Kinetics of absorption of CO2 in amino-functionalized ionic liquids

The kinetics of the reaction of CO2 with a primary amine functionalized ionic liquid (NH2-RTIL) at 303 K and 333 K are studied in this work. The absorption of CO2 was carried out by the decreasing pressure method in a gas–liquid stirred cell reactor. The volumetric mass transfer coefficient of the liquid phase was determined from the experiments using [bmim]BF4 as liquid phase and the kinetics of the reaction was studied based on the experiments carried out with a liquid phase containing [bmim]BF4 and 1-(3-aminopropyl)-3-methylimidazolium tetrafluoroborate ([APmim]BF4) at concentrations between 45 and 253 mol m−3. The enhancement factor due to the chemical reaction was calculated from the fluxes of CO2 absorbed. The kinetic results were analyzed using the general solution given by Van Krevelen and Hoftijzer based on the film model and the approximate solution of DeCoursey based on the Danckwerts surface renewal model. The results indicate that the reaction takes place in an intermediate regime limited by diffusion of the amine functionalized ionic liquid. The reaction was assumed first order in both CO2 and [APmim]BF4 and the calculated kinetic constants (k1,1) are of the same order of magnitude as the ones available for primary amines and CO2 in viscous media.