Monte carlo simulation of carboxylic acid phase equilibria

Area of Science:

• Thermodynamics
• Computational Chemistry
• Chemical Engineering

Background:

• Accurate phase equilibrium data is crucial for chemical process design.
• Carboxylic acids are important industrial chemicals with complex phase behavior.
• Molecular simulations offer a route to predict phase equilibria.

Purpose of the Study:

• To generate phase equilibrium data for acetic, propanoic, 2-methylpropanoic, and pentanoic acids.
• To evaluate the TraPPE-UA force field for simulating carboxylic acids.
• To assess the accuracy of predicted pure component and binary mixture properties.

Main Methods:

• Configurational-bias Monte Carlo simulations in the Gibbs ensemble.
• Used the TraPPE-UA force field, extended for carboxylic acids.
• Simulated pure component and binary vapor-liquid equilibrium (VLE) systems.

Main Results:

• Pure component saturated liquid densities showed excellent agreement (MAE < 1.1%).
• Predicted critical temperatures and densities were within 1% of experimental values.
• Binary VLE simulations (x-y data) agreed well with experiments.

Conclusions:

• The TraPPE-UA force field accurately predicts densities and critical properties for carboxylic acids.
• The force field overestimates pure component vapor pressures, impacting binary mixture predictions.
• Further refinement of the TraPPE-UA force field is needed for accurate vapor pressure calculations.