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Method for preparing p-dihydroxy benzene

A technology of hydroquinone and p-aminophenol, applied in chemical instruments and methods, preparation of organic compounds, organic chemistry, etc., can solve problems such as equipment corrosion, difficulty in selecting equipment materials, harsh conditions, etc., and achieve the goal of increasing production capacity Effect

Active Publication Date: 2009-04-22
JIANGSU YANGNONG CHEM GROUP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0012] The disadvantages of this process are: ① more tar is produced during the reaction process; ② the reaction is carried out under strong acidic conditions up to 250 °C, and the conditions are very harsh; ③ it can be found from the comparison of the two patents of Mitsui Toya Company mentioned above that, The effect of the ratio of p-aminophenol to hydrogen halide on the hydrolysis yield during hydrolysis is far less than that of the hydrolysis temperature on the yield; especially when the temperature is above 240°C, the hydrolysis yield is significantly improved, but it can be found through the inspection of the corrosion manual that the acid There is a turning point in the corrosion of metals between 230-240°C, and most metals are above 240°C, and the corrosion intensifies rapidly, so the corrosion of equipment is serious, and it is difficult to choose suitable equipment materials

Method used

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  • Method for preparing p-dihydroxy benzene
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  • Method for preparing p-dihydroxy benzene

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0044] Hydroquinone preparation method carries out according to the following steps:

[0045] Diazotization reaction: Add 408Kg (0.625Kmol) of 15% sulfuric acid and 27.8Kg (0.25Kmol) of industrial product 98% p-aminophenol into a 1000L reactor, stir and cool down to -5~0°C, add 40% sodium nitrite dropwise 48Kg (0.275Kmol) aqueous solution, adding time for 30-45min, keep warm for 0.5hr after dropping, add 1.5Kg urea, stir for 15min, when the release of nitrogen is not obvious, add 1.5Kg thiourea and stir for another 15min. The dropwise addition, heat preservation and feeding temperature are all kept at -5-5°C to obtain 470-480Kg of dark brown diazonium liquid, which is stored at 0°C.

[0046] Hydrolysis reaction: Add 1000Kg of 30% sulfuric acid to a 2000L reactor, heat to reflux at 106-108°C, add the above diazo solution dropwise at about 0°C for 1-2 hours, then reflux at 102-104°C for 3- 4hr, the temperature was lowered to obtain 1460Kg of light brown hydrolyzate, and the hyd...

Embodiment 2 to Embodiment 7

[0052] The preparation method is the same as in Example 1, except that the concentration of sulfuric acid in the diazotization reaction is different.

[0053]

[0054]

[0055] Increase the diazotization acidity from 10% to more than 30%, the color of the diazonium solution and the hydrolyzed solution becomes darker and darker, and the diazonium salt is easy to precipitate at low temperature, causing unsafe factors.

Embodiment 8 to Embodiment 12

[0057] The preparation method is the same as in Example 1, except that the ratio of hydrolyzed base acid is changed. The composition of sulfuric acid / water (kg / kg) in the bottom acid is ①300 / 700; ②300 / 450; ③150 / 350; ④300 / 450; ⑤300 / 300.

[0058]

[0059] When the hydrolyzed base acid concentration is 30-40%, the change of the base acid composition has little effect on the yield, and the oil layer yield is above 90%; when the base acid concentration is increased to 50%, the yield drops obviously.

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Abstract

The invention relates to a method for preparing hydroquinone (HQ for short), which comprises the following steps: (1) dripping aqueous solution of sodium nitrite into sulphuric acid solution of para-aminophenol to carry out diazotization reaction to obtain dark brown diazonium solution, and using urea, thiourea, thioether, thioalcohol and the like to destroy excessive sodium nitrite; (2) pre-adding dilute sulphuric acid into a reaction kettle, refluxing and dripping the diazonium solution obtained in step (1) to carry out hydrolysis reaction; (3) after extracting hydroquinone from the hydrolyzed solution, using water-phase dilute sulphuric acid in the hydrolysis reaction, and after extracting oil phase and removing solvent, obtaining the crude product of the hydroquinone; and (4) refining the crude product and carrying out post treatment.

Description

technical field [0001] The present invention relates to the preparation method of Hydroquinone (HQ for short). Background technique [0002] Hydroquinone is an important raw material, auxiliary agent and intermediate for rubber, pharmaceuticals, dyes, pesticides and fine chemicals. Catalysts, anti-aging agents for rubber and plastics, monomer polymerization inhibitors, stabilizers and antioxidants for food and paint varnishes, petroleum anticoagulants, etc. In addition, hydroquinone can be further processed into other fine chemical products, such as p-hydroxyanisole, 1,4-diaminoleuco, quinazine, etc. In recent years, the application fields of hydroquinone are gradually expanding. [0003] There are many synthetic methods of hydroquinone, and there are more than 10 kinds so far, among which the aniline oxidation method, p-dicumyl peroxidation method, phenol hydrogen peroxide hydroxylation method, bisphenol A law etc. [0004] Hydroxylation of phenol with hydrogen peroxide...

Claims

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Application Information

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IPC IPC(8): C07C39/08C07C37/05
Inventor 丁克鸿徐林程晓曦顾志强许金来戚明甫王怡明王殿防徐业庆
Owner JIANGSU YANGNONG CHEM GROUP
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