Studies on the structure of [Bmim][NO3] and 1-alkanol: Cohesive energy density and internal pressure

Abstract

The internal pressure (Pint), cohesive energy density (ced), and free volume (vf) for liquid mixtures of [Bmim][NO3] with (C5 to C7) 1-alkanol were calculated at 303.15 K and atmospheric pressure. Flory’s statistical theory was employed to drive the internal pressure of binary mixtures. The COSMO-RS model in combination with experimental densities was applied to calculate the cohesive energy density of the binary systems. The ‘structuredness’ of the fluids above was studied using the Pint/ced ratio. The values are between 0.2 and 0.6, as is the case for associated or ionic liquids, and demonstrates the chemical interactions for binary liquids. The variations of these parameters with mole fraction and length of alkyl chain in the studied 1-alkanol were explained from the perspective of intermolecular interactions. It is observed that increase in the methyl groups of alcohol creates additional steric hindrances, loosens the structural packing, and reduces the order of interactions in these mixtures. For binary mixtures of [Bmim][NO3] with 1-octanol, 1-nonanol, and 1-decanol a miscibility gap was observed in the mole fraction regions between 0.1 and 0.9.