A kind of preparation method of trifluoroacetic acid

Abstract

The invention belongs to the technical field of organic synthesis, specifically a method for preparing trifluoroacetic acid, wherein 2-chloro-1,1,1-trifluoroethane is used as a raw material, and under visible light irradiation, 2-chloro-1,1,1-trifluoroethane is oxidized by a hypochlorous acid compound and an acid solution to obtain trifluoroacetic acid. The invention uses 2-chloro-1,1,1-trifluoroethane, a freon waste gas, as a raw material, and trifluoroacetic acid is prepared by a one-step method, providing a new method for preparing trifluoroacetic acid with simple process, low cost, green environmental protection, and easy industrial large-scale production, overcoming the technical defects of the prior art method for preparing trifluoroacetic acid, and being suitable for industrial large-scale preparation of trifluoroacetic acid.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis, and specifically relates to a method for preparing trifluoroacetic acid. Background Art

[0002] Trifluoroacetic acid is an organic compound with the chemical formula C2HF3O2. It is a colorless volatile fuming liquid with a similar smell to acetic acid, hygroscopic and pungent odor. Trifluoroacetic acid is strongly acidic due to the electron-withdrawing trifluoromethyl group, and its acidity is 100,000 times stronger than acetic acid. Trifluoroacetic acid is a good solvent for many organic compounds. When used in combination with carbon disulfide, it can dissolve proteins. It is also an excellent solvent for organic reactions, and can obtain results that are difficult to obtain in general organic solvents. For example, when quinoline is catalytically hydrogenated in general solvents, the pyridine ring is preferentially hydrogenated, but in trifluoroacetic acid, the benzene ring is preferentially hydrogenated. Trifluoroacetic acid is also used to synthesize fluorine-containing compounds, pesticides and dyes. It is a catalyst for esterification and condensation reactions, a protective agent for hydroxyl and amino groups, and can also be used in the synthesis of sugars and polypeptides, as well as a mineral processing agent.

[0003] There are many routes for preparing trifluoroacetic acid. The currently known routes are:

[0004] 1. 3,3,3-trifluoropropene is oxidized with potassium permanganate to obtain trifluoroacetic acid. During the oxidation process, potassium permanganate is required as an oxidant, and a large amount of manganese salt and hydrogen chloride will be produced during the reaction, which causes great pollution and high post-processing costs.

[0005] 2. Using acetic acid, acetyl chloride or acetic anhydride as raw materials, electrochemical fluorination is carried out with hydrofluoric acid or sodium fluoride, and then hydrolyzed to obtain trifluoroacetic acid; the electrochemical fluorination synthesis route consumes a lot of energy due to the introduction of electrochemistry, and the reaction process requires the use of hydrofluoric acid, which has a pungent odor and is highly toxic, resulting in poor environmental protection of the reaction route.

[0006] 3. 1,1,1-trifluoro-2,3,3-trichloropropene is oxidized with potassium permanganate to obtain trifluoroacetic acid; 1,1,1-trifluoro-2,3,3-trichloropropene is prepared by Swarts fluorination of hexachloropropene. The synthesis of 1,1,1-trifluoro-2,3,3-trichloropropene is relatively complicated and the reaction economy is poor.

[0007] 4. Oxidation of 2,3-dichlorohexafluoro-2-butene to produce trifluoroacetic acid; 2,3-dichlorohexafluoro-2-butene is highly toxic, and potassium permanganate is required as an oxidant during the reaction, resulting in the generation of by-products manganese salts and hydrogen chloride, and the subsequent treatment cost is very high.

[0008] 5. First, trichloroacetonitrile is reacted with hydrogen fluoride to generate trifluoroacetonitrile, and then trifluoroacetonitrile is hydrolyzed to obtain trifluoroacetic acid. This process requires the use of highly toxic hydrofluoric acid, which is highly corrosive and has poor environmental protection.

[0009] 6. Using m-trifluoromethylaniline chromic acid as raw material, trifluoroacetic acid is obtained by oxidation; the price of m-trifluoromethylaniline chromic acid is relatively expensive and cannot be adapted to industrial production.

[0010] 7. Using 2-chloro-1,1,1-trifluoroethane as raw material, trifluoroacetic acid is prepared through a multi-step reaction under the catalytic action of a catalyst; the multi-step reaction preparation process has cumbersome operating steps, complex processes, and expensive catalysts, all of which lead to increased costs and make industrial production impossible.

[0011] It can be seen from the analysis that in the above-mentioned prior art preparation method, from the perspective of raw materials, since 2-chloro-1,1,1-trifluoroethane is a component of Freon waste and is a greenhouse gas with a very strong greenhouse effect, it has a strong destructive effect on the atmosphere. Therefore, consuming 2-chloro-1,1,1-trifluoroethane and synthesizing trifluoroacetic acid is the best solution. However, the current preparation of trifluoroacetic acid using 2-chloro-1,1,1-trifluoroethane as a raw material has complicated steps and requires a catalyst, which is not suitable for industrial large-scale production; and other methods are also not suitable for industrial large-scale production of trifluoroacetic acid due to raw material, environmental protection and cost issues. Summary of the invention

[0012] In view of the above-mentioned deficiencies in the prior art, the present invention provides a method for preparing trifluoroacetic acid. The method of the present invention uses 2-chloro-1,1,1-trifluoroethane as a raw material, and uses a hypochlorous acid compound and an acid solution to oxidize 2-chloro-1,1,1-trifluoroethane under visible light irradiation to obtain trifluoroacetic acid. The present invention uses 2-chloro-1,1,1-trifluoroethane, a freon waste gas, as a raw material, and uses a one-step method to obtain trifluoroacetic acid, providing a new method for preparing trifluoroacetic acid with simple process, low cost, green environmental protection, and easy industrial large-scale production, which overcomes the technical defects of the prior art method for preparing trifluoroacetic acid.

[0013] The present invention is achieved through the following technical solutions:

[0014] A method for preparing trifluoroacetic acid comprises the following steps:

[0015] Under visible light irradiation, a hypochlorous acid compound and 2-chloro-1,1,1-trifluoroethane are mixed, and then acid solution is added in batches, and the hypochlorous acid compound and the acid solution are used to oxidize 2-chloro-1,1,1-trifluoroethane to obtain trifluoroacetic acid. The present invention performs the reaction under visible light irradiation, and visible light irradiation realizes the conversion of chlorine gas into chlorine free radicals, while the conversion cannot be achieved under the condition of no light, which in turn affects the subsequent reactions. Therefore, the experiment cannot be carried out under the condition of no light, and the target product trifluoroacetic acid cannot be obtained.

[0016] Preferably, the mass ratio of 2-chloro-1,1,1-trifluoroethane, hypochlorous acid compound and acid solution is 1-5:1:0.1-10. In order to achieve complete reaction, and because 2-chloro-1,1,1-trifluoroethane is a gas, it is easy to collect, and the product is liquid trifluoroacetic acid. Therefore, when conducting the experiment, the mass ratio of 2-chloro-1,1,1-trifluoroethane to hypochlorous acid compound is equal to or higher than 1:1, that is, an excess of 2-chloro-1,1,1-trifluoroethane is used to achieve complete reaction; in addition, the acid solution is commercially available sulfuric acid or hydrochloric acid of known concentration, and its mass is calculated according to the formula Calculated.

[0017] Preferably, the oxidation conditions are: stirring the reaction at room temperature for 8 hours to 24 hours. If the stirring time is less than 8 hours, the reaction is incomplete and there is residual raw material. If the reaction time is too long, it will bring challenges to energy consumption.

[0018] Preferably, the wavelength of visible light is 200nm to 600nm, which is strong blue light. Under strong blue light, chlorine gas is converted into chlorine free radicals, and the intensity of irradiation has little effect on the reaction.

[0019] Preferably, the hypochlorous acid compound is hypochlorous acid or hypochlorite, and the hypochlorite ion in the hypochlorous acid compound is used for the reaction.

[0020] Preferably, the hypochlorite is selected from sodium hypochlorite or calcium hypochlorite.

[0021] Preferably, the hypochlorite is selected from sodium hypochlorite pentahydrate. Comparative studies have shown that the yield of trifluoroacetic acid obtained by reacting with sodium hypochlorite pentahydrate as a raw material is the highest and is significantly better than other hypochlorous acid compounds.

[0022] Preferably, the acid solution is selected from sulfuric acid solution or hydrochloric acid solution, and the acid solution is obtained by experimental screening.

[0023] Preferably, when the acid solution is selected from a sulfuric acid solution, the concentration of the sulfuric acid solution is 0.1 mol / L to 16.8 mol / L, and the concentration of the sulfuric acid solution has little effect on the oxidation performance.

[0024] Preferably, when the acid solution is selected from a hydrochloric acid solution, the concentration of the hydrochloric acid solution is 0.1 mol / L to 12 mol / L, and the concentration of the hydrochloric acid solution has little effect on the oxidation performance.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention uses 2-chloro-1,1,1-trifluoroethane as a raw material, and uses acid and hypochlorous acid compounds to oxidize 2-chloro-1,1,1-trifluoroethane under light conditions, and oxidizes 2-chloro-1,1,1-trifluoroethane in situ to trifluoroacetic acid. The oxidation process of the present invention involves a free radical process, specifically: hypochlorite reacts rapidly with acid to generate corresponding metal salts and hypochlorous acid, and releases heat, hypochlorous acid is unstable and undergoes a disproportionation reaction to generate hydrogen chloride and chloric acid, and chloric acid can decompose to generate chlorine, perchloric acid, oxygen and water. Chlorine is converted into chlorine free radicals under light conditions, and the chlorine free radicals and 2-chloro-1,1,1-trifluoroethane undergo a free radical chlorination process to generate trifluorotrichloroethane, and trifluorotrichloroethane is oxidized by an oxidizing substance generated in situ to generate trifluoroacetic acid, wherein the oxide may be oxygen, chlorine, hypochlorous acid, chloric acid, and perchloric acid.

[0027] The present invention proposes a one-step method for preparing trifluoroacetic acid. The reaction does not require complicated multi-step operations, and the reaction process does not require the participation of a catalyst. Trifluoroacetic acid can be synthesized in one step under light conditions, and the preparation of trifluoroacetic acid can be achieved at room temperature. The entire step is simple, efficient, and has a high yield. Therefore, in terms of the preparation method, the preparation of trifluoroacetic acid of the present invention is suitable for industrial production.

[0028] 2. The present invention provides a new method for preparing trifluoroacetic acid, wherein the raw materials are hypochlorous acid compounds, acid solution and 2-chloro-1,1,1-trifluoroethane, wherein 2-chloro-1,1,1-trifluoroethane is a component of freon waste, a greenhouse gas with a strong greenhouse effect, and has a strong destructive effect on the atmosphere; any hypochlorite that can provide hypochlorite ions can be applied to the present invention, thereby realizing the secondary utilization of hypochlorous acid compound waste; the concentration of the acid solution has little effect on the oxidation performance, and the cost is low. The present invention realizes the transformation of waste into treasure while solving the problem of environmental pollution, so in terms of raw materials, the preparation of trifluoroacetic acid of the present invention is suitable for industrial production.

[0029] The preparation method of the invention is green and environmentally friendly. After the reaction is completed, a mixture of sodium salt, water, trifluorotrichloroethane and trifluoroacetic acid is generated. Trifluorotrichloroethane is a liquid. During the distillation process, trifluorotrichloroethane and trifluoroacetic acid are separated, so that trifluorotrichloroethane is collected while purifying trifluoroacetic acid. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is the fluorine spectrum of trifluoroacetic acid prepared in Example 2 of the present invention.

[0031] Figure 2This is the carbon spectrum of trifluoroacetic acid obtained in Example 2 of the present invention.

[0032] Figure 3 Figure (a) shows the spectrum of trifluoroacetic acid with the carbon peak at 162.7 ppm. Figure 3 Figure (b) is the spectrum of the carbon peak of trifluoroacetic acid at 113.7 ppm.

[0033] Figure 4 This is a high-resolution mass spectrum of trifluoroacetic acid obtained in Example 2 of the present invention.

[0034] Figure 5 It is a schematic diagram of the preparation principle of trifluoroacetic acid of the present invention.

[0035] Figure 6 This is the fluorine spectrum of the by-product CF3CCl3 distilled out in Example 2 of the present invention. DETAILED DESCRIPTION

[0036] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention. The experimental methods described in the embodiments of the present invention are conventional methods unless otherwise specified.

[0037] Compared with the prior art of oxidizing 3,3,3-trifluoropropene with potassium permanganate to obtain trifluoroacetic acid, the oxidants of the present invention are acid solution and hypochlorous acid compounds, which overcomes the problem that potassium permanganate produces a large amount of manganese salt during the reaction, which in turn causes environmental pollution and increases production costs.

[0038] Compared with the prior art electrochemical fluorination, the present invention not only solves the problem of energy consumption, but also overcomes the problems of poor environmental protection, poor reaction reproducibility, unsatisfactory chemical yield, high current efficiency and high energy consumption caused by the use of hydrogen fluoride gas.

[0039] Compared with the prior art of obtaining trifluoroacetic acid by oxidizing 1,1,1-trifluoro-2,3,3-trichloropropene with potassium permanganate, the raw materials of the invention can be purchased without preparation, thus overcoming the defect of poor reaction economy.

[0040] Compared with the existing technology of oxidizing 2,3-dichlorohexafluoro-2-butene to prepare trifluoroacetic acid, the process overcomes the difficulty in synthesizing the raw material 2,3-dichlorohexafluoro-2-butene and avoids the use of dangerous fluorine gas as a raw material. The above two points make the industrial value of this process low.

[0041] Compared with the prior art synthesis route of hydrolyzing trifluoroacetonitrile by reacting trichloroacetonitrile with hydrogen fluoride, the present invention overcomes the environmental protection problem caused by the use of hydrogen fluoride gas and has the advantages of simple process, high yield and less three wastes.

[0042] Compared with the prior art route of preparing trifluoroacetic acid by chromic acid oxidation of m-trifluoromethylaniline, the raw material trifluoromethylaniline is difficult to purchase, so it has no industrial prospects. The raw materials of the present invention are cheap and easy to obtain, and are suitable for industrial large-scale production.

[0043] Compared with the prior art of preparing trifluoroacetic acid using 2-chloro-1,1,1-trifluoroethane as a raw material, the present invention obtains trifluoroacetic acid in one step, overcomes the problems of complicated operation steps and complex process in multi-step reactions, and does not require a catalyst to participate in the reaction, so the invention is suitable for industrial production.

[0044] The present invention uses 2-chloro-1,1,1-trifluoroethane as a raw material, and uses an acid solution and a hypochlorous acid compound to oxidize 2-chloro-1,1,1-trifluoroethane under light conditions, thereby overcoming the technical defects of the above-mentioned prior art preparation methods and providing a one-step method for preparing trifluoroacetic acid, thereby reducing the preparation cost and realizing the reuse of waste 2-chloro-1,1,1-trifluoroethane. The preparation principle is as follows: Figure 4 shown.

[0045] The technical solution of the present invention is further explained by using embodiments and comparative examples, as shown below:

[0046] Example 1

[0047] A method for preparing trifluoroacetic acid comprises the following steps:

[0048] S1. Add 13.6g of sodium hypochlorite solution into a 50mL round-bottom flask, the effective chlorine content of which is 11.5%, and the amount of sodium hypochlorite is calculated to be 13.6×11.5%=1.564g; insert a balloon filled with 2-chloro-1,1,1-trifluoroethane into the round-bottom flask under 50W visible light with a wavelength of 365nm, and then inject 16.8mol / L sulfuric acid solution into the round-bottom flask in six batches, 0.4mL each time, for a total of 2.4mL, and then continue to stir and react under light for 12h. After the reaction is completed, distill to obtain 0.85g of trifluoroacetic acid, with a yield of 75%.

[0049] Wherein, the mass ratio of sodium hypochlorite to 2-chloro-1,1,1-trifluoroethane is 1:1.

[0050] Example 2

[0051] A method for preparing trifluoroacetic acid comprises the following steps:

[0052] 6 g of sodium hypochlorite pentahydrate was added to a 50 mL round-bottom flask, and its effective chlorine content was 40%. The amount of sodium hypochlorite pentahydrate was calculated to be 6×40%=2.4 g. Under 30 W visible light with a wavelength of 365 nm, a balloon filled with 2-chloro-1,1,1-trifluoroethane was inserted into the round-bottom flask, and then 16.8 mol / L sulfuric acid solution was injected in six batches, 0.4 mL each time, for a total of 2.4 mL. The reaction was then continued to react under light with stirring for 12 h. After the reaction was completed, 0.80 g of trifluoroacetic acid was obtained by distillation, with a yield of 94%.

[0053] Wherein, the mass ratio of sodium hypochlorite pentahydrate to 2-chloro-1,1,1-trifluoroethane is 1:3.

[0054] Example 3

[0055] A method for preparing trifluoroacetic acid comprises the following steps:

[0056] 2.8 g of calcium hypochlorite was added to a 250 mL round-bottom flask. Under 50 W visible light with a wavelength of 365 nm, a balloon filled with 2-chloro-1,1,1-trifluoroethane was inserted into the round-bottom flask. Then, 16.8 mol / L sulfuric acid solution was injected in three batches, 1 mL each time, for a total of 3 mL. The reaction was continued under stirring for 18 h under light. After the reaction, 1.14 g of trifluoroacetic acid was obtained by distillation with a yield of 50%.

[0057] Wherein, the mass ratio of calcium hypochlorite to 2-chloro-1,1,1-trifluoroethane is 1:5.

[0058] Example 4

[0059] A method for preparing trifluoroacetic acid comprises the following steps:

[0060] 6 g of sodium hypochlorite pentahydrate was added to a 50 mL round-bottom flask, and its effective chlorine content was 40%. The amount of sodium hypochlorite pentahydrate was calculated to be 6×40%=2.4 g. Under 50 W visible light with a wavelength of 365 nm, a balloon filled with 2-chloro-1,1,1-trifluoroethane was inserted into the round-bottom flask, and 0.1 mol / L sulfuric acid solution was injected in twelve batches, 2 mL each time, for a total of 24 mL. The reaction was then continued to be stirred under light for 8 h. After the reaction was completed, 0.26 g of trifluoroacetic acid was obtained by distillation, with a yield of 30%.

[0061] Among them, the mass ratio of sodium hypochlorite pentahydrate to 2-chloro-1,1,1-trifluoroethane is 1:4.

[0062] Example 5

[0063] A method for preparing trifluoroacetic acid comprises the following steps:

[0064] 6 g of sodium hypochlorite pentahydrate was added to a 50 mL round-bottom flask, and its effective chlorine content was 40%. The amount of sodium hypochlorite pentahydrate was calculated to be 6×40%=2.4 g. Under 50 W visible light with a wavelength of 365 nm, a balloon filled with 2-chloro-1,1,1-trifluoroethane was inserted into the round-bottom flask, and 5 mol / L sulfuric acid solution was injected in twelve batches, 4 mL each time, for a total of 48 mL. The reaction was then continued to be stirred under light for 24 h. After the reaction was completed, 0.69 g of trifluoroacetic acid was obtained by distillation, with a yield of 81%.

[0065] Among them, the mass ratio of sodium hypochlorite pentahydrate to 2-chloro-1,1,1-trifluoroethane is 1:2.

[0066] Example 6

[0067] A method for preparing trifluoroacetic acid comprises the following steps:

[0068] 1 g of sodium hypochlorite pentahydrate was added to a 20 mL vial. The effective chlorine content of the sodium hypochlorite pentahydrate was 40%. The amount of sodium hypochlorite pentahydrate was calculated to be 1×40%=0.4 g. Under 30 W visible light with a wavelength of 365 nm, a balloon filled with 2-chloro-1,1,1-trifluoroethane was inserted into the round-bottom flask. Then, 12 mol / L hydrochloric acid solution was injected in six batches, 1 mL each time, for a total of 6 mL. The reaction was then continued to be stirred under light for 8 h. After the reaction was completed, 114 mg of trifluoroacetic acid was obtained by distillation, with a yield of 80%.

[0069] Wherein, the mass ratio of sodium hypochlorite pentahydrate to 2-chloro-1,1,1-trifluoroethane is 1:5.

[0070] Example 7

[0071] A method for preparing trifluoroacetic acid comprises the following steps:

[0072] 1 g of sodium hypochlorite pentahydrate was added to a 20 mL vial. The effective chlorine content of the sodium hypochlorite pentahydrate was 40%. The amount of sodium hypochlorite pentahydrate was calculated to be 1×40%=0.4 g. Under 50 W visible light with a wavelength of 365 nm, a balloon filled with 2-chloro-1,1,1-trifluoroethane was inserted into the round-bottom flask. Then, 0.1 mol / L hydrochloric acid solution was injected in eleven batches, 1 mL each time, for a total of 11 mL. The reaction was then continued to react under light with stirring for 12 h. After the reaction was completed, 28 mg of trifluoroacetic acid was obtained by distillation, with a yield of 20%.

[0073] Among them, the mass ratio of sodium hypochlorite pentahydrate to 2-chloro-1,1,1-trifluoroethane is 1:4.

[0074] Example 8

[0075] A method for preparing trifluoroacetic acid comprises the following steps:

[0076] 1 g of sodium hypochlorite pentahydrate was added to a 20 mL vial, the effective chlorine content of which was 40%, and the amount of sodium hypochlorite pentahydrate was calculated to be 1×40%=0.4 g. Under 40 W visible light with a wavelength of 365 nm, a balloon filled with 2-chloro-1,1,1-trifluoroethane was inserted into the round-bottom flask, and then 5 mol / L hydrochloric acid solution was injected in eleven batches, 2 mL each time, for a total of 22 mL. The reaction was then continued to react under light with stirring for 24 h. After the reaction was completed, 86 mg of trifluoroacetic acid was obtained by distillation, with a yield of 60%.

[0077] Among them, the mass ratio of sodium hypochlorite pentahydrate to 2-chloro-1,1,1-trifluoroethane is 1:2.

[0078] Comparative Example 1

[0079] A method for preparing trifluoroacetic acid, using potassium permanganate as an oxidant, comprises the following steps:

[0080] 0.79 g of potassium permanganate solid and 1.6 g of sodium hypochlorite solution were added to a 20 mL vial. The effective chlorine content of the sodium hypochlorite solution was 11.5%. The amount of sodium hypochlorite was calculated to be 1.6×11.5%=0.184 g. Under irradiation with 30 W visible light and a wavelength of 365 nm, a balloon filled with 2-chloro-1,1,1-trifluoroethane was inserted into the round-bottom flask, and the reaction was continued to be stirred under light for 12 hours. After the reaction was completed, no product trifluoroacetic acid was detected.

[0081] Comparative Example 2

[0082] A method for preparing trifluoroacetic acid, using nitric acid as an oxidant, comprises the following steps:

[0083] 1.6 g of sodium hypochlorite solution was added to a 20 mL vial. The effective chlorine content of the sodium hypochlorite solution was 11.5%. The amount of sodium hypochlorite was calculated to be 1.6×11.5%=0.184 g. Under irradiation with 30 W visible light and a wavelength of 365 nm, a balloon filled with 2-chloro-1,1,1-trifluoroethane was inserted into the round-bottom flask, and then 16 mol / L, 0.5 mL of nitric acid solution was slowly injected. The reaction was then stirred under light for 10 hours. No product trifluoroacetic acid was detected after the reaction was completed.

[0084] The product trifluoroacetic acid is obtained in Examples 1 to 8 of the present invention. The trifluoroacetic acid obtained in Example 2 is used as an example for research. The specific research method and results are as follows:

[0085] Figure 1is the peak position of the trifluoroacetic acid NMR fluorine spectrum, 19 F NMR (565 MHz, CDCl3) -76.60(s,3F).

[0086] Figure 2 and Figure 3 is the peak position of the carbon NMR spectrum of trifluoroacetic acid, 13 C NMR (151 MHz, CDCl3)162.7 (q, J = 44.1 Hz ), 113.7 (q, J = 285.1 Hz).

[0087] Figure 4 This is the high-resolution mass spectrum of trifluoroacetic acid. The results show that the molecular formula of trifluoroacetic acid is CF3COOH, and its accurate molecular mass is 113.9929. ESI-HRMS: m / z Calcd for C2HF3O2[M+H] + :115.0007, found114.9998.

[0088] Figure 5 The schematic diagram of the reaction process of preparing trifluoroacetic acid using sulfuric acid or hydrochloric acid as the acid solution, where H + Provided by sulfuric acid or hydrochloric acid.

[0089] Figure 6 is the peak position of the nuclear magnetic resonance fluorine spectrum of trifluorotrichloroethane, a by-product distilled from the reaction, 19 F NMR (565 MHz, CDCl3) -82.20 (s,3F).

[0090] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, they are also intended to be included.

Claims

1. A method for preparing trifluoroacetic acid, characterized in that, The steps include: Under visible light irradiation, a hypochlorous acid compound and 2-chloro-1,1,1-trifluoroethane are mixed, and then an acid solution is added in batches, and the hypochlorous acid compound and the acid solution are used to oxidize the 2-chloro-1,1,1-trifluoroethane to obtain trifluoroacetic acid; The mass ratio of 2-chloro-1,1,1-trifluoroethane, hypochlorous acid compound and acid solution is 1~5:1:0.1~10; The hypochlorous compound is hypochlorous acid or a hypochlorite; The acid solution is selected from sulfuric acid solution or hydrochloric acid solution.

2. The method for preparing trifluoroacetic acid according to claim 1, wherein The oxidation conditions are: stirring the reaction at room temperature for 8h~24h.

3. A method for preparing trifluoroacetic acid according to claim 1, characterized in that, The wavelength of visible light is 200nm~600nm.

4. The method for preparing trifluoroacetic acid according to claim 1, wherein The hypochlorite is selected from sodium hypochlorite or calcium hypochlorite.

5. A method for preparing trifluoroacetic acid according to claim 4, characterized in that, The hypochlorite is selected from sodium hypochlorite pentahydrate.

6. The method for preparing trifluoroacetic acid according to claim 1, wherein When the acid solution is selected from sulfuric acid solution, the concentration of the sulfuric acid solution is 0.1 mol / L~16.8 mol / L.

7. The method for preparing trifluoroacetic acid according to claim 1, wherein When the acid solution is selected from hydrochloric acid solution, the concentration of the hydrochloric acid solution is 0.1 mol / L~12 mol / L.

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