Steam Distillation

Overview of Steam Distillation

Steam Distillation is a method of separating temperature-dependent substances. It's a particular type of distillation. Explaining in other terms, this is to separate the miscible liquid base according to its volatilities. For example, aromatic compounds. It plays a vital role in certain industrial regions. There is no chemical reaction taking place here. It's a physical process.

At a very high sustained temperature level, few organic compounds can decompose. Often, it is used to separate volatile essential oils from the plant materials. 

Earlier, steam distillation was one of the popular laboratory methods used for the purification of organic compounds. But now, it has been replaced in many such uses by supercritical fluid extraction and vacuum distillation. However, it is more economical and straightforward than those alternatives and remains vital in specific industrial sectors.


Process of Extraction of Essential Oils by Steam Distillation

In general, we use steam distillation to extract the essential oil. Steam distillation applies low-pressure steam to replace the volatile compounds from intact plant material. Besides, steam distillation allows us for temperature control and the amount of steam applied to the plant material.

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Steam distillation is a method by which we can remove oil from plant matter. In the apparatus, a chamber with holes in the bottom is present to enable steam to flow through either fresh or dried herbs.

It consists of a lid that prevents the oil from diffusing into the air when steam is applied. Then, we can collect the water and oil droplets that have undergone consideration. Therefore, the separation of water and oil happens by passing through the filter.


How Does Steam Distillation Work?

Let us discuss the steam distillation working briefly. The majority of the complex organic compounds do not dissolve in water. Alternatively, they create a mixture that can be separated if it is allowed to settle when the water settles down, and the organic compounds float to the top.

The principle of the steam distillation method is that, when the heating of a mixture of two or more immiscible liquids happens, the vapour pressure exerted by the system will be increased. This happens because the sum of the vapor pressures of all the components of the mixture is now combined. This enables elements with high boiling points to evaporate at even lower temperatures by merely allowing them to form a mixture with water.


Steam Distillation Extraction Procedure

Let us discuss the working of steam distillation. In the extraction procedure, steam flows through the organic matter that comprises the separating compounds. The steam is condensed and produces a mixture of both steam and matter.

The mixture is then heated by passing additional steam, which proceeds to flow over the matter, evaporating the mixture. Due to reduced vapour pressure, the necessary organic compounds evaporate as part of the mixture. Moreover, the extraction of the mixture takes place from organic matter.


Principle of Steam Distillation

When a mixture of two liquids that are immiscible (e.g., water and organics) is heated and disturbed, each liquid's surface exerts its own vapour pressure as though another component of the mixture was absent. Here, the specific constituent independently extracts the vapour pressure on its own, and the vapour pressure of the system consequently increases.

The two immiscible liquids tend to boil when the vapour pressure of these liquids exceeds the atmospheric pressure. Most of the organic compounds are insoluble in water. At an absolute temperature, we can purify it because that is below the point at which such compounds decompose.


Advantages of Steam Distillation

Few of the advantages of using Steam Distillation are:

  • This process generates organic solvent-free products

  • There is no need for subsequent steps after the steam distillation process

  • It possesses a large capacity at the industrial scale for processing of oils. 

  • The equipment is quite inexpensive

  • In the steam distillation of essential oils process from steam boiler, it requires very less amount of fuel

  • Majorly, this method is used for oil production on an industrial scale

  • Participates in extracting materials from the body of plants such as stem and roots

  • It is used as an oil steam distillation that possess high boiling points

  • Extraction of essential oils by steam distillation can be done easily


Applications of Steam Distillation

The steam distillation process is used to separate organic compounds that are temperature-sensitive like aromatic substances. It also helps to extract oils from natural products like citrus oil, eucalyptus oil, and more natural substances that are derived from the organic matter. Due to this reason, the steam distillation method is widely used in producing perfumes and cologne, and in the production of a few cooking materials.

Majorly, this method is used for extracting the orange oil on a big range in industries. In addition, the steam distillation application can also be found in the production of petroleum and food product industries used to separate fatty acids from the mixtures.

Steam distillation’s partial modification technique is used for the isolation of dairy flavours from the dairy products.

Crude oil contains a broad range of components where every component is isolated in a stepwise manner in oil refineries using the steam distillation process.

FAQ (Frequently Asked Questions)

1. How Does Steam Distillation Vary from Simple Distillation?

Some important differences between steam distillation and simple or batch or differential distillation are given below:

  1. Batch distillation is processed either with or without reflux. In many cases, it is defined as a process without reflux, but steam distillation must operate with reflux.

  2. Components are miscible in batch distillation, but in steam distillation, those are immiscible in nature.

  3. Batch distillation is a dynamic process whereas steam distillation is a steady-state process

  4. Batch distillation cannot be used to purify high boiling liquids. It is majorly used as test runs for newer products. On the other hand, steam distillation can be used to purify high boiling liquids and to remove volatiles from edible oil. As long as the water exists in the system, the high boiling component evaporates at a temperature less than their Normal Boiling Point (NBP).

  5. The bottleneck of steam distillation is high energy consumption, and the batch distillation is its capacity, time consumption.

2. On Which Principle Does Distillation Work?

Distillation works on the principle of volatility difference of the individual components of the mixture.

The volatility of a component is defined by its capacity for faster conversion to vapour phase.

For instance, if we have a liquid mixture of A and B. Let us assume that A has volatility of x, and B has volatility x + 1.

When this mixture is fed in a distillation column, it is heated first. During this process, B liquid will convert to the vapour phase quite faster than A, since it’s volatility is greater than that of A.

Thus, if you check the composition of the vapour in the system, it will have a higher fraction of B. When this vapour stage is condensed, it will again have a higher fraction of B than that of A.

Hence, this condensed liquid with a higher fraction of B will be separated using the decanter based on the difference in its density. Thus we get the resultant pure A and pure B.