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Keywords:

  • CO2 absorption;
  • aqueous solutions of ionic liquids;
  • monoethanolamine;
  • 1-butyl-3-methylimidazolium acetate;
  • 1-ethyl-3-methylimidazolium octylsulfate

Abstract

BACKGROUND

Ionic liquids are regarded as future effective absorbents of CO2, however high viscosity of this medium limits its use in industry. To resolve the problem a mixture of alkanolamine, ionic liquids and water was proposed as a CO2 absorbent and the influence of solution composition on the volume of CO2 absorbed was determined.

RESULTS

In most binary mixtures of ionic liquids and water tasted the presence of water does not affect the overall capacity of absorption mixture except for the 1-butyl-3-methylimidazolium acetate where each mol of water added to the mixture reduces the volume of CO2 that could be absorbed by more than one mole. The capture of CO2 using three-component systems of water/ionic liquid/monoethanolamine (MEA) was systematically investigated with two selected ionic liquids: 1-butyl-3-methylimidazolium acetate and 1-ethyl-3-methylimidazolium octylsulfate. It was shown that the volume of CO2 absorbed is linearly dependent on the mass fraction of components for 1-ethyl-3-methylimidazolium octylsulfate over the entire experimental domain whereas in 1-butyl-3-methylimidazolium acetate the interaction between ionic liquid and water substantially decreases the volume of CO2 absorbed.

CONCLUSIONS

The best results for CO2 absorption were obtained using the three component system 1-butyl-3-methylimidazolium acetate/monoethanolamine/water. Optimization of the composition of an IL-MEA-water mixture allows tuning of the properties of the medium. The CO2 absorption capacity of the mixture is mainly a function of MEA concentration and, to a lesser degree, of the concentration of IL possessing chemisorption abilities. The presence of water decreases the viscosity of the mixture and therefore facilitates the application of IL-based media in industrial applications. © 2012 Society of Chemical Industry