Density and viscosity of liquid mixtures formed by n-hexane, ethanol, and cyclopentyl methyl ether

Abstract

• Experimental data of density and viscosity of liquid mixtures. • Theoretical modeling of density and viscosity of liquid mixtures. • Equilibrium Molecular Dynamics of density and viscosity of liquid mixtures • SAFT VR Mie EoS couple to FVT for ternary mixtures. Experimental determination, theoretical modeling, and molecular simulation have been combined to describe atmospherical density and viscosity for liquid n-hexane, ethanol, and cyclopentyl methyl ether pure compounds as a function of temperature and all the corresponding binary and ternary liquid mixtures at 298.15 K over the whole mole fraction range. Experimental determinations are carried out using a Stabinger viscosimeter. The reported density and viscosity data are modeled with the Statistical Associating Fluid Theory of Variable Range employing a Mie potential (SAFT-VR-Mie) equation of state coupled to the free volume theory (FVT). All-Atom molecular simulations employ equilibrium molecular dynamics (EMD) to obtain the corresponding densities from Isobaric-Isothermal (NPT) ensemble and viscosities from the microcanonical (NVE) and using the Green–Kubo formulation. According to the results, density and viscosity decrease with temperature for pure liquid fluids. For the case of liquid mixtures, densities and viscosities negatively deviate from the corresponding linear trend, and no ternary stationary points are detected under the explored conditions. The experimental data of both properties in binary mixtures are well correlated by a Redlich–Kister polynomial, and the ternary mixture is acceptably correlated by only using binary parameters. From a theoretical perspective, densities of binary and ternary mixtures are excellently predicted from the SAFT-VR-Mie EoS, whereas viscosities of the binary mixtures are well correlated from SAFT-VR-Mie EoS + FVT, while the viscosities of the ternary mixture are well predicted using the same framework. EMD accurately describes the density of pure fluids and mixtures, but it exhibits more significant deviations in viscosity predictions. Moreover, the qualitative viscosity trend with temperature and composition is maintained. Finally, SAFT-VR-Mie and EMD are used to describe the hydrogen bond (HB) network formed within the mixtures at different alcohol compositions, which is also used to validate the selected association scheme. HB formation varies with respect to ethanol concentration, and the results show a negative deviation from compositions linearity, showing good agreement between both approaches.