(243h) The Catalytic Hydrocracking of Poly(Ethylene-co-Vinyl Alcohol) Multilayer Films

Hydrocracking of polyolefins has emerged as a promising route to transform plastic waste into platform chemicals at mild reaction conditions. However, most current hydrocracking studies are limited to feedstocks of single-component polyolefins, such as low-density polyethylene (LDPE) or polypropylene (PP). Yet, post-consumer plastics contain many complex polymeric materials, which have not been proven compatible with hydrocracking catalytic systems. One such fraction of complex plastic waste is multilayer film plastic packaging (MF), produced on a scale of ~100 million tons/year¹. MFs cannot be directly mechanically recycled and are mostly landfilled or incinerated, making them a good candidate for catalytic methods.

Herein, we uncover a new mechanistic framework for the direct, solvent-free hydrocracking of EVOH/LDPE blends, used as a surrogate for MFs, into considerable yields of hydrocarbon liquid products at mild conditions. The reaction pathway of EVOH over a bifunctional metal/acid catalyst to form water and hydrocarbons is elucidated. Subsequently, the critical role of acidity in the dehydration of EVOH is unveiled. High yields (58%) of isomerized C₅-C₁₂ hydrocarbons are achieved from EVOH/LDPE blends in short reaction times (2 h) and mild conditions (250 °C). Extensive characterization of the catalyst, products, and remaining solid is completed to explain structure-reactivity relations. Moreover, key similarities and differences are identified between the hydrocracking of EVOH and LDPE. Finally, these fundamental insights are employed to achieve the single-pot hydrocracking of real MFs into high yields of hydrocarbon products.

References:

1. Lithner, D.; Larsson, Å.; Dave, G., Environmental and health hazard ranking and assessment of plastic polymers based on chemical composition. Science of the total environment 2011, 409 (18), 3309-3324.