Process for synthesizing 2-chloropyridine from chlorine and pyridine

Abstract

A process for synthesizing 2-chloropyridine from pyridine and chlorine gas includes such technological steps as reaction while rectification, neutralization, and refining by rectification. It features that the liquid-phase mixture of pyridine and water in mol ratio of 1 : 3 is fed into coupled rectifying tower-reactor, the mixture containing pyridine output from tower top is partially returned back into tower, residual is fed to top of reactor while the mol raatio of chlorine gas to pyridine is ensured to be 1 : 2.5-4.0, the residual and chlorine gas take part in parallel-current reation in reactor to generate 2-chloropyridine, and after neutralized it comes to central position of coupled rectifying tower with the temp at top of 94-96 deg.C and reactor temp of 140-190 deg.C. Its advantages include short technological route, high output rate and less waste liquid drainage.

Description

technical field [0001] The invention relates to a process for synthesizing 2-chloropyridine by using pyridine and chlorine gas as raw materials, which belongs to the improvement of the process for synthesizing 2-chloropyridine. technical background [0002] 2-Chloropyridine is a raw material intermediate used in the synthesis of medicines, preservatives, fungicides and fungicides. Its downstream products have the characteristics of high efficiency and low toxicity, and are widely used in pharmaceutical, shipbuilding, construction and metal processing industries. Now It is gradually being pushed into the daily chemical market. In addition, this product can also be used to produce low-toxic pesticides and other industrial chemicals, and the future application prospects are extremely promising. [0003] There are two methods for synthesizing 2-chloropyridine from pyridine and chlorine: one is catalytic thermal chlorination, and the other is gas p...

AI Technical Summary

Problems solved by technology

The main problems in this process are: long process, low total yield, and large amount of waste liquid discharge

The reaction temperature of the catalytic thermal chlorination method is relatively high, usually above 300°C, the reaction process is intense, the temperature is not easy to control, and there is even a danger of explosion. The product yield is higher when there is a directional catalyst, but the highest yield does not exceed 70% (U.S. Patent, US2820791, 1958; Japanese Patent Flat 2-134365, 1990), a large amount of coke is also by-produced in the process, which not only brings difficulties to the separation of products, but also easily blocks pipelines; photochlorination method The reaction temperature is below 190 DEG C, and the reaction conditions are milder than the catalytic thermal chlorination method, but there are also low yields (no more than 54%, Japanese patent flat 1-308256, 1989), many by-products, and the operation of the reaction process is difficult to control The problem

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