Modeling of the Interfacial Behavior of Carbon Dioxide + Methyl Myristate, Carbon Dioxide + Palmitate, and Carbon Dioxide + Methyl Myristate + Methyl Palmitate Mixtures Using CPA-EOS and Gradient Theory

This work presents the vapor–liquid equilibrium and the interfacial behavior modeling of binary and ternary CO₂ + ester mixtures, with the cubic plus association equation of state (CPA-EOS) combined with the density gradient theory. The binary mixtures, CO₂ + methyl myristate and CO₂ + methyl palmitate, were studied at temperatures from 313.15 K to 333.15 K, considering the ester molecules as non-associating and the carbon dioxide as non-associating or self-associating (2B scheme) molecule. Phase behavior was predicted with binary interaction parameters adjusted from binary mixture phase equilibrium experimental data. Results show than there are some points better represented by the associating scheme, but the overall trend shows that the CPA-EOS with the non-associating scheme for all the molecules is the best option for describing the phase equilibrium and calculating the interfacial tension for the CO₂ + ester binary mixtures. For this reason, the CO₂ + methyl myristate + methyl palmitate mixture at 313.15 K was modeled only with non-associating fluids. The AAD% for the calculated interfacial tensions, considering non-associating molecules in the mixture is 9.7 % for the CO₂ + methyl myristate mixture, 15.1 % for the CO₂ + methyl palmitate mixture, and 7.9 % for the CO₂ + methyl myristate + methyl palmitate mixture.