A method for preparing trifluoroethanol

Abstract

The present invention relates to the technical field of organic synthesis, and specifically to a preparation method of trifluoroethanol, which comprises the following steps: S1 Add 2-chloro-1,1-difluoroethyl 2,2,2-trifluoroethyl ether into a reaction kettle, and while stirring, dropwise add concentrated sulfuric acid at a certain reaction temperature. After the dropping is completed, continue to keep the temperature for reaction until the reaction is complete to obtain the compound shown in Formula I; S2 Add water into a reaction vessel, and dropwise add the compound shown in Formula I prepared in step S1 into the reaction vessel for hydrolysis reaction. After the reaction is completed, let it stand for stratification, and the lower layer is 2,2,2-trifluoroethyl chloroacetate; S3 Add 2,2,2-trifluoroethyl chloroacetate and an aqueous potassium hydroxide solution into the reaction vessel in sequence, and after the reaction is completed, rectify to obtain the product trifluoroethanol; The reaction involved in the present invention is carried out at a lower temperature and under normal pressure, and the equipment used in the reaction is conventional ordinary equipment, which is simple and easy to operate and suitable for industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of organic synthesis, and particularly to a preparation method of trifluoroethanol. Background Art

[0002] 2,2,2-Trifluoroethanol, CAS No.: 75-89-8, boiling point: 77-80 °C, is an important aliphatic fluorine-containing intermediate, a colorless liquid miscible with water, with an odor similar to ethanol. Due to the strong electron-withdrawing effect of the trifluoromethyl group, it has different properties from other alcohols and can participate in a variety of organic chemical reactions. It can be oxidized to trifluoroacetaldehyde or trifluoroacetic acid, and is used to synthesize trifluoroacetic acid derivatives, fluorinated ether anesthetics, fluorinated pharmaceuticals (such as flucardium), fluorinated pesticides, and working media for waste heat recovery power generation systems, etc.

[0003] In the 1933 US Patent US2982789, Swarts used trifluoroacetic anhydride as a raw material to obtain trifluoroethanol through catalytic reduction. However, trifluoroacetic anhydride is prone to deep reduction, generating hemiacetals, esters, acids, and even hydrocarbons. Other methods include: trifluoroacetic acid method, trifluoroacetate method, trifluoroacetaldehyde method, trifluoroacetyl chloride method, vinylidene fluoride method, 1,1,1-trifluoroethane (HFC-143a) method, and 1,1,2-trifluoro-1-chloroethane (HCFC-133a) method, but each has its own defects, as follows:

[0004] The trifluoroacetic acid method uses rhodium, rubidium, iridium, etc. as catalysts for the reaction of trifluoroacetic acid with hydrogen to produce trifluoroethanol. However, due to the deep reduction of trifluoroacetic acid, a certain amount of by-products such as trifluoroethane, ethane, and methane are generated;

[0005] The trifluoroacetate method uses trifluoroacetate as a raw material and reacts with hydrogen under the action of a metal oxide catalyst to produce trifluoroethanol. However, the reaction products are not easily separated, the conversion rate is low, and the catalyst needs to be repeatedly activated;

[0006] The trifluoroacetaldehyde method is that derivatives of trifluoroacetaldehyde react with hydrogen in the presence of a catalyst palladium / carbon and a cocatalyst aliphatic tertiary amine to produce trifluoroethanol. However, the raw material trifluoroacetaldehyde is itself more expensive than trifluoroethanol, which has no practical significance;

[0007] The trifluoroacetyl chloride method uses trifluoroacetyl chloride as a raw material and obtains trifluoroethanol through catalytic hydrogenation reduction reaction. The catalyst used in the reaction is expensive and has a short lifespan. Since both trifluoroacetyl chloride and by-product hydrogen chloride are gases, it is not easy to cause high raw material consumption;

[0008] The vinylidene fluoride method is that vinylidene fluoride is oxidized by oxygen in the presence of a catalyst to produce trifluoroethanol. However, the raw material vinylidene fluoride is difficult to obtain, and it is prone to polymerization, which will cause the catalyst to quickly lose its activity. Moreover, vinylidene fluoride and the oxidant will form an explosion limit, which is unsafe in operation;

[0009] The method using 1,1,1-trifluoroethane (HFC-143a) is that 1,1,1-trifluoroethane (HFC-143a) is oxidized by oxygen under the initiation of fluorine gas to produce trifluoroethanol. However, the initiator fluorine gas has a high price, is highly toxic and dangerous. Moreover, both the reaction conversion rate and selectivity are not ideal.

[0010] The method using 1-chloro-1,1,2-trifluoroethane (HCFC-133a) is that 1-chloro-1,1,2-trifluoroethane (HCFC-133a) reacts with an alkali metal salt of a carboxylic acid such as potassium acetate in the presence of solvents DMSO, DMF, sulfolane, N-methylpyrrolidone to carry out an esterification reaction to produce a carboxylic acid ester of trifluoroethanol, and then hydrolyze it in alkaline water to obtain trifluoroethanol. The reaction needs to be carried out under high temperature and high pressure conditions, has strong corrosion, and requires high equipment requirements. Summary of the Invention

[0011] The object of the present invention is to provide a preparation method of trifluoroethanol to solve at least one of the above technical problems.

[0012] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0013] A preparation method of trifluoroethanol, the preparation method comprising the following steps:

[0014] S1 Add 2-chloro-1,1-difluoroethyl-2,2,2-trifluoroethyl ether to a reaction kettle, and while stirring, dropwise add concentrated sulfuric acid at a certain reaction temperature. After the dropwise addition is completed, continue to keep the temperature for reaction until the reaction is complete to obtain a compound shown in formula I;

[0015]

[0016] S2 Add water to a reaction vessel, and at a certain temperature, dropwise add the compound shown in formula I prepared in step S1 to the reaction vessel for hydrolysis reaction. After the reaction is completed, let it stand for stratification, and the lower layer is 2,2,2-trifluoroethyl chloroacetate;

[0017] S3 Add 2,2,2-trifluoroethyl chloroacetate and an aqueous solution of potassium hydroxide to the reaction vessel in sequence, stir and react for a period of time, and then distill and rectify to obtain the product trifluoroethanol.

[0018] Further, when dropping the concentrated sulfuric acid in step S1, the reaction temperature is controlled to be 10-100 °C, the concentration of the concentrated sulfuric acid is 90%-98%, and after the dropwise addition of the concentrated sulfuric acid, the reaction temperature is controlled to be 30 °C for continuous reaction.

[0019] Further, when dropping the concentrated sulfuric acid in step S1, the reaction temperature is controlled to be 20-60 °C, and the concentration of the concentrated sulfuric acid is 90%-96%.

[0020] Further, the molar ratio of 2-chloro-1,1-difluoroethyl 2,2,2-trifluoroethyl ether to 95% concentrated sulfuric acid is 1:1 to 2.

[0021] Further, the molar ratio of 2-chloro-1,1-difluoroethyl 2,2,2-trifluoroethyl ether to 95% concentrated sulfuric acid is 1:1.5.

[0022] Further, the temperature of the hydrolysis reaction in step S2 is less than 30 °C.

[0023] Further, the mass percentage of potassium hydroxide in step S3 is 20%.

[0024] The beneficial effects of adopting the technical solution of the present invention are as follows:

[0025] The reaction involved in the present invention is carried out at a relatively low temperature and under normal pressure. The equipment used in the reaction is conventional and ordinary equipment, which is simple and easy to operate and suitable for industrial production.

[0026] All the raw materials used in the present invention are conventional raw materials without special requirements; no additional catalyst is added during the reaction, and the reaction situation can be detected at any time, enabling the reaction to be completely reacted at one time and avoiding secondary recovery treatment, thereby reducing the loss of raw materials. Description of the Drawings

[0027] Figure 1 It is the mass spectrum of the chloroacetic acid 2,2,2-trifluoroethyl ester compound prepared in the present invention.

[0028] Figure 2 It is the gas chromatogram of the chloroacetic acid 2,2,2-trifluoroethyl ester compound prepared in Example 1. Detailed Embodiments

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0030] The raw materials in the present invention are all commercially available.

[0031] 2-chloro-1,1-difluoroethyl 2,2,2-trifluoroethyl ether 99% (Jiangsu Blue Planet Environmental Protection Technology Co., Ltd.).

[0032] A preparation method of trifluoroethanol, the preparation method comprising the following steps:

[0033] S1 Add 2-chloro-1,1-difluoroethyl 2,2,2-trifluoroethyl ether into a reaction kettle. At a certain reaction temperature, while stirring, slowly add concentrated sulfuric acid drop by drop. After the addition is completed, continue to keep the temperature for reaction until the reaction is complete to obtain the compound shown in Formula I;

[0034] S2 Add water into a reaction vessel. At a certain temperature, slowly add the compound shown in Formula I prepared in step S1 into the reaction vessel for hydrolysis reaction. After the reaction is completed, let it stand for stratification. The lower layer is 2,2,2-trifluoroethyl chloroacetate;

[0035] S3 Add 2,2,2-trifluoroethyl chloroacetate and an aqueous solution of potassium hydroxide into a reaction vessel in sequence. After stirring and reacting for a period of time, distill and rectify to obtain the product trifluoroethanol.

[0036] The reaction principle of the present invention is as follows:

[0037]

[0038] Reaction formula (1)

[0039] Reaction formula (1) reveals the reaction process of 2-chloro-1,1-difluoroethyl 2,2,2-trifluoroethyl ether reacting with concentrated sulfuric acid to form a sulfate compound.

[0040]

[0041] Formula I

[0042]

[0043] Reaction formula (2) and reaction formula (3) reveal the reaction process of the sulfate compound generated in reaction formula (1) reacting with water to form 2,2,2-trifluoroethyl chloroacetate.

[0044]

[0045] Reaction formula (4) is the process of the alkaline hydrolysis of 2,2,2-trifluoroethyl chloroacetate to generate trifluoroethanol, potassium glycolate, and potassium chloride.

[0046] The above four reaction formulas elaborate in detail the process of 2-chloro-1,1-difluoroethyl 2,2,2-trifluoroethyl ether reacting with concentrated sulfuric acid to form the corresponding sulfate compound, the sulfate compound reacting with water and further reacting to form an ester and then undergoing alkaline hydrolysis to trifluoroethanol, providing a new method for the preparation of trifluoroethanol.

[0047] Figure 1 This is the mass spectrum of the 2,2,2-trifluoroethyl chloroacetate compound prepared in the present invention.

[0048] Figure 2Gas chromatogram of the chloroacetic acid - 2,2,2 - trifluoroethyl ester compound prepared in Example 1.

[0049] Example 1

[0050] Add 200 g of 2 - chloro - 1,1 - difluoroethyl - 2,2,2 - trifluoroethyl ether to a 1 - liter carbon steel stirred reaction kettle. While stirring, add dropwise 156 g of concentrated sulfuric acid with a concentration of 95%. Control the reaction temperature below 50°C. After the addition is completed, maintain the temperature at about 30°C and stir - react for 4 hours to obtain a sulfate product with a yield of 99%. During the reaction process, the tail gas is absorbed by water.

[0051] Add 350 g of water to a 1 - liter four - necked glass flask with stirring. Dropwise add the sulfate compound prepared by the reaction into the reaction flask, and control the reaction temperature below 30°C with a water bath. After the addition is completed, let it stand for liquid - liquid separation, and separate out 173 g of the lower - layer organic matter, with the content of chloroacetic acid - 2,2,2 - trifluoroethyl ester being 99.2%.

[0052] Add the prepared chloroacetic acid - 2,2,2 - trifluoroethyl ester and 540 g of 20% potassium hydroxide aqueous solution to a 1 - liter glass flask in sequence. After stirring for 1 hour, distill, and collect the fraction before the kettle temperature reaches 103°C, which is an aqueous solution of trifluoroethanol. Then, rectify to remove water to obtain 95 g of trifluoroethanol with a content of 99%. After a series of treatments such as dehydration, crystallization, filtration, and recrystallization of the aqueous solution in the flask, potassium chloride and potassium hydroxyacetate can be separated out.

[0053] Example 2

[0054] Add 300 g of 2 - chloro - 1,1 - difluoroethyl - 2,2,2 - trifluoroethyl ether to a 1 - liter carbon steel stirred reaction kettle. While stirring, add dropwise 300 g of concentrated sulfuric acid with a concentration of 98%. Control the reaction temperature below 60°C. After the addition is completed, maintain the temperature at about 30°C and stir - react for 4 hours to obtain a sulfate product with a yield of 99%. During the reaction process, the tail gas is absorbed by water.

[0055] Add 600 g of water to a 2 - liter four - necked glass flask with stirring. Dropwise add the sulfate compound prepared by the reaction into the reaction flask, and control the reaction temperature below 30°C with a water bath. After the addition is completed, let it stand for liquid - liquid separation, and separate out 257 g of the lower - layer organic matter, with the content of chloroacetic acid - 2,2,2 - trifluoroethyl ester being 98.5%.

[0056] Add the prepared chloroacetic acid - 2,2,2 - trifluoroethyl ester and 805 g of 20% potassium hydroxide aqueous solution to a 1 - liter glass flask in sequence. After stirring for 1 hour, distill, and collect the fraction before the kettle temperature reaches 103°C, which is an aqueous solution of trifluoroethanol. Then, rectify to remove water to obtain 141 g of trifluoroethanol with a content of 99%. After a series of treatments such as dehydration, crystallization, filtration, and recrystallization of the aqueous solution in the flask, potassium chloride and potassium hydroxyacetate can be separated out.

[0057] Example 3

[0058] 580 g of 2-chloro-1,1-difluoroethyl 2,2,2-trifluoroethyl ether was added to a 2-L carbon steel stirred reactor. While stirring, 375 g of concentrated sulfuric acid with a concentration of 92% was added dropwise. The reaction temperature was controlled below 60 °C. After the addition was completed, the temperature was maintained at about 30 °C and stirred for 4 h to obtain a sulfate product with a yield of 99%. During the reaction process, the tail gas was absorbed by water.

[0059] 900 g of water was added to a 2-L four-necked glass flask with stirring. The sulfate compound obtained from the reaction was added dropwise into the reaction flask, and the reaction temperature was controlled below 30 °C using a water bath. After the addition was completed, the mixture was allowed to stand and separate into layers. 495 g of the lower organic layer was separated, and the content of 2,2,2-trifluoroethyl chloroacetate was 98%.

[0060] The prepared 2,2,2-trifluoroethyl chloroacetate and 1540 g of an aqueous potassium hydroxide solution with a content of 20% were successively added to a 2-L glass flask. After stirring for 1 h, distillation was carried out, and the fraction before the kettle temperature reached 103 °C was collected, which was an aqueous solution of trifluoroethanol. After rectification to remove water, 273 g of trifluoroethanol with a content of 99% was obtained. After a series of treatments including dehydration, crystallization, filtration, and recrystallization of the aqueous solution in the flask, potassium chloride and potassium hydroxyacetate could be separated out.

[0061] Example 4

[0062] 2000 g of ************** was added to a 5-L stirred autoclave lined with polytetrafluoroethylene. While stirring, 504 g of concentrated sulfuric acid with a concentration of 98% was added dropwise. The reaction temperature was controlled below 60 °C. After the addition was completed, the temperature was maintained at about 30 °C and stirred for 2 h to obtain a sulfate product. The reaction device was adjusted to a distillation device, and 183 g of water was added dropwise to the stirred autoclave. The temperature was maintained at 40 °C during the addition. After the addition was completed, stirring was continued for 2 h, and then the temperature was raised for distillation. 1727 g of 2,2,2-trifluoroethyl chloroacetate with a boiling point of 60-62 °C and a content of 98.8% was collected. After the sulfuric acid in the stirred autoclave cooled, it could be used as a raw material for the production of sulfate compounds again.

[0063] The prepared 2,2,2-trifluoroethyl chloroacetate and 5480 g of an aqueous potassium hydroxide solution with a content of 20% were successively added to a 10-L glass flask. After stirring for 1 h, distillation was carried out, and the fraction before the kettle temperature reached 103 °C was collected, which was an aqueous solution of trifluoroethanol. After rectification to remove water, 978 g of trifluoroethanol with a content of 99% was obtained. After a series of treatments including dehydration, crystallization, filtration, and recrystallization of the aqueous solution in the flask, potassium chloride and potassium hydroxyacetate could be separated out.

[0064] It should be noted that there is an unclear part in the original text at "2000 g of **************", which needs to be further clarified for a more accurate translation.In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent claim. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing trifluoroethanol, characterized in that: The preparation method comprises the following steps: S1: Add 2-chloro-1,1-difluoroethyl 2,2,2-trifluoroethyl ether into a reaction kettle. While stirring, dropwise add concentrated sulfuric acid at a certain reaction temperature. After the dropping is completed, continue to keep the temperature for reaction until the reaction is complete to obtain the compound shown in Formula I; S2: Add water into a reaction vessel. Dropwise add the compound shown in Formula I prepared in step S1 into the reaction vessel at a certain temperature for hydrolysis reaction. After the reaction is completed, let it stand for stratification. The lower layer is 2,2,2-trifluoroethyl chloroacetate; S3: Add 2,2,2-trifluoroethyl chloroacetate and an aqueous potassium hydroxide solution into the reaction vessel in sequence. After stirring and reacting for a period of time, distill and rectify to obtain the product trifluoroethanol.

2. The preparation method of trifluoroethanol according to claim 1, characterized in that: In step S1, when dropping the concentrated sulfuric acid, control the reaction temperature at 10-100 °C, the concentration of the concentrated sulfuric acid is 90%-98%, and after the dropping of the concentrated sulfuric acid is completed, control the reaction temperature at 30 °C to continue the reaction.

3. The preparation method of trifluoroethanol according to claim 2, characterized in that: In step S1, when dropping the concentrated sulfuric acid, control the reaction temperature at 20-60 °C, and the concentration of the concentrated sulfuric acid is 90%-96%.

4. The preparation method of trifluoroethanol according to claim 1, characterized in that: The molar ratio of 2-chloro-1,1-difluoroethyl 2,2,2-trifluoroethyl ether to 95% concentrated sulfuric acid is 1:1-2.

5. The preparation method of trifluoroethanol according to claim 4, characterized in that: The molar ratio of 2-chloro-1,1-difluoroethyl 2,2,2-trifluoroethyl ether to 95% concentrated sulfuric acid is 1:1.

5.

6. The preparation method of trifluoroethanol according to claim 1, characterized in that: In step S2, the temperature of the hydrolysis reaction is less than 30 °C.

7. The preparation method of trifluoroethanol according to claim 1, characterized in that: In step S3, the mass percentage content of potassium hydroxide is 20%.

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