Phase behavior of carbon dioxide and oxygen in the ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide

The phase behavior of carbon dioxide and oxygen mixtures in the ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [hmim][Tf2N], at (40 å± 0.5) ̊C was investigated. Experiments were carried out in a fixed volume high pressure view cell with the vapor phase being sampled and analyzed using a gas chromatograph. Solubility data was determined by difference. Measurements were carried out at equilibrium pressures from 18.7 to 72.5 bar and feed compositions of 25, 35, and 50 mole percent oxygen with the balance being carbon dioxide. Noticeable enhancement was seen at pressures greater than 30 bar and was quantified by calculating enhancement factors and showing ternary diagrams. These results were compared with those of the same system at a lower temperature and carbon dioxide-expanded organic solvents.