Upper Critical Solution Temperatures in Carbon Dioxide–Hydrocarbon Systems

Abstract

Critical solution temperatures of binary mixtures were measured, with particular interest being given to the situation in which one of the components is a gas near its critical temperature. The carbon dioxide-1,2,3,4,-tetrahydronaphthalene (tetralin) and the carbon dioxidedecahydronaphthalene (decalin) systems were studied. Phase diagrams analogous to the carbon dioxide–n-alkane systems (>C13) were observed. Interactions between the strong carbon dioxide quadrapole and the aromatic structure of tetralin or naphthenic structure of decalin were not significant. A 25 wt % benzene + 75 wt % decalincarbon dioxide system gave a continuous vapor-liquid critical locus between the pure component critical points, as did the binary systems carbon dioxide-benzene, carbon dioxide-cyclohexane, carbon dioxide-hexane, and carbon dioxide-1-hexene, in contrast to the unbounded critical loci of CO2-decalin and tetralin. The experimental results tend to support the general conclusion that geometric considerations are dominant in determining the formation of a UCST line in the critical region. © 1975, American Chemical Society. All rights reserved.