Thermophysical properties of imidazolium-based ionic liquids
Thermophysical properties of imidazolium-based ionic liquids
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DOI：
10.1021/je034261a
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发表时间：
2004-07-01
期刊：
影响因子：
--
通讯作者：
Brennecke, JF
中科院分区：
文献类型：
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作者：
Fredlake, CP;Crosthwaite, JM;Brennecke, JF
离子液体（Ionic Liquids，IL）是在低温下为液体的盐，通常包括室温附近的区域。它们正受到密切的研究，特别是作为反应和分离的替代溶剂，因为它们表现出可忽略的蒸气压，因此不会造成空气污染。显然，基本的热物理性能对于这些应用的设计和评估至关重要。我们目前的密度作为温度的函数，熔融温度，玻璃化转变温度，分解温度，和热容量作为温度的函数的一系列的13个流行的咪唑基离子液体。本文研究的离子液体有1-丁基-3-甲基咪唑四氟硼酸盐、1-丁基-3-甲基咪唑六氟磷酸盐、1-丁基-3-甲基咪唑氯化物、1-丁基-3-甲基咪唑溴化物、1-丁基-3-甲基咪唑二氰胺盐、1-丁基-3-甲基咪唑三氟甲磺酸盐、1-（三氟甲基磺酰基）甲基化物，1-丁基-3-甲基咪唑鎓双（三氟甲基磺酰基）酰亚胺，1-乙基-3-甲基咪唑（三氟甲基磺酰基）亚胺，2，3-二甲基-1-乙基咪唑鎓双（三氟甲基磺酰基）亚胺，2，3-二甲基-1-丙基咪唑鎓双（三氟甲基磺酰基）酰亚胺、1-丁基-2，3-二甲基咪唑四氟硼酸盐和1-丁基-2，3-二甲基咪唑六氟磷酸盐。属性遵循相当合理的趋势。例如，密度随着阳离子上烷基链长度的增加而减小。对于给定的阳离子，密度随着阴离子分子量的增加而增加。许多离子液体倾向于容易过冷，在非常低的温度下形成玻璃，而不是表现出结晶或熔融转变。热稳定性随着阴离子尺寸的增加而增加，并且热容随着温度和IL中原子数目的增加而增加。
Ionic liquids (ILs) are salts that are liquid at low temperatures, usually including the region around room temperature. They are under intense investigation, especially as replacement solvents for reactions and separations, since they exhibit negligible vapor pressure and would not, therefore, contribute to air pollution. Clearly, basic thermophysical properties are vital for design and evaluation for these applications. We present density as a function of temperature, melting temperatures, glass-transition temperatures, decomposition temperatures, and heat capacities as a function of temperature for a series of 13 of the popular imidazolium-based ILs. The ionic liquids investigated here are 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium dicyanamide, 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-methylimidazolium tris(trifluoromethylsulfonyl)methide, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium his(trifluoromethylsulfonyl)imide, 2,3-dimethyl-1-ethylimidazolium bis(trifluoromethylsulfonyl)imide, 2,3-dimethyl-1-propylimidazolium bis(trifluoromethylsulfonyl)imide, 1-butyl-2,3-dimethylimidazolium tetrafluoroborate, and 1-butyl-2,3-dimethylimidazolium hexafluorophosphate. The properties follow quite reasonable trends. For instance, density decreases as the length of the alkyl chain on the cation increases. For a given cation, the density increases as the molecular weight of the anion increases for the anions studied here. Many of the ILs tend to subcool easily, forming glasses at very low temperatures rather than exhibiting crystallization or melting transitions. The thermal stability increases with increasing anion size, and heat capacities increase with temperature and increasing number of atoms in the IL.