Isothermal vapor-liquid equilibrium measurements and PC-SAFT, PR78, and CPA phase behavior modeling of n-tricosane + SC CO2 mixtures

This study reports the isothermal VLE (PTxy) data of n-tricosane (heavy n-alkane, n-C23H48) in supercritical (SC) CO2 at two selected temperatures of (323 and 343) K over the pressure range from (1.66 to 34.88) MPa. The measurements were made using a high-temperature and high-pressure VLE optical cell. The combined expanded uncertainty of the temperature, pressure, and phase concentration measurements at 0.95 confidence level with a coverage factor of k = 2 is estimated to be 0.2 K, 0.22 %, and 3.5 %, respectively. The measured VLE data has been used to estimate the critical parameters (TC, PC, xC) of the binary n-tricosane + CO2 mixture. The derived L -G critical properties data of the binary n-tricosane + CO2 mixture are: TC = 323.15 K, PC = 34.02 MPa, xC = 0.060 mole fraction of n-tricosane; and TC = 343.15 K, PC = 40.14 MPa, xC = 0.071 mole fraction of n-tricosane. The measured solubility data for the mixture has been used to estimate the physical meaning Krichevskii parameter � partial differential P )infinity TCVC = � 75.93 MPa. Based on the derived Krichevskii parameter the thermodynamic (partial partial differential x molar volumes, V2 infinity , H2 infinity, C infinity P2) and structural (cluster size,N infinity exc) properties of the infinite dilution mixture of n- tricosane + CO2 near the critical point (CP) of pure solvent (CO2) have been calculated. The measured vapor - liquid equilibrium data for n-tricosane + CO2 was modeled using three equations of state (PC-SAFT, PR78, and CPA). The best prediction option with PC-SAFT was obtained with kij = 0.12, while kij = 0 was the best using PR78 and CPA EoS.