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A method for continuous gradient acidification of DSD acid

A gradient and acidification kettle technology, applied in chemical instruments and methods, preparation of organic compounds, organic chemistry, etc., can solve the problems of unsatisfactory mass production, small DSD acid crystals, low production efficiency, etc., and achieve high speed and high output Improvement, high content effect

Active Publication Date: 2021-11-16
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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  • A 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

A method for continuous gradient acidification of DSD acid, the method uses 2-6 acidification tanks, the feed port of the latter acidification tank is connected to the discharge port of the previous acidification tank, and the pH value of the first-level acidification tank is The set value of the pH value of the final acidification tank is not less than 5.0, the set value of the pH value of the last stage acidification tank is not greater than 3.5, and the set value of the pH value of the latter stage acidification tank is not greater than the set value of the pH value of the previous stage acidification tank; the process is as follows : First, stabilize the temperature of each stage of acidification kettle at 60°C-110°C, and start stirring, then add DSD acid sodium salt solution and inorganic acid to the first stage acidification kettle, and then add additional inorganic acid to the subsequent acidification kettle, so that each stage The pH value of the acidification tank is stable at the set value of the pH value of the acidification tank of this stage, and the solid-liquid mixture flowing out of the last stage of acidification tank is the acidified DSD acid. This method utilizes the method of decreasing the pH value by gradient, not only uses a small amount of DSD acid crystals precipitated in the early stage as seeds, but also provides necessary conditions for the subsequent growth of DSD acid crystals.

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 Patents(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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