Study on intermolecular interactions in supercritical fluids by partial molar volume and isothermal compressibility

摘要

The apparent densities of H_2O-CO_2, H_2S-CO_2, H_2-CO_2 binary systems were determined at 308.15 K and different pressures. The concentration of the solutes was 0.3 mol%. The partial molar volumes (PMVs) of the solutes and isotermal compressiblity of mixed fluids were calculated using the experimental data. The PMVs of the two polar solutes (H_2O and H_2S) in supercritical CO_2 are negative, and a minimum can be observed in each PMV versus pressure curve at the pressure where isothermal compressibility ofthe fluid is largest. The absolute value of the minimum of H_2O is smaller than that of H_2S, probably because of the hydrogen bonding between water molecules. However, the PMVs of the two non-polar solutes are positive, and the maximum value of H_2 is larger than that of CH_4. The effect of molecular size and polarity on the intermolecular interactions between solutes and solvents were discussed.