Ammonia solubilities in room-temperature ionic liquids

The solubilities of ammonia in the room-temperature ionic liquids 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]), 1-hexyl-3-methylimidazolium chloride ([hmim][Cl]), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([emim][Tf2N]), and 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) have been measured for the first time. New static phase equilibrium cells have been constructed for the present experiment. Isothermally fixed temperatures are similar to 283, 298, 323, 348, and 355 K, and six mixture compositions are prepared (from similar to 10 mol % to 85 mol % ammonia) at the ambient temperature. The observed solubilities are high: in fact, they are among the highest ever reported in the literature for room-temperature mixtures that contain ionic liquids. Observed pressure-temperature-composition (PTx) data have been successfully correlated with our previous equation of state (EOS) model. Possible applications of the present systems to the absorption cooling/heating cycle have been discussed, in comparison to the traditional ammonia-water system.