High-yield production of lactide isomers from depolymerization of polylactic acid in supercritical carbon dioxide

• Published in: The Journal of supercritical fluids 2025-03, Vol.217, p.106473, Article 106473
• Main Authors: Sivri, Seda, Sezgi, Naime Aslı, Dilek, Cerag
• Format: Article
• Language: English
• Subjects: Depolymerization; Lactic acid; Lactide; PLA; Recycling
• ISSN: 0896-8446
• DOI: 10.1016/j.supflu.2024.106473

Chemical depolymerization of polylactic acid (PLA) was demonstrated in supercritical carbon dioxide medium. No catalyst, organic solvent or water was employed in the reaction. The primary feedstocks used in ring opening polymerization of PLA, lactide isomers, were produced with high yield. More specifically, lactides were produced as the sole nongaseous products with a 93 % yield based on the initial polymer mass at 200 °C and 310 bar in 120 min. The influences of the reaction temperature, time, and pressure on PLA depolymerization products were investigated. While the lactide yield and distribution were highly influenced by the reaction temperature and time, further improvement was attained with an increase in the pressure. The results demonstrate that supercritical CO2 can be applied as a promising reaction medium for PLA degradation, providing a high-yield production of its feedstock. The process can enable green depolymerization of polylactic acid and promote its circular economy with a closed loop production. [Display omitted] •PLA was depolymerized in supercritical CO2 without a catalyst or cosolvent.•93 % yield of lactide isomers were obtained at 200 °C, 310 bar within 120 min.•Solid products consisted solely of the primary feedstocks, lactide isomers.•Lactic acid was produced at higher temperatures and/or prolonged reactions.