Influence of temperature on CO2 absorption rate and capacity in ionic liquids

Abstract

Ionic liquids (ILs) present a new alternative for postcombustion CO2 capture because their properties can be tuned by means of different cation−anion combinations in order to obtain the most suitable properties for a specific task. This work is a novel study that investigates the absorption kinetics and evolution of the chemical transformations produced by CO2 absorption in ILs at different temperatures. A large range of pure ILs was tested with a screening process based on the pKa anion for efficient and reversible CO2 capture. CO2 uptake by selected ILs was determined for a wide range of pressures between atmospheric pressure and 2000 kPa at room temperature. Results show that CO2 absorption capacities of [bmim][Ac] and [bmim][Phen] at 100 kPa are close to those obtained at higher pressures, suggesting the existence of two solvation regimes. This was confirmed by IR analysis. The kinetics were significantly affected by the temperature and were shown to increase sharply with it. The optimum temperature for CO2 capture in [bmim][Ac] and [bmim][Phen] was found to be 323.15 and 348.15 K, respectively.