Upcycling of Polyethylene through Sustainable Introduction of In-Chain Amides Using Zeolite Catalysis

Abstract

The incorporation of heteroatoms in the polyethylene backbone enables chemical recycling through chemolysis. In this work, ketone-functionalized polyethylenes (kf-PEs) are converted into amide-functionalized PEs (af-PEs) through ammoximation and Beckmann rearrangement. The ammoximation involves the in situ production of NH₂OH from base chemicals NH₃ and H₂O₂, using a heterogeneous TS-1 catalyst, and allows us to convert up to 91% of the ketones to oximes. The subsequent Beckmann rearrangement was investigated using heterogeneous Brønsted acidic zeolite catalysts. H-ITQ-2, a delaminated zeolite with MWW topology, was found to be the most effective catalyst, converting up to 80% of oximes into in-chain amides. Both the external surface area and the amount of Brønsted acid sites are found to be key factors in the reaction. Finally, it is shown that the obtained af-PE can be depolymerized through ammonolysis coupled with hydrogenation in a one-pot system, highlighting its applicability for chemical recycling.