What kinds of dye intermediates can be divided into?

Dye intermediates, also known as intermediates, generally refer to various aromatic derivatives used to produce dyes and organic pigments. They are made by a series of organic synthesis unit processes, and are made of benzene, toluene, naphthalene, anthracene and other aromatic hydrocarbons from coal chemical industry and petrochemical industry. With the development of chemical industry, the application of dye intermediates has been extended to pharmaceutical industry, pesticide industry, fire industry, information recording material industry, additives, surfactants, spices, plastics, synthetic fibers and other production departments. Dye intermediates mainly include four categories: benzene intermediates, toluene intermediates, naphthalene intermediates and anthraquinone system intermediates. In addition, there are some heterocyclic intermediates.

1. Benzene intermediates: benzene can be used to prepare important basic organic intermediates such as benzene sulfonic acid, nitrobenzene, chlorobenzene and nitrochlorobenzene through sulfonation, nitration and chlorination (see halogenation). A series of benzene intermediates with complex structures can be prepared by various organic synthesis unit processes.

2. Toluene intermediates: dye intermediates made from toluene as the basic raw material through a series of organic synthesis units, mainly made from toluene chlorination, toluene sulfonation and toluene nitration. In fact, various toluene intermediates are not only used in dyes, pharmaceuticals, pesticides, additives, coatings, spices, but also in the production of plastics and other polymers.

3. Naphthalene intermediate: it is a dye intermediate made from naphthalene as raw material through a series of organic synthesis units such as sulfonation, nitration, reduction, amination and hydrolysis. This intermediate has naphthalene ring, which contains amino, hydroxyl, sulfonic acid group, etc.

4. Anthraquinone system intermediate: it is a dye intermediate. It is an anthraquinone derivative containing nitro, sulfonic acid, halogen, ammonia, hydroxyl, methyl and carboxyl groups. It is mainly used to produce anthraquinone dyes. This intermediate can be prepared by a series of organic synthesis units, such as nitration, sulfonation, halogenation, reduction and amination. Anthraquinone can be prepared by oxidation of anthracene, but this method is limited by the source of anthracene. In addition, anthraquinone can also be formed by combining phthalic anhydride with benzene in the presence of aluminum trichloride and then cyclizing in concentrated sulfuric acid. With the increasing demand for anthraquinone, new synthetic routes such as naphthoquinone method and styrene method are being developed.