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Process for preparing 2,4-dichlorphenoxyacetic acid with high quality

A dichlorophenoxyacetic acid, high-quality technology, applied in the direction of carboxylate preparation, organic compound preparation, chemical instruments and methods, etc., can solve problems such as reduction

Inactive Publication Date: 2013-02-06
SHANGHAI CAC CHEM +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] The traditional primary chlorination of phenol to 2,4-dichlorophenol process, in order to improve the reaction conversion rate, the reaction selectivity of phenol to 2,4-dichlorophenol is only 90%, and the creosote oil (10%) will react with chlorine Acetic acid will also condense into phenoxyacetic acid under alkalinity, and reduce the quality of 2,4-dichlorophenoxyacetic acid. To reach 96% by mass, the product of 2,4-dichlorophenoxyacetic acid needs to be washed, which will produce A large amount of phenolic wastewater

Method used

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  • Process for preparing 2,4-dichlorphenoxyacetic acid with high quality
  • Process for preparing 2,4-dichlorphenoxyacetic acid with high quality

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0028] 1. Phenol chlorination to 4-chlorophenol:

[0029] (1) Take 1000 grams of phenol and put it into a 2000ml four-necked bottle, heat and melt it, and start stirring. Raise the temperature to 20°C, introduce the chlorine gas ventilation pipe under the phenol liquid surface, open the valve of the chlorine gas cylinder, start to feed chlorine gas, control the introduction of chlorine gas, keep the reaction temperature at 20-100°C, and optimally control it at 60-80°C. And absorb hydrogen chloride in the tail gas with water (for neutralization in the preparation of 2,4-dichlorophenoxyacetate). After 16 hours, when about 839 grams of chlorine gas was fed in, the mass percent content of phenol in the reaction solution was tracked by gas chromatography to be 0.1-0.5%, and the chlorine gas flow was stopped.

[0030] (2) At this time, the reaction solution is composed of (mass percentage content): 0.22% of phenol, 32.71% of 2-chlorophenol, 48.89% of 4-chlorophenol, 18.10% of 2,4-d...

Embodiment 2

[0045] A kind of technique for preparing high-quality 2,4-dichlorophenoxyacetic acid, flow chart as figure 1 shown, including the following steps:

[0046] (1) Phenol is placed in the reaction kettle, and chlorine gas is passed into it, and the weight ratio of chlorine gas and phenol is controlled to be 2: 10, and the chlorination reaction temperature is 20° C., and 2-chlorophenol, 4-chlorophenol and 2-chlorophenol are prepared. , the mixture of 4-dichlorophenol, the mass percent content of residual phenol detected by gas chromatography is 0.5%, then the temperature is controlled to be 50°C, and the hydrogen chloride gas obtained by feeding inert gas is removed from the reaction;

[0047] (2) 2-chlorophenol is separated by rectification under reduced pressure, and the reaction temperature of rectification under reduced pressure is 110 ℃, and reaction pressure is 30mmHg;

[0048] (3) continue to pass into chlorine and carry out chlorination reaction, control reaction temperatu...

Embodiment 3

[0051] A process for preparing high-quality 2,4-dichlorophenoxyacetic acid, comprising the following steps:

[0052] (1) Phenol is placed in the reaction kettle, and chlorine gas is passed into it, and the weight ratio of chlorine gas and phenol is controlled to be 3: 10, and the chlorination reaction temperature is 60° C., and 2-chlorophenol, 4-chlorophenol and 2-chlorophenol are prepared. , the mixture of 4-dichlorophenol, the mass percent content of residual phenol detected by gas chromatography is 0.6%, then the temperature is controlled to be 80°C, and the hydrogen chloride gas obtained by feeding inert gas is removed from the reaction;

[0053] (2) 2-chlorophenol is separated by rectification under reduced pressure, and the reaction temperature of rectification under reduced pressure is 110 ℃, and reaction pressure is 30mmHg;

[0054] (3) continue to feed chlorine and carry out chlorination reaction, control reaction temperature to be 60 ℃, react to detect 2 through gas ...

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Abstract

The invention relates to a process for preparing 2,4-dichlorphenoxyacetic acid with high quality; and the process comprises the following steps of: using phenol as a raw material; first chlorinating the phenol so as to prepare 2-chlorophenol, 4-chlorophenol and 2,4-chlorophenol; separating out the 2-chlorophenol through rectifying; further chlorinating the 4-chlorophenol to obtain 2,4-dichlorophenol immediate with mass percentage of not less than 98%; and under an alkaline condition, reacting the 2,4-dichlorophenol immediate with chloroacetic acid, so as to obtain 2,4-dichlorphenoxyacetic acid with mass percentage of not less than 98%. Compared with the prior art, the process for preparing 2,4-dichlorphenoxyacetic acid with the high quality, provided by the invention, has the advantages as follows: the 2,4-dichlorphenoxyacetic acid (98%) with high quality is obtained; meanwhile, untransformed 2,4-dichlorophenol is recycled through solvent extraction and is recycled as reaction raw material for the next reaction through being neutralized and alkalified; therefore, the environment friendly process for preparing the 2,4-dichlorphenoxyacetic acid with high quality and high yield is provided.

Description

technical field [0001] The invention relates to a preparation process of a pesticide intermediate, in particular to a process for preparing high-quality 2,4-dichlorophenoxyacetic acid. Background technique [0002] Phenoxyacetic acid herbicides are a type of hormonal herbicides and one of the commonly used plant hormones. 2,4-D is one of the earliest discovered and most widely used varieties. As early as 1945, it has been successfully commercialized and used. It is one of the earliest pesticide herbicides developed in the world. From 1950 to 1970, there were a large number of synthetic literature and literature on 2,4-dichlorophenol and 2,4-D at home and abroad. According to the patent report, the process used is phenol first chlorination method, which is currently used by major 2,4-D manufacturers at home and abroad, that is, phenol is chlorinated into 2,4-dichlorophenol, and the reaction selectivity is only 90% %, during which 2-chlorophenol, 2,6-dichlorophenol and 2,4,6-...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C07C59/70C07C51/367
Inventor 李宗成郑留清周庆江朱正江李瑞清
Owner SHANGHAI CAC CHEM
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