The CO(2) Absorption in Flue Gas Using Mixed Ionic Liquids

Because of the appealing properties, ionic liquids (ILs) are believed to be promising alternatives for the CO(2) absorption in the flue gas. Several ILs, such as [NH(2)emim][BF(4)], [C(4)mim][OAc], and [NH(2)emim[OAc], have been used to capture CO(2) of the simulated flue gas in this work. The structural changes of the ILs before and after absorption were also investigated by quantum chemical methods, FTIR, and NMR technologies. However, the experimental results and theoretical calculation showed that the flue gas component SO(2) would significantly weaken the CO(2) absorption performance of the ILs. SO(2) was more likely to react with the active sites of the ILs than CO(2). To improve the absorption capacity, the ionic liquid (IL) mixture [C(4)mim][OAc]/ [NH(2)emim][BF(4)] were employed for the CO(2) absorption of the flue gas. It is found that the CO(2) absorption capacity would be increased by about 25%, even in the presence of SO(2). The calculation results suggested that CO(2) could not compete with SO(2) for reacting with the IL during the absorption process. Nevertheless, SO(2) might be first captured by the [NH(2)emim][BF(4)] of the IL mixture, and then the [C(4)mim][OAc] ionic liquid could absorb more CO(2) without the interference of SO(2).