Monoethanolamine and ionic liquid aqueous solutions as effective systems for <scp>CO₂</scp> capture

Abstract

Abstract 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 CO 2 absorbent and the influence of solution composition on the volume of CO 2 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 CO 2 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. © 2012 Society of Chemical Industry