Fractional Distillation of Crude Oil

This lesson explains how crude oil is separated into useful fractions by fractional distillation, as required by the Edexcel GCSE Chemistry specification (1CH0). You need to understand the process, the temperature gradient, why different fractions condense at different heights, and the names and uses of the main fractions.

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Why Separate Crude Oil?

Crude oil in its raw form is not very useful. It is a mixture of hundreds of different hydrocarbons with different chain lengths. To make useful products (fuels, plastics, chemicals), the oil must be separated into groups of hydrocarbons with similar chain lengths and boiling points. Each group is called a fraction.

Because crude oil is a mixture (not a compound), it can be separated by physical methods — specifically, fractional distillation.

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The Process of Fractional Distillation

Fractional distillation takes place in a fractionating column — a tall tower at an oil refinery.

Steps