No abstract

Ionic liquids are the basis of a potential alternative to conventional processes based on aqueous amines currently used for carbon dioxide capture. Mixtures of ionic liquids offer an additional degree of tailoring over the intrinsic tunable properties of "single" ionic liquids, while totally maintaining the ionic liquid character. In this work, two mixtures of mutually miscible ionic liquids have been investigated, namely, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide + 1-ethyl-3-methylimidazolium ethylsulfate and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide + 1-butyl-3-ethylimidazolium ethylsulfate. Their ability to absorb carbon dioxide in the pressure range up to ca. 16 bar, at 298.2 K, was determined at different composition ratios of the mixtures; their thermal phase-transition temperatures and physical properties (density, viscosity, and surface tension) were determined over the entire compositional range, at atmospheric pressure and the same temperature. The absorption data were adequately correlated by the NRTL (Non-Random Two-Liquid) model, whereas different equations were successful in satisfactorily correlating the physical properties of the mixtures and in predicting them from knowledge of the properties of the pure ionic liquid components.

With a decrease in world oil reserves and a higher demand for petroleum and its derived products, the effective exploitation of oil reservoirs has become increasingly important. Enhanced oil recovery (EOR) assisted by surfactants is an effective method for recovering the oil from reservoirs that have lost their drive after the application of primary and secondary recovery methods. This research is aimed at showing the suitability of several ionic liquids as effective replacements for conventional surfactants in EOR. The reservoir fluid has been modelled as a ternary system of water (pure water or aqueous solution of NaCl) plus the ionic liquid trihexyl(tetradecyl)phosphonium chloride plus dodecane. Determination of its liquid-liquid phase equilibrium indicates the formation of a Winsor type III system, with a triphasic region and adjacent biphasic regions. The interfacial tensions in the system corroborate the ability of the ionic liquid to act as a surface active agent, as desirable for its use in an EOR process. A relevant transport property such as viscosity, in addition to density, has been experimentally measured for the equilibrium phases.