抄録
Supercritical water is the water at fluid phase when temperature and pressure are above its critical values (374 ℃, 22.1 MPa). At this state, water has high potential as a solvent for organic components and gases. As a result, biomass could be homogeneously dissolved in supercritical water and consequently obtain high conversion. This study attempted to investigate the kinetics mechanism of xylose as a model compound of hemicellulose in wide range of temperature. The experiment was carried out at temperature of 350-450 ℃ and pressure of 25 MPa using a continuous reactor. Liquid intermediate was found to be products from isomerization of xylose, dehydration and retro-aldol condensation. Reaction network was proposed and kinetic parameters of each reaction were calculated based on data fitting assuming the first order for all reactions. Finally, the effect of temperature was used to classify the reactions into radical reaction, which shows Arrhenius behavior, and ionic reaction, which shows non-Arrhenius behavior in supercritical region.
