CN118619826A - A method for synthesizing hexafluoropropylene oxide trimer - Google Patents

Abstract

The present application relates to the technical field of fluorine-containing fine chemicals, and in particular to a method for synthesizing a trimer of hexafluoropropylene oxide, comprising subjecting hexafluoropropylene oxide to polymerization in a solvent under the action of a solid-supported amination ionic liquid catalyst to obtain a trimer of hexafluoropropylene oxide, wherein the solid-supported amination ionic liquid catalyst is composed of a 1-(3-aminopropyl)-3-alkyl imidazole chloride ionic liquid and an H-type 732 cation exchange resin carrier. The present application has the effect of providing a method for synthesizing a trimer of hexafluoropropylene oxide with simple reaction conditions and a relatively stable catalyst.

Description

A method for synthesizing hexafluoropropylene oxide trimer

Technical Field

The present application relates to the technical field of fluorine-containing fine chemicals, and in particular to a method for synthesizing a hexafluoropropylene oxide trimer.

Background Art

Hexafluoropropylene oxide trimer is the product obtained by the polymerization reaction of hexafluoropropylene oxide under the action of nucleophilic reagents. Since the phthaloyl group at the end of its molecule is very active, it can react with a variety of compounds to generate a series of fluorinated compounds. It is particularly widely used in the preparation of fluorinated surfactants. For example, it can be hydrolyzed into the corresponding carboxylic acid and used to replace PFOA in the synthesis of PVDF, which has a high value.

German patent with publication number DE 2627986 discloses a method of using bis(dialkylamino)difluoromethane as a catalyst to polymerize HFPO to obtain trimers and tetramers. However, the reaction time of this technical solution is relatively long, and the reaction temperature is -20°C to -30°C, which is relatively low, and the requirements for reaction equipment are relatively high. In addition, this technical solution simultaneously obtains trimers and tetramers, but the selectivity is poor and the reaction yield is relatively low.

Chinese invention patent publication number CN1022240C discloses a method for producing perfluoroacyl fluoride. The catalyst system used in the technical solution is composed of alkali metal fluoride, nitrile and ether. The HFPO oligomers prepared by the method are mainly between dimer and pentamer, and the selectivity of trimer is only about 60% at most, and the yield is low.

The Chinese invention patent with publication number CN117486714A discloses a method for synthesizing hexafluoropropylene oxide dimer by catalysis of imidazole-type ionic liquid. The preparation method is as follows: S1. adding the imidazole-type ionic liquid catalyst to the solvent, stirring evenly, and performing activation treatment; S2. introducing hexafluoropropylene oxide into the activated mixed solution for reaction, and obtaining a crude product of hexafluoropropylene oxide dimer after the reaction; S3. subjecting the crude product obtained in S2 to atmospheric distillation, and obtaining a pure product of hexafluoropropylene oxide dimer after distillation; S4. reusing the catalyst and the solvent, and repeating the steps of S2 and S3 for multiple times to obtain hexafluoropropylene oxide dimer; the imidazole-type ionic liquid catalyst is metal-functionalized methylbisimidazole chloride M-(MimCleimCl-COO) ₂ , wherein M is one of zinc, copper, cobalt and iron. In this technical solution, polymers with different numbers of monomers can be prepared by changing the valence state of the metal catalyst. Phosphamide is compounded with a monovalent metal fluoride salt to prepare a hexafluoropropylene oxide dimer. Phosphamide is compounded with a divalent metal fluoride salt to prepare a hexafluoropropylene oxide trimer. The content of the dimer or trimer is more than 80%. However, the solubility of zinc fluoride, barium fluoride and magnesium fluoride in organic solvents is extremely poor, and the fluoride ions in the catalyst system solution are also very small. Therefore, the catalyst has a short life and is prone to failure.

The Chinese invention patent with publication number CN110041192B provides a method for preparing a hexafluoropropylene oxide trimer, which uses hexafluoropropylene oxide as a raw material, hexafluoropropylene oxide dimer alcohol salt and fluorinated alkali metal salt as a composite catalytic initiator, and under the condition of adding a chain transfer inhibitor, a hexafluoropropylene oxide trimer is obtained through reaction, and the selectivity can reach about 80%. However, the hexafluoropropylene oxide dimer alcohol salt is very unstable and has certain defects in preparation and storage, which is not conducive to industrialization.

A Chinese invention patent with publication number CN111138274B discloses a method for preparing HFPO trimer, comprising the following steps: (1) adding a proton inert solvent and a catalyst to a reactor under a protective gas atmosphere, stirring and dispersing them uniformly, wherein the catalyst is a mixture of silver nitrate and alkali metal fluoride; (2) introducing HFPO gas into the reactor, and controlling the temperature in the reactor at 10°C to 30°C to carry out a polymerization reaction; after the reaction is completed, adjusting the temperature of the reactor to room temperature, allowing the reaction liquid to stand for stratification, and recovering the lower layer material to obtain HFPO trimer. In this technical solution, silver nitrate and alkali metal fluoride are used as a mixed catalyst system. By adjusting the ratio of the two, the trimer content can reach up to 91%, but silver nitrate is photosensitivity, has poor stability, and produces nitrous acid gas, and has low operational safety.

The Chinese invention patent with publication number CN112958017B discloses an apparatus and method for continuously producing hexafluoropropylene oxide trimer. The product of the first stage reactor is mainly dimer, and the product of the second stage reactor is mainly trimer. The catalyst system in the second stage reaction is mainly monovalent alkali metal fluoride, wherein a mixed solvent and auxiliary agents such as crown ether are used to increase the solubility of the alkali metal in the reaction solvent. The yield of the trimer can reach more than 80%, but the reaction system becomes more complicated, the reaction temperature is as low as -30 to 5°C, and the monovalent alkali metal fluoride such as cesium fluoride and potassium fluoride has strong water absorption and needs to be dried in advance.

In the existing technical means, the synthesis of hexafluoropropylene oxide trimer is mainly based on the use of amines or fluorides in combination with other additives. Although a higher trimer yield can be obtained, the catalyst system still needs to be improved in terms of stability, operational safety, complexity, etc. Therefore, it is still necessary to develop a new method for the synthesis of hexafluoropropylene oxide trimer.

Summary of the invention

The technical problem to be solved by the present invention is to provide a method for synthesizing a hexafluoropropylene oxide trimer with high yield, simple reaction conditions and relatively stable catalyst.

In order to solve the above technical problems, the present invention adopts the following technical solutions:

A method for synthesizing hexafluoropropylene oxide, wherein hexafluoropropylene oxide is polymerized in a solvent under the action of a solid-supported amination ionic liquid catalyst to obtain a hexafluoropropylene oxide trimer, wherein the solid-supported amination ionic liquid catalyst is composed of a 1-(3-aminopropyl)-3-alkylimidazole chloride ionic liquid and an H-type 732 cation exchange resin carrier, and the structure is shown below:

Wherein, R is a C1-C4 straight-chain alkyl group.

By adopting the above technical scheme, the synthesis method of the present invention uses a solid-supported aminated ionic liquid as a catalyst, the amino group in the ionic liquid is combined with the sulfonic acid group in the carrier resin in the form of an ionic bond, and the aminated ionic liquid is grafted onto the surface of the H-type 732 cation exchange resin carrier, so that the catalyst has the advantages of both homogeneous and heterogeneous catalysts in the catalytic process. On the one hand, the carrier resin is used to adsorb the catalyst, so that the catalyst gradually releases ions during the reaction. Compared with the problem of the catalyst being separated from the carrier surface during use caused by the ordinary loading method, the solid-supported aminated ionic liquid in the technical scheme can play a catalytic role for a longer time and stably. On the other hand, after the reaction is completed, the resin and the ion catalyst adsorbed on the resin can be recovered by simple filtration. The invention can improve the phenomenon in the prior art that the liquid catalyst is partially dissolved in the solvent or the product and is difficult to separate and recover, resulting in the gradual loss of the catalyst. In addition, compared with the solid catalyst, the solid-supported amino ionic liquid has a higher solubility in the solvent and less agglomeration during use, which alleviates the problem of the reduction of the catalytic active center of the solid catalyst, so that the catalyst can continue to show high selectivity for the trimer of hexafluoropropylene oxide. By screening the carbon chain length of the 1-(3-aminopropyl)-3-alkylimidazole chloride ionic liquid, the operator found that when the carbon chain is a straight-chain alkyl of C1-C4, the catalyst has a strong selectivity for the reaction. This is because when the carbon chain is too long, a steric hindrance effect is generated, which makes it easy for the chloride ion to combine with the amino group, resulting in a decrease in the selectivity of the catalyst.

The present invention comprises the following steps:

S1: adding the immobilized amino ionic liquid catalyst and the solvent into a reaction kettle, stirring and dispersing;

S2: after adjusting the reaction temperature to keep it stable, hexafluoropropylene oxide is introduced to carry out polymerization reaction to obtain a crude hexafluoropropylene oxide trimer;

S3: After standing, the lower layer of crude product is separated and distilled to obtain pure hexafluoropropylene oxide trimer;

S4: Collect the upper catalyst and solvent mixture, and repeat steps S2 and S3.

Through the above technical scheme, when producing hexafluoropropylene oxide trimer, the present technical scheme uses a solid-supported amino ionic liquid catalyst to catalyze the polymerization of hexafluoropropylene oxide to generate hexafluoropropylene oxide trimer. Compared with the prior art, only hexafluoropropylene oxide is used as a raw material, the process is relatively simple, and the preparation and storage costs of the raw materials are lower. In addition, the liquid catalyst used in the present technical scheme is more evenly mixed with the raw materials compared with the fixed catalyst, thereby avoiding the agglomeration of the solid catalyst during the production process. At the same time, the ion concentration in the liquid catalyst is higher and the catalytic effect is stronger.

In the present invention, the solvent in step S1 is an aprotic polar solvent.

Through the above technical scheme, in the present technical scheme, 1-(3-aminopropyl)-3-alkylimidazole chloride ionic liquid and H-type 732 cation exchange resin are combined in the form of ionic bonds, so that the catalyst is grafted onto the surface of the ion exchange resin. Therefore, the use of a non-protonic polar solvent can reduce the damage to the immobilized amino ionic liquid catalyst, thereby extending the duration of the catalyst and enhancing the catalytic effect.

In the present invention, the solvent in step S1 is one or a combination of diethylene glycol dimethyl ether or tetraethylene glycol dimethyl ether.

Through the above technical solution, diethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether are both excellent non-protonic ionic solvents and have a good dissolving effect in this technical solution.

In the present invention, the solid-supported amination ionic liquid catalyst in step S1 has a solid-supported mass of 30-40%.

In the present invention, the reaction temperature in step S2 is 20-40° C., and the reaction time in step S2 is 0.5-1.5 h.

In the present invention, the molar ratio of the catalyst to hexafluoropropylene oxide in step S2 is 1:(40-100).

In the present invention, the mass ratio of the solvent to hexafluoropropylene oxide in step S2 is 1:(1-5).

The synthetic method of the present invention has the following beneficial effects:

1. In the production of hexafluoropropylene oxide trimer, the present technical solution uses a solid-supported amino ionic liquid catalyst to catalyze the polymerization of hexafluoropropylene oxide to generate hexafluoropropylene oxide trimer. Compared with the prior art, only hexafluoropropylene oxide is used as the raw material, the process is relatively simple, and the preparation and storage costs of the raw materials are lower;

2. The liquid catalyst used in the technical solution is more evenly mixed with the raw materials than the fixed catalyst, thus avoiding the agglomeration of the solid catalyst during the production process. At the same time, the ion concentration in the liquid catalyst is higher and the catalytic effect is stronger. 3. By screening the carbon chain length of 1-(3-aminopropyl)-3-alkyl imidazole chloride, when the carbon chain is a straight-chain alkyl of C1-C4, the catalyst has a strong selectivity for the reaction.

DETAILED DESCRIPTION

The present invention is further described below through specific implementation modes, but the protection scope of the present invention is not limited thereto.

Preparation of immobilized amination ionic liquid catalyst: 3-chloropropylamine hydrochloride is reacted with the corresponding N-alkyl imidazole to synthesize the amination ionic liquid, which is then immobilized on H-type 732 cation exchange resin. The synthesis steps are as follows:

1) Synthesis of amino ionic liquid: Weigh excess N-alkyl imidazole and 3-chloropropylamine hydrochloride in anhydrous ethanol at 70°C for condensation and reflux reaction for 48 hours. Distill under reduced pressure to obtain a light yellow viscous liquid, dissolve it in pure water, add excess KOH to adjust the pH to alkaline, then add an equal volume of ethanol/tetrahydrofuran mixed solution for extraction, filter, distill under reduced pressure, and vacuum dry to obtain a light yellow viscous liquid 1-(3-aminopropyl)-3-methylimidazolium chloride ionic liquid;

2) Synthesis of immobilized amino ionic liquid: 1-(3-aminopropyl)-3-alkyl imidazolium chloride ionic liquid and H-type 732 cation exchange resin containing sulfonic acid groups in an equal molar amount to 1-(3-aminopropyl)-3-alkyl imidazolium chloride are stirred in pure water at room temperature for 48 hours. The product is washed with pure water, filtered, and vacuum dried to obtain an immobilized 1-(3-aminopropyl)-3-alkyl imidazolium chloride ionic liquid catalyst. For example, the immobilized 1-(3-aminopropyl)-3-methyl imidazolium chloride ionic liquid has the following reaction route:

Embodiment 1:

200g of diethylene glycol dimethyl ether and 10.2g of solid-supported 1-(3-aminopropyl)-3-methylimidazolium chloride ionic liquid catalyst (35% solid support mass) were added to a 1L reactor purged with nitrogen under nitrogen protection, and then stirred at room temperature for 0.5h. The reaction temperature was set at 20°C and stabilized for 10min before 240g of hexafluoropropylene oxide was introduced for reaction. After the feeding was completed, the reaction was continued until the pressure in the reactor remained unchanged, and the stirring was continued for 0.5h. After the reaction was completed, the crude hexafluoropropylene oxide trimer was released from the valve at the bottom of the reactor, and the catalyst and solvent mixture on the upper layer were kept in the reactor for recycling.

The difference between Example 2-3 and Comparative Example 1-2 and Example 1 is that the molar ratio of the catalyst to hexafluoropropylene oxide in step S2 is different, as shown in the following table:

The difference between Examples 4-5 and Comparative Examples 3-4 and Example 1 is that the immobilized mass of the immobilized amination ionic liquid catalyst in step S1 is different, as shown in the following table:

The difference between Examples 6-7 and Comparative Examples 5-6 and Example 1 is that the reaction temperature in step S2 is different, as shown in the following table:

Reaction temperature (℃) Example 1 20 Example 6 30 Example 7 40 Comparative Example 4 10 Comparative Example 5 50

The difference between Comparative Example 7 and Example 1 is that different catalysts are used. The specific steps are as follows:

220g of diethylene glycol dimethyl ether and 13.7g of potassium fluoride were added to a 1L reactor purged with nitrogen under nitrogen protection, and then stirred at room temperature for 0.5h. The reaction temperature was set to 5°C and stabilized for 10min before 240g of hexafluoropropylene oxide was introduced for reaction. After the feeding was completed, the pressure in the reactor remained constant and the stirring was continued for 1h. After the reaction was completed, the reaction was allowed to stand for 0.5h, and the crude hexafluoropropylene oxide trimer in the lower layer was released from the valve at the bottom of the reactor.

The difference between Example 8 and Example 1 is that the catalyst in Example 7 is reused three times, and the difference between Comparative Example 8 and Comparative Example 7 is that the catalyst is reused three times.

Detection Methods

Liquid chromatography was used to perform liquid phase analysis on the products of each embodiment and comparative example to obtain the purity and yield of each product.

The test results are shown in the following table:

Conclusion: It can be seen from the data of Examples 1-3 and Comparative Examples 1-2 in the above table that when the technical scheme produces hexafluoropropylene oxide trimer, the molar ratio of the catalyst to hexafluoropropylene oxide has a good catalytic efficiency when it is 1: (40-100). When the molar ratio of the catalyst to hexafluoropropylene oxide is less than 1: 40, the yield and purity of the hexafluoropropylene oxide trimer are greatly reduced. When the molar ratio of the catalyst to hexafluoropropylene oxide is greater than 1: 100, the yield and purity of the hexafluoropropylene oxide trimer are slightly improved, and it is not meaningful to continue to increase the amount of the catalyst.

Conclusion: It can be seen from the data of Examples 1, 4, 5 and Comparative Examples 3 and 4 in the above table that when the technical scheme produces hexafluoropropylene oxide trimer, the solid-loaded mass of the solid-loaded 1-(3-aminopropyl)-3-methylimidazolium chloride ionic liquid catalyst has a good catalytic efficiency when it is 30-40%. When the solid-loaded mass of the solid-loaded 1-(3-aminopropyl)-3-methylimidazolium chloride ionic liquid catalyst is less than 30%, the yield and purity of the hexafluoropropylene oxide trimer are greatly reduced. When the solid-loaded mass of the solid-loaded 1-(3-aminopropyl)-3-methylimidazolium chloride ionic liquid catalyst is greater than 40%, the yield and purity of the hexafluoropropylene oxide trimer are slightly improved, and it is not meaningful to continue to increase the solid-loaded mass.

Conclusion: It can be seen from the data of Examples 1, 6, 7 and Comparative Examples 5 and 6 in the above table that when the technical solution produces hexafluoropropylene oxide trimer, the reaction temperature in step S2 has a good yield and product purity at 20-40°C. When the reaction temperature in step S2 is less than 20°C, the yield and purity of the hexafluoropropylene oxide trimer are not much different from those at 20°C, but the reaction rate is low at low temperatures. At the same time, in order to maintain a reaction temperature of 10°C, additional energy is required for refrigeration, and the production cost is large, which does not conform to the current green production environment. When the reaction temperature in step S2 is greater than 40°C, the yield and purity of the hexafluoropropylene oxide trimer are greatly reduced. This is because at a higher temperature, not only the polymerization difficulty of hexafluoropropylene oxide increases, but the product hexafluoropropylene oxide trimer also has a certain degree of decomposition, so it is difficult to continue to increase the reaction temperature.

Conclusion: It can be seen from the data of Example 1 and Comparative Example 7 in the above table that the yield and purity of hexafluoropropylene oxide produced by the present technical scheme are both high. Since a liquid catalyst is used in the present technical scheme, it is more evenly mixed with the raw material than a fixed catalyst, thereby avoiding the agglomeration of the solid catalyst during the production process. At the same time, the ion concentration in the liquid catalyst is higher and the catalytic effect is stronger, so that the final product has a higher purity and yield.

Conclusion: It can be seen from the data of Example 8 and Comparative Example 7 in the above table that the solid-supported 1-(3-aminopropyl)-3-methylimidazolium chloride ionic liquid catalyst used in the present technical solution has a good reuse effect and can still maintain a high catalytic effect after repeated use, while the traditional solid catalyst has agglomeration phenomenon after repeated use, which greatly reduces the catalytic effect.

The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims (8)

1. A method for synthesizing hexafluoropropylene oxide trimer is characterized in that: under the action of an immobilized amination ionic liquid catalyst, hexafluoropropylene oxide is subjected to polymerization reaction in a solvent to obtain hexafluoropropylene oxide trimer, wherein the immobilized amination ionic liquid catalyst consists of 1- (3-aminopropyl) -3-alkyl imidazole chloride ionic liquid and an H-type 732 cation exchange resin carrier, and the structure is as follows:

Wherein R is C ₁～C₄ straight-chain alkyl.

2. The method for synthesizing hexafluoropropylene oxide trimer according to claim 1, characterized in that: the synthesis method comprises the following steps:

s1: adding the immobilized amination ionic liquid catalyst and the solvent into a reaction kettle, and stirring and dispersing;

S2: after the reaction temperature is regulated to be kept stable, introducing hexafluoropropylene oxide for polymerization reaction to obtain a crude product of hexafluoropropylene oxide trimer;

s3: standing, separating out a lower crude product, and rectifying to obtain a pure hexafluoroepoxypropyl trimer product;

s4: and (3) collecting the upper catalyst and solvent mixture, and repeating the steps S2 and S3.

3. The method for synthesizing hexafluoropropylene oxide trimer as set forth in claim 2, wherein: the solvent in the step S1 is an aprotic polar solvent.

4. The method for synthesizing hexafluoropropylene oxide trimer as set forth in claim 2, wherein: the solvent in the step S1 is one or a combination of a plurality of diethylene glycol dimethyl ether or tetraethylene glycol dimethyl ether.

5. The method for synthesizing hexafluoropropylene oxide trimer as set forth in claim 2, wherein: the solid-supported mass of the solid-supported amination ionic liquid catalyst in the step S1 is 30-40%.

6. The method for synthesizing hexafluoropropylene oxide trimer as set forth in claim 2, wherein: the reaction temperature in the step S2 is 20-40 ℃, and the reaction time in the step S2 is 0.5-1.5 h.

7. The method for synthesizing hexafluoropropylene oxide trimer as set forth in claim 2, wherein: the molar ratio of the catalyst to hexafluoropropylene oxide in the step S2 is 1: (40-100).

8. The method for synthesizing hexafluoropropylene oxide trimer as set forth in claim 2, wherein: the mass ratio of the solvent to hexafluoropropylene oxide in the step S2 is 1 (1-5).