Valorization of Glycerol Through 2,2,6,6‐Tetramethyl‐1‐Piperidine‐N‐Oxyl (TEMPO)‐Catalyzed Electrochemical Oxidation with High C3 Product Selectivity: Impact of Stirred Bulk Versus Flow Electrolysis

Conversion of glycerol to value‐added products is an attractive solution to the oversupply of this byproduct of biofuel production. The glycerol oxidation reaction (GOR) may form product mixtures derived from the scission of the three‐carbon (C3) glycerol backbone, generating one‐ (C1) or two‐carbon (C2) species. Here, the bulk and flow electrolysis (FE) of the 2,2,6,6‐tetramethyl‐1‐piperidine‐N‐oxyl (TEMPO)‐mediated GOR reaction is explored to produce a valorized C3 product, highlighting key selectivity differences between the two methods despite using the same optimized electrolyte composition. Increasing the pH of the solution dramatically increases GOR activity but presents a tradeoff with the stability of TEMPO. At an optimal pH of 10.6 in carbonate buffer in a batch reactor, the reaction proceeds with higher than 90% yield via a 10‐electron oxidation to mesoxalic acid, a C3 product. FE at much lower Reynolds number yields significantly lower selectivity toward C3, demonstrating a high sensitivity to mass transport. The work sheds light on the opportunities toward selectively producing C3 products from GOR as well as the importance of mass transfer considerations for the valorization of this key bio‐feedstock and for others involving mediated electrocatalysis.