MECHANISM AND KINETICS OF CELLOBIOSE DECOMPOSITION IN SUBRITICAL AND SUPERCRITICAL WATER

Cellobiose decomposition kinetics and products in sub-and supercritica l water were studied with a flow apparatus at temperatures from 300 to 400 degrees C at pressures from 25 to 40 MPa, and at short residence times (0.04-2 s). Cellobiose was found to decompose via hydrolysis of the glycosidic bond and via pyrolysis of the reducing end. Pyrolysis p roducts were glycosylerythrose (GE) and glycosylglycolaldehyde (GG) wh ich were confirmed by FAB-MS. Hydrolysis products were glucose, erythr ose, and glycolaldehyde from cellobiose, GE, and GG, respectively, as well as glucose decomposition products. The kinetics from glucose deco mposition were used to fit the experimental results and evaluate rate constants of hydrolysis (k(H)) and pyrolysis rate constants (k(1) and k(2)) The activation energy for the hydrolysis of cellobiose and pyrol ysis products GG and GE was found to be 108.6, 110.5, and 106.1 kJ/mol , respectively. In the supercritical region, there was a decrease in t he pyrolysis rates k(1) and k(2) and a corresponding increase in hydro lysis selectivity from 85% to 95% as the pressure increased from 30 to 40 MPa.