High-pressure phase behavior of binary mixtures containing ionic liquid [HMP][Tf2N], [OMP][Tf2N] and carbon dioxide

This paper presents bubble-point pressure data for CO2 in ionic liquids 1-hexyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([HMP][Tf2N]) and 1-octyl-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([OMP][Tf2N]) at pressures up to approximately 62 MPa and temperatures between 303.15 and 373.15 K. The solubility of CO2 in ionic liquids was measured with a high-pressure variable-volume view cell. At high CO2 concentrations in ionic liquids, the equilibrium pressure increased sharply with increasing CO2 concentrations while the solubility of CO2 in the ionic liquids decreased commensurate to increases in temperature. We have observed that in the [Tf2N] anion-based ionic liquids, the shorter the alkyl group chain in cation is, the larger the solubility of CO2 in ionic liquid become. The experimental data for the CO2 + ionic liquid system were relatively well correlated using the Peng–Robinson equation of state.

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• Solubility of CO2 in [HMP][Tf2N] and [OMP][Tf2N] at 303.15–373.15 K, up to 62 MPa.
• Solubility of CO2 decreased commensurate to increase in temperature.
• In [Tf2N] anion-based IL, CO2 solubility decreased with alkyl chain length in cation.
• The PR-EoS well correlates these CO2 + ionic liquid systems.