Solubilities and thermodynamic properties of gases in the ionic liquid 1-n-butyl-3-methylimidazolium hexafluorophosphate

This work presents the solubility of nine different gases in 1-n-butyl-3-methylimidazolium hexafluorophosphate. The gases considered include carbon dioxide, ethylene, ethane, methane, argon, oxygen, carbon monoxide, hydrogen, and nitrogen. We also report the associated Henry's constants and enthalpies and entropies of absorption. We found carbon dioxide to have the highest solubility and strongest interactions with the ionic liquid, followed by ethylene and ethane. Argon and oxygen had very low solubilities and immeasurably weak interactions. Carbon monoxide, hydrogen, and nitrogen all had solubilities below the detection limit of our apparatus. Our results suggest that the mass transfer of gases into ionic liquids likely will be an important issue for reactions involving these gases. We also determined that ionic liquids show good potential for use as a gas-separation medium.