What is an azeotrope? Definition and characteristics

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Azeotropes have other interesting characteristics that make them mixtures with different uses:

Ideal for flammable compounds: Azeotropes allow you to create mixtures of flammable components with non-flammable components. In this way, the mixture obtained is easier to transport and store. This is essential when transporting highly flammable products, since azeotropic mixtures do not separate naturally. Therefore, they allow the dangerous product to be transported safely.
Easy separation and recovery: Azeotropes can be easily separated and recovered. They are boiled and recycled by distillation.
Modification of mixtures: they allow to change the physical properties of a mixture to obtain other unique ones. This is useful for various applications.

How to separate an azeotrope or azeotropic mixture

There are different methods to separate an azeotropic mixture:

Azeotropic Distillation – It is a fairly efficient method whereby a drag component is added that alters the volatility of the azeotrope component molecules.
Pressure Swing Distillation – This is a common physical method used to break an azeotropic mixture. It consists of varying the distillation pressure to modify the composition of the mixture and to obtain the desired component, avoiding the azeotrope.
Pervaporation – This method is used on miscible liquid mixtures. It is similar to a filter since it includes membranes and through them two liquids are obtained, in which the components of the initial mixture are concentrated. One component passes through a more permeable membrane than the other.

Generally, azeotropes can be:

Compounds with strong hydrogen bonds. For example: amino-alcohols, amino-phenols, oxyacids, polyphenols, amides.
Compounds with weaker hydrogen bonds. Examples: nitromethane, acetonitrile, compounds with active hydrogens and oxygen, nitrogen or fluorine.
Compounds with oxygen, nitrogen, etc., but without active hydrogens. For example: ethers, ketones, aldehydes, esters, tertiary amines, nitroderivatives.
Compounds with active hydrogens, but without nitrogen, oxygen, etc. Examples, Chloroform, methylene chloride, CH ₂ Cl – CH ₂ Cl, etc.
All remaining compounds that cannot form hydrogen bonds. For example: hydroxycarbons, mercaptans, halogen derivatives of hydrocarbons.

Other more specific examples are:

Bea Sánchez, JL Formulation and preparation of mixtures. (2020). Spain. Synthesis.
Álvarez, LX First Steps in Organic Chemistry . (2020). Spain. B087PM7T4H.
Olaya Querevalu, MT; Olaya Zavaleta, YA Organic chemistry: learn easy. (2017). Spain. B076Q71H4R.