Cracking

After going through the stages of distillation, each of the resulting purified fractions (refinery).

Cracking is the decomposition of hydrocarbon molecules are large molecules into smaller hydrocarbon compounds. Examples of this cracking is the processing of diesel oil or kerosene to gasoline.
This process is primarily intended to improve the quality and the acquisition of gasoline fractions (gasoline). The quality of gasoline is determined by the nature of the anti-knock (knock) are expressed in octane number. Numbers given in isooktan 100 octane (2,2,4-trimethyl pentane) which have anti-knocking properties are privileged, and the octane number 0 is given in n-heptane, which have anti-knock properties of the poor. Gasoline is tested to be compared with the mixture and n-heptane isooktana. Octane number is influenced by multiple molecular structure of hydrocarbons.

There are 3 ways cracking process, namely:
a. How to heat (thermal cracking), namely with the use of high temperatures and low pressures.

b. Way catalyst (catalytic cracking), namely with the use of catalysts. The catalyst used is usually SiO2 or Al2O3 bauxite. The reaction of catalytic cracking via carbonium ion cracking mechanism. At first the catalyst due to the acidic proton to molecules olevin appends or interesting hydride ion from alkanes resulting in the formation of carbonium ions:

c. Hidrocracking
Hidrocracking is a combination of cracking and hydrogenation to produce a saturated compound. The reaction was carried out at high pressure. Another advantage of this Hidrocracking is that the sulfur contained in petroleum is converted into hydrogen sulfide which is then separated.