Catalytic upgrading of polyolefins via oxygenation and in-chain ester formation using Ti and Sn zeolite catalysts

Plastic wastes are so far underexplored as feedstocks for producing ‘upcycled’ materials. This project, focusing on the large available mass of end-of-life polyolefins, aims at selective oxidation of these hydrocarbon-type materials. As a first option, alcohol (and ketone) groups are created along the polyolefin chain. For this, selective Ti-containing zeolites and clean oxidants (e.g. hydrogen peroxide) are applied at mild temperatures, avoiding the adverse aspects of free radical autoxidations. Polyolefins with a small degree of hydroxylation offer great perspectives, e.g. regarding coatability, while preserving most attractive properties of the original polyolefins. Secondly, the ketone groups on the polyolefins are further converted to in-chain esters via a Baeyer-Villiger reaction. Such reaction is enabled by Sn-doped zeolites, using again peroxides. This results in polyethylene-derived polyesters, with attractive new properties like easy degradation by chemolysis, or even self-healing. For both major reaction types, the architecture of the zeolites is adapted to deal with the polymeric nature of the dissolved reactants. Catalyst-polymer interactions are studied in detail, also to facilitate recovery and reuse of the heterogeneous catalysts. Finally, key characteristics of the isolated reaction products (e.g. functionalization, thermal and structural properties) are recorded to facilitate future market adoption of these new materials.