Method for preparing diaminobenzene from dinitro benzene

Abstract

The invention discloses a method for preparing diaminobenzene by using dinitro benzene which refers to paradinitrobenzene or m-dinitrobenzene. The method comprises the steps as follows: the dinitro benzene is added into a kettle firstly and then ethanol and a supported catalyst are added; the kettle is closed and air in the kettle is replaced by using hydrogen; then normal pressure is maintained in the kettle and heating and mixing are carried out; the hydrogen is introduced into the kettle after temperature in the kettle reaches 60 DEG C so as to lead the pressure in the kettle to be maintained at 1.0 MPa to 3.0 MPa and then hydrogenation reaction is started; a conversion ratio can reach 95 percent to more than 99 percent after the hydrogenation for about 3 hours to 8 hours and then a reacted mixture and the catalyst are separated out; the catalyst separated is returned to the kettle for continuous use to supplement the lost catalyst; reaction product separation is carried out to the reacted mixture which is a clear solution so as to obtain the diaminobenzene.

Description

technical field [0001] The invention relates to a method for preparing diaminobenzene from dinitrobenzene, where the dinitrobenzene refers to p-dinitrobenzene or m-dinitrobenzene. Background technique [0002] The reduction of nitro compounds to amino compounds was first prepared by the method of iron powder and hydrochloric acid. This method is seriously polluting, and it is a process route that will be abolished in the near future as stipulated by the state. In recent years, most of this kind of production uses Raney nickel catalysts. , that is, the conversion of nitro to amino groups is realized by catalytic hydrogenation using Raney nickel as a catalyst, but the use of Raney nickel catalysts for catalytic hydrogenation has the following disadvantages: [0003] 1) It is extremely inconvenient to use. Because the active component of the Raney nickel catalyst for catalytic hydrogenation is skeleton nickel, but skeleton nickel is extremely easy to catch fire in the air and ...

AI Technical Summary

Problems solved by technology

[0003] 1) Very inconvenient to use

Because the active component of the Raney nickel catalyst for catalytic hydrogenation is skeleton nickel, but skeleton nickel is extremely easy to catch fire in the air and cannot be preserved. It can only be used as a commodity in the form of nickel-aluminum alloy powder. Dissolve the aluminum, wash it and add it to the reaction system under the condition of isolating the air; in addition, the catalytic activity of Raney nickel often changes greatly due to different treatment conditions (such as alkali dissolution and washing conditions)

[0004]2) When Raney nickel catalyst is used, the amount of by-products of the reaction is large and the product yield is low

The hydrogenation of the Raney nickel catalyst to transform the nitro group into an amino group often requires a higher temperature, generally higher than 100 °C, and the product amino compound generated by hydrogenation is easy to generate by-products at a temperature higher than 100 °C ( Industrially referred to as tar), which reduces the product yield on the one hand, and may also affect the normal progress of the reaction on the other hand.

[0005]3) Catalyst consumption is high

Due to the low catalytic activity of Raney nickel, the amount of catalyst that needs to be added is relatively large. On the other hand, because the recovery of the catalyst is extremely difficult, the consumption of the catalyst is too large, resulting in high production costs.

[0006]4) There are huge potential safety hazards in production

Because Raney nickel is easy to catch fire when it sees air, a fire will occur if there is a little carelessness in operation; at the same time, there is hydrogen in the hydrogenation workshop, which is very easy to explode