Design-of-Experiments-Based Optimisation of Vanillin Yield from Kraft Lignin Using Pulse Electrolysis and Thermolysis

Abstract

The electrification of the production of fine chemicals has received increased interest in combating petrochemical routes with a high carbon footprint. Oxidising biomass from waste streams with concomitant hydrogen production, such as the transformation of lignin to vanillin, would be a great asset. Here, we show the combination of activity screening using a scanning droplet cell on a thin-film Ni−Fe library and performance testing in a flow-through cell with pulse electrolysis. The identified optimal Ni−Fe material composition was prepared on Ni foam with a polymer/metal precursor spray method. Full factorial and Doehlert matrix designs were employed to better comprehend each parameter‘s effects on the complex system. The best conditions for the electrooxidation of Kraft lignin at room temperature were at E1st=1.36 V vs RHE, t1st=1 s for the first pulse and E2nd=1.60 V vs RHE and t2nd=15 s for the second pulse, leading to the significantly improved production of 2.15 μmols of vanillin at room temperature. Pulsed chronopotentiometry was demonstrated to be a cost-effective and robust technique with a simple setup for the valorisation of Kraft lignin. Combined with a subsequent thermolysis step, 8.05 μmols of vanillin were obtained.