Monoethanolamine and ionic liquid aqueous solutions as effective systems for CO_2 capture

摘要

BACKGROUND: Ionic liquids are regarded as future effective absorbents of CO_2, 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 CO_2 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 CO_2 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 CO_2 absorbed. CONCLUSIONS: The best results for CO_2 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 CO_2 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.