7.1.2 Fractional Distillation and Petrochemicals

Crude oil is a complex mixture containing a wide range of hydrocarbon compounds. To separate these hydrocarbons into useful fractions, a process called fractional distillation is employed. Fractional distillation takes advantage of the differences in boiling points of the hydrocarbons to separate them based on their molecular size.

During fractional distillation, crude oil is heated in a fractionating column, which is a tall vertical tower. The column is hot at the bottom and cool at the top. As the crude oil is heated, it evaporates and rises up the column. The column is equipped with several trays or plates at different heights. As the vapour ascends, the temperature gradually decreases. This causes the vapour to condense at different heights based on the boiling points of the different hydrocarbons.

The condensed hydrocarbons are collected at different levels of the fractionating column, creating distinct fractions. Each fraction contains hydrocarbon molecules with a similar number of carbon atoms. The fractions include gases, gasoline, naphtha, kerosene, diesel oil, lubricating oil, and residue such as bitumen.

These fractions can be further processed to produce various fuels and feedstock for the petrochemical industry. Fuels such as petrol (gasoline), diesel oil, kerosene, heavy fuel oil, and liquefied petroleum gases (LPG) are essential for transportation, heating, and energy generation.

Additionally, the petrochemical industry plays a vital role in producing a wide range of materials that are integral to modern life. Petrochemicals are chemical compounds derived from petroleum or natural gas. The industry utilises fractions from crude oil to produce solvents, lubricants, polymers (plastics and synthetic fibres), detergents, fertilisers, and many other products.

The ability of carbon atoms to form families of similar compounds leads to the vast array of natural and synthetic carbon-based materials. Carbon atoms can bond with each other and other elements in various ways, giving rise to the diversity of organic compounds that are crucial for our daily lives.