Isothermal vapor–liquid equilibria of binary systems of carbon dioxide and 1-butyne, compared to other binary CO2 + C4Hn systems in terms of global parameters

Abstract

Isothermal vapor–liquid equilibria have been measured for binary systems carbon dioxide and 1-butyne at 303, 313, and 333 K. In advance, the accuracy of the experimental method was checked with the binary system carbon dioxide + n-butane in comparison to literature data. The measurements were performed using an analytical method with a recirculation view cell apparatus. The experimental data were correlated with the Peng–Robinson equation of state. The interaction parameters k_ij of the binary systems of carbon dioxide and n-butane, isobutane, 1-butene, and 1,3-butadiene were calculated and compared. The k_ij-values turned out to decrease with increasing degree of unsaturation of the hydrocarbons. The binary mixtures of carbon dioxide with C₄-hydrocarbons were located in a global phase diagram calculated for the Peng–Robinson equation of state for the first time here. The analysis of the global phase diagram shows that the unsaturation of the C₄ molecules has a quantitative effect on the phase behaviour in contrast, for example, to the chain length effect.