CN111333501B - Preparation method of fluorine-containing carboxylic acid - Google Patents
Preparation method of fluorine-containing carboxylic acid Download PDFInfo
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- C07C51/083—Preparation of carboxylic acids or their salts, halides or anhydrides from carboxylic acid anhydrides
- C07C51/087—Preparation of carboxylic acids or their salts, halides or anhydrides from carboxylic acid anhydrides by hydrolysis
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- C07C51/16—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
- C07C51/31—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation of cyclic compounds with ring-splitting
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- C07C51/41—Preparation of salts of carboxylic acids
- C07C51/412—Preparation of salts of carboxylic acids by conversion of the acids, their salts, esters or anhydrides with the same carboxylic acid part
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- C07C51/60—Preparation of carboxylic acid halides by conversion of carboxylic acids or their anhydrides or esters, lactones, salts into halides with the same carboxylic acid part
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Abstract
The invention discloses a preparation method of fluorine-containing carboxylic acid, which takes fluorine-containing carboxylate as a raw material, obtains a corresponding mixture of fluorine-containing acyl chloride and fluorine-containing acid anhydride by reacting with an acyl chlorination reagent, and prepares the high-purity fluorine-containing carboxylic acid after hydrolyzing and drying the mixture of the fluorine-containing acyl chloride and the fluorine-containing acid anhydride. The method is suitable for the post-treatment of preparing fluorine-containing carboxylic acid by the oxidation method of fluorine-containing olefin (monoolefin, diolefine, cycloolefine and the like), replaces the traditional strong acid acidification and ether continuous extraction process, and is more convenient and applicable; can also be used for recovering and purifying the fluorine-containing carboxylate emulsifier. The purity of the fluorine-containing carboxylic acid prepared by the method can reach more than 98 percent.
Description
Technical Field
The invention relates to the technical field of fluorine-containing carboxylic acid, and particularly relates to a preparation method of fluorine-containing carboxylic acid.
Background
Fluorine-containing carboxylic acid is a widely used intermediate from which a variety of fluorine-containing fine chemicals can be derived or used as an emulsifier for the polymerization of fluorine-containing monomers. The fluorine-containing carboxylic acid can be prepared from corresponding hydrogen-containing acid, anhydride, ester, acyl chloride or acyl fluoride by an electrochemical fluorination method or a hydrogen-containing precursor by a fluorine gas fluorination method, but both methods have the problems of extremely low yield and complex and difficult product separation; fluorocarboxylic acids can also be prepared by the oxidation of fluoroolefins (mono-olefins, di-olefins, cyclic olefins, etc.).
In the prior art, the fluorine-containing carboxylic acid is prepared by an oxidation method, and concentrated sulfuric acid or concentrated hydrochloric acid is adopted for acidification and then distillation or ether continuous extraction after oxidation treatment. See related patents US2438485, US 243146, US2502478, US4751027, etc. and related literature (J Am Chem Soc, 1945, 67, 1235-1237J Am Chem Soc 1947, 2, 281-283J Am Chem Soc, 1951, 73, 1103-1104J Am Chem Soc, 1959, 81, 2678-2680 russ Chem Bull 1962, 11, 2049-2051J fluoride Chem, 1981-82, 19, 35-42 synth commu, 1983, 13, 81-86J fluoride Chem, 1990, 48, 29-35J fluoride Chem, 1990, 48, 77-84, etc..
As for long-carbon-chain fluorine-containing carboxylic acid and fluorine-containing dicarboxylic acid with more than 5 carbon atoms, because of the high acidity, a large amount of concentrated sulfuric acid or concentrated hydrochloric acid is required to be added in the actual operation, a long-time heating operation is required, and the reflux extraction is carried out for a long time by using ether, even if the satisfactory yield cannot be achieved, the main reason is that the acidification is incomplete or the extraction is incomplete.
According to the regulations of hazardous chemical safety regulations and easy-to-prepare-poison chemical management regulations, concentrated sulfuric acid, concentrated hydrochloric acid, ether and the like are all hazardous chemicals, belong to easy-to-prepare-poison chemicals and are regulated by the police department. Diethyl ether is also very volatile and flammable, has a strong anesthetic effect on human bodies, and has high danger in the extraction and distillation processes. In addition, ether can be oxidized into peroxide under the action of air, and has the danger of causing strong explosion when being heated, thereby meeting the requirement of explosion prevention on equipment. Therefore, extraction with diethyl ether is not the most desirable option for safety reasons. Especially in industrial production, the use of large amounts of concentrated sulfuric acid, concentrated hydrochloric acid and diethyl ether has great environmental risks and safety risks.
Fluorocarboxylic acids and salts thereof have good surface activity and are used in large amounts as emulsifiers in the production of fluoropolymers. In view of the high cost of these fluorine-containing carboxylic acids and salts thereof and the adverse effect on the environment, it is desirable to recover, purify and reuse as much as possible. In the prior art, the patent and literature disclose methods for recycling fluorine-containing carboxylate emulsifiers, such as vacuum concentration method, metal salt conversion method, foam separation method and ion exchange resin method, and refer to US4609497, US4282162, US5312935 and US6281374.
In reality, the recovered fluorine-containing carboxylate solid or concentrated solution has impurities with different contents, the purity is difficult to meet the requirement of direct reuse, and no exception is that strong acid is required to be added to carry out acidification treatment on the fluorine-containing carboxylate aqueous solution, and other chemical or physical means are used for achieving the required purity. It has been described that fluorocarboxylic acids are highly acidic and difficult to acidify completely, and thus the current recovery techniques are not satisfactory.
In conclusion, the existing oxidation post-treatment method for preparing fluorine-containing carboxylic acid and the recycling of the fluorine-containing carboxylate emulsifier have the defects of low yield and purity, complex operation and the like, and the use of a large amount of inorganic acid such as concentrated sulfuric acid and the like has great environmental risk and potential safety hazard. Therefore, finding a synthetic route of fluorine-containing carboxylic acid which is simple to operate, economic and feasible, improves yield and purity, and is suitable for industrial amplification production is still a great challenge.
Disclosure of Invention
The invention aims to provide a novel preparation method of fluorine-containing carboxylic acid aiming at the problems in the prior art in the preparation process of fluorine-containing carboxylic acid. The method comprises the steps of taking fluorine-containing carboxylate as a raw material, reacting with an acyl chlorination reagent to obtain a corresponding mixture of fluorine-containing acyl chloride and fluorine-containing acid anhydride, and hydrolyzing and drying the mixture to obtain fluorine-containing carboxylic acid; the method can obtain the high-purity fluorine-containing carboxylic acid without strong acid acidification and ether continuous extraction operation, has simpler preparation process, and is particularly suitable for industrial scale production of the fluorine-containing carboxylic acid.
In order to achieve the purpose of the invention, the specific technical scheme is as follows:
the preparation method of fluorine-containing carboxylic acid comprises the following steps of carrying out acyl chlorination reaction on solid fluorine-containing carboxylate and acyl chlorination reagent to generate a corresponding mixture of fluorine-containing acyl chloride and fluorine-containing acid anhydride; then distilling out fluorine-containing acyl chloride and acid anhydride, hydrolyzing and drying to obtain the fluorine-containing carboxylic acid.
The fluorine-containing carboxylate comprises fluorine-containing carboxylate existing in the form of emulsifier, fluorine-containing carboxylate generated in the process of preparing fluorine-containing carboxylic acid by using a fluorine-containing olefin oxidation method, and fluorine-containing carboxylate generated by the reaction of fluorine-containing carboxylic acid. When the fluorine-containing carboxylate emulsifier is adopted, the solution of the fluorine-containing carboxylate emulsifier needs to be concentrated and fully dried to obtain the solid fluorine-containing carboxylate. When purifying low-purity commercial fluorine-containing carboxylic acid, the fluorine-containing carboxylic acid is required to react with alkali liquor such as KOH, naOH, ammonia water and the like, and then the solid fluorine-containing carboxylate is obtained after drying.
The fluorine-containing carboxylate generated in the preparation of the fluorine-containing carboxylic acid by the oxidation method of the fluorine-containing olefin can be prepared by the following method: after the fluorine-containing olefin (monoolefin, diolefine, cycloolefine and the like) is completely oxidized by potassium permanganate, sodium permanganate, potassium dichromate, sodium dichromate and other strong oxidizing agents, excessive oxidizing agents are treated by sodium thiosulfate, sulfur dioxide, oxalic acid and other reducing agents, the oxidation product is filtered and washed to remove filter residues, the filtrate and the washing liquor are combined, a small amount of strong base such as KOH, naOH and the like is added to adjust the pH value to be alkaline, and the solid mixed salt containing fluorine-containing carboxylate is obtained after full drying.
The fluorine-containing carboxylate may be a fluorine-containing dicarboxylic acid salt having a structure represented by the general formula (I),
MOOC-(CR 1 R 2 ) a -(CF 2 ) n -(CR 3 R 4 ) b -COOM（I）
wherein R is 1 、R 2 、R 3 、R 4 Is a hydrogen atom, a fluorine atom, a chlorine atom or C 1-3 Alkyl groups, which may be the same or different; a and b are integers from 0 to 3, n is an integer from 0 to 5, and a + b + n is more than or equal to 2 and less than or equal to 8; when n is 0, R 1 、R 2 、R 3 、R 4 At least one is a fluorine atom; m is a monovalent alkali metal ion or ammonium ion.
Thus, when the fluorine-containing carboxylic acid salt is a fluorine-containing dicarboxylic acid salt, the fluorine-containing dicarboxylic acid prepared has the formula HOOC- (CR) 1 R 2 ) a -(CF 2 ) n -(CR 3 R 4 ) b -COOH, wherein R 1 、R 2 、R 3 、R 4 A, b and n are as defined above.
The fluorine-containing carboxylate can also be fluorine-containing monocarboxylate which has a structure shown as a general formula (II),
X-R f -COOM（II）
wherein X is a hydrogen atom, a fluorine atom or a chlorine atom; r f Is a linear or branched fluoroalkylene or oxyfluoroalkylene group having 4 to 20 carbon atoms; m is a monovalent alkali metal ion or ammonium ion.
When the fluorine-containing carboxylate is fluorine-containing monocarboxylate, the prepared fluorine-containing monocarboxylate has a general formula X-R f -COOH, X and R f The definition is the same as above.
In general, in the process of preparing fluorine-containing carboxylic acid by oxidation of fluorine-containing olefin (monoolefin, diolefin, cycloolefine, etc.), the used oxidant is potassium permanganate, sodium permanganate, potassium dichromate, sodium dichromate, etc., after the reaction is finished, the excess oxidant is treated by reducing agents such as sodium thiosulfate, sulfur dioxide, oxalic acid, etc., then the oxidation product is filtered, the filter residue is washed, and the filtrate and the washing liquid are combined for subsequent treatment, which is disclosed in the field. The method of the invention is used for replacing the original post-treatment method of acidification and extraction, filtrate and washing liquor are required to be combined, then a small amount of strong base such as KOH, naOH and the like is added to adjust the pH value to be alkaline, the oxidation products are ensured to exist in the form of fluorine-containing carboxylate, and the mixed salt containing the fluorine-containing carboxylate is obtained after drying, and can be used for the next step of acyl chlorination reaction without further separation.
The acyl chlorination reagent is at least one of thionyl chloride, phosphorus trichloride, phosphorus pentachloride, triphosgene, diphosgene, phosgene and oxalyl chloride. Sulfoxide chloride, triphosgene and oxalyl chloride are particularly preferred for ease of subsequent processing.
The equivalent ratio of the acyl chlorination reagent to the fluorine-containing carboxylate is 0.5-3.6, namely the amounts of thionyl chloride, phosphorus pentachloride, phosgene and oxalyl chloride used in 1 mole of fluorine-containing monocarboxylate are 0.6-3.6 moles, the amount of diphosgene is 0.3-1.8 moles, and the amounts of phosphorus trichloride and triphosgene are 0.2-1.2 moles; the amounts of thionyl chloride, phosphorus pentachloride, phosgene and oxalyl chloride used as acyl chloride reagents for 1 mole of fluorine-containing dicarboxylic acid salt are 1.2 to 7.2 moles, diphosgene is 0.6 to 3.6 moles, and phosphorus trichloride and triphosgene are 0.4 to 2.4 moles.
The temperature of the acyl chlorination reaction is 10-150 ℃, and more preferably 30-100 ℃.
The acyl chlorination reaction of the invention can be added with organic base as catalyst, and the dosage of the catalyst is less than or equal to 3 percent of the solid mass of the fluorine-containing carboxylate. The organic base catalyst is used for better promoting the reaction and reducing the dosage of the acyl chlorination reagent. The organic base is preferably one or a combination of any two or more of imidazole, N-methylimidazole, N-dimethylformamide, N-methylpyrrolidone, pyridine, picoline and triethylamine.
The acyl chlorination reaction can also add a phase transfer catalyst as a reaction auxiliary agent, and the dosage of the phase transfer catalyst is less than or equal to 5 percent of the solid mass of the fluorine-containing carboxylate.
The reaction auxiliary used in the present invention may be one of or a combination of any two or more of crown ethers that can be used as a phase transfer catalyst, quaternary phosphonium salts that can be used as a phase transfer catalyst, and quaternary ammonium salts that can be used as a phase transfer catalyst. Useful crown ethers include 18-crown-6, 15-crown-5, 12-crown-4 or derivatives thereof such as dibenzo-18-crown-6, dicyclohexyl-18-crown-6 and dibenzo-24-crown-8, and benzo 12-crown-4, and the like. Useful quaternary ammonium salts include benzyltriethylammonium chloride, methyltrioctylammonium chloride, tetra-n-butylammonium bromide, tetra-n-butylammonium bisulfate, and the like. Useful quaternary phosphonium salts include tetra-n-butylphosphonium chloride, tetra-n-butylphosphonium bromide, tetraphenylphosphonium chloride, triphenylmethylphosphonium bromide, triphenylmethylphosphonium chloride, benzyltriphenylphosphonium chloride, and the like.
The acyl chlorination reaction of the invention can be added with an organic solvent as a reaction medium, and the dosage of the organic solvent is less than or equal to 300 percent of the solid mass of the fluorine-containing carboxylate. The organic solvent is added to better disperse the fluorine-containing carboxylate, thereby facilitating heat transfer and mass transfer. The organic solvent is one or the combination of more than two of dichloromethane, chloroform, benzene, toluene, xylene, ethylbenzene and chlorobenzene.
The acyl chloride reaction product prepared by the method is usually a mixture of fluorine-containing acyl chloride and fluorine-containing acid anhydride, the proportion of the mixture is related to the addition amount of the acyl chloride reagent, the acyl chloride reagent is added in a large amount, the proportion of the acyl chloride is large, and the proportion of the acid anhydride is large otherwise. Both the fluorine-containing acyl chloride and the fluorine-containing anhydride can be hydrolyzed into fluorine-containing carboxylic acid, and the yield and the purity of the target product are not influenced. In order to save cost, the dosage of acyl chlorination reagent should be reduced as much as possible. The optimum amount of acid chloride reagent can be determined experimentally for different fluorine-containing carboxylic acid salts.
After the acyl chlorination reaction is finished, the solvent and the product can be separated from the residual inorganic salt by conventional normal pressure distillation or reduced pressure distillation; and after the hydrolysis is finished, drying the water phase to obtain solid fluorine-containing carboxylic acid, and recycling the organic phase by using the prior art.
The invention has the following beneficial technical effects:
1. the invention solves the defects in the prior art and provides a novel preparation method of fluorine-containing carboxylic acid. The method takes fluorine-containing carboxylate as a raw material, obtains a corresponding mixture of fluorine-containing acyl chloride and fluorine-containing acid anhydride by reacting with an acyl chlorination reagent, and prepares the high-purity fluorine-containing carboxylic acid after hydrolyzing and drying the mixture. The method can prepare fluorine-containing carboxylic acid with the purity of more than or equal to 98 percent only by simple equipment and process conditions.
2. The method is particularly suitable for the post-treatment of preparing fluorine-containing carboxylic acid by the oxidation method of fluorine-containing olefin (monoolefin, diolefine, cycloolefine and the like), replaces the traditional strong acid acidification and ether continuous extraction process, can improve the yield and the product purity, is more convenient and applicable, and has no environmental risk and potential safety hazard
3. The method is also suitable for recovering and purifying the fluorine-containing carboxylate emulsifier, improves the recovery rate and the purity, achieves the aim of recycling, reduces the cost and protects the environment.
4. The method can also be used for further purification treatment of low-purity fluorine-containing carboxylic acid, and is simple and practical.
The invention is specifically described and further illustrated by the following examples.
Detailed Description
Example 1
240g of 96.6 percent potassium 2, 2-difluorosuccinate solid and 220g of thionyl chloride are reacted until no tail gas is generated, products are distilled out (the contents of acyl chloride and anhydride are respectively 87.4 percent and 11.8 percent by GC analysis), and 148g of 2, 2-difluorosuccinic acid is obtained after hydrolysis and drying, the purity is 98.5 percent, and the yield is 93.9 percent.
Example 2
320g of tridecafluoroheptanoic acid sodium salt solid with 95.4 percent of content is reacted with 220g of thionyl chloride until no tail gas is generated, products are evaporated (the content of acyl chloride and anhydride is respectively 96.3 percent and 1.5 percent by GC analysis), and 266g of tridecafluoroheptanoic acid is obtained after hydrolysis and drying, the purity is 98.8 percent, and the yield is 91.3 percent.
Example 3
1608g of potassium permanganate oxidation product of 1, 2-dichlorotetrafluorocyclobutene having a content of 93.4% were filtered and washed twice, the filtrate and the washings were combined, and 155g of potassium hydroxide was added to adjust the pH to 9. The solution was dried to obtain 2954g of mixed salt, mainly containing potassium tetrafluorosuccinate, excess potassium hydroxide and potassium chloride.
The mixed salt was charged into a 5L three-necked flask equipped with a mechanical stirring, constant pressure dropping funnel and a thermometer tube together with 3100g of chloroform. 1802g of thionyl chloride (molar ratio to the theoretical value of the target carboxylic acid: about 2). And tail gas is absorbed by alkali liquor. After the addition is completed for 3.5h, the reaction is continued for 10min to finish the reaction. The products distilled at 90 ℃ under atmospheric pressure were collected by an ice water cold trap and the respective contents of tetrafluorosuccinyl chloride and tetrafluorosuccinic anhydride were 91.1% and 6.7% by GC analysis.
Adding 1000ml of deionized water into a 2L three-neck flask with a mechanical stirring device, a constant pressure dropping funnel and a thermometer guide pipe, dripping the acyl chloride product within 2 hours under stirring, keeping the internal temperature below 30 ℃, continuing stirring for 0.5 hour after dripping, and absorbing tail gas with alkali liquor. And drying the hydrolysate under reduced pressure by using a rotary evaporator to obtain 1236g of dried tetrafluorosuccinic acid, wherein the purity is 98.5 percent, and the total yield is 83.6 percent.
Comparative example 3
625g of 93.4 percent potassium permanganate oxidation product of 1, 2-dichlorotetrafluorocyclobutene is filtered and washed twice, the filtrate and the washing liquid are combined and added into a 5L three-neck flask with a mechanical stirring and constant pressure dropping funnel and a thermometer catheter, then 1000ml of 98 percent concentrated sulfuric acid is slowly dropped under stirring, the temperature of 50 ℃ is maintained for acidification for 18h, 1500ml of diethyl ether is added for reflux extraction for 12h, anhydrous calcium chloride is added into an organic phase after liquid separation for drying overnight, and the obtained organic layer is spin-dried after liquid separation again to obtain 431g of solid tetrafluorosuccinic acid with the purity of 92.4 percent and the total yield of 68.3 percent.
Example 4
810g of the sodium permanganate oxidation product of 1, 2-dichlorohexafluorocyclopentene having a content of 95.1% were filtered and washed twice, the filtrate and the washings were combined, and 77g of sodium hydroxide were added to adjust the pH to 9. The solution was dried to obtain 1453g of mixed salt, which mainly contained sodium hexafluoroglutarate, excess sodium hydroxide and sodium chloride.
The above mixed salt, 6g of imidazole, 10g of crown ether (18-crown-6) and 500g of methylene chloride were charged together into a 5L three-necked flask equipped with a mechanical stirring, constant pressure dropping funnel and a thermometer tube. 600g of oxalyl chloride was dropped into the flask through a constant pressure dropping funnel with stirring, and the internal temperature was controlled to be around 25 ℃. And absorbing tail gas by using alkali liquor. After the addition was completed for 2h, stirring was continued for 0.5h to complete the reaction. The product of distillation under reduced pressure (80 ℃ C.,. Ltoreq.20 mmHg) was collected by a dry ice alcohol cold trap, and the respective contents of hexafluoroglutaryl chloride and hexafluoroglutaric anhydride were 64.3% and 34.9% by GC analysis.
Adding 500ml of deionized water into a 2L three-neck flask with a mechanical stirring function, a constant pressure dropping funnel and a thermometer guide pipe, dripping the acyl chlorination product within 1 hour under stirring, keeping the internal temperature below 40 ℃, continuing stirring for 1 hour after dripping, and absorbing tail gas with alkali liquor. The hydrolyzate was dried under reduced pressure using a rotary evaporator to obtain 695g of dried hexafluoroglutaric acid, purity 98.1%, total yield 90.5%.
Example 5
The experimental procedure was similar to examples 3 and 4.
358g of mixed sodium salt obtained by oxidizing 97.2 percent decafluorocyclohexene, 2g of N-methylpyrrolidone, 3g of benzyltriphenylphosphonium chloride, 400g of chloroform and 240g of phosphorus trichloride, hydrolyzing and drying to obtain 322g of octafluoroadipic acid with the purity of 99.2 percent and the yield of 84.5 percent.
Example 6
The experimental procedure was similar to examples 3 and 4.
406g of 93.4 percent 3-trifluoromethyl perfluorocyclohexene, 4g of pyridine, 5g of tetrabutylammonium bromide, 500g of toluene and 430g of thionyl chloride are reacted to obtain an acyl chloride mixture, and the mixture is hydrolyzed and dried to obtain 351g of 3-trifluoromethyl heptafluoro adipic acid with the purity of 98.3 percent and the total yield of 83.2 percent.
Example 7
The experimental procedure was similar to examples 3 and 4.
290g of mixed potassium salt obtained by oxidizing 95.7 percent dodecafluorocycloheptene, 6g of triethylamine, 5g of methyl trioctyl ammonium chloride, 350g of chlorobenzene and 390g of triphosgene to obtain an acyl chloride mixture, and hydrolyzing and drying the acyl chloride mixture to obtain 247g of decafluoropimelic acid, wherein the purity is 98.5 percent, and the total yield is 80.4 percent.
Example 8
855g of a mixed salt containing potassium tridecafluoroheptanate, potassium hydroxide and potassium chloride (wherein potassium tridecafluoroheptanate is about 1.42mol, an oxidation product of 1H, 2H-perfluoro-1-octene) and 4g of tetra-n-butylammonium bromide were added together with 500g of dichloromethane to a 2L three-necked flask equipped with a mechanical stirring, constant pressure dropping funnel and a thermometer tube. 260g of thionyl chloride containing 0.5g of N, N-dimethylformamide was added dropwise to the flask through a constant pressure dropping funnel with stirring, and the internal temperature was controlled to about 35 ℃. And tail gas is absorbed by alkali liquor. After 1.5h of complete addition, stirring was continued for 1h to complete the reaction. The product distilled under reduced pressure (80 ℃ C.,. Ltoreq.20 mmHg) was collected by a dry ice alcohol cold trap, and the content of tridecafluoroheptanoyl chloride by GC analysis was 98.6%.
485g of tridecafluoroheptanoic acid is obtained after hydrolysis and drying, the purity is 99.3 percent, and the yield is 93.2 percent.
Example 9
The experimental procedure was similar to that of example 8.
520g of potassium nonafluorodecanoate with the content of about 96.7%, 2g of N-methylimidazole, 2g of tetra-N-butylphosphonium bromide, 400g of toluene and 320g of phosphorus pentachloride were reacted to obtain an acid chloride mixture, and after hydrolysis and drying, 457.6g of nonafluorodecanoic acid with the purity of 99.8% and the yield of 97.6% was obtained.
Example 10
The experimental procedure was similar to that of example 8.
550g of perfluorotetradecanoic acid ammonium salt with the content of about 95.7 percent, 3g of triethylamine, 3g of benzyltriethylammonium chloride, 400g of chlorobenzene and 300g of triphosgene are reacted to obtain an acyl chloride mixture, and the acyl chloride mixture is hydrolyzed and dried to obtain 491g of perfluorotetradecanoic acid with the purity of 99.3 percent and the yield of 94.8 percent.
Example 11
The experimental procedure was analogous to example 8.
An acid chloride mixture obtained by reacting 620g of perfluorooctadecanoic acid sodium salt with a content of about 93.6%, 1g of N, N-dimethylformamide, 4g of bicyclohexano-18-crown-6, 500g of chloroform and 210g of thionyl chloride was subjected to hydrolysis drying to obtain 548g of perfluorooctadecanoic acid with a purity of 99.2% and a yield of 95.9%.
Example 12
The experimental procedure was similar to that of example 8.
An acyl chloride mixture obtained by reacting 735g of perfluoroeicosanoic acid potassium salt with the content of 91.4 percent, 2g of pyridine, 2g of tetra-n-butylphosphonium chloride, 550g of ethylbenzene and 320g of thionyl chloride is hydrolyzed and dried to obtain 638g of perfluoroeicosanoic acid, the purity of which is 98.5 percent and the yield of which is 96.8 percent.
Example 13
650g of commercially available perfluorooctanoic acid having a purity of 96.5% was neutralized to alkaline with a 25% potassium hydroxide aqueous solution, and dried to obtain 713g of mixed salt.
The above mixed salt was charged into a 1L three-necked flask equipped with a mechanical stirring, a constant pressure dropping funnel and a thermometer tube. 360g of thionyl chloride mixed with 1g of N, N-dimethylformamide is slowly dripped into the flask through a constant-pressure dropping funnel, the internal temperature is controlled to be not higher than 50 ℃, stirring is started after half of dripping, and tail gas is absorbed by alkali liquor. After the addition was completed for 2.5h, stirring was continued for 1h to complete the reaction. The product distilled under reduced pressure (90 ℃ C., not more than 20 mmHg) was collected by a dry ice alcohol cold trap, and the content of perfluorooctanoyl chloride was 99.1% by GC analysis.
628g of perfluoro caprylic acid is obtained after hydrolysis and drying, the purity is 99.5 percent, and the yield is 99.6 percent.
Example 14
Commercially available hexafluoroglutaric acid with a purity of 95% was purified by the method of example 13.
253g of low-purity hexafluoroglutaric acid was neutralized to alkalinity with a 20% aqueous solution of sodium hydroxide, dried, subjected to an acylchlorination reaction, hydrolyzed and dried to obtain 236g of hexafluoroglutaric acid, the purity of which was 99.2%, and the yield of which was 97.5%.
Example 15
Recovering the emulsifier to form a concentrate (wherein CF is present) 3 CF 2 CF 2 OCF(CF 3 )COONH 4 About 24% content, with minor amounts of buffer and ammonium sulfate) 2704g were oven dried to obtain 680g of solid.
340g of the above solid was taken in a three-necked flask equipped with a mechanical stirring, constant pressure dropping funnel and a thermometer tube together with 95g of triphosgene and 250g of xylene. A mixture of 1g of pyridine, 2g of triethylamine and 50g of xylene was dropped into the flask via a constant pressure dropping funnel while stirring, and the internal temperature was controlled to about 50 ℃. And tail gas is absorbed by alkali liquor. After 1h of complete addition, stirring was continued for 1.5h to complete the reaction. Collecting the product distilled under reduced pressure (80 deg.C, 20 mmHg) with dry ice alcohol cold trap, and GC analyzing CF 3 CF 2 CF 2 OCF(CF 3 ) The COCl content was 97.4%.
Adding 200ml deionized water into a 2L three-neck flask with mechanical stirring, constant pressure dropping funnel and thermometer guide tube, dripping the acyl chloride product within 1h under stirring, maintaining the internal temperature below 50 ℃, continuing stirring for 0.5h after dripping, and absorbing tail gas with alkali liquor. Drying the hydrolysate under reduced pressure with a rotary evaporator to obtain dry CF 3 CF 2 CF 2 OCF(CF 3 ) 304g of COOH in total, the purity is 99.7 percent, and the recovery rate is 98.2 percent.
Comparative example 15
Dissolving 340g of the solid in example 15 in 200g of water, dropwise adding 600ml of 98% concentrated sulfuric acid while stirring, maintaining the temperature at 50 ℃, acidifying for 12h, adding 1000ml of ether, refluxing and extracting for 10h, adding anhydrous magnesium sulfate into the organic phase after liquid separation, drying overnight, separating the organic layer again, and rotating the obtained organic layerDry to obtain solid CF 3 CF 2 CF 2 OCF(CF 3 ) The COOH content was 284g, the purity was 94.2%, and the recovery was 86.7%.
Example 16
Concentrating the emulsifier with 94% content, drying, and concentrating to obtain solid salt of potassium perfluoro-2, 5,8, 11-tetramethyl-3, 6,9, 12-tetraoxapentadecacarboxylate (molecular formula CF) 3 CF 2 CF 2 O(CF(CF 3 )CF 2 ) 3 OCF(CF 3 ) COOK) 352g by a similar operation to that in example 14, 312g of a carboxylic acid was recovered with a purity of 99.1% and a recovery of 97.8%.
Claims (7)
1. A method for preparing fluorine-containing carboxylic acid is characterized in that: the method comprises the steps of carrying out acyl chlorination reaction on solid fluorine-containing carboxylate and an acyl chlorination reagent to generate a corresponding mixture of fluorine-containing acyl chloride and fluorine-containing acid anhydride; then distilling out fluorine-containing acyl chloride and acid anhydride, hydrolyzing and drying to obtain fluorine-containing carboxylic acid,
the fluorine-containing carboxylate comprises fluorine-containing carboxylate existing in the form of emulsifier, fluorine-containing carboxylate generated in the preparation of fluorine-containing carboxylic acid by a fluorine-containing olefin oxidation method, fluorine-containing carboxylate generated by the reaction of fluorine-containing carboxylic acid,
the fluorine-containing carboxylate has the following general formula:
MOOC-(CR 1 R 2 )a-(CF 2 )n-(CR 3 R 4 )b-COOM （I）
wherein R is 1 、R 2 、R 3 、R 4 Is a hydrogen atom, a fluorine atom, a chlorine atom or C 1-3 Alkyl groups, which may be the same or different; a and b are integers from 0 to 3, n is an integer from 0 to 5, and a + b + n is more than or equal to 2 and less than or equal to 8; when n is 0, R 1 、R 2 、R 3 、R 4 At least one is a fluorine atom; m is a monovalent alkali metal ion or ammonium ion,
alternatively, the fluorine-containing carboxylic acid salt has the general formula:
X-R f -COOM （II）
wherein X is a hydrogen atom, a fluorine atom or a chlorine atom; r f Is a linear or branched fluoroalkylene or oxyfluoroalkylene radical having from 4 to 20 carbon atoms(ii) a M is a monovalent alkali metal ion or ammonium ion.
2. The method for producing a fluorocarboxylic acid according to claim 1, wherein: the acyl chlorination reagent is at least one of thionyl chloride, phosphorus trichloride, phosphorus pentachloride, triphosgene, diphosgene, phosgene and oxalyl chloride.
3. The method for producing a fluorocarboxylic acid according to claim 1, wherein: the equivalent ratio of the acyl chlorination reagent to the solid fluorine-containing carboxylate is 0.5-3.5.
4. The method according to claim 1, wherein: the temperature of the acyl chlorination reaction is 10-150 ℃.
5. The method for producing a fluorocarboxylic acid according to claim 1, wherein: an organic base is also added during the acyl chlorination reaction, and the addition amount of the organic base is less than or equal to 3% of the mass of the solid fluorine-containing carboxylate; the organic base is one or the combination of more than two of imidazole, N-methylimidazole, N-dimethylformamide, N-methylpyrrolidone, pyridine, picoline and triethylamine.
6. The method according to claim 1, wherein: a phase transfer catalyst is also added during the acyl chlorination reaction, and the addition amount of the phase transfer catalyst is less than or equal to 5 percent of the mass of the solid fluorine-containing carboxylate; the phase transfer catalyst is one or the combination of any two or more of crown ether, quaternary phosphonium salt and quaternary ammonium salt which can be used as the phase transfer catalyst.
7. The method according to claim 1, wherein: during the acyl chlorination reaction, an organic solvent is also added, and the adding amount of the organic solvent is less than or equal to 300% of the mass of the solid fluorine-containing carboxylate; the organic solvent is one or the combination of more than two of dichloromethane, chloroform, benzene, toluene, xylene, ethylbenzene and chlorobenzene.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3697564A (en) * | 1967-04-25 | 1972-10-10 | Allied Chem | Fluorocarbon acids and derivatives |
| CN1165807A (en) * | 1997-06-11 | 1997-11-26 | 中国科学院上海有机化学研究所 | Absolute trifluoro acetate and absolute trifluoro acetic acid prepn. |
| CN101774902A (en) * | 2010-01-13 | 2010-07-14 | 苏州大学 | Preparation method of polyfluoro aliphatic carboxylic acid |
| CN106831388A (en) * | 2017-01-18 | 2017-06-13 | 济南齐氟新材料技术有限公司 | A kind of preparation method of perfluoro-heptanoic acid |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3697564A (en) * | 1967-04-25 | 1972-10-10 | Allied Chem | Fluorocarbon acids and derivatives |
| CN1165807A (en) * | 1997-06-11 | 1997-11-26 | 中国科学院上海有机化学研究所 | Absolute trifluoro acetate and absolute trifluoro acetic acid prepn. |
| CN101774902A (en) * | 2010-01-13 | 2010-07-14 | 苏州大学 | Preparation method of polyfluoro aliphatic carboxylic acid |
| CN106831388A (en) * | 2017-01-18 | 2017-06-13 | 济南齐氟新材料技术有限公司 | A kind of preparation method of perfluoro-heptanoic acid |
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