P-chloroaniline hydrochloride preparation method

Abstract

The invention provides a p-chloroaniline hydrochloride preparation method, which comprises: in the presence of an organic solvent azeotropic with water, using p-chloronitrobenzene as a starting raw material, adding anti-dehalogenation agent and an acid binding agent, sealing, introducing hydrogen gas, carrying out a hydrogenation reaction under the catalysis of a platinum-carbon catalyst at a hightemperature under a high pressure, cooling, filtering to remove the catalyst, collecting the filtrate, adding concentrated hydrochloric acid to the filtrate, carrying out thermal insulation for 0.5-2h at a temperature of 80-95 DEG C, continuously heating to achieve a boiling state, refluxing by a water separator until no water is separated, filtering, and drying to obtain p-chloroaniline hydrochloride. According to the present invention, the preparation method has characteristics of mild and controllable reaction conditions, simple operation and low cost, performs the two steps through the one-pot method, and provides the advanced preparation method for industrial production.

Description

technical field [0001] The invention belongs to the field of synthesis of pharmaceutical intermediates, in particular to a preparation method of p-chloroaniline hydrochloride. Background technique [0002] p-Chloroaniline hydrochloride is an important organic chemical raw material and intermediate, and plays an important role in the fields of medicine, dyes, pesticides, rubber additives, synthetic resins, spices, photography, etc. [0003] p-Chloroaniline is generally prepared by reduction of p-chloronitrobenzene, the reaction equation is as follows: [0004] [0005] The reduction methods of nitro group mainly include iron powder reduction method, alkali sulfide reduction method, hydrazine hydrate reduction method and catalytic hydrogenation reduction method. The iron powder reduction method has the characteristics of relatively mature technology, easy production control, and few side reactions. It is the main method for producing p-chloroaniline, but there are difficul...

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Problems solved by technology

[0009] But still have the generation of part dechlorination thing (aniline), cause hydrogenation reaction yield on the low side, crude product purity is not up to standard (crude product purity about 90%), in addition, along with the generation of dechlorination side reaction, with dechlorination thing ( Aniline) and the generation of additional by-product HCl, which will cause certain corrosion to the hydrogenation tank

[0010] 2) In order to improve the purity of the prepared p-chloroaniline, the crude product p-chloroaniline needs to be further purified, and the purification of the existing crude product p-chloroaniline (purity about 90%) needs to be realized by rectification and purification in a ten-meter-high rectification tower, The purification operation of the rectification tower is complicated, the yield is low, waste of energy and man-hours, which virtually complicates the production process

The water content of concentrated hydrochloric acid is generally about 64%, and p-chloroaniline hydrochloride is very soluble in water. During the post-treatment process of the traditional industrial production process of p-chloroaniline hydrochloride, it is concentrated until a small amount of water remains in the later stage and remains p-chloroaniline hydrochloride. Salt has bigger solubility, causes product yield (yield is about 85%) on the low side

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