Method for preparing 3,3'-dichlorobenzidine hydrochloride through rearrangement

A technology of dichlorobenzidine hydrochloride and dichlorohydroazobenzene, which is applied in the field of preparation of 3,3'-dichlorobenzidine hydrochloride, can solve the problem of difficult washing of sulfate radicals and low reaction conversion rate , Sulfate solubility and other problems, to achieve the effect of improving selectivity and conversion rate, easy to stir evenly, and inhibiting side reactions

Inactive Publication Date: 2015-05-13
NINGXIA LANFENG FINE CHEM CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The current method for preparing 3,3'-dichlorobenzidine hydrochloride is to use the organic solvent solution of 2,2'-dichlorohydroazobenzene (abbreviated as DHB) prepared by the existing technology, add hydrochloric acid and sulfuric acid to Formation of row reaction, hydrochloric acid rearrangement method and sulfuric acid rearrangement method have the situation that the material viscosity is high and it is not easy to stir, resulting in long reaction time, high stirring energy consumption, and low reaction conversion rate
Although the viscosity of the sulfuric acid rearrangement method is slightly improved, the product yield is lower than that of the hydrochloric acid rearrangement method due to the high solubility of 3,3'-dichlorobenzidine sulfate in water, and the resulting Add sodium chloride or hydrochloric acid to convert the sulfate into hydrochloride, the process is complicated, and the sulfate in the product is not easy to clean, which affects the quality of the product
U.S. Patent USP5208376 reports, adds alkyl (C 8 ~C 28 ) Polyglycol ether sulfate can partially improve the viscosity of the material, but the viscosity is still high and it is not easy to stir evenly

Method used

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Examples

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Embodiment 2

[0027] A process for preparing 3,3'-dichlorobenzidine hydrochloride, the process steps are as follows:

[0028] (1) Dissolving and cooling: Add 1 times the amount of xylene to the toluene solution of 2,2'-dichlorohydroazobenzene to dissolve, and cool down to 5°C.

[0029] (2) Rearrangement reaction: The materials cooled in the previous step are respectively put into two rearrangement reaction kettles (No. 1 and No. 2 kettles) equipped with hydrogen chloride gas distributors at the lower part, and hydrogen chloride gas is first introduced into No. 1 kettle , when the conversion rate of 2,2'-dichlorohydroazobenzene reaches more than 50%, the hydrogen chloride gas overflowing from the liquid level in the reaction kettle is passed into No. 2 kettle, and the two kettles react simultaneously, and the hydrogen chloride gas is continuously introduced. When the reaction of No. 1 reactor is completed, change to No. 2 reactor to feed hydrogen chloride, put the material of No. 1 reactor t...

Embodiment 3

[0033] A process for preparing 3,3'-dichlorobenzidine hydrochloride, the process steps are as follows:

[0034] (1) Dissolving and cooling: Add 1 times the amount of toluene to the toluene solution of 2,2'-dichlorohydroazobenzene to dissolve, and cool down to 10°C.

[0035] (2) Rearrangement reaction: Continuous reaction is adopted, and three rearrangement reactors form a group, numbered No. 1 kettle, No. 2 kettle, and No. 3 kettle. Hydrogen chloride gas is introduced from No. 1 kettle through the lower gas distributor , the liquid level overflows the hydrogen chloride and passes into the gas distributor at the bottom of the No. 2 kettle, and also passes into the No. 3 kettle. The toluene solution of pre-cooled 2,2'-dichlorohydroazobenzene is continuously added from the No. 3 tank, overflows to the No. 2 tank through the overflow pipe installed on the upper part of the rearrangement tank, and then overflows to the No. 1 tank , and finally overflow discharge. During the p...

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Abstract

The invention discloses a method for preparing 3,3'-dichlorobenzidine hydrochloride through the rearrangement reaction of hydrogen chloride. By using an existing technique, ortho-nitrochlorobenzene is added into an organic solvent and alkaline liquor under the catalysis of a precious metal catalyst and a cocatalyst, and then the obtained object carries out a coupled reduction reaction with hydrogen, so that 2,2'-dichlorohydrazobenzene is obtained; and hydrogen chloride gas is fed into a 2,2'-dichlorohydrazobenzene solution dissolved by using an organic solvent to carry out a rearrangement reaction, so that 3,3'-dichlorobenzidine hydrochloride is obtained. The yield can reach over 95%, the reaction process can be intermittent, semi-continuous and continuous reaction processes, and the method is low in viscosity of reaction process, easy to uniformly stir and low in energy consumption, and has a yield higher than that in a traditional process, therefore, the method has a good industrialization prospect.

Description

technical field [0001] The invention relates to a preparation method of 3,3'-dichlorobenzidine hydrochloride. Background technique [0002] 3,3'-dichlorobenzidine (DCB) hydrochloride (C 12 h 10 C l2 N 2 2HCl) is an important intermediate for the production of dichlorobenzidine series organic pigments. The output of organic pigments prepared with it as the main raw material accounts for about 27% of the total organic pigments, and is widely used in the production of ink, paint, rubber, plastic and other coloring and pigment printing paste and pigment dyeing paste. It is slightly soluble in water, soluble in alcohol, easy to oxidize, relatively stable in dilute hydrochloric acid and other properties. The current method for preparing 3,3'-dichlorobenzidine hydrochloride is to use the organic solvent solution of 2,2'-dichlorohydroazobenzene (abbreviated as DHB) prepared by the existing technology, add hydrochloric acid and sulfuric acid to Both the hydrochloric acid rearra...

Claims

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Application Information

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IPC IPC(8): C07C211/52C07C209/54
Inventor 郑善龙杨长清李占宁
Owner NINGXIA LANFENG FINE CHEM CO LTD
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