Physico-geometrical Kinetic Aspects of the Thermal Dehydration of Trehalose Dihydrate

When linearly heating trehalose dihydrate (TH-DH) at a relatively high heating rate (β ≥ 1.5 K min–1), the thermal dehydration begins in the solid state and transitions to the liquid state at the melting point of TH-DH (∼370 K). The complex mass loss and phase change characteristics observed during the thermal dehydration is due to the contributory effects of various physical phenomena, including melting of TH-DH and anhydride products. The reactions entirely occurred in the solid state under isothermal and nonisothermal conditions at a low heating rate (β ≤ 1.0 K min–1), and its kinetics were described by the physico-geometrical consecutive process comprising the surface reaction and subsequent phase boundary-controlled reaction. The reactions initiated at approximately the melting point of TH-DH under a significantly high atmospheric water vapor pressure and proceeded mostly in the liquid state exhibiting a single-step mass loss behavior. The thermal dehydration accompanied by liquefaction demonstrated an autocatalytic kinetic behavior, which was regulated by the evaporation of the water vapor from the surface of viscous liquid particles. The kinetic findings for the reactions in the solid and liquid states allow the physico-geometrical interpretation for the complex mass loss and phase change behaviors during heating TH-DH at relatively high β values.