Volumetric behavior of water-alcohol mixture at 673.15 K under high pressures. I. Methanol and ethanol solutions

The densities of water-methanol and water-ethanol mixtures were measured at 673.15 K and 25-40 MPa and the excess molar volumes V_m^E and fitted V_m^E were estimated with the Redlich-Kister equation. The concentration dependence of V_m^E gave the positive deviations from the ideal solution at all the experimental conditions. The concerted effects, the dispersion of water molecules around the hydrophobic group of alcohol molecule, and compression effect, may give the maximum around 30-40 mole % of alcohol concentration and 30 MPa for the excess molar volumes at 673.15 K. The comparison V V_m^E between methanol and ethanol aqueous solutions indicated that the magnitude of water?methanol interactions were larger than that of ethanol solutions at 30?35 MPa and 673.15 K. The effect of thermal motions of molecules was significant at 25 MPa and compression effect became dominant at 40 MPa on the volume change of solutions at 673.15 K. This is an abstract of a paper presented at the AIChE Annual Meeting (San Francisco, CA 11/12-17/2006).