A method for preparing hexafluoropropylene trimerization with enhanced catalysis

Abstract

This invention discloses a method for preparing hexafluoropropylene trimerization using enhanced catalysis, relating to the fields of fluorinated organic compound synthesis and liquid coolant technology. The method involves passing HFP into an aprotic solvent containing Lewis acid under an inert atmosphere, polymerizing it under specified conditions, terminating the reaction with a proton source, and finally separating the dimer and trimer through anaerobic fractionation. Subsequent steps include washing, neutralization, and drying to remove catalyst residue, recover the solvent, and regenerate and recycle the Lewis acid. This method achieves highly selective, low-impurity, and high-purity products. The obtained trimer can be used in high-insulation, high-stability electronic liquid coolants, and the process is economical, with the catalyst reusable.

Description

Technical Field

[0001] This invention relates to the field of fluorinated organic compound synthesis and liquid coolant technology, and in particular to a method for preparing hexafluoropropylene trimerization by enhancing catalysis. Background Technology

[0002] Hexafluoropropylene (HFP) is an important perfluoroolefin monomer with wide applications in fluorination chemistry. HFP can be converted into various functional liquids or intermediates through dimerization, trimerization, and higher forms. These oligomers have important uses in electronic coolants, insulating fluids, fluorinated surfactants, and fluoropolymer precursors.

[0003] However, existing HFP oligomerization techniques still have significant limitations: Catalytic system and selectivity issues: Traditional HFP oligomerization often employs alkali metal fluorides to support gas-phase reactions on solid supports. A typical patent, such as Daikin's early process, involves passing HFP gas through activated carbon or NiO catalysts supported on alkali metal fluorides at 200°C to generate oligomers with high conversion rates.

[0004] Although this method can achieve high conversion rates, it suffers from problems such as high temperatures, long contact times, poor catalyst selectivity, and difficulties in controlling byproducts. Furthermore, this solid-phase catalytic system makes it difficult to flexibly control the oligomer ratio on an industrial scale.

[0005] Limitations of liquid-phase polymerization processes: To enhance selectivity, some literature and patents have explored HFP oligomerization in the liquid phase. For example, US Patent 4042638A describes the use of halides and crown ethers to catalyze HFP polymerization in organic solvents, achieving highly selective dimerization at near room temperature.

[0006] While this method achieves good selectivity, it fixes the product to dimer, and catalyst recovery and residue removal are potential problems. Furthermore, the formation of trimers or higher polymers is suppressed, which is detrimental to the production of high-purity trimers.

[0007] Harmful isomers and purification challenges: HFP dimer (C6F) 12 HFP typically exists in multiple isomers (cis / trans-4-methyl-2-pentene and the thermodynamic isomer 2-methyl-2-pentene), some of which are toxic to humans and the environment. For example, European patent EP1,877,356 (corresponding to US7053253B1) proposes a method for treating HFP dimer mixtures (containing undesirable isomers) with alkali (alkaline aqueous solution), which can effectively remove thermodynamic isomers to extremely low ppm levels.

[0008] However, this removal process relies on water washing, stratification, possible organic-aqueous phase extraction, and neutralization, making the process complex and posing challenges to improving product recovery and purity.

[0009] In summary, existing technologies still have the following key problems in HFP aggregation (especially trimerization): It is difficult to precisely control the ratio of dimer to trimer (insufficient selectivity); Catalytic systems (such as solid fluorides or halides + crown ethers) are difficult to recover / reuse; Purification of catalyst residues (especially harmful ions or metals) is difficult; Removal of harmful isomers (such as thermodynamic isomers) from the final products (dimer, trimer) requires additional complex processing. There is still considerable room for improvement in the industrialization, economic efficiency, and safety of existing trimer production methods. Summary of the Invention

[0010] Based on the problems raised in the background art above, the present invention proposes a method for preparing hexafluoropropylene trimerization with enhanced catalysis.

[0011] The technical solution is as follows: A method for preparing hexafluoropropylene trimerization with enhanced catalysis includes the following steps: Raw material preparation: Aluminum trichloride: 1–5 parts by weight; Aprotic solvent: 100–200 parts by weight; Hexafluoropropylene monomer: 20–30 parts by weight; Terminator: 0.1-0.5 parts by weight; Bonded supported carboxylic acid purification agent: 10-20 parts by weight; The steps include: (a) In a N2 atmosphere, aluminum trichloride is mixed with an aprotic solvent and stirred to ensure that the synergist is fully dissolved; (b) Add HFP monomer to the above system through a throttle valve to form an active system with HFP and synergist; (c) Control the reaction temperature in the range of 35°C to 45°C, the stirring speed in the range of 250–500 rpm, and the reaction time in the range of 8–12 hours; (d) Terminate the reaction with a terminator, then add a bonded supported carboxylic acid purification agent, stir for 30-60 minutes, and filter. (e) The filtered mixture is transferred to a distillation / fractionation apparatus under an inert atmosphere, and the fractions are separated by vacuum fractionation to collect the crude dimer and trimer. (f) The collected dimers and trimers are mixed with water at an organic phase:water mass ratio of 1:0.1–1:5 and stirred vigorously to extract residual synergists; the organic layer is collected after separation; an alkaline solution of 0.5–2 parts by mass is added to the organic layer and gently stirred to neutralize; the organic layer is separated again after separation; the organic layer is dried using a desiccant and then filtered; the solvent is evaporated to recover the purified HFP dimers and trimers.

[0012] Optionally, the preparation method of the bonded supported carboxylic acid purifying agent is as follows: Step 1: Preparation of functionalized precursor: According to the mass ratio, add 100-140 parts of pretreated support, 1500-1800 parts of ethanol, and 4-7 parts of silane coupling agent KH570 to the reactor. After deoxygenating with nitrogen for 20-30 minutes, reflux at 110-120℃ for 8-12 hours. Filter, wash, and dry to obtain double bond modified support; separately take 10-20 parts of 2-mercaptothiophene, 15-35 parts of 2,3-dimercaptosuccinic acid, and 200-300 parts of anhydrous dichloromethane and stir at room temperature for 2-4 hours to obtain thiolized synergistic complex. Step 2: Addition reaction loading and purification: Add the above double bond modified support to the mercapto-enhanced complex, deoxygenate under nitrogen for 10-20 minutes, add 1-3 parts of photoinitiator Darocur 1173, and react at room temperature for 4-6 hours under 365nm ultraviolet light irradiation; after the reaction, wash 4-6 times with anhydrous dichloromethane, filter, and vacuum dry at 100-120℃ for 8-10 hours to obtain the bonded supported carboxylic acid purified agent.

[0013] Optionally, the pretreatment carrier is selected from ZSM-5 molecular sieve or MCM-41 mesoporous silica material, and the pretreatment step is calcination at 500-600℃ for 4-6 hours.

[0014] Optionally, the aprotic solvent is selected from dichloromethane, perfluorobutyltetrahydrofuran, or perfluoroalkane.

[0015] Optionally, the terminating agent is selected from deionized water or 0.1–1M HCl solution.

[0016] Optionally, the inert atmosphere is N2 or Ar.

[0017] Optionally, the depressurization pressure in the reduced pressure fractionation is 10–200 Torr.

[0018] Optionally, the alkaline solution is selected from 0.01–1M NaHCO3 or Na2CO3.

[0019] Optionally, the desiccant is selected from anhydrous MgSO4 or 3Å–5Å molecular sieves, and the amount of desiccant used is 0.1–2 times the mass of the organic layer.

[0020] Reaction mechanism: In anhydrous, aprotic inert systems, aluminum trichloride acts as a Lewis acid, coordinating with the double bond of hexafluoropropylene to form a carbocation active intermediate, initiating intermolecular nucleophilic addition to achieve oligomerization. This stabilizes the active sites, inhibits deactivation, and enhances the trimerization pathway by regulating the regioselectivity of the addition reaction through steric hindrance and electronic effects. The bonded, immobilized carboxylic acid purification agent is covalently bonded to the support surface via a mercapto-olefin photoaddition reaction. Its carboxyl and mercapto active sites can specifically complex residual aluminum ions and catalytic components. Simultaneously, the weakly acidic sites on the surface stabilize the configuration of the target oligomer, inhibiting the formation and accumulation of harmful isomers, thus achieving a synergistic catalytic-purification mechanism.

[0021] Technical effects: Compared with the prior art, the present invention has the following advantages: Aluminum trichloride was used to achieve highly selective oligomerization of hexafluoropropylene under mild conditions, which significantly improved the trimer formation ratio and simplified the reaction process and equipment requirements.

[0022] The bonded supported carboxylic acid purifier constructed through the addition reaction of mercapto-olefins can efficiently remove residual catalysts and metal impurities from the reaction system, reduce the difficulty of subsequent purification, and improve product purity and yield.

[0023] By combining vacuum fractionation, water washing and neutralization with drying and refining, the content of harmful isomers can be effectively controlled, and the stability and applicability of dimer and trimer products can be improved. Attached Figure Description

[0024] Figure 1 The infrared spectrum prepared in Example 4. Detailed Implementation

[0025] The features of the present invention are further illustrated below through embodiments, but the scope of protection of this patent is not limited to the embodiments.

[0026] Example 1 1. Raw material preparation (unit: kg) Aluminum trichloride: 1kg Aprotic solvent: 100 kg (selected from dichloromethane) Hexafluoropropylene monomer (HFP): 20kg Terminator: 0.1 kg (selected from deionized water) Bonded supported carboxylic acid purification agent: 10kg 2. Preparation of bonded supported carboxylic acid purification agent Step 1: Preparation of functionalized precursors According to the mass fractions, 100 kg of pretreated support (selected from ZSM-5 molecular sieve, the pretreatment step is calcination at 500℃ for 4 hours), 1500 kg of ethanol, and 4 kg of silane coupling agent KH570 were added to the reactor. After deoxygenation under nitrogen for 20 minutes, the reaction was refluxed at 110℃ for 8 hours. The mixture was filtered, washed, and dried to obtain the double bond modified support. Separately, 10 kg of 2-mercaptothiophene, 15 kg of 2,3-dimercaptosuccinic acid, and 200 kg of anhydrous dichloromethane were stirred at room temperature for 2 hours to prepare the thiolized synergistic complex.

[0027] Step 2: Addition reaction loading and purification The above-mentioned double bond modified support was added to the mercapto-enhanced complex, and the mixture was deoxygenated under nitrogen for 10 minutes. Then, 1 kg of photoinitiator Darocur 1173 was added, and the mixture was reacted at room temperature for 4 hours under 365 nm ultraviolet light irradiation. After the reaction, the mixture was washed 4 times with anhydrous dichloromethane, filtered, and vacuum dried at 100 °C for 8 hours to obtain the bonded supported carboxylic acid purification agent.

[0028] 3. Preparation steps of hexafluoropropylene trimer (a) Mix 1 kg of aluminum trichloride with 100 kg of dichloromethane in a N2 atmosphere and stir to ensure that the synergist is fully dissolved; (b) Add 20 kg of HFP monomer to the above system through a throttling device to form an active system with HFP and synergist; (c) Control the reaction temperature at 35°C and the stirring speed at 250 rpm; the reaction time is 8 hours. (d) Terminate the reaction with 0.1 kg of deionized water, then add 10 kg of bonded supported carboxylic acid purification agent, stir for 30 minutes, and filter. (e) The filtered mixture is transferred to a distillation / fractionation apparatus under N2 atmosphere, and the fractions are separated by vacuum fractionation (reduced pressure of 10 Torr) to collect the crude dimer and trimer. (f) The collected dimers and trimers were mixed with water at a mass ratio of 1:0.1 (organic phase: water) and stirred vigorously to extract residual synergists; the organic layer was collected after separation; 0.5 kg of alkaline solution (selected from 0.01 M NaHCO3) was added to the organic layer and gently stirred to neutralize; the organic layer was separated again after separation; the organic layer was dried using a desiccant (selected from anhydrous MgSO4, in an amount 0.1 times the mass of the organic layer) and then filtered; the solvent was evaporated to recover the purified HFP dimers and trimers.

[0029] Example 2 1. Raw material preparation (unit: kg) Aluminum trichloride: 2.5 kg Aprotic solvent: 130 kg (selected from perfluorobutyltetrahydrofuran) Hexafluoropropylene monomer (HFP): 23kg Terminator: 0.25 kg (selected from 0.3 M HCl solution) Bonded supported carboxylic acid purification agent: 13kg 2. Preparation of bonded supported carboxylic acid purification agent Step 1: Preparation of functionalized precursors According to the mass fractions, 115 kg of pretreated support (selected from MCM-41 mesoporous silica material, the pretreatment step is calcination at 530℃ for 4.5 hours), 1600 kg of ethanol, and 5 kg of silane coupling agent KH570 were added to the reactor. After deoxygenation under nitrogen for 23 minutes, the reaction was refluxed at 113℃ for 9 hours. The mixture was filtered, washed, and dried to obtain the double bond modified support. Separately, 13 kg of 2-mercaptothiophene, 22 kg of 2,3-dimercaptosuccinic acid, and 230 kg of anhydrous dichloromethane were stirred at room temperature for 2.5 hours to prepare the thiol-enhanced complex.

[0030] Step 2: Addition reaction loading and purification The above-mentioned double bond modified support was added to the mercapto-enhanced complex, and the mixture was deoxygenated under nitrogen for 13 minutes. Then, 1.5 kg of photoinitiator Darocur 1173 was added, and the mixture was reacted at room temperature for 4.5 hours under 365 nm ultraviolet light irradiation. After the reaction, the mixture was washed 5 times with anhydrous dichloromethane, filtered, and vacuum dried at 105 °C for 8.5 hours to obtain the bonded supported carboxylic acid purification agent.

[0031] 3. Preparation steps of hexafluoropropylene trimer (a) Mix 2.5 kg of aluminum trichloride with 130 kg of perfluorobutyltetrahydrofuran in a N2 atmosphere and stir to fully dissolve the synergist; (b) Add 23 kg of HFP monomer to the above system through a throttling device to form an active system with HFP and synergist; (c) Control the reaction temperature at 38°C and the stirring rate at 320 rpm; the reaction time is 9 hours. (d) The reaction was terminated with 0.25 kg of 0.3 M HCl solution, and then 13 kg of bonded supported carboxylic acid purification agent was added. The mixture was stirred for 40 minutes and then filtered. (e) The filtered mixture is transferred to a distillation / fractionation apparatus under an Ar atmosphere, and the fractions are separated by vacuum fractionation (reduced pressure of 60 Torr) to collect the crude dimer and trimer. (f) The collected dimers and trimers were mixed with water at a mass ratio of 1:1.5 (organic phase: water) and stirred vigorously to extract residual synergists; the organic layer was collected after separation; 1 kg of alkaline solution (selected from 0.3 M Na2CO3) was added to the organic layer and gently stirred to neutralize; the organic layer was separated again; the organic layer was dried using a desiccant (selected from 3 Å molecular sieve, in an amount 0.8 times the mass of the organic layer) and then filtered; the solvent was evaporated to recover the purified HFP dimers and trimers.

[0032] Example 3 1. Raw material preparation (unit: kg) Aluminum trichloride: 4kg Aprotic solvent: 170 kg (selected from perfluoroalkane) Hexafluoropropylene monomer (HFP): 27kg Terminating agent: 0.4 kg (selected from 0.7 M HCl solution) Bonded supported carboxylic acid purification agent: 17kg 2. Preparation of bonded supported carboxylic acid purification agent Step 1: Preparation of functionalized precursors According to the mass fractions, 130 kg of pretreated support (selected from ZSM-5 molecular sieve, the pretreatment step is calcination at 570℃ for 5.5 hours), 1700 kg of ethanol, and 6 kg of silane coupling agent KH570 were added to the reactor. After deoxygenation under nitrogen for 27 minutes, the reaction was refluxed at 117℃ for 11 hours. The mixture was filtered, washed, and dried to obtain the double bond modified support. Separately, 17 kg of 2-mercaptothiophene, 30 kg of 2,3-dimercaptosuccinic acid, and 270 kg of anhydrous dichloromethane were stirred at room temperature for 3.5 hours to prepare the thiol-enhanced complex.

[0033] Step 2: Addition reaction loading and purification The above-mentioned double bond modified support was added to the mercapto-enhanced complex, and the mixture was deoxygenated under nitrogen for 17 minutes. Then, 2.5 kg of photoinitiator Darocur 1173 was added, and the mixture was reacted at room temperature for 5.5 hours under 365 nm ultraviolet light irradiation. After the reaction, the mixture was washed 5 times with anhydrous dichloromethane, filtered, and vacuum dried at 115 °C for 9.5 hours to obtain the bonded supported carboxylic acid purification agent.

[0034] 3. Preparation steps of hexafluoropropylene trimer (a) Mix 4 kg of aluminum trichloride with 170 kg of perfluoroalkane in a N2 atmosphere and stir to ensure that the synergist is fully dissolved; (b) Add 27 kg of HFP monomer to the above system through a throttling device to form an active system with HFP and synergist; (c) The reaction temperature was controlled at 42°C and the stirring rate at 430 rpm; the reaction time was 11 hours. (d) The reaction was terminated with 0.4 kg of 0.7 M HCl solution, and then 17 kg of bonded supported carboxylic acid purification agent was added. The mixture was stirred for 50 minutes and then filtered. (e) The filtered mixture is transferred to a distillation / fractionation apparatus under N2 atmosphere, and the fractions are separated by vacuum fractionation (reduced pressure of 150 Torr) to collect the coarse dimer and trimer. (f) The collected dimers and trimers were mixed with water at a mass ratio of 1:3.5 (organic phase: water) and stirred vigorously to extract residual synergists; the organic layer was collected after separation; 1.5 kg of alkaline solution (selected from 0.7 M NaHCO3) was added to the organic layer and gently stirred to neutralize; the organic layer was separated again; the organic layer was dried using a desiccant (selected from 5 Å molecular sieve, in an amount 1.5 times the mass of the organic layer) and then filtered; the solvent was evaporated to recover the purified HFP dimers and trimers.

[0035] Example 4 1. Raw material preparation (unit: kg) Aluminum trichloride: 5kg Aprotic solvent: 200 kg (selected from dichloromethane) Hexafluoropropylene monomer (HFP): 30kg Terminator: 0.5 kg (selected from 1M HCl solution) Bonded supported carboxylic acid purification agent: 20kg 2. Preparation of bonded supported carboxylic acid purification agent Step 1: Preparation of functionalized precursors According to the mass fractions, 140 kg of pretreated support (selected from MCM-41 mesoporous silica material, the pretreatment step is calcination at 600℃ for 6 hours), 1800 kg of ethanol, and 7 kg of silane coupling agent KH570 were added to the reactor. After deoxygenation under nitrogen for 30 minutes, the reaction was refluxed at 120℃ for 12 hours. The mixture was filtered, washed, and dried to obtain the double bond modified support. Separately, 20 kg of 2-mercaptothiophene, 35 kg of 2,3-dimercaptosuccinic acid, and 300 kg of anhydrous dichloromethane were stirred at room temperature for 4 hours to prepare the thiol-enhanced complex.

[0036] Step 2: Addition reaction loading and purification The above-mentioned double bond modified carrier was added to the mercapto-enhanced complex, and the mixture was deoxygenated under nitrogen for 20 minutes. Then, 3 kg of photoinitiator Darocur 1173 was added, and the mixture was reacted at room temperature for 6 hours under 365 nm ultraviolet light irradiation. After the reaction, the mixture was washed 6 times with anhydrous dichloromethane, filtered, and vacuum dried at 120 °C for 10 hours to obtain the bonded supported carboxylic acid purification agent.

[0037] 3. Preparation steps of hexafluoropropylene trimer (a) Mix 5 kg of aluminum trichloride with 200 kg of dichloromethane in a N2 atmosphere and stir to ensure that the synergist is fully dissolved; (b) Add 30 kg of HFP monomer to the above system through a throttling device to form an active system with HFP and synergist; (c) Control the reaction temperature at 45°C and the stirring speed at 500 rpm; the reaction time is 12 hours; (d) Terminate the reaction with 0.5 kg of 1 M HCl solution, then add 20 kg of bonded supported carboxylic acid purification agent, stir for 60 minutes, and filter. (e) The filtered mixture is transferred to a distillation / fractionation apparatus under an Ar atmosphere, and the fractions are separated by vacuum fractionation (reduced pressure of 200 Torr) to collect the crude dimer and trimer. (f) The collected dimers and trimers were mixed with water at a mass ratio of 1:5 (organic phase: water) and stirred vigorously to extract residual synergists; the organic layer was collected after separation; 2 kg of alkaline solution (selected from 1 M Na2CO3) was added to the organic layer and gently stirred to neutralize; the organic layer was separated again after separation; the organic layer was dried using a desiccant (selected from anhydrous MgSO4, in an amount twice the mass of the organic layer) and then filtered; the solvent was evaporated to recover the purified HFP dimers and trimers.

[0038] Comparative Example 1 1. Raw material preparation (unit: kg) Aluminum trichloride: 1kg Aprotic solvent: 100 kg (selected from dichloromethane) Hexafluoropropylene monomer (HFP): 20kg Terminator: 0.1 kg (selected from deionized water) 2. Preparation steps of hexafluoropropylene trimer (a) Mix 1 kg of aluminum trichloride with 100 kg of dichloromethane in a N2 atmosphere and stir to ensure that the synergist is fully dissolved; (b) Add 20 kg of HFP monomer to the above system through a throttling device to form an active system with HFP and synergist; (c) Control the reaction temperature at 35°C and the stirring speed at 250 rpm; the reaction time is 8 hours. (d) Terminate the reaction with 0.1 kg of deionized water, stir for 30 minutes, and filter. (e) The filtered mixture is transferred to a distillation / fractionation apparatus under N2 atmosphere, and the fractions are separated by vacuum fractionation (reduced pressure of 10 Torr) to collect the crude dimer and trimer. (f) The collected dimers and trimers were mixed with water at a mass ratio of 1:0.1 (organic phase: water) and stirred vigorously to extract residual synergists; the organic layer was collected after separation; 0.5 kg of alkaline solution (selected from 0.01 M NaHCO3) was added to the organic layer and gently stirred to neutralize; the organic layer was separated again after separation; the organic layer was dried using a desiccant (selected from anhydrous MgSO4, in an amount 0.1 times the mass of the organic layer) and then filtered; the solvent was evaporated to recover the purified HFP dimers and trimers.

[0039] Comparative Example 2 1. Raw material preparation (unit: kg) Aluminum trichloride: 1kg Aprotic solvent: 100 kg (selected from dichloromethane) Hexafluoropropylene monomer (HFP): 20kg Terminator: 0.1 kg (selected from deionized water) Bonded supported carboxylic acid purification agent: 10kg 2. Preparation of bonded supported carboxylic acid purification agent Step 1: Preparation of functionalized precursors According to the mass fractions, 100 kg of pretreated support (selected from ZSM-5 molecular sieve, the pretreatment step is calcination at 500℃ for 4 hours), 1500 kg of ethanol, and 4 kg of silane coupling agent KH570 were added to the reactor. After deoxygenation under nitrogen for 20 minutes, the reaction was refluxed at 110℃ for 8 hours. The double bond modified support was obtained by filtration, washing, and drying. Separately, 10 kg of 2-mercaptothiophene and 200 kg of anhydrous dichloromethane were stirred at room temperature for 2 hours to prepare the thiolized synergistic complex.

[0040] Step 2: Addition reaction loading and purification The above-mentioned double bond modified support was added to the mercapto-enhanced complex, and the mixture was deoxygenated under nitrogen for 10 minutes. Then, 1 kg of photoinitiator Darocur 1173 was added, and the mixture was reacted at room temperature for 4 hours under 365 nm ultraviolet light irradiation. After the reaction, the mixture was washed 4 times with anhydrous dichloromethane, filtered, and vacuum dried at 100 °C for 8 hours to obtain the bonded supported carboxylic acid purification agent.

[0041] 3. Preparation steps of hexafluoropropylene trimer (a) Mix 1 kg of aluminum trichloride with 100 kg of dichloromethane in a N2 atmosphere and stir to ensure that the synergist is fully dissolved; (b) Add 20 kg of HFP monomer to the above system through a throttling device to form an active system with HFP and synergist; (c) Control the reaction temperature at 35°C and the stirring speed at 250 rpm; the reaction time is 8 hours. (d) Terminate the reaction with 0.1 kg of deionized water, then add 10 kg of bonded supported carboxylic acid purification agent, stir for 30 minutes, and filter. (e) The filtered mixture is transferred to a distillation / fractionation apparatus under N2 atmosphere, and the fractions are separated by vacuum fractionation (reduced pressure of 10 Torr) to collect the crude dimer and trimer. (f) The collected dimers and trimers were mixed with water at a mass ratio of 1:0.1 (organic phase: water) and stirred vigorously to extract residual synergists; the organic layer was collected after separation; 0.5 kg of alkaline solution (selected from 0.01 M NaHCO3) was added to the organic layer and gently stirred to neutralize; the organic layer was separated again after separation; the organic layer was dried using a desiccant (selected from anhydrous MgSO4, in an amount 0.1 times the mass of the organic layer) and then filtered; the solvent was evaporated to recover the purified HFP dimers and trimers.

[0042] Comparative Example 3 1. Raw material preparation (unit: kg) Aluminum trichloride: 1kg Aprotic solvent: 100 kg (selected from dichloromethane) Hexafluoropropylene monomer (HFP): 20kg Terminator: 0.1 kg (selected from deionized water) Bonded supported carboxylic acid purification agent: 10kg 2. Preparation of bonded supported carboxylic acid purification agent Step 1: Preparation of functionalized precursors According to the mass fractions, 100 kg of pretreated support (selected from ZSM-5 molecular sieve, the pretreatment step is calcination at 500℃ for 4 hours), 1500 kg of ethanol, and 4 kg of silane coupling agent KH570 were added to the reactor. After deoxygenation under nitrogen for 20 minutes, the reaction was refluxed at 110℃ for 8 hours. The mixture was filtered, washed, and dried to obtain the double bond modified support. Separately, 15 kg of 2,3-dimercaptosuccinic acid and 200 kg of anhydrous dichloromethane were stirred at room temperature for 2 hours to prepare the thiolized synergistic complex.

[0043] Step 2: Addition reaction loading and purification The above-mentioned double bond modified support was added to the mercapto-enhanced complex, and the mixture was deoxygenated under nitrogen for 10 minutes. Then, 1 kg of photoinitiator Darocur 1173 was added, and the mixture was reacted at room temperature for 4 hours under 365 nm ultraviolet light irradiation. After the reaction, the mixture was washed 4 times with anhydrous dichloromethane, filtered, and vacuum dried at 100 °C for 8 hours to obtain the bonded supported carboxylic acid purification agent.

[0044] 3. Preparation steps of hexafluoropropylene trimer (a) Mix 1 kg of aluminum trichloride with 100 kg of dichloromethane in a N2 atmosphere and stir to ensure that the synergist is fully dissolved; (b) Add 20 kg of HFP monomer to the above system through a throttling device to form an active system with HFP and synergist; (c) Control the reaction temperature at 35°C and the stirring speed at 250 rpm; the reaction time is 8 hours. (d) Terminate the reaction with 0.1 kg of deionized water, then add 10 kg of bonded supported carboxylic acid purification agent, stir for 30 minutes, and filter. (e) The filtered mixture is transferred to a distillation / fractionation apparatus under N2 atmosphere, and the fractions are separated by vacuum fractionation (reduced pressure of 10 Torr) to collect the crude dimer and trimer. (f) The collected dimers and trimers were mixed with water at a mass ratio of 1:0.1 (organic phase: water) and stirred vigorously to extract residual synergists; the organic layer was collected after separation; 0.5 kg of alkaline solution (selected from 0.01 M NaHCO3) was added to the organic layer and gently stirred to neutralize; the organic layer was separated again after separation; the organic layer was dried using a desiccant (selected from anhydrous MgSO4, in an amount 0.1 times the mass of the organic layer) and then filtered; the solvent was evaporated to recover the purified HFP dimers and trimers.

[0045] Test method: 1. Chemical composition & purity analysis The composition of each fraction (unreacted HFP, dimer, trimer) was analyzed using gas chromatography (GC) or GC-MS. The fractions were diluted and injected into the GC.

[0046] Calibration: Use pure standards (HFPD (dimer) and HFPT (trimer) standards of known purity) to create a calibration curve to determine the concentration of each component.

[0047] The component content (GC peak area percentage) of the product is calculated using the normalization method.

[0048] 2. Determination of residual Lewis acid (catalyst) The metal content in the product is detected by inductively coupled plasma mass spectrometry (ICP-MS) or inductively coupled plasma atomic emission spectrometry (ICP-OES).

[0049] Sample pretreatment: The purified trimer organic layer is diluted in a suitable solvent (dichloromethane). If necessary, the metal ions are introduced into the aqueous phase by acid washing (dilute acid) before measurement.

[0050] The residual amount (ppm level) was obtained by measuring the sample and comparing it with the blank (without catalyst).

[0051] 3. Electrical insulation properties (for coolant applications) Measure the breakdown voltage: Gradually increase the voltage at a specified electrode distance and rate, and record the breakdown point.

[0052] Volume resistivity: Tested according to GB / T5654.

[0053] Test results: Table 1

[0054] Overall, the test data show that various additives used in the preparation of supported Lewis acid catalysts played a key role in improving the core performance of the product: silane coupling agent KH570 modified the double bonds of the support, providing stable chemical bonding sites for the support of Lewis acid active centers, ensuring the uniform distribution of catalytic active centers on the support surface and preventing loss, thus effectively reducing the residual amount of Lewis acid in the product; 2,3-dimercaptosuccinic acid, as a complexing agent, modified Lewis acid, which could precisely control its catalytic activity, optimize the selectivity for HFP trimerization, and thus significantly improve the purity of the trimer product; photoinitiator Darocur1173 could efficiently initiate addition reactions, ensuring that Lewis acid was stably loaded on the support surface, reducing the loss of catalytic active centers, and ultimately significantly improving the breakdown voltage, reducing the conductivity, and maintaining the thermal stability within a stable range. The overall performance was better than the control sample, fully demonstrating the synergistic effect of each additive in the construction of the catalytic system and the optimization of product performance.

[0055] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. Other modifications can be easily made by those skilled in the art. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A method for preparing hexafluoropropylene trimerization with enhanced catalysis, characterized in that, Includes the following steps: Raw material preparation: Aluminum trichloride: 1-5 parts by weight; Aprotic solvent: 100-200 parts by weight; Hexafluoropropylene monomer: 20-30 parts by weight; Terminator: 0.1-0.5 parts by weight; Bonded supported carboxylic acid purification agent: 10-20 parts by weight; The steps include: (a) In a N2 atmosphere, aluminum trichloride is mixed with an aprotic solvent and stirred to ensure that the synergist is fully dissolved; (b) Add HFP monomer to the above system through a throttle valve to form an active system with HFP and synergist; (c) Control the reaction temperature within the range of 35°C to 45°C, the stirring speed within the range of 250-500 rpm, and the reaction time within the range of 8-12 hours; (d) Terminate the reaction with a terminator, then add a bonded supported carboxylic acid purification agent, stir for 30-60 minutes, and filter. (e) The filtered mixture is transferred to a distillation / fractionation apparatus under an inert atmosphere, and the fractions are separated by vacuum fractionation to collect the crude dimer and trimer. (f) The collected dimers and trimers were mixed with water at an organic phase:water mass ratio of 1:0.1-1:5 and stirred vigorously to extract residual synergists; the organic layer was collected after separation; 0.5-2 parts by mass of alkaline solution were added to the organic layer and gently stirred to neutralize; the organic layer was separated again after separation; the organic layer was dried using a desiccant and then filtered; the solvent was evaporated to recover the purified HFP dimers and trimers; The bonded immobilized carboxylic acid purification agent is prepared by reacting a pretreated carrier, silane coupling agent KH570, 2-mercaptothiophene, 2,3-dimercaptosuccinic acid, and photoinitiator Darocur1173 under ultraviolet light irradiation.

2. The method for preparing hexafluoropropylene trimerization by enhanced catalysis according to claim 1, characterized in that: Preparation method of the bonded supported carboxylic acid purification agent: Step 1: Preparation of functionalized precursor: According to the mass ratio, add 100-140 parts of pretreated support, 1500-1800 parts of ethanol, and 4-7 parts of silane coupling agent KH570 to the reactor. After deoxygenating with nitrogen for 20-30 minutes, reflux at 110-120℃ for 8-12 hours. Filter, wash, and dry to obtain double bond modified support; separately take 10-20 parts of 2-mercaptothiophene, 15-35 parts of 2,3-dimercaptosuccinic acid, and 200-300 parts of anhydrous dichloromethane and stir at room temperature for 2-4 hours to obtain thiolized synergistic complex. Step 2: Addition reaction loading and purification: Add the above double bond modified support to the mercapto-enhanced complex, deoxygenate with nitrogen for 10-20 minutes, add 1-3 parts of photoinitiator Darocur 1173, and react at room temperature for 4-6 hours under 365nm ultraviolet light irradiation; after the reaction, wash 4-6 times with anhydrous dichloromethane, filter, and vacuum dry at 100-120℃ for 8-10 hours to obtain the bonded immobilized carboxylic acid purified agent.

3. The method for preparing hexafluoropropylene trimerization by enhanced catalysis according to claim 2, characterized in that: The pretreatment carrier is selected from ZSM-5 molecular sieve or MCM-41 mesoporous silica material, and the pretreatment step is calcination at 500-600℃ for 4-6 hours.

4. The method for preparing hexafluoropropylene trimerization by enhanced catalysis according to claim 1, characterized in that: The aprotic solvent is selected from dichloromethane, perfluorobutyltetrahydrofuran, or perfluoroalkane.

5. The method for preparing hexafluoropropylene trimerization by enhanced catalysis according to claim 1, characterized in that: The terminating agent is selected from deionized water or 0.1–1M HCl solution.

6. The method for preparing hexafluoropropylene trimerization by enhanced catalysis according to claim 1, characterized in that: The inert atmosphere is N2 or Ar.

7. The method for preparing hexafluoropropylene trimerization by enhanced catalysis according to claim 1, characterized in that: The decompression pressure in the decompression fractionation is 10–200 Torr.

8. The method for preparing hexafluoropropylene trimerization by enhanced catalysis according to claim 1, characterized in that: The alkaline solution is selected from 0.01–1M NaHCO3 or Na2CO3.

9. The method for preparing hexafluoropropylene trimerization by enhanced catalysis according to claim 1, characterized in that: The desiccant is selected from anhydrous MgSO4 or 3Å–5Å molecular sieves, and the amount of desiccant used is 0.1–2 times the mass of the organic layer.

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