Catalytic Transformation of Lignocellulosic Biomass into Arenes, 5-Hydroxymethylfurfural, and Furfural

The complete transformation of lignocellulosic biomass into valuable platform chemicals is of great significance. Herein, a catalytic process for the upgrading of lignocellulose to arenes, 5-hydroxymethylfurfural (HMF), and furfural is reported. Firstly, the lignin fraction in lignocellulosic biomass is selectively converted into lignin oil (82.9 mol % yield of lignin monomers from birch wood) over a Pd/C catalyst and then further hydrodeoxygenated to arenes in catalytic hydrogen-transfer reactions over a Ru/Nb₂ O₅ catalyst. High yields of C₇ -C₉ hydrocarbons (95.6 mol %) with 85.6 wt % selectivity to arenes based on lignin oil are achieved owing to the synergistic effect between Ru and Nb₂ O₅ , which enables direct hydrogenolysis of the C_aromatic -OH bond in phenolics. Secondly, the cellulose and hemicellulose fractions in the Pd/C-containing solid residue, as well as methylated C₅ sugars produced during the stripping of lignin, are converted into HMF and furfural with a total yield of up to 24.5 wt % (based on the amount of birch wood) in a THF/concentrated seawater (ca. 30 wt % salts) biphasic reaction system. Here, seawater played a key role in the conversion of cellulose and hemicellulose into HMF and furfural, respectively; more importantly, it made the separation and reuse of the Pd/C catalyst easier. With this catalytic process, the complete and efficient transformation of lignocellulose into highly value-added products with recycling of each catalyst and solvent has been realized.