Catalytic Valorization of Native Biomass in a Deep Eutectic Solvent: A Systematic Approach toward High-Yielding Reactions of Polysaccharides

This work investigates catalytic reactions of raw, bulk, native biomass (poly)carbohydrates in the choline chloride/oxalic acid deep eutectic solvent. In particular, we systematically explore the reactivity of native glucans, fructans, and xylans in model transformations of refined substrates and unrefined cellulosic materials in the catalyst-solvent. We show that alpha-linked glucose polymers, fructans, and xylans are all amenable to hydrolytic processing, and only the linear polysaccharide cellulose remains rather intractable under our conditions. Improved fundamental understanding of the chemistry permits tuning the reaction parameters toward high yielding conversion of undervalued terrestrial and marine biomass into significantly value-added glucose (yield up to 68 wt %), fructose (yield up to 60 wt %), xylose (yield up to 73 wt %), 5-(hydroxymethyl)furfural (yield up to 14 mol %), or furfural (yield up to 72 mol %). Under these optimized conditions, cellulose remains as an unreacted portion, which could be recovered and very effectively beneficiated, delivering additional useful chemicals in high yields from the biomass and optimizing toward total use of the biomass. We realize efficient conversions of polysaccharides of the biomass into high yields of useful small molecules.