(638b) Catalytic Pathways in the Deconstruction of Ethylene Vinyl Alcohol Copolymer

The search for a solution to the growing accumulation of plastic waste remains a pressing challenge for society, in part due to the heterogeneous nature of the plastic waste stream. In particular, multilayer films (MF) contribute to this problem. MFs are complex, single-use plastics commonly used in food and medical applications, often comprised of several stacked thin-film polymeric components, such as polyethylene (PE), polypropylene (PP), and ethylene vinyl alcohol (EVOH). Direct mechanical recycling of these complex MFs is infeasible. Subsequently, 2Mt of post-consumer MF waste is landfilled or incinerated annually. Alternative waste management strategies must be developed.

Chemically deconstructing MFs into valuable chemicals is a promising method to reutilize this carbon resource. Although significant progress has been made for PE and PP deconstruction, EVOH has been largely ignored. Herein, we demonstrate catalytic hydroconversion for valorizing EVOH into high yields of liquid products (62%) at mild conditions and short processing time (2 h). We complete catalyst and process optimization to tune product selectivity, demonstrating control of both the molecular weight distribution and functionality of products. Extensive characterization of the catalyst was completed, including x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and temperature programmed desorption (TPD); reaction products and remaining solid were also characterized to provide insights into structure-property relations. We establish a mechanistic framework for the hydroconversion of EVOH to explain the formation of liquid products. Moreover, key similarities and differences are identified between the hydroconversion of EVOH and polyolefins. These findings are utilized to design catalysts and reaction systems for the single-pot conversion of polymer mixtures and model MFs.