Crude oil is also a naturally occurring hydrocarbon. Hydrocarbons are molecules that contain hydrogen and carbon and come in various lengths and structures, like rings and straight and branched chains.
Petroleum contains many alkanes and alkenes and has several impurities when removed from underneath the earth. Refining petroleum entails both the removal of these impurities and also the separation of petroleum into its various components. The specific method for this separation in crude oil is known as fractional distillation.
Fractional distillation is carried out by heating the petroleum to 400 °C. As every hydrocarbon in petroleum has it a particular boiling point, by doing so, they will separate out and then be collected. The portion that remains thick at 400 °C falls to the bottom of the tower is removed and forms bitumen or asphalt. The mixture of vapours that enters the fractional distillation tower starts to condense as the temperature cools the higher the gases go.
The vapours with higher boiling points condense first are therefore collected first at the lower levels of the tower. The gases that have lower boiling points condense further up the tower and are collected on the higher levels. Those that do not condense are collected at the peak of the tower. However, fractional distillation creates large hydrocarbon molecules that are not very useful until it is further broken down via a process called cracking. Thermal cracking uses higher temperatures to break the bonds that hold the