A method for preparing trifluoropropionic acid

Abstract

This invention discloses a method for preparing trifluoropropionic acid, comprising the following steps: Step 1, reacting acetic acid with trifluoropropylene under the action of a catalyst to obtain trifluoropropyl acetate; Step 2, transesterifying trifluoropropyl acetate with methanol to obtain trifluoropropanol; Step 3, oxidizing trifluoropropanol with hydrogen peroxide under the action of a catalyst to obtain trifluoropropionic acid. This invention has a high yield, simple process conditions, and cheaper raw materials, which can significantly reduce the cost of trifluoropropionic acid.

Description

Technical Field

[0001] This invention belongs to the field of organofluorine chemical technology, specifically relating to a method for preparing trifluoropropionic acid. Background Technology

[0002] Trifluoropropionic acid is a colorless, toxic, highly corrosive, transparent liquid with an acidic odor. It has a boiling point of 146℃, a melting point of 97℃, and a density of 1.359 g / cm³. It is miscible with water and various organic solvents. Trifluoropropionic acid contains a trifluoromethyl group, a strong electron-withdrawing group, which distinguishes its physicochemical properties from other aliphatic carboxylic acids. Due to the strong electron-withdrawing nature of the CF3 group, trifluoropropionic acid exhibits strong acidity and polarity, comparable to hydrofluoric acid and much stronger than typical fatty acids. As a fluorinated acid, trifluoropropionic acid can be used as an intermediate in the synthesis of pharmaceuticals and pesticides, as well as a raw material or intermediate in the synthesis of high-performance materials. It is also an excellent catalyst and a high-grade solvent with special applications, showing broad application prospects.

[0003] Chinese patent CN101973867 discloses a method for preparing 3,3,3-trifluoropropionic acid, which uses 3,3,3-trifluoropropaldehyde as raw material and mesoporous sulfonic acid as catalyst to oxidize the product under the action of hydrogen peroxide. The method is simple to operate, but the product yield is low, and the catalyst used is a solid strong acid, which generates a lot of acidic wastewater, which is not conducive to environmental protection.

[0004] Chinese patent CN103965047 discloses a method for preparing 3,3,3-trifluoropropionic acid, which involves reacting bromoacetic acid with trifluoromethane in the presence of cuprous chloride and tert-butanol alkali metal salt. This method requires a large amount of catalyst and is costly.

[0005] Chinese patent CN107956849 discloses a method for preparing the pharmaceutical intermediate 3,3,3-trifluoropropionic acid. First, trifluoropropylene is used as a raw material and reacted with oxygen in the presence of zirconium oxide and cerium oxide. Then, citric acid, manganese chloride, and titanium oxide are added to react and obtain the product. This method is simple to operate, but the reaction process is relatively long, and the product yield needs further improvement. Summary of the Invention

[0006] Purpose of the invention: In order to overcome the shortcomings of the prior art, the present invention provides a method for preparing trifluoropropionic acid.

[0007] Technical solution: A method for preparing trifluoropropionic acid, comprising the following steps:

[0008] Step 1: In a high-pressure reactor, add acetic acid and a certain proportion of catalyst, heat to a certain temperature, and start to introduce trifluoropropylene while maintaining a certain reaction pressure. After the trifluoropropylene has been introduced for 8-10 hours, cool down and transfer to a flask equipped with a distillation column and condenser. Distill under reduced pressure to obtain trifluoropropyl acetate.

[0009] Step 2: Add trifluoropropyl acetate and a certain amount of methanol to a flask, then add a certain proportion of catalyst, heat and reflux until the trifluoropropyl acetate reacts completely, then put it into a distillation apparatus to distill and obtain trifluoropropanol.

[0010] Step 3: Trifluoropropanol and hydrogen peroxide are oxidized at a fixed reaction temperature under the action of a catalyst to obtain trifluoropropionic acid.

[0011] Furthermore: In step one, the certain proportion of catalyst refers to a catalyst mass of 1-10% of the mass of acetic acid, and the catalyst is boron trifluoride diethyl ether.

[0012] Furthermore, in step one, the molar ratio of acetic acid to trifluoropropylene is 1-3:1.

[0013] Furthermore: In step one, maintaining a certain reaction pressure means maintaining a pressure of 1-3 MPa.

[0014] Furthermore: In step one, the temperature referred to as heating to a certain temperature is 120-150℃.

[0015] Furthermore: In step two, the methanol equivalent referred to as a certain amount of methanol is 2-5 times the molar equivalent.

[0016] Furthermore: In step two, the catalyst of a certain proportion refers to 1-10% of the mass of methanol, and the catalyst refers to an alkali metal salt, including one of sodium hydroxide, potassium hydroxide, sodium methoxide, sodium ethoxide, sodium tert-butoxide, and potassium tert-butoxide.

[0017] Furthermore, in step three, the molar ratio of trifluoropropanol to hydrogen peroxide is 1:1.05-1.5, and the concentration of hydrogen peroxide is 8-27.5%.

[0018] Furthermore: In step three, the catalyst is ferric chloride plus hydrochloric acid, the amount of ferric chloride is 0.2-1% of the mass of hydrogen peroxide, and the amount of hydrochloric acid is 2-5% of the mass of hydrogen peroxide.

[0019] Furthermore, in step three, the reaction temperature is fixed at 60-100℃.

[0020] Beneficial effects: This invention has a high yield, simple process conditions, and cheaper raw materials, which can greatly reduce the cost of trifluoropropionic acid. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below, so that those skilled in the art can better understand the advantages and features of the present invention, thereby making a clearer definition of the scope of protection of the present invention. The embodiments described in this invention are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0022] Example

[0023] 1. Preparation of trifluoropropyl acetate

[0024] In a 500ml autoclave, 120g (2mol) of acetic acid and 6g of boron trifluoride diethyl ether were added and heated to 130℃. Then, 96g (1mol) of trifluoropropylene was introduced and the pressure was maintained at 1.5MPa for 8 hours. The mixture was then cooled and transferred to a flask equipped with a distillation column and a condenser. The mixture was then distilled under reduced pressure to obtain 148.8g of trifluoropropyl acetate with a purity of 98.2% and a yield of 95.4%.

[0025] 2. Preparation of trifluoropropanol

[0026] 78 g (0.5 mol) of trifluoropropyl acetate and 48 g (1.5 mol) of methanol were added to a 250 ml flask, followed by 2.5 g of solid sodium hydroxide. The mixture was heated to reflux and reacted for 2 hours. The mixture was then placed in a distillation apparatus and distilled to obtain 56 g of trifluoropropanol with a purity of 99.6% and a yield of 98.5%.

[0027] 3. Preparation of trifluoropropionic acid

[0028] 50 g (0.44 mol) of trifluoropropanol was added to a flask equipped with a reflux condenser. After heating to 80 °C, pre-prepared hydrogen peroxide (205.7 g 8% hydrogen peroxide plus 0.5 g ferric chloride and 6 g hydrochloric acid) was added dropwise. The dropping rate was controlled, and the reaction temperature was maintained at 80 °C. After the addition was completed, the temperature was cooled to room temperature. The mixture was extracted three times with 200 ml of methyl tert-butyl ether. The organic phases were combined, dried with magnesium sulfate, and distilled to obtain 54 g of trifluoropropionic acid with a purity of 99.8% and a yield of 96%.

[0029] This invention has a high yield, simple process conditions, and cheaper raw materials, which can greatly reduce the cost of trifluoropropionic acid.

Claims

1. A method for preparing trifluoropropionic acid, characterized in that: Includes the following steps: Step 1: In a high-pressure reactor, add acetic acid and a certain proportion of catalyst, heat to a certain temperature, and start to introduce trifluoropropylene while maintaining a certain reaction pressure. After the trifluoropropylene has been introduced for 8-10 hours, cool down and transfer to a flask equipped with a distillation column and condenser. Distill under reduced pressure to obtain trifluoropropyl acetate. Step 2: Add trifluoropropyl acetate and a certain amount of methanol to a flask, then add a certain proportion of catalyst, heat and reflux until the trifluoropropyl acetate reacts completely, then put it into a distillation apparatus to distill and obtain trifluoropropanol. Step 3: Trifluoropropanol and hydrogen peroxide are oxidized at a fixed reaction temperature under the action of a catalyst to obtain trifluoropropionic acid; In step one, the catalyst of a certain proportion refers to a catalyst mass of 1-10% of the mass of acetic acid, and the catalyst is boron trifluoride diethyl ether; the molar ratio of acetic acid to trifluoropropylene is 1-3:1; maintaining a certain reaction pressure refers to maintaining a pressure of 1-3 MPa; heating to a certain temperature refers to a temperature of 120-150℃. In step two, the methanol equivalent of a certain amount refers to 2-5 times the molar equivalent; the catalyst of a certain proportion refers to a catalyst added at a mass of 1-10% of the methanol mass, and the catalyst refers to an alkali metal salt, including one of sodium hydroxide, potassium hydroxide, sodium methoxide, sodium ethoxide, sodium tert-butoxide, and potassium tert-butoxide. In step three, the molar ratio of trifluoropropanol to hydrogen peroxide is 1:1.05-1.5, and the concentration of hydrogen peroxide is 8-27.5%; the catalyst is ferric chloride and hydrochloric acid, with the amount of ferric chloride being 0.2-1% of the mass of hydrogen peroxide and the amount of hydrochloric acid being 2-5% of the mass of hydrogen peroxide; and the reaction temperature is fixed at 60-100℃.