(720g) Nitrogen Behavior in Glycine Decomposition Under Hydrothermal Condition

Nitrogen recovery from biomass feedstock is useful in terms of biorefinery to obtain fertilizer component together with energy in hydrothermal conversion of biomass. However, actual biomass contains various forms of nitrogen, and its behavior is not easy to understand. Thus, in this study, glycine, the simplest amino acid, was employed as model compound, and behavior of nitrogen was studied. We used a laboratory scale continuous reactor, and glycine aqueous solution was delivered together with preheated hot compressed water. Mixing of these two flows at the entrance of the reactor enabled rapid heating of the feedstock to the reaction temperature. At the exit of the reactor, the reactor effluent was mixed with cooling water to achieve rapid cooling. In this way, precise reaction time was determined. We further minimized the dead space of the reactor. The effluent was collected and analyzed for nitrogen products, which were mainly ammonia and methylamine. This is the first result of measuring the reaction characteristics with sufficient accuracy in supercritical water. One of the interesting discussion is whether the reaction rate and selectivity are different between subcritical and supercritical condition. If they are the same, they may be considered as radical reaction, while if not, they may be considered as ionic reaction. Comparison of our result with previous study by Sato, conducted under subcritical conditions, the reaction was found to be radical reaction. The finding of this study provides important information for nitrogen recovery from biomass feedstock using hydrothermal conditions.