The Conversion from Magnesium Hydroxychloride to Anhydrous Magnesium Chloride by Solid-State Reaction

To reduce the content of MgOHCl in anhydrous MgCl2, MgOHCl was converted to anhydrous MgCl2 by solid-state reaction. Factors that affect the conversion effects were investigated, including the mol ratio of NH4Cl to MgOHCl, thickness of covering agent, reaction temperature, and reaction time. The conversion process was characterized by XRD analysis and chemical analysis. The solid-state reaction mechanism was studied and discussed. The MgO content in anhydrous MgCl2 achieved 0.05 pct under the optimal conditions: the mol ratio of NH4Cl to MgOHCl was 3:1, thickness of Al2O3 powder 2 cm, reaction temperature 623 K (350 °C), and reaction time 1 hour.