Molecular dynamics simulation of the interaction between palmitic acid and high pressure CO ₂

Abstract

In this study, molecular dynamics simulation was used to explore the interaction characteristics of palmitic acid and CO 2 , and the effects of temperature and pressure on the solubility of palmitic acid in CO 2 were investigated. In the range of 293–353 K and 5–30 MPa, the snapshot of palmitic acid distribution in CO 2 shows that the molecular chain of palmitic acid in high-density CO 2 system is more straight and more dispersed than that in low-density CO 2 system. The radial distribution function further clearly shows that the solubility of palmitic acid in CO 2 decreases with the increase of temperature and increases with the increase of pressure, which is consistent with the fatty acid solubility data reported in the literature and the setting rules of supercritical CO 2 extraction process conditions. As the temperature decreases and the pressure increases, the interaction energy between palmitic acid and CO 2 increases, which is conducive to overcoming the intermolecular force of palmitic acid and promoting dissolution. The solubility parameters of palmitic acid and CO 2 can better reflect the trend of palmitic acid solubility changing with temperature and pressure, which can play a guiding role in the determination of process conditions and even the development of new processes.