CN118791375A

CN118791375A - Continuous method, equipment and product for preparing fluorine-containing carboxylic acid

Info

Publication number: CN118791375A
Application number: CN202410783833.3A
Authority: CN
Inventors: 李纯婷; 缪里然; 李志新; 范志忠
Original assignee: Shanghai Huayi Sanaifu New Material Co ltd; Changshu 3f Zhonghao New Chemical Materials Co ltd
Current assignee: Shanghai Huayi Sanaifu New Material Co ltd; Changshu 3f Zhonghao New Chemical Materials Co ltd
Priority date: 2024-06-18
Filing date: 2024-06-18
Publication date: 2024-10-18

Abstract

The present application provides a continuous process for preparing a fluorocarboxylic acid, which comprises: step A: continuously inputting a reaction raw material, a fluorinating agent, a solvent and a catalyst into a synthesis reactor, so that the raw material to be fluorinated and the fluorinating agent react in the synthesis reactor to generate fluorine-containing carboxylic ester, and simultaneously, continuously flowing out a crude product stream containing the fluorine-containing carboxylic ester from the synthesis reactor; and (B) step (B): separating and purifying the product stream to obtain a purified product stream; step C: hydrolyzing the purified product stream to obtain a hydrolyzed product stream comprising the fluorocarboxylic acid and/or salt thereof; step D: acidifying the hydrolysis product stream to obtain a crude fluorocarboxylic acid; and E, step: the crude product was purified. The application also provides a fluorine-containing carboxylic acid product prepared by the method and a reaction device for implementing the method. The method is carried out in a continuous mode in the whole process, the process is stable, high automation, low energy consumption, high production capacity and high reliability can be realized, and the fluorine-containing carboxylic acid product can be well used as a substitute of the perfluoro caprylic acid with biological toxicity.

Description

Continuous method, equipment and product for preparing fluorine-containing carboxylic acid

Technical Field

The present application relates to the field of chemical industry and more particularly to a process for preparing a fluorocarboxylic acid in a continuous manner, a fluorocarboxylic acid product prepared by the process, and an apparatus for carrying out the process.

Background

The fluorine-containing carboxylic acid is used as an important polymerization auxiliary agent, can effectively reduce the surface tension of aqueous solution and plays an important role in stabilizing emulsion particles. Currently, in various industrial synthesis and industrial modification processes, fluorocarboxylic acids are commonly used as polymerization aids (e.g., surfactants or emulsifiers), and among them, perfluorooctanoic acid is the most excellent and widely used, but perfluorooctanoic acid is a compound with a great potential risk. In particular, perfluorooctanoic acid is listed as a class 2B carcinogen by the world health organization international cancer research institute, which has potential for persistence, bioaccumulation and toxicity, which must remain in large quantities in the final manufactured polymeric product as well as in process waste if it is used on a large scale as a polymerization aid in various industrial applications. The process waste is environmentally polluting and the residual perfluorooctanoic acid contained in the waste and industrial products is likely to be ingested into the human body. Once the perfluoro caprylic acid enters the human body, serious and irreversible damage is caused to the human health. Thus, many countries and regions have been out of the control of perfluorooctanoic acid and its derivatives. It would therefore be highly desirable in the art to be able to develop a fluoroalkyl carboxylic acid product as a replacement for perfluorooctanoic acid, which should also have the various properties of perfluorooctanoic acid, but which is significantly less carcinogenic than perfluorooctanoic acid.

In addition, the existing synthesis and separation methods of fluorine-containing organic compounds (especially fluorine-containing carboxylic acids) are usually carried out in a stepwise and intermittent manner, and have the advantages of low automation degree, more manual operation, long time period, poor safety and poor reliability. In addition, the prior art requires a dispersing process during the synthesis of fluorine-containing organic compounds such as fluorine-containing carboxylic acids, which can produce wastewater containing a large amount of fluorine-containing organic compounds, and requires further purification of the wastewater twice or more in order to meet the related environmental requirements and to improve recovery rate, which is cumbersome and redundant in process steps, and significantly increases synthesis cost.

In order to solve the above problems, a great deal of research and development costs and efforts have been put into research institutions and enterprises in the related art to variously improve and optimize the perfluorooctanoic acid substitutes and the synthesis process of fluorine-containing organic compounds, but the technological progress achieved so far has been still very limited.

The present inventors have made intensive studies with respect to the above problems, unexpectedly developed a synthesis method which can be performed in a continuous manner, can be performed at a high automation level, has low energy consumption, is suitable for industrial continuous production, and can realize stable process, low energy consumption, high productivity and high reliability, and the fluorine-containing carboxylic acid product synthesized by the present application has a degradable structure, no bioaccumulation and toxicity, has excellent surface activity, and can perfectly replace the carcinogenic substance perfluorooctanoic acid for use as a polymerization aid.

Disclosure of Invention

In a first aspect the present application provides a continuous process for the preparation of a fluorocarboxylic acid, which process comprises:

Step A: continuously inputting the reaction raw material, the fluorinating agent, the solvent and the catalyst into the synthesis reactor 2, so that the reaction raw material to be fluorinated and the fluorinating agent react in the synthesis reactor 2 to generate fluorine-containing carboxylic acid ester, and simultaneously, continuously flowing out a crude product stream f containing the fluorine-containing carboxylic acid ester from the synthesis reactor 2;

and (B) step (B): separating and purifying the product stream f to obtain a purified product stream m;

Step C: hydrolyzing the purified product stream m to obtain a hydrolysis product stream s, wherein the hydrolysis product stream s contains fluorine-containing carboxylic acid and/or salt thereof;

step D: acidifying the hydrolysis product stream q to obtain a crude fluorocarboxylic acid;

step E: purifying the crude product of the fluorine-containing carboxylic acid to obtain a pure product of the fluorine-containing carboxylic acid.

According to one embodiment of the first aspect of the application, prior to said step a, in the dynamic mixer 1, the fluorinating agent, the catalyst and the solvent are premixed to form a premix.

According to another embodiment of the first aspect of the application, in step a, the premix is continuously fed into the synthesis reactor 2, while the reaction raw materials are continuously fed into the synthesis reactor 2 independently of the premix.

According to another embodiment of the first aspect of the application, the fluorinating agent is selected from one or more of the following: potassium fluoride, sodium fluoride, ammonium fluoride, calcium fluoride, lithium fluoride, cesium fluoride.

According to another embodiment of the first aspect of the application, the catalyst is selected from one or more of the following quaternary ammonium salts: benzyl triethylammonium chloride, tetrabutylammonium bisulfate, tetrabutylammonium bromide, hyperbranched quaternary ammonium salts, trifluoromethyltetramethyl ammonium salts, dibutyl tetrabutylammonium salts of phosphoric acid, and malondialdehyde tetrabutylammonium salts.

According to another embodiment of the first aspect of the application, the solvent is selected from one or more of the following: dimethylformamide, dimethylacetamide, acetonitrile, dimethylsulfoxide, and methylpyrrolidone.

According to another embodiment of the first aspect of the application, the reaction feed comprises a halogenated olefin and a halogenated ester; the halogenated olefin is selected from one or more of the following: halogenated C2-C12 olefins, halogenated C2-C12 olefin dimers, halogenated C2-C12 olefin trimers, halogenated C2-C12 olefin tetramers, halogenated C2-C12 olefin pentamers, halogenated C2-C12 olefin hexamers; the halogenated esters are selected from one or more of the following: C1-C12 alkyl esters of halogenated C2-C12 carboxylic acids, C3-C12 cycloalkyl esters of halogenated C2-C12 carboxylic acids, and C6-C12 aralkyl esters of halogenated C2-C12 carboxylic acids.

According to another embodiment of the first aspect of the application, in said step a, the reaction is carried out at a temperature of 40-100 ℃ and the residence time of the reaction mass in the synthesis reactor 2 is 10 minutes to 2 hours.

According to another embodiment of the first aspect of the present application, the step B includes the following operations: separating: carrying out solid-liquid separation on the crude product stream f in a centrifugal screw type solid-liquid separator g to obtain solid waste salt and a liquid crude product stream g; purifying: the liquid crude product stream g is extracted with extractant h in an extraction coalescer 4 and then rectified in a continuous rectification column 5, recovering solvent and extractant h to obtain purified product stream m.

According to another embodiment of the first aspect of the application, in step C the purified product stream m is mixed with a hydrolysis solvent o and an alkaline solution p to effect hydrolysis. According to another embodiment of the first aspect of the application, the hydrolysis is carried out at a temperature of 30-80 ℃.

According to another embodiment of the first aspect of the application, the hydrolysis solvent o is a C1-C6 alcohol and the weight ratio of hydrolysis solvent o to purified product stream m is from 50:100 to 500:100.

According to another embodiment of the first aspect of the application, the lye p is a solution of an alkaline agent in water in a concentration of 5-40 wt.%, the alkaline agent is an alkali metal hydroxide, and the weight ratio of lye p to purified product stream m is 100:100 to 500:100.

According to another embodiment of the first aspect of the present application, the hydrolysis product stream is acidified and separated in step D in a mixer-coalescer 8 to obtain a crude fluorocarboxylic acid, which is then purified in step E in a purification unit to obtain a pure fluorocarboxylic acid. According to another embodiment of the first aspect of the application, the acidification is carried out at a temperature between 0 and 80 ℃. According to another embodiment of the first aspect of the application, the molar ratio of acid r used in the acidification process to the fluorocarboxylate salt comprised in the hydrolysis product stream q is comprised between 1:1 and 4:1.

According to another embodiment of the first aspect of the application, the fluorine-containing carboxylic acid is a C2-C15 fluorine-containing alkyl C2-C6 carboxylic acid.

According to another embodiment of the first aspect of the present application, the fluorine-containing carboxylic acid produced by the process of the present application does not comprise perfluorooctanoic acid. According to another embodiment of the first aspect of the present application, perfluoro octanoic acid, which is not in compliance with the regulations of the relevant laws and regulations (such as national or worldwide environmental protection and/or various industrial product fields), is not included in the fluorine-containing carboxylic acid produced by the process of the present application. According to another embodiment of the first aspect of the present application, the fluorocarboxylic acid produced by the process of the present application does not include any fluorocarboxylic acid which is toxic, harmful or can accumulate in the human body.

In a second aspect the application provides a fluorine-containing carboxylic acid product obtainable by the process of any of the embodiments of the first aspect of the application.

In a third aspect, the application provides a continuous reaction apparatus for carrying out the method according to any embodiment of the first aspect of the application, the apparatus comprising: a dynamic mixer 1, a synthesis reactor 2, a solid-liquid separation device 3, an extraction coalescer 4, a continuous rectifying tower 5, a hydrolysis device 6, a continuous rectifying tower 7, a mixer-coalescer 8 and a purification device 9.

The method, apparatus and device of the present application are further described in the detailed description section below with reference to the accompanying drawings.

Drawings

FIG. 1 shows a schematic process flow diagram of the method of the present application;

FIG. 2 shows a picture of crystals of a fluorocarboxylic acid product synthesized in an example of the application;

FIG. 3 shows a picture of a continuous reaction apparatus used in an embodiment of the present application;

FIG. 4 shows a picture of a continuous rectification column used in an embodiment of the present application;

FIG. 5 shows nuclear magnetic resonance fluorine spectra of perfluorohexyl acetic acid, a fluorocarboxylic acid product synthesized in the examples of the present application;

FIG. 6 shows the nuclear magnetic resonance hydrogen spectrum of perfluorohexyl acetic acid, a fluorocarboxylic acid product synthesized in the examples of the present application.

Reference numerals:

1 a dynamic mixer; 2 a synthesis reactor; 3a solid-liquid separation device; 4, extracting a coalescer; 5a continuous rectifying tower; a hydrolysis device; 7, a continuous rectifying tower; 8a mixer-coalescer; 9 a purification device;

a halogenated olefin; halogenated esters; c a fluorinating agent; d a solvent; e a catalyst; f a crude product stream; g a liquid crude product stream; h, extracting agent; j an extract waste stream; k extracting the crude product stream; l overhead; m purifying the product stream; n hydrolyses the product stream; o solvent; p alkali liquor; q purifying the hydrolysis product stream; r acid reagent; s a crude fluorocarboxylic acid; t, waste acid liquid; u fluorocarboxylic acid pure product; v bottoms; w water.

Detailed Description

"Range" is disclosed herein in the form of lower and upper limits. There may be one or more lower limits and one or more upper limits, respectively. The given range is defined by selecting a lower limit and an upper limit. The selected lower and upper limits define the boundaries of the particular ranges. All ranges that can be defined in this way are inclusive and combinable, i.e., any lower limit can be combined with any upper limit to form a range. For example, ranges of 60-120 and 80-110 are listed for specific parameters, with the understanding that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3,4 and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5.

In the present application, unless otherwise indicated, the numerical range "a-b" represents a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed throughout, and "0-5" is simply a shorthand representation of a combination of these values.

In the present application, all the embodiments mentioned herein and the preferred embodiments may be combined with each other to form new technical solutions, if not specifically described.

In the present application, all technical features mentioned herein and preferred features may be combined with each other to form new technical solutions, if not specifically stated.

In the present application, the term "comprising" as referred to herein means open or closed unless otherwise specified. For example, the term "comprising" may mean that other components not listed may also be included, or that only listed components may be included.

The method of the present application comprises step a, step B, step C, step D and step E described above. According to one embodiment of the application, the steps a-E are performed sequentially. According to one embodiment of the application, steps a-E described above, as well as any other steps (e.g. a pre-mixing step performed before step a, and other steps performed before or after any step) are performed in a continuous manner.

The method of the present application will be described with reference to an exemplary embodiment of the method of the present application shown in fig. 1.

According to one embodiment of the application, prior to step a, a premixing step is first carried out in which at least a portion of the reaction mass is mixed to form a premix, and the premix and the remaining reaction mass (if any) are then fed into the synthesis reactor 2 independently of each other for reaction. In the embodiment shown in fig. 1, the premixing step is carried out in a dynamic mixer 1. For example, the fluorinating agent c, catalyst e and solvent d may be fed into the dynamic mixer 1 in a continuous manner such that the fluorinating agent c, catalyst e and solvent d in liquid form are mixed together to form a premix liquid mass; the premix liquid is then fed into the synthesis reactor 2, whereas the reaction raw materials (which comprise the haloolefin a and the haloester b) are fed into the synthesis reactor 2 independently of the premix.

According to another embodiment, which differs from that of fig. 1, the fluorinating agent c, the catalyst e and the solvent d may be fed into the dynamic mixer 1 in a continuous manner, so that the halogenated olefin a, the halogenated esters b, the fluorinating agent c, the catalyst e and the liquid solvent d are mixed together to form a premix liquid mass, which is then fed into the synthesis reactor 2.

According to one embodiment of the present application, the solvent d is a liquid organic compound capable of effectively dissolving or dispersing the fluorinating agent c, the catalyst e, the halogenated olefin a and the halogenated ester b without interfering with the reaction and the fluorinated product. For example, the solvent d may be an aprotic organic solvent, e.g. the solvent d may be selected from one or more of the following: dimethylformamide, dimethylacetamide, acetonitrile, dimethylsulfoxide, methylpyrrolidone; preferably dimethylformamide and/or methylpyrrolidone. According to one embodiment of the application, a portion of the solvent may be used to dissolve or disperse the above-described fluorinating agent c, catalyst e, halogenated olefin a and halogenated ester b, which are then added to the dynamic mixer 1 or synthesis reactor 2.

According to one embodiment of the application, the fluorinating agent c is an alkali metal fluoride, which may be, for example, one or more of the following: preferably, the fluorinating agent c is potassium fluoride, sodium fluoride, ammonium fluoride, calcium fluoride, lithium fluoride, cesium fluoride, or a combination of the two. According to one embodiment of the present application, the total amount of the materials finally fed into the synthesis reactor 2, wherein the weight ratio of the fluorinating agent c to the solvent d is 30:100 to 150:100, for example, 40:100 to 120:100, 42:100 to 50:100, 100:100 to 120:100, 40:100 to 80:100, or a combination of any two of the above values.

According to one embodiment of the application, the catalyst is a quaternary ammonium salt, which may be selected, for example, from one or more of the following: benzyl triethylammonium chloride, tetrabutylammonium bisulfate, tetrabutylammonium bromide, hyperbranched quaternary ammonium salt, trifluoromethyltetramethyl ammonium salt, dibutyl tetrabutylammonium phosphate, and malondialdehyde tetrabutylammonium salt; the preferred catalyst may be selected from one or more of the following: tetrabutylammonium bromide and trifluoromethyltetramethyl ammonium salt. The "hyperbranched quaternary ammonium salt" mentioned above means that at least one (e.g., one, two, three, four) of the four alkyl/aryl groups attached to the nitrogen atom has a highly branched structure, such as t-butyl, isopropyl, t-amyl, etc., and one example of the hyperbranched quaternary ammonium salt is a Gemini quaternary ammonium salt. According to one embodiment of the application, the weight ratio of catalyst e to solvent d is from 2:100 to 30:100, for example from 3:100 to 25:100, or from 4:100 to 20:100, or from 4.5:100 to 15:100, or from 5:100 to 10:100, or from 6:100 to 8:100, or within the numerical range obtained by combining any two of the above endpoints with each other, in the total feed to the synthesis reactor 2.

According to one embodiment of the application, the halogenated olefin is an olefin substituted with one or more halogen atoms, including for example fluorine, chlorine, bromine, iodine, or any combination thereof, which may replace 5-100%, such as 15-100%, or 30-100%, or 50-100%, or 60-100%, or 80-100%, or 90-100%, of the hydrogen atoms in the olefin, preferably is a perhalogenated olefin. According to an exemplary embodiment, the halogenated olefin may be a fluoroolefin, preferably a perfluorinated olefin.

Examples of said halogenated olefins are selected from one or more of the following: halogenated C2-C12 olefins, halogenated C2-C12 olefin dimers, halogenated C2-C12 olefin trimers, halogenated C2-C12 olefin tetramers, halogenated C2-C12 olefin pentamers, halogenated C2-C12 olefin hexamers; or one or more selected from the following: fluorinated C2-C12 olefins, fluorinated C2-C12 olefin dimers, fluorinated C2-C12 olefin trimers, fluorinated C2-C12 olefin tetramers, fluorinated C2-C12 olefin pentamers, and fluorinated C2-C12 olefin hexamers; or one or more selected from the following: perfluoroC 2-C12 olefins, perfluoroC 2-C12 olefin dimers, perfluoroC 2-C12 olefin trimers, perfluoroC 2-C12 olefin tetramers, perfluoroC 2-C12 olefin pentamers, perfluoroC 2-C12 olefin hexamers; such as perfluoroC 2-C8 olefins, perfluoroC 2-C8 olefin dimers, perfluoroC 2-C8 olefin trimers, perfluoroC 2-C8 olefin tetramers, perfluoroC 2-C8 olefin pentamers, perfluoroC 2-C8 olefin hexamers; or perfluoro C3-C6 olefin, perfluoro C3-C6 olefin dimer, perfluoro C3-C6 olefin trimer, perfluoro C3-C6 olefin tetramer, perfluoro C3-C6 olefin pentamer, perfluoro C3-C6 olefin hexamer. For example, the halogenated olefin may include one or more of the following: hexafluoropropylene dimer, hexafluoropropylene trimer, hexafluoropropylene tetramer, preferably hexafluoropropylene dimer.

According to one embodiment of the present application, the weight ratio of the halogenated olefin a to the solvent d is 150:100 to 500:100, for example, 200:100 to 400:100, or 210:100 to 310:100, or 200:100 to 220:100, or 230:100 to 250:100, or 280:100 to 310:100, or a combination of any two of the above values, in the total material finally fed into the synthesis reactor 2.

According to one embodiment of the application, the halogenated esters are selected from one or more of the following: a C1-C12 alkyl halogenated C2-C12 carboxylate, a C3-C12 cycloalkyl halogenated C2-C12 carboxylate, and a C6-C12 aralkyl halogenated C2-C12 carboxylate; for example, C1-C8 alkyl esters of halogenated C2-C8 carboxylic acids, C3-C10 cycloalkyl esters of halogenated C2-C8 carboxylic acids, C6-C10 aralkyl esters of halogenated C2-C8 carboxylic acids; or a C1-C6 alkyl halogenated C2-C6 carboxylate, a C3-C8 cycloalkyl halogenated C2-C6 carboxylate, a C6-C8 aralkyl halogenated C2-C6 carboxylate; or a C1-C4 alkyl ester of a halogenated C2-C4 carboxylic acid, a C3-C6 cycloalkyl ester of a halogenated C2-C4 carboxylic acid, a C6-C8 aralkyl ester of a halogenated C2-C4 carboxylic acid. "halo" in the "halo esters" means that the esters are substituted with one or more, e.g., one, two, three, four, five, six halogen atoms, e.g., perhalo; the halogen atoms may include fluorine, chlorine, bromine, iodine, or a combination of two or more of the foregoing halogen atoms. According to an exemplary embodiment of the present application, examples of the halogenated esters include: ethyl (mono) bromoacetate, (mono) ethyl fluoroacetate, and (mono) ethyl chloroacetate.

According to one embodiment of the present application, the weight ratio of the halogenated esters b to the solvent d is 80:100 to 220:100, for example, 100:100 to 200:100, or 120:100 to 175:100, or 110:100 to 130:100, or 130:100 to 150:100, or 160:100 to 180:100, or a combination of any two of the above values.

According to one embodiment of the application, the reaction of step a may be carried out in one or more synthesis reactors 2. Each synthesis reactor 2 may comprise a tank reactor, a tubular reactor, or the like; the tank reactor may comprise a vertical tank or a horizontal tank. Various stirring devices may be disposed within the reactor, which may include four-bladed inclined paddles, ribbon paddles, three-bladed propeller blades, according to one exemplary embodiment.

In the case of using a plurality of synthesis reactors 2, the plurality of synthesis reactors 2 may be in a parallel or serial relationship with each other, or the plurality of synthesis reactors 2 may be arranged in a serial-parallel manner, for example, four, six, eight, ten or twelve synthesis reactors are divided into two groups (first group and second group), the two groups being connected in series, and the reactors in each group being connected in parallel; or four, six, eight, ten or twelve synthesis reactors are divided into two groups (first and second groups) connected in parallel, with two reactors in each group connected in series.

According to one embodiment of the application, in case a plurality of synthesis reactors is used, one or more separators, such as solid-liquid separators, may be provided between any one of the synthesis reactors and the synthesis reactor downstream thereof.

FIG. 3 shows a photograph of an exemplary continuous reaction apparatus for practicing the present application.

As described above, at least a portion (part or all) of the reaction materials (which may include, for example, part or all of one or more of the following: haloolefins, haloesters, fluorinating agents, solvents, and catalysts) is fed to the synthesis reactor as a premix via a premixing step, with the remainder of these reaction materials (if any) being fed to the synthesis reactor as a separate stream. The reaction mass reacts in the synthesis reactor to form a fluorocarboxylate ester within the reactor. According to one embodiment of the application, the reaction mass is introduced into the synthesis reactor in a continuous manner and, after the reaction of the mass under stirring to form the fluorocarboxylate, the reacted mass (comprising fluorocarboxylate, unreacted reaction starting material, solvent, catalyst, remaining fluorinating agent, small amounts of by-products, etc.) in the reactor is discharged from the synthesis reactor in a continuous flow such that the total amount of mass in the synthesis reactor 2 remains constant, as described above for the proportions of the components in the reaction mass. According to one embodiment of the application, the material in the reactor 2 may be discharged passively by increasing the amount of material in the synthesis reactor, or may be promoted by the action exerted by a pump (e.g. pushing action, shearing force, pressure difference, etc.), for example actively by the action of a screw pump. The material continuously flowing out of the synthesis reactor is herein denoted as crude product stream f.

In one exemplary embodiment of the application, the fluorochemical carboxylic acid ester formed by the fluorination reaction in the synthesis reactor may be a C2-C12 alkyl ester of a C2-C12 fluorochemical carboxylic acid, such as a C2-C10 alkyl ester of a C3-C10 fluorochemical carboxylic acid, or a C2-C8 alkyl ester of a C4-C8 fluorochemical carboxylic acid, or a C2-C6 alkyl ester of a C6-C8 fluorochemical carboxylic acid. According to one embodiment of the present application, the carboxylic acid moiety (i.e., the moiety after the ester group excludes the alkoxy group) in the "fluorocarboxylic ester" may have one or more substituted fluorine atoms, for example, the number of substituted fluorine atoms may be 1 to 24, or 2 to 20, or 3 to 16, or 4 to 16, or 6 to 16, or 8 to 16, or within a numerical range obtained by combining any two of the above-mentioned end values with each other. For example, the carboxylic acid moiety in the "fluorocarboxylate" may be perfluoro substituted.

According to another embodiment of the present application, the alcohol moiety (alkoxy moiety) in the "fluorocarboxylate" may contain no substituted fluorine atom, or may have one or more substituted fluorine atoms, for example, the number of substituted fluorine atoms may be 1 to 24, or 2 to 20, or 3 to 16, or 4 to 16, or 6 to 16, or 8 to 16, or within a numerical range obtained by combining any two of the above-mentioned end values with each other. For example, the alcohol moiety in the "fluorocarboxylate" may be completely unsubstituted or perfluorinated.

According to a preferred embodiment of the present application, in the fluorine-containing carboxylic acid ester, the moiety derived from the halogenated olefin is perfluorinated, whereas the moiety derived from the halogenated ester is not perfluorinated. According to an exemplary embodiment of the present application, the fluorine-containing carboxylic acid ester is a C1-C8 alkyl ester of a C2-C12 fluorine-containing alkyl C2-C6 carboxylic acid, or may be a C2-C4 alkyl ester of a C2-C8 perfluoroalkyl C2-C4 carboxylic acid, for example may be ethyl perfluorohexyl acetate. The corresponding fluorine-containing carboxylic acid may be perfluorohexyl acetic acid.

Without wishing to be bound by any particular theory, it has surprisingly been found that the partially fluorinated carboxylic acids of the present application have good biodegradability compared to prior art commonly used perfluorocarboxylic acids such as perfluorohexanoic acid, effectively overcome the biotoxicity and in vivo accumulation drawbacks of prior art perfluorocarboxylic acids, and have good process properties that can be a good substitute for prior art toxic and hazardous perfluorocarboxylic acids.

During the reaction in step a, the residence time of the material in the synthesis reactor 2 is from 10 minutes to 2 hours, for example from 20 minutes to 1 hour, or from 10 to 20 minutes, or from 40 minutes to 2 hours.

During the reaction in step a, the temperature in the synthesis reactor 2 may be 40-100 ℃, for example 70-90 ℃.

Next in step B, the crude product stream f is continuously fed to a solid-liquid separation device 3, in which the crude product stream f is subjected to a continuous solid-liquid separation operation, and then the liquid crude product stream g, from which solid impurities are removed, is continuously fed to an extraction coalescer 4. The extractant h is continuously fed into the extraction coalescer 4 through an extractant inlet on the extraction coalescer 4, thoroughly mixed with the liquid crude product stream g, and then phase separated, with the extraction waste stream j (which contains mainly solvent and extractant) exiting from a separate outlet of the extraction coalescer 4, and the extraction crude product stream k (which contains the relatively higher purity fluorocarboxylate esters) continuously exiting from the extraction coalescer 4 into a continuous rectification column 5 located downstream thereof.

According to one embodiment of the application, the extraction waste stream j mainly comprises the solvent as described above and the extractant, and the content of the product (fluorocarboxylate) therein is less than 2 wt%, such as less than 1.5 wt%, or less than 1 wt%. According to another embodiment of the application, the extraction waste stream j may be further subjected to a rectification treatment, whereby the separated solvent may be sent to a premixing step or step a, the separated extractant may be recycled, reintroduced from the extractant inlet of the extraction coalescer 4, and the separated fluorocarboxylate may be treated separately or sent to a downstream hydrolysis step C.

According to one embodiment of the application, the content of fluorocarboxylic acid ester in the extracted crude product stream k is further increased, for example, may be greater than 85 wt%, or greater than 90 wt%.

According to one embodiment of the application, the extractant h is selected from one or more of the following: water, aromatic hydrocarbons (e.g., C6-C16 aromatic hydrocarbons), ethers (e.g., C2-C12 ethers). According to one embodiment of the application, the weight ratio of extractant h to liquid crude product stream g fed continuously to extraction coalescer 4 is from 100:2 to 100:20, and may be, for example, from 100:5 to 100:15, or from 100:7 to 100:12, from 100:8 to 100:10, or within the numerical range obtained by combining any two of the above endpoints with each other.

According to one embodiment of the application, the extracted crude product stream k is rectified in a continuous rectification column 5 (also referred to as "first continuous rectification column"), the residual solvent and small amounts of extractant contained in the mixture are discharged as overhead stream l, while the content of the desired product fluorocarboxylate is further increased and discharged as purified product stream m from the product outlet of the continuous rectification column 5. Some other impurities or by-products are discharged as bottom stream. Figure 4 shows a picture of a continuous rectification column used in the present application.

In the next step C, the purified product stream m is continuously fed into the hydrolysis apparatus 6 while simultaneously continuously feeding the lye p and the solvent (also referred to as "hydrolysis solvent") o to the hydrolysis apparatus 6, so that the fluorocarboxylic acid ester in the purified product stream m is hydrolyzed to form the corresponding fluorocarboxylic acid and/or salt thereof, and the resulting hydrolyzed product stream n continuously flows out from the hydrolysis apparatus 6 and is fed to the continuous rectification column 7 (also referred to as "second continuous rectification column").

According to one embodiment of the application, one or more of said hydrolysis devices 6 may be employed; in the case of using a plurality of hydrolysis apparatuses 6, the plurality of hydrolysis apparatuses may be arranged in series or in parallel, and are preferably connected in series with each other.

According to one embodiment of the application, the residence time of the purified product stream m in the hydrolysis device 6 may be from 1 minute to 2 hours, for example from 5 to 100 minutes, or from 10 to 90 minutes, or from 20 to 80 minutes, or from 30 to 70 minutes.

According to one embodiment of the application, the hydrolysis reaction temperature in the hydrolysis device 6 is 30-80 ℃, for example 40-70 ℃, or 50-60 ℃.

According to one embodiment of the application, the hydrolysis solvent o may comprise a C1-C6 alcohol, such as methanol, ethanol, propanol, butanol, pentanol, hexanol, and the like, preferably methanol.

According to one embodiment of the application, the hydrolysis solvent o and the purified product stream m are fed continuously to the hydrolysis device such that the weight ratio of the hydrolysis solvent o to the purified product stream m is from 50:100 to 500:100; for example, the weight ratio may be 80:100 to 400:100; or 90:100 to 300:100; or 95:100 to 200:100; or 100:100 to 180:100.

According to one embodiment of the application, the alkaline solution p continuously fed to the hydrolysis device is a solution of an alkaline agent having a concentration of 5-40% by weight in water, for example the alkaline agent may be an alkali metal hydroxide, preferably sodium hydroxide, lithium hydroxide, potassium hydroxide, or a mixture thereof. According to one embodiment of the application, the lye p and the purified product stream m are fed continuously to the hydrolysis device such that the weight ratio of the hydrolysis solvent p to the purified product stream m is from 100:100 to 500:100; for example, the weight ratio may be 110:100 to 400:100; or 120:100 to 200:100; or 130:100 to 180:100; or 140:100 to 160:100; or 150:100 to 300:100; or 180:100 to 250:100; or 200:100 to 240:100, or within the numerical range obtained by combining any two of the above endpoints with each other.

According to one embodiment of the application, the hydrolysis product stream n is continuously fed into the continuous rectification column 7 (second continuous rectification column), continuously subjected to a rectification treatment (second rectification treatment), and the purified hydrolysis product stream q after rectification is fed to a downstream coalescer. According to one embodiment of the application, a part or a majority of the other material separated off in the second continuous rectification column may be recycled to the previous step. For example, as shown in FIG. 1, one or both of the hydrolysis solvent flowing out from the top of the column and the lye flowing out from the bottom of the column may be recycled back to the hydrolysis apparatus 6 for carrying out the hydrolysis operation without treatment or after necessary treatment and purification; in addition to the hydrolysis solvent and lye recycled here, fresh hydrolysis solvent and lye are also provided as required, so that the weight ratio (flow ratio) of each of the hydrolysis solvent and lye to the purified product stream m satisfies the description of the preceding paragraph.

The purified hydrolysis product stream q separated in the continuous rectification column 7 is continuously fed into a mixer-coalescer 8, and additionally fed into the mixer-coalescer 8 with an acidic reagent r, and the purified hydrolysis product stream q is acidified so that the fluorocarboxylate is converted into the objective fluorocarboxylic acid. The product fluorocarboxylic acid is continuously separated from the waste acid water t in a mixing-coalescing device 8, and the obtained fluorocarboxylic acid crude product s is continuously input into a downstream purification device 9 for further purification, and finally the high-purity fluorocarboxylic acid pure product v is obtained.

According to one embodiment of the application, the temperature of the acidification step may be between 0 and 80 ℃, preferably between 20 and 50 ℃. According to one embodiment of the application, the acidic reagent used in the acidification step may be a strong mineral acid or an aqueous solution thereof, and in case an aqueous solution is used, the concentration of the aqueous solution may be 0.01-30 wt.%, for example 0.1-20 wt.%, or 0.2-10 wt.%, or 0.5-5 wt.%, or 0.8-2 wt.%. The strong inorganic acid may be selected from hydrochloric acid, sulfuric acid, phosphoric acid, or a combination thereof. According to one embodiment of the application, both the acidic reagent r and the purified hydrolysis product stream q are continuously fed to the mixer-coalescer 8 such that the molar ratio of the acid (hydrogen ions) to the fluorocarboxylate contained in the purified hydrolysis product stream q is from 1:1 to 4:1, which may be, for example, from 1:1 to 3:1, or from 1:1 to 2:1, or from 1.1:1 to 1.5:1.

According to one embodiment of the application, the hybrid-coalescer 8 may comprise a mixer (for continuous acidification) and a coalescer (for continuous separation) in series with each other; or may include a mixing section and a coalescing section in the same apparatus.

According to one embodiment of the application, the purification device 9 may be a continuous distillation device, a continuous rectification device, or a combination thereof. For example, the purification apparatus 9 may be a continuous rectification column (third continuous rectification column) for further purification therein, with a trace amount of water w being discharged from the top of the column and a high-purity fluorocarboxylic acid pure product u being collected, and with the bottom waste material v being caused to flow out at the bottom of the column. The tower bottom waste v is mixed impurities of fluorine-containing high-boiling residues. The trace water and fluorine-containing carboxylic acid pure products at the top of the tower can be collected by switching a valve according to the requirement.

Compared with the prior art, the continuous production process of the application can realize the following advantages:

1. When the fluorine-containing carboxylic ester is synthesized, the solvent and the solid materials are premixed according to the proportion, so that the solid is changed into paste or slurry, the solid materials have continuous feeding feasibility, the whole raw materials are kept constant in a certain proportion, the stability of the production quality can be kept, and the solid materials are always in a dynamic state, so that the condition of blocking a pipeline or a valve can not occur. The synthesized fluorine-containing carboxylic acid ester can obtain high-purity fluorine-containing carboxylic acid ester after passing through a continuous solid-liquid separation device, a continuous extraction liquid separation device and a continuous rectification device, and a raw material basis is provided for the subsequent continuous production of fluorine-containing carboxylic acid;

2. The high-purity fluorine-containing carboxylic ester enters a continuous hydrolysis device, and the hydrolysis speed can be timely adjusted according to the reaction condition by adjusting the alkali ratio and the solvent ratio, so that the high-purity fluorine-containing carboxylic ester is compatible with single or multi-series kettle bodies. The hydrolyzed fluorine-containing carboxylate enters a mixer, is continuously fed with acid for acidification, is continuously fed into a coalescer for separation, and can obtain a crude product of fluorine-containing carboxylic acid with higher purity, and the crude product of fluorine-containing carboxylic acid with higher purity can be obtained through continuous rectification and purification;

3. Compared with intermittent reaction, the continuous production process has high overall reaction efficiency, is not easy to generate blockage and overtemperature, has lower equipment failure rate, high automation and continuous degree and higher product stability;

4. The fluorine-containing carboxylic acid prepared by the method is preferably the partially fluorinated fluorine-containing carboxylic acid, can be used as a substitute of perfluorooctanoic acid, has lower toxic action, contains a degradable hydrocarbon structure, has good environmental protection property, and has extremely low surface tension and critical micelle concentration.

In the following examples, the excellent effects achieved by the process of the present application are specifically illustrated. The purpose of which is to provide a better understanding of the present application. It should be understood that these embodiments are merely illustrative and not limiting. The reagents used in the examples were commercially available as usual unless otherwise indicated. The methods and conditions used in the examples are conventional methods and conditions unless otherwise specified.

Examples

All reagents used in the following examples were analytically pure and used without further purification, and all water used was deionized water. The gas chromatograph used in this example is model 8890 gas chromatograph offered by agilent.

Example 1

In this example, using the continuous reaction apparatus shown in fig. 3, potassium fluoride, N-dimethylformamide and tetrabutylammonium bromide were first fed into a dynamic mixer at a mass ratio of 30:70:1, sufficiently mixed therein to form a uniform slurry-like material, and continuously fed into the dynamic mixer at the same time as the slurry-like material was continuously fed out from the outlet of the dynamic mixer in the above-described ratio to maintain the continuous feeding out of the mixed material.

The slurry material was continuously fed into the synthesis reactor while ethyl bromoacetate and hexafluoropropylene dimer were continuously fed into the synthesis reactor such that the mass flow ratio of slurry material, ethyl bromoacetate and hexafluoropropylene dimer was 100:120:215. The temperature of the synthesis reactor was controlled at 70 ℃, in which a stirring device was provided, and the reaction mixture was moved toward the outlet of the reactor while being stirred and pushed with new charge while reacting in the synthesis reactor. The residence time of the reaction mass in the reactor was about 20 minutes.

The material flowing out of the synthesis reactor was sent to a continuous solid-liquid separation device (LW 220 x 880 centrifugal screw solid-liquid separator) for solid-liquid separation. The separated solid materials are used as solid waste to be discharged, the separated liquid enters a No. 2 continuous synthesis reactor, and potassium fluoride and N, N-dimethylformamide are additionally added into the No. 2 continuous synthesis reactor, so that the mass flow ratio of the slurry materials output from the dynamic mixer to ethyl bromoacetate and hexafluoropropylene dimer is 100:15:10 at any moment. The temperature in the No. 2 continuous synthesis reactor was maintained at 90℃and a stirring device was provided therein, and the reaction mixture was moved toward the outlet of the reactor while being stirred and pushed with new charge while reacting in the synthesis reactor. The residence time of the reaction mass in the reactor was about 20 minutes.

The product stream output from the continuous synthesis reactor No.2 was continuously input into a continuous solid-liquid separator (LW 220 x 880 centrifugal screw solid-liquid separator), the solid material obtained by separation was removed as waste, and the liquid phase obtained was a crude product stream of fluorocarboxylic ester having a purity of not less than 73%, and the reaction yield was 96% as measured by gas chromatography.

The crude product stream of the fluorocarboxylate is then continuously fed into an extraction coalescer (M50 type high speed centrifugal extractor) and water is continuously fed into the extraction coalescer such that the flow ratio (mass ratio) of the crude product of the fluorocarboxylate to water is 10:1, after mixing therein, a phase separation is performed, resulting in an extracted crude product stream (purity of fluorocarboxylate > 93% as measured by gas chromatography), which is continuously fed to a first continuous rectification column, which phase separation additionally produces an aqueous solution of N, N dimethylformamide, from which, after dehydration, the N, N dimethylformamide can be recovered for recycling.

In the first continuous rectifying column (as shown in FIG. 4, a wire mesh packing is used in the continuous rectifying column, the pressure in the kettle is about 100mbar, the temperature in the kettle is about 47 ℃), the extracted crude product stream is rectified, a purified product stream is collected at an outlet near the top, and the purity of the fluorocarboxylic acid ester is more than or equal to 99% and the yield is more than 90% as measured by gas chromatography).

The purified product stream was continuously fed to the hydrolysis apparatus while continuously adding an aqueous sodium hydroxide solution having a concentration of 12 wt% and methanol to the hydrolysis apparatus such that the purified product stream had a sodium hydroxide to methanol flow ratio (by weight) of 3:5:5. The temperature in the hydrolysis apparatus was maintained at 50 c and the residence time of the material in the hydrolysis apparatus was about 35 minutes. The degree of hydrolysis is greater than 99% as measured by nuclear magnetic resonance.

The hydrolysis product stream was fed to a second continuous rectification column (which was identical to the first continuous rectification column, the internal temperature was around 300mbar, the internal temperature was around 75 ℃) and the hydrolysis product stream was rectified, and the purified hydrolysis product stream was collected at an outlet near the bottom. The methanol with the purity more than 99% is obtained at the top of the second continuous rectifying tower and can be directly conveyed to a hydrolysis device for recycling.

The purified hydrolysate stream is fed into a mixer for continuous acidification, the acidification temperature is controlled to be 50 ℃, and the pH value of the acidified material is ensured to be less than 2. Continuously introducing the acidified product into a coalescer for continuous separation to obtain the fluorine-containing carboxylic acid with the phase separation purity of more than 90% and the waste acid liquid. The hydrolysis and acidification phase separation operation is carried out to obtain crude fluorine-containing carboxylic acid, wherein the loss rate of the fluorine-containing carboxylic acid is lower than 1%.

And then the crude product of the fluorine-containing carboxylic acid is conveyed to a third continuous rectifying tower (the third continuous rectifying tower is completely the same as the first continuous rectifying tower, the temperature in the kettle is about 150mbar, the temperature in the kettle is about 120 ℃), the pure product of the fluorine-containing carboxylic acid is obtained, and the crystallized image is shown in figure 2. The pure product is characterized by nuclear magnetic resonance technology, and the nuclear magnetic fluorine spectrum and the nuclear magnetic hydrogen spectrum of the characterized pure product are respectively shown in fig. 5 and 6. The purity of the fluorine-containing carboxylic acid (perfluorohexyl-ethyl acetate) is measured to be more than 99 percent, and the purification yield is more than or equal to 90 percent.

Example 2

In this example, using the same continuous reaction apparatus as in example 1, potassium fluoride, N-dimethylformamide and tetrabutylammonium bromide were first fed into a dynamic mixer at a mass ratio of 45:90:2, thoroughly mixed therein to form a uniform slurry-like material, and continuously fed into the dynamic mixer at the same time as the slurry-like material was continuously fed out from the outlet of the dynamic mixer in the above-described ratio to maintain the continuous feeding out of the mixed material.

The slurry material was continuously fed into the synthesis reactor while ethyl bromoacetate and hexafluoropropylene dimer were continuously fed into the synthesis reactor such that the mass flow ratio of slurry material, ethyl bromoacetate and hexafluoropropylene dimer was 137:120:215. The temperature of the synthesis reactor was controlled at 90 ℃, in which a stirring device was provided, and the reaction mixture was moved toward the outlet of the reactor while being stirred and pushed with new charge while reacting in the synthesis reactor. The residence time of the reaction mass in the reactor was about 1 hour.

The material flowing out of the synthesis reactor was sent to a continuous solid-liquid separation device (LW 220 x 880 centrifugal screw solid-liquid separator) for solid-liquid separation. The separated solid material is used as solid waste to be discharged, the separated liquid phase is a crude product stream of fluorine-containing carboxylic ester with the purity of more than or equal to 71 percent, and the reaction yield is 93 percent by gas chromatography.

The crude product stream of the fluorocarboxylate is then continuously fed into an extraction coalescer (M50 type high speed centrifugal extractor) and water is continuously fed into the extraction coalescer such that the flow ratio (mass ratio) of the crude product of the fluorocarboxylate to water is 10:1, after mixing therein, a phase separation is performed, resulting in an extracted crude product stream (purity of fluorocarboxylate > 92%, as measured by gas chromatography), which is continuously fed to a first continuous rectification column, which phase separation additionally produces an aqueous solution of N, N dimethylformamide, from which, after dehydration, the N, N dimethylformamide can be recovered for recycling.

In the first continuous rectification column (which is the same as the first continuous rectification column used in example 1, the pressure in the column is about 100mbar, the temperature in the column is about 47 ℃), the crude product stream after extraction is rectified, and the purified product stream is collected from an outlet near the top, wherein the purity of the fluorocarboxylic acid ester is greater than or equal to 99% and the yield is greater than 90% as measured by gas chromatography).

The purified product stream was continuously fed to the hydrolysis apparatus while continuously adding sodium hydroxide and methanol to the hydrolysis apparatus at a concentration of 12 wt.% such that the purified product stream had a sodium hydroxide to methanol flow ratio (by weight) of 3:5:3. The temperature in the hydrolysis apparatus was maintained at 55℃and the residence time of the material in the hydrolysis apparatus was about 70 minutes. The degree of hydrolysis was 99% as measured by nuclear magnetic resonance.

The hydrolysis product stream is fed to a second continuous rectification column (which is identical to the first continuous rectification column, the temperature in the column is around 300mbar, the column temperature is around 75 ℃), the hydrolysis product stream is rectified and the purified hydrolysis product stream is collected at an outlet near the bottom. The methanol with the purity more than 99% is obtained at the top of the second continuous rectifying tower and can be directly conveyed to a hydrolysis device for recycling.

The purified hydrolysate stream is fed into a mixer for continuous acidification, the acidification temperature is controlled to be lower than 50 ℃, and the pH value of the acidified material is ensured to be less than 2. Continuously introducing the acidified product into a coalescer for continuous separation to obtain the fluorine-containing carboxylic acid with the phase separation purity of more than 90% and the waste acid liquid. The hydrolysis and acidification phase separation operation is carried out to obtain crude fluorine-containing carboxylic acid, wherein the loss rate of the fluorine-containing carboxylic acid is lower than 1%.

And then conveying the crude product of the fluorine-containing carboxylic acid to a third continuous rectifying tower (the third continuous rectifying tower is completely the same as the first continuous rectifying tower, the temperature in a kettle is about 150mbar, the temperature in the kettle is about 120 ℃), rectifying the crude product of the fluorine-containing carboxylic acid to obtain a pure product of the fluorine-containing carboxylic acid, wherein the purity of the fluorine-containing carboxylic acid is greater than 99% and the purification yield is more than or equal to 90% as measured by nuclear magnetic resonance.

Example 3

In this example, using the same continuous reaction apparatus as in example 1, cesium fluoride, N-dimethylformamide and tetrabutylammonium bromide were first fed into a dynamic mixer at a mass ratio of 117:100:1, thoroughly mixed therein to form a uniform slurry-like material, and potassium fluoride, N-dimethylformamide and tetrabutylammonium bromide were continuously fed into the dynamic mixer at the same time as the slurry-like material was continuously fed out from the outlet of the dynamic mixer in the above-described ratio to maintain the continuous feeding of the mixed material.

The slurry material was continuously fed into the synthesis reactor while ethyl bromoacetate and hexafluoropropylene dimer were continuously fed into the synthesis reactor such that the mass flow ratio of slurry material, ethyl bromoacetate and hexafluoropropylene dimer was 218:120:215. The temperature of the synthesis reactor was controlled at 90 ℃, in which a stirring device was provided, and the reaction mixture was moved toward the outlet of the reactor while being stirred and pushed with new charge while reacting in the synthesis reactor. The residence time of the reaction mass in the reactor was about 1 hour.

The material flowing out of the synthesis reactor was sent to a continuous solid-liquid separation device (LW 220 x 880 centrifugal screw solid-liquid separator) for solid-liquid separation. The separated solid material is used as solid waste to be discharged, the separated liquid phase is a crude product stream of fluorine-containing carboxylic ester with the purity of more than or equal to 69 percent, and the reaction yield is 91 percent by gas chromatography.

The purified product stream was continuously fed to the hydrolysis apparatus while continuously adding a lithium hydroxide aqueous solution having a concentration of 15 wt% and methanol to the hydrolysis apparatus so that the purified product stream had a flow ratio (by weight) of lithium hydroxide to methanol of 4:3:5. The temperature in the hydrolysis apparatus was maintained at 60℃and the residence time of the material in the hydrolysis apparatus was about 30 minutes. The degree of hydrolysis was 99% as measured by nuclear magnetic resonance.

Comparative example 1

In this comparative example, no continuous reaction and purification process design was employed, nor was a premixing operation of the reaction mass employed.

Specifically, potassium fluoride, N-dimethylformamide, bromobutyl ammonium bromide, hexafluoropropylene dimer and tetrabutylammonium bromide were added at a time in a weight ratio of 9:19:24:43:2 to a synthesis reactor, the temperature of which was controlled at 90℃and the reaction was continued for 1 hour.

After the reaction is finished, the materials in the synthesis reactor are conveyed to a solid-liquid separation device (LW 220 x 880 centrifugal screw solid-liquid separator) for solid-liquid separation. The separated solid material is used as solid waste to be discharged, the separated liquid phase is a crude product stream of fluorine-containing carboxylic ester with the purity of more than or equal to 70 percent, and the reaction yield is 80 percent as measured by gas chromatography.

The crude product stream of the fluorocarboxylate is then fed into an extraction coalescer (M50 type high speed centrifugal extractor) and water is fed into the extraction coalescer such that the mass ratio of the fluorocarboxylate crude product to water is 10:1, thoroughly stirred and then allowed to stand for stratification, the upper layer being an aqueous solution of N, N dimethylformamide from which, after dehydration, the N, N dimethylformamide can be recovered for recycle. The lower layer is the crude product after extraction (purity of the fluorocarboxylic ester > 90% as measured by gas chromatography).

The extracted crude product was fed to a first rectifying column (the first rectifying column is the same as the first continuous rectifying column used in example 1, the pressure in the vessel is about 100mbar, the temperature in the vessel is about 47 ℃), the extracted crude product was rectified, and a purified product was collected at an outlet near the top, wherein the purity of fluorocarboxylic acid ester was not less than 99% and the yield was more than 90% as measured by gas chromatography).

The purified product was fed to a hydrolysis unit to which sodium hydroxide and methanol were added at a concentration of 12 wt.% such that the purified product stream was 3:5:3 by weight sodium hydroxide to methanol. The temperature in the hydrolysis apparatus was maintained at 55℃and the residence time of the material in the hydrolysis apparatus was 35 minutes. The degree of hydrolysis was found to be 99%.

The hydrolysate was fed into a second rectifying column (the second rectifying column was identical to the first rectifying column, the temperature in the vessel was about 300mbar, the temperature in the vessel was about 75 ℃), the hydrolysate was rectified, and the purified hydrolysate was collected at an outlet near the bottom. And obtaining a mixed solution of methanol, ethanol and water at the top of the second rectifying tower.

And conveying the purified hydrolysate into a mixer for continuous acidification, controlling the acidification temperature to be lower than 50 ℃, and ensuring the pH value of the acidified material to be less than 2. And continuously introducing the acidified product into a coalescer for separation to obtain the fluorine-containing carboxylic acid with the phase separation purity of more than 90% and the waste acid liquid.

And then the crude fluorocarboxylic acid is conveyed to a third rectifying tower (the third rectifying tower is identical to the first rectifying tower, the temperature in the kettle is about 150mbar, the temperature in the kettle is about 120 ℃), the fluorocarboxylic acid is rectified, and the fluorocarboxylic acid purity is greater than 99% as measured by nuclear magnetic resonance, and in addition, the time required for the same-scale single-batch production of the above examples 1-3 and comparative example 1 is compared with the following table.

Table 1 examples 1-3 and comparative example 1 total time required to synthesize batches of the same scale.

As can be seen from Table 1 above, the batch reaction of comparative example 1 requires a significant amount of time to warm up, cool down and stand the material, excluding the effects of experimental error, while the continuous production process of examples 1-3 can save at least 30% of the time in the same scale apparatus.

In addition, the present invention was carried out in the following examples 4 and 5, and the influence of the adjustment of the process conditions on the results was examined.

Example 4

In this example 4, the procedure of example 1 was repeated, but in the hydrolysis step, the material remained in the hydrolysis apparatus, the process parameters of the hydrolysis apparatus were adjusted, and samples were continuously taken from the hydrolysis apparatus at 5 minute intervals, the degree of hydrolysis of the material therein was examined, and when the degree of hydrolysis reached 99%, the time at this time was recorded. The process parameters and minimum time required for adequate hydrolysis are summarized in the following table:

Table 1: hydrolysis data statistics (lye used is aqueous sodium hydroxide and solvent is methanol).

Example 5

In this example 5, the procedure of example 1 was repeated, but in the acidification step, the process parameters of this step were adjusted, and the results after acidification were examined and summarized as shown in table 2 below:

TABLE 2 influence of acidification reaction parameters on the acidification effect (the acid reagent is sulfuric acid solution)

Acidizing formula	Acid ratio	Acidification temperature DEG C	Fluorine-containing carboxylic acid%	Impurity%	Residual acid after separating
						1	1.2	30	95	0	1
2	1.5	30	95	0	3
						3	2	30	90	0	7
4	1.5	60	80	10	3

Claims

1. A continuous process for preparing a fluorine-containing carboxylic acid, the process comprising:

Step A: continuously feeding the reaction raw material, the fluorinating agent, the solvent and the catalyst into the synthesis reactor (2), allowing the reaction raw material to be fluorinated and the fluorinating agent to react in the synthesis reactor (2) to generate fluorine-containing carboxylic acid ester, and continuously flowing out a crude product stream (f) containing fluorine-containing carboxylic acid ester from the synthesis reactor (2);

and (B) step (B): separating and purifying the crude product stream (f) to obtain a purified product stream (m);

Step C: hydrolyzing the purified product stream (m) to obtain a hydrolyzed product stream (n) comprising fluorocarboxylic acid and/or salt thereof;

Step D: acidifying the hydrolysis product stream (n) to obtain a crude fluorocarboxylic acid;

2. The method according to claim 1, characterized in that prior to said step a, in a dynamic mixer (1) the fluorinating agent, the catalyst and the solvent are premixed to form a premix;

Then in step a, the premix is continuously fed into the synthesis reactor (2) while the reaction raw materials are continuously fed into the synthesis reactor (2) independently of the premix.

3. The method of claim 1 or 2, wherein the fluorinating agent is selected from one or more of the following: potassium fluoride, sodium fluoride, ammonium fluoride, calcium fluoride, lithium fluoride, cesium fluoride;

The catalyst is selected from one or more quaternary ammonium salts of: benzyl triethylammonium chloride, tetrabutylammonium bisulfate, tetrabutylammonium bromide, hyperbranched quaternary ammonium salt, trifluoromethyltetramethyl ammonium salt, dibutyl tetrabutylammonium phosphate, and malondialdehyde tetrabutylammonium salt;

the solvent is selected from one or more of the following: dimethylformamide, dimethylacetamide, acetonitrile, dimethylsulfoxide, methylpyrrolidone;

The reaction raw materials comprise halogenated olefin and halogenated esters; the halogenated olefin is selected from one or more of the following: halogenated C2-C12 olefins, halogenated C2-C12 olefin dimers, halogenated C2-C12 olefin trimers, halogenated C2-C12 olefin tetramers, halogenated C2-C12 olefin pentamers, halogenated C2-C12 olefin hexamers; the halogenated esters are selected from one or more of the following: C1-C12 alkyl esters of halogenated C2-C12 carboxylic acids, C3-C12 cycloalkyl esters of halogenated C2-C12 carboxylic acids, and C6-C12 aralkyl esters of halogenated C2-C12 carboxylic acids.

4. The process according to claim 1 or 2, characterized in that in step a the reaction is carried out at a temperature of 40-100 ℃ and the residence time of the reaction mass in the synthesis reactor (2) is 10 minutes to 2 hours.

5. The method according to claim 1 or 2, wherein step B comprises the following operations:

separating: carrying out solid-liquid separation on the crude product stream (f) in a centrifugal screw type solid-liquid separator (g) to obtain solid waste salt and a liquid crude product stream (g);

purifying: the liquid crude product stream (g) is extracted with an extractant (h) in an extraction coalescer (4) and then rectified in a continuous rectification column (5) to give a purified product stream (m).

6. A process according to claim 1 or 2, characterized in that in step C the purified product stream (m) is mixed with a hydrolysis solvent (o) and an alkaline solution (p) to effect hydrolysis;

the hydrolysis is carried out at a temperature of 30-80 ℃;

The hydrolysis solvent (o) is a C1-C6 alcohol, the weight ratio of hydrolysis solvent (o) to purified product stream (m) being from 50:100 to 500:100;

the lye (p) is a solution of an alkaline agent in water in a concentration of 5-40 wt%, the alkaline agent is an alkali metal hydroxide, and the weight ratio of lye (p) to purified product stream (m) is 100:100 to 500:100.

7. The process according to claim 1 or 2, characterized in that in step D the hydrolysis product stream(s) is acidified and separated in a mixer-coalescer (8) and then purified in step E in a purification unit (9) to obtain a pure product of the fluorocarboxylic acid;

the acidification is carried out at a temperature of 0-80 ℃;

The molar ratio of the acidic reagent (r) used in the acidification process to the fluorocarboxylate salt comprised in the hydrolysis product stream (n) is from 1:1 to 4:1.

8. The method of claim 1 or 2, wherein the fluorine-containing carboxylic acid is a C2-C12 fluorine-containing alkyl C2-C6 carboxylic acid.

9. A fluorine-containing carboxylic acid product made by the process of any one of claims 1-8, the fluorine-containing carboxylic acid not comprising perfluorooctanoic acid.

10. A continuous fluorination reaction apparatus for carrying out the method of any one of claims 1-8, said apparatus comprising: a dynamic mixer (1), a synthesis reactor (2), a solid-liquid separation device (3), an extraction coalescer (4), a continuous rectifying tower (5), a hydrolysis device (6), a continuous rectifying tower (7), a mixing-coalescer (8) and a purification device (9).