Phase Behavior of Gases in Ionic Liquids

This presentation will emphasize the importance of characterizing the global phase behavior of gases in ionic liquids and how this can provide insight into new applications.  Solubility measurements of several gases in ionic liquids are discussed and important experimental details are highlighted when measuring the vapor-liquid equilibria using a gravimetric microbalance and vapor-liquid-liquid equilibria using a mass-volume technique.  The global phase behavior has been well correlated with a modified cubic equation and many of the systems described exhibit type-III and type-V phase behavior according to the van Konynenburg-Scott classification.  We have found that gases can exhibit different solubility behaviors in ionic liquids (i.e. physical and chemical absorption) and that these behaviors can be analyzed with the present equation of state using a simple association model and excess thermodynamic functions.  Gas separation using ionic liquids is discussed which includes examples of ternary phase behavior (experiments and model calculations) and what will be required to develop future commercial processes.