Vapor–liquid phase equilibrium of carbon dioxide with mixed solvents of DMSO+ethanol and chloroform+methanol including near critical regions

A visual and volume-variable high-pressure phase equilibrium analyzer was used for measuring the vapor–liquid phase boundaries of the ternary systems containing carbon dioxide and mixed solvents of dimethyl sulfoxide (DMSO) + ethanol or chloroform + methanol at temperatures from 298.15 K to 348.15 K over wide composition ranges including near critical points. Four pseudo-binary systems of carbon dioxide plus mixed solvents with constant molar ratios of DMSO/ethanol = 3/7, 5/5, 7/3, and chloroform/methanol = 1/2, were studied in this work. The critical conditions at each investigated temperature were estimated from the experimental isothermal phase boundaries by interpolation. The Peng–Robinson equation of state with the two-parameter van der Waals mixing rules was applied to calculate the phase boundaries. The experimental values were compared with the predicted results from the Peng–Robinson equation using the binary interaction parameters determined from the vapor–liquid equilibrium data of the constituent binaries. The agreement is reasonably well for carbon dioxide + chloroform + methanol, but obvious overestimations are found near the critical regions of carbon dioxide + DMSO + ethanol, especially at higher temperatures.