Study On Solubility Parameter Of Supercritical Carbon Dioxide By Molecular Dynamics Simulation

The study on thermodynamic properties and intermolecular interactions in supercritical systems is the basic of understanding and predicting specialities of the supercritical fluid, which is important to the development of supercritical fluid technology.The solubility parameter is one of the most useful concepts in the physical chemistry, and it is widely used to explain and predict the thermodynamic behavior of fluid. In order to enhance the soluble ability and improve the solubility and selectivity of solute in supercritical fluid, molecular simulation method was applied to investigate the solubility parameters of supercritical carbon dioxide with and without co-solvent.Firstly, in this paper, the density and solubility parameter of pure carbon dioxide were calculated by molecular dynamics simulation. The relation between solubility parameter and density was studied, and an empirical correlation of solubility parameter was proposed for selecting solvents.Molecular dynamics simulations were performed on supercritical mixtures of methanol in carbon dioxide to obtain the density and solubility parameter. The effects of the methanol concentration, fluid density, pressure, and temperature on the solubility parameter were discussed.The influence of three polar or nonpolar co-solvents, ethanol, acetone, cyclohexane, was studied at concentration of 4.0mol%.The solubility parameter enhancement with these co-solvents is considerable, and the solubility parameter increases in the order ethanol, acetone, cyclohexane. This work will provide a direction in improving the solubility and feasibility of supercritical fluid extraction.