries but at extreme conditions. • We explore different catalysts and cosolvents for PET methanolysis at mild conditions. • Based on quantitative comparisons, we promote a conscious selection of the catalyst. • The process is applied on bottle flakes and textile fibers mixed in cotton and PET. Plastic disposal is becoming a threat to our environment because of the severe lack of technologies producing high-quality polymers from scraps at a competitive cost compared to the virgin versions. Regarding polyethylene terephthalate (PET), different recycling technologies have been proposed, but they have several disadvantages in terms of cost, process flexibility, and safety. This work systematically investigates the efficiency of different catalytic systems in the methanolysis of PET, operated at mild temperature. High-performance liquid chromatography was adopted to assess the depolymerization efficacy and the product distribution, allowing a quantitative comparison between the different catalytic systems. Potassium carbonate and dichloromethane proved to be the best performing catalyst/cosolvent pair, leading to almost complete depolymerization of PET from bottle flakes and high yield to dimethyl terephthalate. On the other side, when treating PET/cotton fabrics, the hydrolysis catalyzed by hydroxyl groups in the cotton hampered the complete PET depolymerization, leaving room for further research.