Selective Lanthanide-Organic Catalyzed Depolymerization of Nylon-6 to ..epsilon..-Caprolactam: Article No. e202212543

Nylon-6 is selectively depolymerized to the parent monomer e-caprolactam by the readily accessible and commercially available lanthanide trisamido catalysts Ln(N(TMS)2)3 (Ln = lanthanide). The depolymerization process is solvent-free, near quantitative, highly selective, and operates at the lowest Nylon-6 to ..epsilon..-caprolactam depolymerization temperature reported to date. The catalytic activity of the different lanthanide trisamides scales with the Ln3+ ionic radius, and this process is effective with post-consumer Nylon-6 as well as with Nylon-6 + polyethylene, polypropylene or polyethylene terephthalate mixtures. Experimental kinetic data and theoretical (DFT) mechanistic analyses suggest initial deprotonation of a Nylon terminal amido N-H bond, which covalently binds the catalyst to the polymer, followed by a chain-end back-biting process in which ..epsilon..-caprolactam units are sequentially extruded from the chain end.