fractional distillation

Each hydrocarbon has a different boiling point. Longer chain hydrocarbons have a higher boiling point than shorter chains.

Hydrocarbons in crude oil have to be separated to be useful.

1) crude oil is heated to a very high temperature this causes all of the hydrocarbons to evaporate and turn into a gas

2) crude oil vapour is not fed into the fractional distillation column. Column is hotter at the bottom and cooler at the top.

3) the hydrocarbon vapours now rise up the column.

4) hydrocarbons condense ( turn back into a liquid) when they reach their boiling point.

5) the liquid fractions are then removed.

6) the remaining hydrocarbons continue moving up the column. These now condense when they reach their boiling points.

Very long chain hydrocarbons have high boiling points. These hydrocarbons are removed from the bottom of the column.

Very short chain hydrocarbons have very low boiling points and these do not condense. Removed from the top of the column as gases.

Some fractions are used as fuels e.g petrol and diesel to fuel cars, kerosene to fuel jets, heavy fuel oil to fuel ships and liquidfied petroleum gas.

Some fractions are used as feedstock and feedstock is a chemical used to make other chemicals. E.g solvents, lubricants, detergents and polymers.