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The oil refining process starts with a fractional distillation
column. On the right, you can see several chemical processors that
are described in the next section.
Very few of the components come out of the fractional
distillation column ready for market. Many of them must be
chemically processed to make other fractions. For example, only
40% of distilled crude oil is gasoline; however, gasoline is one of
the major products made by oil companies. Rather than continually
distilling large quantities of crude oil, oil companies chemically
process some other fractions from the distillation column to make
gasoline; this processing increases the yield of gasoline from each
barrel of crude oil.
In the next section, we'll look at how we chemically process
one fraction into another.

Chemical Processing

You can change one fraction into another by one of three
methods:
— breaking large hydrocarbons into smaller pieces
(cracking);
— combining smaller pieces to make larger ones
(unification);
— rearranging various pieces to make desired hydrocarbons
(alteration).

Cracking

Cracking takes large hydrocarbons and breaks them into
smaller ones.
There are several types of cracking:
— Thermal – you heat large hydrocarbons at high
temperatures (sometimes high pressures as well) until they break
apart.

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