Chen Baizhen

Preparation of anhydrous magnesium chloride in a gas-solid reaction with ammonium carnallite

Dehydrated ammonium carnallite was synthesized with bischofite from salt lake and ammonium chloride solution in a 1:1 molar ratio of MgCl2:NH4Cl, dehydrated at 160°C for about 4 h. The yield was above 85%. The product was then mixed with solid-state ammonium chloride with a 1:4 mass ratio for the further dehydration at 410°C. The decomposition of NH4Cl made a pressure of NH3 at 30.5 kPa to prevent the hydrolysis of ammonium carnallite. The anhydration of magnesium chloride was achieved at 700°C. The results showed that anhydrous magnesium chloride contains magnesium oxide in an amount that was less than 0.1% by weight. XRD pattern and SEM micrograph showed a good dispersion of ammonium carnallite and anhydrous magnesium chloride crystals with well-distributed big grains, just enough to meet the need for the production of magnesium metal in the electrolysis process.