A method for efficiently purifying and separating 2-chloro-4-trifluoromethylphenol

Abstract

The present invention relates to a method for purifying and separating 2-chloro-4-trifluoromethylphenol, and belongs to the field of chemical industry. The method comprises the following steps: mixing a mixture containing 2-chloro-4-trifluoromethylphenol with water or an aqueous solvent, forming a 2-chloro-4-trifluoromethylphenol hydrate in a separated solid form at a certain temperature, and obtaining a purified 2-chloro-4-trifluoromethylphenol product. The method provided by the present invention can simply and effectively separate and purify 2-chloro-4-trifluoromethylphenol from a mixture containing 2-chloro-4-trifluoromethylphenol or a mixture of 2-chloro-4-trifluoromethylphenol and its isomers, avoids the use of large amounts of organic solvents and acids and bases, saves energy consumption, and is environmentally friendly.

Description

Technical Field

[0001] The present invention relates to the field of chemical industry, and more particularly to a method for purifying and separating 2-chloro-4-trifluoromethylphenol. Background Art

[0002] 2-Chloro-4-trifluoromethylphenol is a significant byproduct of the dietherification process for producing oxyfluorfen (US Pat. No. 4,046,798). In recent years, several patents have reported its use in the preparation of oxyfluorfen (CN101891623, CN109280008, CN109970567, and CN102030655). Effectively recycling this byproduct, 2-chloro-4-trifluoromethylphenol, is of great significance and value. However, according to comprehensive literature, 2-chloro-4-trifluoromethylphenol often coexists with isomers of 2-chloro-4-trifluoromethylphenol during its production process, and these isomers can participate in parallel reactions to generate isomers of the target compound. This necessitates further purification, which in turn increases input and waste generation, ultimately impacting the reaction yield.

[0003] Since 2-chloro-4-trifluoromethylphenol is a liquid at room temperature and has a very low freezing point, it is difficult to purify by conventional crystallization methods. It generally needs to be purified by column separation and distillation. The process requires a large amount of solvent and equipment investment, is costly and has a cumbersome process.

[0004] U.S. Patent WO2018185559 discloses a separation method for converting 2-chloro-4-trifluoromethylphenol into a salt form and filtering out isomers. This method reduces purification costs, but still requires the addition of a large amount of base and the steps of salt formation and re-acidification to obtain pure 2-chloro-4-trifluoromethylphenol. The input of acid and the production of salt are inevitable in this process, which also has disadvantages. Summary of the Invention

[0005] 1. Technical problems to be solved

[0006] In view of the problems existing in the prior art, the object of the present invention is to provide a method for separating and purifying 2-chloro-4-trifluoromethylphenol without the need for column separation, rectification or alkali salt formation.

[0007] 2. Technical solution

[0008] To solve the above problems, the present invention adopts the following technical solutions.

[0009] A method for efficiently purifying and separating 2-chloro-4-trifluoromethylphenol comprises mixing a mixture containing 2-chloro-4-trifluoromethylphenol (hereinafter referred to as the phenol mixture) with water or a water-containing solvent to form a solid 2-chloro-4-trifluoromethylphenol hydrate, and separating and obtaining a purified 2-chloro-4-trifluoromethylphenol product.

[0010] The mixture of 2-chloro-4-trifluoromethylphenol contains isomers of 2-chloro-4-trifluoromethylphenol and a solvent.

[0011] Furthermore, the isomers of 2-chloro-4-trifluoromethylphenol contained in the phenol mixture are 2-chloro-3-trifluoromethylphenol, 2-chloro-5-trifluoromethylphenol, 2-chloro-6-trifluoromethylphenol, 3-chloro-2-trifluoromethylphenol, 3-chloro-4-trifluoromethylphenol, 3-chloro-5-trifluoromethylphenol, 3-chloro-6-trifluoromethylphenol, 4-chloro-2-trifluoromethylphenol and 4-chloro-3-trifluoromethylphenol, and their isomer structures are shown in the figure:

[0012] Furthermore, the ratio of 2-chloro-4-trifluoromethylphenol contained in the phenol mixture to the isomers of 2-chloro-4-trifluoromethylphenol contained in the phenol mixture is 1000:1-1:1000.

[0013] Furthermore, the content of 2-chloro-4-trifluoromethylphenol in the phenol mixture is preferably ≥60%.

[0014] Furthermore, the weight of water as a reactant in the water or water-containing solvent is 0.5-30 times the weight of 2-chloro-4-trifluoromethylphenol in the mixture of 2-chloro-4-trifluoromethylphenol.

[0015] Furthermore, the aqueous solvent is a mixture of water and a non-polar solvent, wherein the non-polar solvent includes n-hexane, n-heptane, cyclohexane, methylcyclohexane, ether, petroleum ether, chloroform, dichloroethane and toluene and any combination thereof.

[0016] Furthermore, the phenol mixture needs to be mixed with water or a water-containing solvent at a certain temperature, which is -16-16°C.

[0017] Furthermore, the separation method includes but is not limited to filtration and centrifugation. In the separation method, the solvent used for filtering the filter cake can be water and a non-polar solvent, wherein the non-polar solvent includes but is not limited to n-hexane, cyclohexane, petroleum ether, chloroform, dichloroethane and toluene. The amount of the non-polar solvent will affect the yield, and the temperature of the non-polar solvent is below the crystallization temperature of the hydrate.

[0018] Furthermore, the temperature is -16°C to 16°C, preferably -4°C to 12°C.

[0019] 3. Beneficial effects

[0020] Compared with the prior art, the advantages of the present invention are:

[0021] (1) The present invention utilizes the property that 2-chloro-4-trifluoromethylphenol forms a solid hydrate with water at low temperature, separates the hydrate solid, and obtains a purified 2-chloro-4-trifluoromethylphenol product, which greatly reduces the complexity of the purification and separation process of 2-chloro-4-trifluoromethylphenol;

[0022] (2) The final product of the present invention is a purified white solid 2-chloro-4-trifluoromethylphenol hydrate. Since the solid needs to be stored at low temperatures, has a small contact area, is easy to package, and has low volatility, once the hydrate is formed, it will not decompose and cause corrosion as long as the temperature is guaranteed. However, the final product of the prior art is a liquid, which is volatile and produces odor. It will slowly decompose and produce acid and fluoride ions, causing equipment corrosion. Therefore, the use of this solution can greatly reduce the source of odor and the corrosion of phenol on equipment;

[0023] (3) The solvents used in the separation and purification process of the present invention are water and non-polar solvents, which avoids the use of large amounts of organic solvents and acids and bases, and greatly reduces the three wastes discharged during the industrial production process;

[0024] (4) The present invention uses simple equipment in the separation and purification process, and does not require the use of complex equipment such as high-temperature distillation. It is simple, efficient, energy-saving and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The spectrum of the phenol mixture containing isomers before purification and the gas phase normalized ratio data of the present invention;

[0026] Figure 2 The spectrum and gas phase normalized ratio data of the phenol mixture containing only isomers before purification of the present invention;

[0027] Figure 3 The figure and ratio data of the purified phenol product of the present invention;

[0028] Figure 4 The figure shows the spectrum and ratio data of the purified product with almost no isomers in the present invention. DETAILED DESCRIPTION

[0029] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0030] In the embodiment, in the phenol mixture of 2-chloro-4-trifluoromethylphenol and the isomers of 2-chloro-4-trifluoromethylphenol, the ratio of 2-chloro-4-trifluoromethylphenol to the isomers of 2-chloro-4-trifluoromethylphenol in the phenol mixture is 1000:1 to 1:1000; in the 2-chloro-4-trifluoromethylphenol hydrate obtained by purification in the embodiment, the ratio of 2-chloro-4-trifluoromethylphenol to the isomers of 2-chloro-4-trifluoromethylphenol in the hydrate is 93:2 to 9 9.99:0.01, the purity of 2-chloro-4-trifluoromethylphenol in the purified hydrate is above 97%, and can be as high as higher than 99.9%; the best way to mix the phenol mixture with water or an aqueous solvent is to add the phenol mixture dropwise to water or an aqueous solvent to obtain a better crystal form, and the mixing method has no effect on the reaction itself; the 2-chloro-4-trifluoromethylphenol hydrate obtained in the examples is generally white flaky or blocky crystals, and in some cases the hydrate is a white powdery solid.

[0031] See also Figure 1-4 ,Will Figure 1 The data of the ratio of the phenol mixture containing isomers before purification in the present invention are Figure 3 Compared with the proportion data of the phenol product after purification according to the technical solution adopted by the present invention, it can be seen from the change in its peak area that the concentration of 2-chloro-4-trifluoromethylphenol in the phenol mixture increases from 15.744% to 95.389% in the purified phenol product;

[0032] Will Figure 2 The data of the proportion of the phenol mixture containing only isomers before purification in the present invention are Figure 3 By comparing the proportion data of the phenol products after purification according to the technical solution adopted in the present invention, it can be seen from the change in its peak area that the concentration of 2-chloro-4-trifluoromethylphenol in the phenol mixture increases from 80.678% to 98.389% of the 2-chloro-4-trifluoromethylphenol concentration in the purified phenol product.

[0033] Will Figure 1 The ratio data of the phenol mixture containing isomers before purification in the present invention is Figure 4 Compared with the proportion data of the purified product with almost no isomers obtained according to the technical solution, it can be seen from the change in its peak area that the concentration of 2-chloro-4-trifluoromethylphenol in the phenol mixture increases from 15.744% to 100.000% of the 2-chloro-4-trifluoromethylphenol concentration in the purified phenol product with almost no isomers;

[0034] Will Figure 2 The data of the proportion of the phenol mixture containing only isomers before purification in the present invention are Figure 4Compared with the proportion data of the purified product with almost no isomers obtained according to the technical solution, it can be seen from the change in its peak area that the concentration of 2-chloro-4-trifluoromethylphenol in the phenol mixture increases from 80.678% to 100.000% in the purified phenol product with almost no isomers. The comparison of the data further demonstrates the excellent purity of the final product obtained by the technical solution of the present invention.

[0035] Example 1:

[0036] A method for purifying and separating 2-chloro-4-trifluoromethylphenol comprises the following steps:

[0037] S1. Add 50g of water to a 250ml four-necked flask and cool to 6°C;

[0038] S2. A mixture of 30 g (0.15 mol) of 2-chloro-4-trifluoromethylphenol and isomers of 2-chloro-5-trifluoromethylphenol was added dropwise to the cooled water. A white solid precipitated in the water during the addition process.

[0039] S3. After the addition was completed, the phenol mixture in a 250ml four-necked flask was stirred and insulated for 10min;

[0040] S4. The stirred phenol mixture was filtered, and the filter cake was washed with water. After filtration, 32 g of hydrate of 2-chloro-4-trifluoromethylphenol was obtained, wherein the ratio of 2-chloro-4-trifluoromethylphenol to the isomer 2-chloro-5-trifluoromethylphenol was 97.2:1.9.

[0041] Example 2:

[0042] A method for purifying and separating 2-chloro-4-trifluoromethylphenol comprises the following steps:

[0043] S1. Add 50g of water to a 250ml four-necked flask and cool to 6°C;

[0044] S2. A mixture of 30 g (0.15 mol) of 2-chloro-4-trifluoromethylphenol and isomers of 2-chloro-5-trifluoromethylphenol was added dropwise to the cooled water. A white solid precipitated in the water during the addition process.

[0045] S3. After the addition was completed, the phenol mixture in a 250ml four-necked flask was stirred and insulated for 10min;

[0046] S4. The stirred phenol mixture was filtered, and the filter cake was washed with n-hexane at a temperature below the hydrate crystallization temperature. After filtration, 29.5 g of hydrate of 2-chloro-4-trifluoromethylphenol was obtained, wherein the ratio of 2-chloro-4-trifluoromethylphenol to the isomer 2-chloro-5-trifluoromethylphenol was 97.8:0.6.

[0047] Example 3:

[0048] A method for purifying and separating 2-chloro-4-trifluoromethylphenol comprises the following steps:

[0049] S1. Add 30g of n-hexane and 20g of water to a 250ml four-necked flask and cool to 9°C.

[0050] S2. To the cooled mixture was added dropwise a mixture of 30 g (0.15 mol) of 2-chloro-4-trifluoromethylphenol and isomers of 2-chloro-5-trifluoromethylphenol, and a white solid precipitate appeared in the water during the addition process;

[0051] S3. After the addition was completed, the phenol mixture in a 250ml four-necked flask was stirred and insulated for 10min;

[0052] S4. The stirred phenol mixture was filtered, and the filter cake was washed with n-hexane at a temperature below the hydrate crystallization temperature. After filtration, 26.8 g of hydrate of 2-chloro-4-trifluoromethylphenol was obtained, wherein the ratio of 2-chloro-4-trifluoromethylphenol to the isomer 2-chloro-5-trifluoromethylphenol was 99.8:0.01.

[0053] Comparative Example 1:

[0054] A method for purifying and separating 2-chloro-4-trifluoromethylphenol by column chromatography comprises the following steps:

[0055] S1. A mixture of 3 g (0.015 mol) of 2-chloro-4-trifluoromethylphenol and its isomers 2-chloro-5-trifluoromethylphenol was purified and separated by column chromatography;

[0056] S2. Take 80g of petroleum ether and 130g of ethyl acetate mixed to different proportions of elution solvent to elute the sample;

[0057] S3. The samples received in separate bottles were collected and desolventized according to their test results, ultimately yielding 1.8 g of a pale yellow liquid mixture of 2-chloro-4-trifluoromethylphenol and its isomer, 2-chloro-5-trifluoromethylphenol, in a ratio of 99.3:0.2, and 1.2 g of an elution solvent mixture. This method is complex and requires separate collection and desolventization based on the test results of the samples received in separate bottles. This method requires a large amount of solvent, resulting in high costs, and produces excessive amounts of ineffective waste. The resulting product is a volatile, odorous liquid, which means the product will decompose to produce acid and fluoride ions, which can corrode equipment.

[0058] Comparative Example 2:

[0059] A method for separating 2-chloro-4-trifluoromethylphenol by salt formation comprises the following steps:

[0060] S1. Add 400g toluene, 25g ethanol, 15g water and 90g potassium hydroxide flakes to a 1000ml four-necked flask, stir for 1h and cool to 20°C;

[0061] S2. Add 300 g (1.5 mol) of a mixture of 2-chloro-4-trifluoromethylphenol and isomers of 2-chloro-5-trifluoromethylphenol dropwise at 15-22 ° C. After the addition is complete, stir and heat for 3 h.

[0062] S3. Filter and rinse the filter cake with 50 g of toluene to obtain 360 g of an off-white solid 2-chloro-4-trifluoromethylphenol potassium salt hydrate wet product, wherein the water content is 18.15%, and the ratio of 2-chloro-4-trifluoromethylphenol and the isomer 2-chloro-5-trifluoromethylphenol is 93:0.6.

[0063] S4. Add the above 2-chloro-4-trifluoromethylphenol potassium salt hydrate to a 1000ml four-necked flask, add 400g of toluene and stir;

[0064] S5. 30% hydrochloric acid was added dropwise to a 1000 ml four-necked flask at a temperature below 40° C. until the pH was below 2, consuming 162 g of hydrochloric acid. After standing for stratification, the flask was washed with 50 g of water. The upper layer was desolvated with a toluene solution to obtain 246 g of 2-chloro-4-trifluoromethylphenol, wherein the ratio of 2-chloro-4-trifluoromethylphenol to the isomer 2-chloro-5-trifluoromethylphenol was 98:0.8. This method involves the use of a large amount of organic solvent, a strongly alkaline compound, and a strongly acidic mixture, resulting in excessive discharge of three wastes and industrial pollution, which is not conducive to the development of subsequent environmental protection work.

Claims

1. A method for purifying and separating 2-chloro-4-trifluoromethylphenol, characterized in that: A mixture containing 2-chloro-4-trifluoromethylphenol is mixed with water or a water-containing solvent to form a solid 2-chloro-4-trifluoromethylphenol hydrate, and a purified 2-chloro-4-trifluoromethylphenol product is separated. The isomers of 2-chloro-4-trifluoromethylphenol contained in the 2-chloro-4-trifluoromethylphenol mixture are 2-chloro-3-trifluoromethylphenol, 2-chloro-5-trifluoromethylphenol, 2-chloro-6-trifluoromethylphenol, 3-chloro-2-trifluoromethylphenol, 3-chloro-4-trifluoromethylphenol, 3-chloro-5-trifluoromethylphenol, 3-chloro-6-trifluoromethylphenol, 4-chloro-2-trifluoromethylphenol and 4-chloro-3-trifluoromethylphenol.

2. A method for purifying and separating 2-chloro-4-trifluoromethylphenol according to claim 1, characterized in that: The ratio of 2-chloro-4-trifluoromethylphenol contained in the 2-chloro-4-trifluoromethylphenol mixture to the isomers of 2-chloro-4-trifluoromethylphenol contained in the 2-chloro-4-trifluoromethylphenol mixture is 1000:1-1:1000.

3. A method for purifying and separating 2-chloro-4-trifluoromethylphenol according to claim 2, characterized in that: The content of 2-chloro-4-trifluoromethylphenol in the 2-chloro-4-trifluoromethylphenol mixture is ≥60%.

4. A method for purifying and separating 2-chloro-4-trifluoromethylphenol according to claim 1, characterized in that: The weight of water as a reactant in the water or water-containing solvent is 0.5-30 times the weight of 2-chloro-4-trifluoromethylphenol in the mixture of 2-chloro-4-trifluoromethylphenol.

5. A method for purifying and separating 2-chloro-4-trifluoromethylphenol according to claim 1, characterized in that: The aqueous solvent is a mixture of water and a non-polar solvent, wherein the non-polar solvent includes n-hexane, n-heptane, cyclohexane, methylcyclohexane, ether, petroleum ether, chloroform, dichloroethane and toluene and any combination thereof.

6. A method for purifying and separating 2-chloro-4-trifluoromethylphenol according to claim 1, characterized in that: The mixture containing 2-chloro-4-trifluoromethylphenol needs to be mixed with water or a water-containing solvent at a certain temperature, which is -16-16°C.

7. A method for purifying and separating 2-chloro-4-trifluoromethylphenol according to claim 1, characterized in that: The separation method is filtration or centrifugation.

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