Experimental Thermodynamic Properties of 1-Butyl-2-methylpyridinium Tetrafluoroborate [b2mpy][BF₄] with Water and with Alkan-1-ol and Their Interpretation with the COSMO-RS Methodology

Abstract

This work provides experimental data on liquid−liquid equilibria in the range 288−328 K and data of HmE and VmE at temperatures of 298.15 and 318.15 K, for binary mixtures corresponding to 1-butyl-2-methylpyridinium tetrafluoroborate, [b2mpy][BF4], with alkanols (methanol to pentan-1-ol) and water. The [b2mpy][BF4] is completely miscible in water, and all the mixtures give positive values of HmE and VmE, giving increasing values of excess quantities with temperature. For mixtures with alkanols, values of HmE > 0 are obtained with VmE < 0, endothermic effects accompanied by contraction, with temperature changes represented by (dHmE/dT)p > 0 and (dVmE/dT)p > 0. Experimental data are correlated with a suitable equation and are presented together with those obtained in previous works for another two isomers, [b3mpy][BF4] and [b4mpy][BF4], and the properties of all of them are compared and discussed along with their behavior. The quantum-chemical method COSMO-RS is applied for the first time to predict excess properties of these mixtures containing ionic liquids, and the results show a significant contribution of hydrogen bond interactions in the behavior of the mixtures studied here, generically referred to as [bXmpy][BF4] (X = 2, 3, 4) + H2O or + CvH2v+1(OH) (v = 1−5).