Selective Oxidation of Ethanol on a Nickel Foam Electrode Followed by Aldol Condensation with Furfural: An Electrochemical Approach for the Utilization of Biomass-Derived Molecules

An electrochemical method was developed to achieve the oxidative aldol condensation of ethanol with biomass-derived furfural under ambient conditions. The product distribution was composed of 3-(2-furyl)acrolein (F2A) as the major product and 5-(2-furanyl)-2,4-pentadienal (F24P) as the minor product, resulting from the cross aldol condensation of F2A with a second acetaldehyde molecule. The latter reaction step was successfully eliminated to achieve a single product, 3-(2-furanyl)-2-methyl-2-propenal (F22P), by simply substituting ethanol with 1-propanol. Over 90% Faradaic efficiency for the electrochemical step was achieved in 0.5 M KOH and 50% aqueous ethanol at a nickel foam anode. In addition, the same anode and cathode electrodes can be used up to four times without compromising the efficiency of the overall process, thus highlighting nickel foam as an inexpensive and robust anode material for ethanol to acetaldehyde oxidation.