1.10 Fractional distillation
Find out about fractional distillation ; why it is different from simple distillation and how it can be used industrially
Fractional distillation in the laboratory
Fractional distillation is the separation of a mixture into its component parts, or fractions. Chemical compounds are separated by heating them to a temperature at which one or more fractions of the mixture will vaporize.
A fractionating column can be added to a simple distillation apparatus. The column is used to achieve a good separation of one liquid from another.
The column is often packed with glass beads which cause repeated condensation and evaporation. This can give a much purer condensate ( product) than when using simple distillation.
By controlling the temperature carefully the different fractions ( components) in the mixture of liquids can be separated from each other.
The most volatile components of the mixture will be the first to be extracted.
Activity 1. Fractional distillation in industry
Crude oil is a mixture of different hydrocarbons.
Fractional distillation is used to separate crude oil into its different fractions. The fraction with the lowest boiling point (the most volatile) rises to the top of the tower where it is given off as gas.
Activity 2. From thin air
Watch the first 2 minutes 25 seconds of this video.
Answer the following questions:
- what are the main components of air?
- what is the percentage of each component - illustrate this with an appropriate chart
- what are the main processes required for the separation of the components in air?
- explain what liquefaction is. How is it achieved?
- how is liquid air separated into its different fractions?
- explain why this process works . Use the following words: volatile, boiling point , separate, evaporate.
