2-chloro pyridine preparation method

Abstract

The invention provides a 2-chloro pyridine preparation method. Pyridine and water are mixed according to the molar ratio of 1:1.5-3.6, an activator is added, pyridine and chlorine are fed into a glass reactor according to the molar ratio of 1:0.70-0.80 after vaporization, chlorination reaction is performed under the effect of an ultraviolet light source at the temperature of 150-170 DEG C, the reaction time is 3-5 seconds, and the reaction mixture undergoes cooling and gas-liquid separation. The separated gas phase is absorbed with water to produce hydrochloric acid, the separated liquid phase is neutralized and then is distilled to obtain pyridine, 2-chloro pyridine and 2,6-dichloro pyridine, and a water jacket is distilled out for the next batch of production. Due to the fact that the activator is added in the process of chlorination reaction, the activation energy and reaction temperature required by the chlorination reaction are reduced, and a process cycle is shortened. By the adoption of the glass reactor provided with a spiral packing in the inside and the ultraviolet light source matched with the glass reactor in wavelength, the probability that the 2-chloro pyridine is secondarily chlorinated is reduced, and the conversion rate and selectivity of the raw materials are improved.

Description

technical field [0001] The invention relates to a preparation method of chemical products, in particular to a preparation method of 2-chloropyridine. Background technique [0002] 2-Chloropyridine is a colorless or light yellow transparent liquid, insoluble in water, soluble in ether, ethanol, chloroform and other organic solvents, is an important special fine chemical intermediate, mainly used in the synthesis and Additives for daily chemical products have important applications in the pyridine organic synthesis industry. [0003] At present, there are many synthesis routes of 2-chloropyridine, and the industrial synthesis technology mainly includes the following four types according to the raw material routes: one is the multi-step substitution method, in which one of the raw materials of the reaction, sodium amide, is a first-class flammable, explosive , not in contact with air and water, the biggest problem with this method is that there are many steps and the conversio...

AI Technical Summary

Problems solved by technology

[0003] At present, there are many synthesis routes of 2-chloropyridine, and the industrial synthesis technology mainly includes the following four types according to the raw material routes: one is the multi-step substitution method, in which one of the raw materials of the reaction, sodium amide, is a first-class flammable, explosive , not in contact with air and water, the biggest problem with this method is that there are many steps and the conversion rate is low

The second is the pyridine N-oxide method, which is to react pyridine with hydrogen peroxide to generate pyridine N-oxide, then react with chlorine gas to generate 2-chloropyridine N-oxide, and obtain 2-chloropyridine after reduction; This method is a traditional synthetic method, the technology is mature and simple, but the route is lengthy, there are certain three wastes pollution, and the yield is low

The third is the 2-hydroxypyridine method. The 2-hydroxypyridine is chlorinated with chlorinating agents such as thionyl chloride and phosphorus pentachloride, and the hydroxyl group and the chlorine atom undergo a displacement reaction to obtain 2-chloropyridine. The process of the method is simple, but the raw material The source of 2-hydroxypyridine is limited

Although this method shortens the process flow compared with the original gas-phase photochlorination method, the operation of the reaction process is easy to control, the total yield is improved, and the waste liquid discharge is reduced, but it still needs further improvement.