铵光卤石氨法无水氯化镁的制备与表征

Preparation and characterization of anhydrous magnesium chloride by reaction of ammonia and ammonium carnallite

为制备用于电解炼镁的原料无水氯化镁,用盐湖水氯镁石和氯化铵溶液为原料在一定条件下合成铵光卤石,铵光卤石在热空气中脱水成低水铵光卤石,低水铵光卤石与氨在一定的温度下脱水为氨合铵光卤石,氨合铵光卤石热分解成无水氯化镁。分析结果表明:制得的无水氯化镁中氧化镁的含量约为0.1%。综合热分析显示:铵光卤石的脱水温度以160℃为宜,氨合铵光卤石的热分解温度>580℃,X射线衍射说明氨合铵光卤石为一混合物,制得的无水氯化镁中无杂相,电镜扫描图表明氨合铵光卤石分散性好,无水氯化镁的颗粒大而均匀。

Anhydrous magnesium chloride was prepared for electrolytically producing magnesium metal, ammonium carnallite was synthesized by a process in which hydrated magnesium chloride in salt lake and ammonium chloride solution, dehydrated to some extent by heating, dehydrated ammonium carnallite and ammonia reacted at a temperature, preparing ammoniation ammonium carnallite, decomposing it into anhydrous magnesium chloride at high temperature. The analytical result show that anhydrous magnesium chloride contains magnesium oxide in an amount about 0.1% by weight. TG-DTA curves show that ammonium carnallite is pretreated to remove some of water by known thermal processes at 160°C, ammoniation ammonium carnallite crystals are calcined to anhydrous magnesium chloride at a temperature greater than 580°C. XRD pattern demonstrated that ammoniation ammonium carnallite are mixture, anhydrous magnesium chloride processes high purity. SEM micrograph demonstrated ammoniation ammonium carnallite crystals of good dispersion could be obtained, the grains of anhydrous magnesium chloride are big and well-distributed.