Catalytic Deconstruction of Ethylene Vinyl Acetate Copolymer and Polyethylene Mixtures via Hydroconversion: Challenges and Solutions

Published in: ACS Sustainable Chem. Eng. 2024, 12, 23, 8717–8728
Authors: Pedro Moura, Pavel A. Kots, Brandon C. Vance, Zoé O.G. Schyns, Sean Najmi, Zachary R. Hinton, Caitlin M. Quinn, Thomas H. Epps III, LaShanda T.J. Korley, and Dionisios G. Vlachos
May 2024
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Abstract:

We explore hydrogenolysis over ruthenium supported on zirconia (Ru/ZrO₂) and hydrocracking over platinum (Pt) supported on zeolites as an effective end-of-life strategy for ethylene vinyl acetate (EVA)─a widely used performance heat sealant in hard-to-recycle multilayer packaging. For Ru/ZrO₂ hydrogenolysis, EVA reacts slower than low-density polyethylene (LDPE) and the catalyst deactivates due to carbonaceous deposits originating from polyenes generated in situ during EVA thermal degradation. High H₂ pressures and temperatures can overcome catalyst deactivation; however, CH₄ yields are excessive due to cascade hydrogenolysis stemming from strong C═C/metal interactions. Polyene hydrogenation allows chains anchored by C═C to desorb from Ru, shifting product selectivity from CH₄ to higher-value liquids. Hydrogenolysis of mixed EVA and linear low-density polyethylene (LLDPE), mirroring typical frozen food packaging formulations, results in comparable catalyst activity and CH₄ yield as the pure EVA resin. For Pt/zeolite hydrocracking, pure EVA and EVA: LLDPE mixtures are deconstructed to propane or light naphtha with minimal CH₄ production. Among catalysts tested, Pt/HY gives the highest liquid productivity (g_C5+products/g_cat·h). These findings showcase the recalcitrant nature of EVA and its associated mixtures for Ru/ZrO₂ hydrogenolysis, highlighting that hydrocracking catalysts may be superior for complex packaging waste.

Keywords: Plastics waste, valorization, Hydrogenolysis, EVA, LLDPE, PE