A molecular dynamics simulation investigation on the solubility of polycyclic aromatic hydrocarbons in supercritical water

Polycyclic aromatic hydrocarbons (PAHs) are typical chemical pollutants from coal or organic matters. The solubility and conversion of PAHs in water phase are the prerequisite of complete gasification of organic matter or coal and the rate-determining step. This paper is supposed to provide a theoretical basis of restraining coking for ensuring efficient gasification. In this work, molecular dynamics (MD) simulation investigations focused on dissolution of macromolecules including PAHs were summarized and relevant problems were outlined. MD simulations on the solubility of PAH mixtures in supercritical water were carried out for the purpose of illuminating the behaviors of oil droplets containing PAHs under the extreme hydrothermal circumstances. Water densities were ranging from 0.1 g/cm(3) to 0.3 g/cm(3) in this study. The calculation results indicated that the solubility of light PAHs such as naphthalene was complete and thorough in supercritical water, while heavy PAHs such as benzo[ghi]perylene were sensitive to the thermodynamic state of water solvent. As for PAHs mixtures, light PAHs were inclined to be dissolved, while heavy PAHs were more likely to form PAH aggregates. Furthermore, effects of pressure on solubility were not significant. The increase in temperature and density was primarily beneficial to enhance the solubility of PAH mixtures in supercritical water. (C) 2020 Elsevier B.V. All rights reserved.