Method for continuous gradient acidification of DSD acid

A gradient, acidification kettle technology, applied in chemical instruments and methods, preparation of organic compounds, preparation of sulfonic acid, etc., can solve the problems of inability to meet mass production, small DSD acid crystals, low production efficiency, etc. The effect of fast filtration and high content

Active Publication Date: 2019-10-11
ZHEJIANG HONGDA CHEM
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] However, in the existing process and the improved process, the acidification process is produced in batches, and the acidification is completed in one step. Not only the acidified DSD acid crystals are small, it is difficult to press filter, but also the production efficiency is low, which cannot meet the needs of mass production.

Method used

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  • Method for continuous gradient acidification of DSD acid

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0029] Example 1, using two-stage acidification, that is, using a two-stage acidification kettle, first preheating the DSD acid sodium salt solution to 80 ° C, and protecting it with nitrogen; prepare sulfuric acid, and calibrate the flow meter and pH meter;

[0030] The first-stage acidification kettle, the pH value is set to 5.5: inject 6000LDSD acid sodium salt solution into the 8000L jacketed enamel reaction kettle, turn on stirring and steam, and maintain the temperature at 90±3℃; slowly turn on the sulfuric acid dropwise Valve, adjust the pH value in the kettle to 5.5±0.2; close the sulfuric acid valve, continue to stir for 2 hours, take a sample to observe whether there is agglomeration; if there is, continue to stir until there is no agglomeration; after no agglomeration, open DSD sodium acid at the same time Salt solution and sulfuric acid dripping valve, stabilize the flow of DSD sodium salt solution, and use the pH meter to control the opening of the sulfuric acid dr...

Embodiment 2

[0032] Example 2, using three-stage acidification, that is, using a three-stage acidification kettle, first preheating the DSD acid sodium salt solution to 80 ° C, and protecting it with nitrogen; prepare sulfuric acid, and calibrate the flow meter and pH meter;

[0033] The first-stage acidification kettle, the pH value is set to 5.0: inject 6000LDSD acid sodium salt solution into the 8000L jacketed enamel reaction kettle, turn on stirring and steam, and maintain the temperature at 90±3°C; slowly turn on the sulfuric acid dropwise Valve, adjust the pH value in the kettle to 5.0±0.2; close the sulfuric acid valve, continue to stir for 2 hours, take a sample to observe whether there is agglomeration; if there is, continue to stir until there is no agglomeration; after no agglomeration, open DSD sodium acid at the same time Salt solution and sulfuric acid dripping valve, stabilize the flow of DSD sodium salt solution, and use the pH meter to control the opening of the sulfuric ac...

Embodiment 3

[0036] Example 3, using three-stage acidification, that is, using a three-stage acidification kettle, first preheating the DSD acid sodium salt solution to 70 ° C, and protecting it with nitrogen; prepare sulfuric acid, and calibrate the flow meter and pH meter;

[0037] The first-stage acidification kettle, the pH value is set to 5.0: put 6000LDSD acid sodium salt solution into the 8000L jacketed enamel reaction kettle, turn on stirring and steam, and maintain the temperature at 80±3℃; slowly turn on the sulfuric acid dropwise Valve, adjust the pH value in the kettle to 5.0±0.2; close the sulfuric acid valve, continue to stir for 2 hours, take a sample to observe whether there is agglomeration; if there is, continue to stir until there is no agglomeration; after no agglomeration, open DSD sodium acid at the same time Salt solution and sulfuric acid dripping valve, stabilize the flow of DSD sodium salt solution, and use the pH meter to control the opening of the sulfuric acid d...

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Abstract

Provided is a method for continuous gradient acidification of DSD acid. The method uses 2-6-stage acidification kettles, a feed port of the later-stage acidification kettle is communicated with a discharge port of the former-stage acidification kettle, the set value of the pH value of the first-stage acidification kettle is not smaller than 5.0, the set value of the pH value of the last-stage acidification kettle is not larger than 3.5, and the set value of the pH value of the later-stage acidification kettle is not larger than the set value of the pH value of the former-stage acidification kettle. The process includes the following steps of stabilizing the temperature of each stage of acidification kettle at 60-110 DEG C, starting to conduct stirring, adding a DSD sodium sulfate solutionand inorganic acid into the first-stage acidification kettle, and only adding inorganic acid into the subsequent acidification kettles so that the pH value of each stage of acidification kettle can bestabilized at the set value of the pH value of the stage of acidification kettle to obtain a solid-liquid mixture (the acidified DSD acid) flowing out of the first-stage acidification kettle. By means of the gradient pH value reducing method, a small number of DSD acid crystals separated out in the former period serve as the crystal seeds, necessary conditions are provided for the subsequent DSDacid crystal growth, and the obtained DSD acid is high in press-filtration speed and high in content and contains few impurities.

Description

technical field [0001] The invention relates to the technical field of organic compound synthesis, in particular to a method for continuous gradient acidification of DSD acid. Background technique [0002] The full name of DSD acid is 4,4'-diaminostilbene-2,2'-disulfonic acid, which is an important dye intermediate in the field of fine chemicals and the main raw material for the production of stilbene series optical brighteners; It is also an important intermediate of direct dyes and reactive dyes, and can produce hundreds of varieties such as direct frozen yellow G, direct brilliant yellow 4R, reactive bright yellow KD-3G, and fast orange F3G. The synthesis of DSD acid generally adopts the steps of sulfonation, oxidation, reduction, and acid analysis: the raw material p-nitrotoluene is sulfonated with oleum to obtain p-nitrotoluene o-sulfonic acid, which is oxidized to 4,4' by air under alkaline conditions -Dinitrostilbene-2,2'-sodium disulfonate, reduced by iron powder at...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C07C303/02C07C303/44C07C309/46
CPCC07C303/02C07C303/44C07C309/46
Inventor 李将刘肖晖王国森
Owner ZHEJIANG HONGDA CHEM
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