CO(2) Capture and Separation Properties in the Ionic Liquid 1-n-Butyl-3-Methylimidazolium Nonafluorobutylsulfonate

Recently, the use of ionic liquids (ILs) for carbon capture and separation processes has gained great interest by many researchers due to the high solubility of CO(2) in ILs. In the present work, solubility measurements of CO(2) in the novel IL 1-n-butyl-3-methylimidazolium nonafluorobutylsulfonate [C(4)mim][CF(3)CF(2)CF(2)CF(2)SO(3)] were performed with a high-pressure view-cell technique in the temperature range from 293.15 to 343.15 K and pressures up to about 4.2 MPa. For comparison, solubilities of H(2), N(2), and O(2) in the IL were also measured at 323.15 K via the same procedure. The Krichevsky-Kasarnovsky equation was employed to correlate the measured solubility data. Henry’s law constants, enthalpies, and entropies of absorption for CO(2) in the IL were also determined and presented. The CO(2) solubility in this IL was compared with other ILs sharing the same cation. It was shown that the solubility of CO(2) in these ILs follows the sequence: [C(4)mim][CF(3)CF(2)CF(2)CF(2)SO(3)] ≈ [C(4)mim][Tf(2)N] > [C(4)mim][CF(3)CF(2)CF(2)COO] > [C(4)mim][BF(4)], and the solubility selectivity of CO(2) relative to O(2), N(2), and H(2) in [C(4)mim][CF(3)CF(2)CF(2)CF(2)SO(3)] was 8, 16, and 22, respectively. Furthermore, this IL is regenerable and exhibits good stability. Therefore, the IL reported here would be a promising sorbent for CO(2).