乙二醇氨法制备高纯无水氯化镁工艺研究

Technology of Preparing High-Purity Anhydrous Magnesium Chloride by Glycol-Ammonia Method

无水氯化镁是电解金属镁的原料也是众多催化剂和医药的中间体。研究以水合氯化镁与高沸点溶剂共沸蒸馏为基础,通过一系列过程制备出含纯99%以上无水氯化镁。过程包括:(1)配置水合氯化镁的醇溶液,(2)采用常压或负压蒸馏脱水,(3)采用不同方法对无水氯化镁醇溶液氨化,再经真空过滤、氨饱和甲醇洗涤,得到六氨氯化镁结晶,(4)经120℃烘干,蒸掉结晶中的甲醇得到六氨氯化镁,(5)经450℃煅烧得到无水氯化镁。通过对全流程的工艺条件的探索,探明了过程控制因素和影响规律。用XRD对六氨氯化镁的分析表明,氨化过程在氨浓度较低情况下,有副反应MgC l2+glycol+2NH3→Mg-glycol+2NH4C l↓发生,NH4C l夹带在六氨氯化镁中,而镁的醇盐则是无水氯化镁中MgO的主要来源,在较低温度和氨高度过量的环境中该反应可以得到有效抑制。

Anhydrous magnesium chloride is the material of electroly metal magnesium and the important intermediate of catalyzer and medicine. Based on hydrous magnesium chloride azeotroped and distilled with high boiling point solvents, the high - purity anhydrous magnesium chloride whose purity is more than 99% is prepared by a series of processes which were obtained as follows： （ 1 ） dissolve the hydrated magnesium chloride in ethylene glycol, （2） dehydrate the mixture in distillation at normal or negative pressure, （ 3 ） aminate the MgC12 - glycol solution to prepare the hexammoniate magnesium chloride , filtrate and wash the hexammoniate magnesium chloride with ammonia saturated methanol, （4） dry the crystals in oven where methanol is evaporated at 120℃, （5） calcine the crystals to obtain the anhydrous magnesium chloride at 450℃. We obtained controlled process factors and influential laws by analyzing the conditions of technology. The XRD data of the intermediate product （hexatnmoniate magnesium chloride） shows that the NH4Cl is the significant impurity of MgCl2·6NHs. therefore we conclude that the MgO which occurs in anhydrous magnesium mainly caused by the Mgglycol salt which produced by the co -reaction MgC l2＋glycol＋2NH3→Mg-glycol＋2NH4C l↓ in the aminating process. Fortunately this co - reaction can be bated in lower temperature and high superfluous of NH3.