Production of formic acid from biomass-based compounds using a filter press type electrolyzer

There has been a growing interest for the sustainable production of formic acid (FA) in recent years considering its potential use as a hydrogen storage compound. In this context, the electrochemical transformation of carbohydrate-based biomass into formic acid in aqueous media was investigated using a filter-press type electrochemical cell. Therefore the oxidation of mono and disaccharides was carried out at NiOOH, RuO2/Ti (DSA) and PbO2 anodes, in FM01-LC (ICI) electrolyzer. The effect of carbon number of biomass compound, anode material and pH on product distribution was determined. Between the readily available carbohydrates studied in this work at NiOOH anode, in alkaline medium, d-xylose provides the highest selectivity towards formate anion, i.e. 42%. The transformation of d-glucose into formic acid, with 38% selectivity, was achieved at RuO2/Ti (DSA) in 0.5 M NaOH medium, applying a current density of 80 A m−2. The production of formate anion is mostly accompanied by the formation of oxalate anion and carbonates which constitute the by-products of the reaction. Considering that after acidification of carbonates the resulting CO2 can be easily removed and trapped by the growing plants which provide new biomass-based material, the transformation of oxalate anion (OA) into CO32− is of major importance. For this reason the oxidation of OA at DSA in 0.1 M NaOH medium was also studied. In these conditions 60% of the initial oxalate anion was transformed to CO32− at 2.5 V vs. SCE.