Method for preparing X substituted aniline from X substituted nitrobenzene

Abstract

The invention discloses a method for preparing X substituted aniline by catalytic hydrogenation of X substituted nitrobenzene; wherein the X can be any one of -F, -Cl, -Br, -OCH3, -OH or-R, R is saturated hydrocarbyl with one or more carbons and the position of X in the nitrobenzene is ortho position, or meta position, or para position of nitryl. The method comprises the following steps: adding X substituted nitrobenzene in a reaction kettle; and then adding ethanol and a supported catalyst; sealing the reaction kettle; completely replacing air in the reaction kettle with hydrogen; maintaining normal pressure in the reaction kettle and heating and stirring the mixture; introducing the hydrogen into the kettle after the temperature reaches 60 DEG C; maintaining the pressure in the kettle between 1.0 and 3.0 MPa; starting hydrogenation reaction and maintaining the temperature in the kettle between 60 and 90 DEG C during the hydrogenation process; and separating reaction mixture and the catalyst when the conversion rate reaches 95-99 percent after hydrogenation for 3 to 8 hours.

Description

technical field [0001] The invention relates to a method for preparing X-substituted aniline by catalytic hydrogenation of X-substituted nitrobenzene, where X can be -F, -Cl, -Br, -OCH 3 , -OH, or -R, wherein R is a saturated hydrocarbon group with 1 or more carbons, and the position of X in nitrobenzene is the ortho or meta or para position of the nitro group. 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 inconvenie...

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 the required temperature is 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 ( It is called tar in the industry, which reduces the yield of the product 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