High-pressure phase equilibria of systems with ionic liquids

Abstract

In this work, the phase behavior of the binary systems of carbon dioxide (CO 2) + 1-ethyl-3-methylimidazolium hexafluorophosphate ([emim][PF 6]), CO 2 + 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF 6]), and CO 2 + 1-hexyl-3-methylimidazolium hexafluorophosphate ([hmim][PF 6]) have been studied experimentally. A synthetic method was used to measure vapor–liquid boundaries. Pressures up to 97 MPa have been applied. The effect of the different alkyl groups on the CO 2 solubility in the various ionic liquids has been analysed. Also, it has been shown that the phase behavior of the systems CO 2 + [emim][PF 6] and CO 2 + [bmim][PF 6] are completely different in comparison with the phase behavior of the systems trifluoromethane (CHF 3) + [emim][PF 6] and CHF 3 + [bmim][PF 6], respectively.