Method for purifying pendimethalin

A pendimethalin and purification method technology, applied in the field of pendimethalin purification, can solve the problems of increasing the difficulty and safety of operation, reducing the content of N-nitrosamine compounds, harsh equipment material conditions, etc., and achieving a reaction speed Fast, reduce the difficulty of operation and equipment requirements, increase the effect of safety

Active Publication Date: 2010-11-24
JIANGSU YONGAN CHEM CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Relevant scientific research institutions and production enterprises in all countries in the world have conducted research on this. U.S. Patent 5196585 and others have introduced the generation of tissue by-products such as sulfite and dithionate in the nitrification process, but after adopting this method, N- The content of nitrosamine compounds is still more than 10%; U.S. Patent No. 4,136,117 and other reports use sulfamic acid and 37.7% hydrochloric acid to react for 6 hours under the conditions of 80-82°C after nitration, and the content of N-nitrosamine compounds can reach 0.1 %; U.S. Patent US5922915 and other reports increase the temperature of the material to 170~180°C in the

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0019] Add 0.25g crude pendimethalin, 0.03g sodium thiocyanate, and 0.125g hydrochloric acid with a mass concentration of 31% in a three-necked glass flask equipped with a stirring and heating device, and reflux at 80°C for 15 hours, and add additional 0.01 g sodium thiocyanate. The N-nitrosamine is traced by liquid chromatography and is less than 10ppm. After the reaction, the oil layer is washed with water, alkali and washed again, and then controlled at a temperature of less than 90°C under a vacuum of -0.01Mpa to remove the solvent to obtain the finished pendimethalin. The mass content of the pendimethalin is 96.7%, and the N-nitrosamine content is less than 16ppm.

[0020] The crude pendimethalin in this embodiment is the crude pendimethalin dissolved in the dichloroethane solvent after nitration, and the weight content of the dichloroethane solvent in the pendimethalin crude product is 60%.

Embodiment 2

[0022] Add 5g pendimethalin crude product, 0.71g sodium thiocyanate, 2.13g hydrochloric acid with a mass concentration of 31% in a three-neck glass flask equipped with a stirring and heating device, reflux at 80°C for 15 hours, and add 0.23 g sodium thiocyanate. The N-nitrosamine is traced by liquid chromatography and is less than 10ppm. After the reaction, the oil layer is washed with water, alkali and washed again, and the vacuum degree is -0.01Mpa. The mass content of the pendimethalin is 96.2%, and the N-nitrosamine content is less than 5ppm.

[0023] The crude pendimethalin in this embodiment is the crude pendimethalin dissolved in the dichloroethane solvent after nitration, and the weight content of the dichloroethane solvent in the pendimethalin crude product is 60%.

Embodiment 3

[0025] In the 100L reactor, add 40kg pendimethalin crude product, mass concentration is 31% hydrochloric acid 12kg, sodium thiocyanate 4.0kg and stir and add ammonium thiocyanate 1.6kg after refluxing at 75 ℃ for 8 hours, this moment N-substance The nitramine compound content is between 100-200ppm, and the reflux is continued for 7 hours. Liquid chromatographic analysis shows that the N-nitrosamine content is less than 10ppm, and the reaction ends. After conventional water washing, alkali washing, and water washing, the temperature below 90°C is controlled and the vacuum degree is -0.01Mpa to remove the solvent to obtain the finished pendimethalin. The mass content of the obtained pendimethalin is 96.4%, and N-nitroso The amine content is less than 10 ppm.

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Abstract

The invention discloses a method for purifying pendimethalin, which comprises the following steps of: adding coarse product of pendimethalin, thiocyanate and hydrochloric acid into a reaction container according to a mass ratio of 7-10:1:3-5; performing reflux reaction at the temperature of between 75 and 81 DEG C for 6 to 15 hours under normal pressure, adding the thiocyanate again in the reaction process for continuous reaction until the content of N-nitrosamine compound is less than 10ppm, and taking an oil layer after the reaction is finished; and washing the oil layer with water, alkali and water in turn and controlling the temperature to between 60 and 90 DEG C under the vacuum condition for removing a solvent so as to obtain the pendimethalin. The method for purifying the pendimethalin has the advantages that: due to the existence of the aid thiocyanate, the speed of the reaction for removing the N-nitrosamine compound is high, and the content of the N-nitrosamine compound is less than 20ppm; because the reaction temperature is controlled at the reflux temperature, the method does not need to be operated under the pressure condition, and can reduce the operating difficulty and equipment requirement and improve the operating safety.

Description

technical field [0001] The invention relates to a method for purifying herbicides, in particular to a method for purifying pendimethalin. Background technique [0002] Pendimethalin, its chemical name: N-(ethylpropyl)-3,4-dimethyl-2,6-dinitroaniline; is a dinitroaniline herbicide, applicable Annual grasses and some broadleaf weeds. Because pendimethalin products have good weeding effect and high safety, they have been widely popularized and applied. [0003] The current process uses 3,4-dimethylnitrobenzene as the starting material, undergoes hydrogenation reduction, alkylation reaction with 3-pentanone, nitration reaction, and denitrosation reaction to obtain the product pentamethylpentane spirit. It is recorded in US Patent No. 4,136,117 and US Patent No. 4,621,157 that about 20% of toxic N-nitroso by-products will be produced during the nitration reaction of this process. It is described in Adv. Cancer. Res. 1967.10: 163 (Frontier Cancer Research, October 1967, p. 163...

Claims

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Application Information

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IPC IPC(8): C07C211/52C07C209/84
Inventor 赵坚强钟锡君
Owner JIANGSU YONGAN CHEM CO LTD
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