Method for preparing trifluorobromoethylene by phase transfer catalysis
Technical Field
The invention relates to a preparation method of trifluorobromoethylene, in particular to a method for preparing trifluorobromoethylene by phase transfer catalysis.
Background
The trifluorobromoethylene has the properties of fluorine-containing olefin, comprises halogenation, hydrogenation and nucleophilic reaction, is mainly applied to polymerization reaction, and can also be used as a chemical intermediate. The metal organic intermediate is an important reagent for synthesizing trifluorovinyl compounds, such as trifluorostyrene which is a raw material for synthesizing an ion exchange membrane of a fuel ion battery, or hexafluorobutadiene which is green etching gas with excellent etching performance and low GWP value. The trifluorobromoethylene telomer can be used as the floating liquid and damping liquid of a high-precision navigation system liquid floating gyroscope and an accelerometer, and the liquids are high in price and widely used in the aerospace industry. Further, trifluorobromoethylene is also one of the three monomers (tetrafluoroethylene, perfluoromethyl perfluorovinyl ether, trifluorobromoethylene) required to prepare cured fluororubbers.
The synthesis process of the trifluorobromoethylene mainly comprises two routes, namely a route taking the trifluoroethylene as a starting material and a route taking the trifluorochloroethylene as a starting material. Chemists at the end of the nineteenth century added Br2To CF2Preparation of CF ═ CFH2BrCHFBr(K2CO3 and KOAc in ethanol solution), and the product 1, 2-dibromo-1, 1, 2-trifluoroethane is further treated with a base (sodium hydroxide, potassium hydroxide, etc. are present)And removing hydrogen bromide to obtain the product of trifluorobromoethylene. The reaction equation is as follows:
the trifluorobromoethylene is prepared by taking chlorotrifluoroethylene as a raw material, four steps are needed, the total yield is about 60 percent, and the reaction equation is as follows:
CF2=CFCl+HBr→CF2BrCFClH (2)
CF2BrCFClH+Zn→CF2=CHF+ZnBrCl
CF2=CHF+Br2→CF2BrCHFBr
CF2BrCHFBr+KOH→CF2=CFBr+KBr+H2O
the intermediate products in the two routes are 1, 2-dibromo-1, 1, 2-trifluoroethane, and the subsequent steps for preparing the trifluorobromoethylene by dehydrobromination of the 1, 2-dibromo-1, 1, 2-trifluoroethane are the same, wherein the step of dehydrobromination of the 1, 2-dibromo-1, 1, 2-trifluoroethane is a key step for restricting the synthesis efficiency of the trifluorobromoethylene. In the traditional alkali liquor dehydrobromination process, the problems of poor mass transfer effect, long reaction time, low efficiency and the like exist because the raw material 1, 2-dibromo-1, 1, 2-trifluoroethane is insoluble in alkali liquor.
Therefore, it is necessary to develop a new method for preparing trifluorobromoethylene by dehydrobromination of 1, 2-dibromo-1, 1, 2-trifluoroethane.
Disclosure of Invention
The invention aims to provide a method for preparing trifluorobromoethylene by phase transfer catalysis, which has the advantages of high reaction speed, high synthesis efficiency, low cost, environmental protection and the like.
The technical scheme adopted by the invention for achieving the aim of the invention is as follows:
a method for preparing trifluorobromoethylene comprises the step of carrying out dehydrobromination reaction on 1, 2-dibromo-1, 1, 2-trifluoroethane in an alkali solution under the action of a phase transfer catalyst to generate trifluorobromoethylene, wherein:
the alkali solution is an aqueous solution or an alcoholic solution of alkali, the alkali is selected from KOH and/or NaOH, and the alcohol is selected from one, two or more than three of methanol, ethanol, n-propanol, isopropanol, n-butanol and cyclohexanol;
the phase transfer catalyst is selected from one, two or more than three of tetramethylammonium bromide, tetraethylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium hydrogen sulfate, dodecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, tetradecyltrimethylammonium chloride, tetradecyltrimethylammonium bromide and hexadecyltrimethylammonium bromide.
The alkaline solution used in the invention can be an alkaline aqueous solution or an alkaline alcoholic solution; the mass percentage concentration of the alkali solution is preferably 5.0-40.0%, and more preferably 15.0-30.0%. Suitable alcohols are preferably one, two or more combinations of three or more selected from methanol, ethanol, n-propanol, isopropanol, n-butanol and cyclohexanol, and more preferably one, two or three selected from ethanol, n-propanol and isopropanol.
The invention uses phase transfer catalyst to improve the effective contact between alkali and 1, 2-dibromo-1, 1, 2-trifluoroethane, improve mass transfer effect, greatly accelerate reaction rate and shorten reaction time. Suitable phase transfer catalysts are selected from one, two or more than three combinations of tetramethyl ammonium bromide, tetraethyl ammonium bromide, tetrabutyl ammonium chloride, tetrabutyl ammonium hydrogen sulfate, dodecyl trimethyl ammonium chloride, dodecyl trimethyl ammonium bromide, tetradecyl trimethyl ammonium chloride, tetradecyl trimethyl ammonium bromide and hexadecyl trimethyl ammonium bromide; preferably one, two or more of tetramethylammonium bromide, tetraethylammonium bromide, dodecyltrimethylammonium bromide and hexadecyltrimethylammonium bromide.
The amount of the phase transfer catalyst to be used in the present invention is preferably 0.1 to 5.0% by mass of 1, 2-dibromo-1, 1, 2-trifluoroethane, and more preferably 0.5 to 2.0% by mass of 1, 2-dibromo-1, 1, 2-trifluoroethane. The amount of the base to be added used in the present invention is preferably 0.5 to 4.0 times the molar amount of 1, 2-dibromo-1, 1, 2-trifluoroethane, and more preferably 1.5 to 2.0 times the molar amount of 1, 2-dibromo-1, 1, 2-trifluoroethane.
In the method for preparing the trifluorobromoethylene, the used phase transfer catalyst and the aqueous solution or the alcoholic solution of the alkali can be recycled, and the yield of the trifluorobromoethylene is not influenced.
The raw material 1, 2-dibromo-1, 1, 2-trifluoroethane used in the present invention may be prepared from trifluoroethylene or chlorotrifluoroethylene.
The invention also provides a process for preparing trifluorobromoethylene, which comprises the following steps:
(1) preparing a certain amount of alkali solution, and putting the alkali solution into a reactor, wherein the mass percentage concentration of the alkali solution is 5.0-40.0%;
(2) adding a phase transfer catalyst in a certain proportion into a reactor, wherein the amount of the added phase transfer catalyst is 0.1-5.0% of the mass of 1, 2-dibromo-1, 1, 2-trifluoroethane;
(3) starting a stirring and condensing reflux device, and raising the temperature to 40-120 ℃;
(4) dropwise adding the raw material 1, 2-dibromo-1, 1, 2-trifluoroethane into a reactor, controlling the addition amount of alkali to be 0.5-4.0 times of the molar weight of the 1, 2-dibromo-1, 1, 2-trifluoroethane, and collecting the product by adopting low-temperature cold hydrazine;
(5) after the dropwise addition of the 1, 2-dibromo-1, 1, 2-trifluoroethane is finished, preserving the heat for 1-8 h;
(6) cooling to room temperature, filtering, and separating to obtain an organic phase and an aqueous phase, wherein the organic phase is trifluorobromoethylene.
And for the water phase obtained in the reaction, a certain amount of alkali is added into the water phase, so that bromide salt solid can be separated out and filtered, and the liquid can be used as alkali liquor for the next reaction, so that the recycling of waste alkali liquor is realized, and the three-waste treatment amount is greatly reduced.
Compared with the prior art, the invention has the following advantages: under the condition of not changing the original reaction system and reaction conditions, the effective contact of reaction materials is promoted by adding a phase transfer catalyst, the mass transfer effect is improved, the reaction rate can be accelerated, the reaction time is shortened, and the production efficiency is improved; meanwhile, the cyclic application of the phase transfer catalyst and the alkali liquor can be realized, the three wastes are reduced, and the production cost is reduced.
Detailed Description
The present invention is further illustrated by the following examples, which are not intended to limit the invention to these embodiments. It will be appreciated by those skilled in the art that the present invention encompasses all alternatives, modifications and equivalents as may be included within the scope of the claims.
Example 1
And (3) placing a 250ml three-neck flask in an oil bath pot, wherein 1# cold hydrazine is loaded on the three-neck flask for refluxing unreacted raw materials, the temperature of the 1# cold hydrazine is-2 ℃, then 2# cold hydrazine is loaded for collecting products after the 1# cold hydrazine, and the temperature of the 2# cold hydrazine is-20 ℃. 69g of 30% KOH and 0.9g of dodecyltrimethylammonium chloride were charged in a three-necked flask, and 60g of the starting material 1, 2-dibromo-1, 1, 2-trifluoroethane was charged into a constant-pressure funnel (NaOH: CF)2BrCHFBr ═ 1.5:1 molar ratio). When the temperature of the oil bath kettle is raised to 70 ℃, the CF raw material is dripped into the three-neck flask while stirring2And keeping the temperature for 5 hours after the BrCHFBr is added. The reaction results are shown in Table 1.
Example 2
And (3) placing a 250ml three-neck flask in an oil bath pot, wherein 1# cold hydrazine is loaded on the three-neck flask for refluxing unreacted raw materials, the temperature of the 1# cold hydrazine is-2 ℃, then 2# cold hydrazine is loaded for collecting products after the 1# cold hydrazine, and the temperature of the 2# cold hydrazine is-20 ℃. 69g of 30% KOH and 0.9g of dodecyltrimethylammonium chloride were charged in a three-necked flask, and 60g of the starting material 1, 2-dibromo-1, 1, 2-trifluoroethane was charged into a constant-pressure funnel (NaOH: CF)2BrCHFBr ═ 1.5:1 molar ratio). When the temperature of the oil bath kettle is raised to 70 ℃, the CF raw material is dripped into the three-neck flask while stirring2And keeping the temperature for 4 hours after the completion of the BrCHFBr dropping. The reaction results are shown in Table 1.
Example 3
And (3) placing a 250ml three-neck flask in an oil bath pot, wherein 1# cold hydrazine is loaded on the three-neck flask for refluxing unreacted raw materials, the temperature of the 1# cold hydrazine is-2 ℃, then 2# cold hydrazine is loaded for collecting products after the 1# cold hydrazine, and the temperature of the 2# cold hydrazine is-20 ℃. 69g of 30% KOH and 0.9g of dodecyltrimethylammonium chloride were charged in a three-necked flask, and 60g of the starting material 1, 2-dibromo-1, 1, 2-trifluoroethane was charged into a constant-pressure funnel (NaOH: CF)2BrCHFBr=1.5:1 molar ratio). When the temperature of the oil bath kettle is raised to 70 ℃, the CF raw material is dripped into the three-neck flask while stirring2And keeping the temperature for 3 hours after the completion of the BrCHFBr dropping. The reaction results are shown in Table 1.
Example 4
And (3) placing a 250ml three-neck flask in an oil bath pot, wherein 1# cold hydrazine is loaded on the three-neck flask for refluxing unreacted raw materials, the temperature of the 1# cold hydrazine is-2 ℃, then 2# cold hydrazine is loaded for collecting products after the 1# cold hydrazine, and the temperature of the 2# cold hydrazine is-20 ℃. 69g of 30% KOH and 0.9g of tetrabutylammonium bromide were charged in a three-necked flask, and 60g of the starting material 1, 2-dibromo-1, 1, 2-trifluoroethane were charged into a constant-pressure funnel (NaOH: CF)2BrCHFBr ═ 1.5:1 molar ratio). When the temperature of the oil bath kettle is raised to 70 ℃, the CF raw material is dripped into the three-neck flask while stirring2And keeping the temperature for 3 hours after the completion of the BrCHFBr dropping. The reaction results are shown in Table 1.
Example 5
And (3) placing a 250ml three-neck flask in an oil bath pot, wherein 1# cold hydrazine is loaded on the three-neck flask for refluxing unreacted raw materials, the temperature of the 1# cold hydrazine is-2 ℃, then 2# cold hydrazine is loaded for collecting products after the 1# cold hydrazine, and the temperature of the 2# cold hydrazine is-20 ℃. 69g of 30% KOH and 0.9g of tetramethylammonium bromide were charged in a three-necked flask, and 60g of the starting material 1, 2-dibromo-1, 1, 2-trifluoroethane was charged into a constant-pressure funnel (NaOH: CF)2BrCHFBr ═ 1.5:1 molar ratio). When the temperature of the oil bath kettle is raised to 70 ℃, the CF raw material is dripped into the three-neck flask while stirring2And keeping the temperature for 3 hours after the completion of the BrCHFBr dropping. The reaction results are shown in Table 1.
Example 6
And (3) placing a 250ml three-neck flask in an oil bath pot, wherein 1# cold hydrazine is loaded on the three-neck flask for refluxing unreacted raw materials, the temperature of the 1# cold hydrazine is-2 ℃, then 2# cold hydrazine is loaded for collecting products after the 1# cold hydrazine, and the temperature of the 2# cold hydrazine is-20 ℃. 69g of 30% KOH and 0.9g of cetyltrimethylammonium bromide were charged into a three-necked flask, and 60g of the starting material 1, 2-dibromo-1, 1, 2-trifluoroethane was charged into a constant-pressure funnel (NaOH: CF)2BrCHFBr ═ 1.5:1 molar ratio). When the temperature of the oil bath kettle is raised to 70 ℃, the CF raw material is dripped into the three-neck flask while stirring2And keeping the temperature for 3 hours after the completion of the BrCHFBr dropping. The reaction results are shown in Table 1.
Example 7
And (3) placing a 250ml three-neck flask in an oil bath pot, wherein 1# cold hydrazine is loaded on the three-neck flask for refluxing unreacted raw materials, the temperature of the 1# cold hydrazine is-2 ℃, then 2# cold hydrazine is loaded for collecting products after the 1# cold hydrazine, and the temperature of the 2# cold hydrazine is-20 ℃. 69g of 30% KOH and 1.2g of dodecyltrimethylammonium chloride were placed in a three-necked flask, and 60g of the starting material 1, 2-dibromo-1, 1, 2-trifluoroethane was charged into a constant-pressure funnel (NaOH: CF)2BrCHFBr ═ 1.5:1 molar ratio). When the temperature of the oil bath kettle is raised to 70 ℃, the CF raw material is dripped into the three-neck flask while stirring2And keeping the temperature for 3 hours after the completion of the BrCHFBr dropping. The reaction results are shown in Table 1.
Example 8
And (3) placing a 250ml three-neck flask in an oil bath pot, wherein 1# cold hydrazine is loaded on the three-neck flask for refluxing unreacted raw materials, the temperature of the 1# cold hydrazine is-2 ℃, then 2# cold hydrazine is loaded for collecting products after the 1# cold hydrazine, and the temperature of the 2# cold hydrazine is-20 ℃. 69g of 30% KOH and 0.6g of dodecyltrimethylammonium chloride were charged into a three-necked flask, and 60g of the starting material 1, 2-dibromo-1, 1, 2-trifluoroethane was charged into a constant-pressure funnel (NaOH: CF)2BrCHFBr ═ 1.5:1 molar ratio). When the temperature of the oil bath kettle is raised to 70 ℃, the CF raw material is dripped into the three-neck flask while stirring2And keeping the temperature for 3 hours after the completion of the BrCHFBr dropping. The reaction results are shown in Table 1.
Example 9
And (3) placing a 250ml three-neck flask in an oil bath pot, wherein 1# cold hydrazine is loaded on the three-neck flask for refluxing unreacted raw materials, the temperature of the 1# cold hydrazine is-2 ℃, then 2# cold hydrazine is loaded for collecting products after the 1# cold hydrazine, and the temperature of the 2# cold hydrazine is-20 ℃. 69g of 30% KOH and 0.3g of dodecyltrimethylammonium chloride were charged in a three-necked flask, and 60g of the starting material 1, 2-dibromo-1, 1, 2-trifluoroethane was charged into a constant-pressure funnel (NaOH: CF)2BrCHFBr ═ 1.5:1 molar ratio). When the temperature of the oil bath kettle is raised to 70 ℃, the CF raw material is dripped into the three-neck flask while stirring2And keeping the temperature for 3 hours after the completion of the BrCHFBr dropping. The reaction results are shown in Table 1.
Comparative example 1
Placing 250ml three-neck flask in oil bath pot, loading 1# cold hydrazine on the three-neck flask for refluxing unreacted raw material,the temperature of the 1# cold hydrazine is-2 ℃, the 1# cold hydrazine is then added with the 2# cold hydrazine for collecting the product, and the temperature of the 2# cold hydrazine is-20 ℃. 69g of 20% NaOH were charged into a three-necked flask, and 60g of 1, 2-dibromo-1, 1, 2-trifluoroethane as a raw material was charged into a constant-pressure funnel (NaOH: CF)2BrCHFBr ═ 1.5:1 molar ratio). When the temperature of the oil bath kettle is raised to 70 ℃, the CF raw material is dripped into the three-neck flask while stirring2And keeping the temperature for 5 hours after the BrCHFBr is added. The reaction results are shown in Table 1.
Comparative example 2
And (3) placing a 250ml three-neck flask in an oil bath pot, wherein 1# cold hydrazine is loaded on the three-neck flask for refluxing unreacted raw materials, the temperature of the 1# cold hydrazine is-2 ℃, then 2# cold hydrazine is loaded for collecting products after the 1# cold hydrazine, and the temperature of the 2# cold hydrazine is-20 ℃. 69g of 20% NaOH were charged into a three-necked flask, and 60g of 1, 2-dibromo-1, 1, 2-trifluoroethane as a raw material was charged into a constant-pressure funnel (NaOH: CF)2BrCHFBr ═ 1.5:1 molar ratio). When the temperature of the oil bath kettle is raised to 120 ℃, the CF raw material is dripped into the three-neck flask while stirring2And keeping the temperature for 5 hours after the BrCHFBr is added. The reaction results are shown in Table 1.
Comparative example 3
And (3) placing a 250ml three-neck flask in an oil bath pot, wherein 1# cold hydrazine is loaded on the three-neck flask for refluxing unreacted raw materials, the temperature of the 1# cold hydrazine is-2 ℃, then 2# cold hydrazine is loaded for collecting products after the 1# cold hydrazine, and the temperature of the 2# cold hydrazine is-20 ℃. 33g of 20% NaOH was charged into a three-necked flask, and 60g of 1, 2-dibromo-1, 1, 2-trifluoroethane as a raw material was charged into a constant-pressure funnel (NaOH: CF)2BrCHFBr ═ 0.7:1 molar ratio). When the temperature of the oil bath kettle is raised to 70 ℃, the CF raw material is dripped into the three-neck flask while stirring2And keeping the temperature for 5 hours after the BrCHFBr is added. The reaction results are shown in Table 1.
Comparative example 4
And (3) placing a 250ml three-neck flask in an oil bath pot, wherein 1# cold hydrazine is loaded on the three-neck flask for refluxing unreacted raw materials, the temperature of the 1# cold hydrazine is-2 ℃, then 2# cold hydrazine is loaded for collecting products after the 1# cold hydrazine, and the temperature of the 2# cold hydrazine is-20 ℃. 115g of 20% NaOH was charged into a three-necked flask, and 60g of 1, 2-dibromo-1, 1, 2-trifluoroethane as a raw material was charged into a constant-pressure funnel (NaOH: CF)2BrCHFBr ═ 2.5:1 molar ratio).When the temperature of the oil bath kettle is raised to 70 ℃, the CF raw material is dripped into the three-neck flask while stirring2And keeping the temperature for 5 hours after the BrCHFBr is added. The reaction results are shown in Table 1.
Comparative example 5
And (3) placing a 250ml three-neck flask in an oil bath pot, wherein 1# cold hydrazine is loaded on the three-neck flask for refluxing unreacted raw materials, the temperature of the 1# cold hydrazine is-2 ℃, then 2# cold hydrazine is loaded for collecting products after the 1# cold hydrazine, and the temperature of the 2# cold hydrazine is-20 ℃. 161g of 20% NaOH was charged into a three-necked flask, and 60g of 1, 2-dibromo-1, 1, 2-trifluoroethane as a raw material was charged into a constant-pressure funnel (NaOH: CF)2BrCHFBr ═ 3.5:1 molar ratio). When the temperature of the oil bath kettle is raised to 70 ℃, the CF raw material is dripped into the three-neck flask while stirring2And keeping the temperature for 5 hours after the BrCHFBr is added. The reaction results are shown in Table 1.
TABLE 1 results of reactions carried out under different conditions
From the results in table 1, it can be seen that, after the phase transfer catalyst is added to the reaction system, since the phase transfer catalyst promotes effective contact of the reaction materials, improves the mass transfer effect, and accelerates the reaction rate, the conversion rate of the reaction is obviously increased under the same heat preservation time, and even if the heat preservation time is shortened, the conversion rate of the reaction is also obviously higher than that of the reaction system without the catalyst.
Example 10
This example describes the process of the present invention for recycling a phase transfer catalyst and a basic solution: after the first reaction is finished, cooling to room temperature, filtering bromide salt, and separating the organic phase and the water phase; and adding a certain amount of alkali into the water phase until the concentration of the alkali liquor is 30%, filtering to remove bromide salt solid precipitated at the moment, wherein a certain amount of the catalyst is lost in the process of filtering and liquid separation, and the catalyst needs to be added for each time of application, other specific reaction operations are the same as those in comparative example 1, the reaction temperature is 70 ℃, the alkali liquor is 30% KOH solution, the heat preservation time is 3 hours, and the reaction results are shown in Table 2.
TABLE 2 reaction results of the phase transfer catalyst and the lye used repeatedly