High-Pressure Phase Behavior of Carbon Dioxide in Ionic Liquids: 1-Alkyl-3-methylimidazolium Trifluoromethanesulfonate

摘要

Phase equilibrium data of carbon dioxide (CO2) in the ionic liquids (ILs) 1-alkyl-3- methylimidazolium trifluoromethanesulfonate ([Cn-mim][TfO], n = 2, 4, 6, 8) are presented at high-pressures up to about 45 MPa and at temperatures between 298.15 K and 343.15 K. CO2 gave very high solubilities in the ILs at lower pressure, while the equilibrium pressure increased very steeply at higher CO2 concentrations. The solubility of CO2 in the ILs decreased with an increase in temperature. The increase in the alkyl chain length on the cation of the [TfO] anion based ILs increased the CO2 solubility. In the modeling work, the critical properties and acentric factors of the ILs were estimated using the Joback’s group contribution method, and then the Peng-Robinson equation of state was used to calculate the phase behavior.