Kolbe Electrolysis of Mixtures of Aliphatic Organic Acids

Kolbe electrolysis of mixtures of n‐butanoic with n‐hexanoic acid and propanoic with n‐hexanoic acid have been performed in aqueous solution at a smooth platinum anode. Typically, hexane production by the oxidation of butanoic acid, or butane production from propanoic acid, in aqueous solution is not observed to exceed a few percent. In the current work, significant increases of these products were observed. In addition, a substantial fraction of the remaining or acids reacted were converted to mixed alkane dimers with hexanoic acid. These results are interpreted by a model in which n‐hexanoic acid and its various oxidation products form a lipophilic layer at the anode surface which provides an environment where further oxidation to carbonium ions is disfavored. This model has been suggested previously to explain pressure effects on Kolbe electrolysis (1). This observation supports the feasibility of producing mixed linear alkanes for use as fuels and chemicals from mixed organic acids which may be produced by anaerobic fermentation of organic matter.