Method for preparing 3,4-dichloroaniline by using o-dichlorobenzene through nitration and hydrogenation

Abstract

The invention discloses a method for preparing 3,4-dichloroaniline by using o-dichlorobenzene through nitration and hydrogenation, the method comprises the following steps: materials of o-dichloroaniline, sulfuric acid, recycled acid, and nitric acid in a ratio of 2.34: 1.6: 1.1: 1.3 are added into a nitration kettle for nitration reaction so as to obtain a 3,4-dichloronitrobenzene and 2,3-dichloronitrobenzene mixed solution; the mixed solution enters a main rectifying tower to be subjected to reduced pressure rectification and crystallization separation to obtain more than 99.5% of 3, 4-dichloronitrobenzene and 2,3-dichloronitrobenzene; and 3, 4-dichloronitrobenzene, a palladium-carbon catalyst and ethanol are added into a hydrogenation kettle, hydrogen is introduced while stirring, desolventizing is performed after the reaction is ended, and reduced pressure rectification is performed to obtain a finished product of 3,4-dichloroaniline with the purity of more than 99.5%. The method is simple in process and wide in temperature and pressure range and is easy to control, so that the environment is protected, the cost is saved, and the yield is improved.

Description

Technical field: [0001] The invention belongs to the technical field of fine chemicals, and relates to a method for industrially producing 3,4-dichloroaniline, in particular to a method for preparing 3,4-dichloroaniline by nitrating and hydrogenating o-dichlorobenzene. Background technique: [0002] 3,4-Dichloroaniline is an important chemical intermediate, which is an isomer of 2,5-dichloroaniline. It can be used as an intermediate of pesticides and dyes, and is used to synthesize propanil and liguron , Diuron, Metrapyr and other herbicides and azo dyes can also be used as intermediates of biologically active components. In the dye industry, it is used to synthesize C.I. Disperse Red 152 and 153; in medicine, 3,4-dichlorophenylthiourea can be prepared by mixing 3,4-dichloroaniline with ammonium thiocyanate, and 3 , 4-dichlorophenol and mothproof agent for wool textiles, Miding FF, etc. [0003] At present, the chlorobenzene route is mostly used for the preparation of 3,4-...

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Problems solved by technology

[0004] In order to solve the deficiencies in the prior art, the purpose of the present invention is to provide a method for preparing 3,4-dichloroaniline by nitration and hydrogenation of o-dichlorobenzene, which effectively solves the problem of preparing 3,4-dichloroaniline by nitration of chlorobenzene. Aniline produces a large number of by-products