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Keywords:

  • 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide;
  • 1-butyl-3-methylimidazolium bis(trifluoromethylsullfonyl)amide;
  • H2;
  • phase equilibria;
  • vapor-liquid equilibria

Abstract

Previously unavailable high-pressure solubility data of hydrogen in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide has been measured experimentally up to temperatures and pressures of 450 K and 15 MPa, respectively. In contrast to CO2 solubility, H2 tends to dissolve better in the ionic liquid at higher temperatures. This “inverse” temperature effect has been studied from a thermodynamic perspective and the underlying reason for this effect is explained. It is shown that the negative P-T slope is not limited to this particular binary mixture, but is the typical behavior in most, if not all, H2 + ionic liquid systems. However, there is a certain range of temperatures, pressures, and concentrations in which this phenomenon occurs. By predicting the Scott-van Konynenburg phase diagram for systems of H2 + ionic liquids to be of type III, it is shown how and why the solubility increases with temperature in some regions, but decreases in others. © 2012 American Institute of Chemical Engineers AIChE J, 2012