A continuous preparation method for perfluoroisobutyronitrile

Abstract

This invention discloses a continuous preparation method for perfluoroisobutyronitrile (PFIR), comprising the following steps: A: Hexafluoropropylene and carbonyl fluoride are continuously fed into a primary reaction tube, and reacted in the presence of an organic solvent, an organic base, and a fluorinated quaternary salt to obtain a perfluoroisobutyronitrile reaction mixture; B: The perfluoroisobutyronitrile reaction mixture is then reacted with a sodium amide suspension to obtain a perfluoroisobutyramide reaction solution; C: Finally, the mixture is dehydrated by the catalytic oxidation of the metal fluoride oxide to obtain perfluoroisobutyronitrile. This invention has the advantages of continuous reaction, ease of operation, high reaction yield, and few side reactions, reducing the transfer and storage of hazardous chemicals such as carbonyl fluoride and acyl fluoride products, making the reaction safer and more controllable, and suitable for industrial production.

Description

Technical Field

[0001] This invention relates to a continuous preparation method for perfluoroisobutyronitrile. Background Technology

[0002] Perfluoroisobutyronitrile (C4F7N) has low toxicity and excellent chemical stability. Its global warming potential (GWP) is 2400, which is only about 1 / 10 of that of sulfur hexafluoride. Its ozone depletion potential (ODP) is 0. Compared with sulfur hexafluoride, its atmospheric lifetime is greatly shortened, showing a certain potential to replace sulfur hexafluoride as a gas.

[0003] Currently, there are two main technological routes for the industrialization of perfluoroisobutyronitrile (PFOS).

[0004] The first route is the ECF route, as disclosed in Chinese patent CN104662617A, which involves electrochemically fluorinating isobutyric anhydride to form heptafluoroisobutyrate methyl ester, reacting it with ammonia to generate heptafluoroisobutyramide, and finally dehydrating it with trifluoroacetic anhydride to form perfluoroisobutyronitrile. The ECF route has problems such as large consumption of dehydrating agents, large emissions of waste that are difficult to recycle and treat, and high costs.

[0005] The second route is the HFP route. Chinese patent CN107935884A discloses an addition reaction between perfluoroolefins and carbonyl fluorides to obtain acyl fluorides; the acyl fluorides then react with alkali metal amines or amino compounds to obtain amides; finally, a dehydration reaction is carried out with a dehydrating agent to obtain perfluoronitrile. In the dehydration process of heptafluoroisobutyramide, the main dehydrating agents used are one or more of trifluoroacetic anhydride, acetic anhydride, thionyl chloride, phosphorus pentoxide, or phosphorus oxychloride, and the organic solvents used are one or more of pyridine, polyphosphoric acid, carbon tetrachloride, N,N-dimethylformamide, N,N-diethylformamide, 1,4-dioxane, or dimethyl sulfoxide. The HFP route also suffers from problems such as large amounts of dehydrating agents, large emissions of waste that are difficult to recycle and treat, and high costs.

[0006] Although perfluoroisobutyramide has a mature dehydration process using dehydrating agents, it has the following drawbacks: (1) It is an intermittent process, making it difficult to achieve large-scale continuous production; (2) It uses a large amount of dehydrating agent, which easily generates a large amount of liquid or solid waste, and the consumed dehydrating agent is difficult to recycle and reuse; (3) It uses a large amount of solvent, and due to the introduction of dehydrating agent and its by-products, the solvent is difficult to recycle and reuse, generating a large amount of waste liquid and seriously polluting the environment.

[0007] While the heptafluoroisobutyramide catalytic dehydration process has gradually emerged, it can reduce the amount of waste by more than 90% and the cost by 30% to 40%, but it has defects such as high reaction temperature, poor catalyst selectivity, short lifespan, difficulty in regeneration and activation, and poor reproducibility of reaction results. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention proposes a continuous preparation method for perfluoroisobutyronitrile that is characterized by mild reaction, low waste, low cost, high catalytic activity, good product selectivity, high overall reaction yield, good reaction reproducibility, and long catalyst lifetime, making it suitable for industrial-scale production.

[0009] The objective of this invention is achieved through the following technical solution:

[0010] A continuous preparation method for perfluoroisobutyronitrile includes the following steps:

[0011] A: Hexafluoropropylene and carbonyl fluoride are continuously fed into the first-stage reaction tube, and an addition reaction is carried out in the presence of organic solvent, organic base and fluorinated quaternary salt to obtain a perfluoroisobutyryl fluoride reaction mixture.

[0012] B: Pass the perfluoroisobutyryl fluoride reaction mixture and sodium amino suspension obtained in step A into a secondary reaction tube to carry out a substitution reaction and obtain a perfluoroisobutyramide reaction solution.

[0013] C: The perfluoroisobutyramide reaction solution obtained in step B is filtered and then passed into a three-stage reaction tube, where it is dehydrated by catalytic dehydration with a metal fluoride oxide to obtain perfluoroisobutyronitrile; the metal fluoride oxide is selected from at least one of chromium fluoride oxide, molybdenum fluoride oxide, tungsten fluoride oxide, niobium fluoride oxide, and cobalt fluoride oxide.

[0014] The present invention has discovered that in step A, the organic base not only increases the reaction rate, but its combination with the fluorinated quaternary salt further enhances the reaction conversion rate, thereby increasing the reaction yield. Specifically, the organic base is selected from at least one of pyridine, triethylamine, N,N-dimethylamine, quinoline, and 4-dimethylaminopyridine; preferably, the organic base is selected from at least one of pyridine, triethylamine, and 4-dimethylaminopyridine.

[0015] The fluorinated quaternary salt is selected from at least one of tetramethylammonium fluoride, ethyltrimethylammonium fluoride, tetraethylammonium fluoride, methyltriethylammonium fluoride, tetrapropylammonium fluoride, tetrabutylammonium fluoride, benzyltrimethylammonium fluoride, benzyltriethylammonium fluoride, benzyltributylammonium fluoride, tetradecyltrimethylammonium fluoride, hexadecyltrimethylammonium fluoride, dimethyldibenzylammonium fluoride, trioctylmethylammonium fluoride, tetraphenylphosphine fluoride, triphenylmethylphosphine fluoride, triphenylethylphosphine fluoride, triphenylbutylphosphine fluoride, or triphenylbenzylphosphine fluoride; preferably, the fluorinated quaternary salt is selected from tetrabutylammonium fluoride, benzyltrimethylammonium fluoride, hexadecyltrimethylammonium fluoride, or benzyltributylammonium fluoride; more preferably, the fluorinated quaternary salt is selected from tetrabutylammonium fluoride or benzyltrimethylammonium fluoride.

[0016] The organic solvent should be able to dissolve the fluorinated quaternary salt. Preferably, the organic solvent is selected from at least one of C1 to C20 halogenated or non-halogenated aliphatic hydrocarbons, aromatic hydrocarbons, ketones, ethers, nitriles, or heterocyclic compounds. More preferably, the organic solvent is selected from at least one of acetonitrile, N,N-dimethylformamide, methyl isopropyl ether, and dichloroethane.

[0017] In step A, hexafluoropropylene and carbonyl fluoride readily produce byproduct fluoroketone compounds, which can affect the selectivity and yield of the reaction. This invention, by adjusting the ratio of reactants, reaction temperature, and residence time of materials, can achieve highly selective production of perfluoroacyl fluoride compounds, effectively avoiding the formation of byproduct fluoroketone compounds.

[0018] Specifically, the molar ratio of organic base, catalyst, hexafluoropropylene, and acyl fluoride compound is 0.01–0.05:0.02–0.2:1:1–5, the reaction temperature is 50–150°C, the residence time of the reactants is 5–40 s, and the resulting perfluoroisobutyramide reaction solution is substantially free of bis(perfluoroisopropyl)ketone. Preferably, the molar ratio of organic base, catalyst, hexafluoropropylene, and acyl fluoride compound is 0.01–0.03:0.02–0.1:1:1–2, the reaction temperature is 50–100°C, and the residence time of the reactants is 10–25 s.

[0019] In step B, the sodium amide suspension needs to be able to react with perfluoroisobutyryl fluoride. Preferably, the mass concentration of the sodium amide suspension is 10%–20%. The molar ratio of the perfluoroisobutyryl fluoride reaction mixture to the sodium amide suspension is 1:1–1.2, the reaction temperature is -30–25°C, and the residence time of the reactants is 1–500 s. Preferably, the molar ratio of the perfluoroisobutyryl fluoride reaction mixture to the sodium amide suspension is 1:1.05–1.15, the reaction temperature is -30–0°C, and the residence time of the reactants is 10–100 s. Alternatively, the molar ratio of the perfluoroisobutyryl fluoride reaction mixture to the sodium amide suspension is 1:1.05–1.1, the reaction temperature is -30–0°C, and the residence time of the reactants is 10–50 s.

[0020] In step C, the catalytic dehydration reaction temperature of the perfluoroisobutyramide reaction solution is 100℃~300℃, the reaction pressure is 0.2~2.0MPa, and the residence time is 1~2000s; preferably, the catalytic dehydration reaction temperature of the perfluoroisobutyramide reaction solution is 150℃~250℃, the reaction pressure is 0.5~1.5MPa, and the residence time is 10~1000s; more preferably, the catalytic dehydration reaction temperature of the perfluoroisobutyramide reaction solution is 150℃~200℃, the reaction pressure is 0.5~1.0MPa, and the residence time is 100~1000s.

[0021] The present invention has found that the molar ratio of metal element, fluorine element and oxygen element in the metal fluoride oxide is 1:(1~4):(0.5~2); preferably, the molar ratio of metal element, fluorine element and oxygen element in the metal fluoride oxide is 1:(1~2):(0.5~1).

[0022] Specifically, the metal fluoride oxide is prepared by the following steps:

[0023] An alkaline solution is added dropwise to a metal salt solution to induce precipitation. The precipitate is dried to obtain a catalyst precursor. The catalyst precursor is then fluorinated with a fluorinating agent to obtain a metal fluoride oxide. The metal salt solution is obtained by dissolving or dispersing the metal oxide raw material in water.

[0024] Specifically, in this invention, the metal oxide raw material can be provided by salts of any corresponding valence state, such as chromium (III) ions, molybdenum (VI) ions, tungsten (VI) ions, niobium (VI) ions, and cobalt (VI) ions. Salts of chromium ions include, but are not limited to, chromium nitrate or its hydrated crystalline compounds, and chromium chloride or its hydrated crystalline compounds; salts of molybdenum ions include, but are not limited to, molybdic acid, ammonium molybdate and its hydrated crystalline compounds, potassium molybdate, calcium molybdate, copper molybdate, and barium molybdate; salts of tungsten ions include, but are not limited to, tungstic acid, ammonium tungstate and its hydrated crystalline compounds, ammonium paratungstate and its hydrated crystalline compounds, sodium tungstate, and tungsten chloride; salts of niobium ions include, but are not limited to, niobium chloride, niobium oxalate, sodium niobate, potassium niobate, and niobium fluoride; and salts of cobalt ions include, but are not limited to, cobalt oxalate, cobalt nitrate, cobalt chloride, and its hydrated crystalline compounds.

[0025] Preferably, during the preparation process, a fluorinated surfactant is added to the metal salt solution, and the molar ratio of the fluorinated surfactant to the metal oxide raw material is (0.0004~0.025):1.

[0026] The fluorinated surfactant can control the average pore size of the catalyst precursor during the preparation of the metal fluoride, so that the metal fluoride has a suitable pore size, thereby solving the adverse effects of high pressure on the activity of metal fluoride. This allows the fluoride metal catalyst of the present invention to still have high conversion rate, high selectivity and good stability under high pressure.

[0027] The fluorinated surfactant is PFOA or a compound with a similar structure. Preferably, the fluorinated surfactant is selected from at least one of perfluorooctyl sulfonyl fluoride, sodium perfluorononenoxybenzenesulfonate, tridecylfluorohexanesulfonic acid, or potassium perfluorooctyl sulfonate.

[0028] The fluorinating agent is a mixture of an inert gas and hydrogen fluoride, which reacts with the catalyst precursor at 200–400°C. The inert gas is selected from at least one of nitrogen, helium, and argon.

[0029] In one specific embodiment, the metal fluoride oxide of the present invention is prepared by the following steps:

[0030] A metal salt solution is obtained by dissolving or uniformly suspending a metal oxide raw material and a fluorinated surfactant in deionized water. Concentrated ammonia (25%–28% by mass) is added dropwise to precipitate the metal salt, and the pH of the solution is controlled at 8–10. The precipitate is washed until the pH is 7–8 and dried in an oven at 80–100°C for 12–24 hours to obtain a catalyst precursor. The precursor is then calcined at 300–500°C for 5–24 hours under inert gas protection. A mixture of inert gas and hydrogen fluoride is then introduced, and the precursor is fluorinated at 200–400°C to obtain the metal fluoride oxide.

[0031] When the metal fluoride oxide prepared above is used in the liquid-phase catalytic preparation of perfluoroisobutyronitrile, the lifetime of the metal fluoride oxide is 500–2000 h, and the space-time yield is 0.5–1.5 t / (m²). 3 Generally, when the reaction temperature is about 150–200°C, the catalyst lifetime is about 1000–2000 h; when the reaction temperature is about 200–300°C, the catalyst lifetime is about 500–1000 h. Preferably, the metal fluoride oxide lifetime is 1000–2000 h, and the space-time yield is 1.0–1.5 t / (m³). 3 cat·h).

[0032] Furthermore, the metal fluoride oxide of the present invention can be easily regenerated once deactivated. Specifically, the catalyst is regenerated by purging with air and / or oxygen at 500–800°C.

[0033] The continuous reactor described in this invention is a tubular reactor, a coil reactor, or a microchannel reactor.

[0034] Generally, the primary and secondary reaction tubes suitable for this invention are coil reactors or microchannel reactors, and the tertiary reaction tubes suitable for this invention are tubular reactors.

[0035] The continuous preparation method described in this invention is not only easy to operate, reducing the complexity of batch reaction, but also reduces the transfer and storage of hazardous chemicals such as acyl fluoride products. Furthermore, the product purity of each reaction step is high, saving the steps that require separation and purification in each process. Only the final product, perfluoroisobutyronitrile, needs to be purified.

[0036] Specifically, the refining process of the perfluoroisobutyronitrile prepared by the present invention includes the following steps: the reactants from the tertiary reaction tube are first separated by a gas-liquid separator, the liquid material in the separator is the remaining material and is then circulated back to the primary reaction tube through a bypass to continue the reaction, and the gas is subjected to two-stage cryogenic cooling through a cryogenic device to obtain the perfluoroisobutyronitrile product.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] 1. This invention has the advantages of continuous reaction being easy to operate, high reaction yield, and few side reactions, reducing the transfer and storage of hazardous chemicals such as carbonyl fluoride and acyl fluoride products, making the reaction safer and more controllable, and suitable for industrial production;

[0039] 2. The preparation of perfluoroisobutyronitrile using the metal fluoride oxide described in this invention exhibits good catalytic activity, good product selectivity, good reaction reproducibility, long catalyst lifetime, and easy activation and regeneration. Attached Figure Description

[0040] Appendix Figure 1 The continuous preparation process flow diagram of Embodiment 1 of the present invention is as follows: 1-first stage reaction tube, 2-second stage reaction tube, 3-third stage reaction tube, 4-first feed pump, 5-second feed pump, 6-third feed pump, 7-filter, 8-separation tank, 9-cryogenic equipment, 10-remaining materials. Detailed Implementation

[0041] 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.

[0042] In this embodiment of the invention, gas chromatography was used for analysis. The analytical instrument was a Shimadzu GC-2014; the chromatographic column was a GAS-Pro (60m x 0.32mm x 1.0um). GC analysis method: detector temperature 250℃, vaporization chamber temperature 250℃, column temperature: 60℃ (5min) 10℃ / min, 85℃ (3min) 10℃ / min, 250℃ (4min); carrier gas (N2) flow rate 1.05mL / min, air flow rate 300mL / min, hydrogen flow rate 30mL / min, split ratio 50:1, injection volume 0.2mL.

[0043] Preparation Example 1

[0044] 120g of Cr(NO3)3·9H2O was dissolved in 480ml of deionized water. Then, 150g of a 10% (w / w) ammonia solution was added to the solution, maintaining the final pH between 6.5 and 10.0. The solution was filtered, and the precipitate was washed with deionized water until neutral. After drying in air at 110℃ for 16 hours, a catalyst precursor was obtained. The catalyst precursor was then pressed into tablets, loaded into a reactor, and calcined at 400℃ in a nitrogen atmosphere. A mixture of nitrogen and hydrogen fluoride (20% hydrogen fluoride by volume) was then introduced, and fluorination was performed at 200–400℃ to prepare a chromium-based fluorination catalyst, denoted as Cat1.

[0045] The composition of Cat1 (at%) was analyzed using an energy dispersive spectroscopy (EDX) instrument: Cr:O:F = 41.23:15.94:42.83.

[0046] Preparation Example 2

[0047] 60g of H₂MoO₄ was weighed and uniformly dispersed in 200ml of deionized water, and 0.1g of potassium perfluorooctyl sulfonate was added and stirred to dissolve. Then, 350g of ammonia solution (25%) was added to the above solution, and the final pH value of the solution was controlled between 8 and 10. The solution was filtered, and the precipitate was washed with deionized water until neutral. After drying in air at 110℃ for 16 hours, the catalyst precursor was obtained. The catalyst precursor was then pressed into tablets and loaded into a reactor. It was calcined at 400℃ in a nitrogen atmosphere, and then fluorinated at 400℃ by introducing a mixed gas of nitrogen and hydrogen fluoride (hydrogen fluoride volume fraction 20%) to prepare a molybdenum fluoride oxidase catalyst, denoted as Cat2.

[0048] EDX analysis showed that the composition of Cat2 (at%) was: Mo:F:O = 1:2.11:1.85.

[0049] Preparation Example 3

[0050] 60g of H2WO4 was weighed and uniformly dispersed in 200ml of deionized water, and 0.1g of potassium perfluorooctyl sulfonate was added and stirred to dissolve. Then, 240g of ammonia solution (25%) was added to the above solution, controlling the final pH value of the solution between 8 and 10. The solution was filtered, and the precipitate was washed with deionized water until neutral. After drying in air at 110℃ for 16 hours, the catalyst precursor was obtained. The catalyst precursor was then pressed into tablets and loaded into a reactor. It was calcined at 400℃ in a nitrogen atmosphere, and then fluorinated at 200-400℃ with a mixture of nitrogen and hydrogen fluoride (hydrogen fluoride volume fraction 20%) to produce a tungsten fluoride oxyfluoride catalyst, denoted as Cat3.

[0051] EDX analysis showed that the composition of Cat3 (at%) was W:F:O = 1:4.02:0.98.

[0052] Preparation Example 4

[0053] 100g of NbCl5 was weighed and uniformly dispersed in 300ml of deionized water, and 0.1g of potassium perfluorooctyl sulfonate was added and stirred to dissolve. Then, 310g of ammonia solution (25%) was added to the above solution, controlling the final pH value of the solution between 8 and 10. The solution was filtered, and the precipitate was washed with deionized water until neutral. After drying in air at 110℃ for 16 hours, the catalyst precursor was obtained. The catalyst precursor was then pressed into tablets and loaded into a reactor. It was calcined at 400℃ in a nitrogen atmosphere, and then fluorinated at 400℃ with a mixture of nitrogen and hydrogen fluoride (hydrogen fluoride volume fraction 20%) to produce a niobium fluoride oxyfluoride catalyst, denoted as Cat4.

[0054] EDX analysis showed that the composition of Cat4 (at%) was: Nb:F:O = 1:3.02:1.51.

[0055] Preparation Example 5

[0056] 120g of Co(NO3)2·6H2O was weighed and dissolved in 480ml of deionized water. 0.1g of potassium perfluorooctyl sulfonate was added and stirred until dissolved. Then, 140g of ammonia solution (25%) was added to the solution, controlling the final pH value of the solution to be between 8 and 10. The solution was filtered, and the precipitate was washed with deionized water until neutral. After drying in air at 110℃ for 16 hours, a catalyst precursor was obtained. The catalyst precursor was then pressed into tablets, loaded into a reactor, and calcined at 400℃ in a nitrogen atmosphere. A mixture of nitrogen and hydrogen fluoride (20% hydrogen fluoride by volume) was then introduced, and fluorination was performed at 400℃ to prepare a cobalt fluoride oxyfluoride catalyst, denoted as Cat5.

[0057] EDX analysis showed that the composition of Cat5 (at%) was: Co:F:O = 1:1.09:0.53.

[0058] Comparative Preparation Example 1

[0059] With a 20% alkali cesium fluoride and 80% activated carbon support composition, alkali metal fluorides were impregnated onto activated carbon at 50°C using an impregnation method. After filtration and drying at 80°C for 24 hours, a catalyst precursor was obtained. 10 mL of the catalyst precursor was loaded into a Monel tubular reactor with an inner diameter of 1 / 2 inch and a length of 30 cm, and calcined at 300°C for 6 hours under nitrogen gas with a nitrogen space velocity of 200 h⁻¹. -1 A cesium fluoride catalyst with activated carbon as a support was prepared and designated CatD1.

[0060] Comparative Preparation Example 2

[0061] The preparation method of the catalyst in the repeated patent CN109320436A, taking cobalt oxide as an example, is as follows: cobalt nitrate hydrate is dissolved in water, concentrated ammonia is added dropwise for precipitation, the pH value is adjusted to 7.5, then aged for 12 hours, washed with water and filtered, dried in an oven at 80℃ for 36 hours, and then calcined at 450℃ for 8 hours under nitrogen protection to obtain cobalt oxide, denoted as CatD2.

[0062] Example 1

[0063] A: Using the first feed pump 4, hexafluoropropylene, carbonyl fluoride, pyridine and acetonitrile solution of dissolved fluorinated quaternary salt are continuously fed into the first-stage reaction tube 1. The reaction temperature is controlled at 80℃ and the residence time is 10-20s to obtain a perfluoroisobutyryl fluoride reaction solution with complete reaction in equal proportion.

[0064] B: The perfluoroisobutyryl fluoride reaction solution is directly introduced into the secondary reaction tube 2, and the sodium amino acetonitrile solution is introduced into the secondary reaction tube 2 by means of the second feed pump 5. The reaction temperature is controlled at -30 to -20℃ and the residence time is 20 to 30s. The specific feed molar ratio of hexafluoropropylene / carbonyl fluoride / pyridine / tetrabutylammonium fluoride / sodium amino is shown in Table 1. The perfluoroisobutyramide reaction solution is obtained.

[0065] C: The effluent from the secondary reaction tube 2 is filtered by filter 7 to separate the fluoride salt and obtain an acetonitrile solution of amide (amide mass concentration 50%). The solution is then fed into the tertiary reaction tube 3 using the third feed pump 6. The tertiary reaction tube 3 is filled with 50g of the chromium fluoride catalyst (Cat1) prepared in Preparation Example 1. The reaction temperature is controlled at 150°C, the residence time is 600s, and the reaction pressure is 0.5MPa. The reaction pressure is controlled by the unloading valve.

[0066] D: The reactants coming out of the tertiary reaction tube 3 are first separated by the gas-liquid separator 8. The liquid material in the separator is the residual material 10, which is then circulated back to the primary reaction tube 1 through a bypass. The gas is subjected to two-stage cryogenic treatment by the cryogenic equipment 9. The first stage separates water and high-boiling substances at 0°C, and the second stage separates perfluoroisobutyronitrile products at -10°C and fills them into steel cylinders. The non-condensable gas is discharged after being washed with alkali.

[0067] The perfluoroisobutyronitrile (PFOS) product was analyzed by GC. The changes in the overall yield and purity of the PFOS under different reaction conditions are shown in Table 1 below:

[0068] Table 1. Changes in product content under different reaction conditions in Example 1

[0069]

[0070] Example 2

[0071] A: Using a feed pump, hexafluoropropylene, carbonyl fluoride, pyridine, and acetonitrile solution of tetrabutylammonium fluoride are continuously fed into the first-stage reaction tube. The reaction temperature is controlled at 70°C and the residence time is 20s to obtain a perfluoroisobutyryl fluoride reaction solution with complete reaction in equal proportions.

[0072] B: The perfluoroisobutyryl fluoride reaction solution is directly introduced into the secondary reaction tube, and the sodium amino acetonitrile solution is introduced into the secondary reaction tube by means of a slurry pump. The reaction temperature is controlled at -30℃ and the residence time is 30s. The feed molar ratio of hexafluoropropylene / carbonyl fluoride / pyridine / tetrabutylammonium fluoride / sodium amino is 1:1:0.01:0.2:1.05 to obtain the perfluoroisobutyramide reaction solution.

[0073] C: The effluent from the secondary reaction tube, after being filtered to separate the fluoride salt, yields an acetonitrile solution of amide (amide mass concentration 50%), which is then introduced into the tertiary reaction tube. The tertiary reaction tube is filled with 50g of the molybdenum fluoride catalyst (Cat2) prepared in Example 2. The reaction temperature is controlled at 150°C, the residence time is 600s, and the reaction pressure is 0.5MPa. The reaction pressure is controlled by an unloading valve.

[0074] D: The reactants coming out of the tertiary reaction tube are first separated in a gas-liquid separator. The liquid material in the separator is discharged and then circulated to the primary reaction tube through a bypass. The gas undergoes two stages of deep cooling. The first stage separates water and high-boiling substances at 0°C, and the second stage separates perfluoroisobutyronitrile products at -10°C and fills them into steel cylinders. The non-condensable gas is discharged after being washed with alkali.

[0075] The perfluoroisobutyronitrile product was analyzed by GC, and the purity of the perfluoroisobutyronitrile reaction was 98.9%, with an overall reaction yield of 88.4%.

[0076] Example 3

[0077] A: Using a feed pump, hexafluoropropylene, carbonyl fluoride, pyridine, and acetonitrile solution of tetrabutylammonium fluoride are continuously fed into the first-stage reaction tube. The reaction temperature is controlled at 70°C and the residence time is 20s to obtain a perfluoroisobutyryl fluoride reaction solution with complete reaction in equal proportions.

[0078] B: The perfluoroisobutyryl fluoride reaction solution is directly introduced into the secondary reaction tube, and the sodium amino acetonitrile solution is introduced into the secondary reaction tube by means of a slurry pump. The reaction temperature is controlled at -30℃ and the residence time is 30s. The feed molar ratio of hexafluoropropylene / carbonyl fluoride / pyridine / tetrabutylammonium fluoride / sodium amino is 1:1:0.01:0.2:1.05 to obtain the perfluoroisobutyramide reaction solution.

[0079] C: The effluent from the secondary reaction tube, after being filtered to separate the fluoride salt, yields an acetonitrile solution of amide (amide mass concentration 50%), which is then introduced into the tertiary reaction tube. The tertiary reaction tube is filled with 50g of the tungsten fluoride catalyst (Cat3) prepared in Example 3. The reaction temperature is controlled at 150°C, the residence time is 600s, and the reaction pressure is 0.5MPa. The reaction pressure is controlled by an unloading valve.

[0080] D: The reactants coming out of the tertiary reaction tube are first separated in a gas-liquid separator. The liquid material in the separator is discharged and then circulated to the primary reaction tube through a bypass. The gas undergoes two stages of deep cooling. The first stage separates water and high-boiling substances at 0°C, and the second stage separates perfluoroisobutyronitrile products at -10°C and fills them into steel cylinders. The non-condensable gas is discharged after being washed with alkali.

[0081] The perfluoroisobutyronitrile product was analyzed by GC, and the purity of the perfluoroisobutyronitrile reaction was 99.2%, with an overall reaction yield of 91.3%.

[0082] Example 4

[0083] A: Using a feed pump, hexafluoropropylene, carbonyl fluoride, pyridine, and acetonitrile solution of tetrabutylammonium fluoride are continuously fed into the first-stage reaction tube. The reaction temperature is controlled at 70°C and the residence time is 20s to obtain a perfluoroisobutyryl fluoride reaction solution with complete reaction in equal proportions.

[0084] B: The perfluoroisobutyryl fluoride reaction solution is directly introduced into the secondary reaction tube, and the sodium amino acetonitrile solution is introduced into the secondary reaction tube by means of a slurry pump. The reaction temperature is controlled at -30℃ and the residence time is 30s. The feed molar ratio of hexafluoropropylene / carbonyl fluoride / pyridine / tetrabutylammonium fluoride / sodium amino is 1:1:0.01:0.2:1.05 to obtain the perfluoroisobutyramide reaction solution.

[0085] C: The effluent from the secondary reaction tube, after being filtered to separate the fluoride salt, yields an acetonitrile solution of amide (amide mass concentration 50%), which is then introduced into the tertiary reaction tube. The tertiary reaction tube is filled with 50g of the niobium fluoride catalyst (Cat4) prepared in Example 4. The reaction temperature is controlled at 150°C, the residence time is 600s, and the reaction pressure is 0.5MPa. The reaction pressure is controlled by an unloading valve.

[0086] D: The reactants coming out of the tertiary reaction tube are first separated in a gas-liquid separator. The liquid material in the separator is discharged and then circulated to the primary reaction tube through a bypass. The gas undergoes two stages of deep cooling. The first stage separates water and high-boiling substances at 0°C, and the second stage separates perfluoroisobutyronitrile products at -10°C and fills them into steel cylinders. The non-condensable gas is discharged after being washed with alkali.

[0087] The perfluoroisobutyronitrile product was analyzed by GC, and the purity of the perfluoroisobutyronitrile reaction was 97.3%, with an overall reaction yield of 84.2%.

[0088] Example 5

[0089] A: Using a feed pump, hexafluoropropylene, carbonyl fluoride, pyridine, and acetonitrile solution of tetrabutylammonium fluoride are continuously fed into the first-stage reaction tube. The reaction temperature is controlled at 70°C and the residence time is 20s to obtain a perfluoroisobutyryl fluoride reaction solution with complete reaction in equal proportions.

[0090] B: The perfluoroisobutyryl fluoride reaction solution is directly introduced into the secondary reaction tube, and the sodium amino acetonitrile solution is introduced into the secondary reaction tube by means of a slurry pump. The reaction temperature is controlled at -30℃ and the residence time is 30s. The feed molar ratio of hexafluoropropylene / carbonyl fluoride / pyridine / tetrabutylammonium fluoride / sodium amino is 1:1:0.01:0.2:1.05 to obtain the perfluoroisobutyramide reaction solution.

[0091] C: The effluent from the secondary reaction tube, after being filtered to separate the fluoride salt, yields an acetonitrile solution of amide (amide mass concentration 50%), which is then introduced into the tertiary reaction tube. The tertiary reaction tube is filled with 50g of the cobalt fluoride catalyst (Cat5) prepared in Example 5. The reaction temperature is controlled at 150°C, the residence time is 600s, and the reaction pressure is 0.5MPa. The reaction pressure is controlled by an unloading valve.

[0092] D: The reactants coming out of the tertiary reaction tube are first separated in a gas-liquid separator. The liquid material in the separator is discharged and then circulated to the primary reaction tube through a bypass. The gas undergoes two stages of deep cooling. The first stage separates water and high-boiling substances at 0°C, and the second stage separates perfluoroisobutyronitrile products at -10°C and fills them into steel cylinders. The non-condensable gas is discharged after being washed with alkali.

[0093] The perfluoroisobutyronitrile product was analyzed by GC, and the purity of the perfluoroisobutyronitrile reaction was 91.5%, with an overall reaction yield of 72.3%.

[0094] Comparative Example 1

[0095] A: 10 mL of catalyst CatD1 was packed into a tubular reactor made of Incon alloy with an inner diameter of 1 / 2 inch and a length of 30 cm. The reaction conditions were: reaction temperature 160 °C, molar ratio of carbonyl fluoride to hexafluoropropylene 3:1, contact time 0.1 s, reaction pressure 0.1 MPa, and reaction time 10 hours. The reaction product, perfluoroisobutyryl fluoride, was collected using a polytetrafluoroethylene sampling bag.

[0096] B: In a 1-liter, 316 stainless steel autoclave, after evacuation, 0.5 mol of perfluoroisobutyryl fluoride and 1.5 mol of sodium amide are rapidly introduced at -40°C with stirring. After the introduction is complete, the temperature is maintained at 15°C and the reaction time is 20 hours. After the reaction is complete, 2.0 mol of phosphorus oxychloride is added directly. After evacuation, the temperature is raised to 180°C and the reaction time is 6 hours. After the reaction is complete, the gaseous product perfluoroisobutyronitrile in the reaction system is collected using a 200mL small steel bottle made of 316 stainless steel.

[0097] The perfluoroisobutyronitrile product was analyzed by GC, and the purity of the perfluoroisobutyronitrile reaction was 90.1%, with an overall reaction yield of 70.1%.

[0098] Comparative Example 2

[0099] A: 10 mL of CatD1 catalyst was packed into a tubular reactor made of Incon alloy with an inner diameter of 1 / 2 inch and a length of 30 cm. The reaction conditions were: reaction temperature 160 °C, molar ratio of carbonyl fluoride to hexafluoropropylene 3:1, contact time 0.1 s, reaction pressure 0.1 MPa, and reaction time 10 hours. The reaction product, perfluoroisobutyryl fluoride, was collected using a polytetrafluoroethylene sampling bag.

[0100] B: The reaction was carried out in a tubular reactor made of Incon alloy with an outer diameter of 1 / 2 inch and an internal volume of 30 ml. The reaction conditions were: reaction temperature 150°C, molar ratio of perfluoroisobutyryl fluoride to methylamine 1:3, contact time 10 s, and reaction pressure 0.1 MPa. The reaction stream was condensed and collected in a polytetrafluoroethylene bottle, with the solid remaining at the bottom of the bottle and the gas phase being discharged from the system. After 10 hours of reaction, solid perfluoroisobutyrylamide was obtained.

[0101] C: 10 mL of CatD2 catalyst was packed into a tubular reactor made of Incon alloy with an outer diameter of 1 / 2 inch and an internal volume of 30 mL. The reaction conditions were: reaction temperature 400℃, contact time of perfluoroisobutyramide 10 s, and reaction pressure 0.1 MPa. The reaction stream from the reaction tube first flowed through a polytetrafluoroethylene bottle for condensation, with the solids retained at the bottom of the bottle. Then, it passed through a drying tube to remove moisture. Finally, the reaction stream entered a 200 mL stainless steel bottle made of 316 stainless steel to collect the gaseous product perfluoroisobutyronitrile in the reaction system.

[0102] The perfluoroisobutyronitrile product was analyzed by GC, and the purity of the perfluoroisobutyronitrile reaction was 6.9%, with an overall reaction yield of 36.3%.

Claims

1. A continuous preparation method for perfluoroisobutyronitrile, characterized in that: The preparation method includes the following steps: A: Hexafluoropropylene and carbonyl fluoride are continuously fed into the first-stage reaction tube, and an addition reaction is carried out in the presence of organic solvent, organic base and fluorinated quaternary salt to obtain a perfluoroisobutyryl fluoride reaction mixture. B: Pass the perfluoroisobutyryl fluoride reaction mixture and sodium amino suspension obtained in step A into a secondary reaction tube to carry out a substitution reaction and obtain a perfluoroisobutyramide reaction solution. C: The perfluoroisobutyramide reaction solution obtained in step B is filtered and then passed into a three-stage reaction tube, where it is dehydrated by catalytic dehydration with a metal fluoride oxide to obtain perfluoroisobutyronitrile; the metal fluoride oxide is selected from at least one of chromium fluoride oxide, molybdenum fluoride oxide, tungsten fluoride oxide, niobium fluoride oxide, and cobalt fluoride oxide.

2. The continuous preparation method of perfluoroisobutyronitrile according to claim 1, characterized in that: In step A, the organic base is selected from at least one of pyridine, triethylamine, N,N-dimethylamine, quinoline, or 4-dimethylaminopyridine; the organic solvent is selected from at least one of acetonitrile, N,N-dimethylformamide, methyl isopropyl ether, or dichloroethane; and the fluorinated quaternary salt is selected from at least one of tetramethylammonium fluoride, ethyltrimethylammonium fluoride, tetraethylammonium fluoride, methyltriethylammonium fluoride, tetrapropylammonium fluoride, tetrabutylammonium fluoride, benzyltrimethylammonium fluoride, benzyltriethylammonium fluoride, benzyltributylammonium fluoride, tetradecyltrimethylammonium fluoride, hexadecyltrimethylammonium fluoride, dimethyldibenzylammonium fluoride, trioctylmethylammonium fluoride, tetraphenylphosphine fluoride, triphenylmethylphosphine fluoride, triphenylethylphosphine fluoride, triphenylbutylphosphine fluoride, or triphenylbenzylphosphine fluoride.

3. The continuous preparation method of perfluoroisobutyronitrile according to claim 1, characterized in that: In step A, the molar ratio of the organic base, catalyst, hexafluoropropylene, and acyl fluoride compound is 0.01–0.05:0.02–0.2:1:1–5, the reaction temperature is 50–150°C, and the residence time of the reactants is 5–40 s.

4. The continuous preparation method of perfluoroisobutyronitrile according to claim 1, characterized in that: In step B, the molar ratio of the perfluoroisobutyryl fluoride reaction mixture and the sodium amino suspension is 1:1 to 1.2, the reaction temperature is -30℃ to 25℃, and the residence time of the reactants is 1 to 500s.

5. The continuous preparation method of perfluoroisobutyronitrile according to claim 1, characterized in that: In step C, the reaction temperature is 100℃~300℃, the reaction pressure is 0.2~2.0Mpa, and the residence time is 1~2000s.

6. The continuous preparation method of perfluoroisobutyronitrile according to claim 1, characterized in that: In step C, the molar ratio of the metal element, fluorine element and oxygen element in the metal fluoride oxide is 1:(1~4):(0.5~2).

7. The continuous preparation method of perfluoroisobutyronitrile according to claim 1, characterized in that: In step C, the metal fluoride oxide is prepared through the following steps: Alkali solution is added dropwise to a metal salt solution to induce precipitation. The precipitate is dried to obtain a catalyst precursor. The catalyst precursor is then fluorinated with a fluorinating agent to obtain metal fluoride oxides. The metal salt solution is obtained by dissolving or dispersing metal oxide raw materials in water.

8. The continuous preparation method of perfluoroisobutyronitrile according to claim 7, characterized in that: In the preparation process, a fluorinated surfactant is added to the metal salt solution, and the molar ratio of the fluorinated surfactant to the metal oxide raw material is (0.0004~0.025):

1.

9. The continuous preparation method of perfluoroisobutyronitrile according to claim 8, characterized in that: The fluorinated surfactant is selected from at least one of perfluorooctyl sulfonyl fluoride, sodium perfluorononenoxybenzenesulfonate, tridecylfluorohexanesulfonic acid, or potassium perfluorooctyl sulfonate.

10. The continuous preparation method of perfluoroisobutyronitrile according to claim 7, characterized in that: The fluorinating agent is a mixture of inert gas and hydrogen fluoride, which reacts with the catalyst precursor at 200–400°C.

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