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 (82.9mol% 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/Nb2O5 catalyst. High yields of C-7-C-9 hydrocarbons (95.6mol%) with 85.6wt% selectivity to arenes based on lignin oil are achieved owing to the synergistic effect between Ru and Nb2O5, 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 C-5 sugars produced during the stripping of lignin, are converted into HMF and furfural with a total yield of up to 24.5wt% (based on the amount of birch wood) in a THF/concentrated seawater (ca.30wt% 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.