TYPES OF DISTILLATION

TYPES OF DISTILLATION :

Different types of distillation include:

• Simple distillation
• Fractional distillation
• Steam distillation
• Vacuum distillation
• Air-sensitive vacuum distillation
• Short path distillation
• Zone distillation

Simple Distillation

The simple distillation process is applied when the boiling points of two liquids are significantly different from each other (a minimum difference of 25-degree centigrade) or to separate liquids from solids or non-volatile components. It involves heating the mixture of liquid to the boiling point and immediately condensing the vapors so formed. The condensed vapor is then collected. Raoult’s law governs the purity of the distillate or the purified liquid.

Fractional Distillation

In fractional distillation, liquids in the mixtures that have similar boiling points are often separated. Several vaporization-condensation steps are involved in fractional distillation, which takes place in a fractioning column. This process is also known as rectification. With every vaporization-condensation cycle, the purity of the distillate improves.

Steam Distillation

Steam distillation is used to separate the components in a mixture that are heat-sensitive. In the beginning, the steam is passed through the mixture to make it slightly heated and vaporize some portion of it. A high heat-transfer rate is seen without requiring high temperatures. The vapors so formed are then condensed to get the necessary distillate. This distillation process is used to obtain essential oils and herbal distillates from several aromatic flowers/herbs.

Vacuum Distillation

For separating liquids that have very high boiling points in mixtures, the Vacuum Distillation is ideal. To boil these compounds, they are not heated to high temperatures, but the pressure of the surroundings is lowered. Due to lower pressure, the component boils at lower temperatures.

Once the component’ vapor pressure is equal to the pressure of the surrounding, it is transformed into a vapor. These vapors are then condensed as well as collected as the distillate. The method of vacuum distillation is also useful to obtain highly purified samples of compounds that decompose at high temperatures.

Air-Sensitive Vacuum Distillation

The vacuum distillation process is usually carried out for compounds that are sensitive to air and readily react with it. However, once the process is complete, the vacuum must be replaced with an inert gas. This process is often referred to as air-sensitive vacuum distillation.

Short Path Distillation

The purification of a small quantity of a compound that is unstable at high temperatures is possible through short path distillation. This process is called a short path because the distillate travels a minimal distance before being collected, and this is done under lowered pressure levels. As the distance traveled by the distillate is very short, this method reduces the wastage along the walls of the apparatus.

Zone Distillation

The zone distillation process involves the partial melting of a substance, and the condensation of the vapors formed to get a pure distillate. This process is usually carried out in a long container with the help of a zone heater.

Various Examples of Distillation

1. The simplest and most common example of distillation is the steam from a kettle, which gets deposited as drops of distilled water on a cold surface.

2. This process is used in the separation of alcoholic liquors from fermented materials for purification of alcohol by separating liquids from non-volatile solids.

3. It is used to separate two or more liquids having different boiling points, as in the case of separation of gasoline, kerosene, and lubricating oil from crude oil in crude oil refining, enabling safe storage and transportation.

4. Making liquefied gases from the air. For example, nitrogen, oxygen, and argon are distilled from the air.

5. The desalination of seawater is done through distillation.

6. Perfumes and flavorings for food are obtained from herbs and plants by distillation.

7. Distilled water is used in lead-acid batteries and low-volume humidifiers.

8. Other industrial uses include the processing of chemical products such as formaldehyde and phenol.