Measurements and Modeling of Volumetric and Phase Behavior of Carbon Dioxide + Higher Alkanes: CO₂ + n -Pentadecane at Temperatures 313 to 410 K and Pressures up to 77 MPa

Experimental compressed liquid density and bubble pressure of {xCO₂ + (1 - x)C₁₅H₃₂} are reported for x = 0.376, 0.562, and 0.757 at temperatures from 313, 363, and 410 K and pressures from bubble points up to about 77 MPa. Density was measured using a vibrating U-tube driven and scanned in frequency domain by a lock-in amplifier to accurately measure the resonance peak in complex form where density is determined with an expanded uncertainty of U(ρ) = 0.003ρ. The experimental measurements are compared with cubic equations of state of Redlich-Kwong-Soave (RKS), Peng-Robinson 1976 (PR76), and the improved version Peng-Robinson 1978 (PR78) with and without volume translation correction. PR78 EOS gives best predictions with an average deviation of 1.2%. The deviations are maximum near the bubble points and increase in a systematic manner with increasing CO₂ mole fraction x. Bubble pressures were determined from the discontinuity of p-V plots completed during a series of isothermal constant composition expansion processes. Bubble pressures are limited to 353 K in literature but extended in this work to 412 K. No previous data on compressed liquid density of this system available in literature at high pressure.