Activity coefficients and Distex equilibria of some C₆ and C₇ hydrocarbons in aniline

With the increasing need for large quantities of pure hydrocarbons in recent years, methods of predicting multicomponent vapor-liquid data have assumed increasing importance. Although certain light hydrocarbons are obtained in high purity by fractional distillation of petroleum fractions, the most promising methods of separation involve systems that deviate widely from the ideal solution laws, and the conventional K-charts based on these laws are inapplicable. For example, a method for separation of hydrocarbons into types involves the use of aniline as a solvent, and although the hydrocarbon mixture itself may or may not be an ideal solution, aniline--hydrocarbon mixtures do not approach ideal solutions. In fact, a solvent that forms ideal solutions is of no assistance in this respect. Binary vapor-liquid data must be available before ternary vapor-liquid equilibria of non-ideal systems can be predicted. Activity coefficients (deviations from the ideal law) provide the most convenient means of expressing non-ideality of the solution. The numerical value of an activity coefficient is in fact a quantitative measure of non-ideality. There is at present very little information available on binary-ternary behavior, and there is no satisfactory general correlation of ternary with binary activity coefficients