(779f) Overall View of Lignocellulosic Biomass Decomposition in Supercritical Water

Supercritical water gasification is a promising technology for gasifying wet biomass. However, detail reaction kinetics of each component, cellulose, hemicellulose, and lignin have not been elucidated, and the interaction between the components has to be elucidated. In this study, mixture of cellulose, hemicellulose, and/or lignin was delivered into a continous reactor for supercritical water gasification and its reaction characteristics were determined. Reaction temperature was changed around critical point of water so that both subcritical and supercritical conditions were considered while the reaction pressure was kept at 25 MPa. Intermediate compounds were analyzed by HPLC, and comparison between avaraged single copound result and mixture was made. The interaction was clearly observed, especially in terms of hydrogen consumption. Reaction network was develped, and reaction rate constants were deteremined for each of the reaction by least square method to fit the experimental data with the calculation by the model. The Arrhenisc plot for these reactions classified ionic reaction and radical reaction. For the case of radical reacitons, Arrhenius plot showed a straight line as usual, but for the case of ionic reactions, reaction rate kinetics deviated from the straight line at high temperature, indicating ions get unstable under supercritical condition. The overall reaction kinetics was also determined, and discussed.