What is the process of fractional distillation in petroleum refining?

Fractional distillation in petroleum refining is the process of separating crude oil into its various components or fractions.

In more detail, crude oil, a mixture of different hydrocarbons, is heated until it vaporises. This vapour is then fed into a fractionating column, a tall tower filled with trays or plates. The column is hotter at the bottom and cooler at the top. As the vapour rises through the column, it cools down. Different components of the crude oil condense at different temperatures, so they separate out on the trays at different levels in the column.

The fractions collected from the bottom of the column are those with higher boiling points, such as bitumen and fuel oil. These are heavy, long-chain hydrocarbons. As we move up the column, the fractions have lower boiling points and are lighter, shorter-chain hydrocarbons. Diesel oil and lubricating oil are collected in the middle of the column, while petrol (gasoline) and refinery gases are collected at the top.

Each fraction has different uses. For example, bitumen is used in road surfacing, fuel oil in ships and power stations, diesel oil in vehicles, lubricating oil in engines, petrol in cars, and refinery gases in heating and cooking.

This process is crucial in the petroleum industry as it allows the valuable components of crude oil to be separated and used in a variety of ways. It's also a great example of how physical properties, such as boiling point, can be used to separate mixtures. Fractional distillation is a key topic in IGCSE Chemistry, and understanding it can help you appreciate the practical applications of the principles you learn.