Iron-based Lewis/Brønsted Deep Eutectic Solvents for the hydrolysis of nylon-6,6

Approximately 1/3 of the global nylon production is accounted for by PA 66, with production levels around 2.5 million tons. To date little end of life options have been developed for PA 66 in spite of its limited biodegradation. In this work, PA 66 is quantitatively depolymerized to the monomers adipic acid and hexamethylene diamine (in the form of diammonium dichloride) by using a naturally abundant iron-based Lewis/Brønsted acidic Deep Eutectic Solvents (LBDESs) in 5 hours at 180 °C. The depolymerization process is quantitative and the yield of the recovered monomers, after the optimization of the reaction conditions and the work-up procedure, exceeds 85%. The process is proved to be effective with virgin polymer in pellets, fibers and also with real post-consumer 100% nylon tights. In addition, the environmental parameters of this process are evaluated and compared with those obtained for other literature processes, indicating that the present process is competitive.