1. Overview of anthraquinone
(Picture: Structural formula of anthraquinone, remember this structure, we will see it later to.)
See the picture above, which is the structural formula of anthraquinone. Anthraquinone refers to an anthracene compound with a carbonyl group at the C9 and C10 positions. It is a fused-ring organic compound and Called 9,10-anthrone and 9,10-anthraquinone.
In 1835, Laurent oxidized anthracene with nitric acid and prepared anthraquinone for the first time. Anthraquinone derivatives are colored and widely found in nature. Most anthraquinone compounds in natural products contain hydroxyl groups and often exist in a free state or in a glycoside state combined with sugar. For example, the plant dye madder contains alizarin and hydroxyalizarin, which are anthraquinone compounds.
Theoretically, anthraquinone may have 10 isomers. At present, there are only three relatively stable ones: 1,2-anthracene ester, 1,4-anthraquinone and 9,10-anthraquinone. The anthraquinone usually referred to is 9,10-anthraquinone.
Anthraquinone has special reducibility and is reduced to 9,10-dihydroxyanthraquinone sodium salt in an alkaline solution of sodium dithionite (insurance powder). (Therefore, the discharging of anthraquinone dyes is more difficult than that of azo dyes.)
2. The production process of anthraquinones
There are four common production processes for anthraquinone:
1. Anthracene gas-phase catalytic oxidation method
The anthracene oxidation method uses refined anthracene as raw material, air as oxidant, and vanadium pentoxide as catalyst to perform gas-phase catalytic oxidation. The reactor has two types: fixed bed and sulfurized bed.
2. Phthalic anhydride method
Using phthalic anhydride and benzene as raw materials, Aluminum trichloride is used as a catalyst to perform Friedel-Crafts reaction, and then dehydration with concentrated sulfuric acid is used to generate anthraquinone. The phthalic anhydride method is divided into solvent method, ball milling method and gas phase condensation method. Most of China uses the solvent method, which uses excess benzene as the solvent. The raw materials of this method are easily available and can be made from petroleum. It has the advantages of low reaction temperature, simple equipment, and few side reactions. The disadvantages are serious pollution, aluminum trichloride waste acid water is difficult to treat, and the production cost is high. The phthalic anhydride method is used for the synthesis of anthraquinone in China. Raw material consumption quota: phthalic anhydride 768kg/t, pure benzene 700kg/t, sulfuric acid (98%) 1364kg/t, aluminum trichloride 1554kg/t, oleum 1000kg/t.
3. Naphthoquinone method
Using naphthoquinone and butylene Using olefin as raw material and cuprous chloride as catalyst, anthraquinone is obtained after condensation reaction and dehydrogenation. Due to the rapid development of petrochemical industry, a large amount of raw materials butadiene and naphthoquinone used in this method are provided. This method has the advantages of low consumption and less three wastes. In Japan and the United States, the naphthoquinone method has reached a considerable scale and has a promising future. Japan’s Kawasaki Company uses this method to produce.
4. Styrene method
Styrene is first processed into two Polymerization reaction, then oxidation to o-benzoic acid, and then cyclization to synthesize anthraquinone. The advantages of this method are that the raw materials are easily available, there are no pollution problems caused by the aluminum salt wastewater of the phthalic anhydride method, and the product cost is low. However, the reaction conditions are harsh, the technology is complex, and the equipment requirements are high. It is a process studied by BASF in Germany. In addition, Mitsui Chemical Company of Japan obtained a patent for the preparation of anthraquinone using toluene as raw material.
3. Anthraquinone dyes
Anthraquinone disperse dyes, acid dyes, vat dyes , reactive dyes, etc., have developed into dye categories with complete chromatography and good performance. There are more than 400 varieties of anthraquinone dyes, which occupy a very important position in the field of synthetic dyes. The following takes four blue dyes as examples to introduce the bright colors of anthraquinone dyes.
1. Anthraquinone disperse dyes
Anthraquinone disperse dyes have an anthraquinone structure. Disperse dyes. Most of the α-positions on the anthraquinone core are amino or hydroxyl groups. Anthraquinone dyes are poorly soluble in water. The light absorption coefficient is about 10,000 to 25,000, which is 1/2 to 1/3 of azo dyes, so the coloring power on fibers is fundamentally worse than azo dyes.
Advantages:
In the navy blue and black ranges of high-concentration dyeing, anthraquinone dyes are rarely used; but anthraquinone Disperse dyes have bright colors, so they are often used for red, yellow or blue dyeing. Judging from the color structure of anthraquinone disperse dyes, they are not affected by hydrolysis and reduction during dyeing. Therefore, they have good light fastness, good chemical stability, and are easy to use. They still occupy a very important position among disperse dyes. Accounting for about 20%. During dyeing, the formalin condensate of ligninsulfonic acid and β-naphthalenesulfonic acid is used as a dispersant, and is micronized at the same time, dispersed in a water bath, and heat treated together with the fibers.
Disadvantages:
Anthraquinone disperse dyes have a disadvantage that other dyes do not have. They can be absorbed by nitrogen oxides in the atmosphere. It is discolored due to the action of sulfur oxides and sulfur oxides, that is, gas discoloration. This phenomenon is related to the basicity of the α-amino group. To overcome this shortcoming, arylamines can be used instead of alkylamines, and electrophilic groups such as halogen atoms, cyano groups and nitro groups can be introduced, such as the dye C.I. Disperse Blue 27 developed by Eastman Company in the United States.
Representative varieties: C.I. Disperse Blue 56 (2BLN), C.I. Disperse Blue 87 and C.I. Disperse Red 92.
(Picture: The structural formula of Dispersed Blue 2BLN is obviously…�Quinone has four amino groups added)
2. KN-R Brilliant Blue, the representative of anthraquinone-based reactive dyes
See the picture above, the structural formula of C.I.19 reactive blue KN-R. The anthraquinone structure in the dye structure is very obvious.
3. Anthraquinone vat dye represents RSN vat blue:
(Picture: Structural formula of Vat Blue RSN)
Vat Blue RSN (C.I.4 Vat Blue) is the earliest anthraquinone reduction dye. Industrially, 2-aminoanthraquinone is used as raw material and is produced by mixing alkali fusion condensation of potassium hydroxide and sodium hydroxide.
4. Anthraquinone acid dye represents weakly acidic brilliant blue RAW:
(Picture: C.I.80 acid blue RAW structural formula)
Weakly acidic brilliant blue RAW is made from the condensation of 1,4 dihydroxyanthraquinone and mesitylene and then smoke It is obtained by sulfonation of sulfuric acid and salting out. </p
