Water Desorption Process in Room Temperature Ionic Liquid-H2OMixtures: N,N-diethyl-N-methyl-N-(2-methoxyethyl) Ammonium Tetrafluoroborate

Hiroshi Abe,1 TomohiroMori,1 Yusuke Imai,1 and Yukihiro Yoshimura2


1Department of Materials Science and Engineering, National Defense Academy, Yokosuka, Kanagawa 239-8686, Japan
 2Department of Applied Chemistry, National Defense Academy, Yokosuka, Kanagawa 239-8686, Japan

Journal of Thermodynamics Volume 2012, Article ID 351968, 5 pages

Abstract
A water desorption process of a mixture of room temperature ionic liquid (N, N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium tetrafluoroborate) and water was investigated via simultaneous X-ray diffraction and differential scanning calorimetry (DSC) measurements, in which relative humidity was controlled by a water vapor generator. In these measurements, H2O concentration was estimated by the peak position of the principal peak in X-ray diffraction patterns, and the thermal property associated with a mixing state was detected by a DSC thermograph. In addition, the density of the mixture was measured as a macroscopic property. In situ observations revealed that the thermally unstable mixing state in the water-rich region has an important correlation with density and thermal and structural properties.

Fig. 1
A [DEME] cation and a [BF4] anion.


Fig. 2
Temperature and concentration dependences of density in [DEME][BF4]-x mol% H2Omixtures.
Fig. 3.
Concentration dependence of volumetric thermal expansion coefficient, β, at 25.C.
Fig. 4.
Time dependence of Qmax position.
Fig. 5.
x-Qmax relationship. Solid curve is obtained by the least square fitting method.
Fig. 6.
Time dependences of (a) water concentrations and (b) mass.
Fig. 7.
Water concentration dependence of normalized heat flow.
Fig. 8.
Time dependence of the normalized heat flow. For a comparison, the normalized heat flow at 30.C and 85%RH is plotted as background, where a little mass change was measured after the DSC scan.
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