Method for controlling continuous reaction crystal size of 2,4-dichlorphenoxyacetic acid
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A technology of dichlorophenoxyacetic acid and dichlorophenoxyacetic acid salt, applied in the field of herbicides, can solve the problems of small particle size and wide distribution, and achieve the effects of increasing average particle size, less equipment corrosion, and high yield
Active Publication Date: 2015-01-14
TIANJIN UNIV OF SCI & TECH +1
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Problems solved by technology
It avoids the phenomenon of liquid-liquid stratification during the crystallization process by cooling after the acidification reaction at high temperature, and then overcomes the problem of small particle size and wide distribution caused by explosive nucleation caused by liquid-liquid stratification
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Embodiment 1
[0026] Using 2,4-D sodium salt as a raw material, a 90°C saturated solution of 2,4-D sodium salt and a 33.74% HCl aqueous solution were prepared according to step (1). Then carry out reaction crystallization according to step (2): continuously add 2,4-D sodium salt and hydrochloric acid solution to the reaction crystallizer, control the reaction crystallization temperature to 45°C, and the molar ratio of 2,4-D sodium salt to hydrochloric acid is 1:1.1, residence time is 7h, stirring rate is 300rpm. When the system is stable, the main particle size of the product is 185.382 μm, the purity of the final 2,4-D product is 99.2%, and the yield of the crude 2,4-D product is 99.5%.
Embodiment 2
[0028] Using 2,4-D sodium salt as a raw material, a 90°C saturated solution of 2,4-D sodium salt and a 20.00% HCl aqueous solution were prepared according to the implementation step (1). Then carry out reaction crystallization according to the implementation step (2): continuously add 2,4-D sodium salt and hydrochloric acid solution into the reaction crystallizer, control the reaction crystallization temperature at 25°C, and the molar ratio of 2,4-D sodium salt to hydrochloric acid is 1:1.1, residence time is 5h, stirring speed is 400rpm. After the system is stable, the main particle size of the product is 168.872μm. The purity of the final 2,4-D product was 98.6%, and the yield of the crude 2,4-D product was 99.1%.
Embodiment 3
[0030] Using 2,4-D potassium salt as a raw material, firstly, according to the implementation step (1), a saturated solution of 2,4-D potassium salt at 80°C and an aqueous HCl solution with a mass fraction of 37.00% are prepared. Then carry out the reaction crystallization according to the implementation step (2): continuously add 2,4-D potassium salt and hydrochloric acid solution into the reaction crystallizer, control the reaction crystallization temperature to 35°C, and feed 2,4-D sodium salt and hydrochloric acid by moles The ratio is 1:1.1. The residence time is 5h, and the stirring rate is 360rpm. When the system is stable, the main particle size of the product is 180.453μm. The purity of the final 2,4-D product was 99.1%, and the yield of the crude 2,4-D product was 99.5%.
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Abstract
The invention relates to a method for controlling a continuous reaction crystal size of a herbicide 2,4-dichlorphenoxyacetic acid. The method comprises the following steps: (1) preparing a 80-100 DEG C saturated or nearly saturated solution of a 2,4-dichlorphenoxyacetic acid salt, and 10-38% hydrochloric acid respectively; (2) in a crystallizer, continuously adding the 2,4-dichlorphenoxyacetic acid salt solution and the hydrochloric acid prepared in the step (1), wherein a molar ratio of the 2,4-dichlorphenoxyacetic acid salt to hydrochloric acid is 1 to (1-1.2), controlling the crystallization temperature at 20-60 DEG C, controlling the retention time to 2-10 hours, continuously discharging the material to an after-treatment process to obtain the 2,4-dichlorphenoxyacetic acid product. According to the crystal size control method disclosed by the invention, the 2,4-dichlorphenoxyacetic acid salt is dissolved at a high temperature, the 2,4-dichlorphenoxyacetic acid salt solution and hydrochloric acid are subjected to a continuous reaction crystallization process in the crystallizer at a low temperature, so that the problems that the 2,4-dichlorphenoxyacetic acid product produced by the process of performing acidification reaction at a high temperature and then cooling for crystallizing is low in purity and small in crystal size and easily causes equipment corrosion are solved. The method has the advantages that the prepared produce has a great crystal size and a high purity, energy consumption is low, equipment corrosion is hardly caused, the operation is simplified and the process is easily controlled automatically.
Description
(1) Technical field [0001] The invention relates to a method for controlling the particle size of the herbicide 2,4-dichlorophenoxyacetic acid. (2) Background technology [0002] 2,4-Dichlorophenoxyacetic acid, 2,4-D for short, is currently one of the most widely used herbicides in the world. In its synthetic production process, it is usually necessary to first generate 2,4-dichlorophenoxyacetic acid salt, namely 2,4-D sodium salt or 2,4-D potassium salt, and finally acidify to obtain 2,4-D acid. [0003] The preparation method of 2,4-D in the published patent CN1194259A is as follows: the 2,4-dichlorophenoxyacetic acid sodium salt prepared above is purified in the aqueous phase at a pH value of 9-10 to reduce its phenol content . Then the sodium salt is acidified in hydrochloric acid and converted into 2,4-dichlorophenoxyacetic acid. After the acid is filtered by suction to make the chloride qualified, it is separated and separated. After drying, it is packaged into a genuine p...
Claims
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Application Information
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