Electrooxidation of Anhydrous Glycerol: Kinetics and Selectivity

As a by‐product of biofuel production, glycerol needs to find its use in various applications, for example, as a substrate for electrosynthesis of more valuable chemicals. The glycerol oxidation reaction (GOR) in aqueous media is technologically feasible but produces various products with hard‐to‐control selectivity. Less explored is the electrooxidation of anhydrous glycerol, which theoretically limits possible products to aldehydes/ketones, including high‐cost glyceraldehyde. Herein, the GOR with gold electrodes is investigated using glycerol and acetonitrile as solvents without and with base, TEMPO (2,2,6,6‐tetramethylpiperidine 1‐oxyl) redox mediator, and a copper(I)‐bipyridyl catalyst added into the lithium bis(trifluoromethanesulfonyl)imide electrolyte solutions. Both redox‐mediated and heterogeneous oxidation are slow when glycerol is used as a solvent even at 90 °C, as in particular probed by Fourier‐transformed alternating current voltammetry. Redox‐mediated glycerol oxidation to glyceraldehyde is achieved in acetonitrile at a yield rate of 6 ± 3 nmol s −1 cm −2 , but the reaction essentially stops after ≈1 h of electrolysis. Heterogeneous catalytic GOR in acetonitrile is more stable but requires significantly more positive potentials and produces a mix of products. While demonstrating the possibility of selective anhydrous glycerol electrooxidation, our results highlight the need for improvements in the mediator and catalyst designs.