High pressure phase behaviour of methane in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide

Solubility data of methane in the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide are presented within temperature and pressure ranges of 300–450 K and 1–16 MPa, respectively. Experiments were carried out in a view-cell based on the synthetic method. Results indicated rather low methane solubility in the ionic liquid, ranging from 3 up to 22 mole% at the higher pressure limit of 16 MPa. In comparison to some other gases of concern to ionic liquid gas purification membranes, methane had much lower solubility than carbon dioxide and higher solubility than hydrogen. Isothermal methane solubility was shown to increase with pressure in an almost linear manner. However, temperature effects were more predominant at low temperatures, i.e. increasing the temperature caused a more notable decrease in solubility at lower temperatures than at higher temperatures. Solubility results of methane are also compared to those of ethane, propane and butane in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. Methane is by far less soluble than ethane, propane, and butane.