Effect of LiOH Addition on Dehydration Reaction of Mg(OH)2


R. Kurosawa and J. Ryu, J. Chem. Eng. Jpn., 52, 152-158 (2019).

The dehydration behavior of LiOH-modified Mg(OH)2 (LiOH/Mg(OH)2), as a new chemical heat storage material, was investigated. Structural analysis of LiOH/Mg(OH)2 was carried out using an X-ray diffraction (XRD) meter. The profile of the dehydration reaction of LiOH/Mg(OH)2 was observed to analyze the dehydration kinetics of the LiOH/Mg(OH)2 samples. The XRD patterns of the LiOH/Mg(OH)2 samples shifted toward higher angles than that of Mg(OH)2. This indicated that the lattice parameter might have changed and lattice defects such as oxygen vacancies might have been generated on the surface of Mg(OH)2. The rate of the dehydration reaction increased as the amount of added LiOH increased; therefore, LiOH/Mg(OH)2 could be a potential chemical heat storage material. We concluded that LO20 (Mg(OH)2 containing 20 mol% LiOH) was the combination with the most optical mixing mole ratio. This result was determined by analyzing the dehydration activation energy values. When the dehydration reactions of the LiOH/Mg(OH)2 samples were considered to be first-order reactions, the calculated mole fraction of Mg(OH)2 could not be reproduced. However, the calculated mole fractions of Mg(OH)2 were in agreement with those measured considering the reactions to be zero- and first-order reactions. Therefore, the kinetics of the dehydration reaction of the LiOH/Mg(OH)2 samples included both zero- and first-order reactions.