Issue 18, 2022

A sustainable way of recycling polyamides: dissolution and ammonolysis of polyamides to diamines and diamides using ammonia and biosourced glycerol

Abstract

In order to make recycling a viable strategy for post-consumer plastics, economically feasible revalorization processes must be developed. The ammonolysis of polyamides can be such a cutting-edge recycling technology; however, due to the rigid structure of these polyamide plastics, operating conditions of current ammonolysis processes are harsh, including high temperatures (>300 °C) and high NH3 pressures. Here, we report a very green and elegant ammonolysis process of the widely abundant polyamide 66 by using a hard Lewis acid catalyst and 1 bar of NH3 in a simple glycol solvent at 200 °C. Computational studies revealed that especially the vicinal diol moiety of these glycol solvents plays a key role in activation of the ammonia nucleophile, with glycerol being the most effective solvent, reaching the depolymerization equilibrium after 20 h even without a catalyst. To our delight, a biosourced glycerol (obtained from the saponification of triglycerides) could also directly serve as a suitable solvent, even outperforming the ammonolysis process in highly purified glycerol.

Graphical abstract: A sustainable way of recycling polyamides: dissolution and ammonolysis of polyamides to diamines and diamides using ammonia and biosourced glycerol

Supplementary files

Article information

Article type
Paper
Submitted
13 jun 2022
Accepted
18 ago 2022
First published
24 ago 2022

Green Chem., 2022,24, 6923-6930

A sustainable way of recycling polyamides: dissolution and ammonolysis of polyamides to diamines and diamides using ammonia and biosourced glycerol

W. Stuyck, K. Janssens, M. Denayer, F. De Schouwer, R. Coeck, K. V. Bernaerts, J. Vekeman, F. De Proft and D. E. De Vos, Green Chem., 2022, 24, 6923 DOI: 10.1039/D2GC02233H

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