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Reaction of poly(vinyl chloride) (PVC) with 5 equiv. of triethyl silane in THF, in the presence of in situ generated (xantphos)RhCl catalyst, results in partial reduction of PVC via hydrodechlorination to yield poly(vinyl chloride- co -ethylene). Increasing catalyst loading or using N , N -dimethylacetamide (DMA) as a solvent both diminished selectivity for hydrodechlorination, promoting competitive dehydrochlorination reactions. Reaction of PVC with 2 equiv. of sodium formate in THF in the presence of (xantphos)RhCl affords excellent selectivity for hydrodechlorination along with complete PVC dechlorination, yielding polyethylene-like polymers. Higher catalyst loadings were necessary to activate PVC towards reduction in this case. In contrast, reaction of PVC with 1 equiv. of NaH in DMA, in the presence of (xantphos)RhCl, exhibited good selectivity for dehydrochlorination, as well as much higher reaction rates. These results combined shed light on the interplay between critical reaction parameters that control PVC's mode of reactivity.
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This content will become publicly available on February 3, 2026
Enhancing Rate and Selectivity for Hydrodechlorination of Poly(Vinyl Chloride) with Rh Catalysts
Abstract Hydrodechlorination of poly(vinyl chloride) (PVC) directly to polyethylene (PE) represents a way to repurpose PVC waste, while avoiding toxic and/or corrosive byproducts that are produced at the end of life of PVC items. Prior studies identified a rhodium‐catalyzed route to hydrodechlorinate PVC to form PE products with sodium formate as a hydrogen source. While all chlorine could be removed to form PE‐like polymers, the reaction was slow and side reactions introduced undesirable cross‐links in the polymer product. In this work, mechanistic studies are pursued to improve catalytic activity for this method. Xantphos and diphenylphosphinoethane (DPPE) both support Rh(I) to promote this reaction to full conversion, effectively removing all chlorine from PVC samples, with Xantphos support providing the fastest metal catalysis for hydrodechlorination to date. However, side reactions to form cross‐links are present for both catalyst systems. Control studies suggest the proposed route for cross‐link formation also deactivates the Rh catalyst, indicating the cross‐link formation can also be the cause for the reaction to slow over time. Other reaction conditions were found to influence the selectivity between hydrodechlorination and cross‐link formation. These results introduce key catalyst design principles to improve methods for hydrodechlorination of PVC, allowing for sustainable repurposing of this toxic polymer waste.
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- Award ID(s):
- 2203756
- PAR ID:
- 10642652
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- ChemSusChem
- Volume:
- 18
- Issue:
- 11
- ISSN:
- 1864-5631
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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