Refining is a chemical process. So to really understand how it works we need to know a little basic chemistry.
Crude oil is mainly made up of hydrocarbons – chains of carbon atoms and hydrogen atoms. The chemical bonds that link these chains together can be broken up and linked in different ways. In fact, the hydrocarbon compound is the most versatile on the chemical charts. It can make an estimated 2.5 million possible combinations. Longer, heavier molecules can be transformed into lighter ones and vice versa.
But crude oil is far from pure. It can also contain substances that need to be removed because they would damage an engine or other machinery. In the refinery, we remove sulphur, nitrogen, oxygen, water and other trace substances and then dispose of them safely.
 
Vaporizing the crude oil
The first step in separating oil into useful products involves heating it to a about 350˚ Celsius. It is then pumped into a fractioning tower.
If you have ever seen an oil refinery from a distance, these are the tall, slender towers that jut up above the horizon. The vaporized oil rises up the tower through trays with holes in them. As the gas cools, its components condense back into several distinct liquids. Lighter liquids like kerosene and naptha, a product used in chemicals processing, collect near the top of the tower, while heavier ones like lubricants and waxes fall through weirs to trays at the bottom.

Demand for gasoline is high, so we use the flexibility of the hydrocarbon compound to turn some of the heavier components from the fractioning tower into gasoline. Reforming and alkylation are two such processes. Cracking is another. It breaks large hydrocarbon molecules down into smaller ones, making the end product runnier. It’s a process developed by  heritage company Amoco, and it’s standard practice for oil companies today.