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Technology for synthesizing and purifying p-toluidine-3-sulfonic acid

A technology of p-toluidine and sulfonic acid, applied in the preparation of sulfonic acid, organic chemistry, etc., can solve the problems of high corrosion, high cost of sulfuric acid, and high cost of solvent consumption, and achieve the effects of low cost, simple method and high product purity

Inactive Publication Date: 2010-06-23
李崇仁
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Since 4B acid is easy to decompose above 100°C, high-purity products cannot be obtained, and the cost of solvent consumption is relatively high
In 1985, DF-3401572 reported the method of preparing high-purity 4B acid by sulfonating fuming acid at 65°C, but there were still disadvantages of high cost and high corrosion due to the need for a large amount of sulfuric acid

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0013] Example 1: 200g of p-toluidine and 200g of concentrated sulfuric acid were heated to 210°C under stirring, reacted for 2 hours, cooled and solidified to obtain 385g of crude product 4B acid. Add 100g of the crude 4B acid above, add 500ml of water and stir, add 32g of sodium carbonate at 35°C to neutralize (PH=8) until the solids are completely dissolved, then add 50g of activated carbon and continue stirring for half an hour, filter the filtrate, and add Add 30g of concentrated sulfuric acid to PH=1, white crystals are precipitated, filter and wash with water to obtain 76g of high-purity 4B acid.

Embodiment 2

[0014] Example 2: 200g of p-toluidine and 200g of concentrated sulfuric acid were heated to 220°C under stirring, reacted for 4 hours, cooled and solidified to obtain 380g of crude 4B acid. Add 100g of the above crude 4B acid, add 500ml of water and stir, add 30g of sodium hydroxide at 50°C to neutralize (PH=7) until all the solids are dissolved, then add 40g of activated carbon and continue stirring for half an hour, filter the filtrate, and stir Add 30g of concentrated sulfuric acid to PH=2, white crystals are precipitated, filtered and washed with water to obtain 80g of high-purity 4B acid.

Embodiment 3

[0015] Example 3: 200g of p-toluidine and 200g of concentrated sulfuric acid were heated to 215°C under stirring, reacted for 5 hours, cooled and solidified to obtain 390g of crude 4B acid. Add 100g of the crude 4B acid above, add 500ml of water and stir, add 30g of potassium bicarbonate to neutralize (PH=9) at 10°C until all the solids are dissolved, then add 40g of activated carbon and continue stirring for half an hour, filter the filtrate, and stir Add 30g of nitric acid to PH=1, white crystals are precipitated, filtered and washed with water to obtain 85g of high-purity 4B acid.

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Abstract

A technology for synthesizing and purifying p-toluidine-3-sulfonic acid comprises the following steps: adding p-toluidine in concentrated sulfuric acid with the same amount, stirring to react for 2-5 hours at 210-220 DEG C, cooling, curing to obtain crude 4B acid; adding the crude 4B acid in water to stir, adding alkali to neutralize at 10-50 DEG C to ensure that the PH value of the neutralized solution is 7-9 and the 4B acid is completely dissolved; in 4B acid solution, adding activated carbon at 10-50 DEG C and stirring for 30-60 minutes to absorb impurities and decolor, filtering to obtain purified aqueous solution of 4B acid, wherein the content of activated carbon is 30-50wt% of the purified 4B acid; and adding acid in the discolored 4B acid under stirring to ensure that the pH value is 1-2 and white crystals are precipitated, filtering, and washing with water to obtain high purity 4B acid. The method has the advantages of easy method, low cost and high product purity.

Description

[0001] Field [0002] The invention belongs to a process for synthesizing and purifying p-toluidine-3-sulfonic acid. technical background [0003] p-Toluidine-3-sulfonic acid (also known as 4B acid) is an important intermediate in organic synthesis, mainly used in the production of brilliant red 6B and Lisol Baohong 7B and other materials. There are many methods for synthesizing 4B acid. The earlier process used p-toluidine and sulfuric acid to produce directly at 210-220°C; in recent years, it was prepared by sulfonation at 75-195°C in a high boiling point solvent. But no matter which method is used, it needs to be purified in an aqueous solution at a higher temperature of about 100 °C. Since 4B acid is easy to decompose above 100°C, high-purity products cannot be obtained, and the solvent consumption cost of the solvent method is relatively high. In 1985, DF-3401572 reported the method of sulfonating fuming acid at 65°C to prepare high-purity 4B acid. However, it still has...

Claims

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Application Information

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IPC IPC(8): C07C309/46C07C303/06
Inventor 李崇仁
Owner 李崇仁
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