THE ROLE OF SUPPORTING ELECTROLYTE DURING THE ELECTROCATALYTIC HYDROGENATION OF AROMATIC-COMPOUNDS

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 tetraethylammonium p-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-degrees-C, 1.0 M benzene, 2.5 M 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- or p-toluenesulphonate anions), with product current efficiencies of approximately 40%. When nitrobenzene was hydrogenated with a sodium p-toluenesulphonate supporting electrolyte, only nitro group reduction was observed. When the supporting electrolyte was TEATS, both nitro group reduction and aromatic ring hydrogenation occurred.