Partial Molar Volumes Of Solutes And Molecular Simulation Of Molecular Interaction In Binary Mixed CO₂--Cosolvent Supercritical Fluids

In the recent years, supercritical fluid CO2 as new and green technology is more and more recognized by many chemists and engineers. But the basic research on the application aspects of SCF-CO2 is very lack, which embarrasses more development and industry applying. In this dissertation, the molecular interaction and the solution structure were explored primarily based on the experiment data and molecular simulation. This basic research is armed to find out and to predict SCF particularity, which are very important for the SCF application.Firstly the densities of the binary mixtures of CO2—methanol, CO2—ethanol, CO2—n— butyraldehyde and CO2—i—butyraldehyde were measured from 313.5K to 323.5K under the pressure range from 7 to 14MPa. The partial molar volumes of the solutes were calculated based on the relationship between the concentrations of the solutes and the densities of the mixtures﹒Intermolecular interaction between CO2 and the solutes was studied based on the partial molar volume data. The partial molar volumes of the solutes were negative and the absolute value decreases with increasing pressure and the concentration of the cosolvent. Moreover, the partial molar volumes of the solutes related with molecule size and space structure of the cosolvent.Based on experiment data, molecular dynamics simulation techniques were used to study the radial distribution function (RDF) in supercritical binary mixtures. Through figs of RDF, we can know that the CO2 part densities around solute are more than the whole densities and CO2 molecular congregates around solute molecular. We also know the microscopic structure of supercritical binary mixtures.Comparing experiment data with molecular simulation, we think there is strong molecular interaction between solute molecular and solvent molecular around critical point.