Kinetics of sorbitol decomposition under hydrothermal condition

Abstract

Sorbitol is widely used in food industries, and its decomposition behavior under hydrothermal condition is needed for its recovery from biomass and processing. In order to elucidate the decomposition behavior of sorbitol under hydrothermal conditions, hydrothermal decomposition of sorbitol was investigated in a flow reactor between 170°C and 250°C at 25 MPa. The decomposition was well expressed using a first-order reaction rate, and the rate constant followed the Arrhenius law. The pre-exponential factor and the activation energy were also determined. Compared with the decomposition of the sorbitol isomer mannitol, sorbitol was decomposed more rapidly, likely due to the variation in water molecule accessibility owing to different isomeric configurations. In addition, although activation energies were comparable for both mannitol and sorbitol (29.1 kJ mol-1 and 28.3 kJ mol-1, respectively), the pre-exponential factor of mannitol (6.19 s-1) was an order of magnitude lower than that of sorbitol (42.9 s-1).