Kinetic studies on the loss of water from α- d-glucose monohydrate

Abstract

Although the dehydration of α- d-glucose monohydrate is an important aspect of several industrial processes, there is uncertainty with regard to the applicable rate law and other factors that affect dehydration. Therefore, the dehydration of three glucose monohydrate samples has been studied using isothermal gravimetric analysis. Dehydration follows a one-dimensional contraction (R1) rate law for the majority of kinetic runs, and an activation energy of 65.0 ± 3.9 kJ mol −1 results when the rate constants are fitted to the Arrhenius equation. Fitting the rate constants to the Eyring equation results in values of 62.1 ± 3.7 kJ mol −1 and −77.8 ± 4.7 J mol −1 K −1 for Δ H ‡ and Δ S ‡, respectively. The impedance effect on the loss of water vapor has also been investigated to determine the values for activation energy, enthalpy, and entropy for diffusion of water. The results obtained for the activation parameters are interpreted in terms of the absolute entropies of anhydrous glucose and the monohydrate.