(677c) Electrochemical Co-Production of Chlorine and Hydrogen from Waste Poly(vinyl chloride)

Polymer recycling has garnered considerable attention from scientists, policymakers, and the broader public, as rising plastic pollution increasingly presents environmental and ecological hazards.¹ While numerous chemical and mechanical recycling pathways exist for certain commercial plastics (e.g., polyethylene terephthalate, polyethylene, polypropylene), methodologies for polyvinylchloride (PVC) are limited, as conventional thermochemical processes are stymied by hazardous byproducts.^2,3 Electrochemical processes—which can operate at ambient temperatures and pressures—may enable more suitable reaction conditions, as highly reactive intermediates can be generated on-demand to cleave C–Cl bonds. Within this context, previous work from our group has leveraged PVC as a chlorine source for generating chlorinated arenes, demonstrating a sustainable and versatile route toward value-added products from waste PVC.⁴ Building on this concept, we sought to investigate alternative pathways for both reductive dechlorination and oxidative chlorine utilization.

In this presentation, we will discuss the development of an electrochemical PVC recycling process capable of extracting high-value chlorine and hydrogen directly from waste plastic. Specifically, cathodic hydrogen evolution in the presence of alcohols provides access to reactive alkoxides which rapidly react with PVC to liberate chloride ions. These chloride ions are subsequently oxidized at the anode to yield chlorine—a valuable commodity chemical that can be recycled directly for PVC manufacturing or repurposed in other chemical processes. We begin by investigating the underlying hydrogen evolution kinetics, systematically evaluating electrode materials and supporting electrolytes to understand electrochemical alcohol reduction and confirm alkoxide generation. We then turn toward the dechlorination process, assessing the reactivity between target alkoxides and PVC, quantifying the extent of dechlorination under varying reaction conditions. Finally, we present proof-of-concept chemical recycling experiments, demonstrating the generation of hydrogen and chlorine gases from both synthetic PVC and waste PVC materials. The results of this work may be broadly applicable to electrochemical polymer recycling—a burgeoning area for electrochemistry—providing access to highly reactive intermediates for a wide range of plastics beyond PVC.

References

1. Geyer, J. R. Jambeck and K. L. Law, Production, use, and fate of all plastics ever made. Sci. Adv., 2017, 3, e1700782.
2. Lewandowski and K. Skórczewska, A brief review of poly(vinyl chloride) (PVC) recycling. Polymers, 2022, 14, 3035.
3. K. Jha, B. J. Neyhouse, M. S. Young, D. E. Fagnani, A. J. McNeil, Revisiting poly(vinyl chloride) reactivity in the context of chemical recycling. Chem. Sci., 2024, Advance Article.
4. E. Fagnani, D. Kim, S. I. Camarero, J. F. Alfaro and A. J. McNeil, Using waste poly(vinyl chloride) to synthesize chloroarenes by plasticizer-mediated electro(de)chlorination. Nat. Chem., 2023, 15, 222–229.