JP2011093808A - Method of producing fluorine-containing carboxylic acid anhydride - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing a fluorine-containing carboxylic acid anhydride at a high yield using a corresponding fluorine-containing carboxylic acid fluoride. <P>SOLUTION: The method of producing a fluorine-containing carboxylic acid anhydride represented by formula (3): (R<SB>f</SB>CO)<SB>2</SB>O [in the formula, R<SB>f</SB>represents the same group as the group in formula (1)] includes reacting a fluorine-containing lithium carboxylate represented by formula (1): R<SB>f</SB>COOLi (in the formula, R<SB>f</SB>represents a fluorine-containing alkyl group) with a fluorine-containing carboxylic acid fluoride represented by formula (2): R<SB>f</SB>COF [in the formula, R<SB>f</SB>represents the same group as the group in formula (1)]. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a method for producing an anhydrous fluorine-containing carboxylic acid useful as an intermediate for medical and agrochemical intermediates and functional materials, and more specifically, a method for producing a condensation reaction between a fluorine-containing carboxylic acid fluoride and a fluorine-containing lithium carboxylate. About.

Acetic anhydrides are important raw materials for organic synthesis as acylating agents for aromatic compounds. In the method for producing acetic anhydride ((CH ₃ CO) ₂ O), acetic acid is obtained by heating ethylidene diacetate in the presence of an acid catalyst such as zinc chloride by passing phosgene through acetic acid using anhydrous aluminum chloride as a catalyst. A large-scale method includes the reaction of ketene produced by thermal decomposition of steam or acetone with acetic acid, the oxidation of acetaldehyde with oxygen in the presence of a catalyst such as cobalt acetate, and the production of acetic anhydride via peracetic ester. It has been broken.

On the other hand, halocarboxylic acid anhydrides are obtained by dehydrating trifluoroacetic acid with phosphoric anhydride (P ₂ O ₅ ) or sulfuric anhydride to remove trifluoroacetic anhydride (Non-patent Document 1) and difluoroacetic acid with phosphoric anhydride (P ₂ Dehydrated with O ₅ ) and mixed with difluoroacetic anhydride (Non-patent Document 2), trichloroacetic acid chloride and ½ amount of water, and under pressure and heating conditions, anhydrous trichloroacetic acid (Non-patent Document 3), potassium trifluoroacetate Trifluoroacetic anhydride (Patent Document 1), trifluoroacetic acid chloride and alkali metal carbonate or alkaline earth metal carbonate of trifluoroacetic acid as pressure and heating conditions. Heating conditions include trifluoroacetic anhydride (Patent Document 2), trifluoroacetic acid fluoride and alkali metal carbonate or alkaline earth gold Carbonate is mixed and trifluoroacetic anhydride (patent document 3), a mixture of dichloroacetic anhydride and trifluoroacetic acid is refluxed under pressure and heating conditions, and trifluoroacetic anhydride (patent document 4), trifluoroacetic acid chloride and It has been reported that it can be synthesized by many methods such as mixing zinc oxide, copper oxide, cadmium oxide and the like to obtain trifluoroacetic anhydride (Patent Document 5) under pressure and heating conditions.

  Difluoroacetic anhydride can be obtained by refluxing a mixture of difluoroacetic acid and phosphorus pentoxide, further adding phosphorus pentoxide and then distilling (Non-patent Document 2), but no other methods have been applied.

JP 2001-64228 A Japanese Patent Publication No.45-38523 JP 2001-64228 A JP-B 61-33139 No.46-6888

J. of Organic Chemistry 1949, 2976 J. of Organic Chemistry 1956, 376 Chem. Abstr., 76, 85329 (1972) (Metody Poluch. Khim. Reakt. Prep., No. 21, 111 (1970))

  Each of the precursors of acetic anhydride produced on a large scale uses a characteristic chemical substance. In the case of an anhydride of halocarboxylic acid, halocarboxylic acid or its acid halide is used as the precursor.

  Dehydration of halocarboxylic acid with phosphorus pentoxide produces polyphosphoric acid, which has a high viscosity, making it difficult to recover halocarboxylic acid anhydride from the product. It is not possible. Also, recovery and disposal of these dehydrating agents is not easy in terms of safety, handling and environment. The halide of halocarboxylic acid is acid chloride except for one example, but acid chloride is not necessarily the precursor that can be most efficiently prepared from the starting material. For example, the acid fluoride of perfluorocarboxylic acid may be obtained directly by electrolytic fluorination of carboxylic acid or the like.

  Therefore, the present invention provides a method for producing the corresponding anhydrous fluorinated carboxylic acid with high yield using the fluorinated carboxylic acid fluoride.

  The present inventors examined a method for synthesizing an anhydrous fluorine-containing carboxylic acid using a fluorine-containing carboxylic acid fluoride. When a fluorine-containing carboxylic acid fluoride and a fluorine-containing lithium carboxylate were reacted, a by-product of lithium fluoride was obtained. It discovered that an anhydrous fluorine-containing carboxylic acid was produced | generated, and resulted in this invention.

  Here, the fluorine anion having a small ionic radius forms a more stable salt with a lithium cation having a smaller ionic radius than a potassium cation or a sodium cation having a larger ionic radius. That is, when acid chloride is used instead of fluorine-containing carboxylic acid fluoride, or when sodium or potassium is used instead of lithium, the metal salt produced as a by-product is formed as an anhydrous fluorine-containing carboxylic acid as will be apparent from Reference Example 2 below. Not as stable as you can. On the other hand, when fluorine-containing carboxylic acid fluoride and fluorine-containing lithium carboxylate were combined, anhydrous fluorine-containing carboxylic acid was produced with a high yield specifically as shown in each Example described later.

The present invention is as follows.
[1] General formula (1)
R _f COOLi (1)
(Wherein R _f represents a fluorine-containing alkyl group) and a fluorine-containing lithium carboxylate represented by the general formula (2)
R _f COF (2)
(Wherein R _f represents the same group as the group in the general formula (1)). The general formula (3) comprising reacting the fluorine-containing carboxylic acid fluoride represented by the general formula (3)
(R _f CO) ₂ O (3)
(In the formula, R _f represents the same group as the group in the general formula (1)).

[2] The fluorine-containing lithium carboxylate is represented by the general formula (4)
R _f COX (4)
(In the formula, R _f represents the same group as the group in the general formula (1), X represents F, Cl, Br, or I). The fluorine-containing carboxylic acid halide represented by lithium hydroxide is reacted with lithium hydroxide. The manufacturing method of the anhydrous fluorine-containing carboxylic acid of the invention 1 which is the fluorine-containing lithium carboxylate obtained by making it carry out.

[3] The fluorine-containing lithium carboxylate is represented by the general formula (5)
R _f COOH (5)
(In the formula, R _f represents the same group as the group in the general formula (1).) The fluorine-containing lithium carboxylate obtained by reacting the fluorine-containing carboxylic acid represented by lithium hydroxide or lithium carbonate. A method for producing an anhydrous fluorine-containing carboxylic acid according to Invention 1 or 2.

  [4] A step of synthesizing a fluorine-containing lithium carboxylate by a method of reacting a fluorine-containing carboxylic acid halide and lithium hydroxide, or a method of reacting a fluorine-containing carboxylic acid and lithium hydroxide or lithium carbonate; The manufacturing method of the anhydrous fluorine-containing carboxylic acid of the invention 1 which performs the process with which a fluorine-containing carboxylic acid fluoride is made to react using the same container.

  [5] Step of synthesizing fluorine-containing lithium carboxylate, step of removing water accompanying fluorine-containing carboxylic acid using azeotropic distillation, step of reacting fluorine-containing lithium carboxylate and fluorine-containing carboxylate fluoride The manufacturing method of the anhydrous fluorine-containing carboxylic acid of the invention 4 performed using the same container.

[6] The process for producing an anhydrous fluorine-containing carboxylic acid according to Inventions 1 to 5, wherein R _f is a difluoromethyl group or a trifluoromethyl group in the general formula (1).

  [7] The method for producing an anhydrous fluorine-containing carboxylic acid according to inventions 1 to 6, wherein the reaction between the fluorine-containing lithium carboxylate and the fluorine-containing carboxylic acid fluoride is carried out at a reaction temperature of −78 to 120 ° C.

  In the method of the present invention, the yield of the reaction between the fluorine-containing carboxylic acid fluoride and the fluorine-containing lithium carboxylate is high, and since the fluorine-containing carboxylic acid fluoride can be directly used as a reaction raw material, Since such a multi-stage process is not required, the production efficiency as a whole process from industrial raw materials becomes remarkably high. In addition, hydrogen fluoride is not generated in principle despite the use of acid fluoride, which is advantageous in waste treatment.

The present invention is a method for producing anhydrous fluorine-containing carboxylic acid (R _f CO) ₂ O comprising reacting fluorine-containing lithium carboxylate (R _f COOLi) with fluorine-containing carboxylic acid fluoride (R _f COF). The reaction is considered to proceed according to the following reaction formula.

_{R f COF + R f COOLi →} (R f CO) 2 O + LiF
R _f is a fluorine-containing alkyl group. In the specification, unless otherwise specified, the “alkyl group” collectively refers to linear, branched, and cyclic, and represents an alkyl group having 1 to 4 carbon atoms or a cyclic alkyl group having 3 to 7 carbon atoms as “lower alkyl”. Sometimes referred to as “group”. The fluorine-containing alkyl group represented by R _f has at least one fluorine atom, may have any number of halogen (chlorine, bromine, iodine) atoms, fluoromethyl group, difluoromethyl group, trifluoro Halomethyl groups such as methyl group, dichlorofluoromethyl group, chlorodifluoromethyl group, bromodifluoromethyl group, dibromofluoromethyl group, 2,2,2-trifluoroethyl group, 1,1,2,2,2-pentafluoro Examples include an ethyl group, 2,2,3,3,3-pentafluoropropyl group, n-heptafluoropropyl group, 1,1,1,3,3,3-hexafluoroisopropyl group. Among these, a halomethyl group is preferable, and a difluoromethyl group or a trifluoromethyl group is more preferable.

  The fluorine-containing carboxylic acid fluoride may be produced by any method, and a commercially available product can also be used. Perfluorocarboxylic acid fluoride can be obtained by electrolytic fluorination reaction of fluorine-containing carboxylic acid chloride or oligomerization reaction of perfluoropropene oxide or tetrafluoroethylene oxide.

The difluoroacetic acid fluoride may be produced by any method. For example, (1) a method in which difluoroacetic acid is reacted with phosphorus pentoxide, thionyl chloride, etc. and then fluorinated with a metal fluoride such as potassium fluoride, (2) 1-alkoxy represented by CHF ₂ CF ₂ OR ′ A method of decomposing 1,1,2,2-tetrafluoroethane in the presence of sulfur trioxide and fluorosulfuric acid (J. Am. Chem. Soc., 1950 72, 1860), (3) 1-alkoxy-1 , 1,2,2-tetrafluoroethane is reacted in the presence of a catalyst such as antimony halide or titanium halide (JP-A-8-92162), (4) 1-alkoxy-1,1,2,2 A method for producing difluoroacetic acid fluoride by thermally decomposing tetrafluoroethane in the presence of a catalyst (Japanese Patent Laid-Open No. 8-20560) is known.

  The reaction of the method (4) is represented by the following formula.

CHF ₂ CF ₂ OR '→ CHF ₂ COF + R'F
R of 1-alkoxy-1,1,2,2-tetrafluoroethane represented by the general formula CHF ₂ CF ₂ OR ′ (R ′ represents a monovalent organic group) which is a starting material for this reaction. 'Is a leaving group and is not particularly limited, but an alkyl group or a lower alkyl group is more preferable. For example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group and the like are preferable.

  1-alkoxy-1,1,2,2-tetrafluoroethane can be obtained by a known production method. For example, it can be synthesized by a method in which alcohol (R′OH) and tetrafluoroethylene are reacted in the presence of a base.

  Specifically, 1-methoxy-1,1,2,2-tetrafluoroethane can be synthesized by a method in which methanol and tetrafluoroethylene are reacted in the presence of potassium hydroxide (J. Am. Chem. Soc. 73, 1329 (1951)).

Specific examples of the fluorine-containing ether that can be used in the first step of the present invention include, but are not limited to, the following.
1-methoxy-1,1,2,2-tetrafluoroethane (CHF ₂ CF ₂ OMe), 1-ethoxy-1,1,2,2-tetrafluoroethane (CHF ₂ CF ₂ OEt), 1- (n -Propoxy) -1,1,2,2-tetrafluoroethane, 1-isopropoxy-1,1,2,2-tetrafluoroethane, 1- (n-butoxy) -1,1,2,2-tetra Examples include fluoroethane, 1- (s-butoxy) -1,1,2,2-tetrafluoroethane, 1- (t-butoxy) -1,1,2,2-tetrafluoroethane, and the like.

  The catalyst used for thermal decomposition is a solid catalyst, and metal oxides and metal fluorinated oxides described in JP-A-8-92162 can be used as the catalyst. Phosphate can also be used as the catalyst. The phosphate may be supported on a carrier.

  As phosphoric acid, any of orthophosphoric acid, polyphosphoric acid, and metaphosphoric acid may be used. Examples of polyphosphoric acid include pyrophosphoric acid. Phosphate is the metal salt of these phosphoric acids. Since it is easy to handle, orthophosphoric acid is preferred. Phosphate refers to a metal salt of these phosphoric acids. In this specification, an acid in which a metal is substituted with a hydrogen atom is also referred to as a metal salt.

  The phosphate is not particularly limited, but is composed of hydrogen, aluminum, boron, alkaline earth metal, titanium, zirconium, lanthanum, cerium, yttrium, rare earth metal, vanadium, niobium, chromium, manganese, iron, cobalt, nickel. And at least one metal phosphate selected from the group. Preferably, the main component is aluminum phosphate, cerium phosphate, boron phosphate, titanium phosphate, zirconium phosphate, chromium phosphate, or the like. It is also preferable that the metal of a subsidiary component is included. As specific subcomponents, cerium, lanthanum, yttrium, chromium, iron, cobalt, nickel and the like are preferable, but cerium, iron and yttrium are more preferable. Of these, aluminum phosphate, cerium phosphate, and phosphates composed of these two types are more preferable.

  The method for preparing the catalyst is not particularly limited, and a commercially available phosphate may be used as it is, or a general precipitation method may be used. As a specific preparation method of the precipitation method, for example, diluted ammonia water is added dropwise to a mixed aqueous solution of metal nitrate (in the case of a plurality of raw material salts, each raw material salt solution is prepared) and phosphoric acid to adjust pH. To adjust to precipitate and leave to mature as necessary. Then, it is washed with water and it is confirmed that it has been sufficiently washed with the conductivity of the washing water. In some cases, alkali metal containing a portion of the slurry is measured. It is then filtered and dried. There is no particular limitation on the drying temperature. Preferably 80 to 150 degreeC is good. More preferably, it is 100 degreeC-130 degreeC. The obtained dried product is pulverized to uniform particle size, or further pulverized and molded. Thereafter, firing is performed in an air or nitrogen atmosphere at 200 ° C. to 1500 ° C. The firing is preferably performed at 400 to 1300 ° C, more preferably 500 to 900 ° C.

  Although depending on the temperature, the firing time is about 1 to 50 hours, preferably about 2 to 24 hours. Since the calcination treatment is a treatment necessary for stabilizing the phosphate, if the treatment is performed at a temperature lower than the above temperature range or the treatment time is short, the catalyst activity may not be sufficiently exhibited at the initial stage of the reaction. . In addition, it is not preferable to perform the calcination treatment at a temperature higher than the above temperature range or for a long time because not only excessive heating energy is required but also crystallization of the catalyst may occur.

The operation of adding a metal component other than the main component is preferably performed with a metal salt, and nitrates, chlorides, oxides, phosphates, and the like of the metal are preferable. Among them, nitrate is preferable because it is easy to prepare. Although there is no restriction | limiting in particular in addition amount, Generally it is 1 gram atom or less with respect to 1 gram atom of phosphorus, Preferably it is 0.5 gram atom or less. More preferably, it is 0.3 gram atom or less. The addition of these metal components may be performed at the time of catalyst preparation, or may be performed on the phosphate after the catalyst is calcined. The obtained catalyst has different physical properties depending on the type of metal salt and the preparation method and conditions. The catalyst may be used as it is, but it can also be used in a state of being supported on a carrier. As support, alumina, titania, zirconia, zirconia sulfate (ZrO (SO ₄ ))
Examples thereof include metal oxides such as metal oxides, silicon carbide, silicon nitride, activated carbon, etc., and activated carbon having a large specific surface area is particularly preferable.

  Activated carbon carrying phosphoric acid or phosphate can be prepared by immersing it in phosphoric acid and impregnating it, or drying and coating or adsorbing it by spraying. In the case of loading a compound, it can be prepared by impregnating a solution of the compound to be loaded, or drying a coating or adsorbed by spraying. In addition, a second compound is allowed to act on activated carbon impregnated with a solution of the compound, or coated or adsorbed by spraying, thereby causing a precipitation reaction or the like on the activated carbon surface to carry a compound different from the first compound. You can also. Further, the phosphate-carrying catalyst can also be prepared by carrying out the above-described phosphate preparation method in the presence of a support such as activated carbon. As an example, activated carbon supporting aluminum phosphate is shown in the examples.

  Activated carbon is made from plant-based, peat, lignite, lignite, bituminous coal, anthracite, etc. that are made from wood, charcoal, coconut husk, palm kernel charcoal, raw ash, etc. Any of petroleum type or synthetic resin type such as carbonized polyvinylidene chloride may be used. For example, activated carbon manufactured from bituminous coal (BPL granular activated carbon made by Toyo Calgon), coconut shell charcoal (granular white birch GX, SX, CX, XRC manufactured by Nippon Enviro Chemicals), Toyo Calgon PCB) and the like, but is not limited thereto. The shape and size are usually used in a granular form, but can be used within a normal knowledge range as long as it is suitable for a reactor such as a sphere, fiber, powder, or honeycomb.

The activated carbon used as the carrier for the thermal decomposition reaction is preferably activated carbon having a large specific surface area. The specific surface area of the activated carbon is sufficient in a range of commercially available standards, are each 400m ² / g~3000m ² / g, preferably 800m ² / g~2000m ² / g. Furthermore, when using activated carbon as a support, it is usually immersed in a basic aqueous solution such as ammonium hydroxide, sodium hydroxide, potassium hydroxide or the like for about 10 hours or longer at room temperature or when activated carbon is used as a catalyst support. It is desirable to perform pretreatment with acid such as nitric acid, hydrochloric acid, hydrofluoric acid, etc. to activate the carrier surface and remove ash in advance.

  Further, the carrier such as an oxide of the present invention may contain a metal component and an atom other than oxygen, and the other atom is preferably a fluorine atom or a chlorine atom. For example, partially fluorinated alumina, partially chlorinated alumina, partially fluorinated chlorinated alumina, partially fluorinated zirconia, partially fluorinated titania and the like may be used. The ratio of chlorine atoms and fluorine atoms in the oxide catalyst is not particularly limited.

  In the present specification and claims, unless otherwise specified, partially fluorinated or chlorinated oxides such as alumina and zirconia as described above are oxides such as “alumina” and “zirconia”. Display by name.

These supports include at least one metal oxide selected from the group consisting of alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), titania (TiO ₂ ), zirconia sulfate, and partially fluorinated oxides thereof. Catalysts are preferred, and alumina and partially fluorinated alumina are more preferred in terms of reactivity and catalyst life.

These partially fluorinated oxides can be used as a support for a fluorine-containing carboxylic acid fluoride synthesis catalyst, and can also be used as a catalyst. Preparation, pretreatment, use, etc. as a catalyst can be applied as described in the present specification for preparation, pretreatment, use, etc. as a support as it is or according to common general technical knowledge. That is, when a metal oxide such as alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), titania (TiO ₂ ) or the like is used as a catalyst, it can be handled in the same manner as a supported catalyst on which a metal compound or the like is supported. Good.

  The catalyst is usually used in the form of particles or granules. The diameter of the particles or the granulated body (all may be referred to as “particle diameter”) is not particularly limited, and is usually about 20 μm to 10 mm. When the catalyst contains a chlorine atom or a fluorine atom, the chlorine atom or the fluorine atom may exist only on the surface of the metal oxide.

  Before use, the catalyst is partially fluorinated by contacting with a fluorine-containing compound such as hydrogen fluoride, fluorinated hydrocarbon or fluorinated chlorinated hydrocarbon in advance to change the composition of the catalyst during the reaction, shorten the life, It is effective to prevent abnormal reactions.

  In particular, treatment with hydrogen fluoride can significantly increase the activity of the reaction. The fluorination treatment with hydrogen fluoride is preferably performed by contacting with hydrogen fluoride at least at a temperature higher than the reaction temperature of the reaction according to the present invention.

  Specifically, in the case of a phosphate simple substance, it is about 200 to 700 ° C, preferably about 250 to 600 ° C, and more preferably 300 to 550 ° C. On the other hand, in the case of a supported catalyst using an oxide or activated carbon as a carrier, the temperature is about 200 to 600 ° C, preferably about 250 to 500 ° C, more preferably 300 to 400 ° C. In any case, if the temperature is lower than 200 ° C., it takes time for the treatment, and it is not preferable to perform the treatment beyond the maximum temperature range because excessive heating energy is required. The treatment time is also related to the treatment temperature and cannot be limited, but it is about 1 hour to 10 days, preferably about 3 hours to 3 days.

  In the case of activated carbon not supporting phosphoric acid, even if it is treated with hydrogen fluoride, it shows little activity. However, when activated carbon treated with phosphoric acid is treated with hydrogen fluoride, the conversion rate is 96. under the same reaction conditions. The catalyst activity was 1% and selectivity: 98.0%. Also from this, the effect of the hydrogen fluoride treatment can be easily seen.

  Furthermore, it is preferable to perform an activation treatment prior to the reaction. As the activation treatment, it is sufficiently dehydrated in a nitrogen stream at about 250 ° C. to 300 ° C., and an organic fluorine compound such as dichlorodifluoromethane or chlorodifluoromethane, or a gas or catalyst treatment such as hydrogen fluoride or chlorine trifluoride. It is preferable to activate with an inorganic fluorine compound showing a sufficient vapor pressure in the state. Of these, hydrogen fluoride is particularly preferred. This activation treatment is considered to generate an active catalyst containing fluorine atoms on the entire surface of the catalyst.

Further, when R ′ of 1-alkoxy-1,1,2,2-tetrafluoroethane (CHF ₂ CF ₂ OR ′), which is a raw material for thermal decomposition, is a group having 2 or more carbon atoms, R′F produced Is decomposed in the reaction region to generate hydrogen fluoride, which may have an effect of increasing the activity of the catalyst.

  The thermal decomposition reaction is recommended as a most preferable form of the gas phase flow continuous system, but is not limited thereto. The type of the reactor is preferably a fixed bed type or a fluidized bed type, and the dimensions and shape of the reactor can be appropriately changed according to the amount of the reactants and the like.

  In pyrolysis, an inert gas may exist in the reaction conditions. Examples of the inert gas include nitrogen or rare gases, and nitrogen or helium is preferable from the viewpoint of ease of handling and availability. The amount in the presence of the inert gas is not particularly limited, but if it is too much, there is a possibility that the recovery rate is lowered. Therefore, in the usual case, the raw material 1-alkoxy-1,1,2,2-tetrafluoro An amount less than the ethane feed rate is preferred.

  The reaction temperature for thermal decomposition varies depending on the type of catalyst and the raw material. Usually, it is 100-400 degreeC, about 150-350 degreeC is preferable and 180-280 degreeC is more preferable. If the reaction temperature is less than 100 ° C., the conversion tends to be low, which is not preferable. When the reaction temperature exceeds 400 ° C., severe heat resistance is required for the reaction apparatus, and excessive heating energy is required, which is not economically preferable.

  The reaction time (contact time) is usually 0.1 to 300 seconds, preferably 0.5 to 200 seconds, and more preferably 1 to 60 seconds. If the reaction time is too short, the conversion rate may be lowered. On the other hand, if the reaction time is too long, productivity is lowered, which is not preferable. The reaction pressure is not particularly limited and may be normal pressure, reduced pressure, or increased pressure. A pressure of about 0.05 to 0.5 MPa (0.5 to 5 atmospheres) is preferable, and usually a pressure in the vicinity of atmospheric pressure that facilitates operation is preferable.

  In the catalyst, coking may occur over time, and the activity of the catalyst may decrease. The catalyst having reduced activity can be easily regenerated by contacting with oxygen at 200 ° C. to 1200 ° C., preferably 400 ° C. to 800 ° C. It is convenient to perform the oxygen treatment while it is loaded in the reaction tube or in an external device. This is done by circulating oxygen there. As a method of circulating oxygen, other gas may coexist, and air diluted with nitrogen or air is economically preferable. Further, a gas having oxidizing power such as chlorine and fluorine can be used.

  In the thermal decomposition reaction, in addition to the desired difluoroacetic acid fluoride, as a by-product, a compound obtained by further decomposing alkyl fluoride (R′F) or alkyl fluoride is generated. For example, when ethyl fluoride is generated as the alkyl fluoride, ethylene and hydrogen fluoride may be formed. The crude product containing the by-product obtained by the reaction can be used as a raw material for the reaction with the fluorine-containing carboxylic acid lithium salt and the fluorine-containing carboxylic acid lithium salt without containing purification alkyl fluoride. In addition, crude products obtained mainly by removing alkyl fluoride can be used, difluoroacetic acid fluorides that have been further purified to high purity can be used, or these various purified gases can be cooled. Alternatively, it can be compressed and stored in a pressure vessel. Difluoroacetic acid fluoride can be purified by distillation.

  The fluorine-containing carboxylic acid lithium salt used in the present invention may be obtained by any method. Commercial products may be obtained. The fluorine-containing carboxylic acid lithium salt is obtained by dissolving lithium carbonate or lithium hydroxide (LiOH) or a hydrated salt thereof in a fluorine-containing carboxylic acid aqueous solution and evaporating the water. Moreover, you may add fluorine-containing carboxylic acid or fluorine-containing carboxylic acid halide to the container which prepared the lithium component and water.

  An example of the manufacturing method of fluorine-containing lithium carboxylate is shown. Fluorine-containing carboxylic acid or fluorine-containing carboxylic acid halide is added to lithium hydroxide or lithium carbonate using water as a medium. A method of dissolving lithium hydroxide or lithium carbonate in water and adding a fluorine-containing carboxylic acid or fluorine-containing carboxylic acid halide thereto, or a method of adding lithium hydroxide or lithium carbonate to an aqueous solution of a fluorine-containing carboxylic acid, In addition to adding a lithium hydroxide or lithium carbonate aqueous solution to an aqueous solution of fluorine carboxylic acid, in addition, lithium hydroxide or lithium carbonate, fluorine-containing carboxylic acid or fluorine-containing carboxylic acid halide, and water are charged in a reaction vessel in any order. You can enter. These reactions are shown below.

R _f COOH + LiOH → R _f COOLi + H ₂ O
R _f COOH + LiCO ₃ → R _f COOLi + H ₂ O + CO ₂
R _f COX + 2LiOH → R _f COOLi + LiX + H ₂ O
In any case, since it is an exothermic neutralization reaction, the contact is preferably performed at a slow rate so as to avoid a rapid temperature change. As is clear from the above reaction formula, the ratio of raw materials is 1: 1 in the case of monovalent fluorine-containing carboxylic acid and lithium hydroxide or lithium carbonate, and the fluorine-containing carboxylic acid is converted to fluorine-containing carboxylic acid halide and hydroxylated. In the case of lithium, the molar ratio may be 2: 1, but either component can be used in an amount of about 50%.

  When an acidic component is added to an aqueous solution of lithium hydroxide or lithium carbonate, the pH of the reaction system approaches from neutral to neutral as the reaction proceeds, and the point at which the pH reaches 7 is regarded as the end point of this reaction. Conversely, when the lithium component is added to the acidic component, the end point of this reaction is the time when the pH is 7. Although the reaction temperature of this reaction is not limited, it is convenient to carry out at about 0-50 degreeC. Since this reaction is an exothermic reaction, it is preferable to carry out the reaction while cooling, and it is also preferable to adjust the addition amount so as not to reach a high temperature exceeding about 50 ° C. The aqueous solution of fluorine-containing lithium carboxylate produced in the container can be made into solid lithium fluorine-containing carboxylate by removing water and carbonic acid. When water and carbonic acid are removed by heating, a hydrated salt of fluorine-containing lithium carboxylate may be formed.

When R _f COX is used as a raw material, a LiX salt is by-produced. When X is a fluorine atom having the smallest molecular weight among halogen atoms, X = F is recommended because the weight of by-products is minimized. LiX can be removed as desired, but particularly stable LiF can be used without separation because it does not have a particularly adverse effect.

  When the hydrate salt is heated and dehydrated, anhydrous fluorine-containing lithium carboxylate is obtained. As the fluorine-containing lithium carboxylate, an anhydride is preferable, and it is preferable to sufficiently dehydrate the fluorine-containing lithium carboxylate before the reaction with the fluorine-containing carboxylic acid fluoride. When water is present in the reaction system, the fluorine-containing carboxylic acid fluoride is lost due to hydrolysis, and the fluorine-containing carboxylic acid and hydrogen fluoride are mixed as impurities into the reaction product, thereby hindering the purification effect of the fluorine-containing carboxylic acid anhydride. There is a fear. As a method for dehydrating the fluorine-containing lithium carboxylate, it can be carried out by heating under normal pressure or reduced pressure, but drying under reduced pressure is recommended. Dehydration at a low temperature is desirable.

In addition, as a dehydration method, a water azeotropic solvent is added to an aqueous solution in which the fluorine-containing lithium carboxylate is dissolved or a solution in which the fluorine-containing lithium carboxylate and water coexist, and water is removed by azeotropic distillation. Or a method of facilitating the evaporation of water by adding a volatile solvent that does not azeotrope with water.
As a result, it is possible to carry out the operation up to obtaining the desired product of the fluorine-containing carboxylic acid as a starting material using the fluorine-containing carboxylic acid component as a starting material, and the reaction operation is easy and the product is not lost. There is an effect that there are few. Solvents added at this time include chloroform, carbon tetrachloride, 1,2-dichloroethane, 1,2-dichloroethylene, halogenated hydrocarbons such as 1,1,2-trichloroethane, benzene, toluene, ethylbenzene, m-xylene, etc. Aromatic hydrocarbons, aliphatic hydrocarbons such as pentane, hexane, cyclohexane, heptane, ketone solvents such as acetone, ethyl methyl ketone, 3-methyl-butanone, cyclohexanone, and nitriles such as acetonitrile, propionitrile, butyronitrile Multicomponent azeotrope can also be used. In particular, dehydration by a Dean-Stark apparatus using toluene as an azeotropic solvent is simple.

  The solvent remaining in the reaction vessel after dehydration can be reacted by introducing fluorine-containing carboxylic acid fluoride while leaving the solvent in the vessel, but it is preferably distilled off. Regardless of whether or not the solvent is removed, the fluorine-containing lithium carboxylate dehydrated in the container can be subsequently reacted with the fluorine-containing carboxylate fluoride in the container. Is a preferred embodiment.

  In the method of the present invention, the fluorine-containing lithium carboxylate and the fluorine-containing carboxylate fluoride are 1: 1 reaction, and therefore it is economically preferable to equimolar, but the fluorine-containing lithium carboxylate is contained with respect to 1 mol of the fluorine-containing lithium carboxylate. The fluorine carboxylic acid fluoride can be in the range of about 0.5 to 2. Such a range can be taken to facilitate purification by allowing one of the raw materials to be substantially completely consumed. For example, when the fluorine-containing carboxylic acid fluoride is deliberately less than 1 mol, the remaining reactive fluorine-containing carboxylic acid fluoride in the reaction product can be reduced, and the separation operation can be omitted. Moreover, the effective utilization of the fluorine-containing lithium carboxylate obtained through a multistep process can be aimed at by making fluorine-containing carboxylic acid fluoride over 1 mol.

  The reaction between the fluorine-containing lithium carboxylate and the fluorine-containing carboxylate fluoride is carried out at a reaction temperature of −78 to 120 ° C., preferably −20 to 100 ° C., more preferably 20 to 80 ° C. If it is less than −78 ° C., a special apparatus is required for cooling, and if it exceeds 120 ° C., the generated fluorine-containing carboxylic acid is not preferable because impurities are generated as decomposition. The reaction pressure varies depending on the reaction temperature and the type of fluorine-containing carboxylic acid fluoride, but is 0.1 to 20 MPa. In addition, when a solvent is used, it is also affected by the boiling point of the solvent, and by providing a condensation reflux tower in the reactor, the pressure can be reduced or a normal pressure reaction can be performed. The reaction time depends on the reaction temperature, the apparatus scale, and the presence or absence of a solvent, but is usually about 10 minutes to 30 hours, and about 30 minutes to 10 hours is preferred from the viewpoint of throughput and ease of operation.

  This reaction may be performed using a solvent, but proceeds without using a solvent. As the solvent, any solvent may be used as long as it is inert to this reaction, and N, N-dimethylformamide, morpholine, polyglyme and the like can be used in addition to those exemplified as those suitable for azeotropic dehydration of the water described above.

  Although the method of this reaction may be a flow type or a batch type, it is usually preferred to use a batch type tank reactor. The reactor is preferably stainless steel, Monel (registered trademark), Inconel (registered trademark), Hastelloy (registered trademark), fluororesin, or a container lined with these. Since difluoroacetic acid fluoride has a boiling point of 2 ° C., it is preferably a pressure-resistant vessel that can be sealed, or preferably provided with means for preventing distillation such as a reflux tower.

  At the completion of this reaction, the reaction system contains anhydrous fluorine-containing carboxylic acid and lithium fluoride. In addition, unreacted fluorine-containing carboxylic acid or fluorine-containing carboxylic acid fluoride, and side-reaction fluorine-containing carboxylic acid are contained. May be included. Anhydrous fluorinated carboxylic acid can be obtained by distilling the mixture. At this time, vacuum distillation that can be distilled at a low temperature is suitable. It is also preferable to use an excessive amount of fluorine-containing carboxylic acid fluoride in order to reduce the content of unreacted fluorine-containing lithium carboxylate. Since the unreacted fluorinated carboxylic acid used in excess can be easily recovered by distillation, it can be used again in this reaction with or without purification. Since the fluorinated carboxylic acid is caused by the presence of water in the reaction system, it is preferable to prevent water from entering the system before, during and after the reaction. The fluorine-containing carboxylic acid recovered by distillation can be used as a raw material for the fluorine-containing lithium carboxylate. Lithium fluoride can be purified and used as a battery material, a raw material for optical crystals, and the like.

  Next, the method of the present invention will be described from the step of synthesizing a fluorine-containing lithium carboxylate using a fluorine-containing carboxylate fluoride and lithium hydroxide as raw materials to the step of obtaining an anhydrous fluorine-containing carboxylic acid. It can also be obtained and used separately.

  Charge lithium hydroxide and water into a corrosion-resistant material such as resin or a container lined with them. At least a part of the lithium component is dissolved in water. An organic solvent may be added together with water, and the solvent is not particularly limited, but a solvent used for azeotropic distillation such as toluene described above is preferable. In order to dissolve and disperse, stirring with a stirring blade or the like is also possible. While stirring, fluorine-containing carboxylic acid fluoride is gradually introduced so that there is no significant increase in temperature. After the reaction is completed in a short time, if not added so far, an azeotropic solvent such as toluene is added and azeotropic distillation is performed to remove water in the reactor. If it is subjected to the next reaction without dehydration, it will be avoided because hydrolysis of the fluorine-containing carboxylic acid fluoride introduced in the next step occurs to cause a side reaction in which fluorine-containing carboxylic acid is generated.

  After dehydration, the fluorine-containing lithium carboxylate and the azeotropic solvent remaining in the reactor may be used in the next step as they are, or the azeotropic solvent may be distilled off to leave only the fluorine-containing lithium carboxylate, In order to facilitate final purification, it is preferred to remove the azeotropic solvent. In any case, the fluorine-containing carboxylic acid fluoride is introduced therein and brought to a predetermined temperature, whereby the anhydrous fluorine-containing carboxylic acid is generated. If the reactor is cooled when the fluorine-containing carboxylic acid fluoride is charged to the reactor, the operation is easy, but it is also possible to carry in while feeding at room temperature (about 25 ° C.) or at the reaction temperature. After a predetermined reaction time has elapsed, the reactor is cooled and the contents are taken out, whereby an anhydrous fluorine-containing carboxylic acid is obtained as a reaction product. In the case of a product having a relatively low boiling point, the purity of the anhydrous fluorine-containing carboxylic acid can be improved by distillation. When unreacted fluorine-containing lithium carboxylate remains, it is preferable to use vacuum distillation.

  Hereinafter, although an example explains the present invention, the present invention is not limited to these embodiments.

[Example 1]
Anhydrous lithium difluoroacetate (CHF ₂ COOLi, 4.56 g, 0.053 mol) was charged into a 50 cc stainless steel reactor, the reactor was closed, and then cooled to −78 ° C. with a dry ice / acetone bath and decompressed. Difluoroacetic acid fluoride (CHF ₂ COF, 2.62 g, 0.027 mol) was added while stirring, the bath was removed, and the temperature was returned to room temperature (about 25 ° C.). Thereafter, the oil bath was replaced, and stirring was continued at 80 ° C. for 3 hours. Vacuum distilling gave crude difluoroacetic anhydride (4.54 g) in 93.9% yield (CHF ₂ COF basis). The composition is (CHF ₂ CO) ₂ O: 96.2 area%, CHF ₂ COF: 1.9 area%, CHF ₂ COOH (difluoroacetic acid): 1.1 area%, others: 0.8 area% there were.

[Example 2]
In a 1500 cc fluororesin-lined autoclave equipped with a blowing tube, thermometer, pressure gauge, stirrer, and Dean Stark device, lithium hydroxide monohydrate (LiOH.H ₂ O, 41.96 g, 1 mol) and 360 g of ions The exchanged water was charged and cooled with ice while stirring. While maintaining the internal temperature at 15 ° C. or lower, CHF ₂ COF was gradually supplied through the blowing tube, and the pH was measured successively. When the pH reached 7, the supply of CHF ₂ COF was stopped (CHF ₂ COF supply amount: 48.7 g, 0.50 mol). Next, 500 cc of toluene was added thereto, and azeotropic dehydration using water / toluene as a fraction was performed. After the water recovery in the Dean-Stark apparatus was substantially finished, the entire amount of toluene was distilled off by vacuum flash distillation. After completion of the distillation, the autoclave was depressurized and cooled with a dry ice / acetone bath. Here, after introducing CHF ₂ COF (48.7 g, 0.50 mol) from the blowing tube, the bath was removed. When the internal temperature reached 0 ° C., it showed almost normal pressure (about 0.0 MPaG. “G” represents gauge pressure. The same applies hereinafter.), Then heated in an oil bath at 80 ° C. and stirred for 3 hours. (Maximum pressure: 0.16 MPaG). The contents were collected by vacuum flash and volatiles (70.8 g) were collected in a separate stainless steel container. When analyzed by a gas chromatograph (FID detector), (CHF ₂ CO) ₂ O: 81.4 area%, CHF ₂ COF: 13.4 area%, CHF ₂ COOH (difluoroacetic acid): 7.1 area%, Other: 1.9 area%.

[Reference Example 1]
Ion exchange water (0.9 g, 0.05 mol) was charged into a 50 cc stainless steel reactor, the reactor was closed, cooled to −78 ° C. with a dry ice / acetone bath, and then decompressed. After introducing CHF ₂ COF (9.8 g, 0.10 mol), the mixture was returned to room temperature (about 25 ° C.) with stirring. After changing the bath to an oil bath and stirring at a bath temperature of 80 ° C. for 8 hours (maximum pressure: 1.05 MPaG), cooling with ice water and analyzing the contents by GC, formation of (CHF ₂ CO) ₂ O was observed. There wasn't.

[Reference Example 2]
Potassium difluoroacetate (CHF ₂ COOK, 1.52 g, 0.0113 mol) prepared by neutralizing commercially available difluoroacetic acid with an aqueous potassium hydroxide solution, drying with a rotary evaporator, and further drying under reduced pressure at 1 kPa (absolute pressure) The reactor was charged into a 50 cc stainless steel reactor, and after closing the reactor, the pressure was reduced by cooling to −78 ° C. with a dry ice / acetone bath. CHF ₂ COF (1.9 g, 0.0194 mol) was added with stirring, the bath was removed, and the temperature was returned to room temperature (about 25 ° C.). Thereafter, the oil bath was replaced, and stirring was continued at 80 ° C. for 8 hours (maximum pressure: 0.95 MPaG). The solid was left by flash distillation, and the volatiles were transferred to another stainless steel container and analyzed by a gas chromatograph (FID detector). As a result, only CHF ₂ COF was detected, and (CHF ₂ CO) ₂ O was not recognized. . When the residue of the reactor was analyzed by infrared absorption spectroscopy (IR), it showed almost the same spectrum as the raw material CHF ₂ COOK.

  It is useful as a method for producing an anhydrous fluorine-containing carboxylic acid that is useful as an intermediate for medical and agricultural chemicals and functional materials.

Claims (7)

General formula (1)
R _f COOLi (1)
(Wherein R _f represents a fluorine-containing alkyl group) and a fluorine-containing lithium carboxylate represented by the general formula (2)
R _f COF (2)
(Wherein R _f represents the same group as the group in the general formula (1)). The general formula (3) comprising reacting the fluorine-containing carboxylic acid fluoride represented by the general formula (3)
(R _f CO) ₂ O (3)
(In the formula, R _f represents the same group as the group in the general formula (1)). The fluorine-containing lithium carboxylate has the general formula (4)
R _f COX (4)
(In the formula, R _f represents the same group as the group in the general formula (1), X represents F, Cl, Br, or I). The fluorine-containing carboxylic acid halide represented by lithium hydroxide is reacted with lithium hydroxide. The method for producing an anhydrous fluorine-containing carboxylic acid according to claim 1, wherein the fluorine-containing lithium carboxylate is obtained. The fluorine-containing lithium carboxylate has the general formula (5)
R _f COOH (5)
(In the formula, R _f represents the same group as the group in the general formula (1).) The fluorine-containing lithium carboxylate obtained by reacting the fluorine-containing carboxylic acid represented by lithium hydroxide or lithium carbonate. A method for producing an anhydrous fluorine-containing carboxylic acid according to claim 1 or 2. A step of synthesizing a fluorine-containing lithium carboxylate by a method of reacting a fluorine-containing carboxylic acid halide and lithium hydroxide, or a method of reacting a fluorine-containing carboxylic acid and lithium hydroxide or lithium carbonate; The method for producing an anhydrous fluorine-containing carboxylic acid according to claim 1, wherein the step of reacting with acid fluoride is performed using the same container. The step of synthesizing the fluorine-containing lithium carboxylate, the step of removing water accompanying the fluorine-containing carboxylic acid using azeotropic distillation, and the step of reacting the fluorine-containing lithium carboxylate and the fluorine-containing carboxylic acid fluoride are the same. The manufacturing method of the anhydrous fluorine-containing carboxylic acid of Claim 4 performed using the container of. In general formula (1), _Rf is a difluoromethyl group or a trifluoromethyl group, The manufacturing method of the anhydrous fluorine-containing carboxylic acid of any one of Claims 1-5. The method for producing an anhydrous fluorine-containing carboxylic acid according to any one of claims 1 to 6, wherein the reaction between the fluorine-containing lithium carboxylate and the fluorine-containing carboxylic acid fluoride is carried out at a reaction temperature of -78 to 120 ° C.