Experimental results on the fluid multiphase behavior of various ternary systems of near-critical carbon dioxide, certain 1-alkanols and o-nitrophenol

Experimental results on fluid multiphase equilibria occurring in a series of ternary systems of carbon dioxide+1-alkanol+o-nitrophenol are presented and discussed. The alkanols considered were 1-octanol, 1-heptanol, 1-hexanol and 1-pentanol. In these mixtures, the critical endpoints of the three-phase equilibria liquid–liquid–vapor were determined experimentally. A comparison of the results obtained in this study was made with previous measurements in a series of ternary mixtures carbon dioxide+1-alkanol+n-tetradecane with, as the alkanol, 1-octanol, 1-heptanol, 1-hexanol and 1-pentanol. In literature, the binary subsystem carbon dioxide+o-nitrophenol has been reported to have type-V fluid phase behavior according to the classification of Van Konynenburg and Scott, whereas the binary subsystem carbon dioxide+1-pentanol has type-IV. The other binary subsystems carbon dioxide+1-alkanol show type-III fluid phase behavior. The transformation of type-V fluid phase behavior into type-IV or type-III suggests that the binary system carbon dioxide+o-nitrophenol actually has type-IV fluid phase behavior instead of type-V.