What is Distillation and What is Fractionation? Is there a difference? What is the definition?

Distillation refers to the mass transfer process in which components are separated by taking advantage of the differences in the volatility of components in a liquid mixture. Fractionation is a method of separating a mixture of several volatile components with different boiling points. Distillation is generally to obtain a single component, and fractionation can be done to separate several components with different boiling points, and a fractionation column is required.

The basic principle is the same, it is to use the different boiling points of substances to make the components with low boiling points become gases through heating, so as to achieve the purpose of separation.

In high school, there is not much difference and they are interoperable.

However, there is a difference in distillation, that is, once, generally to remove impurities and purify.

Fractionation, generally for the separation of multiple components.

Distillation: The liquid is heated to the boiling point, the liquid begins to boil and gradually turns into vapor, so that the vapor is cooled by the condensing device, and the liquid is obtained again by condensation. Distillation has the following uses:

Separation of liquid mixtures (separation can only be done effectively if there is a large difference between the boiling points of the mixture components); determination of the boiling point of compounds; Extraction of liquids or solids with low melting points to remove non-volatile impurities; Solvents, or concentrated solutions.

Fractionation: Although distillation is a common method for separating liquid organic matter, its separation efficiency is not high. Sufficient separation can only be achieved if the boiling points of the separated components differ by more than 150 degrees Celsius.

For mixtures with similar boiling points, it is not possible to separate the components in an ordinary distillation, and they can only be gradually separated after multiple distillations in stages. Doing so is cumbersome and wasteful. Therefore, the method of fractional distillation is adopted.

Fractionation is actually the result of boiling vaporized mixtures passing through a fractionation column and heat exchange in the column. The substances with high boiling point in the rising vapor are first condensed back into the distillation flask, and the vapor with low boiling point continues to rise, so that the vapor is cooled by the condensing device, and the liquid is obtained again by condensation, so that the substances with different boiling points are separated.

Difference Between Distillation and Fractionation:

1.The number of distillations is different.

Distillation only performs one vaporization and condensation, and fractionation is a method that uses a fractionation column to vaporize multiple times and condense the process in one operation. Thus, fractionation is actually multiple distillations.

2.The purity of the substances separated is different.

The substances separated by distillation are generally pure, such as distilled water made from natural water.

and from industrial alcohol.

Absolute ethanol is prepared in China.

The substances separated by fractionation are still mixtures with different boiling point ranges. It is more suitable for separating and purifying liquid-organic mixtures with little difference in boiling point.

Principle of fractionation:

Fractionation is carried out with a fractionation column, and after the solvent being fractionated is boiled in the distillation flask, the vapor evaporates from the round-bottom flask into the fractionation column, where it partially condenses into a liquid. The boiling point of this liquid is lower than that of the liquid in the distillation flask due to the higher content of low-boiling components.

When another part of the vapor in the flask rises into the fractionation column, it is heat exchanged with the condensed liquid, causing it to re-boil, while the rising vapor itself is partially condensed, so that a new liquid vapor equilibrium is created, and as a result, the low boiling point component in the vapor increases. As this new vapor rises in the fractionation column, it is condensed into a liquid, and then boiled by heat exchange with the other part of the rising vapor.

As the rising vapor is constantly condensed and evaporated in the fractionation column, each condensation and evaporation increases the low boiling point components of the vapor. Therefore, the ascent of the vapor in the fractionation column is similar to a simple distillation that has been repeated many times, so that the components of the low boiling point in the vapor are gradually increased.

1. The number of distillations.

Distillation is performed only once for vaporization and condensation, and fractionation is a method of using fractionation columns to complete the process of multiple gasification-condensation in a single operation. Thus, fractionation is actually multiple distillations.

2. The purity of the separated substance.

The substances separated by distillation are generally pure, such as distilled water from natural water and absolute ethanol from industrial alcohol;

The substances separated by fractionation are still mixtures with different boiling point ranges. It is more suitable for separating and purifying liquid-organic mixtures with little difference in boiling point.

With the increasing depletion of the first-class industry and the increasing competition in the oil market, how to make full use of limited oil resources and enhance the core competitiveness of enterprises has become the focus and core of the development of China's petroleum industry. In order to promote the sustained and healthy development of the petroleum industry and provide strong support for China's national economy, we must vigorously enhance the development of the petroleum industry, and the stability of the oil industry is the key. In the process of stabilization, it is worth mentioning the process technology of fractionation.

If the mixture is heated to boiling, and the vapor phase and the liquid phase are in close contact for a long time, and the vapor-liquid two phases reach an equilibrium state, and finally the two phases are moved into the separator for separation, this operation is called equilibrium distillation.

Features: It is only partially separated, and cannot meet the separation requirements of high purity.

Scope of application: only for rough separation or as preliminary processing.

I've already brought you the differences between distillation and fractionation, so let's take a look at it with me.

When distilling a mixture with a relatively close boiling point, the vapors of various substances will be evaporated at the same time, but there are more low boiling points, so it is difficult to achieve the purpose of separation and purification, so it has to rely on fractionation.

Distillation is only one vaporization and condensation, and the separated substances are generally purer, such as distilled water made from natural water, purifying and separating liquid organic compounds, while fractionation is to be continuously vaporized and condensed for many times, and the separated substances are still mixtures, but the boiling point range is different, for example, multiple fractions with different boiling points can be obtained after atmospheric and vacuum fractionation of petroleum, which is suitable for the separation of more liquids.

Distilled water refers to water that has undergone distillation and condensation operations. Generally speaking, water in nature is impure, it may contain a variety of salts, organic matter, dissolved gases, microorganisms and suspended solids, etc., and the non-volatile components can be removed by distillation. Distilled water can also be divided into heavy distilled water and triple distilled water.

Dry distillation is a processing method that strengthens the heat of wood and coal to decompose it under the condition of isolating the air. After dry distillation, the composition and aggregation state of the raw material will change, and the product will be solid, gaseous and liquid. Dry distillation of wood can obtain charcoal, wood tar and wood gas; For coal dry distillation, coke, coal tar, crude ammonia, and coke oven gas can be obtained.

The process of dry distillation is a chemical process.

1.Distillation

The process of heating a liquid mixture to boiling it into vapor and then condensing it into a liquid.

Distillation is one of the most commonly used methods for separating and purifying liquid organic compounds. It can also be used as a method to identify organic matter and judge the purity of substances.

2.The basic principle of fractional distillation is similar to that of distillation. The difference is that there is an additional fractionation column on the device, and the process of using the fractionation column to make the vapor state and cold the condensation is improved from one time to many times.

To put it simply, fractionation is the distillation of multiple times.

3.Distillation and fractionation are both important methods for separating and purifying liquid organic compounds. Distillation is mainly used to separate two or more liquid mixtures with large boiling points (at least 30 or more), while fractionation is to separate and purify liquid mixtures with small differences in boiling points, and now the most sophisticated fractionation equipment has been able to separate mixtures with a difference in boiling point of 1 2.

Fractionation has been widely used in laboratories and in the chemical industry.

First, the principle is different.

1. Distillation principle: use the difference in the volatility of each component in the liquid mixture to partially vaporize the liquid mixture, and then condense the vapor part, so as to realize the separation of its components. It is a unit operation that falls under the mass transfer separation.

It is widely used in petroleum refining, chemical industry, light industry and other fields. The principle is based on the example of separating a mixture of two components. The volatile components were enriched in steam, and the non-volatile components were enriched in the remaining liquid, which realized the separation of the two components to a certain extent.

2. Principle of fractionation: Fractionation column is used for fractionation, and after the solvent to be fractionated is boiled in the distillation flask, the steam evaporates from the round bottom flask into the fractionation column and condenses the liquid in the fractionation column. Due to the high content of low-boiling components, the boiling point of the liquid is lower than that of the liquid in the distillation flask.

When another part of the steam in the distillation flask rises to the fractionation column, it exchanges heat with the condensate to boil it again, while the rising steam itself partially condenses. As a result, a new liquid-vapor equilibrium is created, resulting in an increase in the low-boiling component of the steam.

Second, the device is different.

1. Distillation device: distillation flask (with branch pipe), thermometer, condenser tube, horn tube, alcohol lamp, asbestos net, iron frame, branch Erlenmeyer flask, rubber stopper.

2. Fractionation device: gas lamp, fractionation column, asbestos net, tripod, round bottom flask, condenser tube, horn tube (liquid receiver), Erlenmeyer flask, thermometer.