Solubility of CO₂ in Binary Mixtures of Room-Temperature Ionic Liquids at High Pressures

Abstract

The solubility data of carbon dioxide (CO2) in a series of ionic liquids (ILs): 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM]+[BF4]−), 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]+[BF4]−), 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([OMIM]+[Tf2N]−), and their binary mixtures (i.e., [EMIM]+[BF4]− + [OMIM]+[Tf2N]− and [BMIM]+[BF4]− + [OMIM]+[Tf2N]−) at temperatures (313.2 and 333.2) K and pressures up to 6 MPa were measured by a high-pressure view-cell technique. The mixed ILs tested were (0, 20, 50, 80, and 100) wt % [EMIM]+[BF4]− (or [BMIM]+[BF4]−) in [OMIM]+[Tf2N]−. The solubility data of CO2 in pure ILs were correlated with the Peng–Robinson equation of state (PR EOS), whereas the solubility data of CO2 in mixed ILs can be well predicted based on the mole fraction average of [EMIM]+[BF4]− (or [BMIM]+[BF4]−) and [OMIM]+[Tf2N]− over the solubility of CO2 in pure ILs. It was found that the solubility of CO2 in pure or mixed ILs increases with increasing pressure at all temperatures but decreases with increasing temperature. The Henry’s constants follow the order of [BMIM]+[BF4]− + [OMIM]+[Tf2N]− > [EMIM]+[BF4]− + [OMIM]+[Tf2N]− at the same content of [OMIM]+[Tf2N]−. The use of mixed ILs provides the opportunity to tune the solubility and selectivity for capturing CO2 at high pressures. It is the first work for us to present the solubility data of CO2 in binary mixtures of ILs at high pressures for physical absorption.

Gas solubility in long‐chain imidazolium‐based ionic liquids

“…In particular, COSMO‐RS model shows good prediction for [SCN]‐based ILs, but the Valderrama's equation gives worse results. Moreover, the FFV for IL of [C 4 MIM][Tf 2 N] was 0.1271 obtained in this work, while the value is 0.1281 as calculated by Shannon et al, indicating the validation of the calculation method. It can be seen that the free volume exhibits a linear relationship with the carbon number in the alkyl side‐chain on the cation in each [C n MIM][X] series.…”

“…The temperature of the still was controlled by electric heating elements with an uncertainty of ± 0.1 K, and the system pressure was measured by a pressure gauge with a range of 0–20.00 MPa and an uncertainty of ± 0.01 MPa. The details of apparatus and procedure have been described in our previous publications …”

“…The details of apparatus and procedure have been described in our previous publications. 22,23 Computational Details…”

“…[35][36][37][38] It can be seen that the COSMO-RS model gives excellent prediction for IL density with the ARD less than 2%. In particular, COSMO-RS model 22 indicating the validation of the calculation method. It can be seen that the free volume exhibits a linear relationship with the carbon number in the alkyl side-chain on the cation in each [C n MIM][X] series.…”

Carbon Dioxide Capture with Ionic Liquids and Deep Eutectic Solvents: A New Generation of Sorbents

“…Lei et al. examined CO 2 solubility in binary mixtures of imidazolium‐based ILs . [C 8 MIM][Tf 2 N] with a fluoroalkyl group and long alkyl chain length was chosen to achieve high CO 2 solubility, and the other IL was [C 2 MIM][BF 4 ] or [C 4 MIM][BF 4 ] for high selectivity.…”