Evaporation Study of an Ionic Liquid with a Double-Charged Cation

Area of Science:

• Physical Chemistry
• Materials Science

Background:

• Dicationic ionic liquids (DILs) are advanced materials with unique properties.
• Understanding their thermophysical properties, like evaporation, is crucial for applications.

Purpose of the Study:

• To investigate the evaporation behavior of a specific dicationic ionic liquid: 1,3-bis(3-methylimidazolium-1-yl)propane bis(trifluoromethanesulfonyl)amide ([C3(MIm)22+][Tf2N-]2).
• To determine the vaporization characteristics (enthalpy and vapor pressure) of this DIL.
• To assess the impact of thermal decomposition on evaporation.

Main Methods:

• Knudsen effusion mass spectrometry was employed to study the evaporation process.
• The study analyzed the volatile products formed during evaporation.

Main Results:

• The dicationic ionic liquid undergoes partial thermal decomposition, yielding monocationic ionic liquids as volatile products.
• Despite decomposition, the vaporization characteristics of the parent dicationic ionic liquid were accurately determined.
• The vaporization enthalpy at 550 K was found to be (155.5 ± 3.2) kJ·mol−1.
• Saturated vapor pressure was described by the equation ln(p/Pa) = -(18699 ± 381)/(T/K) + (30.21 ± 0.82) between 508–583 K.

Conclusions:

• This study presents the first accurate determination of vaporization characteristics for a dicationic ionic liquid.
• The findings provide essential thermophysical data for [C3(MIm)22+][Tf2N-]2, aiding in its potential applications.
• Thermal decomposition does not impede the accurate measurement of vaporization properties for this class of compounds.