Thermal Decomposition Mechanism of MgCl 2·6H2O

The thermal decomposition mechanism and the intermediate morphology of MgCl2·6H2O before and after calcination by a resistance furnace, were studied using integrated thermal analysis, X-ray diffraction, scanning electron microscope, energy dispersive X-ray spectrum and chemical analysis. The results showed that there were six steps in the thermal decomposition of MgCl2·6H2O, producing MgCl2·4H2O at 69℃, MgCl2·2H2O at 129℃, MgCl2·nH2O(1≤n≤2) and MgOHCl at 167℃, and the MgCl2·nH2O(1≤n≤2) converted to Mg(OH)Cl·0.3H2O with dehydration and hydrolysis simultaneously at 203℃, Mg(OH)Cl·0.3H2O dehydrated to MgOHCl at 235℃, MgOHCl directly converted to MgO at 415℃. The MgOHCl particle was irregular with porous structure, while Mg(OH)Cl·0.3H2O particle had relatively flat surface.