How different chemical compounds are separated from crude oil?

Before knowing how to separate crude oil, we must know what actually is crude oil composed of. It is a mixture of comparatively volatile liquid hydrocarbons, though it even contains some nitrogen, sulfur, and oxygen. It occurs underground and can contain natural gas, kept in solution by the pressure at varying depths.


Separating the mixture of substances in crude oil into fractions by evaporation and condensation is called fractional distillation. There may be light distillates like Naptha and middle distillates like petrol, Tar, oil, and kerosene. In the end, residues such as heavy fuel oil, waxes, grease, or asphalt are obtained.

Steps of Separation

  • Crude oil is pumped into the bottom of the fractionating tower and heated.

  • The chemical compounds in the crude oil boil and vaporize based on their individual boiling points.

  • Materials with the lowest boiling points rise to the top of the tower as vapor and are collected. While hydrocarbons which are having a high boiling point, such as asphalt and some types of waxes, remain liquid and are drained off through the bottom of the tower as they are the residue in the fractionating tower.

Hence, fractional distillation is the process in order to separate the crude oil into its components.