2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16
Phenol is a colorless crystalline substance with a very specific smell. This substance is widely used in the production of various dyes, plastics, various synthetic fibers (mainly nylon). Before the development of the petrochemical industry, phenol production was carried out exclusively from coal tars. Of course, this method was not able to cover all the needs of the rapidly developing industry in phenol, which has now become an important component of almost all the objects around us.
Phenol, the production of which has become an urgent need due to the emergence of an extremely wide range of new materials and substances, of which it is an integral ingredient, is used in the synthesis of phenol-formaldehyde resin. And it, in turn, is an important component of phenolics. Also, a large amount of phenol is processed into cyclohexanol, which is necessary for the manufacture of synthetic fibers in industrialscales.
Another important application of phenol is the production of a mixture of creosols, which is synthesized into creosol formaldehyde resin, used to make many medicines, antiseptics and antioxidants. Therefore, today the production of phenol in large quantities is an important task of petrochemistry. Many methods have already been developed to produce this substance in sufficient volumes. Let's dwell on the main ones.
The oldest and most proven method is the alkali melting method, which is characterized by a large consumption of sulfuric acid for the sulfonation of benzene and caustic, followed by their fusion into benzenesulfonatrium s alt, from which this substance is directly separated. The production of phenol by the method of benzene chlorination followed by saponification of chlorobenzene with sodium hydroxide is profitable only if there is a large amount of cheap electricity needed for the production of caustic and chlorine. The main disadvantages of this technique are the need to create high pressure (at least three hundred atmospheres) and an extremely significant degree of equipment corrosion.
A more modern method is to obtain phenol by decomposition of isopropylbenzene hydroperoxide. True, the scheme for isolating the required substance here is rather complicated, since it involves the preliminary production of hydroperoxide by the method of benzene alkylation with a propylene solution. Further, the technology provides for the oxidation of the resultingisopropylbenzene with an air mixture until hydroperoxide is formed. As a positive factor of this technique, one can note the production of another important substance, acetone, in parallel with phenol.
There is also a method for isolating phenol from coke and semi-coke tars of solid fuel materials. Such a procedure is necessary not only to obtain valuable phenol, but also to improve the quality of various hydrocarbon products. One of the properties of phenol is rapid oxidation, which leads to accelerated aging of the oil and the formation of viscous resinous fractions in it.
But the most modern method and the latest achievement of the petrochemical industry is to obtain phenol from benzene directly by oxidizing it with nitrous oxide. The whole process is carried out in a special adiabatic reactor containing a zeolite-containing catalyst. The initial nitrous oxide is obtained by the oxidation of ammonia with air or by separation from adipic acid. More precisely, from its by-products formed during the synthesis. This technology is capable of producing high-purity phenol with a minimum total content of impurities.
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