Fractional Distillation of Crude Oil

Crude oil, a fossil fuel, exists as a mixture of various hydrocarbons, compounds generally formed of carbon and hydrogen atoms only.
Fractional distillation is the industrial process used to separate these hydrocarbons in order to produce fuel and other useful substances.
Crude oil is first heated to become a vapour. This process takes place in a distillation tower, where temperature ranges from high at the bottom (approximately 350 degrees Celsius) to low at the top (approximately -170 degrees Celsius).
As the vapour rises, it cools down. Different hydrocarbons condense and are collected at different levels due to their different boiling points, a property influenced by the size and weight of their molecules.
Hydrocarbons with the lowest boiling points such as methane, ethane, propane and butane are collected from the top of the tower. These are used as fuels and in the petrochemical industry.
Hydrocarbons like petrol and naphtha have slightly higher boiling points and thus condense a little lower in the tower. They are used respectively as fuels for vehicles and in the production of chemicals.
Diesel and kerosene have higher boiling points, therefore condense even lower. These are used respectively for car fuel and jet fuel.
Below these, lubricating oils and fuel oils are collected. The former are used in industry for lubrication purposes. Fuel oils are used as fuel in large ships and in power stations.
The residue at the bottom, comprising of hydrocarbons with the highest boiling points, is used to produce bitumen, which gets utilised in road surfacing and roofing.
The principle of fractional distillation is based on the variation in the boiling points of the hydrocarbons due to differences in the strength and number of their intermolecular forces. These forces are greater for larger molecules, hence they require more energy to overcome, leading to higher boiling points.
Fractional distillation thus yields valuable products such as gasoline, diesel, jet fuel, heating oil, and chemicals for plastics and pharmaceuticals. It plays a crucial part in the modern industrial society.