Direct Valorization of Lignocellulosic Biomass into Value-Added Chemicals by Polyoxometalate Catalyzed Oxidation under Mild Conditions

Efficient methodologies for converting sustainable lignocellulosic biomass to high-value chemicals are important for the utilization of biomass. Although many conversion methods have been proposed, those that are commonly used require harsh operating conditions. Polyoxometalate (POM) can be used either as a direct oxidation agent or as a catalyst to depolymerize technical lignin, but the lignin oil yield for this process is relatively low. Instead of using technical lignin, in this study we used an oxidation approach to directly convert native lignocellulose in a methanol/water mixture using polyoxometalate (H₃PMo₁₂O₄₀) as a catalyst to produce high-value chemicals. 80% of lignin in the hardwood was depolymerized to low molecular weight lignin oil (376 Da) at 150 °C and 1 MPa O₂ in 2 h. The lignin oil yielded 38.0% aromatic monomers, based on total lignin mass. Simultaneously, only 9.2% residual solids remained; 83.7% of the hemicellulose in the hardwood was converted to water-soluble carbohydrates.