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Sometimes oil can be distilled only a small percentage of gasoline. To increase this percentage is used for the distillation process secondary or cracking.
The cracking is to break or decompose high molecular weight hydrocarbons (fuels such as gas oil and fuel oil) in the lower molecular weight compounds (gasoline). In the process always form hydrogen and carbon compounds. It is very important in petroleum refineries as a way to increase gasoline production at the expense of heavier products and less valuable, such as kerosene and fuel oil.
There are two types of cracking, the thermal and catalytic. The first is by applying heat and high pressure, the second by the combination of heat and a catalyst.
In this process, the heavier parts of crude oil are heated to high temperatures under pressure. This divides (cracked) large hydrocarbon molecules into smaller molecules, which increases the amount of gasoline (composed of such molecules) produced from a barrel of crude. Used liquid or gaseous light loads, high temperatures (800-900 º C) and low pressures. With the process are derived mainly from naphtha olefins.
In this case the heavy fractions such as gas oil and fuel oil are heated to 500 ° C at pressures of 500 atm. in the presence of auxiliary substances: catalysts that speed up the process. For these catalysts the process takes its name.
The best-known catalytic processes that have supplanted the old far thermal processes include fluidized bed technique and fluid catalytic powder using aluminum-silica gel as catalysts. In the fluidized bed process, oil is passed through a stationary bed of solid particles in the fluid catalytic process, the particles are mobile and are suspended in a stream of oil vapor at a temperature of 450 ° to 540 ° C, and a pressure of 2.4 atmospheres.

The great advantage of cracking can be seen clearly in the following statistics: in 1920, a barrel of crude, which contains 159 liters, 41.5 liters of gasoline produces 20 liters of kerosene, diesel oil and 77 liters and 20 liters of distilled heavier distillates. Today, a barrel of oil produces 79.5 liters of gasoline, 11.5 liters of jet fuel, 34 liters of diesel and distillates, 15 liters of lubricants and 11.5 liters of waste heavier.
This simple statistic shows that thanks to the production of naphtha cracking can increase dramatically.

Major petroleum products

BOILING FRACCIÓNTAMAÑOPUNTO (° C) USOSGasC 1 to C 5 -160 to 30Combustible gaseosoGasolina directaC 5 to C 12 30 200Combustible motorQueroseno, combustóleoC 12 to C 18 180 400Diesel, fuel and hornoLubricantesC 16 más350 Massolo másLubricantesParafinasC 20 and low fusiónVelas , fósforosAsfaltoC 36 and másResiduos gomososSuperficie road
NAFTA: The naphtha is a mixture of hydrocarbons that are refined, partially achieved in the top of the atmospheric distillation tower. Different types of companies and refiners produce gasoline generally two types: light and heavy, in which both are distinguished by the range of distillation which is then used to produce different types of gasoline. The gasoline or petrol is highly flammable so its handling and storage require an extremely careful and special. The naphthas are also used in agricultural areas such as solvents, also has application in the paint industry and the production of specific solvents.

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