Dehydration/Hydration Behavior of Layered Double Hydroxide for Chemical Heat Storage

Dehydration and rehydration behavior of a layered double hydroxide (LDH), Mg2Al(OH)6.2Cl0.8·nH2O, was investigated. The dehydration proceeds in two steps; at first interlayer water is released from 50 °C, then dehydration condensation of hydroxyl groups starts from 300 °C. Interlayer anion Cl− is also desorbed as HCl during the second dehydration. The mole fraction of water removed by dehydration before the HCl desorption was estimated by thermogravimetric analysis; 1.85 mol-H2O/mol-LDH. The dehydrated material, without HCl loss, was quantitatively hydrated by refluxing in water for 480 min.