Method for preparing 3, 3, 3-trifluoro-1-propyne by two-step method

Abstract

The invention discloses a method for preparing 3, 3, 3-trifluoro-1-propyne through a two-step method, the 3, 3, 3-trifluoro-1-propyne is prepared through a production system and collected through a material collecting system, and the preparation steps of the production system comprise: (1) in a first solvent, carrying out an addition reaction on 3, 3, 3-trifluoro-1-propylene and ICl to obtain 2-iodo-1-chloro-3, 3, 3-trifluoropropane; (2) in a second solvent, enabling the 2-iodine-1-chloro-3, 3, 3-trifluoropropane to react with alkali to eliminate bimolecular hydrogen halide so as to obtain 3, 3, 3-trifluoro-1-propyne; the temperature of the material receiving system is-196 to-60 DEG C, and the pressure of the material receiving system is-0.03 MPa to normal pressure. The 3, 3, 3-trifluoro-1-propyne is prepared by taking trifluoropropene as a raw material through two-step reaction, and the method has the advantages of simple preparation steps, high reaction yield, small amount of three wastes, low production cost and the like, and is very suitable for industrial production.

Description

Technical Field

[0001] The present invention relates to the synthesis of fluorinated alkynes, and particularly to a method for preparing 3,3,3-trifluoro-1-propyne from 1,1,2-trifluoropropene through two-step reactions. Background Art

[0002] 3,3,3-trifluoro-1-propyne, with the molecular formula C3HF3, is abbreviated as TFPY in English. Its boiling point is -48.3°C, flash point is -94.5±13.9°C, and density is 1.2 g / cm 3 , GWP1.4, and ODP is negligible. TFPY is a new type of refrigerant with low GWP and can be used as an anti-corrosion agent, aerosol, foaming agent. It can also be used for synthesizing pharmaceutical intermediates and monomers of high molecular compounds, and is a very important fluorinated industrial product.

[0003] Currently, the preparation processes of TFPY mainly include a liquid-phase elimination process and a gas-phase dehydrohalogenation process. Among them, the gas-phase dehydrohalogenation process generally has problems such as low catalyst activity, low raw material conversion rate, and low yield, making it difficult to meet the requirements of industrial production. The liquid-phase elimination process is more applied in industrial production. The raw material routes of the liquid-phase elimination process mainly include:

[0004] (1) 1,1,2-trifluoropropane raw material process

[0005] Patent CN101675017A discloses a method for preparing TFPY using cis-1-chloro-3,3,3-trifluoropropane (Z-1233zd) as the raw material. It uses potassium hydroxide as the base, water and methanol as the solvents, and reacts at 38°C. The conversion rate of the raw material Z-1233zd is 98.6%, the selectivity of the product TFPY is 98.3%, and the yield is 96.9%. However, when the raw material is E-1233zd and reacts under the same conditions, no product is formed at all.

[0006] The above reaction is an anti-elimination reaction. When the leaving group is in the anti position, elimination can occur smoothly. Therefore, Z-1233zd can smoothly eliminate one molecule of HCl to obtain TFPY. However, it is difficult to obtain and prepare the raw material Z-1233zd, making it difficult to meet the requirements of industrial production. Although E-1233zd is an industrial product with low price, the reaction conditions for direct elimination reaction are very harsh and the yield is low, which is not suitable for industrial production.

[0007] (2) 1,1,2-trifluoropropene raw material process

[0008] Henne Laboratory (A.L. Henne, M. Nager, Trifluoropropyne, J. Am. Chem. Soc 73 (1951) 1042–1043.) disclosed a process for preparing TFPY using 3,3,3-trifluoropropene (TFP) as a raw material. First, the addition reaction of TFP with bromine gives a dibrominated product 1,2-dibromo-3,3,3-trifluoropropane, then the elimination reaction with a base gives 2-bromo-3,3,3-trifluoropropene, followed by the addition reaction with bromine to obtain 1,2,2-tribromo-3,3,3-trifluoropropane. After that, it reacts with a base again to get 1,2-dibromo-3,3,3-trifluoropropene, and finally, it is reduced with zinc powder to obtain TFPY. This process undergoes five steps, with a complex process and cumbersome operation. Although the yield of each step exceeds 90%, the final overall yield is only 73%. Moreover, this method involves bromination reactions, which require high equipment requirements, high production costs, and low market competitiveness.

[0009] In summary, it is necessary to develop a synthetic process for 3,3,3-trifluoro-1-propyne that is simple in process, high in reaction yield, low in production cost, safe, environmentally friendly, suitable for industrial application, and has market competitiveness. Summary of the Invention

[0010] To solve the above technical problems, the present invention proposes a method for obtaining 3,3,3-trifluoro-1-propyne from trifluoropropene through two-step reactions.

[0011] The object of the present invention is achieved by the following technical solutions:

[0012] A method for preparing 3,3,3-trifluoro-1-propyne by a two-step process, wherein the 3,3,3-trifluoro-1-propyne is prepared by a production system and collected by a receiving system. The preparation steps of the production system include:

[0013] (1) In a first solvent, 3,3,3-trifluoro-1-propene undergoes an addition reaction with ICl to obtain a compound of the following formula (I);

[0014] (2) In a second solvent, the compound of formula (I) reacts with a base to eliminate two molecules of hydrogen halide to obtain 3,3,3-trifluoro-1-propyne shown in the following formula (II);

[0015] The reaction equations are as follows:

[0016]

[0017] The starting material 3,3,3-trifluoro-1-propene used in the present invention is a refrigerant produced industrially, with low cost and easy availability. The iodine used in the reaction can also be recycled, further reducing the production cost. The main three wastes are salty wastewater, with a small amount and easy to treat, having advantages in industrial production.

[0018] The collection of the product of the present invention is carried out in a material receiving system. The material receiving system is connected to the product outlet of step (2) of the production system. The temperature of the material receiving system is -196 to -60 °C, and the pressure is -0.03 Mpa to atmospheric pressure. Preferably, the temperature of the material receiving system is controlled to be -196 to -80 °C, and the pressure is -0.02 to -0.01 MPa. If the temperature of the material receiving system is too high, it will cause the product to not be cooled in time; if the vacuum degree of the material receiving system is too low, it will cause the raw materials to be transferred to the material receiving system prematurely, thereby reducing the conversion rate of the raw materials; if the vacuum degree of the material receiving system is relatively high, it will cause the product to not be transferred out of the reaction system in time, increasing the self-polymerization of the product, thereby reducing the amount of the collected product and the reaction yield.

[0019] In step (1) of the production system of the present invention, the first solvent is selected from at least one of halogenated hydrocarbons, ether solvents, nitrile solvents, amide solvents or sulfone solvents; in step (2), the second solvent is selected from at least one of water, alcohol solvents, ether solvents, nitrile solvents, amide solvents or sulfone solvents.

[0020] Preferably, the halogenated hydrocarbon is selected from at least one of dichloromethane, dichloroethane, trichloroethane, dichloropropane, chloroform or carbon tetrachloride; the alcohol solvent is selected from at least one of methanol, ethanol, propanol, isopropanol, ethylene glycol or diethylene glycol; the ether solvent is selected from at least one of tetrahydrofuran, diethyl ether or dioxane; the nitrile solvent is selected from at least one of acetonitrile, propionitrile or butyronitrile; the amide solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide or hexamethylphosphoric triamide; the sulfone solvent is selected from dimethyl sulfoxide and / or sulfolane.

[0021] Furthermore, in step (1), the molar ratio of ICl to 3,3,3-trifluoro-1-propene is 1:(1.0 to 1.5). Preferably, the molar ratio of ICl to 3,3,3-trifluoro-1-propene is 1:(1.1 to 1.2).

[0022] In step (1), the dosage of the first solvent has no specific limitation as long as the dosage of the first solvent can ensure the normal progress of the reaction in step (1). Preferably, the mass ratio of the raw material 3,3,3-trifluoro-1-propene to the first solvent is 1:(1 to 5); more preferably, the mass ratio of 3,3,3-trifluoro-1-propene to the first solvent is 1:(2 to 4).

[0023] In step (2), the base is selected from at least one of alkali metal hydroxides, alkali metal alkoxides or alkali metal amides. Preferably, the base is selected from at least one of alkali metal hydroxides and alkali metal alkoxides. Specifically, the base is selected from at least one of potassium hydroxide, sodium hydroxide and potassium tert-butoxide.

[0024] The phase transfer catalyst can increase the reaction rate, shorten the reaction time, and thus reduce the self-polymerization of the product. Therefore, step (2) is preferably carried out in the presence of a phase transfer catalyst, and the phase transfer catalyst is selected from alkyl quaternary ammonium salts containing C2-C12 alkyl groups. Further preferably, the alkyl quaternary ammonium salt is selected from at least one of tetrabutylammonium chloride, tetrabutylammonium bromide, methyltrioctylammonium chloride or tetra(dodecyl)ammonium chloride.

[0025] Furthermore, in step (2), the molar ratio of the compound of formula (I) to the base is 1:(2.0-10.0). Preferably, the molar ratio of the compound of formula (I) to the base is 1:(4.0-8.0).

[0026] In step (2), the amount of the second solvent is not specifically limited as long as the amount of the second solvent can ensure the normal progress of the reaction in step (2). Preferably, the mass ratio of the compound of formula (I) to the second solvent is 1:(1-5); more preferably, the mass ratio of the compound of formula (I) to the second solvent is 1:(2-3).

[0027] In step (2), the molar ratio of the compound of formula (I) to the phase transfer catalyst is 1:(0.01%-1.0%). Preferably, the molar ratio of the compound of formula (I) to the phase transfer catalyst is 1:(0.1%-1.0%).

[0028] In the process of preparing 3,3,3-trifluoro-1-propyne by the two-step method of the present invention, the reaction temperature of step (1) is -30 to 10 °C, and the reaction time is 1 to 24 h; the reaction temperature of step (2) is -20 to 120 °C, and the reaction time is 2 to 8 h. Preferably, the reaction temperature of step (1) is -20 to -10 °C, and the reaction time is 1 to 18 h; the reaction temperature of step (2) is 50 to 80 °C, and the reaction time is 2 to 6 h.

[0029] Specifically, the preparation steps of the 3,3,3-trifluoro-1-propyne compound of the present invention include:

[0030] In step (1), a magnetic rotor, a first solvent and ICl are sequentially added to a reactor, adjusted to the required temperature, and then gaseous or liquid 3,3,3-trifluoro-1-propene is introduced into the reactor. After the feeding is completed, the reaction is continued until the end.

[0031] The excess 3,3,3-trifluoro-1-propene was slowly distilled off, and then a 5% Na2S2O3 solution was added to the reaction solution with continuous stirring until the reaction solution became colorless. The organic phase was separated, washed three times with 300 mL of water, and the solvent was removed by rotary evaporation after drying to obtain the compound of formula (I).

[0032] In step (2), a magnetic rotor, a second solvent, and a base were successively added to the reactor, adjusted to the required temperature, and the compound of formula (I) was added dropwise for reaction to obtain the trifluoropropyne shown in formula (II). Preferably, the phase transfer catalyst and the second solvent were added to the reactor simultaneously.

[0033] The trifluoropropyne generated in step (2) was collected through a material collection system, which consisted of a low-temperature environment (ultra-low temperature freezer or dry ice bath, liquid nitrogen), a collection bottle, and a vacuum pump. The collection bottle was placed in the low-temperature environment. The liquid phase port of the collection bottle was connected to a copper coil, the coil was connected to the reactor in step (2), the gas phase port of the collection bottle was connected to a buffer bottle, and the buffer bottle was connected to the vacuum pump. The vacuum degree was set. When the vacuum gauge of the buffer bottle showed the required vacuum degree, the vacuum pump was turned off; when the pressure gauge reading deviated from the required vacuum degree, the vacuum pump was turned on, and the vacuum pump was turned off again after reaching the vacuum degree. The vacuum degree was controlled by intermittently turning on the vacuum pump to avoid pumping out the product.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. The present invention uses trifluoroethylene as the starting material and obtains TFPY through two-step reactions. Not only are the raw materials simple and easily available, and the process is simple, but also the reaction yield is greatly improved through the environmental control of the material collection system.

[0036] 2. The raw materials used in the present invention contain iodine. As a good leaving group, iodine can eliminate two molecules of hydrogen halide in one step, and the elimination reaction efficiency is higher, and the yield is further improved. After the reaction, iodine can also be recovered, with less three wastes and low production cost, and high feasibility for industrial application. Specific Embodiments

[0037] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all alternative, improved, and equivalent solutions that may be included within the scope of the claims.

[0038] Example 1

[0039] This example provides a preparation method of 3,3,3-trifluoro-1-propyne, which specifically includes the following steps:

[0040] (1) Addition reaction of trifluoroethylene R1234zf with ICl

[0041] The reactor used was a 500 mL three-necked flask. One neck was connected to a thermometer, one to a nitrogen bag, and one to a gas pipe (the front section of the gas pipe was connected to an R1234zf cylinder). In a nitrogen atmosphere, a magnetic rotor, 127.5 g of dry dichloromethane, and 48.6 g (0.3 mol) of ICl were successively added to the three-necked flask. The flask was placed in a low-temperature circulating reaction bath, and the temperature was set to -20 °C. After the temperature reached -20 °C, gaseous R1234zf was introduced, and the flow rate was controlled at 30 mL / min. When the introduced weight reached 40.3 g (0.36 mol), the feeding was stopped, and the reaction continued for 16 h. After the reaction ended, the reaction was quenched with a 5% Na2S2O4 solution at 0 °C, then washed three times with water. The organic phase was taken, dried with anhydrous magnesium sulfate, and the solvent was evaporated to obtain a colorless liquid, weighing 61.8 g.

[0042] Gas chromatography analysis of this liquid showed that the content of 2-iodo-1-chloro-3,3,3-trifluoropropane was 98.6%, the content of dichloromethane was 1.1%, and the others were 0.3%. The reaction yield was calculated to be 78.7%.

[0043] (2) Elimination reaction of 2-iodo-1-chloro-3,3,3-trifluoropropane with a base

[0044] The reactor also used a 1000 mL three-necked flask. One neck was connected to a thermometer, one to a constant-pressure dropping funnel, and one to a spherical condenser. The temperature of the condensate was -20 °C, and the rear end of the condenser was connected to a receiving system. The temperature of the receiving system was controlled at -196 °C, and the pressure was -0.01 MPa.

[0045] In a nitrogen atmosphere, a magnetic rotor, 287.5 g of deionized water, and 224 g (4 mol) of potassium hydroxide were successively added to the flask. The temperature of the heater was set to 100 °C. After reaching the set temperature, 258 g (1 mol) of 2-iodo-1-chloro-3,3,3-trifluoropropane was slowly added dropwise. After the addition was completed, the reaction continued for 3 h, and the reaction ended. Layers appeared at the bottom of the flask. The lower organic phase was taken, washed with water, and weighed to obtain 121.6 g. Gas chromatography analysis showed that the organic phase in the flask was 2-iodo-3,3,3-trifluoropropene, with a content of 99.0% and other contents of 1%.

[0046] The total weight of the materials collected by the receiving system was 55.5 g. Sampling for gas chromatography analysis showed that the product collected by the receiving system was 3,3,3-trifluoro-1-propyne, with a content of 99.7% and other contents of 0.3%. It was calculated that the conversion rate of 2-iodo-1-chloro-3,3,3-trifluoropropane was close to 100%, and the product selectivity was 58.3%.

[0047] Example 2

[0048] The operation of this example is the same as that of Example 1, with the only difference being that: in step (1), the reaction temperature is increased to -10°C, and other operations remain unchanged. Finally, a colorless liquid is obtained, weighing 70.1 g. Gas chromatography analysis of this liquid shows that: the content of 2-iodo-1-chloro-3,3,3-trifluoropropane is 99.0%, the content of dichloromethane is 0.7%, and the others are 0.3%. The reaction yield is calculated to be 89.7%.

[0049] Example 3

[0050] The operation of this example is the same as that of Example 2, with the only difference being that: in step (1), the reaction temperature is increased to 0°C, and other operations remain unchanged. Finally, a colorless liquid is obtained, weighing 71.2 g. Gas chromatography analysis of this liquid shows that: the content of 2-iodo-1-chloro-3,3,3-trifluoropropane is 86.0%, the content of 1-iodo-2-chloro-3,3,3-trifluoropropane is 12.3%, the content of dichloromethane is 0.7%, and the others are 1.0%. The reaction yield is calculated to be 79.1%.

[0051] Example 4

[0052] The operation of this example is the same as that of Example 2, with the only difference being that: in step (1), the reaction temperature is increased to 10°C, and other operations remain unchanged. Finally, a colorless liquid is obtained, weighing 70.4 g. Gas chromatography analysis of this liquid shows that: the content of 2-iodo-1-chloro-3,3,3-trifluoropropane is 12.1%, the content of 1-iodo-2-chloro-3,3,3-trifluoropropane is 85.8%, the content of dichloromethane is 0.9%, and the others are 1.2%. The reaction yield is calculated to be 11.0%.

[0053] Example 5

[0054] The operation of this example is the same as that of Example 2, with the only difference being that: in step (1), the reaction solvent is changed to 1,2-dichloroethane, and other operations remain unchanged. Finally, a colorless liquid is obtained, weighing 71.4 g. Gas chromatography analysis of this liquid shows that: the content of 2-iodo-1-chloro-3,3,3-trifluoropropane is 98.2%, the content of 1,2-dichloroethane is 1.4%, and the others are 0.4%. The reaction yield is calculated to be 90.6%.

[0055] Example 7

[0056] The operation of this example is the same as that of Example 2, with the only difference being that: in step (2), the amount of potassium hydroxide used is increased to 336 g (6 mol), and other operations remain unchanged. After the reaction, there is no organic phase at the bottom of the flask. The total weight of the materials received in the steel cylinder is 88.0 g. Gas chromatography analysis of the gas in the steel cylinder shows that: the content of 3,3,3-trifluoro-1-propyne is 99.5%, and the others are 0.5%. The raw material conversion rate is calculated to be close to 100%, and the reaction selectivity is 93.1%.

[0057] Example 8

[0058] The operation of this example is the same as that of Example 7, with the only difference being that in step (2), the base is changed to sodium hydroxide with a dosage of 240 g (6 mol), and other operations remain unchanged. After the reaction, there is no organic phase at the bottom of the flask. The total weight of the materials received in the steel cylinder is 87.1 g. The gas in the steel cylinder is taken for gas chromatography analysis. The results show that the content of 3,3,3-trifluoro-1-propyne is 99.5%, and the other is 0.5%. The raw material conversion rate is calculated to be close to 100%, and the reaction selectivity is 92.2%.

[0059] Example 9

[0060] The operation of this example is the same as that of Example 7, with the only difference being that in step (2), the solvent is changed to methanol and water with a volume ratio of 1:1 and a total volume of 300 mL, and other operations remain unchanged. After the reaction, there is no organic phase at the bottom of the flask. The total weight of the materials received in the steel cylinder is 83.7 g. The gas in the steel cylinder is taken for gas chromatography analysis. The results show that the content of 3,3,3-trifluoro-1-propyne is 99.3%, and the other is 0.7%. The raw material conversion rate is calculated to be close to 100%, and the reaction selectivity is 88.4%.

[0061] Example 10

[0062] The operation of this example is the same as that of Example 7, with the only difference being that in step (2), tetrabutylammonium bromide is added with a dosage of 1.61 g (0.005 mol), and other operations remain unchanged. The reaction ends after 1 h. There is no organic phase at the bottom of the flask. The total weight of the materials received in the steel cylinder is 90.5 g. The gas in the steel cylinder is taken for gas chromatography analysis. The results show that the content of 3,3,3-trifluoro-1-propyne is 99.5%, and the other is 0.5%. The raw material conversion rate is calculated to be close to 100%, and the reaction selectivity is 95.8%.

[0063] Example 11

[0064] The operation of this example is the same as that of Example 7, with the only difference being that in step (2), the reaction temperature is reduced to 30 °C, and other operations remain unchanged. Layers appear at the bottom of the flask. The lower organic phase is taken, washed with water, and weighed to be 86.5 g. The sample is taken for gas chromatography analysis. The results show that the content of 2-iodo-1-chloro-3,3,3-trifluoropropane is 98.4%, and the other is 1.6%. The total weight of the materials received in the steel cylinder is 89.1 g. The gas in the steel cylinder is taken for gas chromatography analysis. The results show that the content of 3,3,3-trifluoro-1-propyne is 99.8%, and the other is 0.2%. The raw material conversion rate is calculated to be 94.6%, and the reaction selectivity is 66.5%.

[0065] Example 12

[0066] The operation of this example is the same as that of Example 7, except that: in step (2), the pressure of the product collection system is -0.03 MPa, and other operations remain unchanged. After the reaction is completed, there is no organic phase at the bottom of the flask. The total weight of the materials received in the steel cylinder is 95.1 g. Take the sample in the steel cylinder for gas chromatography analysis. The results show that: the content of 3,3,3-trifluoro-1-propyne is 68.5%, the content of 3,3,3-trifluoro-2-iodo-1-propene is 30.5%, and other components account for 1%. The raw material conversion rate is calculated to be close to 100%, and the reaction selectivity is 69.3%.

[0067] Example 13

[0068] The operation of this example is the same as that of Example 7, except that: in step (2), the pressure of the product collection system is atmospheric pressure, and other operations remain unchanged. After the reaction is completed, there is no organic phase at the bottom of the flask. The total weight of the materials received in the steel cylinder is 56.7 g. Take the gas in the steel cylinder for gas chromatography analysis. The results show that: the content of 3,3,3-trifluoro-1-propyne is 99.6%, and other components account for 0.4%. The raw material conversion rate is calculated to be close to 100%, and the reaction selectivity is 60.1%.

[0069] Example 14

[0070] The operation of this example is the same as that of Example 7, except that: in step (2), the temperature of the product collection system is -60 °C, and other operations remain unchanged. After the reaction is completed, there is no organic phase at the bottom of the flask. The total weight of the materials received in the steel cylinder is 78.8 g. Take the gas in the steel cylinder for gas chromatography analysis. The results show that: the content of 3,3,3-trifluoro-1-propyne is 99.3%, and other components account for 0.7%. The raw material conversion rate is calculated to be close to 100%, and the reaction selectivity is 83.2%.

[0071] Comparative Example 1

[0072] This comparative example provides a traditional preparation process of 3,3,3-trifluoropropyne, which is carried out with reference to Background Technology A.L. Henne, M. Nager, Trifluoropropyne, J. Am. Chem. Soc., 73 (1951) 1042–1043. It mainly includes the following steps:

[0073] Preparation of 1,2-dibromo-3,3,3-trifluoropropane: The reactor is a 500 mL three-necked flask. One neck is connected to a thermometer, one to a reflux pipe, and one to an inlet gas conduit. The upper end of the reflux pipe is connected to a gas conduit that leads to a tail gas absorption device. The front end of the inlet gas conduit is connected to a cylinder of trifluoropropene. 20°C circulating water is passed through the reflux pipe. A magnetic rotor and 160 g (1 mol) of bromine are successively added to the three-necked flask. Stirring and heating are started. When the temperature reaches 60°C, gaseous TFP is introduced at a flow rate of approximately 30 mL / min. When the reaction liquid changes from dark brown to light yellow, feeding is stopped. The amount of TFP fed is 107 g (1.13 mol). The temperature is raised to 80°C and maintained for 30 min. The unreacted TFP in the flask is discharged. The reaction ends. The reaction liquid is washed with 5% sodium carbonate solution and then with water to obtain 250.3 g of the organic phase. A sample is taken for gas chromatography analysis. The results show that the content of 3,3,3-trifluoropropene is 0.3%, the content of 1,2-dibromo-3,3,3-trifluoropropane is 98.2%, other components are 1.5%, and the reaction yield is 96.1%.

[0074] Preparation of 2-bromo-3,3,3-trifluoropropene: The reactor is a 500 mL three-necked flask. One neck is connected to a thermometer, one to a constant pressure dropping funnel, and one is sealed with a hollow plug. A magnetic rotor, 120 mL of water, and 48 g (1.2 mol) of sodium hydroxide are successively added to the three-necked flask. Stirring and heating are started. When the temperature reaches 40°C, 1,2-dibromo-3,3,3-trifluoropropane prepared by the above method is added dropwise. The dropping rate is adjusted to control the reaction temperature at 40°C. The total feeding amount of 1,2-dibromo-3,3,3-trifluoropropane is 256 g (1 mol). After the feeding is completed, the reaction continues for 3 h. The reaction ends. Layers appear in the flask. The lower organic phase is taken and washed three times with water to obtain 165.4 g of a colorless liquid. A sample is taken for gas chromatography analysis. The results show that the content of 1,2-dibromo-3,3,3-trifluoropropane is 0.8%, the content of 2-bromo-3,3,3-trifluoropropene is 97.2%, other components are 2.0%, and the reaction yield is 91.7%.

[0075] Preparation of 1,2,2-tribromo-3,3,3-trifluoropropane: The reactor is a 500 mL three-necked flask. One neck is connected to a thermometer, one neck is connected to a reflux pipe, and one neck is connected to a constant pressure dropping funnel. The upper end of the reflux pipe is connected to a gas guide tube, which is led into a tail gas absorption device, and circulating water at 20 °C is introduced into the reflux pipe. A magnetic rotor and 160 g (1 mol) of bromine are successively added to the three-necked flask. Stirring and heating are started. When the temperature reaches 40 °C, 2-bromo-3,3,3-propene prepared in the above step is added dropwise. When the reaction solution changes from dark brown to light yellow, the feeding is stopped. The total amount of 2-bromo-3,3,3-propene added is 189 g (1.08 mol). After continuing the reaction for 1 h, the reaction ends. The reaction liquid is washed with 5% sodium carbonate solution and water to obtain 330.2 g of an organic phase. Sampling is carried out for gas chromatography analysis. The results show that the content of 1,2,2-tribromo-3,3,3-trifluoropropane is 98.7%, the content of 2-bromo-3,3,3-propene is 0.4%, and the others are 0.9%. The reaction yield is 97.6%.

[0076] Preparation of 1,2-dibromo-3,3,3-trifluoropropene: The reactor is a 500 mL three-necked flask. One neck is connected to a thermometer, one neck is connected to a constant pressure dropping funnel, and one neck is sealed with a hollow plug. A magnetic rotor, 120 mL of water and 48 g (1.2 mol) of sodium hydroxide are successively added to the three-necked flask. Stirring and heating are started. When the temperature reaches 50 °C, 1,2,2-tribromo-3,3,3-trifluoropropane prepared by the above method is added dropwise. The dropping rate is adjusted to control the reaction temperature at 40 °C. The total feeding amount of 1,2,2-tribromo-3,3,3-trifluoropropane is 335 g (1 mol). After the feeding is completed, the reaction continues for 3 h and then ends. Layers appear in the flask. The lower organic phase is taken and washed three times with water to obtain 235.4 g of a colorless liquid. Sampling is carried out for gas chromatography analysis. The results show that the content of 1,2,2-tribromo-3,3,3-trifluoropropane is 0.7%, the content of 1,2-dibromo-3,3,3-trifluoropropene is 97.6%, and the others are 1.7%. The reaction yield is 90.5%.

[0077] Preparation of 3,3,3-trifluoro-1-propyne: The reactor is a 1000 mL three-necked flask. One neck is connected to a thermometer, one neck is connected to a constant-pressure dropping funnel, and one neck is connected to a reflux pipe. The condenser is filled with refrigerant at 0 °C, and the rear end of the condenser is connected to a steel cylinder for collecting TFPY products. The steel cylinder is placed in a freezer at -60 °C. In a nitrogen atmosphere, a magnetic rotor, 700 mL of absolute ethanol, and 82 g (1.26 mol) of zinc powder are added to the three-necked flask in sequence. Stirring and heating are started. When reflux appears, the dried 1,2-dibromo-3,3,3-trifluoropropene prepared in the above step is added dropwise. The dropping rate is adjusted to control the reaction temperature stable. The total amount of 1,2-dibromo-3,3,3-trifluoropropene added dropwise is 254 g (1 mol). After the dropping is completed, the reaction continues for 2 h, and the reaction ends. The weight of the liquid phase collected in the metal cylinder is 87.4 g. Sampling is carried out for gas chromatography analysis. The results show that the content of 3,3,3-trifluoropropyne is 99.7%, and the others are 0.3%. The reaction yield is 92.7%.

[0078] The two-step reaction method adopted by the present invention can convert cheap 3,3,3-trifluoropropene into 3,3,3-trifluoropropyne, solving the difficulties of long reaction steps, large amounts of three wastes, and high costs in the traditional process, and having the characteristics of short steps, high yield, and less three wastes, and having good prospects for industrial production.

[0079] Comparative Example 2

[0080] The operation of this comparative example is the same as that of Example 7, except that: in step (2), the temperature of the product collection system is at room temperature, and other operations remain unchanged. After the reaction ends, there is no organic phase at the bottom of the flask. The total weight of the materials received in the steel cylinder is 15.9 g. The gas in the steel cylinder is taken for gas chromatography analysis. The results show that the content of 3,3,3-trifluoro-1-propyne is 99.4%, and the others are 0.6%. The raw material conversion rate is calculated to be close to 100%, and the reaction selectivity is 16.9%.

[0081] Comparative Example 3

[0082] The operation of this comparative example is the same as that of Example 7, except that: in step (2), the pressure of the product collection system is at atmospheric pressure, and other operations remain unchanged. After the reaction ends, there is no organic phase at the bottom of the flask. The total weight of the materials received in the steel cylinder is 28.6 g. The gas in the steel cylinder is taken for gas chromatography analysis. The results show that the content of 3,3,3-trifluoro-1-propyne is 99.6%, and the others are 0.6%. The raw material conversion rate is calculated to be close to 100%, and the reaction selectivity is 30.3%.

Claims

1. A method for preparing 3,3,3-trifluoro-1-propyne by a two-step process, characterized in that: The 3,3,3-trifluoro-1-propyne is prepared by a production system and collected by a material receiving system. The preparation steps of the production system include: (1) In a first solvent, 3,3,3-trifluoro-1-propene undergoes an addition reaction with ICl to obtain a compound of the following formula (I); (2) In a second solvent, the compound of formula (I) reacts with a base to eliminate two molecules of hydrogen halide to obtain 3,3,3-trifluoro-1-propyne shown in the following formula (II); The reaction equations are as follows:

2. The method for preparing 3,3,3-trifluoro-1-propyne by a two-step method according to claim 1, wherein: The temperature of the material receiving system is -196 to -60 °C, and the pressure is -0.03 Mpa to atmospheric pressure.

3. The method for preparing 3,3,3-trifluoro-1-propyne by a two-step process according to claim 2, characterized in that: The temperature of the material receiving system is -196 to -80 °C, and the pressure is -0.02 to -0.01 MPa.

4. The method for preparing 3,3,3-trifluoro-1-propyne by a two-step process according to claim 1, characterized in that: In step (1), the first solvent is selected from at least one of halogenated hydrocarbons, ether solvents, nitrile solvents, amide solvents, or sulfone solvents; in step (2), the second solvent is selected from at least one of water, alcohol solvents, ether solvents, nitrile solvents, amide solvents, or sulfone solvents.

5. The method for preparing 3,3,3-trifluoro-1-propyne by a two-step method according to claim 4, characterized in that: The halogenated hydrocarbon is selected from at least one of dichloromethane, dichloroethane, trichloroethane, dichloropropane, chloroform, or carbon tetrachloride; the alcohol solvent is selected from at least one of methanol, ethanol, propanol, isopropanol, ethylene glycol, or diethylene glycol; the ether solvent is selected from at least one of tetrahydrofuran, diethyl ether, or dioxane; the nitrile solvent is selected from at least one of acetonitrile, propionitrile, or butyronitrile; the amide solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, or hexamethylphosphoric triamide; the sulfone solvent is selected from dimethyl sulfoxide and / or sulfolane.

6. The method for preparing 3,3,3-trifluoro-1-propyne by a two-step process according to claim 1, wherein: In step (1), the molar ratio of ICl to 3,3,3-trifluoro-1-propene is 1:(1.0 to 1.5).

7. The method for preparing 3,3,3-trifluoro-1-propyne by a two-step method according to claim 1, characterized in that: In step (2), the base is selected from at least one of alkali metal hydroxides, alkali metal alkoxides, or alkali metal amides.

8. The method for preparing 3,3,3-trifluoro-1-propyne by a two-step method according to claim 1, characterized in that: Step (2) is carried out in the presence of a phase transfer catalyst, and the phase transfer catalyst is selected from alkyl quaternary ammonium salts containing C2-C12 alkyl groups.

9. The method for preparing 3,3,3-trifluoro-1-propyne by a two-step method according to claim 8, characterized in that: The alkyl quaternary ammonium salt is selected from at least one of tetrabutylammonium chloride, tetrabutylammonium bromide, methyltrioctylammonium chloride, or tetra(dodecyl)ammonium chloride.

10. The method for preparing 3,3,3-trifluoro-1-propyne by a two-step process according to claim 1, characterized in that: In step (2), the molar ratio of the compound of formula (I) to the base is 1:(2.0 to 10.0).

11. The method for preparing 3,3,3-trifluoro-1-propyne by a two-step method according to claim 8, characterized in that: In step (2), the molar ratio of the compound of formula (I) to the phase transfer catalyst is 1:(0.01% to 1%).

12. The method for preparing 3,3,3-trifluoro-1-propyne compound by a two-step method according to claim 1, characterized in that: The reaction temperature of step (1) is -30 to 10 °C, and the reaction time is 1 to 24 h; the reaction temperature of step (2) is room temperature to 120 °C, and the reaction time is 2 to 8 h.

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