Kinetic study of the thermal conversion of ginsenosides using lumped groups in steaming, hydrothermal reactions, and CO2-assisted hydrothermal reactions

Abstract

Kinetic study of the thermal conversion of ginsenosides was carried out in steaming, hydrothermal reactions, and CO2-assisted hydrothermal reactions. Since these are complex reactions involving various ginsenosides, the components are divided into three lumped groups according to their structure. Meanwhile, the conventional series reaction model cannot explain the rapid increase of the final product over that of the intermediate. Therefore, a new model was proposed with a parallel reaction pathway that converts directly from the reactant to the final product. The pathway corresponded to E1 elimination that occurs competitively during deglycosylation by the SN1 mechanism. Consequently, the suggested model was able to explain the rapid increase of the final product and produced more accurate predictions. According to Arrhenius analysis, activation energy decreased in the order of steaming, hydrothermal reactions, and CO2-assisted hydrothermal reactions, which was due to the high ion product of subcritical water and in-situ generation of carbonic acid.