TG-FTIR技术对水氯镁石结晶热解过程的研究

水氯镁石脱水是镁资源利用的关键.其中一种重要的方法是向水氯镁石中添加助剂形成复盐及络合物脱水.通过缓慢冷却水氯镁石及盐酸苯胺的过饱和水溶液制备了水氯镁石-盐酸苯胺结晶物.通过TGDTA-FTIR联用技术分析了盐酸苯胺、水氯镁石以及盐酸苯胺-水氯镁石结晶物的热解过程,定性检测每步分解的逸出气体以推测反应过程.结果显示:盐酸苯胺在400℃以前仅发生物理变化;水氯镁石的热解分阶段进行,205℃以前发生脱去四个结晶水,205℃以后在脱水反应的同时发生水解反应生成HCl;盐酸苯胺-水氯镁石结晶物分阶段脱水、脱盐酸苯胺,整个过程没有水解现象发生,能够得到高纯度无水氯化镁.

TG-FTIR analysis of thermal degradation of bischofite's crystals with aniline hydrochloride

The dehydration of bischofite is the key to the use of magnesium resource. Double salts or complex method is an important way to prepare anhydrous magnesium chloride. The crystals of bischofite and aniline hydrochloride were prepared through lowering the temperature of the mixture's aquatic solution slowly. The pyrolysis of aniline hydrochloride, bischofite and the crystals was qualitatively analyzed by TG-FTIR under 400 degrees C. We infered the reaction process through qualitative detection of escaping gas of each decomposition step. The Experimental results showed that there were three steps in the thermal decomposition of bischofite. In the first step, nearly four crystallized waters decomposed, while hydrolysis and decomposition took place together in the next two steps, but hydrolysis was the main reaction at the lower temperature (205-235 degrees C), and comparative decomposition was the main one at the higher temperature (235-287 degrees C). In the experimental temperature range, aniline hydrochloride didn't decompose. Water and aniline hydrochloride left the crystals at different temperature, and no hydrolysis reaction occurred. Anhydrous magnesium chloride can be prepared though this way.