Electrochemical Oxidation of Alcohols Using Nickel Oxide Hydroxide as Heterogeneous Electrocatalyst in Batch and Continuous Flow

An electrochemical method has been developed for a mediated oxidation of primary alcohols to carboxylic acids. The method is compatible with a variety of alcohols bearing nitrogen-containing heterocycles in undivided batch and flow modes. The use of a heterogeneous NiOOH electron–proton transfer mediator avoids the need for homogeneous catalysts that contribute to more unit operations during downstream purging and increased process mass intensity. To demonstrate the applicability of this method for continuous processing, a single-pass flow electrochemical oxidation of nicotinyl alcohol to nicotinic acid is demonstrated with a 77% isolated yield. The NiOOH-coated anodes show no reduction in catalysis efficiency over 12 h, and minimal Ni metal leaching (22.3 μg per liter) is observed.