Vapor-Liquid Equilibrium and Critical Line of the CO₂ + Xe System. Critical Behavior of CO₂ + Xe versus CO₂ + n-Alkanes

An acoustic technique was applied to investigate the binary critical behavior of the system CO₂ + Xe. The critical line of this binary system exhibits a temperature minimum, suggesting the existence of azeotropic behavior. The compositions of the studied mixtures were chosen in order to define the minimum temperature locus (p = 6.04 MPa, T = 282.34 K and at x(CO₂) = 0.3622). The results were correlated with the Peng-Robinson equation of state using conventional mixing and combining rules. Additionally, the same equation was used to correlate published data on CO₂ with the five lower normal alkanes. The adjustable interaction energy and size parameters for CO₂ + Xe are in line with those from CO₂ + C₂H₆ up to CO₂ + C₅H₁₂, while those for CO₂ + CH₄ deviate significantly.