What is the process used to separate petroleum into different fractions?
The process is called fractional distillation.
Fractional distillation is the use of distillation to separate a liquid mixture into different parts (fractions) that differ in boiling point.
The substances in crude oil have different boiling points, so they can be separated by fractional distillation.
The crude oil is heated to about 600 °C, and its vapours are allowed to condense at different temperatures in the fractionating column.
The temperatures in the column range from about 600 °C at the bottom to 20 °C at the top.
Substances with high boiling points condense at the bottom, while those with low boiling points condense at the top.
Each fraction contains hydrocarbon molecules with a similar number of carbon atoms.