What is the Difference Between Azeotropic and Extractive Distillation?

Azeotropic and extractive distillation are two types of distillation processes used for the separation of components from a mixture. The key difference between the two lies in the formation of an azeotrope:

• Azeotropic Distillation: In this process, the formation of an azeotrope is required to separate the components of a mixture. An azeotrope is a mixture of components having a constant boiling point. Azeotropic distillation is used to break the azeotropes by adding another component to form a new azeotrope with lower boiling points.
• Extractive Distillation: In contrast, extractive distillation does not involve the formation of an azeotrope. Instead, a third component is added to a binary mixture, which can affect the volatility of the existing components. This process involves at least two columns, one for the fresh feed and another for the solvent recovery process.

While both processes involve the addition of components to a mixture for separation, azeotropic distillation forms a new azeotrope, whereas extractive distillation does not. Extractive distillation is often considered a preferable and easier method than azeotropic distillation due to the absence of two liquid phases (organic and aqueous) normally present in azeotropic distillation.

Comparative Table: Azeotropic vs Extractive Distillation

Here is a table comparing the key differences between azeotropic and extractive distillation:

In azeotropic distillation, an entrainer is added to the mixture to form a new azeotrope, which is a mixture that boils at a constant temperature and has a composition different from the original components. This process is used when dealing with components that have similar boiling points.

In extractive distillation, a solvent is added to the mixture to facilitate the separation of components with similar boiling points. The added solvent forms a separate liquid phase with one of the components and alters the relative volatility of the components, resulting in improved separation.