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 298.15K to 348.15K 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. Isothermal VLE phase boundaries were measured via synthetic method. The investigated systems are CO2 +DMSO+ethanol and CO2 +chloroform+methanol. The critical points of each pseudo-binary system were estimated from experimental results. The Peng-Robinson equation with van der Waals one-fluid mixing rules were used in this study.
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