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 fluid's 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.