Determination of Mannitol Decomposition Rate under Hydrothermal Pretreatment Condition

Abstract

For utilization of kelp, which is produced abundantly in Japan, recovery of mannitol is important because mannitol is a main component of kelp. Mannitol can be recovered into liquid phase by hydrothermal pretreatment of kelp, but when treatment condition is too severe, decomposition of the product mannitol also takes place. To determine the optimum condition for hydrothermal pretreatment, determination of mannitol decomposition rate is indispensable. The purpose of this study is to determine decomposition rate parameters of mannitol under hydrothermal conditions for mannitol recovery from kelp without concomitant decomposition. The decomposition rate was successfully determined using a flow reactor, and the rate constant was expressed with a first-order Arrhenius rate equation with a pre-exponential factor of 3.23 s⁻¹ and activation energy of 26.5 kJ/mol. The obtained reaction rate predicted the behavior of mannitol during hydrothermal pretreatment of kelp with average error of 4.6 %.