Abstract:
Azeotropes have been always remained the topic of interest due to the challenges they pose
in their separation. Although experimental studies have been done with the infrared spec-
troscopy (IR), Raman spectroscopy, mass spectroscopy (MS), X-ray diffraction, inelastic neu-
tron spectroscopy, nuclear magnetic resonance spectroscopy (NMR), and Fourier-transform
infrared spectroscopy (FT-IR) setups to know the reason behind this unique behavior of
boiling at a constant temperature, these experimental studies can only infer the results
from the data obtained. However, they cannot provide the molecular-level picture of what
happens at the azeotropic point. To study the molecular mechanism and the role of ther-
modynamics in the formation of azeotropes, molecular simulations are the most helpful tool
to explain the macroscopic picture using the microscopic properties of the underlying ener-
getics. This study employs the Metropolis Monte Carlo method to investigate the molecular
structure at azeotropic composition. We have used the united atom-transferable potentials
for phase equilibria (TraPPE-UA) force field to model the methanol/benzene mixture (pos-
itive azeotrope). Various analyses are performed to support the accuracy of the force field.
The temperature-composition phase diagram and azeotropic point have been predicted us-
ing Gibbs ensemble Monte Carlo simulations, with good agreement from experimental data.
Further, the TraPPE-UA force field is implemented in the molecular dynamics software to
study the effect of temperature in the azeotropic formation. The force field’s accuracy for
modeling the methanol/benzene system is checked by comparing the energetics with Monte
Carlo results.
