CO2-Capturing Capacity of [BEIM]-Cation-Based Ionic Liquids ([BEIM][Tf2N], [BEIM][BF4], and [BEIM][PF6])

New experimental phase equilibrium data and parameterswere determinedfor the binary system of CO2 + 1-butyl-3-ethylimidazolium([BEIM]) cation-based ionic liquids (1-butyl-3-ethylimidazolium bis(trifluoromethylsulfonyl)imide([BEIM][Tf2N]), 1-butyl-3-ethylimidazolium tetrafluoroborate([BEIM][BF4]), and 1-butyl-3-ethylimidazolium hexafluorophosphate([BEIM][PF6])). A variable-volume view cell was used tomeasure the equilibrium state, and the Peng-Robinson equationof state with the van der Waals one-fluid mixing rule was used tocorrelate the data points. Measurements were made in the temperaturerange of 313.2-373.2 K at 10 K intervals. The average absolutedeviations of pressure (AAD-P%) between the calculated and experimentalequilibrium pressures were calculated, with values of 1.62, 1.99,and 1.37 for the [BEIM][Tf2N] + CO2, [BEIM][BF4] + CO2, and [BEIM][PF6] + CO2 systems, respectively. The relatively small differences (less than2%) among the three systems confirmed the accuracy of the experiment.The CO2 solubility in the three systems was ranked in theorder [BEIM][Tf2N] > [BEIM][PF6] > [BEIM][BF4]. The experimental data at 313.2 and 373.2 K were comparedwith those of other imidazolium-based ionic liquids such as 1-butyl-3-methylimidazolium([BMIM]) and 1-hexyl-3-methylimidazolium ([HMIM]). The CO2 solubilities in the [BMIM] and [HMIM] cation-based ionic liquidswere comparable.