Hydrolysis kinetics and mechanism of chitin in subcritical water

Abstract The hydrolysis kinetics of chitin was investigated at 280–366 °C in this study. The chitin began to be hydrolyzed at 283 °C and the lowest yield of chitin residue was obtained at 362 °C. The entire hydrolysis process of chitin was separated into three zones, which could be expressed by Coats-Redfern models. First-order model was the most effective for describing the hydrolysis kinetics of chitin, yielding activation energies of 215.4 kJ mol −1 in zone 1, 153.7 kJ mol −1 in zone 2 and 297.4 kJ mol −1 in zone 3, respectively. The crystalline region and hydrogen bond in chitin could be effectively broken down by subcritical water treatment. The hydrolysis of chitin at 280–366 °C was composed of the hydrolysis of chitin at the surface and the destruction of hydrogen and glycosidic bonds in the interior of the chitin.