Cracking is a chemical process in which
hydrocarbon molecules, particularly those
derived from petroleum refining, are
broken down into smaller, economically
important molecules, such as petrol,
but it is also used to produce raw
materials for the chemical industry.
Thermal cracking was first used in 1913,
as the earliest cracking system developed.
It involved distilling batches
of faitly heavy has oil at approx.
500 degrees Celsius, and pressures
up to 25 bar.
Catalytic cracking has been in use
since the 1930s, and eliminated the use for
high pressures, and produced more