Volume 49 (2016) Issue 7 Pages 663-667
The present study determines the kinetics for decomposition of mannose, its corresponding uronic acid (mannuronic acid (MA)), and sugar alcohol (mannitol) under hydrothermal condition. The experimental work was conducted using a continuous-flow-reactor at temperatures ranging from 170 to 250°C, and with residence time between 3 and 15 s. The operating pressure was fixed at 25 MPa throughout the experiment. The remaining amount of all compounds decreased as the temperature increased. The decomposition reaction followed first order kinetics at shorter residence times. The decomposition rate increased in the order of MA<mannitol<mannose with similar activation energies of 28.3, 29.1 and 44.6 kJ/mol, respectively. However, the pre-exponential factors were 282, 6.19, and 9,600 s−1 for Ma, mannitol, and mannose, respectively, indicating that uronic acid is twice as easily decomposed, while sugar alcohol is less reactive than mannose by two orders of magnitude for the temperature range studied here.