Phase equilibria of dimethyl sulfoxide (DMSO) + carbon dioxide, and DMSO + carbon dioxide + water mixtures

This paper reports high-pressure phase equilibrium data on binary mixtures of carbon dioxide with dimethyl sulfoxide (DMSO) and ternary mixtures of DMSO, carbon dioxide and water. The data cover a range of temperatures between 280 and 370 K and pressures up to 15 MPa. Partial liquid miscibility was observed in the binary system DMSO + CO2 at high CO2 concentrations. Vapor–liquid, liquid–liquid and vapor–liquid–liquid equilibrium conditions were measured.The experimental data were modeled with a group-contribution equation of state that takes into account association effects (GCA-EOS). Self-association of water and cross-association between water and DMSO molecules were considered. A molecular group (CH3SOCH3) was used to represent DMSO, the first member of the alkyl-sulfoxide family. Pure group and binary interaction parameters for this new molecular group have been determined. Good correlation and prediction of phase equilibrium conditions were obtained.