Design of Extractive Distillation Considering the Effect of Feed Components on the Separation of Multiazeotropic Systems

Abstract

Extractive distillation in separating multiazeotropic systems is generally considered a challenge due to the difficulty in finding entrainers that can simultaneously alter multiple azeotropic points. This study proposes a method that leverages intermolecular forces between nonkey components (autoextractive components) and key components. This allows for the separation of an n component mixture into n–1 components or fewer, along with at least one pure component, without the need for additional entrainers. The operating condition for the autoextractive effect is explicitly defined as when the ratio of the autoextractive component to its azeotropic component exceeds the ratio of its azeotropic composition, enabling the separation of the third component without the need for additional autoextractive components. Using the example of the ternary azeotropic system ethyl acetate (A)–ethanol (B)–toluene (C), this study details how to achieve the separation of azeotropic mixtures through the autoextractive effect and entrainer (E). Two novel separation sequences, C/B/A/E and C/A/B/E, have been developed based on the autoextractive effect. These sequences are more readily accepted when the ratio of the autoextractive component to its azeotropic component exceeds its azeotropic composition in the feed.