The role of supporting electrolyte during the electrocatalytic hydrogenation of aromatic compounds

TLDR: In this paper, the electrocatalytic hydrogenation of benzene, aniline, and nitrobenzene at a Raney nickel powder cathode was investigated at a single phase electrolyte consisting of t-butanol, water, and a hydrotropic salt, either sodium or tetraethylammoniump-toluenesulphonate (TEATS).

Abstract: The electrocatalytic hydrogenation of benzene, aniline, and nitrobenzene was investigated at a Raney nickel powder cathode. The single phase electrolyte consisted of t-butanol, water, and a hydrotropic salt, either sodium or tetraethylammoniump-toluenesulphonate (TEATS). The hydrogenation of benzene was achieved only in the latter case; the only product detected was cyclohexane. The highest current efficiency (73%) was obtained at 50° C, 1.0m benzene, 2.5m TEATS, and at an apparent current density of 4.0 mA cm−2. Aniline was electrocatalytically hydrogenated to cyclohexylamine only in the presence of a quaternary ammonium ion supporting electrolyte (containing either Br− orp-toluenesulphonate anions), with product current efficiencies of ∼40%. When nitrobenzene was hydrogenated with a sodiump-toluenesulphonate supporting electrolyte, only nitro group reduction was observed. When the supporting electrolyte was TEATS, both nitro group reduction and aromatic ring hydrogenation occurred.