Liquid−Liquid Coexistence Curves for Binary Systems: Methanol + Cyclohexane and + Several Isomers of Hexane

Experimental liquid−liquid miscibility temperatures as a function of mole fraction are reported for binary systems formed by methanol as common component with hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, 2,3-dimethylbutane, and cyclohexane. All the studied coexistence curves present an upper critical solution temperature (UCST). The UCST of the binary systems presents a clear dependence with the molecular shape of the hydrocarbons (e.g., the solubility of the alkanes in methanol increases as branching increases in the structural isomers); hence, 2,2-dimethylbutane shows the lowest UCST with methanol. Cyclohexane presents the highest UCST with methanol (i.e., it shows the lowest mutual miscibility for the six studied systems). Values of the UCST have been calculated with the Weimer−Prausnitz modification for polar components of Hildebrand's Regular Solutions Theory. The predicted UCSTs compare well with those obtained experimentally.