Improving Physical Absorption of Carbon Dioxide by Ionic Liquid Dispersion

An ionic liquid (IL), 1-butylimidazole hexafluoride phosphate [bmim]PF4, was dispersed in surfactant solution to form an IL-in-water emulsion. Physical absorption of CO2 was carried out in this emulsion system. Absorption rates of CO2 under different operating conditions were obtained by experimental measurements. CO2 concentrations in the bulk of absorbent and the local volumetric mass transfer coefficients of the liquid phase were calculated by model calculation. Experimental results indicate that the dispersed IL droplets in aqueous solution can significantly enhance CO2 mass transfer at the gas-liquid interface. This phenomenon can be ascribed to the increase of mass transfer driving force and local volumetric mass transfer coefficient. The shuttle effect and hydrodynamic effect proved to play important roles for CO2 absorption improved by dispersed IL.