氨络合法制备无水氯化镁工艺

Investigation on Preparation of Anhydrous Magnesium Chloride by Ammonia Complexation Method

采用氨络合法,以菱镁矿为原料制备出了高纯无水MgCl2,研究了温度、反应时间、初始浓度对制备工艺关键步骤的影响.结果表明,菱镁矿粉在750℃下煅烧2h生成高活性MgO;活性MgO与NH4Cl在乙二醇中氯化反应的最佳温度应控制在130～150℃,该反应的表观活化能为40.7kJ/mol;MgCl2·6NH3的最佳反应结晶温度约为15℃,MgCl2·6NH3晶体是白色正八面体,初始浓度、温度等显著影响晶体质量;MgCl2·6NH3的热解过程可分为55～97,97～182和182～297℃三个阶段,每个阶段脱去2个氨分子.

High-purity anhydrous magnesium chloride was prepared from magnesite by ammonia complexation method. By examination of temperature,reaction time,initial concentration on the key steps of this preparation process,the following results were obtained：（1） Magnesite would be calcined into highly active magnesia at 750℃ for 2 h. （2） The optimal temperature of chlorination of active magnesia was between 130 and 150℃,and the apparent activity energy of this chlorination reaction 40.7 kJ/mol. （3） Initial concentration and temperature had remarkable effects on crystal-size distribution of magnesium chloride hexammoniate,and the optimal reaction crystallization temperature was about 15℃. In addition,magnesium chloride hexammoniate was white octahedral crystals. （4） The thermal decomposition process could be divided into three steps of 55～97,97～182,182～297℃ according to its TG curves,and 2 ammonia molecules of one magnesium chloride hexammoniate were released in each step.