Vaporisation of an ionic liquid near room temperature

Abstract

The temperature at which the vapour phase of the ionic liquids (ILs) 1-ethyl-3-methylimidazolium bis[(trifluoromethane)sulfonyl]imide, [C₂C₁Im][Tf₂N], and 1-ethyl-3-methylimidazolium ethylsulfate, [C₂C₁Im][EtOSO₃], can be detected was investigated using line-of-sight mass spectrometry (LOSMS). By optimising the detection system used in previous experiments, the lowest temperature for which vapour was detected for [C₂C₁Im][Tf₂N] was ∼340 K, whereas for [C₂C₁Im][EtOSO₃] it was ∼390 K. Initial investigations also show that the temperature at which measurements are made affects the enthalpy of vaporisation at 298 K, Δ_vapH₂₉₈. The reasons for these differences in Δ_vapH₂₉₈ with respect to temperature are discussed. The vapour pressure of both ILs is estimated at far lower temperatures than previously achieved and extrapolations to room temperature are given.