Electrolysis for Valorization of Industrially-Sourced Crude Glycerol

Valorization of waste (crude) glycerol could enhance sustainability of chemical manufacturing and the economics of biodiesel production. Crude glycerol is of low value, and is typically a mixture of glycerol, methanol, water, sodium hydroxide, and residual impurities. This study disentangles the influences of methanol and triglyceride impurities on the electrolytic oxidation of industrially sourced waste glycerol. Data from industrial biodiesel producers uncovered two predominant waste glycerol formulations: methanol-rich and methanol-lean. Electrolysis using synthetic equivalents of these formulations over a nickel catalyst in a flow electrolyzer revealed that performance losses of up to 90% can be avoided in the presence of ≥0.5 M methanol. At lower concentrations of methanol, use of a dynamic reactor operation protocol mitigated performance losses. The combination of these results enabled stable multihour electrolytic production of the valuable chemical formate from industrially sourced waste glycerol. These findings provide guidance toward feasible operating conditions and process parameters for the further development of crude glycerol electrolysis in industrial practice.