Catalytic Upcycling of Barrier Plastic Films by Selective Deoxygenation of Ethylene Vinyl Alcohol over Pd/MoO₃

Multilayer plastic films that combine polar barrier polymers, such as ethylene vinyl alcohol (EVOH), with nonpolar polyolefins, such as polyethylene (PE), are widely used in food packaging, but their recycling remains challenging because of phase separation during reprocessing. Here, we address this limitation through the selective deoxygenation of EVOH over a Pd-promoted molybdenum oxide (MoO₃) catalyst, enabling C-O bond cleavage while preserving the polymer backbone. The catalytic performance was evaluated in both a monophasic γ-valerolactone (GVL) system and a biphasic GVL/decalin system. While the monophasic GVL system achieved moderate oxygen removal of up to 31.62% after 8 h, the biphasic GVL/decalin system significantly enhanced performance, reaching up to 41.1% oxygen removal in only 1 h, corresponding to a 2.4-2.8-fold increase in the reaction rate. Notably, the biphasic system enabled in situ product separation, with nonpolar deoxygenated products partitioning into the decalin phase, thereby reducing product accumulation on the catalyst surface. Applied to a commercial multilayer film containing 80 wt % LDPE and 20 wt % EVOH, the system achieved near-complete deoxygenation of 83.5% after 1 h over Pd5%/MoO₃. Kinetic analysis revealed a positive half-order dependence on H₂ over Pd/MoO₃, highlighting the critical role of Pd in H₂ dissociation and spillover, which facilitates the rate-determining step. Overall, this work establishes an efficient biphasic catalytic platform for upgrading oxygen-containing barrier layers in multilayer plastic films into more recyclable polyolefin-like materials.