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[Chemical Knowledge]：Production and manufacturing method and process flow of p-nitroaniline

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The manufacturing method
of p-nitroaniline
1. Introduction

p-nitroaniline is an important organic chemical raw material, widely used in dyes, medicine, pesticides and other fields. Therefore, it is of great practical significance to study the manufacturing method of p-nitroaniline. This paper will introduce the preparation method of p-nitroaniline by reduction reaction with p-nitrochlorobenzene as raw material.

2. experimental principle

preparation of p-nitroaniline is through the reduction of the chlorine atom in p-nitrochlorobenzene, the process of converting it to amino. The reducing agent can be selected from hydrogen, zinc powder, iron powder, etc. In this experiment, hydrogen was used as a reducing agent to achieve the reduction of p-nitrochlorobenzene through catalytic hydrogenation reaction.

3. Experimental steps

1. Pretreatment of p-nitrochlorobenzene

Add a certain amount of p-nitrochlorobenzene into a three-necked flask, add a small amount of zinc powder as a catalyst, heat and stir until the zinc powder is completely dissolved. Then, the mixture was cooled to room temperature with an ice water bath, and the insoluble matter was removed by filtration to obtain a pretreated p-nitrochlorobenzene solution.

2. Reduction reaction

Add the pretreated p-nitrochlorobenzene solution into an autoclave, introduce hydrogen, pressurize to a certain pressure, heat to a certain temperature, and start the reduction reaction. During the reaction, the temperature and pressure of the reaction solution should be continuously monitored to maintain a constant temperature and pressure.

3. Post-treatment

After completion of the reaction, the reaction mixture was cooled to room temperature, poured into a separatory funnel, and washed several times with water to remove acidic impurities. The pH is then adjusted to neutral with lye and washed again with water several times to obtain the crude p-nitroaniline.

4. Purification

The crude product was recrystallized from ethanol to give purified p-nitroaniline.

4. Experimental results and discussion

1. Experimental results

Through the collation and analysis of the experimental data, we have obtained the yield and purity data of p-nitroaniline.

2. Results Discussion The temperature and pressure of

reduction reaction are the key factors affecting the yield and purity of p-nitroaniline. Too high temperature and pressure may lead to the occurrence of side reactions and reduce the purity of the product; too low temperature and pressure may lead to incomplete reaction and reduce the yield of the product. Therefore, it is necessary to continuously optimize the reaction conditions in the experiment to obtain the best reaction effect. In addition, the amount of zinc powder used as a catalyst also needs to be properly controlled, and too much zinc powder may lead to excessive metal impurities in the product.

5. conclusion

Through the analysis and discussion of the experimental data, we draw the following conclusion: using p-nitrochlorobenzene as raw material, p-nitroaniline can be successfully prepared by catalytic hydrogenation reaction. During the experiment, it is necessary to control the temperature and pressure of the reduction reaction, as well as the amount of catalyst, in order to obtain p-nitroaniline products with high purity and high yield. The preparation method has the advantages of simple operation, easy access to raw materials and high product purity, and has certain industrial application value.

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