10 Advantages and Disadvantages of Fractional Distillation

 Distillation is the process in which two or more compounds are separated based on their boiling points. The compound with a lower boiling point vaporizes first allowing it to be separated from the compound having a higher boiling point.

What is distillation?

During distillation, the mixture is placed in a container, and the two components of the mixture get separated into different containers. The condensed vapor is called the condensate or distillate.

What is simple distillation?

Simple distillation involves a single vaporization/condensation cycle. Simple distillation is used to separate compounds with widely differing boiling points where both compounds want to be collected. 

It can also be used to purify a liquid that contain either non-volatile impurities such as salt or very small amount of another liquid with a significant difference in boiling points from the liquid to be purified. If two liquids have a boiling point difference of more than 40-50 C, simple distillation will not be effective at separating them. In this case fractional distillation is a must.

What is fractional distillation?

Fractional distillation is like a series of simple distillations. However, instead of having multiple pots and condensers, the vaporization/condensation cycle occurs in a single distillation column. 

In fractional distillation, vapor rises up the column and condenses. It them re-evaporates, rises up the column and condenses again. With each cycle the vapor becomes enriched in the component with the lower boiling point. In this way, fractional distillation accomplishes in one apparatus what would require several simple distillation setups.

In fractional distillation, fractionating columns are insulated in order to allow multiple vaporization/condensation cycles to occur within a single column. The most volatile component vaporizes first. The vapor then condenses on multiple surfaces in the fractionating column, and the resulting liquid vaporizes again. 

During each step, the vapor becomes more enriched in the more volatile component with the lower boiling point. In this way fractional distillation accomplishes in one apparatus what would have required multiple simple distillation steps.

You can read more about the procedure of fractional distillation here: Procedure of Fractional Distillation.

Advantages and Disadvantages of Fractional Distillation

Advantages of Fractional Distillation

The most important advantages of fractional distillation are:    

1. It requires the least amount of items in the apparatus to perform fractional distillation.
2. The apparatus has a fractionating column which makes separating the two components of a mixture easy.
3. It is highly efficient to perform fractional distillation when separating two components of a mixture.
4. The process of fractional distillation foes not require high boiling point difference between the components of the mixture.
5. Fractional distillation gives better separation of components when compared to other forms of distillation.

We shall look into each of them in detail in the following section.

1. It requires the least amount of items in the apparatus to perform fractional distillation.

The list of apparatuses that are required for the process of fractional distillation are:

• Condenser
• Distilling flask
• Fractionating column
• Thermometer
• Heat source such as a Bunsen burner

With these items one can easily perform fractional distillation.

Procuring them also isn't that difficult. They are easily available in hardware shops.

 
2. The apparatus has a fractionating column which makes separating the two components of a mixture easy.

The fractionating column which is an integral part of the fractional distillation apparatus helps in bringing about a better separation between the two liquids that are being distilled. It is placed between the condenser and the flask.

Advantages of Fractionating column

The advantages of fractionating column are:

• They help to separate mixture by allowing the mixed vapors to cool, and be be collected later.
• They can help separate compounds that have relative close boiling points.
• They can also separate compounds based on their property of adsorption, absorption, size etc.
• The more the number of channels better is the separation. Type of packing material also influences this.

3. It is highly efficient to perform fractional distillation when separating two components of a mixture.

There is one question which arises in the mind.

Is fractional distillation more efficient than simple?

Yes, fractional distillation is more efficient that simple. It is so because fractional distillation gives a distillate which is purer than the distillate formed by using simple distillation.

Performing fractional distillation when separating two components of a mixture when the temperature difference between the boiling points of the two are less than 40 degree Celsius is the most efficient. 

Fractional distillation apparatus performs multiple simple distillations cycles and it all automated. For solutions that deviate slightly from Raoult's law the process of fractional distillation is applied for complete separation. 

Fractional distillation separates solutions that have a minimum or maximum boiling points into pure components and azeotropic mixtures. 

4. The process of fractional distillation does not require high boiling point difference between the components of the mixture.

For the process of fractional distillation the temperature difference between the boiling points of two components of a mixture can be less than 40 degree Celsius, and the process would still take place. This is a very convenient way to separate two liquids. 

5. Fractional distillation gives better separation of components when compared to other forms of distillation.

Fractional distillation is one of the most widely used method of distillation because of the fact that it gives better separation than any other forms of distillations such as simple distillation, steam distillation etc. It is an equilibrium process as the composition of the distillate is constantly changing as the distillation proceeds.

Disadvantages of Fractional Distillation

The most important disadvantages of fractional distillation are:

1. Fractional distillation cannot separate solute and solvent. The mixture needs to be a liquid-liquid solution to be distilled by fractional distillation.
2. It requires complex and expensive distillation columns and reflux for industrial fractional distillation.
3. It takes a lot of time to perform fractional distillation.
4. The process needs to be done multiple times.
5. Operational risks are involved in conduct fractional distillation.

We shall look into each of them in detail in the section below.

1. Fractional Distillation cannot separate solute and solvent. The mixture needs be a liquid-liquid solution to be distilled by fractional distillation.

This section can answer the question what type of mixture can be separated by fractional distillation?

To perform fractional distillation, one cannot choose a mixture which is made up of a solute which is dissolved in a solvent. This is because the apparatus is meant to separate only two liquid mixtures. It is unable to separate a solid particles. The apparatus just isn't made for that.

2. It requires complex and expensive equipment like distillation columns and reflux for industrial fractional distillation.

In oil refineries, large distillation towers are used. They cost a lot and get damaged very often due to the heat they are exposed to. They also use reflux which helps in achieving better separation.

3. It requires a lot of time to perform fractional distillation.

It takes a lot of time to perform fractional distillation because fractional distillation repeats the process of simple distillation multiple times until complete separation of the components is achieved. 

4. The process needs to be done multiple times. The more vaporization-condensation that the mixture goes through, the better is the separation of the components. Multiple vaporization and condensation cycles need to be performed, which consumes more energy.

This is one of the trade offs of using fractional distillation as it is a process in which the process needs to be done multiple times.

As fractional distillation is mostly used in industries, the quantity of components that needs to be separated is always higher. Because of that more energy is required to separate such a large amount of mixture. 

5. Operational risk is involved in conducting fractional distillation.

Fractional distillation deals with high pressure and temperatures, therefore it is very dangerous and there is always a possibility that an explosion can occur. This may be detrimental for the personnel that conduct the experiment.

You may also want to read:

Uses of Simple Distillation

Advantages and Disadvantages of Simple Distillation