Selective oxidation of complex, water-insoluble biomass to formic acid using additives as reaction accelerators

Abstract

The oxidation of complex, water-insoluble biomass to formic acid is reported using a Keggin-type polyoxometalate (H₅PV₂Mo₁₀O₄₀) as the homogeneous catalyst, oxygen as the oxidant, water as the solvent and p-toluenesulfonic acid as the best additive. The reaction proceeds at 90 °C and 30 bar O₂ and transforms feedstock like wood, waste paper, or even cyanobacteria to formic acid and CO₂ as the sole products. The reaction obtains up to 53% yield in formic acid for xylan as the feedstock within 24 h. Besides the role of the additive as a reaction promoter, the formic acid isolation and the recycling of catalyst and additive are demonstrated.