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End-of-Life Treatment of Poly(Vinyl Chloride) and Chlorinated Polyethylene by Dehydrochlorination in Ionic Liquids

Authors

  • Daan Glas,

    1. Centre for Surface Chemistry and Catalysis, Department of Microbial and Molecular Systems, KU Leuven, Kasteelpark Arenberg 23, box 2461, 3001 Leuven (Belgium)
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  • Joris Hulsbosch,

    1. Centre for Surface Chemistry and Catalysis, Department of Microbial and Molecular Systems, KU Leuven, Kasteelpark Arenberg 23, box 2461, 3001 Leuven (Belgium)
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  • Prof. Philippe Dubois,

    1. Laboratory of Polymeric and Composite Materials, Center of Innovation and Research in Materials and Polymers, University of Mons, Place du Parc 23, 7000 Mons (Belgium)
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  • Prof. Koen Binnemans,

    1. Division for Molecular Design and Synthesis, Department of Chemistry, KU Leuven, Celestijnenlaan 200F, box 2404, 3001 Leuven (Belgium)
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  • Prof. Dirk E. De Vos

    Corresponding author
    1. Centre for Surface Chemistry and Catalysis, Department of Microbial and Molecular Systems, KU Leuven, Kasteelpark Arenberg 23, box 2461, 3001 Leuven (Belgium)
    • Centre for Surface Chemistry and Catalysis, Department of Microbial and Molecular Systems, KU Leuven, Kasteelpark Arenberg 23, box 2461, 3001 Leuven (Belgium)

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Abstract

There is an urgent need for green technologies to remove halogens from halogenated polymers at the end of their lifetime. Ionic liquids (ILs) were used to dehydrochlorinate and/or dissolve the chlorinated polymers poly(vinyl chloride) (PVC) and chlorinated polyethylene (CPE). The dehydrochlorination activity of an IL depends mainly on its anion and is related to the high hydrogen-bond-accepting ability (β value) of the anion. Different phosphonium ILs successfully dissolve and dehydrochlorinate PVC and CPE at temperatures from 80 °C. PVC is dehydrochlorinated up to 98 % after 60 min in tetrabutylphosphonium chloride ([P4444][Cl]) at 180 °C. PVC pieces stabilized by calcium stearate (4 mm3) are dehydrochlorinated more slowly; conversions of 85 and 96 % are reached after 1 and 8 h, respectively. Smaller pieces are dehydrochlorinated faster. High loadings, for example, 0.3 g stabilized PVC in 0.5 g IL, can be applied with only a minor loss of conversion. [P4444][Cl] proved to be stable during several consecutive reactions; after each run more than 99 % of the IL can be recovered. The structure of the dehydrochlorinated PVC was studied by 13C cross-polarization magic-angle spinning NMR and FTIR spectroscopy; the removal of Cl and the formation of double bonds were confirmed. Carefully dehydrochlorinated CPE was processed further by acyclic diene metathesis depolymerization with ethylene and the Hoveyda–Grubbs second-generation catalyst to yield α,ω-dienes such as 1,5-hexadiene and 1,6-heptadiene.

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