Bichloride-based ionic liquids for the merged storage, processing, and electrolysis of hydrogen chloride

Abstract

Hydrogen chloride is produced as a by-product in industrial processes on a million-ton scale. Since HCl is inherently dangerous, its storage and transport are avoided by, e.g., on-site electrolysis providing H₂ and Cl₂ which usually requires complex cell designs and PFAS-based membranes. Here we report a complementary approach to safely store 0.61 kilogram HCl per kilogram storage material [NEt₃Me]Cl forming the bichloride [NEt₃Me][Cl(HCl)<i>_n</i>]. Although HCl release is possible from this ionic liquid by heat or vacuum, the bichloride can be used directly to produce base chemicals like vinyl chloride. Alternatively, [NEt₃Me][Cl(HCl)<i>_n</i>] is electrolyzed under anhydrous conditions using a membrane-free cell to generate H₂ and the corresponding chlorination agent [NEt₃Me][Cl(Cl₂)<i>_n</i>], enabling the combination of these ionic liquids for the production of base chemicals.