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 kij of the binary systems of carbon dioxide and n-butane, isobutane, 1-butene, and 1,3-butadiene were calculated and compared. The kij-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.