3.8.2

Fractional Distillation

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Fractional Distillation

Fractional distillation is the process of separating crude oil into groups of hydrocarbons with similar numbers of carbon atoms. We call these groups of hydrocarbons “fractions”.

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Long-chain hydrocarbons

  • Hydrocarbons with lots of carbon atoms are called ‘long-chain hydrocarbons’.
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Short-chain hydrocarbons

  • Hydrocarbons with few carbon atoms are called 'short-chain hydrocarbons'.

The Process of Fractional Distillation

Different-sized hydrocarbons have different boiling points. Fractional distillation separates hydrocarbons using their different boiling points. The steps of the process are:

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Evaporation

  • Crude oil is heated until it evaporates.
  • Crude oil vapour is put into a fractionating column at the bottom and rises upwards.
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Condensation

  • The temperature is highest at the bottom of the column. Long-chain hydrocarbons condense at the bottom and are collected as liquids.
  • Short-chain hydrocarbons have lower boiling points. They pass up the column and condense at lower temperatures nearer the top.
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Collection

  • The fractions are collected. They are then processed to create end products:
    • Fuels (e.g. petrol, diesel) are a common end product.
    • The petrochemical industry can use some fractions as feedstock (material used in an industrial process) to make solvents, lubricants, detergents etc.

Jump to other topics

1Structure - Models of the Particulate of Matter

2Structure - Models of Bonding & Structure

3Structure - Classification of Matter

3.1The Periodic Table: Classification of Elements

3.2Periodic Trends

3.3Group 1 Alkali Metals

3.4Halogens

3.5Noble gases, group 18

3.6Functional Groups: Classification of Organic

3.7Functional Group Chemistry

3.8Alkanes

3.9Alcohols

3.10Halogenoalkanes

4Reactivity - What Drives Chemical Reaction?

5Reactivity - How Much, How Fast & How Far?

6Reactivity - The Mechanisms of Chemical Change

7Measurement, Data Processing & Analysis

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