Abstract Reversible thermal dehydration reaction of MgCl2·6H2O has been studied as a potential working way for thermochemical heat storage with high energy density. Understanding its complex multistep dehydration behavior is significant for guiding practical applications; however, there is a lack of deep understanding about the phase transition of MgCl2·6H2O during its dehydration reaction process. In this work, the reaction mechanism, dehydration kinetics, and equilibrium behaviors of MgCl2·6H2O are studied in detail with the help of thermal analytical measurements and morphological observations. The thermogravimetric analysis coupled with differential scanning calorimetry (TG-DSC) shows the dehydration behavior and reaction pathways varying with gas atmosphere, heating rate, water vapor pressure, and sample mass. The formation of intermediate molten MgCl2·6H2O is identified that it makes strong effects on the dehydration kinetics and reaction equilibrium. Futhermore, a revised Clapeyron equilibrium equation is developed and experimentally verified for describing the reaction equilibrium of molten MgCl2·6H2O. It is expected that the findings in this study pave paths for efficient thermal energy storage application based on MgCl2·6H2O.

中文翻译：

---

用于热能储存的六水氯化镁的脱水动力学和热力学

摘要 MgCl2·6H2O 的可逆热脱水反应作为一种潜在的高能量密度热化学蓄热方式已被研究。了解其复杂的多步脱水行为对于指导实际应用具有重要意义；然而，对MgCl2·6H2O在其脱水反应过程中的相变缺乏深入的了解。在这项工作中，借助热分析测量和形态观察，详细研究了 MgCl2·6H2O 的反应机理、脱水动力学和平衡行为。热重分析结合差示扫描量热法 (TG-DSC) 显示脱水行为和反应途径随气体气氛、加热速率、水蒸气压和样品质量而变化。确定中间熔融态MgCl2·6H2O的形成对脱水动力学和反应平衡有很大影响。此外，还建立了一个修正的克拉珀龙平衡方程并通过实验验证，用于描述熔融 MgCl2·6H2O 的反应平衡。预计本研究的发现为基于 MgCl2·6H2O 的高效热能存储应用铺平了道路。