Preparation method of 2-chloropyridine

Abstract

The invention provides a preparation method of 2-chloropyridine. The method comprises the following steps of: mixing pyridine and water by a molar ratio of 1:(1.5-3.6) and adding an activating agent; vaporizing, then leading the pyridine and the water into a glass reactor by a molar ratio of 1:(0.70-0.80) to carry out a chlorination reaction for 3-5 seconds at 150-170 DEG C in the presence of an ultraviolet light source and carrying out cooling and gas-liquid separation on an obtained reaction mixture; absorbing the separated gas phase to form hydrochloric acid by using water; and neutralizing the separated liquid phase and then distilling to obtain pyridine, 2-chloropyridine and 2,6-dichloropyridine, wherein distilled water is applied to the production of a next batch. Because the activating agent is added in the process of the chlorination reaction, activation energy and reaction temperature which are required by the chlorination reaction are reduced, and the process period is shortened. By adopting the glass reactor with a built-in helical filler and the ultraviolet light source the wavelength of which is matched with the glass reactor, the probability of secondary chlorination of the 2-chloropyridine is reduced, and the conversation rate and the selectivity of 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.