Selective deoxygenation of polar polymers using metal supported on TiO2 nanotubes

Abstract

Polar polymers such as poly(vinyl alcohol-co-ethylene) (EVOH) serve as excellent oxygen barriers in multilayered polymer films. However, their presence creates significant challenges for subsequent recycling. Melting and thermal degradation leave behind small domains of immiscible phases that render the final material less valuable. Here, we report a strategy to selectively remove OH groups from the EVOH polymer while preserving the polymer's hydrocarbon backbone. Pd supported on TiO₂ nanotubes exhibits excellent activity and selectivity for C–O bond scission and hydrogenation. This is evidenced in our study, which utilizes both the model compound 2,5-hexanediol (a small surrogate for polyols) and EVOH. The Lewis-acid sites generated on the TiO₂ surface, coupled with hydrogen dissociation on the metal particles and unique sites at the metal support interface, result in enhanced deoxygenation rates to generate saturated products at atmospheric pressure. The intimacy between Pd particles and their TiO₂ supports for EVOH conversion is also discussed.