Dye Intermediates

They are made from aromatic hydrocarbons such as benzene, toluene, naphthalene and anthracene from coal and petrochemical industries as the basic raw materials through a series of organic synthesis unit processes (see Reaction Processes). With the development of the chemical industry, the scope of application of dye intermediates has been extended to the pharmaceutical industry, pesticide industry, fire and explosives industry, information recording materials industry, as well as auxiliaries, surfactants, spices, plastics, synthetic fibers and other production sectors. There are many varieties of dyestuff intermediates, and the more important ones have several hundred kinds. The most important dyestuff intermediates, such as nitrobenzene, aniline, phenol, chlorobenzene and phthalic anhydride, etc., have been developed into important basic organic intermediates due to their wide use and large dosage, and the annual output of the world is more than one million tons. The most important dye intermediates are o-nitrochlorobenzene, p-nitrochlorobenzene, o-nitrotoluene, p-nitrotoluene, 2-naphthol, anthraquinone, 1-aminoanthraquinone and so on. From the above intermediates, after a series of organic synthesis unit processes, a variety of structurally complex intermediates can be produced.

Dye intermediates mainly include four major categories: benzene intermediates, toluene intermediates, naphthalene intermediates and anthraquinone intermediates, in addition, there are some heterocyclic intermediates. The common reaction processes used in the production of intermediates are nitration, sulfonation, halogenation, reduction, amination, hydrolysis, oxidation, condensation and so on. Synthesis of a complex structure of the intermediates, often through many units of the process, sometimes can be used in different basic raw materials and different synthetic routes. For example, the production of p-nitroaniline, initially with benzene nitration, reduction of aniline, and then acetylation, nitration, hydrolysis of the synthetic route, this method of production process is long, high cost. This method is long and costly. Now it has been changed to the synthetic route of benzene chlorination, nitration, separation of p-nitrochlorobenzene, and then high-pressure ammonia decomposition. Used in the manufacture of dyes, pesticides or pharmaceutical intermediates, usually complex structure, often and the final product supporting the production, production is small, the production of intermittent operation. Widely used intermediates, such as nitrobenzene, aniline, chlorobenzene, phenol, etc., are usually produced in comprehensive large-scale chemical plants, with large yields and continuous operation.