Method for preparing p-anisidine through catalytic hydrogenation of p-nitroanisole

Abstract

The invention provides a method for preparing p-aminoanisole by hydrogenating p-nitroanisole. In the presence of KT-02 supported nickel catalyst, the reduction reaction of p-nitroanisole can be started under relatively mild conditions to generate p-aminoanisole. Compared with the existing techniques such as nitrobenzene method, sodium sulfide or iron reduction method, the present invention has the advantages of mild reaction conditions, fast reaction speed, clean reaction process, easy separation of products and the like.

Description

technical field [0001] The invention provides a method for preparing p-aminoanisole by hydrogenating p-nitroanisole. 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) 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 nic...

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 the 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 ( 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 large

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