Thermal stability, specific heats, and surface tensions of ([emim][DCA] + [4empy][Tf2N]) ionic liquid mixtures

•Dynamic and isothermal TGA for ([emim][DCA] + [4empy][Tf2N]) mixtures were carried out.•MOTs for ([emim][DCA] + [4empy][Tf2N]) mixtures were properly predicted by pure IL dynamic data.•Specific heats for ([emim][DCA] + [4empy][Tf2N]) mixtures were measured from T = (296.2 to 372.2) K.•Surface tensions for ([emim][DCA] + [4empy][Tf2N]) mixtures were determined from T = (298.2 to 323.2) K.•Ideality of the ([emim][DCA] + [4empy][Tf2N]) mixtures was evaluated by calculating excess properties.

Lately, mixing ionic liquids (ILs) is a current trend in the investigation of the potential use of ILs as solvents in the liquid–liquid extraction of aromatics from aliphatic/aromatic mixtures. Several mixtures have shown high values of both aromatic/aliphatic selectivity and aromatic distribution ratio, which are the essential parameters an IL or a mixtures of ILs have to accomplish. However, it is also important to know the behavior of relevant aspects of the IL mixtures whether extraction results are of interest. The maximum operation temperature (MOT) is a key property to determine, because it limits the applicability of ILs to work without thermal decomposition. [emim][DCA] and [4empy][Tf2N] IL mixtures have shown good properties in liquid–liquid extraction of toluene from alkane/toluene mixtures. Isothermal analyses of the IL mixture were carried out to obtain an experimental decomposition interval for long-terms, whereas dynamic runs were performed to study several interesting parameters of the IL mixture and were also used to apply Seeberger et al. prediction model for long-terms behaviors. An ideal model to predict the behavior of the mixture was proposed and used in order to predict the MOT of the IL mixture from dynamic data of pure ILs involved in the mixture. To complete this study, specific heats and surface tensions of the mixture were measured and the ideality of the mixture in both cases was also evaluated through their excess properties.

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