Catalytic cracking of oil

Catalytic cracking of petroleum (in translation from English - splitting) is a technological process aimed at increasing the yield of gasoline by special processing of components of heavy oil fractions. At the primary processing of the product, an average of 5-14% of the total mass of gasoline is obtained. The quality of the resulting fuel after direct distillation does not meet the requirements of modern technology.

Catalytic cracking increases the yield of gasoline and improves its quality.

There are two types of thermal (catalytic) cracking: liquid and gas phase. The first raw material is fuel oil, which is fed into the furnace at 600-625 ° C under a pressure close to atmospheric pressure. Gas phase catalytic cracking is carried out under the same conditions, but the raw material for it is gas oil (solar oils). Thermal cracking in the structure of high-molecular alkanes breaks the carbon bonds and forms molecules of low-molecular carbons included in the gasoline fraction:

C10H22-C5H12 + C5H10.

Thus, two substances (limiting and unsaturated hydrocarbons) with a lower molecular mass are formed from the high-molecular dean .

Catalytic cracking is carried out in the presence of catalysts (activated clay or aluminosilicates) at a temperature of 470-530 degrees under a pressure of 70 to 370 kPa. The main raw material for the process is gas oil, the yield of gasoline from the total mass of oil can reach 30-40%. Therefore, the production of gasoline is a difficult and time-consuming process. To improve the quality of the product, alkenes and alkynes are removed from its composition, which sometimes occupy up to 30% of the total mass.

Thanks to the use of innovative technologies, the output of gasoline in the process of distillation of oil can be up to 80 percent. To assess the quality of liquid fuel use the octane number. Isooctane or 2,2,4-trimethylpentane was chosen as a fuel sample with high antiknock properties.

Its octane number is considered equal to 100. As the sample with the lowest antiknock properties, n-heptane is taken: C7H16, the octane number (OC), which is considered equal to 0. To determine this index, the detonation properties of gasoline with the properties of a mixture of isooctane and n-heptane are compared.

For example, a product with an octane number of 80 has the same detonation properties as a mixture of 80% isooctane and 20% n-heptane. The higher the octane number, the higher the fuel quality. The increase in this indicator saves fuel and saves the power of internal combustion engines. Other components are added to the product, including carbons of synthetic origin, and antiknock agents (these are substances that, in minimum concentrations (no more than 0.5%), improve the anti-knock properties of fuel). Previously, tetraethyl plumbum was used for these purposes. Due to the fact that this substance is very toxic, it was replaced with other antiknock detergents, which are manufactured from manganese compounds. These substances are less toxic to our body and give the possibility of obtaining fuel from the OCH at one hundred and twenty-five to one hundred and thirty units.

Technology of gasoline production

By direct distillation of oil , gasoline is obtained from OCH to 91. This method is an unacceptable luxury for today, since the output of gasoline itself is not very high. To improve the fuel yield and improve its quality, re-distillation, catalytic, thermal cracking, reforming, etc. are used.

The above methods increase the expenditure of labor, time and money, however, only they allow to get less harmful gasoline for the environment. To increase the OCH for today very often use a variety of chemicals (alcohols, organometallic compounds, ethers, etc.).