School of Chemistry, University of Nottingham, Nottingham, UK NG7 2RD.
Phys Chem Chem Phys. 2010 Feb 28;12(8):1772-83. doi: 10.1039/b920931j. Epub 2010 Jan 6.
The vaporisation of ionic liquids has been investigated using temperature programmed desorption (TPD) and ultra-high vacuum (UHV) distillation. 1-Alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquids, [C(n)C(1)Im][Tf(2)N] (n = 2, 8), have been distilled at UHV and T > 500 K in a specially designed still. The distillation process yielded spectroscopically pure ionic liquid distillates with complete removal of volatile impurities such as water, argon and 1-methylimidazole. Such UHV distillation offers a method of obtaining high purity ionic liquids for analytical applications. The vapour phase of the ionic liquid mixtures C(2)C(1)ImC(8)C(1)Im[Tf(2)N] and [C(2)C(1)Im][C(8)C(1)Im][Tf(2)N][EtSO(4)] has been analysed by TPD using line-of-sight mass spectrometry (LOSMS). The vapour phase consisted of all possible combinations of neutral ion pairs (NIPs) from the liquid mixture. Neither mixture showed evidence of decomposition during TPD, and the C(2)C(1)ImC(8)C(1)Im[Tf(2)N] mixture was shown to obey Raoult's law. Based on the TPD results, fractional distillations were attempted for [C(2)C(1)Im][C(8)C(1)Im]Tf(2)N and [C(2)C(1)Im][C(8)C(1)Im][Tf(2)N][EtSO(4)] mixtures. The distillate from [C(2)C(1)Im][C(8)C(1)Im]Tf(2)N was enhanced in the more volatile [C(2)C(1)Im][Tf(2)N] components, but the [C(2)C(1)Im][C(8)C(1)Im][Tf(2)N][EtSO(4)] mixture underwent significant decomposition. The similarities and differences between UHV TPD, and high vacuum distillation, of ionic liquids, are discussed. Design parameters are outlined for a high vacuum ionic liquid still that will minimise decomposition and maximise separation of ILs of differing volatility.
使用程序升温脱附（TPD）和超高真空（UHV）蒸馏研究了离子液体的蒸发。1-烷基-3-甲基咪唑双（三氟甲烷磺酰）亚胺离子液体，[C（n）C（1）Im][Tf（2）N]（n = 2,8），在专门设计的蒸馏器中在 UHV 和 T > 500 K 下进行蒸馏。蒸馏过程得到了光谱纯的离子液体馏分，完全去除了挥发性杂质，如水、氩气和 1-甲基咪唑。这种 UHV 蒸馏为分析应用提供了获得高纯度离子液体的方法。使用视线质谱法（LOSMS）通过 TPD 分析了离子液体混合物[C（2）C（1）Im]（0.05）[C（8）C（1）Im]（0.95）[Tf（2）N]和[C（2）C（1）Im] [C（8）C（1）Im] [Tf（2）N][EtSO（4）]的气相。气相由液体混合物中所有可能的中性离子对（NIP）组合组成。在 TPD 过程中，两种混合物均未显示分解的迹象，并且[C（2）C（1）Im]（0.05）[C（8）C（1）Im]（0.95）[Tf（2）N]混合物符合拉乌尔定律。基于 TPD 结果，尝试对[C（2）C（1）Im][C（8）C（1）Im][Tf（2）N]（2）和[C（2）C（1）Im][C（8）C（1）Im][Tf（2）N][EtSO（4）]混合物进行分步蒸馏。来自[C（2）C（1）Im][C（8）C（1）Im][Tf（2）N]（2）的馏分增强了更易挥发的[C（2）C（1）Im][Tf（2）N]成分，但[C（2）C（1）Im][C（8）C（1）Im][Tf（2）N] [EtSO（4）]混合物发生了明显的分解。讨论了离子液体的 UHV TPD 和高真空蒸馏之间的异同。概述了高真空离子液体蒸馏器的设计参数，该蒸馏器将最大限度地减少分解并最大程度地分离挥发性不同的 ILs。
