A method for improving the quality of 2,6-dichloro-4-trifluoromethylaniline

Abstract

The present invention relates to a method for separating and purifying a pesticide chemical product, in particular to a method for improving the quality of 2,6-dichloro-4-trifluoromethylaniline. First, a composite protective agent is added to the crude product of 2,6-dichloro-4-trifluoromethylaniline, and after mixing evenly, it is sent to a rectification device for vacuum rectification. The refined product of 2,6-dichloro-4-trifluoromethylaniline is obtained by rectification. The composite protective agent includes metal fluoride and amine compounds, which can inhibit the dechlorination of 2,6-dichloro-4-trifluoromethylaniline, greatly reduce the generation of impurities, and greatly improve the rectification yield of 2,6-dichloro-4-trifluoromethylaniline.

Description

Technical Field

[0001] The present invention relates to a method for separating and purifying a pesticide chemical product, in particular to a method for improving the quality of 2,6-dichloro-4-trifluoromethylaniline. Background Art

[0002] 2,6-Dichloro-4-trifluoromethylaniline is an important intermediate. Due to its unique biological activity of fluorine-containing aromatic compounds, it has received increasing attention and is widely used in the preparation of medicines and pesticides. Such as pesticides like Regent, Fluvalinate, and Chlorfluazuron. In addition, its diazonium salt can self-condense or condense with other compounds to form many useful dyes, insecticides, and herbicides.

[0003] During the rectification process of 2,6-dichloro-4-trifluoromethylaniline, dehalogenation easily occurs to produce hydrogen fluoride and hydrogen chloride, and hydrogen fluoride and hydrogen chloride will cause strong corrosion to the rectification equipment. At the same time, they will form amine salts with the amino group on 2,6-dichloro-4-trifluoromethylaniline and become impurities. The presence of these impurities reduces the rectification yield of 2,6-dichloro-4-trifluoromethylaniline.

[0004] For 2,6-dichloro-4-trifluoromethylaniline obtained by vacuum rectification, when the content of 2,6-dichloro-4-trifluoromethylaniline is measured by gas chromatography area normalization method, even if the content of 2,6-dichloro-4-trifluoromethylaniline reaches more than 99.5%, there are a small amount of needle-like crystalline suspensions visible to light in the product sample at normal temperature. These are crystalline substances of 2,6-dichloro-4-trifluoromethylaniline hydrochloride or hydrofluoride that precipitate.

[0005] Therefore, in the rectification process of 2,6-dichloro-4-trifluoromethylaniline, it is of great significance to reduce impurities and improve the rectification yield. Summary of the Invention

[0006] The purpose of the present invention is to overcome the defects of many impurities and low rectification yield in the rectification process of 2,6-dichloro-4-trifluoromethylaniline in the prior art, and provide a method for improving the quality of 2,6-dichloro-4-trifluoromethylaniline.

[0007] A method for improving the quality of 2,6-dichloro-4-trifluoromethylaniline. First, a composite protective agent is added to the crude product of 2,6-dichloro-4-trifluoromethylaniline and mixed evenly, and then it is sent to a rectification device for vacuum rectification. The refined product of 2,6-dichloro-4-trifluoromethylaniline is obtained by rectification. The composite protective agent includes metal fluoride and amine compound. By utilizing the property that each component in 2,6-dichloro-4-trifluoromethylaniline containing the composite protective agent has different volatilities, that is, the vapor pressures of each component are different at the same temperature, the light components in the liquid phase are transferred to the gas phase, and 2,6-dichloro-4-trifluoromethylaniline is rectified and separated. Adding a composite protective agent containing metal fluoride and amine compound, on the one hand, inhibits the dechlorination of 2,6-dichloro-4-trifluoromethylaniline. On the other hand, under the condition of heating, anhydrous potassium fluoride or anhydrous sodium fluoride in the composite protective agent will decompose slightly, and a thermal decomposition reaction occurs to release hydrogen fluoride gas. The hydrogen fluoride gas reacts with the amine compound in the protective agent to form amine fluoride after dehalogenation. At this time, the amine fluoride can also be used as an inhibitor to inhibit the dechlorination of 2,6-dichloro-4-trifluoromethylaniline during the rectification process of 2,6-dichloro-4-trifluoromethylaniline, reduce its reactivity, and improve the rectification yield of 2,6-dichloro-4-trifluoromethylaniline. To sum up, on the one hand, the metal fluoride and amine compound in the composite protective agent cooperate with each other to jointly inhibit the dechlorination of 2,6-dichloro-4-trifluoromethylaniline. This mutual cooperation is the main inhibition of the dechlorination of 2,6-dichloro-4-trifluoromethylaniline. On the other hand, under the heating condition, anhydrous potassium fluoride or anhydrous sodium fluoride decomposes slightly, and hydrogen fluoride gas is released after decomposition. The hydrogen fluoride gas reacts with the amine compound in the protective agent to form amine fluoride after dehalogenation, which can also be used as an inhibitor. The amine fluoride also inhibits the dechlorination of 2,6-dichloro-4-trifluoromethylaniline. This inhibition is the secondary inhibition of the dechlorination of 2,6-dichloro-4-trifluoromethylaniline. This dual inhibition of the dechlorination of 2,6-dichloro-4-trifluoromethylaniline greatly reduces the generation of impurities and greatly improves the rectification yield of 2,6-dichloro-4-trifluoromethylaniline.

[0008] The metal fluoride is anhydrous potassium fluoride or anhydrous sodium fluoride.

[0009] The metal fluoride is anhydrous potassium fluoride containing potassium hydroxide, and the dosage of potassium hydroxide is 5-10% of the mass of anhydrous potassium fluoride.

[0010] The metal fluoride is anhydrous sodium fluoride containing sodium hydroxide, and the dosage of sodium hydroxide is 5-10% of the mass of anhydrous sodium fluoride.

[0011] Add 5-10% potassium hydroxide to anhydrous potassium fluoride (or 5-10% sodium hydroxide to anhydrous sodium fluoride), and reduce the decomposition activity of anhydrous potassium fluoride (or anhydrous sodium fluoride) under heating conditions, so as to reduce the release of hydrogen fluoride gas and the formation of amine fluorides, which is beneficial to distilling out 2,6-dichloro-4-trifluoromethylaniline and improving the rectification efficiency of 2,6-dichloro-4-trifluoromethylaniline.

[0012] In the present invention, adding 5-10% potassium hydroxide to anhydrous potassium fluoride (or 5-10% sodium hydroxide to anhydrous sodium fluoride) is beneficial to reducing the yield of amine fluorides and weakening the inhibitory effect of amine fluorides, enabling anhydrous potassium fluoride (or anhydrous sodium fluoride) and amine compounds in the composite protective agent to synergistically inhibit the dechlorination of 2,6-dichloro-4-trifluoromethylaniline and playing a leading role in inhibiting the dechlorination of 2,6-dichloro-4-trifluoromethylaniline, which is one of the highlights of the present invention. Since the rectification of 2,6-dichloro-4-trifluoromethylaniline is carried out under heating conditions, this will cause trace decomposition of anhydrous potassium fluoride (or anhydrous sodium fluoride) in the composite protective agent. After decomposition, hydrogen fluoride gas is released, and the hydrogen fluoride gas reacts with amine compounds (such as one of N-phenyloctadecanamide, dioctadecylamine, and hexadecanamide ethanol) in the protective agent to form amine fluorides after dehalogenation, which can also be used as inhibitors. Amine fluorides also inhibit the dechlorination of 2,6-dichloro-4-trifluoromethylaniline, and this inhibition is the secondary aspect of the inhibition of the dechlorination of 2,6-dichloro-4-trifluoromethylaniline.

[0013] In order to give full play to the synergistic inhibition of anhydrous potassium fluoride (or anhydrous sodium fluoride) and amine compounds in the composite protective agent against the dechlorination of 2,6-dichloro-4-trifluoromethylaniline, 5-10% potassium hydroxide is added to anhydrous potassium fluoride (or 5-10% sodium hydroxide to anhydrous sodium fluoride). This will lead to a reduction in the generation of amine fluorides, weaken the inhibitory effect of amine fluorides, and enable anhydrous potassium fluoride (or anhydrous sodium fluoride) and amine compounds to synergistically inhibit and play the main inhibitory role. To sum up, adding 5-10% potassium hydroxide to anhydrous potassium fluoride (or 5-10% sodium hydroxide to anhydrous sodium fluoride) has the following three advantages: First, it is beneficial to reducing the decomposition activity of anhydrous potassium fluoride (or anhydrous sodium fluoride) under heating conditions, reducing the release of hydrogen fluoride gas, reducing the formation of amine fluorides, weakening the inhibitory effect of amine fluorides as inhibitors, and enabling anhydrous potassium fluoride and amine compounds to synergistically inhibit and play the main inhibitory role. Second, adding 5-10% potassium hydroxide to anhydrous potassium fluoride (or 5-10% sodium hydroxide to anhydrous sodium fluoride) is also beneficial to distilling out 2,6-dichloro-4-trifluoromethylaniline and improving the rectification efficiency of 2,6-dichloro-4-trifluoromethylaniline. Third, adding 5-10% potassium hydroxide to anhydrous potassium fluoride (or 5-10% sodium hydroxide to anhydrous sodium fluoride) makes the hydrogen fluoride generated by the decomposition activity of anhydrous potassium fluoride (or anhydrous sodium fluoride) under alkaline potassium hydroxide conditions preferentially undergo an acid-base reaction with the amine compound (one of N-phenyloctadecanamide, dioctadecylamine, hexadecanamide ethanol) to form the corresponding amine salt, rather than forming an amine salt with the amino group on 2,6-dichloro-4-trifluoromethylaniline to form impurities. Therefore, the generation of impurities is greatly reduced, and the rectification yield of 2,6-dichloro-4-trifluoromethylaniline is extremely improved.

[0014] The amine compound is one of N-phenyloctadecanamide, dioctadecylamine, and hexadecanamide ethanol. Experiments have shown that when the amine compound is N-phenyloctadecanamide, dioctadecylamine, or hexadecanamide ethanol, it is beneficial to improving the rectification efficiency of 2,6-dichloro-4-trifluoromethylaniline.

[0015] The dosage of the metal fluoride is 0.1-1% of the mass of the crude 2,6-dichloro-4-trifluoromethylaniline, which is beneficial to improving the rectification yield of 2,6-dichloro-4-trifluoromethylaniline.

[0016] The dosage of the amine compound is 0.1-15% of the mass of the crude 2,6-dichloro-4-trifluoromethylaniline, which is beneficial to improving the rectification yield of 2,6-dichloro-4-trifluoromethylaniline.

[0017] The dosage of the amine compound is 0.5-5% of the mass of the crude 2,6-dichloro-4-trifluoromethylaniline, which is beneficial to improving the rectification yield of 2,6-dichloro-4-trifluoromethylaniline.

[0018] The rectification device is a rectification column, and a reboiler is provided inside the rectification column. The bottom of the rectification column is heated by the reboiler.

[0019] The pressure of the vacuum rectification is ≤ -0.098 MPa, the top temperature of the rectification column is 110 - 118 °C, and the temperature of the reboiler is 120 - 130 °C. During the vacuum rectification process, maintaining a lower pressure helps to reduce the boiling point, making it easier to separate the components in the mixture to be separated. During the rectification process, the top temperature should be maintained between 110 - 118 °C. This temperature range is determined according to the properties of the crude 2,6-dichloro-4-trifluoromethylaniline containing the composite protective agent to ensure that the required product is collected at the top. The reboiler is a component in the rectification column used to provide thermal energy to reboil and re-separate some components in the mixture. The temperature range of 120 - 130 °C for the reboiler indicates the temperature range of the reboiler, which helps to provide sufficient heat to achieve the reboiling process.

[0020] The beneficial effects of the present invention compared with the prior art are as follows:

[0021] (1) During the rectification of 2,6-dichloro-4-trifluoromethylaniline, the successful introduction of the composite protective agent is also one of the highlights of the present invention! In the prior art, during the rectification of 2,6-dichloro-4-trifluoromethylaniline, dechlorination easily occurs, generating hydrogen fluoride and hydrogen chloride, which cause corrosion to the rectification equipment. The presence of various impurities during the rectification process is not conducive to the evaporation of 2,6-dichloro-4-trifluoromethylaniline, reducing the rectification yield of 2,6-dichloro-4-trifluoromethylaniline. To overcome the deficiencies in the prior art, the present invention has made bold improvements on the basis of the prior art and successfully introduced a suitable composite protective agent to double inhibit the dechlorination of 2,6-dichloro-4-trifluoromethylaniline, greatly reducing the generation of impurities and significantly improving the rectification yield of 2,6-dichloro-4-trifluoromethylaniline.

[0022] (2) Adding 5-10% potassium hydroxide to anhydrous potassium fluoride (or 5-10% sodium hydroxide to anhydrous sodium fluoride) is also the second highlight of the present invention! On the one hand, it enables anhydrous potassium fluoride and amine compounds to synergistically inhibit each other, playing the main role in inhibiting the dechlorination of 2,6-dichloro-4-trifluoromethylaniline. On the other hand, it is also conducive to distilling out 2,6-dichloro-4-trifluoromethylaniline and improving the rectification efficiency of 2,6-dichloro-4-trifluoromethylaniline. In addition, under the condition of alkaline potassium hydroxide, the hydrogen fluoride generated by the decomposition activity of anhydrous potassium fluoride (or anhydrous sodium fluoride) will preferentially undergo an acid-base reaction with an amine compound (one of N-phenyloctadecanamide, distearylamine, and hexadecanamide ethanol) to form the corresponding amine salt, rather than forming an amine salt with the amino group on 2,6-dichloro-4-trifluoromethylaniline to form impurities. Therefore, the generation of impurities is greatly reduced, and the rectification yield of 2,6-dichloro-4-trifluoromethylaniline is improved.

[0023] (3) The rectification process of the present invention is relatively simple, with easy control of process conditions, convenient operation, domestic and inexpensive raw materials, good repeatability, and low cost, making it very suitable for industrial production and having a bright prospect for popularization and application. Specific embodiments

[0024] The present invention will be further described below in conjunction with specific embodiments.

[0025] Example 1

[0026] A method for improving the quality of 2,6-dichloro-4-trifluoromethylaniline. First, 0.95 g of anhydrous potassium fluoride containing 0.05 g of potassium hydroxide and 1 g of N-phenyloctadecanamide are added to 1000 g of crude 2,6-dichloro-4-trifluoromethylaniline, and the mixture is stirred evenly. Then, it is sent to a rectification column equipped with a reboiler for vacuum rectification. The bottom of the rectification column is heated by the reboiler. The pressure of the vacuum rectification is -0.098 MPa, the top temperature of the rectification column is 110 °C, and the temperature of the reboiler is 120 °C. 963 g of 2,6-dichloro-4-trifluoromethylaniline is obtained by rectification. Based on the crude 2,6-dichloro-4-trifluoromethylaniline, the rectification yield of 2,6-dichloro-4-trifluoromethylaniline is 96.3%. The dosage of potassium hydroxide is 5% of the mass of anhydrous potassium fluoride, the dosage of anhydrous potassium fluoride containing potassium hydroxide is 0.1% of the mass of the crude 2,6-dichloro-4-trifluoromethylaniline, and the dosage of N-phenyloctadecanamide is 0.1% of the mass of the crude 2,6-dichloro-4-trifluoromethylaniline.

[0027] Example 2

[0028] A method for improving the quality of 2,6-dichloro-4-trifluoromethylaniline. First, 4.6 g of anhydrous sodium fluoride containing 0.4 g of sodium hydroxide and 50 g of dioctadecylamine are added to 1000 g of crude 2,6-dichloro-4-trifluoromethylaniline, and the mixture is stirred evenly. Then, it is fed into a distillation column equipped with a reboiler for vacuum distillation. The bottom of the distillation column is heated by the reboiler. The pressure of the vacuum distillation is -0.098 MPa, the top temperature of the distillation column is 115 °C, and the temperature of the reboiler is 125 °C. 956 g of 2,6-dichloro-4-trifluoromethylaniline is obtained by distillation. The amount of sodium hydroxide used is 8% of the mass of anhydrous sodium fluoride, the amount of anhydrous sodium fluoride containing sodium hydroxide used is 0.5% of the mass of the crude 2,6-dichloro-4-trifluoromethylaniline, and the amount of dioctadecylamine used is 5% of the mass of the crude 2,6-dichloro-4-trifluoromethylaniline. Based on the crude 2,6-dichloro-4-trifluoromethylaniline, the distillation yield of 2,6-dichloro-4-trifluoromethylaniline is 95.6%.

[0029] Example 3

[0030] A method for improving the quality of 2,6-dichloro-4-trifluoromethylaniline. First, 9 g of anhydrous potassium fluoride containing 1 g of potassium hydroxide and 150 g of N-hexadecylacetamide ethanol are added to 1000 g of crude 2,6-dichloro-4-trifluoromethylaniline, and the mixture is stirred evenly. Then, it is fed into a distillation column equipped with a reboiler for vacuum distillation. The bottom of the distillation column is heated by the reboiler. The pressure of the vacuum distillation is -0.098 MPa, the top temperature of the distillation column is 118 °C, and the temperature of the reboiler is 130 °C. 951 g of 2,6-dichloro-4-trifluoromethylaniline is obtained by distillation. The amount of potassium hydroxide used is 10% of the mass of anhydrous potassium fluoride, the amount of anhydrous potassium fluoride containing potassium hydroxide used is 1% of the mass of the crude 2,6-dichloro-4-trifluoromethylaniline, and the amount of N-hexadecylacetamide ethanol used is 15% of the mass of the crude 2,6-dichloro-4-trifluoromethylaniline. Based on the crude 2,6-dichloro-4-trifluoromethylaniline, the distillation yield of 2,6-dichloro-4-trifluoromethylaniline is 95.1%.

[0031] Example 4

[0032] A method for improving the quality of 2,6-dichloro-4-trifluoromethylaniline. First, 1 g of N-phenyloctadecanamide is added to 1000 g of crude 2,6-dichloro-4-trifluoromethylaniline and mixed evenly. Then it is sent to a distillation column equipped with a reboiler for vacuum distillation. The bottom of the distillation column is heated by the reboiler. The pressure of the vacuum distillation is -0.098 MPa, the top temperature of the distillation column is 110 °C, and the temperature of the reboiler is 120 °C. 753 g of 2,6-dichloro-4-trifluoromethylaniline is obtained by distillation. Based on the crude 2,6-dichloro-4-trifluoromethylaniline, the distillation yield of 2,6-dichloro-4-trifluoromethylaniline is 75.3%. The dosage of N-phenyloctadecanamide is 0.1% of the mass of the crude 2,6-dichloro-4-trifluoromethylaniline.

[0033] In Example 4, "0.95 g of anhydrous potassium fluoride containing 0.05 g of potassium hydroxide" in Example 1 is removed, and other components, dosages, and method steps remain unchanged.

[0034] Example 5

[0035] A method for improving the quality of 2,6-dichloro-4-trifluoromethylaniline. First, 0.95 g of anhydrous potassium fluoride containing 0.05 g of potassium hydroxide is added to 1000 g of crude 2,6-dichloro-4-trifluoromethylaniline and mixed evenly. Then it is sent to a distillation column equipped with a reboiler for vacuum distillation. The bottom of the distillation column is heated by the reboiler. The pressure of the vacuum distillation is -0.098 MPa, the top temperature of the distillation column is 110 °C, and the temperature of the reboiler is 120 °C. 801 g of 2,6-dichloro-4-trifluoromethylaniline is obtained by distillation. Based on the crude 2,6-dichloro-4-trifluoromethylaniline, the distillation yield of 2,6-dichloro-4-trifluoromethylaniline is 80.1%. The dosage of potassium hydroxide is 5% of the mass of anhydrous potassium fluoride, and the dosage of anhydrous potassium fluoride containing potassium hydroxide is 0.1% of the mass of the crude 2,6-dichloro-4-trifluoromethylaniline.

[0036] In Example 5, "and 1 g of N-phenyloctadecanamide" in Example 1 is removed, and other components, dosages, and method steps remain unchanged.

[0037] It can be seen from Examples 4 - 5 that the method of Example 4 does not contain potassium hydroxide-free potassium fluoride, and the rectification yield of 2,6-dichloro-4-trifluoromethylaniline is 75.3%. The method of Example 5 does not contain N-phenyloctadecanamide, and the rectification yield of 2,6-dichloro-4-trifluoromethylaniline is 80.1%. Therefore, in the method for improving the quality of 2,6-dichloro-4-trifluoromethylaniline, the lack of any component in the composite protective agent will result in a relatively low rectification yield of 2,6-dichloro-4-trifluoromethylaniline. It can be seen from Examples 1 - 3 that the rectification yield of 2,6-dichloro-4-trifluoromethylaniline is as high as over 95%. This is because the metal fluoride and amine compound in the composite protective agent cooperate with each other to jointly inhibit the dechlorination of 2,6-dichloro-4-trifluoromethylaniline. This mutual cooperation is the main inhibition of the dechlorination of 2,6-dichloro-4-trifluoromethylaniline. On the other hand, under heating conditions, trace amounts of potassium fluoride or sodium fluoride decompose slightly, and hydrogen fluoride gas is released after decomposition. The hydrogen fluoride gas forms amine fluoride after dehalogenation with the amine compound in the protective agent, which can also act as an inhibitor. The amine fluoride also inhibits the dechlorination of 2,6-dichloro-4-trifluoromethylaniline. This inhibition is the secondary inhibition of the dechlorination of 2,6-dichloro-4-trifluoromethylaniline. This dual inhibition of the dechlorination of 2,6-dichloro-4-trifluoromethylaniline greatly reduces the generation of impurities and greatly improves the rectification yield of 2,6-dichloro-4-trifluoromethylaniline.

[0038] Example 6

[0039] A method for improving the quality of 2,6-dichloro-4-trifluoromethylaniline. First, 1 g of potassium fluoride and 1 g of N-phenyloctadecanamide are added to 1000 g of crude 2,6-dichloro-4-trifluoromethylaniline and mixed evenly. Then, it is sent to a rectification column equipped with a reboiler for vacuum rectification. The bottom of the rectification column is heated by the reboiler. The pressure of the vacuum rectification is -0.098 MPa, the top temperature of the rectification column is 110 °C, and the temperature of the reboiler is 120 °C. 645 g of 2,6-dichloro-4-trifluoromethylaniline is obtained by rectification. Based on the crude 2,6-dichloro-4-trifluoromethylaniline, the rectification yield of 2,6-dichloro-4-trifluoromethylaniline is 64.5%. The dosage of potassium fluoride is 0.1% of the mass of the crude 2,6-dichloro-4-trifluoromethylaniline, and the dosage of N-phenyloctadecanamide is 0.1% of the mass of the crude 2,6-dichloro-4-trifluoromethylaniline.

[0040] In Example 6, "containing 0.05 g of potassium hydroxide" in Example 1 is removed, and other components, dosages, and method steps remain unchanged.

[0041] Example 7

[0042] A method for improving the quality of 2,6-dichloro-4-trifluoromethylaniline. First, 0.87 g of anhydrous potassium fluoride containing 0.13 g of potassium hydroxide and 1 g of N-phenyloctadecanamide are added to 1000 g of crude 2,6-dichloro-4-trifluoromethylaniline, and the mixture is stirred evenly. Then, it is fed into a rectification column equipped with a reboiler for vacuum rectification. The bottom of the rectification column is heated by the reboiler. The pressure of vacuum rectification is -0.098 MPa, the top temperature of the rectification column is 110 °C, and the temperature of the reboiler is 120 °C. After rectification, 668 g of 2,6-dichloro-4-trifluoromethylaniline is obtained. Based on the crude 2,6-dichloro-4-trifluoromethylaniline, the rectification yield of 2,6-dichloro-4-trifluoromethylaniline is 66.8%. The dosage of potassium hydroxide is 15% of the mass of anhydrous potassium fluoride, the dosage of anhydrous potassium fluoride containing potassium hydroxide is 0.1% of the mass of crude 2,6-dichloro-4-trifluoromethylaniline, and the dosage of N-phenyloctadecanamide is 0.1% of the mass of crude 2,6-dichloro-4-trifluoromethylaniline.

[0043] In Example 7, “the dosage of potassium hydroxide is 5% of the mass of anhydrous potassium fluoride” in Example 1 is changed to “the dosage of potassium hydroxide is 15% of the mass of anhydrous potassium fluoride”, and other components, dosages, and method steps remain unchanged.

[0044] Example 8

[0045] A method for improving the quality of 2,6-dichloro-4-trifluoromethylaniline. First, 5 g of anhydrous sodium fluoride and 50 g of dioctadecylamine are added to 1000 g of crude 2,6-dichloro-4-trifluoromethylaniline, and the mixture is stirred evenly. Then, it is fed into a rectification column equipped with a reboiler for vacuum rectification. The bottom of the rectification column is heated by the reboiler. The pressure of vacuum rectification is -0.098 MPa, the top temperature of the rectification column is 115 °C, and the temperature of the reboiler is 125 °C. After rectification, 686 g of 2,6-dichloro-4-trifluoromethylaniline is obtained. The dosage of anhydrous sodium fluoride is 0.5% of the mass of crude 2,6-dichloro-4-trifluoromethylaniline, and the dosage of dioctadecylamine is 5% of the mass of crude 2,6-dichloro-4-trifluoromethylaniline. Based on the crude 2,6-dichloro-4-trifluoromethylaniline, the rectification yield of 2,6-dichloro-4-trifluoromethylaniline is 68.6%.

[0046] In Example 8, “containing 0.4 g of sodium hydroxide” in Example 2 is removed, and other components, dosages, and method steps remain unchanged.

[0047] Example 9

[0048] A method for improving the quality of 2,6-dichloro-4-trifluoromethylaniline. First, add 4.17 g of anhydrous sodium fluoride containing 0.83 g of sodium hydroxide and 50 g of dioctadecylamine to 1000 g of crude 2,6-dichloro-4-trifluoromethylaniline, mix evenly, and then send it to a rectifying column equipped with a reboiler for vacuum rectification. The bottom of the rectifying column is heated by the reboiler. The pressure of the vacuum rectification is -0.098 MPa, the top temperature of the rectifying column is 115 °C, and the temperature of the reboiler is 125 °C. 674 g of 2,6-dichloro-4-trifluoromethylaniline is obtained by rectification. The dosage of sodium hydroxide is 20% of the mass of anhydrous sodium fluoride, the dosage of anhydrous sodium fluoride containing sodium hydroxide is 0.5% of the mass of crude 2,6-dichloro-4-trifluoromethylaniline, and the dosage of dioctadecylamine is 5% of the mass of crude 2,6-dichloro-4-trifluoromethylaniline. Based on the crude 2,6-dichloro-4-trifluoromethylaniline, the rectification yield of 2,6-dichloro-4-trifluoromethylaniline is 67.4%.

[0049] In Example 9, “the dosage of sodium hydroxide is 8% of the mass of anhydrous sodium fluoride” in Example 2 is changed to “the dosage of sodium hydroxide is 20% of the mass of anhydrous sodium fluoride”, and other components, dosages, and method steps remain unchanged.

[0050] In Example 6, anhydrous potassium fluoride does not contain potassium hydroxide, and the rectification yield of 2,6-dichloro-4-trifluoromethylaniline is 64.5%; in Example 7, anhydrous potassium fluoride contains potassium hydroxide and the dosage of potassium hydroxide is 15% of the mass of anhydrous potassium fluoride, and the rectification yield of 2,6-dichloro-4-trifluoromethylaniline is 66.8%; in Example 8, anhydrous sodium fluoride does not contain sodium hydroxide, and the rectification yield of 2,6-dichloro-4-trifluoromethylaniline is 68.6%; in Example 9, anhydrous sodium fluoride contains sodium hydroxide and the dosage of sodium hydroxide is 20% of the mass of anhydrous sodium fluoride, and the rectification yield of 2,6-dichloro-4-trifluoromethylaniline is 67.4%. It is known that during the rectification of 2,6-dichloro-4-trifluoromethylaniline, when anhydrous potassium fluoride does not contain potassium hydroxide, or anhydrous potassium fluoride contains potassium hydroxide and the dosage of potassium hydroxide is not 5-10% of the mass of anhydrous potassium fluoride, or when anhydrous sodium fluoride does not contain sodium hydroxide, or anhydrous sodium fluoride contains sodium hydroxide and the dosage of sodium hydroxide is not 5-10% of the mass of anhydrous sodium fluoride, it will all lead to a low rectification yield of 2,6-dichloro-4-trifluoromethylaniline.

[0051] Therefore, it is necessary to add potassium hydroxide to anhydrous potassium fluoride or sodium hydroxide to anhydrous sodium fluoride. In addition, under the conditions of potassium hydroxide or sodium hydroxide, especially when the dosage of potassium hydroxide is 5-10% of the mass of anhydrous potassium fluoride or the dosage of sodium hydroxide is 5-10% of the mass of anhydrous sodium fluoride, the hydrogen fluoride generated by the decomposition activity of anhydrous potassium fluoride (or anhydrous sodium fluoride) will preferentially undergo an acid-base reaction with an amine compound (one of N-phenyloctadecanamide, dioctadecylamine, and hexadecanamide ethanol) to form a corresponding amine salt, rather than forming an amine salt with the amino group on 2,6-dichloro-4-trifluoromethylaniline to form impurities. Therefore, the generation of impurities is greatly reduced, and the rectification yield of 2,6-dichloro-4-trifluoromethylaniline is improved. The dosage of potassium hydroxide being 5-10% of the mass of anhydrous potassium fluoride or the dosage of sodium hydroxide being 5-10% of the mass of anhydrous sodium fluoride also has the following other advantages: First, it is beneficial to reduce the decomposition activity of anhydrous potassium fluoride (or anhydrous sodium fluoride) under heating conditions, reduce the release of hydrogen fluoride gas, reduce the formation of amine fluorides, and weaken the inhibitory effect of amine fluorides as inhibitors. In this way, anhydrous potassium fluoride and amine compounds synergistically inhibit each other and play the main inhibitory role. Second, adding 5-10% potassium hydroxide to anhydrous potassium fluoride (or 5-10% sodium hydroxide to anhydrous sodium fluoride) is also beneficial for distilling out 2,6-dichloro-4-trifluoromethylaniline and improving the rectification efficiency of 2,6-dichloro-4-trifluoromethylaniline.

[0052] Example 10

[0053] Replace the anhydrous potassium fluoride in Example 1 with potassium fluoride, and keep other components, dosages, and steps unchanged. Based on the crude product of 2,6-dichloro-4-trifluoromethylaniline, the rectification yield of 2,6-dichloro-4-trifluoromethylaniline is 78.6%.

[0054] Example 11

[0055] Replace the anhydrous sodium fluoride in Example 2 with sodium fluoride, and keep other components, dosages, and steps unchanged. Based on the crude product of 2,6-dichloro-4-trifluoromethylaniline, the rectification yield of 2,6-dichloro-4-trifluoromethylaniline is 76.2%.

[0056] From Examples 10-11, it can be seen that when using anhydrous potassium fluoride or anhydrous sodium fluoride, it helps to improve the rectification yield of 2,6-dichloro-4-trifluoromethylaniline.

[0057] The above are only some embodiments of the present invention, and do not impose any formal restrictions on the present invention. Any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention all fall within the scope of the technical solutions of the present invention.

Claims

1. A method for improving the quality of 2,6-dichloro-4-trifluoromethylaniline, characterized in that: First, a composite protective agent is added to the crude 2,6-dichloro-4-trifluoromethylaniline, and the mixture is stirred evenly. Then, it is sent to a rectification device for vacuum rectification to obtain the refined 2,6-dichloro-4-trifluoromethylaniline. The composite protective agent includes metal fluoride and amine compounds. The metal fluoride is anhydrous potassium fluoride containing potassium hydroxide, and the dosage of potassium hydroxide is 5-10% of the mass of anhydrous potassium fluoride. The metal fluoride is anhydrous sodium fluoride containing sodium hydroxide, and the dosage of sodium hydroxide is 5-10% of the mass of anhydrous sodium fluoride. The amine compound is one of N-phenyloctadecanamide, dioctadecylamine, and hexadecanamide ethanol.

2. A method for improving the quality of 2,6-dichloro-4-trifluoromethylaniline according to claim 1, characterized in that: The dosage of the metal fluoride is 0.1-1% of the mass of the crude 2,6-dichloro-4-trifluoromethylaniline.

3. A method for improving the quality of 2,6-dichloro-4-trifluoromethylaniline according to claim 1, characterized in that: The dosage of the amine compound is 0.1-15% of the mass of the crude 2,6-dichloro-4-trifluoromethylaniline.

4. A method for improving the quality of 2,6-dichloro-4-trifluoromethylaniline according to claim 3, characterized in that: The dosage of the amine compound is 0.5-5% of the mass of the crude 2,6-dichloro-4-trifluoromethylaniline.

5. A method for improving the quality of 2,6-dichloro-4-trifluoromethylaniline according to claim 1, characterized in that: The rectification device is a rectification column, and a reboiler is installed in the rectification column. The bottom of the rectification column is heated by the reboiler.

6. A method for improving the quality of 2,6-dichloro-4-trifluoromethylaniline according to claim 5, characterized in that: The pressure of the vacuum rectification is ≤ -0.098 MPa, the top temperature of the rectification column is 110-118 °C, and the temperature of the reboiler is 120-130 °C.