A method for preparing a high carbon number diiodoperfluoroalkane

Abstract

The application relates to the technical field of fluorine-containing iodoalkane preparation, in particular to a preparation method of high-carbon-number diiodoperfluoroalkane, which comprises the following steps: reacting tetrafluoroethylene and elemental iodine to generate diiodotetrafluoroethane; and under the action of a catalyst, the diiodotetrafluoroethane is subjected to telomerization reaction with tetrafluoroethylene to generate high-carbon-number diiodoperfluorobutane and diiodoperfluorohexane; and the catalyst is a metal nickel catalyst supported on silicon dioxide. The metal nickel catalyst supported on silicon dioxide is used to make the diiodotetrafluoroethane and the tetrafluoroethylene subjected to telomerization reaction to obtain diiodoperfluoroalkane with higher carbon number. The application has the advantages of simple process, low reaction temperature and the like, and can significantly improve the yield of diiodoperfluorobutane and diiodoperfluorohexane.

Description

Technical Field

[0001] This invention relates to the field of fluorinated iodoalkane technology, and more particularly to a method for preparing high-carbon-number diiodoperfluoroalkanes. Background Technology

[0002] Diiodoperfluoroalkane I (CF2CF2) n I (n = 1, 2, 3) is a very important intermediate used to synthesize various long-chain, branched perfluorinated or polyfluorinated compounds. For example, it can undergo addition reactions with many substances containing both functional groups and double bonds to give diadditions, and then, through the elimination of HI, yield fluorinated compounds, fluorinated diacetylenes, and branched fluorinated diols. These substances can be copolymerized with other compounds to obtain various fluorinated polymers such as fluorinated polyesters, fluorinated epoxy resins, and fluorinated polyacrylates. In the field of fluororubber preparation, I(CF₂CF₂)₂I is used as a chain transfer agent to control the molecular weight and molecular weight distribution of fluororubber.

[0003] ICF₂CF₂I is typically obtained by reacting iodine with tetrafluoroethylene. This reaction does not require a catalyst or initiator, and the iodine yield can reach over 90%. To obtain diiodoperfluoroalkanes with higher carbon numbers, a telomerization reaction of ICF₂CF₂I with tetrafluoroethylene or a deiodination reaction of ICF₂CF₂I by heating is required. The telomerization process is time-consuming and requires the addition of excess tetrafluoroethylene gas. The deiodination reaction by heating requires high temperatures and produces a large amount of elemental iodine, causing equipment blockage. Both methods yield low amounts of I(CF₂CF₂)₂I.

[0004] Patent CN1267391C discloses a method for preparing diiodoperfluoroalkanes. By rationally adjusting the degree of polymerization and deiodination polymerization, it overcomes the tendency of either the conversion rate or selectivity of the simple deiodination polymerization or polymerization to be overly emphasized, so that the conversion rate and selectivity of the reaction are reasonably balanced. As a result, the conversion rate of the raw materials and the selectivity to the target product both reach 75%, the total yield of the process reaches 57%, and the main product is ICF2CF2I.

[0005] Patent CN115677452A discloses a continuous preparation method for diiodoperfluoroalkanes. In this method, tetrafluoroethylene and iodine are preheated and continuously introduced into a reactor under a nitrogen atmosphere. A gas-phase reaction occurs under the action of a catalyst, and the reaction products are collected to obtain diiodoperfluoroalkanes. This method requires preheating elemental iodine into iodine vapor before adding it via a metering pump, increasing operational complexity. Elemental iodine is highly corrosive and easily corrodes and clogs the metering pump. Furthermore, the reaction of elemental iodine with tetrafluoroethylene to produce diiodotetrafluoroethane is violently exothermic, making continuous processing difficult to control, and the selectivity for diiodoperfluorobutane is low. The yield of high-carbon-number diiodoperfluoroalkanes depends on higher temperatures (e.g., above 300°C) or an excess of tetrafluoroethylene, both of which are disadvantageous for practical operation.

[0006] Therefore, it is necessary to provide an improved method for preparing diiodoperfluoroalkanes to solve the above problems. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing high carbon number diiodoperfluoroalkanes, which significantly improves the yield of diiodoperfluorobutane and diiodoperfluorohexane by using a nickel catalyst supported on silica, while reducing the reaction temperature.

[0008] To achieve the above objectives, the present invention provides a method for preparing diiodoperfluoroalkane, comprising the following steps:

[0009] S1. Tetrafluoroethylene and elemental iodine react to produce diiodotetrafluoroethane;

[0010] S2. Diiodotetrafluoroethane is reacted with tetrafluoroethylene in the presence of a catalyst to produce high-carbon-number diiodoperfluorobutane and diiodoperfluorohexane.

[0011] The catalyst is a metallic nickel catalyst supported on silica.

[0012] This invention can obtain high-carbon-number (≥4 carbon atoms) diiodoperfluoroalkanes. Using a nickel catalyst supported on silica, high yields of diiodoperfluorobutane and diiodoperfluorohexane can be obtained at relatively low temperatures. Furthermore, preparing diiodotetrafluoroethane first, followed by telomerization with tetrafluoroethylene, makes the reaction process easier to control, produces fewer byproducts, and reduces raw material waste.

[0013] Furthermore, the reaction temperature of the telomerization reaction is 220–260°C; the reaction pressure is 2.8–3.5 MPa; and the reaction time is 8–12 hours. The present invention operates at a reaction temperature below 260°C and proceeds in steps, making the reaction process easier to control and resulting in higher raw material utilization.

[0014] Furthermore, in step S1, the reaction temperature between the tetrafluoroethylene and elemental iodine is 140–180°C.

[0015] Furthermore, in step S1, the molar ratio of tetrafluoroethylene to elemental iodine is 1.05 to 1.3:1.

[0016] Furthermore, in step S2, the molar ratio of diiodotetrafluoroethane to tetrafluoroethylene is 1:1.5 to 3.

[0017] Furthermore, the preparation method of the nickel catalyst supported on silica includes: dissolving NiCl2 and NH4Cl in deionized water, then adding concentrated ammonia, mixing with the aqueous silica solution, and carrying out a hydrothermal reaction; after the hydrothermal reaction is completed, separating and drying the product, and then calcining it under a N2 / H2 mixed atmosphere to obtain the nickel catalyst supported on silica.

[0018] NiCl2 reacts with NH4Cl and concentrated ammonia to form a nickel complex, which adsorbs onto the surface of silica. Through calcination and reduction, a nickel catalyst supported on silica is obtained. This catalyst has a large specific surface area and high catalytic activity, resulting in high catalytic efficiency. This allows for a reduction in reaction temperature and an increase in the yields of diiodoperfluorobutane and diiodoperfluorohexane.

[0019] Furthermore, the catalyst contains 0.3 to 1 wt% nickel.

[0020] Furthermore, the hydrothermal reaction is carried out at a temperature of 80–150°C for a duration of 8–12 hours.

[0021] Furthermore, the roasting temperature is 500–900°C, and the time is 4–9 hours.

[0022] Furthermore, the volume fraction of H2 in the N2 / H2 mixed atmosphere is 3-8%.

[0023] Furthermore, this includes the following steps:

[0024] S1. Add elemental iodine to the reactor, evacuate the reactor, replace with N2 to control the oxygen content to below 30 ppm, then add tetrafluoroethylene and react at a temperature of 140-180℃ to produce diiodotetrafluoroethane.

[0025] S2. Add diiodotetrafluoroethane and catalyst to the reactor, evacuate and replace with N2 to control the oxygen content to below 30 ppm, then add tetrafluoroethylene to the reactor and carry out a telomerization reaction at 200-260℃ and 2.8-3.5 MPa to produce high carbon number diiodoperfluorobutane and diiodoperfluorohexane.

[0026] This invention can increase the yield of I(CF2CF2)2I to over 40%, and the yield of diiodoperfluorohexane can reach over 20%.

[0027] The beneficial effects of this invention are as follows:

[0028] The method for preparing high-carbon-number diiodoperfluoroalkanes provided by this invention utilizes a nickel catalyst supported on silica to facilitate the telomerization reaction of diiodotetrafluoroethane and tetrafluoroethylene, thereby yielding diiodoperfluoroalkanes with even higher carbon numbers. This significantly improves the yields of diiodoperfluorobutane and diiodoperfluorohexane while simultaneously reducing the reaction temperature. Furthermore, the reaction temperature of this invention is relatively low, the reaction process is easily controlled, and it is suitable for large-scale application. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention are described clearly and completely below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0030] Examples 1-6

[0031] The preparation method of Ni / SiO2 catalyst includes the following steps:

[0032] A certain amount of NiCl2 and NH4Cl were dissolved in deionized water, and concentrated ammonia was slowly added under stirring. A certain amount of SiO2 was added to the deionized water, and after sonication for 10 minutes, it was added to the mixed solution of NiCl2 and NH4Cl. After stirring for another 10 minutes, the mixture was transferred to a hydrothermal reactor lined with polytetrafluoroethylene and reacted at 80–150 °C for 8–12 hours. After the reaction was completed, the mixture was allowed to cool naturally to room temperature, washed, separated, and dried to obtain the catalyst precursor. The precursor was placed in a tube furnace and calcined at 500–900 °C in a 5% H2 / N2 mixed gas for 4–9 hours. After cooling to room temperature, the product was collected, which is the supported metallic Ni catalyst.

[0033] In Example 1, catalyst A was obtained; in Example 2, catalyst B was obtained; in Example 3, catalyst C was obtained; in Example 4, catalyst D was obtained; in Example 5, catalyst E was obtained; and in Example 6, catalyst F was obtained.

[0034] The hydrothermal reaction temperature, hydrothermal reaction time, calcination temperature, calcination time, and Ni loading in each embodiment are shown in Table 1.

[0035] Table 1. Hydrothermal reaction temperature and time, calcination temperature and time, and Ni loading in Examples 1-5.

[0036]

[0037] Examples 7-15

[0038] A method for preparing diiodoperfluoroalkane includes the following steps: adding elemental iodine to a reaction vessel, evacuating the vessel, replacing the oxygen content with N2 to control it below 30 ppm, and then adding tetrafluoroethylene to the reaction vessel and reacting it at 160°C to produce diiodotetrafluoroethane. The molar ratio of elemental iodine to tetrafluoroethylene is 1:1.2.

[0039] Diiodotetrafluoroethane and a catalyst were added to a reactor. The reactor was evacuated and purged with N2 to control the oxygen content below 30 ppm. Tetrafluoroethylene was then added to the reactor, and the reaction was carried out at 200–260 °C to produce high-carbon-number diiodoperfluorobutane and diiodoperfluorohexane. The polymerization temperature, pressure, reaction time, and catalyst type are shown in Table 2. The molar ratio of diiodotetrafluoroethane to tetrafluoroethylene was 1:2.

[0040] Table 2. Telogenization reaction temperature, pressure, time, and catalyst type for each embodiment.

[0041]

[0042]

[0043] Comparative Example 1

[0044] This comparative example relates to a method for preparing diiodoperfluoroalkane, which differs from Example 12 in that no catalyst is added in this comparative example.

[0045] Comparative Example 2

[0046] This comparative example relates to a method for preparing diiodoperfluoroalkane. The difference from Example 12 is that the catalyst was not loaded, that is, SiO2 was not added during the catalyst preparation process.

[0047] The content of diiodotetrafluoroethane in each example and comparative example is shown in Table 3. Wherein, the conversion rate of diiodotetrafluoroethane = the number of moles of diiodotetrafluoroethane reacted / the initial number of moles of diiodotetrafluoroethane;

[0048] Diiodoperfluorobutane yield = number of moles of diiodoperfluorobutane produced / number of moles of initial diiodotetrafluoroethane;

[0049] Diiodoperfluorohexane yield = number of moles of diiodoperfluorobutane produced / number of moles of initial diiodotetrafluoroethane.

[0050] Table 3. Content of diiodoperfluoroalkanes in each example and comparative example.

[0051]

[0052]

[0053] As can be seen from the comparison of Examples 7-15, the reaction temperature, reaction pressure, reaction time, and catalyst all affect the yield of perfluorobutyl diiodide and perfluorohexyl diiodide. Example 12 showed the highest yields of diiodoperfluorobutane and diiodoperfluorohexane, with a conversion rate of 68.5% for diiodotetrafluoroethane. Furthermore, the yields of diiodoperfluorobutane in all examples of this invention are more than twice that of diiodoperfluorohexane, indicating high selectivity for diiodoperfluorobutane.

[0054] In Comparative Example 1, no catalyst was used, and the yields of perfluorobutyl diiodide and perfluorohexyl diiodide were low. In Comparative Example 2, the catalyst was not supported, and the yields of perfluorobutyl diiodide and perfluorohexyl diiodide were also lower than those in Example 12. This indicates that the supported nano-nickel catalyst used in this invention can significantly improve the yield of high-carbon-number perfluoroalkanes in the telomerization reaction of diiodotetrafluoroethane and tetrafluoroethylene.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A process for the preparation of diiodoperfluoroalkanes, characterized in that, Includes the following steps: S1. Tetrafluoroethylene and elemental iodine react to produce diiodotetrafluoroethane; S2. Diiodotetrafluoroethane is reacted with tetrafluoroethylene in the presence of a catalyst to produce diiodoperfluorobutane and diiodoperfluorohexane. The catalyst is a metallic nickel catalyst supported on silica.

2. The method for preparing diiodoperfluoroalkane according to claim 1, characterized in that, The reaction temperature of the telomerization reaction is 220–260°C; the reaction pressure is 2.8–3.5 MPa; and the reaction time is 8–12 hours.

3. The method for preparing diiodoperfluoroalkane according to claim 1, characterized in that, In step S1, the reaction temperature between tetrafluoroethylene and elemental iodine is 140–180°C.

4. The method for preparing diiodoperfluoroalkane according to claim 1, characterized in that, In step S1, the molar ratio of tetrafluoroethylene to elemental iodine is (1.05-1.3):1; And / or, in step S2, the molar ratio of the diiodotetrafluoroethane to the tetrafluoroethylene is 1:(1.5-3).

5. The method for preparing diiodoperfluoroalkane according to claim 1, characterized in that, The preparation method of the nickel catalyst supported on silica includes: dissolving NiCl2 and NH4Cl in deionized water, then adding concentrated ammonia, mixing with the aqueous silica solution, and then carrying out a hydrothermal reaction. After the hydrothermal reaction is completed, the product is separated and dried, and then calcined under a N2 / H2 mixed atmosphere to obtain a nickel catalyst supported on silica.

6. The method for preparing diiodoperfluoroalkane according to claim 5, characterized in that, The catalyst has a nickel loading of 0.3–1 wt%.

7. The method for preparing diiodoperfluoroalkane according to claim 5, characterized in that, The hydrothermal reaction is carried out at a temperature of 80–150°C for 8–12 hours.

8. The method for preparing diiodoperfluoroalkane according to claim 5, characterized in that, The roasting temperature is 500–900℃, and the time is 4–9 hours.

9. The method for preparing diiodoperfluoroalkane according to claim 5, characterized in that, The volume fraction of H2 in the N2 / H2 mixed atmosphere is 3-8%.

10. The method for preparing diiodoperfluoroalkane according to any one of claims 1-9, characterized in that, Includes the following steps: S1. Add elemental iodine to the reactor, evacuate the reactor, replace with N2 to control the oxygen content to below 30 ppm, then add tetrafluoroethylene and react at a temperature of 140-180℃ to produce diiodotetrafluoroethane. S2. Add diiodotetrafluoroethane and catalyst to the reactor, evacuate and replace with N2 to control the oxygen content to below 30 ppm, then add tetrafluoroethylene to the reactor and carry out a telomerization reaction at 200-260℃ and 2.8-3.5 MPa to produce high carbon number diiodoperfluorobutane and diiodoperfluorohexane.

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