Membrane Matters in Paired Electrolysis: Synthesis of 2,5-Furandicarboxylic Acid and 2-Butanone

Paired electrolysis combines value-added oxidation and reduction reactions and thus increases electron and process efficiency. This work develops a process to oxidize hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) on the anode and reduce acetoin to 2-butanone on the cathode in a 25 cm2 flow cell. First, we analyze the influence of an ion exchange membrane on the process and assess ion migration. We develop a stable process with a bipolar membrane. We then increase the current density and the reactant concentration. At 150 mA cm–2, we reach a combined yield of above 140% and a product concentration of 1.45 mol2-butanone L–1 and 0.9 molFDCA L–1. The space–time yields are 0.25 μmolFDCA s–1 cm–2 and 0.34 μmol2-butanone s–1 cm–2. We then substitute the potassium-based electrolyte with a more cost-effective sodium-based electrolyte. We counteract the detrimental increase in cell voltage by adding Na2SO4 as a supporting electrolyte without impairing the reaction metrics. With this work, we provide a structured approach for developing paired electrolysis processes, showcased with the biobased products FDCA and 2-butanone toward the efficient electrochemical valorization of biomass.