Phase equilibria of binary mixtures with alkanes, ketones, and esters based on the Transferable Anisotropic Mie force field

Abstract

The transferable anisotropic Mie potential (TAMie) force field is extended to acetates and formates. Intramolecular bending and torsion potentials were obtained from quantum chemical calculations. The parameters defining the Mie pair potential, representing the van der Waals interactions, as well as point charges were optimized. These force field parameters were optimized based on an objective function that considers vapor pressure and liquid density data of several members of one chemical group simultaneously. Like in earlier work, the parameterization is conducted using an analytic equation of state to locally approximate the objective function, ensuring swift convergence of the optimization problem. Acetates, from ethyl ester to n-pentyl ester, have average errors (AAD) of 0.9–6.9% in vapor pressure and of 0.4–0.7% in liquid densities. Formates, from ethyl formate to n-butyl formate have average errors of 2.0–4.2% in vapor pressure and 0.8–1.1% for liquid densities for reduced temperature ranges of T/Tc=0.56 to 0.96, where Tc is the critical temperature of the considered substance. For a binary mixture of ethyl acetate with n-hexane results of the TAMie force field are found in good agreement to experimental data. Because phase equilibrium data for esters with alkanes is scarce, we also investigate mixtures of ketones with alkanes. For mixtures of butanone with n-hexane and butanone with n-heptane, molecular simulations are in satisfying agreement to experimental data when Berthelot-Lorentz combining rules are employed. After adjusting corrections to the Berthelot combining rules the agreement of molecular simulations to experimental data is very good. Additionally to phase equilibria, we calculated excess properties for the mixture of hexane and butanone, which also show very promising results compared to experimental data.