Method for preparing 2,6-dichloropyridine by pyridine liquid-phase photochlorination

Abstract

The invention relates to a method for preparing 2,6-dichloropyridine with product purity greater than or equal to 99.0% by using chlorotrifluoromethylbenzene as a solvent for a reaction between pyridine and chlorine. The preparing process comprises the steps as follows: by using the pyridine and the chlorine as initial raw materials and using the chlorotrifluoromethylbenzene as the solvent, continuously performing a chlorination reaction on the pyridine and the chlorine under the irradiation of ultraviolet light; and cooling a chlorination reaction product and the solvent to obtain pyridine chloride solution. The method has the advantages that 1, a precedent of directly preparing the 2,6-dichloropyridine in a high selectivity mode by a liquid-phase photochlorination reaction is set, and not only is the 2,6-dichloropyridine product with purity greater than or equal to 99.0% obtained, but also the method is easy for industrial production; and 2, not only is recycling of the separation solvent in the preparing process of the 2,6-dichloropyridine product with purity greater than or equal to 99.0% implemented, but also the aims of low pollution, low energy consumption and low cost in the preparing process are fulfilled.

Description

technical field [0001] The invention relates to a method for preparing 2,6-dichloropyridine with a product purity ≥ 99.0% by using trifluoromethyl chlorobenzene as a solvent for the reaction between pyridine and chlorine gas. Background technique [0002] The existing main synthesis methods of 2,6-dichloropyridine are: vapor-phase photochlorination of pyridine aqueous solution, the main product obtained is a mixture of 2-chloropyridine and 2,6-dichloropyridine, and the ratio of 2,6-dichloropyridine Generally, it is 5% to 50%. The chlorinated materials need to be separated and purified through a series of steps such as alkali neutralization, rough steaming and rectification, which will generate a large amount of waste water and waste salt, and the disposal cost of the three wastes is high. [0003] In the direct heating chlorination method of pyridine without ultraviolet light, the yield of 2,6-dichloropyridine is less than 30%, the coking rate is about 45%, a large amount of...

AI Technical Summary

Problems solved by technology

[0005] Design purpose: In order to avoid the deficiencies in the background technology, design a pyridine liquid phase that uses trifluoromethyl chlorobenzene as the solvent for the reaction of pyridine and chlorine to achieve the purity of the prepared 2,6-dichloropyridine product ≥ 99.0% The method for preparing 2,6-dichloropyridine by photochlorination overcomes the disadvantages of the large amount of three wastes produced in the preparation method of the background technology and the clogging of tail gas pipes by materials, reduces the discharge of three wastes, reduces production costs, is easier for industrial production, and achieves a purity of ≥99.0 Low pollution, low energy consumption and low cost for the preparation of %2,6-dichloropyridine products