María J. Dávila

On the properties of 1-butyl-3-methylimidazolium octylsulfate ionic liquid

This work reports on a theoretical and experimental study on the ionic liquid 1-butyl-3-methylimidazolium octylsulfate ([BMIM]OS). The halogen-free ionic liquid [BMIM]OS is a stable solvent regarding hydrolysis, whose availability, toxicologically favourable features and well documented biodegradability turns it into a suitable candidate for different multiton-scale industrial applications. The pressure–volume–temperature behaviour of this fluid has been evaluated accurately over wide ranges of temperature and pressure, and correlated successfully with the empirical TRIDEN equation. From the measured data the relevant derived coefficients, isothermal compressibility, isobaric expansibility and internal pressure have been calculated. Other valuable properties such as isobaric heat capacity, speed of sound and refractive index were measured at several temperatures and atmospheric pressure. The molecular structure was looked into by quantum computations at the B3LYP/6-31 + g(d) level and classical molecular dynamics simulations in the NPT ensemble with the OPLS–AA forcefield. Both macroscopic and microscopic studies concur in a complex structure involving microheterogenous polar and non-polar domains, brought about by the aggregation of the non-polar anionic chains.

Solute–solvent interactions in lactams–water ternary solvents

This work reports on a variety of experiments performed as a contribution to an improved understanding of the structure and dynamics of amide-water mixtures. Several thermophysical properties of the pyrrolidin-2-one–N-methylpyrrolidinone–water ternary mixed solvent and its binary constituents were measured at 298.15 K. From the experimental readings excess and mixing properties were evaluated and analyzed in connection with structural effects and ternary interactions. The properties investigated support the formation of strong hydrogen bonds between water and the cyclic amides. For the binary constituents, the derived properties support 1∶2 PYR–water and 1∶3 NMP–water intermolecular interactions. The observed weakening of hydrogen bonds in the ternary system compared with the binary constituents reveals that no significant ternary net interactions are present in the mixture.

On the Properties of Methylbenzoate/n-Hexane Mixed Solvents: A Theoretical and Experimental Study

This paper reports on an experimental and theoretical study of methylbenzoate/n-hexane mixed solvents as a function of pressure and temperature in the whole composition range. We have measured the pressure-volume-temperature (PVT) behavior of these fluids over wide temperature and pressure ranges; from the experimental data, relevant derived coefficients required for the fluids characterization were calculated. The structure of mixed fluids was analyzed from macroscopic data according to excess and mixing properties. The statistical associating fluid theory (SAFT) and perturbed chain (PC)-SAFT molecularly based equations of state were used to predict the PVT behavior with model parameters for pure fluids fitted from correlation of available saturation literature data. The results provided by the PC-SAFT equation of state were clearly superior. Using the fitted PC-SAFT parameters, the global phase behavior of the mixture was predicted, and a type I pattern was inferred according to the van Konynenburg systematic. The molecular level structure was studied through classical molecular dynamics simulations in the NPT ensemble using the optimized potential for liquid simulations (all atom version) (OPLS-AA) force field. Molecular dynamics provides, on one hand, theoretical values of thermophysical properties, which are compared with the experimental ones to check the quality of simulations, and, on the other hand, valuable molecular level structural and dynamic information. Based on both macroscopic and microscopic studies, fluid structure was inferred.