Chemical valorisation of biomass derived furanics and carboxylic acids over niobium-based catalysts

Furfural is an industrial renewable platform chemical, which can be converted to useful furanics such as α-angelica lactone, carboxylic acids such as levulinic acid and valeric acid, or to higher carbon content products via condensation routes for producing drop-in fuel replacements and chemicals with diverse applications. These important conversion processes may be carried out in selective fashions, although they require adequate catalysts. They were successfully carried out using versatile, stable silica-wrapped niobium oxide nanostructured catalysts. For example, α-angelica lactone was converted in an integrated fashion to ethyl levulinate in 90% yield, and the esterification of levulinic and valeric acids gave ethyl levulinate in quantitative yield and ethyl valerate in 90% yield, respectively, at 140 °C. Catalytic, mechanistic and kinetic modelling studies shed light on the influence of the materials properties on the catalytic performances. These catalysts outperformed pure Nb 2 O 5 , as well as hydrothermally synthesized composites consisting of Nb 2 O 5 nanoparticles embedded in a mesoporous siliceous matrix. Reaction and substrate scopes may be considerably broadened in the context of the chemical valorisation of biomass, using stable solid acid catalysts consisting of nanostructured silica-niobia which outperformed pure niobia and other catalysts.