A method for preparing 3-pentafluoroethyl-4-trifluoromethyl-dodecylhexane by electrolytic fluorination of hexafluoropropylene trimer

Abstract

This invention discloses a method for preparing 3-pentafluoroethyl-4-trifluoromethyl-dodecylhexane by electrolytic fluorination of hexafluoropropylene trimer, relating to the field of organofluorine chemistry. This method uses anhydrous hydrogen fluoride as both solvent and fluorine source, and performs electrolytic fluorination in a nickel or Monel alloy electrolytic cell. By optimizing the current density, voltage, temperature, and reaction time, the fluorination selectivity is improved, the formation of byproducts is reduced, and the target product is purified by distillation. This method is stable, highly controllable, and suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of organofluorine chemistry, and in particular to a method for preparing 3-pentafluoroethyl-4-trifluoromethyl-dodecylhexane by electrolytic fluorination of hexafluoropropylene trimer. Background Technology

[0002] Perfluorinated compounds (PFCs) have wide applications in fields such as electronic chemistry, aerospace, semiconductor manufacturing, lubricants, pharmaceuticals, and high-end fluorine materials due to their unique chemical stability, high-temperature resistance, low surface energy, and excellent dielectric properties. Among them, perfluoroalkanes are a typical class of perfluorinated compounds, in which all hydrogen atoms in their molecules are replaced by fluorine atoms, exhibiting extremely low reactivity while possessing high volatility and chemical inertness. Therefore, these compounds are commonly used to manufacture corrosion-resistant solvents, coolants, fluorinated lubricants, and special dielectric fluids.

[0003] hexafluoropropylene trimer (C9F) 18 3-Pentafluoroethyl-4-trifluoromethyl-dodecylhexane (C9F6) is an important perfluoroolefin trimer, polymerized from three molecules of hexafluoropropylene (C3F6) under specific catalytic conditions, and mainly composed of three isomers (T-1, T-2, and T-3). Due to its unique structure and chemical stability, this compound has significant applications in the synthesis of fine fluorinated chemicals. In recent years, using hexafluoropropylene trimer as a raw material to prepare more complex perfluoroalkane derivatives through selective fluorination or structural rearrangement has become a research hotspot. For example, the target product 3-pentafluoroethyl-4-trifluoromethyl-dodecylfluorohexane (C9F6) is... 20 ) is a perfluoroalkyl compound with high stability, low surface tension and excellent insulation properties. It can be used in special coolants, fluorinated solvents, high-end electronic chemicals and medical fluorinated carrier materials.

[0004] Electrolytic fluorination is a relatively mature industrial fluorination method. This process uses anhydrous hydrogen fluoride (HF) as the fluorine source, gradually replacing hydrogen in organic molecules with fluorine under electrolytic conditions. Developed from the Simons fluorination process, this method is widely used in the preparation of perfluoroalkanes, perfluorocycloalkanes, and other high-end fluorine fine chemicals. For example, perfluorobutane, perfluorohexane, and perfluorooctane can all be prepared using this method.

[0005] However, electrolytic fluorination also presents the following technical challenges: the selectivity of the target product is difficult to control and is prone to the formation of byproducts; hydrogen fluoride is highly corrosive to equipment during the reaction; and reaction conditions need to be precisely controlled to avoid over-fluorination or degradation of the carbon skeleton. Summary of the Invention

[0006] To address these issues, this invention provides an efficient and controllable electrolytic fluorination process that achieves the directional fluorination of hexafluoropropylene trimer, successfully preparing 3-pentafluoroethyl-4-trifluoromethyl-dodecylhexane. Compared to traditional direct fluorination and high-temperature gas-phase fluorination methods, the electrolytic fluorination process of this invention offers superior selectivity, lower energy consumption, and milder reaction conditions, providing a new technical route for the fine synthesis of perfluoroalkanes and possessing broad prospects for industrial application.

[0007] The specific plan is as follows:

[0008] A method for preparing 3-pentafluoroethyl-4-trifluoromethyl-dodecylhexane by electrolytic fluorination of hexafluoropropylene trimer, characterized by comprising the following steps:

[0009] (1) Preparation of electrolyte: Add 100-500 parts by weight of anhydrous hydrogen fluoride and 0.5-5 parts by weight of conductive salt to the electrolytic cell and stir evenly;

[0010] (2) Adding raw materials: Under stirring conditions, add 50-300 parts by weight of hexafluoropropylene trimer to the electrolytic cell and dissolve it uniformly in HF, then add 2.5-6 parts of catalyst;

[0011] (3) Electrolysis reaction: The electrolysis reaction should be carried out in a closed system, and the current density and voltage should be controlled. Electrolysis should be carried out at -10~5℃ for 5~24 hours.

[0012] (4) Reaction termination and separation: After the reaction is completed, the reaction mixture is distilled to recover HF, and the remaining liquid is washed with water and neutralized; the target product is purified by vacuum distillation to obtain 3-pentafluoroethyl-4-trifluoromethyl-dodecylhexane;

[0013] The catalyst is prepared by fluorination of a catalyst precursor obtained by complexing an activator and ammonia water in a reactor.

[0014] The complexing activator is prepared by reacting allyl polyethylene glycol, (ferrocene) hexamethylene mercaptan, trans-2-butene-1,4-dicarboxylic acid, and dimethylpropene S-thiobisphosphonic acid.

[0015] In one or more embodiments, the conductive salt is selected from one or a combination of potassium fluoride (KF), cesium fluoride (CsF), or potassium tetrafluoroborate (KBF4).

[0016] In one or more embodiments, the moisture content in the closed electrolytic reaction system is not higher than 50 ppm.

[0017] In one or more embodiments, the electrolytic reaction anode is made of at least one of nickel, nickel-copper alloy, and platinum metal, and the cathode is made of graphite, nickel, or stainless steel.

[0018] In one or more embodiments, the electrolysis current density is controlled at 1~5 A / dm², and the voltage is controlled at 4~6V.

[0019] In one or more embodiments, the distillation pressure is controlled at 5-50 kPa, and the number of distillation trays is 10-50.

[0020] In one or more embodiments, the catalyst is prepared by:

[0021] S1. Preparation of mixed solution: By weight, add 29-58 parts of Co(NO3)2, 10-20 parts of Zn(NO3)2, and 4-8 parts of La(NO3)3 to 300-500 parts of water, then add a complexing activator, stir, and dropwise add 20-50 parts of ammonia water (20-30% by weight) into the reactor. React at 50-70℃ for 100-150 minutes. After gel formation, age the product, spray dry it, and then calcine it at 400-600℃ to obtain the catalyst precursor.

[0022] S2. Catalyst preparation: The catalyst precursor obtained in S1 is loaded into a reactor, and a mixture of nitrogen and HF with a volume ratio of 5-10 times is introduced to carry out fluorination. After the gas introduction is completed, the mixture is replaced with nitrogen to obtain the catalyst.

[0023] In one or more embodiments, the method for preparing the complexing agent is as follows:

[0024] By weight, 150-200 parts of allyl polyethylene glycol, 0.03-0.5 parts of (ferrocene) hexamethylene mercaptan, 10-20 parts of trans-2-butene-1,4-dicarboxylic acid, 3-8 parts of dimethylpropene S-thiodiphosphoric acid (CAS: 684271-20-3), and 0.3-3 parts of benzoyl peroxide are stirred at 50-60°C for 120-150 minutes to obtain a complexing activator.

[0025] The catalyst has the following beneficial effects:

[0026] 1. Increase the number and accessibility of catalyst active sites.

[0027] Introducing ferrocene: By incorporating electrochemically active ferrocene groups into the polyethylene glycol chain, the electron transfer capacity of the catalyst is increased. This modification not only improves the conductivity of the catalyst but also enhances its stability, thereby providing more active sites during the catalytic process.

[0028] Increased accessibility of active sites: Through chemical reactions and calcination processes, pure oxides (such as cobalt oxide, zinc oxide, and lanthanum oxide) are left behind. Subsequent fluorination significantly improves the accessibility of active sites on the catalyst surface, making it easier for reactants to contact the active sites and accelerating the reaction rate.

[0029] 2. Optimize the hole structure

[0030] Controlling pore size distribution: The pore structure of oxides, including pore size and distribution, can be precisely controlled. This control helps to achieve higher specific surface area and more suitable porosity, thereby improving the physical adsorption capacity and reaction selectivity of the catalyst.

[0031] Formation of porous structure: The porous structure formed through the above process not only increases the surface area of ​​the catalyst, but also provides more reaction sites, which is conducive to the diffusion and adsorption of reactants, and further improves the catalytic efficiency.

[0032] 3. Improve catalytic performance

[0033] Enhanced catalytic activity: The catalytic activity of the catalyst is significantly improved due to the increased number of active sites and optimized pore structure. This means that under the same reaction conditions, the catalyst can promote the conversion of reactants into products more quickly, increasing the reaction rate and yield. By introducing ferrocene groups into the polyethylene glycol chain and by copolymerizing trans-2-butene-1,4-dicarboxylic acid with dimethylpropylene S-thiodiphosphoric acid to generate polymers containing carboxylic acid and phosphate groups, these steps significantly improve the pore structure control morphology of the catalyst, increase the number and accessibility of active sites, optimize the pore structure, and ultimately enhance catalytic performance.

[0034] Technical effect

[0035] This invention achieves the production of hexafluoropropylene trimer (C9F) by optimizing the electrolytic fluorination process. 18 ) to 3-pentafluoroethyl-4-trifluoromethyl-dodecylfluorohexane (C9F 20 The efficient conversion of ) has the following technical effects:

[0036] 1. Improve the selectivity of the target product and reduce the formation of byproducts;

[0037] 2. Control the fluorination process to improve the purity of the target product;

[0038] 3. Reduce raw material loss and improve reactant utilization. Detailed Implementation

[0039] The present invention will be further described below with reference to specific embodiments, but the invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all alternatives, improvements, and equivalents that may be included within the scope of the claims.

[0040] The testing method involved in this invention is as follows:

[0041] 1) Purity of the target product: The purity of the target product was determined by gas chromatography-mass spectrometry (GC-MS).

[0042] 2) Target product yield: The target product yield is calculated using the following formula: Yield (%) = (Target product mass / Theoretical product mass) * 100% Example

[0043] (1) Preparation of electrolyte

[0044] Add 300 g of anhydrous hydrogen fluoride (HF) and 2 g of potassium fluoride (KF) as a conductive salt to the electrolytic cell, stir well and let it dissolve completely.

[0045] (2) Add raw materials

[0046] Under stirring conditions, hexafluoropropylene trimer (C9F) was added to the electrolytic cell. 18 150 g of the catalyst was stirred and dissolved evenly in HF, and then 2.5 g of the catalyst was added.

[0047] The catalyst is prepared by:

[0048] S1. Preparation of mixed solution: Add 29g Co(NO3)2, 10g Zn(NO3)2, and 4g La(NO3)3 to 300g water, then add complexing activator and stir. Add 20g of ammonia water (20% by mass) dropwise to the reactor and react at 50℃ for 100 minutes. After gel formation, age the product, spray dry it, and then calcine it at 400℃ to obtain the catalyst precursor.

[0049] S2. Catalyst preparation: The catalyst precursor obtained in S1 is loaded into a reactor, and a mixture of nitrogen and HF with a volume ratio of 1:0.2 is introduced to carry out fluorination. After the gas introduction is completed, the mixture is replaced with nitrogen to obtain the fluorinated catalyst.

[0050] The preparation method of the complexing activator is as follows:

[0051] 150g allyl polyethylene glycol, 0.03g (ferrocene) hexamethylene mercaptan, 10g trans-2-butene-1,4-dicarboxylic acid, 3g dimethyl propylene S-thiodiphosphoric acid (CAS: 684271-20-3), and 0.3g benzoyl peroxide were stirred at 50°C for 120 minutes to obtain a complexing activator.

[0052] (3) Electrolysis reaction

[0053] Electrolysis was carried out at a temperature of -5℃, a current density of 2 A / dm², and a voltage of 5 V for 16 hours. The electrolytic cell used a nickel anode and a graphite cathode, and the moisture content in the system was maintained below 30 ppm.

[0054] (4) Reaction termination and separation

[0055] After the electrolysis reaction was completed, HF was recovered by vacuum distillation, and the residual liquid was then washed with water and neutralized. The product was then sent to a distillation column for purification at a pressure of 10 kPa and 30 trays, finally yielding 3-pentafluoroethyl-4-trifluoromethyl-dodecylfluorohexane with a purity of 98.7%.

[0056] Analysis and testing showed that the purity of the target product in this case was 99.33%, and the yield of the target product was 87.50%. Example

[0057] (1) Preparation of electrolyte

[0058] Add 200 g of anhydrous hydrogen fluoride (HF) to the electrolytic cell, and then add 3 g of cesium fluoride (CsF) as a conductive salt, and stir until homogeneous.

[0059] (2) Add raw materials

[0060] Add hexafluoropropylene trimer (C9F) to the electrolytic cell 18 100 g of the catalyst was stirred and dissolved, and then 3.5 g of the catalyst was added.

[0061] The catalyst is prepared by:

[0062] S1. Preparation of mixed solution: Add 34g Co(NO3)2, 13.5g Zn(NO3)2, and 6g La(NO3)3 to 400g water, then add complexing activator and stir. Add 30g of 25% ammonia water dropwise to the reactor and react at 60℃ for 125 minutes. After gel formation, age the product, spray dry it, and then calcine it at 500℃ to obtain the catalyst precursor.

[0063] S2. Catalyst preparation: The catalyst precursor obtained in S1 is loaded into a reactor, and a mixture of nitrogen and HF with a volume ratio of 1:0.3 is introduced to carry out fluorination. After the gas introduction is completed, the mixture is replaced with nitrogen to obtain the catalyst.

[0064] The preparation method of the complexing activator is as follows:

[0065] 165g allyl polyethylene glycol, 0.2g (ferrocene) hexamethylene mercaptan, 15g trans-2-butene-1,4-dicarboxylic acid, 5g dimethyl propylene S-thiodiphosphoric acid (CAS: 684271-20-3), and 1g benzoyl peroxide were stirred at 55°C for 130 minutes to obtain a complexing activator.

[0066] (3) Electrolysis reaction

[0067] At 0℃, the current density was controlled at 3 A / dm², the voltage at 4.5 V, and the electrolysis reaction time at 12 hours. The electrolytic cell used a nickel-copper alloy anode and a nickel cathode, and the moisture content in the system was ≤40 ppm.

[0068] (4) Reaction termination and separation

[0069] After electrolysis, HF was recovered, and the remaining liquid was washed and neutralized with water. The target product was purified by vacuum distillation at a pressure of 20 kPa and 40 trays, finally yielding 3-pentafluoroethyl-4-trifluoromethyl-dodecylfluorohexane with a purity of 98.5%.

[0070] Analysis and testing showed that the purity of the target product in this case was 99.40%, and the yield of the target product was 87.72%. Example

[0071] (1) Preparation of electrolyte

[0072] Add 400 g of anhydrous hydrogen fluoride (HF) and 1 g of potassium tetrafluoroborate (KBF4) as a conductive salt to the electrolytic cell, and stir until homogeneous.

[0073] (2) Add raw materials

[0074] Add hexafluoropropylene trimer (C9F) to the electrolytic cell 18 250 g, after dissolving, add 5 g of catalyst.

[0075] The catalyst is prepared by:

[0076] S1. Preparation of mixed solution: Add 46g Co(NO3)2, 17g Zn(NO3)2, and 6g La(NO3)3 to 400g water, then add complexing activator and stir. Add 40g of 25% ammonia water dropwise to the reactor and react at 60℃ for 125 minutes. After gel formation, age the product, spray dry it, and then calcine it at 500℃ to obtain the catalyst precursor.

[0077] S2. Catalyst preparation: The catalyst precursor obtained in S1 is loaded into a reactor, and a mixture of nitrogen and HF with a volume ratio of 1:0.4 is introduced to carry out fluorination. After the gas introduction is completed, the mixture is replaced with nitrogen to obtain the catalyst.

[0078] The preparation method of the complexing activator is as follows:

[0079] 180g of allyl polyethylene glycol, 0.4g of (ferrocene)hexamethylene mercaptan, 18g of trans-2-butene-1,4-dicarboxylic acid, 7g of dimethylpropene S-thiodiphosphoric acid (CAS: 684271-20-3), and 2g of benzoyl peroxide were stirred at 55°C for 140 minutes to obtain a complexing activator.

[0080] (3) Electrolysis reaction

[0081] At -10℃, the current density was controlled at 1.5 A / dm², the voltage at 4.8 V, and the electrolysis reaction time at 24 hours. The electrolytic cell used a platinum anode and a nickel cathode, and the moisture content in the system did not exceed 50 ppm.

[0082] (4) Reaction termination and separation

[0083] After electrolysis, HF was recovered by distillation, and the residual liquid was then washed and neutralized with water. The target product was then purified by distillation (5 kPa pressure, 50 trays) to obtain 3-pentafluoroethyl-4-trifluoromethyl-dodecylhexane with a purity of 99.0%.

[0084] Analysis and testing showed that the purity of the target product in this case was 99.44%, and the yield of the target product was 87.74%. Example

[0085] (1) Preparation of electrolyte

[0086] Add 250 g of anhydrous hydrogen fluoride (HF) to the electrolytic cell, and add 2 g each of cesium fluoride (CsF) and potassium tetrafluoroborate (KBF4) as conductive salts, and stir until homogeneous.

[0087] (2) Add raw materials

[0088] Add hexafluoropropylene trimer (C9F) to the electrolytic cell18 200 g of the catalyst was stirred evenly and then 6 g of the catalyst was added.

[0089] The catalyst is prepared by:

[0090] S1. Preparation of mixed solution: Add 58g Co(NO3)2, 20g Zn(NO3)2, and 8g La(NO3)3 to 500g water, then add complexing activator and stir. Add 50g of ammonia water (30% by mass) dropwise to the reactor and react at 70℃ for 150 minutes. After gel formation, age the product, spray dry it, and then calcine it at 600℃ to obtain the catalyst precursor.

[0091] S2. Catalyst preparation: The catalyst precursor obtained in S1 is loaded into a reactor, and a mixture of nitrogen and HF with a volume ratio of 1:0.5 is introduced to carry out fluorination. After the gas introduction is completed, the mixture is replaced with nitrogen to obtain the catalyst.

[0092] The preparation method of the complexing activator is as follows:

[0093] 200g allyl polyethylene glycol, 0.5g (ferrocene) hexamethylene mercaptan, 20g trans-2-butene-1,4-dicarboxylic acid, 8g dimethyl propylene S-thiodiphosphoric acid (CAS: 684271-20-3), and 3g benzoyl peroxide were stirred at 60°C for 150 minutes to obtain a complexing activator.

[0094] (3) Electrolysis reaction

[0095] At 5°C, the current density was controlled at 4 A / dm², the voltage at 5.5 V, and the electrolysis reaction time at 8 hours. The electrolytic cell used a nickel anode and a stainless steel cathode, and the moisture content in the system did not exceed 25 ppm.

[0096] (4) Reaction termination and separation

[0097] After electrolysis, HF was recovered by distillation, and the remaining liquid was washed and neutralized with water. The target product was purified by vacuum distillation at a pressure of 30 kPa and 20 trays, finally yielding 3-pentafluoroethyl-4-trifluoromethyl-dodecylfluorohexane with a purity of 98.3%.

[0098] Analysis and testing showed that the purity of the target product in this case was 99.49%, and the yield of the target product was 87.80%.

[0099] Comparative Example 1

[0100] In this example, no complexing activator is added during the catalyst preparation process; otherwise, it is the same as in Example 1.

[0101] Analysis and testing showed that the purity of the target product in this case was 99.05%, and the yield of the target product was 84.85%.

[0102] Comparative Example 2

[0103] In this example, dimethylpropene S-thiodiphosphate is not added during the preparation of the complexing activator, and the rest is the same as in Example 1.

[0104] Analysis and testing showed that the purity of the target product in this case was 99.21%, and the yield of the target product was 86.65%.

[0105] Compared with the comparative example, the present invention shows certain advantages in terms of target product purity and product yield, proving the superiority of the method.

[0106] Although specific embodiments of the invention have been described in detail, variations of these embodiments can be implemented by those skilled in the art. Furthermore, as set forth in the appended claims, such variations can be obtained without departing from the true spirit and scope of the invention.

Claims

1. A method for preparing 3-pentafluoroethyl-4-trifluoromethyl-dodecylhexane by electrolytic fluorination of hexafluoropropylene trimer, characterized in that, Includes the following steps: (1) Preparation of electrolyte: Add 100-500 parts by weight of anhydrous hydrogen fluoride and 0.5-5 parts by weight of conductive salt to the electrolytic cell and stir evenly; (2) Adding raw materials: Under stirring conditions, add 50-300 parts by weight of hexafluoropropylene trimer to the electrolytic cell and dissolve it uniformly in HF, then add 2.5-6 parts of catalyst; (3) Electrolysis reaction: The electrolysis reaction should be carried out in a closed system, and the current density and voltage should be controlled. Electrolysis should be carried out at -10~5℃ for 5~24 hours. (4) Reaction termination and separation: After the reaction is completed, the reaction mixture is distilled to recover HF, and the remaining liquid is washed with water and neutralized; the target product is purified by vacuum distillation to obtain 3-pentafluoroethyl-4-trifluoromethyl-dodecylhexane; The catalyst is prepared by fluorination of a catalyst precursor obtained by complexing an activator and ammonia water in a reactor. The complexing activator is prepared by reacting allyl polyethylene glycol, (ferrocene) hexamethylene mercaptan, trans-2-butene-1,4-dicarboxylic acid, and dimethylpropene S-thiodiphosphoric acid. The catalyst is prepared by: S1. Preparation of mixed solution: By weight, add 29-58 parts of Co(NO3)2, 10-20 parts of Zn(NO3)2, and 4-8 parts of La(NO3)3 to 300-500 parts of water, then add a complexing activator, stir, and dropwise add 20-50 parts of ammonia water (20-30% by weight) into the reactor. React at 50-70℃ for 100-150 minutes. After gel formation, age the product, spray dry it, and then calcine it at 400-600℃ to obtain the catalyst precursor. S2. Catalyst preparation: The catalyst precursor obtained in S1 is loaded into a reactor, and a mixture of nitrogen and HF with a volume ratio of 5-10 times is introduced to carry out fluorination. After the gas introduction is completed, the mixture is replaced with nitrogen to obtain the catalyst. The preparation method of the complexing activator is as follows: By weight, 150-200 parts of allyl polyethylene glycol, 0.03-0.5 parts of (ferrocene) hexamethylene mercaptan, 10-20 parts of trans-2-butene-1,4-dicarboxylic acid, 3-8 parts of dimethylpropene S-thiodiphosphoric acid, and 0.3-3 parts of benzoyl peroxide are stirred at 50-60°C for 120-150 minutes to obtain a complexing activator.

2. The method for preparing 3-pentafluoroethyl-4-trifluoromethyl-dodecylhexane by electrolytic fluorination of hexafluoropropylene trimer according to claim 1, characterized in that: The conductive salt is selected from one or a combination of potassium fluoride (KF), cesium fluoride (CsF), or potassium tetrafluoroborate (KBF4).

3. The method for preparing 3-pentafluoroethyl-4-trifluoromethyl-dodecylhexane by electrolytic fluorination of hexafluoropropylene trimer according to claim 1, characterized in that: The moisture content in the closed electrolytic reaction system is no higher than 50 ppm.

4. The method for preparing 3-pentafluoroethyl-4-trifluoromethyl-dodecylhexane by electrolytic fluorination of hexafluoropropylene trimer according to claim 1, characterized in that: The anode of the electrolytic reaction is made of at least one of nickel, nickel-copper alloy, and platinum, and the cathode is made of graphite, nickel, or stainless steel.

5. The method for preparing 3-pentafluoroethyl-4-trifluoromethyl-dodecylhexane by electrolytic fluorination of hexafluoropropylene trimer according to claim 1, characterized in that: The current density is controlled at 1~5 A / dm², and the voltage is controlled at 4~6 V.

6. The method for preparing 3-pentafluoroethyl-4-trifluoromethyl-dodecylhexane by electrolytic fluorination of hexafluoropropylene trimer according to claim 1, characterized in that: The distillation pressure is controlled at 5-50 kPa, and the number of distillation trays is 10-50.