Preparation method of 1, 1-difluoro-2-vinyl iodide

Abstract

The invention relates to the field of fluorine-containing fine chemicals, and particularly provides a preparation method of 1, 1-difluoro-2-vinyl iodide, which comprises the following steps: taking elemental iodine and vinylidene fluoride as raw materials, carrying out photocatalysis to obtain an intermediate product, and adding an alkali metal catalyst to obtain the 1, 1-difluoro-2-vinyl iodide. The method has the characteristics of simple process, low cost, high yield and the like.

Description

Technical Field

[0001] This invention relates to the field of fluorine-containing fine chemicals, specifically to a method for preparing 1,1-difluoro-2-iodoethylene. Background Technology

[0002] 1,1-Difluoro-2-iodoethylene can be used as an intermediate raw material for the production of fluorinated resins and fluorinated rubber modifying monomers, fluorinated additives, and other fluorinated fine chemicals. Furthermore, due to the presence of olefin bonds in the molecule, its molecular stability is relatively low, making it easily degraded in the environment, resulting in good overall environmental friendliness. In addition, the introduction of monomers with high vulcanization points, such as iodine and bromine, into fluorinated elastomers can significantly improve the low-temperature performance and mechanical properties of the vulcanizate. Therefore, the preparation technology of 1,1-difluoro-2-iodoethylene has attracted widespread attention.

[0003] There are few literature reports on the synthesis of 1,1-difluoro-2-iodoethylene. It is usually synthesized by the addition reaction of iodine monochloride (ICl) with vinylidene fluoride to 1-chloro-1,1-difluoro-2-iodoethane; then, 1-chloro-1,1-difluoro-2-iodoethane is dehydrochlorinated under alkaline conditions to synthesize 1,1-difluoro-2-iodoethylene. While this method can yield the product, it suffers from several drawbacks. Firstly, the raw material ICl is expensive (market price approximately RMB 15,000 / kg) and has disadvantages such as volatility, decomposition, and difficulty in obtaining and storing it. Secondly, the process is highly exothermic, making it difficult to control the system temperature, and high temperatures can easily generate other byproducts.

[0004] Patent EP 845482 A1 and the literature Ehm Christian, Fluorinated butatrienes [J]. Journal of Fluorine Chemistry, 2010, 131(11): 1173-1181 both use vinylidene fluoride (VDF) and ICl as raw materials for addition reaction, followed by dechlorination reaction in the presence of phase transfer catalyst and organic or inorganic base. Although this process can produce qualified products, the overall yield is low.

[0005] Patent CN 112062651 A discloses a method for synthesizing 1,1-difluoro-2-iodoethylene, which also uses ICl as a raw material. In addition, the subsequent dechlorination adopts a fixed-bed gas phase pyrolysis process, which not only has high energy consumption but also generates a large number of by-products.

[0006] Patent CN 113307720 A, in an attempt to address the high cost of ICl, uses VDF and chlorine to react, then reacts the resulting intermediate with KI to obtain 1-chloro-1,1-difluoro-2-iodoethane. This intermediate is then dechlorinated using a magnetic catalyst to yield 1,1-difluoro-2-iodoethylene. However, this process uses chlorine, a hazardous chemical, as a raw material, increasing the risk and hindering industrial-scale implementation. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a method for preparing 1,1-difluoro-2-iodoethylene. The preparation method is simple, uses inexpensive and readily available raw materials, has low cost, and high yield.

[0008] A method for preparing 1,1-difluoro-2-iodoethylene, comprising: (1) Iodine was added to a reaction vessel containing solvent, vinylidene fluoride was introduced, and the reaction was carried out under photocatalytic conditions. After the reaction was completed, the intermediate product 1,2-diiodo-1,1-difluoroethane was collected by alkaline washing and distillation. (2) The intermediate product 1,2-diiodo-1,1-difluoroethane was added to a slurry bed reactor. An inert solvent and an alkali metal catalyst were added to the slurry bed reactor to carry out the reaction. After the reaction was completed, 1,1-difluoro-2-iodoethylene was collected by distillation.

[0009] The chemical equation for the above preparation method is as follows:

[0010] Preferably, the reaction vessel is filled with a nitrogen atmosphere.

[0011] The molar ratio of vinylidene fluoride to iodine in step (1) is (0.9~1.5):1.

[0012] The solvent mentioned in step (1) is at least one of diethyl ether, tetrahydrofuran, and diethylene oxide.

[0013] The reaction temperature in step (1) is 40~100℃ and the reaction time is 8~24h.

[0014] The photocatalysis mentioned in step (1) refers to infrared light irradiation, wherein the intensity of the infrared light irradiation is 1000~2500mW / cm². 2 .

[0015] In step (1), the alkaline washing solution is an aqueous solution of Na2S2O4.

[0016] The inert solvent mentioned in step (2) is one of carbon tetrachloride, chloroform, N,N-dimethylformamide, and dimethyl sulfoxide (DMSO); preferably one of N,N-dimethylformamide and dimethyl sulfoxide.

[0017] The alkali metal catalyst mentioned in step (2) is a supported metal SiO2 catalyst. Preferably, the alkali metal catalyst is one of Mg / SiO2, Fe / SiO2, Ce / SiO2, Zn / SiO2, Co / SiO2 or Ni / SiO2; more preferably, it is one of Fe / SiO2, Ce / SiO2 or Mg / SiO2.

[0018] More preferably, the alkali metal catalyst has a particle size of 40-80 mesh.

[0019] The mass ratio of the intermediate product, inert solvent, and alkali metal catalyst mentioned in step (2) is 1:(1~20):(0.05~0.3).

[0020] In step (2), the reaction time is 3-12 hours and the reaction temperature is 50-200℃.

[0021] Compared with the prior art, the present invention has the following advantages: 1. The preparation method provided by the present invention uses abundant and inexpensive raw materials, and the process is simple, overcoming the safety risks and high prices associated with the use of iodine chloride in the prior art.

[0022] 2. This invention uses a slurry bed process for dehalogenation, which has relatively mild reaction conditions and allows for the recycling of the catalyst and solvent after the reaction. Moreover, the iodide salts generated after the slurry bed process can be oxidized to prepare elemental iodine again, which effectively reduces costs. Attached Figure Description

[0023] Figure 1 This is a gas chromatogram of 1,1-difluoro-2-iodoethylene prepared in Example 2. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to specific embodiments, but the present invention is not limited to the following embodiments. Unless otherwise specified, the raw materials described are all commercially available products. The catalysts Ce / SiO2, Fe / SiO2, Mg / SiO2, and Zn / SiO2 are all prepared by equal-volume impregnation method, with an alkali metal loading of 10%. During the preparation process, all catalysts are calcined at 600°C for 3 hours, then heated to 500°C and reduced for 6 hours under an Ar / H2 atmosphere, and the particle size is screened to be 40-60 mesh.

[0025] Example 1 126.9 g (0.5 mol) of elemental iodine was added to a 500 mL reactor. The reactor was evacuated and purged with N2. Then, 300 mL of diethyl ether was added to the reactor as a solvent using a micro-pressure feed pump. The reactor was heated to 40 °C and stirred for 30 min. 0.75 mol of vinylidene fluoride (VDF) was then introduced into the reactor, and the light source was turned on for infrared irradiation (irradiation intensity of 1000 mW / cm²). 2 The reaction was carried out for 24 hours. After the reaction, the reactor was cooled to room temperature, and the material was removed and placed in a reaction flask. 200 mL of a 0.2 mol / L Na₂S₂O₄ aqueous solution was added to the reaction flask, stirred, and residual iodine was removed. The organic phase was collected as separate layers. The organic phase was distilled to separate the solvent diethyl ether, which was recovered and reused. The intermediate product 1,2-diiodo-1,1-difluoroethane was collected with a purity of 96.1% and a yield of 93.3%. The reactor was a photocatalytic reactor.

[0026] 10 g of 40-60 mesh Ce / SiO2 catalyst was added to a slurry bed reactor containing 300 mL of N,N-dimethylformamide (DMF) solvent. 79.5 g (0.25 mol) of the intermediate product 1,2-diiodo-1,1-difluoroethane was weighed and slowly added to the slurry bed reactor. The reaction system was heated to 50 °C and reacted for 12 h. After the reaction was completed, different fractions of the intermediate product 1,2-diiodo-1,1-difluoroethane and the product 1,1-difluoro-2-iodoethylene were collected by distillation and cooling, respectively. The purity of the product 1,1-difluoro-2-iodoethylene was 98.2%, and the yield was 91.2%.

[0027] In this embodiment, the total yield of 1,1-difluoro-2-iodoethylene prepared was 85.1%.

[0028] Example 2 126.9 g (0.5 mol) of elemental iodine was added to a 500 mL reactor. The reactor was evacuated and purged with N2. Then, 300 mL of tetrahydrofuran was added to the reactor as a solvent using a micro-pressure feed pump. The reactor was heated to 80 °C and stirred for 30 min. 0.75 mol of VDF was then introduced into the reactor, and the light source was turned on for infrared irradiation (irradiation intensity of 1500 mW / cm²). 2 The reaction was carried out for 24 hours. After the reaction, the reactor was cooled to room temperature, and the material was removed and placed in a reaction flask. 200 mL of a 0.2 mol / L Na₂S₂O₄ aqueous solution was added to the reaction flask, stirred, and residual iodine was removed. The organic phase was collected as separate layers. The organic phase was distilled to separate the solvent, which was then recovered and reused. The intermediate product 1,2-diiodo-1,1-difluoroethane was collected with a purity of 96.8% and a yield of 98.4%. The reactor was a photocatalytic reactor.

[0029] 5 g of 40-60 mesh Ce / SiO2 catalyst was added to a slurry bed reactor containing 300 mL of DMF solvent. 79.5 g (0.25 mol) of the intermediate product 1,2-diiodo-1,1-difluoroethane was slowly added to the reactor. The reaction system was heated to 180 °C and reacted for 8 h. After the reaction was complete, different fractions of the intermediate product 1,2-diiodo-1,1-difluoroethane and the product 1,1-difluoro-2-iodoethylene were collected by distillation and cooling. The purity of the product 1,1-difluoro-2-iodoethylene was 99.4%, and the yield was 97.3%.

[0030] In this embodiment, the total yield of 1,1-difluoro-2-iodoethylene prepared was 95.7%.

[0031] Example 3 126.9 g (0.5 mol) of elemental iodine was added to a 500 mL reactor. The reactor was evacuated and purged with N2. Then, 300 mL of tetrahydrofuran was added to the reactor as a solvent using a micro-pressure feed pump. The reactor was heated to 100 °C and stirred for 30 min. 0.6 mol of VDF was then introduced into the reactor, and the light source was turned on for infrared irradiation (irradiation intensity of 2000 mW / cm²). 2 The reaction was carried out for 24 hours. After the reaction, the reactor was cooled to room temperature, and the material was removed and placed in a reaction flask. 200 mL of a 0.2 mol / L Na₂S₂O₄ aqueous solution was added to the reaction flask, stirred, and residual iodine was removed. The organic phase was collected as separate layers. The organic phase was distilled to separate the solvent, which was then recovered and reused. The intermediate product 1,2-diiodo-1,1-difluoroethane was collected with a purity of 98.0% and a yield of 95.6%. The reactor was a photocatalytic reactor.

[0032] 5 g of 40-60 mesh Fe / SiO2 catalyst was added to a slurry-bed reactor containing 300 mL of dimethyl sulfoxide (DMSO). 79.5 g (0.25 mol) of the intermediate product 1,2-diiodo-1,1-difluoroethane was weighed and slowly added to the reactor. The reaction system was heated to 200 °C and reacted for 3 h. After the reaction was complete, different fractions of the intermediate product 1,2-diiodo-1,1-difluoroethane and the product 1,1-difluoro-2-iodoethylene were collected by distillation and cooling. The purity of the product 1,1-difluoro-2-iodoethylene was 96.9%, and the yield was 95.4%.

[0033] In this embodiment, the total yield of 1,1-difluoro-2-iodoethylene prepared was 91.2%.

[0034] Example 4 126.9 g (0.5 mol) of elemental iodine was added to a 500 mL reactor. The reactor was evacuated and purged with N2. Then, 300 mL of diethylene oxide was added to the reactor as a solvent using a micro-pressure feed pump. The reactor was heated to 80 °C and stirred for 30 min. 0.45 mol of VDF was then introduced into the reactor, and the light source was turned on for infrared irradiation (irradiation intensity of 2500 mW / cm²). 2 The reaction was carried out for 24 hours. After the reaction, the reactor was cooled to room temperature, and the material was removed and placed in a reaction flask. 200 mL of a 0.2 mol / L Na₂S₂O₄ aqueous solution was added to the reaction flask, stirred, and residual iodine was removed. The organic phase was collected as separates. The organic phase was distilled to separate the solvent, which was then recovered and reused. The intermediate product 1,2-diiodo-1,1-difluoroethane was collected with a purity of 97.6% and a yield of 94.5%. The reactor was a photocatalytic reactor.

[0035] 5g of 40-60 mesh Mg / SiO2 catalyst was added to a slurry bed reactor containing 300 ml of DMF solvent. 79.5g (0.25mol) of the intermediate product 1,2-diiodo-1,1-difluoroethane was slowly added to the reactor. The reaction system was heated to 80℃ and reacted for 8 hours. After the reaction was complete, different fractions of the intermediate product 1,2-diiodo-1,1-difluoroethane and the product 1,1-difluoro-2-iodoethylene were collected by distillation and cooling. The purity of the product 1,1-difluoro-2-iodoethylene was 97.6%, and the yield was 96.2%.

[0036] In this embodiment, the total yield of 1,1-difluoro-2-iodoethylene prepared was 90.9%.

[0037] Example 5 This embodiment is the same as Example 2, except that the alkali metal catalyst is Zn / SiO2.

[0038] Examples 6-8 This embodiment is the same as Example 2, except that the reaction temperatures of elemental iodine and vinylidene fluoride are 40, 60, and 100°C, respectively.

[0039] Examples 9-12 This embodiment is the same as Example 2, except that the catalytic reaction temperatures of the intermediate products are 50, 100, 150, and 200°C, respectively.

[0040] Comparative Example 1 81.2 g (0.5 mol) of iodine chloride was added to a 500 mL reactor. The reactor was evacuated and purged with N2, and then heated to 55 °C. 0.75 mol of VDF was introduced into the reactor, and the reaction was allowed to proceed for 24 h. After the reaction was complete, the reactor was cooled to room temperature, and the material was removed and placed in a reaction flask. 200 mL of a 0.2 mol / L Na2S2O4 aqueous solution was added to the reaction flask, and the mixture was stirred to remove residual iodine chloride. The organic phase was collected as a separate layer. The organic phase was distilled to separate the solvent, which was then recovered and reused. The intermediate product, 1-chloro-1,1-difluoro-2-iodoethane, was collected with a purity of 98.9% and a yield of 88.4%.

[0041] 5 g of 40-60 mesh Ce / SiO2 catalyst was added to a slurry bed reactor containing 300 mL of DMF solvent. 56.5 g (0.25 mol) of the intermediate product 1-chloro-1,1-difluoro-2-iodoethane was slowly added to the reactor. The reaction system was heated to 180 °C and reacted for 8 h. After the reaction was complete, different fractions of the intermediate product 1-chloro-1,1-difluoro-2-iodoethane and the product 1,1-difluoro-2-iodoethylene were collected by distillation and cooling. The purity of the product 1,1-difluoro-2-iodoethylene was 97.9%, the yield was 78.3%, and the overall yield was 69.2%.

[0042] Comparative Example 2 81.2 g (0.5 mol) of iodine chloride was added to a 500 mL reactor. The reactor was evacuated and purged with N2, and then heated to 80 °C. 0.6 mol of VDF was introduced into the reactor, and the reaction was allowed to proceed for 24 h. After the reaction was complete, the reactor was cooled to room temperature, and the material was removed and placed in a reaction flask. 200 mL of a 0.2 mol / L Na2S2O4 aqueous solution was added to the reaction flask, and the mixture was stirred to remove residual iodine chloride. The organic phase was collected as separates. The organic phase was distilled to separate the solvent, which was then recovered and reused. The intermediate product, 1-chloro-1,1-difluoro-2-iodoethane, was collected with a purity of 98.0% and a yield of 85.6%.

[0043] 5g of 40-60 mesh Ni / SiO2 catalyst was added to a slurry bed reactor containing 300mL of DMF solvent. 56.5g (0.25mol) of the intermediate product 1-chloro-1,1-difluoro-2-iodoethane was slowly added to the reactor. The reaction system was heated to 180℃ and reacted for 8 hours. After the reaction was complete, different fractions of the intermediate product 1-chloro-1,1-difluoro-2-iodoethane and the product 1,1-difluoro-2-iodoethylene were collected by distillation and cooling. The purity of the product 1,1-difluoro-2-iodoethylene was 98.2%, the yield was 72.3%, and the overall yield was 61.9%.

[0044] Table 1. Experimental results of Examples 1-12 and Comparative Examples 1-2

[0045] Table 1 shows the experimental results of each example and comparative example. It can be seen from the table that the overall yield of Examples 1-12 is significantly improved compared to Comparative Examples 1 and 2. Compared to Example 5, Examples 1-4, using Ce / SiO2, Fe / SiO2, and Mg / SiO2 as alkaline earth metal catalysts, show a significant increase in the yield of the second-step product. Comparing Examples 2 and 6-8, it can be seen that as the reaction temperature of iodine and vinylidene fluoride increases, the yield of the intermediate product first increases and then decreases. The reaction temperature has a relatively small impact on the purity of the intermediate product, but it also shows a trend of first increasing and then decreasing. Comparing Examples 2 and 9-12, it can be seen that as the catalytic reaction temperature increases, the product yield gradually increases. At excessively high temperatures (200℃), the product purity and yield decrease significantly, and a large number of byproducts appear.

[0046] like Figure 1 The figure shows the gas chromatogram of 1,1-difluoro-2-iodoethylene prepared in Example 2. As can be seen from the figure, the peak of the product 1,1-difluoro-2-iodoethylene is at 8.135 min, the peak of the intermediate product 1,2-diiodo-1,1-difluoroethane is at 11.013 min, the peak of the raw material VDF is at 3.919 min, and the peak of the unknown impurity is at 8.580 min.

Claims

1. A method for preparing 1,1-difluoro-2-iodoethylene, characterized in that, include: (1) Iodine was added to a reaction vessel containing solvent, vinylidene fluoride was introduced, and the reaction was carried out under photocatalytic conditions. After the reaction was completed, the intermediate product 1,2-diiodo-1,1-difluoroethane was collected by alkaline washing and distillation. (2) The intermediate product 1,2-diiodo-1,1-difluoroethane was added to a slurry bed reactor. An inert solvent and an alkali metal catalyst were added to the slurry bed reactor to carry out the reaction. After the reaction was completed, 1,1-difluoro-2-iodoethylene was collected by distillation.

2. The preparation method according to claim 1, characterized in that, The molar ratio of vinylidene fluoride to iodine in step (1) is (0.9~1.5):

1.

3. The preparation method according to claim 1, characterized in that, The solvent mentioned in step (1) is at least one of diethyl ether, tetrahydrofuran, and diethylene oxide.

4. The preparation method according to claim 1, characterized in that, The reaction temperature in step (1) is 40~100℃ and the reaction time is 8~24h.

5. The preparation method according to claim 1, characterized in that, The photocatalysis in step (1) is infrared light irradiation, and the intensity of the infrared light irradiation is 1000~2500mW / cm². 2 .

6. The preparation method according to claim 1, characterized in that, The inert solvent mentioned in step (2) is one of carbon tetrachloride, chloroform, N,N-dimethylformamide, and dimethyl sulfoxide.

7. The preparation method according to claim 1, characterized in that, The alkali metal catalyst mentioned in step (2) is a supported metal SiO2 catalyst.

8. The preparation method according to claim 7, characterized in that, The alkali metal catalyst is one of Mg / SiO2, Fe / SiO2, Ce / SiO2, Zn / SiO2, Co / SiO2 or Ni / SiO2.

9. The preparation method according to claim 1, characterized in that, The mass ratio of the intermediate product, inert solvent, and alkali metal catalyst mentioned in step (2) is 1:(1~20):(0.05~0.3).

10. The preparation method according to claim 1, characterized in that, In step (2), the reaction time is 3-12 hours and the reaction temperature is 50-200℃.

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