Purifying method of 2, 3-dichloropyridine

Abstract

The invention discloses a purifying method of 2,3-dichloropyridine. The purifying method comprises the following steps of: mixing a crude 2, 3-dichloropyridine product, a treating agent and an organic solvent to form a liquid phase reaction system, and enabling the liquid phase reaction system to react at the temperature of 20-90DEG C; extracting a sample from the liquid phase reaction system, detecting the sample by using liquid chromatography under the detection conditions that the wavelength is 235nm and the volume ratio of methanol to water in a moving phase is 70:30, and when the content of 2,3,6-trichloropyridine in the sample is less than 0.5 percent, ending the reaction, or continuously reacting; and preparing a product solution after the reaction is ended, then cooling the product solution so that a crystallized product is sufficiently separated out, carrying out solid-liquid separation to obtain the crystallized product, adding the crystallized product to water so as to form a dispersed system, adjusting the pH of the dispersed system to be 1-4 by using inorganic acid, and filtering the dispersed system to obtain solid matters, namely the purified 2, 3-dichloropyridine.

Description

technical field [0001] The invention relates to a method for purifying 2,3-dichloropyridine. Background technique [0002] 2,3-Dichloropyridine is a key intermediate in the synthesis of the pesticide chlorantraniliprole, and its content directly determines the selectivity of subsequent reactions and the quality of the final product chlorantraniliprole. If the 2,3-dichloropyridine produced by domestic manufacturers is detected by liquid chromatography under the detection conditions of wavelength 235nm and mobile phase methanol:water=70:30, its main content is greater than 95%, and the main impurity content is 2- 4%. [0003] The impurity is mainly 2,3,6-trichloropyridine. 2,3,6-trichloropyridine is the result of excessive chlorination during the synthesis of 2,3-dichloropyridine. It is difficult to completely avoid it during the synthesis process. The presence of 2,3,6-trichloropyridine leads to a decrease in product selectivity in subsequent processes, high viscosity of in...

AI Technical Summary

Problems solved by technology

[0006] There are currently two liquid chromatography methods in China for the detection of 2,3-dichloropyridine. The main reason is that the detection wavelength is different: one is detected at a wavelength of 265nm, and the response value to the impurity 2,3,6-trichloropyridine Therefore, the content of the product detected by this method is above 99%; the second type is detected at a wavelength of 235nm, and the response value to the impurity 2,3,6-trichloropyridine is high, and the main content is above 95%. ; Therefore, the same 2,3,-dichloropyridine sample is detected by different wavelengths, and there is a large difference in content; at present, domestic 2,3-dichloropyridine manufacturers use 265nm wavelength detection, and its product content is greater than 99%. Chlorine The manufacturer of benzamide uses 235nm wavelength detection, and the raw material 2,3-dichloropyridine enters the factory with a content greater than 95%.

[0007] Due to differences in detection methods, and there is no industry standard or national standard, 2,3-dichloropyridine manufacturers and users often have differences in detection conclusions