Herein, we describe a study of the electrochemical reduction of oxalic and glyoxylic acids toward a feasible green and sustainable production of tartaric acid in aqueous and/or acetonitrile solvent using silver and lead electrodes. Our results show that on the silver electrode, for both oxalic acid and glyoxylic acid, the reduction reaction is more favorable toward the dimerization step, leading to tartaric acid, due to the increase in the local pH, while on the lead electrode, the step involving the protonation of the intermediate is more favorable, leading to the formation of glycolate. Techno-economic analysis shows that tartaric acid production from glyoxylic acid and from oxalic acid via electrochemical synthesis can be a potential process at the industrial scale. In the present case, the oxygen evolution reaction was chosen as the reaction at the other electrode for practical reasons, but oxygen is a low-value product. Another anodic reaction with a more valuable oxidation product can be selected to increase the profitability of the overall electrochemical process and thereby decrease the total production costs of tartaric acid.

The electrochemical production of valeric acid from the renewable bio-based feedstock levulinic acid has the potential to replace the oxo-process, which uses fossil-based feedstock 1-butylene. The electrochemical reduction of the ketone functionality in levulinic acid using lead or mercury cathodes has already been known for over 100 years. However, large-scale electrochemical production of valeric acid might be limited, owing to the toxicity of these materials. In this study, we identified three additional cathode materials, cadmium, indium, and zinc, which selectively and efficiently produce valeric acid. Of these materials, indium and zinc are considered more benign. More specifically, at indium there is no formation of the side product γ-valerolactone, thus resulting in the highest selectivity towards valeric acid. For the electrochemical reduction, a reaction mechanism involving the formation of an organometallic compound is proposed. Furthermore, a possible processing strategy is outlined to enable the continuous electrochemical production of valeric acid on a large scale.