Computational investigation of benzene-methanol azeotrope: Insights from Molecular Dynamics and Monte Carlo simulations

Azeotropes, mixtures that exhibit constant boiling points and behave as single substances, pose significant challenges in separation processes and are crucial in various industrial applications such as chemical manufacturing and purification. In this study, we aim to investigate the molecular-level behavior of the benzene-methanol azeotrope, given its extensive applications in various industrial fields. First, we calculated the computational phase diagram using Gibbs Ensemble Monte Carlo (GEMC) simulations and found the azeotropic composition (XBEN = 0.41) in close agreement with the experimental value of 0.39. Several other physical properties, such as density and enthalpy of vaporization, exhibit excellent agreement with experimental values, validating the force field and the approach. Subsequently, we analyzed the liquid-vapor interface using Molecular Dynamics (MD) simulations to investigate the phase coexistence at various temperatures and compositions. Here, we validated the force field by calculating physical properties, such as density and vaporization enthalpy, for both the pure components and the azeotropic mixture. The results showed excellent agreement with experimental values. Liquid-vapor interface analysis reveals that benzene exhibits higher volatility at lower concentrations, whereas methanol becomes more volatile at higher concentrations of benzene or lower concentrations of methanol. Furthermore, it was observed that benzene and methanol reach equal composition at the interface for the azeotropic composition and temperature. This result indicates that, at a specific composition and temperature, the volatilities of both liquids become equal, leading to the simultaneous boiling of both components. The combined approaches of GEMC and MD simulations enabled us to investigate the microscopic details of the azeotropic behavior of the benzene-methanol mixtures