Paired Electrosynthesis Using Bio-Oils: Guaiacol Hydrodeoxygenation Coupled with Glycerol Oxidation in a Stirred Slurry Reactor

Paired electrosynthesis of valuable products at both electrodes improves the economic feasibility and environmental sustainability of electrochemical processes. Here, for the first time, the paired electrocatalytic hydrodeoxygenation of guaiacol (a lignin model compound) at the cathode and the electrooxidation of glycerol (a by-product of biodiesel production) at the anode is reported. Using a stirred slurry electrocatalytic reactor with a Pt/C catalyst and 1 M methanesulfonic acid electrolyte in both chambers, Faradaic efficiencies of 97.4% and 37.4% at the cathode and anode, respectively, were achieved at 66 mA cm^–2 superficial current density and 60 °C. Under the same conditions, the energy consumption of the paired electrosynthesis was 13.9 Wh mol^–1. The guaiacol conversion in the paired cell reached 79%, while the highest glycerol conversion was 40.9%. The selectivity for glyceraldehyde, the most valuable product of glycerol oxidation with a price of approximately $20,000/kg, reached 36.8% at 30 ^oC and decreased with increasing temperature. At the cathode, the highest cyclohexane selectivity in guaiacol hydrodeoxygenation was 6.9%. These results show that further optimization of the reaction conditions and the electrochemical reactor design could potentially lead to the development of a paired electrosynthesis process for the simultaneous conversion of lignin derivatives and glycerol.