Amorphization and Semi-Dry Conversion of Crystalline Cellulose to Oligosaccharides by Impregnated Phosphoric Acid

Abstract Efficient conversion of crystalline cellulose to useful chemicals is a grand challenge in biorefining. In this work, we report that amorphization and semi-dry conversion of crystalline cellulose to oligosaccharides is achieved by impregnated H3PO4. Specifically, the impregnation of crystalline cellulose with H3PO4 under 5 MPa of He and subsequent drying at room temperature produces amorphous cellulose. The impregnated H3PO4 likely permeates bulk phase cellulose by dissociating the hydrogen bonding network of cellulose during the treatment. The resulting swollen solid is depolymerized to oligosaccharides in 40% yield with 72% selectivity by heat-treatment at 100 °C with no solvent. The analysis of obtained oligosaccharides using nuclear magnetic resonance and mass spectroscopy reveals that the products are oligomers of glucose linked by various kinds of glycosidic bonds that may be useful as prebiotics.