Crude petroleum oil is a mixture of various solid, liquid and gaseous hydrocarbons.thesehydrocarbon are valuable and have unique uses. Each fraction differs in molecular weight and boiling point range. So, to recover these fractions crude oil is fractionated. Fractional distillation is used to separate a mixture of two or more miscible liquids which boil without decomposition and for which the difference in boiling points is less than 300C.
The fractional distillation apparatus involves fractionating column, condenser, distilling flask, receiver, and heat source.
Fractional Distillation Works
The process starts with taking a mixture of two liquids X and Y of which X is more volatile than B. The mixture is taken in the distilling flask and is heated. The temperature rises slowly and the mixture begins boiling. Vapours will start forming. The vapours formed consists of more volatile component X with a little amount of less volatile component Y.
Vapours start travelling in the fractionating column. Condensation of vapours of the less volatile liquid Y will start before than those of more volatile liquid X. So by the time, the vapours rising in the fractionating column will be more of X and the liquid flowing down will consist of liquid Y.
The process of distillations and condensation is repeated. As a result of successive distillations, the vapours of more volatile component X will reach the top, from where they are taken into the condenser and finally the substance is transferred to a container.