Effect of lithium tetrafluoroborate on the solubility of carbon dioxide in the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate

In this work, the phase behavior of the ternary system of carbon dioxide +1-butyl-3-methylimidazolium tetrafluoroborate + lithium tetrafluoroborate has been investigated. Mixtures of known concentrations of the salt, ionic liquid and carbon dioxide were prepared and their bubble point pressures were measured at different temperatures. Results are reported for this ternary system, at carbon dioxide concentrations of 20.2, 27.6 and 35.2 mol-% and salt concentrations of 0.0, 6.0, 11.5, 16.3 and 21.1 mol-% (on a carbon-dioxide free basis) and within temperature and pressure ranges of 293.15–358.15 K and 1.2–11.3 MPa, respectively. It was observed that the addition of the salt increased the bubble point pressure and its effect was concentration-dependent, i.e. at higher concentrations of the salt, higher pressures are required. This behavior is greater at higher temperatures.