Azeotropes are mixtures of two or more liquids whose proportions cannot be changed by simple distillation. Generally, mixtures have varied boiling points and can be separated at different temperatures. But the vapors of azeotropic mixtures have the same proportions of constituents as in the liquid state. In this article, we discuss the definition, types, and distillation of azeotropic mixtures.
Definition of Azeotrope
An azeotrope is a mixture of liquids that cannot be separated by simple distillation. The constituents of the liquid are at a fixed proportion. When heating the proportion of the vapor is the same as in the liquid state. An azeotrope is also known as a constant boiling point mixture. The most famous example of an azeotropic mixture is a mixture of ethanol/water. An azeotropic mixture can be separated by many methods like azeotropic distillation, extractive distillation, and, pressure swing distillation.
Type of azeotrope mixture
1. Heterogenous and homogenous mixtures
If the constituents of a mixture are not completely miscible but still they form an azeotrope, then they are called a heterogenous azeotrope mixture. If the azeotrope is completely miscible then they are termed homogeneous azeotropes.
2. Positive and negative azeotropes
The azeotropic mixture has a higher boiling point than its constituents and is termed a positive azeotrope. An azeotropic mixture with a lesser boiling point than its constitutions is termed as a negative azeotrope.
3. Binary and ternary Azeotropes
Binary azeotropes are azeotropes that consist of two constitutions with a fixed proportion in the liquid and vapor phases. Ternary azeotropes consist of three constitutions.
What is azeotropic distillation?
Generally, in chemistry, azeotropic distillation is any method used to break an azeotrope in distillation. In chemical engineering, azeotropic distillation usually refers to the specific technique of adding another component to generate a new, lower boiling azeotrope that is heterogeneous.
Research
You can read this article titled “Assessment of extraction options for a next-generation biofuel: Recovery of bio-isobutanol from aqueous solutions” on the separation of a water + isobutanol azeotrope.
In this article titled “Design Optimization of Deep Eutectic Solvent Composition and Separation Performance of Cyclohexane and Benzene Mixtures with Extractive Distillation,” you can see how authors have designed a system with entainers for a Design Optimization of Deep Eutectic Solvent Composition and Separation Performance of Cyclohexane and Benzene Mixtures with entainers for the extractive distillation of organic/inorganic mixture.
You can read this about the technique of chemical looping for the separation of azeotropic mixtures in this article titled “Application of the Chemical-Looping Concept for Azoetrope Separation“.
Application of the Chemical-Looping Concept for Azoetrope Separation, Engineering, Volume 7, Issue 1, 2021,
Pages 84-93, ISSN 2095-8099, https://doi.org/10.1016/j.eng.2020.06.022.(https://www.sciencedirect.com/science/article/pii/S2095809920303283)
This article shows how an azeotropic mixture of “Cyclopentyl methyl ether and 2-methyl tetrahydrofuran” is employed as a solvent in chemical synthesis reactions.
