Fractional distillation is useful for separating a mixture of substances with narrow differences in boiling points, and is the most important step in the refining process. The oil refining process starts with a fractional distillation column.

Fractional distillation

1. heated crude oil enters a tall fractionating column , which is hot at the bottom and gets cooler towards the top.
2. vapours from the oil rise through the column.
3. vapours condense when they become cool enough.
4. liquids are led out of the column at different heights.

Fractional Distillation Process

1. Evaporation. Crude oil is heated until it evaporates. Crude oil vapour is put into a fractionating column at the bottom and rises upwards.
2. Condensation. The temperature is highest at the bottom of the column.
3. Collection. The fractions are collected.

Fractional distillation is the process by which oil refineries separate crude oil into different, more useful hydrocarbon products based on their relative molecular weights in a distillation tower.

Fractional distillation is a process by which components in a chemical mixture are separated into different parts (called fractions) according to their different boiling points. Fractional distillation is used to purify chemicals and to separate mixtures to obtain their components.

Fractional distillation is the separation of a mixture into its component parts, or fractions. Chemical compounds are separated by heating them to a temperature at which one or more fractions of the mixture will vaporize.

(i) The components of the mixture must be miscible with each other. (ii) In case, both the miscible components are liquids, they must differ in their boiling point by more than 25∘C.

Fractional distillation is a method for separating liquids with different boiling points. For example, liquid ethanol can be separated from a mixture of ethanol and water by fractional distillation. When the mixture is heated, one liquid evaporates before the other.

The principle of fractional distillation is that different liquids boil at different temperature. The miscible liquids boil at different temperature and evaporate at different temperature. When the mixture is heated, the liquid with lower boiling point boils and turns into vapours.

Answer

Fractional Distillation: It is a process of separation of a chemical mixture whose components have different boiling points. It is an special type of distillation in which two miscible liquids having different boiling points but closed to each other are separated by fractionating column.

Fractional distillation is a method for separating a liquid from a mixture of two or more liquids. For example, liquid ethanol can be separated from a mixture of ethanol and water by fractional distillation. This method works because the liquids in the mixture have different boiling points.

Tadeo Alderotti

Fractional distillation is the process of taking a chemical mixture and using heat to separate out the various components in that mixture. Essentially, you are able to determine what given component is separated out from the mixture by its boiling point. Remember that boiling point is a physical property.

When the boiling points of the two liquids in the mixture are close, generally a difference of less than 40 degrees Celsius (104 degrees Fahrenheit), fractional distillation is more efficient. Fractional distillation completes several simple distillations in one apparatus.

The more surface area the higher-boiling liquid contacts along the way, the more likely it is to condense back to a liquid and return to the boiling flask. Fractional distillation uses this increased surface area to improve the efficiency of the distillation.

Fractional distillation always endeavors to achieve high purity of the fractions collected. You can improve the purity of the fraction by increasing the surface area of the fractionation column. Remove the fractionation column from the distillation unit and pack the internal space with steel wool.

Fractional distillation is more efficient in separating ideal solutions into their pure components than simple distillation. for solutions that deviate slightly from Raoult’s law, the method can still be applied for complete separation.

Heating further will cause the less volatile liquids to evaporate and distill at higher temperatures. The two main kinds of distillation are simple distillation and fractional distillation, and both are used widely. The condenser leads into a collection flask for the purified liquid. Figure 1.

Simple distillation Fractional distillation Advantages  simpler setup than fractional  faster distillation times  consumes less energy than fractional distillation  much better separation between liquids than simple distillation  can more readily purify complex mixtures than simple distillation Disadvantages  …

We have already said that the simple distillation is less efficient at separating liquids, because there is a smaller surface area inside the column, but it is usually much faster. This means that the fractions obtained are impure, and often contain traces of the other liquids found in the original mixture.

A simple distillation is incapable of significant purification if the boiling points of the components are too close. When the difference in boiling points is less than 100 ˚C, a modification is necessary, namely insertion of a fractionating column between the distilling flask and three-way adapter.

List of Disadvantages of Fractional Distillation

• It can be expensive. On an industrial level, fractional distillation is expensive because it requires large structures, heavy-duty materials, and specialized machinery.
• It comes with operational hazards.
• It can contribute to environmental pollution.

Repeated vaporization and condensation of the mixture allows virtually complete separation of most homogeneous fluid mixtures. The vaporization requires the input of energy. This is the principal disadvantage of distillation: its high energy usage.

Mixtures of liquids whose boiling points are similar (separated by less than 70°C) cannot be separated by a single simple distillation.

Never distill to dryness. The residue left in the distillation flask may contain peroxides, which could ignite or explode after all the liquid has distilled away. Make sure that all joints are secured very tightly.

Distillation is used to separate liquids from nonvolatile solids, as in the separation of alcoholic liquors from fermented materials, or in the separation of two or more liquids having different boiling points, as in the separation of gasoline, kerosene, and lubricating oil from crude oil.

The primary advantage of vacuum distillation is that it allows for distilling heavier materials at lower temperatures than those that would be required at atmospheric pressure, thus avoiding thermal cracking of the components.

A vacuum distillation is used when the boiling point of the compound (or the solvent) is too high (Tb>150 oC) in order to distill the compound (or the solvent off) without significant decomposition. All joints have to fit well to allow for a good vacuum.