What is Extractive Distillation?

Extractive distillation is very similar to regular distillation.  This process is used to separate and purify substances that have a similar boiling point to what they are mixed with.  Distillation generally starts with two substances that have been mixed together being heated to separate the substance with the lower boiling point.  However, when you have two substances with the same, or very similar boiling points, this is nearly impossible without other chemical intervention.  Extractive distillation adds another solvent, called a separation solvent, to the mixture.   

What does the Separation Solvent do?

The separation solvent is added to the chemical mixture/substance in order to alter their boiling points.  Due to the similar boiling points and the low volatility of the chemicals, a third chemical must be added.  The separation solvent interacts with one of the two chemicals and alters its volatility.  This allows the chemical with the higher volatility after this addition to evaporate off first and separate from the other.   

A separation solvent should be non-volatile and have a high boiling point so it doesn’t evaporate out and contaminate the chemical or substance we want to collect.  Additionally, this solvent needs to be able to mix will with the mixture without attaching itself to one of the molecules, thus changing the chemical compound.   

When is Extractive Distillation used?

Extractive distillation needs to be used when two chemicals have similar boiling points and low volatility (reactivity) in order to separate and purify these substances.  This process ensures that the two substances do not evaporate off at the same rate.   

This distillation process is used in many industries.  It produces chemicals with a very high purity, making it ideal for labs and industries that require such high purities.  Extractive distillation is used in medicine production, chemical production, petrochemical industries, and refining industries.   

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