Process for the purification of carboxylic acid fluorides

Abstract

Prevention of yield reduction of R-COF due to impurity mixing, and stable production of high-purity products of R-COF. According to the present application, there are provided: a purification method of carboxylic acid fluoride, which includes a step of removing hydrogen halide by bringing carboxylic acid fluoride containing hydrogen halide into contact with a metal fluoride; a production method of high-purity carboxylic acid fluoride, which includes a step of bringing carboxylic acid fluoride containing hydrogen halide into contact with a metal fluoride; and high-purity carboxylic acid fluoride obtained by the method; and, in a method of removing hydrogen halide from carboxylic acid fluoride containing hydrogen halide, a method of using a metal fluoride as a hydrogen halide adsorbent.

Description

Technical Field

[0001] This invention relates to a method for purifying carboxyl fluoride (R-COF, where R is a monovalent organic group, a hydrogen atom, or a halogen atom). This invention also relates to high-purity R-COF and its manufacturing method. Background Technology

[0002] It is known that R-COF compounds (especially COF2) are difficult to separate from hydrogen halides (especially HF) by distillation, and purification requires a significant amount of time and expense. Patent Document 1 discloses that fractional distillation can be performed using ionic liquids for gas mixtures containing HF, HCl and / or HBr and other components, particularly those containing carboxyl fluorides, COF2 or phosphorus pentafluoride and HCl, and, if necessary, HF. However, the purification method in Patent Document 1 requires expensive ionic liquids, and even with the introduction of ionic liquids, there is a problem that HCl remains in the purified product at percentage levels. Patent Document 2 discloses a method for separating acids, characterized by separating acids from a system in which organic acyl fluorides and acids are mixed, wherein aromatic heterocyclic compounds with boiling points above 50°C and nitrogen atoms as heteroatoms are used as deoxidizers. However, this method suffers from the problem that aromatic heterocyclic compounds are mixed in with the gas flow, hindering the attainment of ultra-high purity.

[0003] On the other hand, there are reports of specific instances of the discovery of complexes between R-COF and hydrogen halides. Non-Patent Document 1 discloses a complex of CH3COF and HI. However, there are very few reports on such complexes to date, and sufficient insight cannot be said to exist.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 5473222 (Japanese Patent Application No. 2007-538309)

[0007] Patent Document 2: Japanese Patent No. 4264689 (Japanese Patent Application No. 2001-396680)

[0008] Non-patent literature

[0009] Non-patent literature 1: J. Phys. Chem. A, Vol. 101, No. 49, 1997, pp. 9260-9271 Summary of the Invention

[0010] The problem the invention aims to solve

[0011] Through in-depth research, the inventors have confirmed that R-COF forms a complex with hydrogen halide (HX). Such a complex is represented, for example, by the formula: R-COF-HX (X = F, Cl, Br, I). R-COF and this complex are difficult to separate, and therefore, for example, the following halogen exchange reaction occurs:

[0012] R-COX 1 +HF→R-COF+HX 1

[0013] (In the formula, R represents a monovalent organic group, a hydrogen atom, or a halogen atom, and X represents a monovalent organic group, a hydrogen atom, or a halogen atom.) 1 The reaction product (containing halogen atoms other than fluorine) contains an R-COF-HX complex. Therefore, even if the synthesis yield (crude yield) is high before purification, the initial distillation process to remove impurities leads to a decrease in the R-COF yield (distillation yield). Furthermore, conventional purification methods cannot produce ultra-high purity R-COF with a purity of 5N (99.999% or higher and lower than 99.9999%). Therefore, the object of this invention is to prevent the decrease in R-COF yield caused by impurities and to stably produce high-purity R-COF products.

[0014] Solution for solving the problem

[0015] The inventors conducted in-depth research and discovered that by using metal fluorides as hydrogen halide adsorbents, R-COF-HX complexes can be effectively decomposed, thereby improving the yield and achieving ultra-high purity of R-COF compounds. In other words, this invention provides the following: [1]

[0017] A method for refining carboxyl fluoride includes a step of contacting carboxyl fluoride containing hydrogen halide with a metal fluoride to remove hydrogen halide. [2]

[0019] A method for manufacturing high-purity carboxyl fluoride includes a step of contacting carboxyl fluoride containing hydrogen halide with a metal fluoride. [3]

[0021] A method for removing hydrogen halide from carboxyl fluoride containing hydrogen halide, wherein a metal fluoride is used as a hydrogen halide adsorbent. [4]

[0023] According to any one of [1] to [3], the carboxyl fluoride containing hydrogen halide is the reaction product of the following halogen exchange reaction.

[0024] R-COX1 +HF→R-COF+HX 1

[0025] (In the formula, R represents a monovalent organic group, a hydrogen atom, or a halogen atom, and X represents a monovalent organic group, a hydrogen atom, or a halogen atom.) 1 (Halogen atoms other than fluorine). [5]

[0027] According to any one of [1] to [3], the carboxyl fluoride containing hydrogen halide is a reaction product of the reaction between carboxyl chloride and metal fluoride. [6]

[0029] According to any one of [1] to [3], wherein the carboxyl fluoride containing hydrogen halide is a reaction product in the reaction of carboxyl chloride with chromium fluoride. [7]

[0031] The method according to any one of [1] to [6], wherein the hydrogen halide is selected from at least one of the group consisting of hydrogen fluoride and hydrogen chloride. [8]

[0033] According to any one of [1] to [7], the metal fluoride in the process of removing the hydrogen halide is sodium fluoride. [9]

[0035] According to any one of [1] to [8], wherein the carboxyl fluoride is trifluoroacetyl fluoride.

[10]

[0037] A carboxyl fluoride with a purity of over 99.999%.

[11]

[0039] A trifluoroacetyl fluoride with a purity of over 99.999%.

[0040] The effects of the invention

[0041] According to the present invention, the yield reduction of R-COF caused by impurity contamination can be prevented, and high-purity R-COF products can be stably manufactured. In particular, according to the present invention, ultra-high purity R-COF with a purity of 5N or higher (99.999% or more and less than 99.9999%), which is unattainable using conventional refining methods, can be manufactured. By using the ultra-high purity R-COF obtained by the present invention in semiconductor manufacturing processes, more precise etching can be performed than before, thereby improving the etching performance of the process. Attached Figure Description

[0042] Figure 1 This is a GC-TCD chart of a mixture of CF3COF and HCl.

[0043] Figure 2 The above is a separate GC-MS chart of CF3COF obtained separately, and it is related to... Figure 1 GC-MS chart of peaks adjacent to the HCl peak (below). Detailed Implementation

[0044] [effect]

[0045] The inventors have discovered that, as described below, when obtaining ultra-high purity R-COF products, R-COF forms complexes with hydrogen halides, which makes the removal of hydrogen halides difficult. In the example section below, where only distillation was performed, the removal of the initial fraction increased due to the HCl reversibly released from the CF3COF-HCl complex, resulting in a lower distillation yield. Furthermore, even after distillation purification, the CF3COF-HCl complex could not be removed, making ultra-high purity impossible. Additionally, in order to maximize purity, the low-boiling fraction and initial distillation time were prolonged, reducing productivity. The inventors have discovered that the formation of this complex can be prevented by using metal fluorides. According to the present invention, the conventional methods of using ionic liquids or aromatic heterocyclic compounds to remove acid components from R-COF compounds can be avoided. Furthermore, according to the present invention, hydrogen halides (especially HCl and HF) that are difficult to separate from R-COF by distillation can be removed through a relatively simple operation of purging the metal fluoride, which acts as a hydrogen halide adsorbent. Moreover, the presence of the aforementioned complex was discovered and the complex was successfully removed, thus enabling the first-ever production of ultra-high purity R-COF with a purity of over 5N.

[0046] [Carboxyl fluoride (R-COF)]

[0047] The carboxyl fluoride, the object of the purification method of the present invention, is represented by the formula: R-COF (where R is a monovalent organic group, a hydrogen atom, or a halogen atom). Halogen atoms in R can be listed as fluorine (F), chlorine (Cl), bromine (Br), and iodine (I). Monovalent organic groups can be, for example, alkyl groups having 1 to 6 carbon atoms, particularly alkyl groups having 1 to 4 carbon atoms, especially methyl, ethyl, propyl (especially n-propyl, isopropyl), butyl (especially n-butyl, isobutyl, tert-butyl), etc.; aryl (especially phenyl, tolyl), aralkyl (especially benzyl, phenethyl), etc. The monovalent organic group can be substituted with a halogen atom, an alkoxy group, etc. Examples of substituted organic groups include, for example, perfluoroalkyl groups such as difluoromethyl, trifluoromethyl, pentafluoroethyl, heptafluoropropyl; alkoxyalkyl groups such as methoxymethyl; and alkoxyaryl groups such as methoxyphenyl.

[0048] More specifically, examples of carboxyl fluorides include fluorides of carboxylic acids having 1 to 7 carbon atoms, with fluorides of carboxylic acids having 2 to 7 carbon atoms being preferred. Examples of carboxylic acids having 1 to 7 carbon atoms include formic acid, acetic acid, propionic acid, n-butyric acid, isobutyric acid, n-valeric acid, isovaleric acid, neovaleric acid, n-hexanoic acid, isohexanoic acid, neohexanoic acid, n-heptanoic acid, isoheptanoic acid, neoheptanoic acid, and combinations thereof. The hydrogen atoms on the carboxylic acid may be fluorinated, preferably perfluorocarboxyl fluorides in which all hydrogen atoms are replaced by fluorine atoms. Specific examples of carboxyl fluorides include difluoroacetyl fluoride (CHF₂COF), trifluoroacetyl fluoride, perfluoron-butyryl fluoride, and perfluoron-heptanoic acid fluoride.

[0049] [Metal fluorides]

[0050] Metal fluorides used as hydrogen halide adsorbents are derived from the formula: MF n (In the formula, M represents a metal atom, and n represents the valence of the metal atom). Examples of metal fluorides include alkali metal fluorides, alkaline earth metal fluorides, transition metal fluorides, and combinations of two or more of these. Examples of alkali metal fluorides include lithium fluoride, sodium fluoride, and potassium fluoride. Examples of alkaline earth metal fluorides include magnesium fluoride, calcium fluoride, and barium fluoride. Examples of transition metal fluorides include chromium fluoride, molybdenum fluoride, manganese fluoride, iron fluoride, cobalt fluoride, copper fluoride, nickel fluoride, zinc fluoride, and silver fluoride. As chromium fluorides, any of chromium fluoride (III), chromium fluoride (VI), and mixtures thereof can be used. As molybdenum fluorides, any of molybdenum fluoride (IV), molybdenum fluoride (V), molybdenum fluoride (VI), and mixtures thereof can be used. As fluorides of manganese, any of manganese fluoride (II), manganese fluoride (III), manganese fluoride (IV), and mixtures thereof can be used. As fluorides of iron, any of iron fluoride (II), iron fluoride (III), and mixtures thereof can be used. As fluorides of cobalt, any of cobalt fluoride (II), cobalt fluoride (III), and mixtures thereof can be used. As fluorides of copper, any of copper fluoride (I), copper fluoride (II), and mixtures thereof can be used. For fluorides of nickel and zinc, divalent metal fluorides are stable. As fluorides of silver, 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.

[0051] Besides being used in powder form, metal fluorides can also be used in granular (cylindrical) (e.g., particle size 0.5–30 mm), honeycomb, granular (spindle-shaped) (e.g., particle size 0.5–30 mm), spherical (e.g., particle size 0.5–30 mm), and other block forms other than powders. Advantages of using it in forms other than powders include: the solidification of the metal fluorides creates a flow path for the raw material gas, reducing the likelihood of decreased reaction efficiency. 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 the molded metal fluoride (e.g., granules) typically has fine pores and voids, gas can be circulated even at a filling rate of 100% by volume.

[0052] [Refining Method]

[0053] The purification method of the present invention includes a step of removing hydrogen halide by contacting carboxyl fluoride containing hydrogen halide with a metal fluoride. Specifically, for example, by passing carboxyl fluoride (R-COF) containing hydrogen halide (HX) through a metal fluoride packed column, the complex of R-COF and HX in the carboxyl fluoride decomposes, and the R-COF gas separated from HX is further purified by distillation, thereby obtaining a high-purity product. The temperature of the packed column during purification is preferably 15–35°C, and most preferably at room temperature (particularly 10–30°C). The hydrogen halide adsorbed on the metal fluoride can be removed by drying at high temperature under a nitrogen atmosphere; therefore, by performing this operation, the metal fluoride can be repeatedly regenerated and reused.

[0054] Examples of metal fluoride packed towers include those constructed by filling various shapes of metal fluorides into a cylindrical tube equipped with a temperature regulator for adjusting the purification temperature (used as a heater during drying and metal fluoride regeneration), allowing the feed gas to flow from one end of the tube to the other. Regarding the direction of feed gas flow, when the cylindrical tube filled with metal fluorides extends vertically, the feed gas can flow gradually by gravity; therefore, a gradual, uniform flow from top to bottom is preferable. When the cylindrical tube extends vertically and the feed gas flows from bottom to top, from an adsorption efficiency perspective, it is desirable to have large-particle metal fluorides mixed in the lower part of the cylindrical tube and small-particle powdered metal fluorides in the upper part. Examples of materials for the reaction apparatus include corrosion-resistant metals such as stainless steel, ferrochrome, Monel alloy, Hastelloy, and nickel. Among these, stainless steel and nickel are preferred from a corrosion resistance point of view.

[0055] Examples of substances that are particularly preferred as objects of refining include the following substances.

[0056] Examples include: (1) halogen exchange reactions as shown in the following formula:

[0057] R-COX 1 +HF→R-COF+HX 1

[0058] (In the formula, R represents a monovalent organic group, a hydrogen atom, or a halogen atom, and X represents a monovalent organic group, a hydrogen atom, or a halogen atom.) 1 The reaction products of R-COF and HX (excluding fluorine halogen atoms) are... 1 The mixture. Here, since the reaction products also contain unreacted HF, the objects to be purified are actually R-COF and HX.

[0059] Examples include: (2) the reaction products of carboxyl chlorides and metal fluorides. As a carboxyl chloride, the compound (R-COCl) in which the -COF portion of the above-mentioned carboxyl chloride (R-COF) forms -COCl can be cited; as a metal fluoride, the above-mentioned compound can be cited. If specific examples are listed, the following formula can be cited:

[0060] 3R-COCl + CrF3 → 3R-COF + CrCl3

[0061] The product represents the reaction of carboxyl chloride with chromium fluoride. In this reaction, theoretically, the Cl reacting with chromium should be removed as CrCl3, therefore HCl should not be present in the reaction system, and the aforementioned complex should not form. However, in practice, small amounts of HF and HCl will be present. The reason is that the CrCl3 produced in the reaction is expressed by the following formula:

[0062] CrCl3 + HF → CrF3 + HCl

[0063] HF is used during regeneration to CrF3, and HCl is produced as a byproduct. This regenerated CrF3 is then reused as a reactant in R-COF synthesis. It can be assumed that Cr can be supported on activated carbon. In such cases, when used as a supported catalyst, the fluorinating agent (HF) used in the regeneration reaction, the byproduct HCl, etc., are easily further adsorbed and remain in the activated carbon.

[0064] Examples include: (3) the reaction product in the method of producing CF3COF by photo-oxidation of CF3CHClF. For example, CF3CHCIF is oxidized by irradiating it with a UV lamp. In this case, oxygen is added as a reactant and Cl (catalyst amount) is added as a free radical initiator. The reaction formula is as follows.

[0065] 2CF3CHClF + O2 → 2CF3COF + 2HCl

[0066] Therefore, HCl is present in the crude product after the reaction.

[0067] Examples include: (4) the reaction products in the method of oxidizing and thermally decomposing CF3CF=CF2 to produce CF3COF. For example, O2 is used as the reactant, and AgNO3 and Ag2O are used as catalysts. The thermal decomposition temperature is about 250℃. The reaction formula is as follows.

[0068] CF3CF=CF2+O2→CF3COF+COF2

[0069] This method relies on thermal decomposition, therefore, due to the water mixed in the reaction system, impurities such as hydrogen halides are easily generated in the crude product.

[0070] (5) Regardless of the synthesis method of R-COF, R-COF is very easy to hydrolyze, and therefore easily contains HF (hydrogen halide) due to changes over time. Since the hydrogen halide generated over time forms a complex with R-COF, it is impossible to achieve ultra-high purity of R-COF using conventional methods.

[0071] In this specification, a mixture of CF3COF with HCl and / or HF is illustrated, particularly as a substance that is difficult to separate.

[0072] [Ultra-high purity R-COF and its manufacturing method]

[0073] Using the purification method of the present invention, ultra-high purity carboxyl fluoride with a purity of 99.999% or higher can be produced. Previously, due to the inability to separate the complex of carboxyl fluoride with hydrogen halide, even precision distillation could not yield such ultra-high purity carboxyl fluoride. In the present invention, a step is first performed where the carboxyl fluoride containing this complex is contacted with a metal fluoride (e.g., through a metal fluoride packed column). The purified carboxyl fluoride, obtained after removing the difficult-to-separate complex, is then distilled to remove other impurities, thereby achieving ultra-high purity carboxyl fluoride with a purity of 99.999% or higher. The order of passage through the metal fluoride packed column and the distillation column is not particularly limited; it is permissible to pass through the distillation column first, followed by the metal fluoride packed column.

[0074] [Applications of Ultra-High Purity R-COF]

[0075] The ultra-high purity R-COF produced by this invention is essentially free of impurities, thus enabling precise chemical reactions in semiconductor manufacturing processes, such as etching and deposition at the atomic level.

[0076] Example

[0077] [Confirmation of the CF3COF-HCl complex]

[0078] The inventors have discovered that when CF3COF comes into contact with HCl, a CF3COF-HCl complex is formed. Figure 1 The image shows a GC-TCD graph of a mixture of CF3COF and HCl. Additionally, Figure 2 The image shows a separate GC-MS graph of CF3COF (top) and a graph with... Figure 1 GC-MS graph of the peaks adjacent to the HCl peak (below). Figure 2 It can be seen that, with Figure 1 The peak adjacent to the HCl peak exhibits the spectrum obtained by adding a peak equivalent to the molecular weight 36 of HCl in a separately obtained GC-MS chart of CF3COF (top), thus confirming its relationship with... Figure 1 The peak adjacent to the HCl peak is the complex of CF3COF and HCl.

[0079] [Example 1]

[0080] The stainless steel reaction tube, which has perforated metal at the bottom to prevent NaF granules from falling, is prepared to be filled with NaF granules (size ( Cylindrical shape, bulk density 1.55 g / cm³ 3 The adsorbent-packed tower (hereinafter referred to as "NaF tower") is used. The specifications of the NaF tower are shown in Table 1, and the HF and HCl removal performance of the NaF tower is shown in Table 2.

[0081] [Table 1]

[0082]

[0083] In Table 1 above, the residence time T1 is V / F (total volume of gas that has passed through the tower (L) / flow rate (L / min)).

[0084] [Table 2]

[0085] HCl, HF, and NaF removal results from the tower (unit: ppm)

[0086]

[0087] Based on Tables 1 and 2, it can be confirmed that NaF granules can adsorb HF and HCl.

[0088] The input gas (the object to be purified) is the reaction product (crude gas from the stationary phase reactor) prepared by the following method.

[0089] Manufacturing method of trifluoroacetyl fluoride (CF3COF) using CrF3 / C:

[0090] A SUS brush was installed at the bottom of a 2B vertical SUS reactor, and CrF3 / C with a loading of 17–33% by mass was packed above the brush. The reactor was heated to 200–350 °C. Trifluoroacetyl chloride (CF3COCl(TFAC)) was passed through, and the formation of CF3COF was confirmed by GC analysis of the outlet gas. The generated CF3COF was collected by cooling a 500 mL container with liquid nitrogen. HCl and HF were present in the CF3COF gas, which was a reaction product.

[0091] Using GC and FT-IR, the following three gases containing R-COF-HX complexes were prepared using the above-mentioned CF3COF gas:

[0092] (1) Distillate of a mixture of CF3COF and HCl (molar ratio 1:1) (without purging the NaF column before distillation)

[0093] (2) Distillate of a mixture of CF3COF and HCl (around 1000 ppm) (without purging the NaF column before distillation).

[0094] (3) Distillate of a mixture of CF3COF and HCl (around 1000 ppm) (with the above-mentioned NaF column being purged before distillation).

[0095] Analysis was conducted. The gas flow rate was controlled using a mass flow controller (MFC) as the gas passed through, and experiments were performed.

[0096] (NaF tower passing conditions)

[0097] In a cylindrical stainless steel reactor with perforated metal at the bottom to prevent NaF granules from falling out, NaF granules (size ( )) were filled at a filling rate of 66.5% by volume. Cylindrical shape, bulk density 1.55 g / cm³ 3 The reactor is made to stand vertically upright, and under the following conditions, air is circulated from the top of the reactor downwards, and then supplied to the distillation column of the next process.

[0098] Temperature: 15~35℃

[0099] Pressure: 0~0.2MPaG (gauge pressure)

[0100] Flow rate: 2-4 kg / hour

[0101] (Distillation conditions)

[0102] Pressure at the top of the vessel / tower: 0~0.2MPaG (gauge pressure)

[0103] Kettle / tower top temperature: -40℃~-100℃

[0104] Fraction discharge flow rate: 0.1kg~2kg

[0105] The results are shown in Tables 3-5.

[0106] [Table 3]

[0107] ①A mixture of CF3COF and HCl (molar ratio 1:1) Examples of distillation without NaF column aeration

[0108]

[0109] The definitions of each fraction shown in the table are as follows.

[0110] Preliminary fraction: The fraction containing HCl (containing more low-boiling-point substances) before the main fraction.

[0111] Main fraction: Fraction with a purity of 90% or higher but lower than 99% (1N)

[0112] The latter fraction: the fraction containing HCl (a fraction with a high concentration of high-boiling-point substances) after the main fraction.

[0113] Bottom pan: For fractions that cannot be recovered during normal operation, such as those heated in the column (fractions with high boiling point components).

[0114] In the table, "ND" means "not detected".

[0115] To remove HCl, an additional 175g of initial fraction is required. The CF3COF and CF3COF-HCl complex cannot be separated, and the CF3COF-HCl complex is contaminated in the main fraction. High purity cannot be achieved, stopping at 1N (purity above 90% but below 99%). If the HCl concentration is high during feeding, HCl will also be contaminated in the later fraction. The HCl contained in the later fraction is considered to have been released from the complex.

[0116] [Table 4]

[0117] ②A mixture of CF3COF and HCl (around 1000 ppm) Examples of distillation without NaF column aeration

[0118]

[0119] The definitions of each fraction shown in the table are as follows.

[0120] Preliminary fraction: The fraction with a purity of 99.9% or higher but lower than 99.99% before the main fraction (fraction with a high content of low-boiling-point substances).

[0121] Main fraction: Fractions with a purity of 99.9% or higher but lower than 99.99%.

[0122] After-distillate: The fraction with a purity lower than 99.9% after the main distillate (fraction with more high-boiling-point substances), which is not equivalent to the after-distillate.

[0123] Bottom pan: For fractions that cannot be recovered during normal operation, such as those heated in the column (fractions with high boiling point components).

[0124] In the table, "ND" means "not detected".

[0125] The main fraction, taking into account gases (N2+CO) that are difficult to remove by distillation, has an actual purity of 3N (99.9888%). Removing (N2+CO) and converting the purity to 4N (above 99.99% and below 99.999%), yields a product of 5N (above 99.999% and below 99.9999%). Furthermore, during the recovery of the initial fraction, 29.9 kg of the initial fraction is required due to the HCl believed to be released from the CF3COF-HCl complex. Achieving a purity of 5N or higher through distillation is impossible, and the time required for low-boiling fractions and initial distillation is prolonged, reducing productivity (main fraction).

[0126] [Table 5]

[0127] ③A mixture of CF3COF and HCl (around 1000 ppm) A NaF column is used for gas purging before distillation.

[0128]

[0129] The gas is introduced into the distillation column in three stages (feed 1 to 3) before distillation begins.

[0130] The definitions of each fraction shown in the table are as follows.

[0131] Preliminary fraction: The fraction with a purity of 3N (purity above 99.9% but below 99.99%) before the main fraction (fraction with a high content of low-boiling-point substances).

[0132] Main fraction: Fraction with a purity of 5N (purity above 99.999% but below 99.9999%).

[0133] Afterburner: Since a large portion of the main fraction can be recovered, no fraction equivalent to the afterburner is obtained.

[0134] Bottom pan: The fraction (containing high-boiling-point substances) that cannot be recovered during normal operation by heating the column.

[0135] In the table, "ND" means "not detected".

[0136] By purging the NaF column before distillation, the CF3COF-HCl complex is decomposed, and high-purity CF3COF with no detectable HCl is distilled out, thus achieving ultra-high purity through distillation.

[0137] Table 3 shows that if the gas is mixed with CF3COF-HCl complex, not only is the initial fraction high and the yield low, but it is also difficult to achieve high purity of CF3COF through distillation. Table 4 shows that even with trace amounts of HCl, a considerable amount of initial fraction is still required due to the formation and release of HCl from the CF3COF-HCl complex, making ultra-high purity of CF3COF difficult. Based on Table 5, by contacting the gas mixed with CF3COF-HCl complex with NaF, the complex, which is difficult to separate by distillation, is decomposed, resulting in a low initial fraction, high yield, and thus achieving ultra-high purity of CF3COF. In the example of this invention, the main fraction achieved a CF3COF purity exceeding 99.999%.

Claims

1. A method for purifying carboxyl fluoride, comprising: The process involves contacting carboxyl fluoride containing hydrogen halide with a metal fluoride to remove the hydrogen halide and obtain carboxyl fluoride with a purity of 99.999% or higher. This process includes passing the carboxyl fluoride containing hydrogen halide through a metal fluoride packed column, and further refining the carboxyl fluoride after passing through the metal fluoride packed column by distillation in a distillation column. The metal fluoride is sodium fluoride. The carboxyl fluoride is selected from at least one of the following groups: difluoroacetyl fluoride (CHF2COF), trifluoroacetyl fluoride, perfluorobutyryl fluoride, and perfluoroheptyl fluoride.

2. A method for manufacturing carboxyl fluoride with a purity of 99.999% or higher, comprising: The process of removing hydrogen halide by contacting carboxyl fluoride containing hydrogen halide with a metal fluoride includes passing the carboxyl fluoride containing hydrogen halide through a metal fluoride packed column, and further refining the carboxyl fluoride that has passed through the metal fluoride packed column by distillation in a distillation column. The metal fluoride is sodium fluoride. The carboxyl fluoride is selected from at least one of the following groups: difluoroacetyl fluoride (CHF2COF), trifluoroacetyl fluoride, perfluorobutyryl fluoride, and perfluoroheptyl fluoride.

3. A method for removing hydrogen halide from carboxyl fluoride containing hydrogen halide to obtain carboxyl fluoride with a purity of 99.999% or higher, using a metal fluoride as a hydrogen halide adsorbent, wherein the method for removing hydrogen halide to obtain carboxyl fluoride with a purity of 99.999% or higher includes passing the carboxyl fluoride containing hydrogen halide through a metal fluoride packed column, and further refining the carboxyl fluoride that has passed through the metal fluoride packed column by distillation in a distillation column. The metal fluoride is sodium fluoride. The carboxyl fluoride is selected from at least one of the following groups: difluoroacetyl fluoride (CHF2COF), trifluoroacetyl fluoride, perfluorobutyryl fluoride, and perfluoroheptyl fluoride.

4. The method according to any one of claims 1 to 3, wherein, Carboxyl fluorides containing hydrogen halides are reaction products of the following halogen exchange reaction. R-COX 1 +HF→R-COF+HX 1 In the formula, R represents a monovalent organic group, a hydrogen atom, or a halogen atom, and X represents... 1 It consists of halogen atoms other than fluorine.

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

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

7. The method according to any one of claims 1 to 3, wherein, Hydrogen halides are selected from at least one of the groups consisting of hydrogen fluoride and hydrogen chloride.

8. The method according to any one of claims 1 to 3, wherein, The carboxyl fluoride is trifluoroacetyl fluoride.

9. The method according to any one of claims 1 to 3, wherein, The temperature of the filling tower is 15–35°C.

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