Electrochemical conversion of lignin to useful chemicals

Electrochemical conversion of waste lignin from pulping mills and biorefineries is an alternative renewable process for generating industrial chemicals that may afford better control over conversion than other catalytic or thermochemical processes because the electrode potential, and hence the reaction energetics, can be controlled. The authors report here electrochemical oxidation of lignin on a Co core/Pt partial shell nanoparticle alloy electrocatalyst, identify several oxidation products, and quantify oxidation product concentration as a function of oxidation time. Key results show that useful chemicals like heptane and apocynin are generated during the electrochemical oxidation of lignin. Some key oxidation product concentrations increase steadily over time, suggesting they are likely stable products that do not participate in other reactions. Concentrations of other oxidation products increase and then decrease with time, suggesting that they may participate in proceeding chemical or electrochemical reactions. Formation of other oxidation products like 1,3-bis(1,1-dimethylethyl)-benzene and 1,4-di-tert-butylphenol suggest oxidative decomposition initiated by hydroxyl radicals that are likely generated at the anode. Overall, the results suggest that electrochemical oxidation of lignin is complex, with possibly many competing homogeneous chemical and heterogeneous electrochemical reactions.