热分析法研究六水硝酸镁的脱水过程与机理  

Dehydration Process and Mechanism of Magnesium Nitrate Hexahydrate Using Thermal Analysis Technique

作　　者：钟远 王敏[2,3] 袁俊生[1] ZHONG Yuan;WANG Min;YUAN Junsheng(School of Chemical Engineering and Technology,Hebei University of Technology,Tianjin 300130,China;Key Laboratory of Comprehensive and Highly Efficient Utilization of Salt Lake Resources,Qinghai Institute of Salt Lakes,Chinese Academy of Sciences,Xining 810008,China;Key Laboratory of Salt Lake Resources Chemistry of Qinghai Province,Xining 810008,China)

机构地区：[1]河北工业大学化工学院,天津300130 [2]中国科学院青海盐湖研究所,中国科学院盐湖资源综合高效利用重点实验室,西宁810008 [3]青海省盐湖资源化学重点实验室,西宁810008

出　　处：《材料导报》2020年第22期22015-22019,共5页Materials Reports

基　　金：国家自然科学基金(U1707603);青海省重大科技专项项目(2017-GX-A3)。

摘　　要：硝酸镁基熔盐作为中温储能材料在太阳能热发电领域具有广阔的应用前景,因此开展六水硝酸镁脱水过程与机理研究对无水硝酸镁的制备具有重要意义。本工作通过脱水反应热力学函数计算、同步TG/DSC热分析测试以及脱水产物表征分析系统研究了其脱水过程和机理。热分析实验中选择升温速率1℃/min使脱水反应在接近平衡态下进行。结果表明,标准状态下当温度高于168.02℃时,六水硝酸镁脱水为无水硝酸镁。在程序升温过程中,六水硝酸镁先熔融为液体,随着水分的蒸发结晶析出二水硝酸镁,遵循相平衡规律。二水硝酸镁在130℃时熔融,熔体直接脱水为无水硝酸镁,是液固非均相反应,脱水速率低,需要较高温度才能完全脱水,具有热力学自发性。Magnesium nitrate-based molten salt has a wide application prospect as a medium temperature energy storage material forsolar thermal po-wer generation.The research on the dehydration process and mechanism of magnesium nitrate hexahydrate is of guiding significance for the preparation of magnesium nitrate.The dehydration process and mechanism of magnesium nitrate hexahydrate were studied in this work through simultaneously TG/DSC.The thermodynamic functions of dehydration reaction of magnesium nitrate hexahydrate were calculated.The dehydration products were characterized by XRD,Raman and DSC.The results of calculation show that magnesium nitrate hexahydrate is dehydrated to magnesium nitrate when the temperature is above 168.02℃in standard state.In the process of program heating,first magnesium nitrate hexahydrate is melted to a solution,then magnesium nitrate dihydrate precipitates from the solution as the water loses.This dehydration process can be described according to the phase equilibrium of magnesium nitrate-water solution.Solid magnesium nitrate dihydrate is melted at 130℃.The melt is dehydrated to anhydrous magnesium nitrate,which involves a liquid-solid heterogeneous phase reaction.The melt is completely dehydrated to anhydrous magnesium nitrate at higher temperature than the calculated value,indicating that this dehydration reaction is thermodynamically spontaneous.

关 键 词：六水硝酸镁 脱水 热分析 热力学计算 

分 类 号：TQ13[化学工程—无机化工]