Distex equilibria

Extractive distillation is becoming increasingly important as a method for the separation and purification of individual hydrocarbons from petroleum or other hydrocarbon mixtures. This general operation--designated 'Dixtex' by The University of Texas laboratories--involves fractionation in the presence of an added component or solvent. The solvent is chosen for its selectivity, in that the activity (volatility) in one type of compound is changed to a different degree than another, thus permitting separation of close-boiling compounds of different types. Separations are effected by this procedure that are impractical or impossible by conventional fractionation. The solvent controls the liquid-vapor equilibrium of the hydrocarbons, and solution abnormalities of mixtures of aromatic with non-aromatic hydrocarbons (as exhibited by abnormally low relative volatilities and even azeotropes) do not occur. This makes possible the separation of mixtures which the usual distillation process completely fails to resolveChemical Engineerin