Fractional distillation of crude oil

Each hydrocarbon that can be present in crude oil has a different boiling point, meaning they can be separated by fractional distillation. In fractional distillation crude oil is separated into fractions. Fractions contain hydrocarbons with a similar number of carbon atoms.

This is how it works:

  1. The crude oil is heated to a very high temperature. This causes it to boil, making all the hydrocarbons evaporate and turn into a gas.

  2. The crude oil vapour is fed into the fractional distillation column, which is hotter at the bottom and cooler at the top. The vapours rise up the column.

  3. When each hydrocarbon reaches their boiling point in the column, they will condense and turn back into a liquid. The liquid fractions are then removed.

Long chain hydrocarbons will be removed from the bottom of the column as they have very high boiling points.

Short chain will be removed from the top of the column as gases as they will not condense (low boiling points.)

Some things that use these fractions of hydrocarbons as fuel include:

  • Petrol and diesel

  • Heavy fuel oil

  • Kerosene

  • Liquified petroleum gas

Some things that use these fractions as feedstock include:

  • Solvents

  • Lubricants

  • Detergents

  • Polymers

(Feedstock is a chemical that is used to make other chemicals)