Method for purifying carboxylic acid fluoride

Abstract

Provided is a method for stably providing a high purity R-COF product, the method configured so that a reduction in R-COF yield caused by contamination by impurities is prevented.　According to the present invention, provided are: a method for purifying a carboxylic acid fluoride, the method including a step for bringing a hydrogen halide-containing carboxylic acid fluoride into contact with a metal fluoride so as to remove the hydrogen halide; a method for producing a high purity carboxylic acid fluoride, the method including a step for bringing a hydrogen halide-containing carboxylic acid fluoride into contact with a metal fluoride; a high-purity carboxylic acid fluoride obtained using this method; and a method for using a metal fluoride as a hydrogen halide adsorbent in a method for removing a hydrogen halide from a hydrogen halide-containing carboxylic acid fluoride.

Description

[Technical field]

[0001] The present invention relates to a method for purifying carboxylic acid fluoride (R-COF, where R is a monovalent organic group, a hydrogen atom, or a halogen atom).The present invention also relates to a high-purity R-COF and a method for producing the same. [Background technology]

[0002] It is known that R-COF compounds (particularly COF2) are difficult to separate from hydrogen halides (particularly HF) by distillation, and purification requires a lot of time and cost. Patent Document 1 discloses that a gas mixture containing HF, HCl and / or HBr and other components, particularly a gas mixture containing carboxylic acid fluoride, COF2 or phosphorus pentafluoride, HCl, and possibly HF, can be fractionated using an ionic liquid. However, the purification method of Patent Document 1 has a problem that an expensive ionic liquid is required, and even if the ionic liquid is passed through, HCl remains in the purified product at a percentage level. Patent Document 2 discloses a method for separating an acid from a system in which an organic acid fluoride and an acid are mixed, characterized in that an aromatic heterocyclic compound having a boiling point of 50°C or higher and having a nitrogen atom as a heteroatom is used as a deoxidizer. However, this method has a problem that the aromatic heterocyclic compound is entrained in the gas flow, which interferes with ultra-high purification.

[0003] On the other hand, there are reports of specific cases where the existence of complexes between R-COF and hydrogen halides has been found. Non-Patent Document 1 discloses a complex between CH3COF and HI. However, there have been few reports on such complexes, and it cannot be said that there is sufficient knowledge about them. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5473222 (Patent Application No. 2007-538309) [Patent Document 2] Patent No. 4264689 (Patent Application No. 2001-396680) [Non-patent literature]

[0005] [Non-Patent Document 1] J.Phys.Chem.A,Vol.101,No.49,1997,p.9260-9271 Summary of the Invention [Problem to be solved by the invention]

[0006] Through intensive research by the present inventors, it has been confirmed that R-COF and hydrogen halide (HX) form a complex. Such a complex is represented, for example, by the formula: R-COF-HX (X=F, Cl, Br, I). Since it is difficult to separate R-COF from this complex, for example, the following halogen exchange reaction: R-COX 1 + HF → R-COF + HX 1 (In the formula, R is a monovalent organic group, a hydrogen atom, or a halogen atom; X 1 is a halogen atom other than fluorine) Since the reaction product contains the R-COF-HX complex, even if the synthesis yield before purification (crude yield) is high, the yield of R-COF by distillation (distillation yield) is reduced because the first distillation cut is performed to remove impurities (reduced distillation yield). Furthermore, when the aim is to produce ultra-high purity R-COF with a purity of 5N (99.999% or more but less than 99.9999%) or more, it has not been possible to produce such an ultra-high purity product using conventional purification methods (hinderance to achieving ultra-high purity). Therefore, the object of the present invention is to prevent the reduction in the yield of R-COF due to the inclusion of impurities and to stably produce high purity R-COF. [Means for solving the problem]

[0007] As a result of intensive research, the present inventors have found that the use of a metal fluoride as a hydrogen halide adsorbent can efficiently decompose the R-COF-HX complex, thereby improving the yield of the R-COF compound and achieving ultra-high purity. [1] A method for purifying a carboxylic acid fluoride, comprising the step of contacting a carboxylic acid fluoride containing a hydrogen halide with a metal fluoride to remove the hydrogen halide. [2] A method for producing a high purity carboxylic acid fluoride, comprising the step of contacting a carboxylic acid fluoride containing a hydrogen halide with a metal fluoride. [3] A method for removing hydrogen halide from a carboxylic acid fluoride containing hydrogen halide, comprising the step of using a metal fluoride as a hydrogen halide adsorbent. [4] Carboxylic acid fluorides containing hydrogen halides can be reacted with the following halogen exchange reaction: R-COX 1 + HF → R-COF + HX 1 (In the formula, R is a monovalent organic group, a hydrogen atom, or a halogen atom; X 1 is a halogen atom other than fluorine) The method according to any one of [1] to [3], wherein the reaction product is a reaction product of [5] The method according to any one of [1] to [3], wherein the carboxylic acid fluoride containing hydrogen halide is a reaction product of a reaction between a carboxylic acid chloride and a metal fluoride. [6] The method according to any one of [1] to [3], wherein the carboxylic acid fluoride containing hydrogen halide is a reaction product of a reaction between a carboxylic acid chloride and chromium fluoride. [7] The method according to any of [1] to [6], wherein the hydrogen halide is at least one selected from the group consisting of hydrogen fluoride and hydrogen chloride. [8] The method according to any of [1] to [7], wherein the metal fluoride in the step of removing hydrogen halide is sodium fluoride. [9] The method according to any one of [1] to [8], wherein the carboxylic acid fluoride is trifluoroacetic acid fluoride.

[10] Carboxylic acid fluoride with a purity of 99.999% or more.

[11] Trifluoroacetic acid fluoride with a purity of 99.999% or more. Effect of the Invention

[0008] According to the present invention, it is possible to prevent a decrease in the yield of R-COF due to the inclusion of impurities, and to stably produce high-purity R-COF. In particular, according to the present invention, it is possible to produce ultra-high purity R-COF that reaches a purity of 5N (99.999% or more and less than 99.9999%) or more, which could not be obtained by conventional purification methods. By using the ultra-high purity R-COF obtained by the present invention in the semiconductor manufacturing process, etching can be performed more precisely than ever before, improving the etching performance of the process. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a GC-TCD chart of a mixture of CF3COF and HCl. [Diagram 2] FIG. 2 shows a GC-MS chart of CF3COF alone (top), which was obtained separately, and a GC-MS chart of the peak adjacent to the HCl peak in FIG. 1 (bottom). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] [Effect] As described later, the present inventors have found that, in obtaining an ultra-high purity product of R-COF, R-COF forms a complex with hydrogen halide, and this complex makes it difficult to remove the hydrogen halide. In the example described later in the Examples section, in which only distillation was performed, the initial cut was increased due to HCl, which is thought to be reversibly released from the CF3COF-HCl complex, and the distillation yield was reduced. In addition, even after distillation purification, the CF3COF-HCl complex could not be removed, and ultra-high purification could not be achieved. In addition, in order to increase the purity as much as possible, the low boiling point cut and the initial retention time were prolonged, and productivity was reduced. The present inventors have found that the formation of this complex can be prevented by using a metal fluoride. According to the present invention, it is possible to avoid the method of using an ionic liquid or an aromatic heterocyclic compound for removing acids from R-COF compounds, which has been proposed in the past. In addition, according to the present invention, hydrogen halides (especially HCl and HF), which are difficult to separate from R-COF by distillation, can be removed by a relatively simple operation of passing them through a metal fluoride as a hydrogen halide adsorbent. Moreover, the existence of the above complex was discovered and successfully removed, making it possible for the first time to produce ultra-high purity R-COF with a purity of 5N or higher.

[0011] [Carboxylic acid fluorides (R-COF)] Carboxylic acid fluoride, which is the target of the purification method of the present invention, is represented by the formula: R-COF (wherein R is a monovalent organic group, a hydrogen atom, or a halogen atom). Examples of the halogen atom in R include fluorine (F), chlorine (Cl), bromine (Br), and iodine (I). Examples of the monovalent organic group include an alkyl group having 1 to 6 carbon atoms, particularly an alkyl group having 1 to 4 carbon atoms, particularly an alkyl group having 1 to 4 carbon atoms, such as a methyl group, an ethyl group, a propyl group (particularly an n-propyl group and an isopropyl group), and a butyl group (particularly an n-butyl group, an isobutyl group, and a tertiary butyl group); an aryl group (particularly a phenyl group and a tolyl group), and an arylalkyl group (particularly a benzyl group and a phenethyl group); and the like. The monovalent organic group may be substituted with a halogen atom, an alkoxy group, or the like. Examples of the substituted organic group include perfluoroalkyl groups such as a difluoromethyl group, a trifluoromethyl group, a pentafluoroethyl group, and a heptafluoropropyl group, alkoxyalkyl groups such as a methoxymethyl group, and alkoxyaryl groups such as a methoxyphenyl group.

[0012] More specifically, the carboxylic acid fluoride may be, for example, a carboxylic acid fluoride having 1 to 7 carbon atoms, preferably a carboxylic acid fluoride having 2 to 7 carbon atoms. Examples of the carboxylic acid having 1 to 7 carbon atoms include formic acid, acetic acid, propanoic acid, n-butanoic acid, isobutanoic acid, n-pentanoic acid, isopentanoic acid, neopentanoic acid, n-hexanoic acid, isohexanoic acid, neohexanoic acid, n-heptanoic acid, isoheptanoic acid, neoheptanoic acid, and combinations of these carboxylic acids. The hydrogen atoms on the carboxylic acid may be substituted with fluorine, and preferably, the hydrogen atoms are all substituted with fluorine atoms in the perfluorocarboxylic acid fluoride. Specific examples of the carboxylic acid fluoride include difluoroacetic acid fluoride (CHF2COF), trifluoroacetic acid fluoride, perfluoro n-butanoic acid fluoride, and perfluoro n-heptanoic acid fluoride.

[0013] [Metal Fluorides] The metal fluoride used as the hydrogen halide adsorbent has the formula: MFn (wherein M is a metal atom, and n is the valence of the metal). Examples of metal fluorides include alkali metal fluorides, alkaline earth metal fluorides, transition metal fluorides, etc., and these may be a combination of two or more. Examples of alkali metal fluorides include lithium fluoride, sodium fluoride, potassium fluoride, etc. Examples of alkaline earth metal fluorides include magnesium fluoride, calcium fluoride, barium fluoride, etc. Examples of transition metal fluorides include chromium fluoride, molybdenum fluoride, manganese fluoride, iron fluoride, cobalt fluoride, copper fluoride, nickel fluoride, zinc fluoride, silver fluoride, etc. Examples of chromium fluoride include chromium fluoride (III), chromium fluoride (VI), and mixtures thereof. As the molybdenum fluoride, any of molybdenum fluoride (IV), molybdenum fluoride (V), molybdenum fluoride (VI) and mixtures thereof can be used. As the manganese fluoride, any of manganese fluoride (II), manganese fluoride (III), manganese fluoride (IV) and mixtures thereof can be used. As the iron fluoride, any of iron fluoride (II), iron fluoride (III) and mixtures thereof can be used. As the cobalt fluoride, any of cobalt fluoride (II), cobalt fluoride (III) and mixtures thereof can be used. As the copper fluoride, any of copper fluoride (I), copper fluoride (II) and mixtures thereof can be used. As for nickel fluoride and zinc fluoride, divalent metal fluorides are stable. As the silver fluoride, any of silver fluoride (I), silver fluoride (II), silver fluoride (III) and mixtures thereof can be used. Considering cost and convenience, alkali metal fluorides such as sodium fluoride and potassium fluoride are particularly preferred.

[0014] The metal fluoride can be used as a powder, or in the form of pellets (cylindrical) (e.g., particle size 0.5-30 mm), honeycomb, granular (spindle) (e.g., particle size 0.5-30 mm), spherical (e.g., particle size 0.5-30 mm), or other lumps other than powder. The advantage of using the metal fluoride in a form other than powder is that, for example, the problem of the reaction efficiency being reduced due to the formation of a flow path for the raw material gas caused by the solidification of the metal fluorides themselves is unlikely to occur. The filling rate of the metal fluoride in the reactor is preferably 30% by volume or more, more preferably 33% by volume or more, and most preferably 60% by volume or more. Since a molded product (e.g., pellets) of the metal fluoride usually has pores or gaps, gas can pass through even if the filling rate is 100% by volume.

[0015] [Purification method] The purification method of the present invention includes a step of contacting a carboxylic acid fluoride containing hydrogen halide with a metal fluoride to remove the hydrogen halide. Specifically, for example, a complex between R-COF and HX in the carboxylic acid fluoride is decomposed by passing the carboxylic acid fluoride (R-COF) containing hydrogen halide (HX) through a metal fluoride packed tower, and the R-COF gas separated from HX is further purified by distillation to obtain a high-purity product. The temperature of the packed tower during purification is preferably 15 to 35°C, and most preferably performed at room temperature (particularly, 10 to 30°C). The hydrogen halide attached to the metal fluoride can be removed by drying at a high temperature under a nitrogen atmosphere, so that the metal fluoride can be repeatedly regenerated and used by performing this operation.

[0016] Examples of the metal fluoride packed tower include a cylindrical tube equipped with a temperature regulator (used as a heater during drying or regeneration of metal fluoride) for adjusting the purification temperature, filled with metal fluorides of various shapes, and configured to allow raw material gas to flow from one end of the tube to the other end. When the cylindrical tube loaded with metal fluoride is extended vertically, the raw material gas is preferably flowed uniformly from top to bottom little by little, since the raw material gas can be flowed little by little by utilizing gravity. When the cylindrical tube is extended vertically and the raw material gas is flowed from bottom to top, it is desirable in terms of adsorption efficiency to place metal fluoride pellets with large particle size at the bottom of the cylindrical tube and metal fluoride powders with small particle size at the top of the cylindrical tube. Examples of materials for the reaction apparatus include corrosion-resistant metals such as stainless steel, Inconel, Monel, Hastelloy, and nickel. Among these, stainless steel and nickel are preferable in terms of corrosion resistance.

[0017] Particularly preferred examples of the subject of purification include the following: (1) A halogen exchange reaction according to the following formula: R-COX 1 + HF → R-COF + HX 1 (In the formula, R is a monovalent organic group, a hydrogen atom, or a halogen atom; X 1 is a halogen atom other than fluorine) The reaction products R-COF and HX 1 Here, since the reaction product also contains unreacted HF, the target of purification is actually R-COF and HX. (2) Examples of reaction products include those obtained by the reaction of carboxylic acid chlorides with metal fluorides. Examples of carboxylic acid chlorides include the above-mentioned compounds (R-COCl) in which the -COF part of the carboxylic acid fluoride (R-COF) is -COCl, and examples of metal fluorides include the above-mentioned compounds. Specific examples include those represented by the following formula: 3 R-COCl + CrF3→ 3 R-COF + CrCl3 In this reaction, in theory, Cl involved in the reaction is removed as CrCl3, so there is no HCl in the reaction system and the complex should not be formed, but in reality, small amounts of HF and HCl are present. This is because CrF3 is converted from CrCl3 produced by the reaction into the following formula: CrCl3+HF → CrF3+HCl This is because HF is used to regenerate CrF3, which produces HCl as a by-product. This regenerated CrF3 is reused as a reactant for R-COF synthesis. Cr can be supported on activated carbon and used as a supported catalyst. When used as a supported catalyst, it is thought that the fluorinating agent (HF) used in the regeneration reaction and the by-product HCl are more likely to be adsorbed and remain in the activated carbon. (3) This is a reaction product in the method of producing CF3COF by photo-oxidation of CF3CHClF. For example, CF3CHClF is irradiated with ultraviolet light from a UV lamp and oxidized to synthesize it. At this time, oxygen is added as a reactant and Cl2 (catalytic amount) is added as a radical initiator. The reaction formula is as follows. 2CF3CHClF + O2→ 2CF3COF + 2HCl Therefore, HCl is present in the crude product after the reaction. (4) This is a reaction product in the process of producing CF3COF by oxidizing and thermally decomposing CF3CF=CF2. For example, O2 is used as a reactant, and AgNO3 and Ag2O are used as catalysts. The thermal decomposition temperature is about 250°C. The reaction formula is as follows: CF3CF=CF2+ O2→ CF3COF + COF2 This method relies on thermal decomposition, so impurities such as hydrogen halides are easily produced in the crude product due to moisture mixed into the reaction system. (5) Regardless of the synthesis method of R-COF, R-COF is inherently very susceptible to hydrolysis and is prone to contain HF (hydrogen halide) over time. If the hydrogen halide generated by such aging is complexed with R-COF, it is not possible to ultra-purify R-COF using conventional methods. In this specification, a mixture of CF3COF and HCl and / or HF is given as an example of a substance that is particularly difficult to separate.

[0018] [Ultra-high purity R-COF and its manufacturing method] By utilizing the purification method of the present invention, ultra-high purity carboxylic acid fluoride with a purity of 99.999% or more can be produced. Conventionally, such ultra-high purity carboxylic acid fluoride could not be obtained even by performing precise distillation because the complex between carboxylic acid fluoride and hydrogen halide could not be separated. In the present invention, a step of contacting carboxylic acid fluoride containing such a complex with a metal fluoride (for example, a step of passing through a metal fluoride packed tower) is first performed, and the carboxylic acid fluoride purified product from which the complex that is difficult to separate is removed is distilled to remove other impurities, thereby realizing ultra-high purity carboxylic acid fluoride with a purity of 99.999% or more. The order of passing through the metal fluoride packed tower and the distillation tower is not particularly limited, and it is also possible to pass through the distillation tower first and then pass through the metal fluoride packed tower.

[0019] [Ultra-high purity R-COF applications] The ultra-high purity R-COF produced by the present invention is substantially free of impurities, enabling precise chemical reactions in semiconductor manufacturing processes, such as etching and deposition at the atomic layer level. EXAMPLES

[0020] [Confirmation of CF3COF-HCl complex] The present inventors have found that a CF3COF-HCl complex is formed when CF3COF is brought into contact with HCl. FIG. 1 shows a GC-TCD chart of a mixture of CF3COF and HCl. FIG. 2 shows a GC-MS chart (top) of CF3COF alone, which was obtained separately, and a GC-MS chart (bottom) of a peak adjacent to the HCl peak in FIG. 1. As can be seen from FIG. 2, the peak adjacent to the HCl peak in FIG. 1 presents a spectrum obtained by adding a peak of molecular weight 36 corresponding to HCl to the GC-MS chart (top) of CF3COF, which was obtained separately, and therefore it was confirmed that the peak adjacent to the HCl peak in FIG. 1 is an association (complex) of CF3COF and HCl.

[0021] [Example 1] NaF pellets (dimensions: 3 mm diameter × 3 mm cylindrical, bulk density: 1.55 g / cm) were placed in a stainless steel reaction tube with a punched metal at the bottom to prevent the NaF pellets from falling. 3 The specifications of the NaF tower are shown in Table 1, and the HF and HCl removal performance of the NaF tower are shown in Table 2.

[0022] [Table 1] In Table 1 above, the residence time T1 is V / F (total volume (L) of gas passing through the tower / flow rate (L / min)).

[0023] [Table 2] From Tables 1 and 2, it was confirmed that NaF pellets were capable of adsorbing HF and HCl.

[0024] The feed gas (material to be purified) is the reaction product (solid phase reactor crude gas) prepared by the following method. Preparation of trifluoroacetic acid fluoride (CF3COF) using CrF3 / C: A SUS scrubbing pad was placed at the bottom of a 2B vertical SUS reactor, and 17-33 mass% CrF3 / C was loaded on top of the SUS scrubbing pad. The reactor was heated to 200-350°C. Trifluoroacetic acid chloride (CF3COCl(TFAC)) was passed through, and the production of CF3COF was confirmed by GC analysis of the outlet gas. A 500 mL cylinder was cooled with liquid nitrogen, and the produced CF3COF was collected. HCl and HF were present in the CF3COF gas, which was the reaction product.

[0025] The following three types of gases containing R-COF-HX complexes were prepared using the above CF3COF gas: (1) Distillate of a mixture of CF3COF and HCl (molar ratio 1:1) (without aeration to the NaF column before distillation) (2) Distillate of a mixture of CF3COF and HCl (approximately 1000 ppm) (when not vented to the NaF column before distillation) (3) Distillate of a mixture of CF3COF and HCl (approximately 1000 ppm) (when the above NaF column is aerated before distillation) The results were analyzed by GC and FT-IR. The gas flow rate was controlled by a mass flow controller (MFC) during the test.

[0026] (NaF tower passage conditions) NaF pellets (dimensions (3 mm diameter × 3 mm cylindrical, bulk density 1.55 g / cm)) were placed in a stainless steel reactor with a punching metal at the bottom to prevent the NaF pellets from falling. 3 The reactor was placed vertically and gas was passed through the reactor from top to bottom under the following conditions, and the gas was then fed to the distillation column in the next step. Temperature: 15~35℃ Pressure: 0~0.2MPaG (gauge pressure) Flow rate: 2~4kg / hr

[0027] (Distillation conditions) Pot / tower pressure: 0 to 0.2 MPaG (gauge pressure) Pot / tower top temperature: -40℃~-100℃ Fraction withdrawal flow rate: 0.1kg~2kg The results are shown in Tables 3 to 5.

[0028] [Table 3] The definitions of each fraction shown in the table are as follows: First distillate: Distillate containing HCl before the main distillate (distillate with a high content of low boiling point substances) Main fraction: fraction with purity between 90% and 99% (1N) Tail fraction: Fraction containing HCl after main fraction (fraction containing a lot of high boiling point substances) Bottoms: Fractions that cannot be recovered in the tail distillate during normal operation and are removed by heating the tower, etc. (Fractions containing a large amount of high boiling point substances) In the table, "ND" means "not detected." It took 175g of initial distillation to remove HCl. CF3COF and the CF3COF-HCl complex could not be separated, and the CF3COF-HCl complex was mixed into the main distillation. The product could not be purified to a high degree, remaining at 1N (purity 90% to less than 99%). If the concentration of HCl is high during charging, HCl will also be mixed into the later distillation. It is believed that the HCl contained in the later distillation was released from the complex.

[0029] [Table 4] The definitions of each fraction shown in the table are as follows: First distillate: Distillates with a purity of 99.9% or more but less than 99.99% before the main distillation (distillates with a high content of low boiling point substances) Main fraction: fraction with purity of 99.9% or more but less than 99.99% Rear distillate: A fraction with a purity of less than 99.9% after the main distillation (a fraction containing a large amount of high boiling point substances), and no fraction corresponding to the rear distillation was obtained. Bottoms: Fractions that cannot be recovered in the tail distillate during normal operation and are removed by heating the tower, etc. (Fractions containing a large amount of high boiling point substances) In the table, "ND" means "not detected." The actual purity of the main fraction was 3N (99.9888%), taking into account the gas (N2 + CO) that was difficult to remove by distillation, and this was 4N (99.99% or more, but less than 99.999%) when calculated excluding (N2 + CO). However, a high-purity product (5N (99.999% or more, but less than 99.9999%)) was not obtained. In addition, when recovering the first fraction, 29.9 kg of the first fraction was required due to HCl that was thought to be released from the CF3COF-HCl complex. A purity of 5N or more could not be achieved by distillation, and the time for cutting low boiling points and the first fraction was prolonged, resulting in a decrease in productivity (amount of the main fraction).

[0030] [Table 5] The feed gas was introduced into the distillation column in three separate portions (feeds 1 to 3) before the start of distillation. The definitions of each fraction shown in the table are as follows: First distillate: Distillate with a purity of 3N (purity between 99.9% and 99.99%) before the main distillation (distillate with a high content of low boiling point substances) Main fraction: fraction with a purity of 5N (purity of 99.999% or more but less than 99.9999%) Tail fraction: Since a large amount of the main fraction was recovered, no fraction corresponding to the tail fraction was obtained. Bottoms: Fractions that cannot be recovered in the tail distillate during normal operation and are removed by heating the tower, etc. (Fractions containing a large amount of high boiling point substances) In the table, "ND" means "not detected." By aerating the NaF column before distillation, the CF3COF-HCl complex was decomposed, and high-purity CF3COF with no detectable HCl was distilled, achieving ultra-high purification by distillation.

[0031] From Table 3, it was found that when the CF3COF-HCl complex is mixed, not only is the initial cut large and the productivity low, but it is also difficult to highly purify CF3COF by distillation. From Table 4, it was found that even if the amount of HCl is small, a considerable amount of the initial cut is required due to the formation of the CF3COF-HCl complex and the released HCl, and it is also difficult to achieve ultra-high purification of CF3COF. From Table 5, it was found that by contacting the gas containing the CF3COF-HCl complex with NaF, the complex which is difficult to separate by distillation is decomposed, the initial cut is small, the productivity is high, and the ultra-high purification of CF3COF is achieved. In the main fraction in the example of the present invention, a purity of CF3COF exceeding 99.999% is achieved.

Claims

1. A method for purifying a carboxylic acid fluoride, comprising the steps of contacting a carboxylic acid fluoride containing a hydrogen halide with a metal fluoride to remove the hydrogen halide, thereby obtaining a carboxylic acid fluoride having a purity of 99.999% or more, The step of removing hydrogen halide to obtain carboxylic acid fluoride having a purity of 99.999% or more includes passing the carboxylic acid fluoride containing hydrogen halide through a metal fluoride packed column and further purifying the carboxylic acid fluoride by distillation, the metal fluoride is sodium fluoride; The method, wherein the carboxylic acid fluoride is at least one selected from the group consisting of difluoroacetic acid fluoride (CHF 2 COF), trifluoroacetic acid fluoride, perfluoro n-butanoic acid fluoride, and perfluoro n-heptanoic acid fluoride.

2. A method for producing a carboxylic acid fluoride having a purity of 99.999% or more, comprising a step of contacting a carboxylic acid fluoride containing a hydrogen halide with a metal fluoride to remove the hydrogen halide, The step of removing hydrogen halide includes passing the carboxylic acid fluoride containing hydrogen halide through a metal fluoride packed column and further purifying the carboxylic acid fluoride by distillation; the metal fluoride is sodium fluoride; The method, wherein the carboxylic acid fluoride is at least one selected from the group consisting of difluoroacetic acid fluoride (CHF 2 COF), trifluoroacetic acid fluoride, perfluoro n-butanoic acid fluoride, and perfluoro n-heptanoic acid fluoride.

3. 1. A method for removing hydrogen halide from a carboxylic acid fluoride containing hydrogen halide to obtain a carboxylic acid fluoride having a purity of 99.999% or more, comprising the steps of: The method for removing hydrogen halide to obtain carboxylic acid fluoride having a purity of 99.999% or more includes passing the carboxylic acid fluoride containing hydrogen halide through a metal fluoride packed column and further purifying the carboxylic acid fluoride by distillation, the metal fluoride is sodium fluoride; The method, wherein the carboxylic acid fluoride is at least one selected from the group consisting of difluoroacetic acid fluoride (CHF 2 COF), trifluoroacetic acid fluoride, perfluoro n-butanoic acid fluoride, and perfluoro n-heptanoic acid fluoride.

4. A carboxylic acid fluoride containing a hydrogen halide is reacted with the following halogen exchange reaction: R-COX １ + HF → R-COF + HX １ (In the formula, R is a monovalent organic group, a hydrogen atom, or a halogen atom; X １ is a halogen atom other than fluorine) The method according to any one of claims 1 to 3, wherein the reaction product is

5. The method according to any one of claims 1 to 3, wherein the carboxylic acid fluoride containing hydrogen halide is a reaction product of a reaction between a carboxylic acid chloride and a metal fluoride.

6. The method according to any one of claims 1 to 3, wherein the carboxylic acid fluoride containing hydrogen halide is a reaction product of a reaction between a carboxylic acid chloride and chromium fluoride.

7. A method according to any one of claims 1 to 3, wherein the carboxylic acid fluoride containing hydrogen halide is a reaction product in a method for producing CF 3 COF by photo-oxidation of CF 3 CHClF by adding oxygen as a reactant and Cl 2 (catalytic amount) as a radical initiator.

8. The method according to claim 1, wherein the carboxylic acid fluoride containing hydrogen halide is a reaction product in a method for producing CF 3 COF by oxidizing and thermally decomposing CF 3 CF═CF 2 .

9. The method of claim 1, wherein the carboxylic acid fluoride is trifluoroacetic acid fluoride.

10. The method according to any one of claims 1 to 9, wherein the hydrogen halide is at least one selected from the group consisting of hydrogen fluoride and hydrogen chloride.

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