Relative Volatilities of Ionic Liquids by Vacuum Distillation of Ionic Liquid Mixtures

Published

June 7, 2007

Author(s)

Jason A. Widegren, Yi-ming Wang, Wesley A. Henderson, Joe W. Magee

Abstract

The relative volatilities of a variety of common, aprotic ionic liquids have been determined for the first time. Equimolar mixtures of ionic liquids were vacuum distilled in a glass sublimation apparatus at approximately 473 K. The composition of the initial distillate, determined by NMR spectroscopy, was used to establish the relative volatility of each ionic liquid in the mixture. The effect of alkyl chain length was studied by distilling mixtures of 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquids, or mixtures of N-alkyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquids, with different alkyl chain lengths. For both classes of salts the volatility is highest when the alkyl side chain is a butyl group. The effect of cation structure on volatility has been determined by distilling mixtures containing different types of cations. Generally speaking, ionic liquids based on imidazolium and pyridinium cations are more volatile than ionic liquids based on ammonium and pyrrolidinium cations, regardless of the types of counter ions present. Similarly, ionic liquids based on the anions [(C₂F₅SO2)₂N] , [(C₄F₉SO₂)(CF₃SO₂)N] and [(CF₃SO₂)₂N] are more volatile than ionic liquids based on [(CF₃SO₂)₃C] and [CF₃SO₃] , and are much more volatile than ionic liquids based on [PF₆] .

Citation

Journal of Physical Chemistry B

Volume

111

Pub Type

Journals

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Keywords

dustillation, ionic liquid, vapor pressure, volatility

Citation

Widegren, J. , Wang, Y. , Henderson, W. and Magee, J. (2007), Relative Volatilities of Ionic Liquids by Vacuum Distillation of Ionic Liquid Mixtures, Journal of Physical Chemistry B, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=50487 (Accessed April 19, 2024)