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Preparation method of 3,4,5-trifluoroaniline

A technology of trifluoroaniline and trifluoronitrobenzene, which is applied in the field of preparation methods, can solve the problems of ineffective fluorine removal by-products, too much waste water, and inability to effectively control fluorine-removal by-products, etc., to achieve inhibition The effect of losing and reducing the production of fluorine by-products

Active Publication Date: 2018-12-07
BENGBU CHINA SYNCHEM TECH CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] 3,4,5-trifluoronitrobenzene, through nitro reduction to prepare 3,4,5-trifluoroaniline, there are many methods, which can be reduced by iron powder (this method has too much waste water, and the country has banned the use of iron powder for nitration base reduction), and methods such as palladium carbon reduction, nickel reduction, ruthenium reduction, and platinum reduction can also be used, but the method cannot be carried out for fluorine removal by-products (such as m-difluoroaniline, o-difluoroaniline, monofluoroaniline, etc.) Effective control
[0004] In the prior art, there is no effective means to suppress the occurrence of by-products of fluorine removal

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0028] A kind of preparation method of 3,4,5-trifluoroaniline comprises the steps:

[0029] (1) Disperse 50g of 3,4,5-trifluoronitrobenzene with a gas chromatography purity of 99.2wt%, a maximum single impurity content of 0.03%, and a fluorine-off impurity content of 40ppm in 500g of pure water, and add 10g of ruthenium carbon (5wt% carbon-loaded ruthenium) and 5g tetrabutylammonium fluoride as a catalyst, heated to 150°C for 12h under a hydrogen atmosphere with a hydrogen pressure of 4.5MPa, to obtain a crude product;

[0030] (2) The crude product was extracted twice with 200 g of dichloromethane, and after the organic phase was distilled off under normal pressure to remove the solvent, a rectification under reduced pressure was performed according to the number of plates of 1500 to obtain 3,4,5-trifluoroaniline.

[0031] The obtained 3,4,5-trifluoroaniline was subjected to gas chromatography-mass spectrometry (conditions: 1°C / min to 150°C from 80°C, 20°C / min to 280°C) to te...

Embodiment 2

[0048] The only difference from Example 1 is that the gas chromatography purity of 3,4,5-trifluoronitrobenzene is 99.1wt%, the maximum single impurity content is 0.06%, and the fluorine-removed impurity content is 65ppm.

[0049] Gas chromatography-mass spectrometry (conditions: 1°C / min to 150°C from 80°C, 20°C / min to 280°C) to test the obtained 3,4,5-trifluoroaniline (peaking time: 45.5min), the purity The impurity is 99.25%, and the impurity is 3,5-difluoroaniline (peak elution time is 45.1min, confirmed by comparison of 3,5-difluoroaniline and standard impurity), [M]: 129.04, the content is 55ppm.

Embodiment 3～6

[0051] The difference with Example 1 is only that the number of theoretical plates of step (2) vacuum distillation is 1000 (Example 3), 2000 (Example 4), 800 (Example 5), 2200 (Example 6) .

[0052] Gas chromatography-mass spectrometry (conditions: 1°C / min to 150°C from 80°C, 20°C / min to 280°C) measured the purity of the obtained 3,4,5-trifluoroaniline to be 99.08% (Example 3 ), 99.91% (Example 4), 98.95% (Example 5), 99.92% (Example 6).

[0053] As can be seen from the results of the examples and comparative examples, the mixture of ruthenium carbon and tetrabutylammonium fluoride with a mass ratio of 1.8 to 2.2:1 is used as a catalyst to catalytically reduce 3,4,5-trifluoronitrobenzene, The fluorine removal by-product content is ≤ 50ppm, and the purity of the 3,4,5-trifluoroaniline ≥ 99% can be achieved only through one rectification.

[0054] It can be seen from the comparative examples that when the catalyst does not select the mixture of ruthenium carbon and tetrabutyla...

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PUM

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Abstract

The invention relates to a preparation method of 3,4,5-trifluoroaniline. The preparation method comprises the following steps: (1) dispersing 3,4,5-trifluoro nitro benzene into water, adding a catalyst, and heating in a hydrogen atmosphere for reaction, so as to obtain a crude product, wherein the catalyst is a mixture of ruthenium carbon and tetrabutylammonium fluoride in a mass ratio of (1.8-2.2) to 1, and ruthenium carbon is counted based on 5% carbon-loaded ruthenium; and (2) extracting the crude product by virtue of dichloromethane, and carrying out primary reduced pressure rectificationon an organic phase, so as to obtain 3,4,5-trifluoroaniline. According to the synthesis method provided by the invention, a specific catalyst is selected, so that the generation of fluorine-generatingimpurities in the process of preparing 3,4,5-trifluoroaniline through 3,4,5-trifluoro nitro benzene can be reduced, and the purity of 3,4,5-trifluoroaniline is improved; and particularly, when the catalyst is the mixture of ruthenium carbon and tetrabutylammonium fluoride in a mass ratio of 2 to 1 and the plate number in every 50g of 3,4,5-trifluoroaniline on a rectifying tower is 1000-2000, thepurity of 3,4,5-trifluoroaniline is 99% or above.

Description

technical field [0001] The invention belongs to the field of intermediate synthesis, and in particular relates to a preparation method of 3,4,5-trifluoroaniline. Background technique [0002] 3,4,5-Trifluoroaniline is an important raw material for the preparation of liquid crystal materials. 3,4,5-Trifluoroaniline can be prepared through a series of reactions such as diazotization, bromination, Grignard reaction, boration, etc., to prepare 3,4 ,5-Trifluorophenylboronic acid. Raw materials for liquid crystal materials, in order to ensure the purity of liquid crystal materials, have very strict requirements on congeners. Generally, the impurities of congeners are required to be less than 50ppm. Therefore, it is necessary to control the impurities of congeners from the raw materials used in each step. [0003] 3,4,5-trifluoronitrobenzene, through nitro reduction to prepare 3,4,5-trifluoroaniline, there are many methods, which can be reduced by iron powder (this method has too ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C07C211/52C07C209/36C07C209/84
CPCC07C209/365C07C209/84C07C211/52
Inventor 徐剑霄赵士民张浩
Owner BENGBU CHINA SYNCHEM TECH CO LTD
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