Method for preparing o-chloroaniline by catalytic hydrogenation

Abstract

The invention discloses a method for preparing o-chloroaniline by catalytic hydrogenation. O-nitrochlorobenzene, ethyl acetate solution, a dechlorination inhibitor and hydrogen are subjected to catalytic hydrogenation synthetic reaction under the effect of a catalyst at the temperature of 25-90 DEG C to obtain the o-chloroaniline. For better technical effects, the o-nitrochlorobenzene, ethyl acetate solution, dechlorination inhibitor are continuously delivered to a fixed bed reactor by a metering pump, inlet amount of hydrogen is controlled by a flow meter, and catalytic hydrogenation synthetic reaction is conducted in the fixed bed reactor. The fixed bed reactor which uses Ni alloy as the catalyst and a neutral carrier as a catalyst carrier is used for controlling the inlet amount of raw materials and hydrogen and the catalyst, thus reducing cost and improving efficiency. In the invention, dechlorination reaction can be effectively inhibited, subsequent processing steps of the principal product are simplified, coupling compounds generated in reaction are little, the selectivity of o-chloroaniline is above 99%, and the dechlorinating amount is below 0.3%. The invention has the advantages of mass industrial production and environment protection.

Description

technical field [0001] The invention relates to a method for preparing aniline, in particular to a method for preparing o-chloroaniline by catalytic hydrogenation, and belongs to the field of preparing o-chloroaniline. Background technique [0002] O-chloroaniline is an important dye intermediate, pharmaceutical intermediate, solvent, antifungal agent and reagent, etc. It is widely used in the production of fine chemicals such as pesticides, dyes, and medicine. Traditional nitro reduction methods mainly include iron powder reduction method, alkali sulfide reduction method, catalytic hydrogenation reduction method, and electrochemical reduction method. The iron powder reduction method produces a large amount of iron sludge, which seriously pollutes the environment; the alkali sulfide reduction method has disadvantages such as complex reduction routes, low product yield, and large waste liquid; the electrochemical reduction method consumes too much energy; the catalytic hydrog...

AI Technical Summary

Problems solved by technology

The iron powder reduction method produces a large amount of iron sludge, which seriously pollutes the environment; the alkali sulfide reduction method has disadvantages such as complex reduction routes, low product yield, and large waste liquid; the electrochemical reduction method consumes too much energy; the catalytic hydrogenation method has a reaction route Short, low energy consumption, environmental protection and other advantages

However, in the process of preparing o-chloroaniline by catalytic hydrogenation of o-nitrochlorobenzene, the side reactions of hydrogenation and dechlorination of C-Cl bonds to generate aniline and condensation of amino groups on the benzene ring to form azo may also occur, so that the subsequent production of the main product The processing steps increase the filtration and other links, and a large amount of coupling compounds will be produced in the reaction, and the coupling compounds will be attached to the wall of the rectification tower, which will cause great difficulties in the regular cleaning of the rectification tower

At the same time, the hydrogen chloride generated by dechlorination will cause corrosion to the equipment

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