Cellulose dissolution in near- and supercritical water for cello-oligosaccharides production

Abstract

Water-soluble cello-oligosaccharides and water-insoluble, low molecular weight cellulose polymers can be produced by controlled cellulose depolymerization of cellulose using supercritical water treatment. The products from the hydrolysis and dissolution of microcrystalline cellulose were investigated after a treatment at temperature range of 320 to 390 degrees Celsius and residence time range of 0.1 to 0.8 seconds. Four cellulosic product fractions were identified, quantified, and characterized using gravimetric and chromatographic techniques. The four fractions consisted of solid cellulosic residue, solid cellulosic precipitate, water-soluble cello-oligosaccharides, and water-soluble degradation products. The water-insoluble, low molecular mass cellulose polymers accounted for up to 25 percent of the total products. In addition, glucose and cello-oligosaccharides of degree of polymerization up to cellodecaose accounted for up to 65 percent of the total products. Furthermore, the water-soluble fraction was significantly purified using membrane ultrafiltration. These results show that the supercritical water treatment of microcrystalline cellulose is a fast and efficient method for producing both cello-oligomers and low molecular weight cellulose precipitate, which can be integrated into a full manufacturing process using downstream separation and purification methods.