Preparation of benzene

There are several ways of industrial and laboratory production of benzene, which differ according to which product is selected as the starting material. Modern chemical production as such increasingly uses various aromatic compounds, such as, for example, coke oven gas, obtained during the coking of coal. The coal tar and various fractions formed during the distillation of oil are used quite widely .

Coal coking is the most important technological operation in metallurgy, it is necessary for obtaining coke. It is not necessary to describe in detail all the technology on which the production of benzene is based, it suffices to say that in this case it is formed at the stage when coal is decomposed, and decomposition products are coke and volatile substances, primarily coke gas. In its steams is a coal tar. When this gas passes through a system of capacitors, the substances that make up it are separated. After electrofiltration, the coke oven gas already contains vapors of organic compounds, including benzene. This production of benzene provides its yield in crude form approximately equal to 10-11 kilograms per ton of dry coal.

Coal tar also makes it possible to obtain benzene. The technology here largely resembles the way in which benzene is produced from coke oven gas. The fact is that in itself, coal tar is a complex mixture of various kinds of aromatic organic compounds. Moreover, even to date, the composition of this compound has not been studied to the end, but it has been established that there are more than 500 (!) Components. Processing is technologically a process of two-stage separation of the resin into separate fractions. To do this, each of them is exposed to alkali in order to remove acidic parts. As a result, solid fractions are formed-anthracene and naphthalene, as well as light ones, which also contain benzene.

In the industry, the production of benzene in crude form, the so-called crude benzene, is common. To obtain a pure compound, the crude benzene must be purified from compounds containing sulfur. In this process, two stages are distinguished. At the first stage, the purification of sulfur impurities itself takes place, and the second purified mixtures are separated by rectification. One of the products of this separation will be benzene.

The most important source of various aromatic compounds is oil. That is why modern production of benzols is oriented towards this product.

Benzene is also isolated from acetylene. This substance under normal conditions is a gas, it is colorless, almost insoluble in water, is lighter than air. Among the chemical properties of this gas is the ability to polymerize, and therefore the industry uses the production of benzene from acetylene. This method seems more promising in terms of creating and maintaining the conditions for the chemical reaction. The fact is that acetylene, in itself, is very explosive, therefore its use in industry is associated with the need to observe the strictest technological discipline and the availability of special equipment, especially heat-resistant equipment. At the same time, before obtaining benzene from acetylene, it is sufficient to achieve a temperature of 400 C and conduct it in the presence of graphite. This method was proposed as far back as 1866 by the French chemist M. Berthelot, however, the yield of the substance was extremely small. Therefore, in today's technologies, the use of various catalysts is widely used, which accelerate the course of the reaction, and contribute to an increase in the yield of pure benzene.

In laboratory conditions, benzene, as a rule, is not obtained, but if such a need arises, the method of fusing benzoic acid with alkali is used. The result of this reaction is benzene.