Improvement of the CO2 Absorption Performance Using Ionic Liquid [NH2emim][BF4] and [emim][BF4]/[bmim][BF4] Mixtures

Functional ionic liquids (ILs) have potential advantages in reducing CO 2 emissions when applied for CO 2 absorption. However, the higher viscosity of functional ILs greatly affects the CO 2 absorption separation process. To improve the absorption performance, a functional IL [NH 2 e-mim][BF 4 ] was synthesized and mixed with low-viscosity conventional ILs [emim][BF 4 ]/[bmim][BF 4 ] based on their respective advantages in terms of CO 2 reduction, and the CO 2 absorption effect and regeneration performance of the binary ILs were investigated. {[NH 2 e-mim][BF 4 ] + [emim][BF 4 ]/[bmim][BF 4 ]} showed better performance when the mole fraction of [NH 2 e-mim][BF 4 ] ( X [NH 2 e-mim][BF 4 ] ) was 0.4, and the CO 2 absorption performance reduced with the increase in the temperature. Density and viscosity of the binary rose with the increase of X [NH 2 e-mim][BF 4 ] and decrease in temperature. The optimal regeneration temperature was approximately 353.15 K when X [NH 2 e-mim][BF 4 ] was 0.4 in 0.1 MPa. During five cycles of absorption and regeneration, CO 2 absorption capacity of {[NH 2 e-mim][BF 4 ] + [emim][BF 4 ]/[bmim][BF 4 ]} was maintained at 75–85% of the first absorption capacity. Moreover, the quality and density changed slightly, and viscosity showed a 5–10% increase in each loop. Thus, the mixed system had an effective regeneration performance.