Application of Fractionation and Extractive Distillation for Separation of Butyl Propionate–Propionic Acid–Butyl Butyrate–Butyric Acid Mixture

A flowsheet for the separation of a butyl propionate–propionic acid–butyl butyrate–butyric acid mixture into individual components was developed. The flowsheet contains a fractionating column and units for extractive distillation of the biazeotropic constituents butyl propionate–propionic acid and butyl butyrate–butyric acid using sulfolane as a separating agent. The mutual arrangement of various isomanifolds was studied in the phase diagrams of the derived separation systems of butyl propionate–propionic acid–sulfolane and butyl butyrate–butyric acid–sulfolane. It was found that their arrangement is favorable for carrying out the extractive distillation process. By analyzing the relative volatility diagrams of the components of the biazeotropic mixtures in the presence of sulfolane, the ratio of the amounts of the separating agent and the initial mixture that is required to implement the separation was selected. The operating parameters of the columns of the flowsheet were determined, ensuring the purity (mole fraction) of individual components of at least 0.9950 at minimum energy consumption in the reboilers of the columns.