KR100502996B1 - Production and use of octafluoropropane - Google Patents

Abstract

(1) reacting hexafluoropropene and hydrogen fluoride in a gas phase in the presence of a fluorination catalyst at a temperature of 150 to 450 ° C. to obtain 2H-heptafluoropropane; and (2) 2H obtained in step (1). Octafluoropropane is prepared by a method comprising reacting heptafluoropropane with fluorine gas in a gaseous phase at a temperature of 250 to 500 ° C. to obtain octafluoropropane. The high-purity octafluoropropane used in the manufacturing process of the semiconductor device is obtained.

Description

Production method of octafluoropropane {PRODUCTION AND USE OF OCTAFLUOROPROPANE}

Corresponding-reference of the relevant application

This application claims the benefit of the date of filing of Provisional Application No. 60 / 241,838, filed October 20, 2000, pursuant to Article 111 (b) of the United States Patent Act, pursuant to Article 119 (e) (1) of the United States Patent Act. It is an application under Article 111 (a) of the Patent Act.

The present invention relates to a process for producing octafluoropropane, octafluoropropane products and uses thereof.

Octafluoropropane is used, for example, as a dry-etching gas or a cleaning gas in semiconductor device manufacturing processes. As the preparation method, the following methods are known:

(1) Method for directly fluorinating hexafluoropropene with fluorine gas (JP-A 62-61572 (JP-B-62-61572))

(2) A method for electrolytic fluorination of hexafluoropropene in hydrogen fluoride (JP-A 62-61115 (JP-B-62-61115))

(3) Method of reacting hexafluoropropene and fluorine in the presence of a catalyst (JP-A 1-45455 (JP-B-1-45455))

(4) A method of reacting hexafluoropropene with a high-order metal fluoride (JP-A 62-54777 (JP-B-62-54777)).

However, in this method, by-products such as tetrafluoromethane (CF ₄ ) and hexafluoroethane (C ₂ F ₆ ) are produced by cleavage, and C ₆ F ₁₂ and C ₆ F ₁₄ are produced by radical addition. In addition, for example, the addition of cyclization results in the formation of a four-membered ring, resulting in a decrease in the yield and selectivity of the desired octafluoropropane. In addition, some of these impurities are difficult to separate by distillation, that is, it is difficult to obtain high-purity octafluoropropane. Specifically, when hexafluoropropene is used as the starting material, chloropentafluoroethane (CFC-115) contained as an impurity hardly reacts with fluorine gas and remains in most of the desired octafluoropropane, Since the boiling point is near, this impurity compound can hardly be separated by distillation, making it difficult to produce high-purity octafluoropropane.

The present invention has been made under such a background, and the present invention aims to provide a method for producing a high purity octafluoropropane, a high purity octafluoropropane and its use for use in the manufacturing process of a semiconductor device.

As a result of extensive research to achieve the above object, the present inventors have (1) reacted hexafluoropropene with hydrogen fluoride in the gas phase at 150 to 450 ° C. in the presence of a fluorination catalyst to give 2H-heptafluoropropane. Obtaining (2) and reacting 2H-heptafluoropropane obtained in step (1) with fluorine gas in a gaseous phase at a temperature of 250 to 500 ° C. without a catalyst to obtain octafluoropropane. It has been found that by using, it is possible to produce high-purity octafluoropropane. The present invention has been completed based on this finding.

More specifically, the present invention (I) comprises the steps of (1) reacting hexafluoropropene with hydrogen fluoride in the gas phase at 150 to 450 ° C. in the presence of a fluorination catalyst to obtain 2H-heptafluoropropane and (2 1) A method for producing octafluoropropane, comprising the step of reacting 2H-heptafluoropropane obtained in step (1) with fluorine gas in a gaseous phase at a temperature of 250 to 500 ° C. to obtain an octafluoropropane. to be. In a preferred embodiment of the invention (I), the starting material hexafluoropropene is dichlorodifluoromethane, chlorodifluoromethane, chloropentafluoroethane, chlorotetrafluoroethane and chlorotrifluoroethylene At least one compound selected from the group consisting of: In step (1), the fluoride catalyst is a bulk catalyst obtained by adding at least one selected from the group consisting of chromium oxide as a main component and indium, zinc and nickel, and the molar ratio of hydrogen fluoride / hexafluoropropene is 0.8. To 3: 1.

In a preferred embodiment of the invention (I), a process for removing impurities contained in 2H-heptafluoropropane is provided before step (2); The impurity is at least one compound selected from the group consisting of tetrafluoromethane, trifluoromethane, chlorotrifluoromethane, hexafluoroethane and pentafluoroethane; The process of removing impurities is a distillation process; 2H-heptafluoropropane has a chlorine compound content of 0.01 vol% or less.

In a preferred embodiment of the invention (I), step (2) is carried out in the presence of a diluent gas, the diluent gas being selected from the group consisting of hydrogen fluoride, tetrafluoromethane, hexafluoroethane and octafluoropropane At least one gas; The molar ratio of hydrogen fluoride / 2H-heptafluoropropane in step (2) ranges from 0.9 to 1.5: 1, and the reactor inlet concentration of 2H-heptafluoropropane is 8 mol% or less.

In a preferred embodiment of the invention (I), at least a portion of the outlet gas of step (2) is circulated and reused as the diluent gas of step (2); Reacting at least a portion of the outlet gas of step (2) with one or more hydrofluorocarbons to remove unreacted fluorine gas in the outlet gas; Hydrofluorocarbons are selected from the group consisting of trifluoromethane, tetrafluoroethane, pentafluoroethane and 2H-heptafluoropropane; Separating the hydrogen fluoride contained in the outlet gas of step (2) and returning the separated hydrogen fluoride to step (1) and / or step (2); At least a portion of the octafluoropropane is separated from the gas from which the hydrogen fluoride is separated, and the remaining gas is returned to step (1) and / or step (2).

The present invention (II) relates to octafluoropropane products containing octafluoropropane having a purity of 99.995 vol% or more. In a preferred embodiment, the total amount of compounds having chlorine atoms in the molecule and ring compounds is up to 50 vol ppm based on octafluoropropane products.

The present invention (III) relates to an etching gas comprising the above-described octafluoropropane article. The present invention (IV) relates to a cleaning gas comprising the above-described octafluoropropane product.

Best way to carry out the invention

Hereinafter, the present invention will be described in detail.

Hexafluoropropene (CF ₃ CF = CF ₂ ) used in the present invention (I) is, for example, tetrafluoroethylene (CF ₂ = CF ₂ ) by pyrolysis of chlorodifluoromethane (CHClF ₂ ). It is obtained as a by-product during the process of producing or by a method of chlorinating and optionally dehalogenating propane, propylene or partially halogenated C3 acyclic hydrocarbons, as described in Japanese Patent Application Laid-Open No. 4-145033. However, in the hexafluoropropene obtained by these methods, chlorine in a molecule such as dichlorodifluoromethane, chlorodifluoromethane, chloropentafluoroethane, chlorotetrafluoroethane and chlorotrifluoroethylene as impurities. The compound containing an atom is mixed in many cases. The present invention provides a method for producing octafluoropropane, using hexafluoropropene, which may contain such impurities, as a raw material. Here, the boiling points of the intermediate 2H-heptafluoropropane, the desired octafluoropropane and the aforementioned impurities are shown in Table 1 below.

Compound name Chemical formula boiling point Chlorodifluoromethane CHClF ₂ -41 ℃ Chloropentafluoroethane CF ₃ CClF ₂ -39.3 ℃ Octafluoropropane CF ₃ CF ₂ CF ₃ -36.7 ℃ Dichlorodifluoromethane CCl ₂ F ₂ -29.2 ℃ Hexafluoropropene CF ₃ CF = CF ₂ -29 ℃ Chlorotrifluoroethylene CF ₂ = CClF -27.9 ℃ 2H-heptafluoropropane CF ₃ CHFCF ₃ -15.2 ℃ Chlorotetrafluoroethane CF ₃ CHClF -12 ℃

As is apparent from the boiling point shown in Table 1, the boiling point of the compound having a chlorine atom in the molecule contained in the starting material hexafluoropropene is close to the boiling point of the obtained octafluoropropane, and thus only by distillation operation Difficult to separate compounds

In the method for producing octafluoropropane of the present invention (I), first, hexafluoropropene and hydrogen fluoride are reacted in a gaseous phase at a temperature of 150 to 450 ° C. in the presence of a fluorination catalyst to obtain 2H-heptafluoropropane. Perform step (1). Step (1) has two advantages.

[1] When hexafluoropropene is directly fluorinated with fluorine gas or when fluorine is directly fluorinated with fluorine gas in the presence of a catalyst or a higher order metal fluoride, carbon-carbon bond cleavage reaction, radical addition reaction, and cyclization Reactions and the like produce various byproducts. Therefore, yield and selectivity are not only low, but high purity octafluoropropane is hardly obtained. The present invention can suppress the production of by-products from these reactions by adding hydrogen fluoride to hexafluoropropene in the presence of a catalyst to obtain intermediate 2H-heptafluoropropane in high yield and high selectivity.

[2] As described above, hexafluoropropene often contains a compound having a chlorine atom in its molecule as an impurity, and these compounds are difficult to remove by distillation. In the present invention, hydrogen fluoride is added to hexafluoropropene to obtain intermediate 2H-heptafluoropropane, and at the same time, a compound having a chlorine atom in the molecule is fluorinated using hydrogen fluoride and thus separated by distillation. Convert to easy compounds.

The reaction of adding hydrogen fluoride to hexafluoropropene is carried out according to the following formula (1) in the presence of a fluorination catalyst:

CF ₃ CF = CF ₂ + HF → CF ₃ CHFCF ₃ (1)

As the fluorination catalyst, a chromium-based catalyst usually used may be used. When hexafluoropropene contains a chlorine-containing impurity and the chlorine-containing impurity is fluorinated and converted into another compound, the reaction temperature is gradually increased, so that chromium as a catalyst having excellent activity (performance) and stability (catalyst lifetime) It is preferable to use a bulk catalyst obtained by adding at least one selected from indium, zinc and nickel as an oxide as a main component. Supported catalysts (eg, alumina carriers) may also be used, but bulk catalysts are preferred in terms of activity and stability. These catalysts are activated by fluorination treatment with hydrogen fluoride before being used for the reaction.

In step (1), the reaction temperature depends on the type and content of impurities in hexafluoropropene but is in the range from 150 to 450 ° C., preferably in the range from 200 to 350 ° C. When CFC-115 is contained as an impurity in hexafluoropropene, the reaction temperature is suitably in the range of 350 to 450 ° C, preferably 350 to 400 ° C. When the reaction temperature exceeds 450 ° C, the stability of the catalyst tends to be lowered. However, when the reaction temperature is lower than 150 ° C, the conversion to the desired reaction decreases or the fluorination reaction of the impurity compound is slowed. not.

The molar ratio (HF / FC01216) of hydrogen fluoride and hexafluoropropene (FC-1216) is preferably 0.8 to 3.0: 1, more preferably 1.0 to 2.0: 1. When the molar ratio of hydrogen fluoride and hexafluoropropene is 0.8: 1 or less, the conversion of hexafluoropropylene is lowered, while the molar ratio of 3.0: 1 or higher increases the cost for the recovery device of unreacted HF. Not.

As described above, the starting material hexafluoropropene may contain a compound having a chlorine atom in its molecule as an impurity, and these impurities are generally difficult to separate by distillation. Examples of compounds having a chlorine atom in the molecule include chlorodifluoromethane, chloropentafluoroethane, dichlorodifluoromethane, chlorotrifluoroethylene and chlorotetrafluoroethane. The present invention (I) is easy to separate these compounds containing chlorine by distillation in the step of reacting hexafluoropropene, which is the main reaction in the presence of a fluorination catalyst, with hydrogen fluoride to obtain 2H-heptafluoropropane. Conversion to one other fluoro-compound.

Chlorine compounds can be converted to other fluorine compounds, for example, by the following reactions (2) to (5):

CHClF ₂ + HF → CHF ₃ + HCl (2)

CF ₂ = CClF + HF → CF ₃ CHClF (3)

CF ₃ CHClF + HF → CF ₃ CHF ₂ + HCl (4)

CF ₃ CClF ₂ + HF → CF ₃ CF ₃ + HCl (5)

The boiling point of these fluorinated compounds and the intermediate, 2H-heptafluoropropane, is shown in Table 2.

Compound name Chemical formula boiling point Tetrafluoromethane CF ₄ -128 ℃ Trifluoromethane CHF ₃ -84.4 ℃ Chlorotrifluoromethane CClF ₃ -81.4 ℃ Hexafluoroethane CF ₃ CF ₃ -78.1 ℃ Pentafluoroethane CF ₃ CHF ₂ -48.5 ℃ 2H-heptafluoropropane CF ₃ CHFCF ₃ -15.2 ℃

As is apparent from Table 2, the boiling point of the fluorinated compound according to the above-described reaction with the intermediate 2H-heptafluoropropane shows a remarkably large difference, and as a result, these compounds can be easily separated by distillation.

A gas mainly composed of 2H-heptafluoropropane obtained in step (1) is introduced into a dehydrohalogenation reaction step in which hydrogen chloride and unreacted hydrogen fluoride are separated therefrom. Hydrogen chloride and hydrogen fluoride are further separated from each other by distillation, and the hydrogen chloride is neutralized using an aqueous alkali solution. Hydrogen fluoride can be returned to the step of fluorinating hexafluoropropene and neutralized with aqueous alkali solution. After separating hydrogen chloride and hydrogen fluoride in the dehydrohalogenation reaction step, a gas mainly composed of 2H-heptafluoropropane is treated in step (2), but before the gas is introduced into the distillation column to be contained in 2H-heptafluoropropane. It is desirable to remove the impurities.

 Specific examples of impurities contained in 2H-heptafluoropropane include tetrafluoromethane, trifluoromethane, chlorotrifluoromethane, hexafluoroethane and pentafluoroethane. It is preferable to remove these impurities by distillation. In the distillation column, the lower boiling fractions tetrafluoromethane, trifluoromethane, chlorotrifluoromethane, hexafluoroethane and pesamfluoroethane are extracted at the top of the distillation column and 2H-heptafluoropropane is extracted from the bottom. do. This gas, mainly composed of 2H-heptafluoropropane, is used as a starting material in direct fluorination with fluorine gas. Regardless of the distillation after the dehydrohalogenation reaction step, the content of the chlorine compound contained as impurities in the 2H-heptafluoropropane is preferably 0.01 vol% or less, more preferably 0.005 vol% or less.

Step (2) will be described below.

Step (2) is a direct fluorination step for obtaining octafluoropropane by reacting 2H-heptafluoropropane obtained in the fluorination step of step (1) with fluorine gas at a temperature of 250 to 500 ° C. in a gaseous phase without catalyst. . This step has three advantages:

[1] In case of producing perfluorocarbon by reacting hydrofluorocarbon and fluorine gas, enormous reaction heat is generated. The heat of reaction is proportional to the number of moles of fluorine reacted per molecule. The greater the amount of fluorine, the greater the heat of reaction, the greater the likelihood of cleavage, polymerization, cyclization or addition of carbon-carbon bonds, or in some cases explosions, and lower yields, resulting in industrial manufacturing or operational problems. do. In order to suppress the rapid generation of heat of reaction in a direct fluorination reaction, a method of diluting fluorine with an inert gas (for example, nitrogen or helium), a method of diluting an organic substance as a substrate, and the like are known. Inert gases such as nitrogen and helium are undesirable in terms of cost in view of their separation and purification from the perfluorocarbons of interest during the distillation step. In the present invention (I), the above-mentioned problem is solved by using at least one gas selected from the group consisting of hydrogen fluoride, tetrafluoromethane, hexafluoroethane and octafluoropropane as the diluent gas.

[2] In the present invention (I), the reaction is carried out by lowering the reactor inlet concentration of the reaction substrate 2H-heptafluoropropane to below the explosion range, specifically 8 mol% or less, using diluent gas. As described above, the fluorine gas used in the direct fluorination reaction using the fluorine gas has a very high reactivity, so that when the organic compound (specifically, a hydrogen-containing compound) is exposed to the fluorine gas, combustion or explosion may occur. And it is dangerous. In step (2), it is important to prevent the explosion of 2H-heptafluoropropane and fluorine gas since the 2H-heptafluoropropane used as the substrate contains a hydrogen atom. In order to prevent explosion, the composition of the mixed gas needs to be out of the explosion range. As a result of examining the explosion ranges of 2H-heptafluoropropane and fluorine gas, the inventors found that the lower limit of the explosion range of 2H-heptafluoropropane was 8 mol% or less. Thus, a safe range of 2H-heptafluoropropane concentrations can be established at the reaction inlet.

[3] In a direct fluorination reaction in which 2H-heptafluoropropane is reacted with fluorine gas, the use of excess 2H-heptafluoropropane for fluorine gas eliminates the need for removing fluorine gas, but subsequent separation. And significant difficulties arise in purification. In step (2) of the present invention (I), an excess molar number of fluorine gas may be used for 2H-heptafluoropropane in order to increase the reaction efficiency, and when the excess fluorine gas is used, the reaction product gas flowing out of the reaction process is purple. In addition to fluorocarbons and hydrogen fluoride, it contains excess fluorine gas. In order to treat excess fluorine gas, a method of reacting a gas with an inorganic oxide such as alumina or soda lime is known, but this method is not preferable because the reaction generates water and causes corrosion of the device material. In the present invention (I), excess fluorine gas can be removed by contacting the gas with 1.1 times mole of hydrofluorocarbon in a chemical equivalent ratio to the excess fluorine gas.

The direct fluorination reaction of reacting heptafluoropropane with fluorine gas proceeds according to the following reaction (6):

CF ₃ CHFCF ₃ + F ₂ → CF ₃ CF ₂ CF ₃ + HF (6)

This reaction can be carried out under a catalyst but can also be carried out without catalyst. Furthermore, as described above, the direct fluorination reaction for reacting hydrofluorocarbons with fluorine gas has a large heat of reaction, and therefore, it is preferable to carry out the reaction in the presence of diluent gas. The diluent gas used for this reaction is at least one gas selected from the group consisting of hydrogen fluoride, tetrafluoromethane, hexafluoroethane and octafluoropropane. At this time, hydrogen fluoride and / or octafluoropropane are preferably used, and more preferably, a gas rich in hydrogen fluoride is used.

The method of introducing the dilution gas is to dilute one or both of 2H-heptafluoropropane and fluorine gas with diluent gas and then introduce them into the reactor. The concentration of 2H-heptafluoropropane as substrate at the reactor inlet is preferably 8 mol% or less, more preferably 6 mol% or less, which is below the explosion range. The concentration of fluorine gas at the inlet of the reactor is preferably such that the molar ratio of fluorine gas / 2H-heptafluoropropane is in the range of 0.9 to 1.5: 1, more preferably in the range of 0.9 to 1.2: 1. If the fluorine concentration is adjusted so that the molar ratio of fluorine gas / 2H-heptafluoropropane is 0.9: 1 or less, the conversion of 2H-heptafluoropropane may be reduced, while the molar ratio exceeds 1.5: 1. In the case of controlling the reaction, a process for removing unreacted fluorine is added. Furthermore, when the molar ratio of fluorine gas / 2H-heptafluoropropane exceeds 1.5: 1, when the outlet gas of step (2) is circulated and recycled to the diluting gas of step (2), the circulating gas (diluent gas) The concentration of fluorine in the building can increase and problems such as explosion can occur.

By dilution gas, 2H-heptafluoropropane and fluorine gas diluted to concentrations below the explosive range can be reacted in the gas phase. 250-500 degreeC of reaction temperature is suitable, Preferably it is 350-450 degreeC. If the reaction temperature is 250 ° C. or lower, the reaction proceeds slowly, while if it exceeds 500 ° C., the carbon-carbon bond in the desired octafluoropropane may be broken, which is undesirable.

The outlet gas of step (2) consists mainly of hydrogen fluoride and octafluoropropane. In the present invention (I), at least part of the outlet gas can be circulated and recycled to the diluent gas in step (2). When unreacted fluorine gas is contained in the outlet gas, a small amount of outlet gas is continuously introduced into the solution containing the continuously flowing metal iodide to generate iodine, and the transmittance of visible light in a specific wavelength region passing through the solution The concentration of unreacted fluorine gas can be detected using a method of continuously quantifying the iodine generated by the measurement. As a method of detecting the fluorine compound and determining the reaction rate, a method of measuring the concentration of perfluorocarbon, hydrofluorocarbon and hydrogen fluoride contained in the mixed gas by infrared spectroscopy can be used. In this way, the operation can be carried out continuously under industrially safe conditions.

In addition to recycling the outlet gas of step (2) as a diluent gas by circulation, if an unreacted fluorine gas is contained therein, for example, an almost same amount of reaction outlet gas as the supplied 2H-heptafluoropropane is extracted. After the introduction into the step of removing unreacted fluorine, it is preferable to remove the fluorine gas by contacting the excess fluorine gas with 1.1 times mole of hydrofluorocarbon in a chemical equivalent ratio. Although the contact temperature of the process of removing a fluorine gas changes with hydrofluorocarbons, Preferably it is 250-500 degreeC, More preferably, it is 350-450 degreeC. The concentration of fluorine gas in the outlet gas after the fluorine removal process is typically 50 ppm or less, and may be 10 ppm or less, depending on the conditions. Specific examples of hydrofluorocarbons capable of reacting with excess fluorine gas include trifluoromethane, tetrafluoroethane, pentafluoroethane and 2H-heptafluoropropane.

The outlet gas of step (2) is introduced into the partial condensation process after the fluorine removal process if fluorine gas remains in it, except for the part of the outlet gas that is circulated and recycled to the diluent gas of step (2) . The main components of the outlet gas are hydrogen fluoride and octafluoropropane, which cool the reaction system in a partial condensation process to allow the hydrogen fluoride to be liquid separated, and the octafluoropropane is mainly separated as a gas. The separated hydrogen fluoride can be circulated and recovered and recycled to the fluorination step (1) and / or the direct fluorination step (2). The gas based on octafluoropropane, which is separated by gas, is subjected to a dehydration process, boosted by a compressor, and introduced into a distillation column.

After introducing a gas containing octafluoropropane as a main component into the distillation column, for example, a low boiling fraction is extracted from the top of the primary distillation column. The low boiling fraction is an inert gas, tetrafluoromethane, hexafluoroethane and the like, which can be used directly as diluent gas in the fluorination step (2). The gas mainly composed of octafluoropropane extracted from the bottom is introduced into the secondary distillation column, and in the secondary distillation column, the octafluoropropane is extracted from the upper portion into the lower boiling point fraction and then introduced into the product process. The high boiling fraction extracted from the bottom of the secondary distillation column can be recovered in step (2) and used as a diluent gas or, if desired, to be decomposed using a harmful gas remover or the like.

The desired octafluoropropane introduced into the product process is further purified, if necessary, and optionally introduced into the product tank via a dehydration process. Octafluoropropane introduced into the product tank can be prepared using analytical methods such as (1) gas chromatography using TCD, FID, or ECD, or (2) gas chromatography-mass spectrometry (GC-MS). Purity can be determined. The present invention (II) relates to high purity octafluoropropane having a purity of 99.995 vol% or more obtained using the process of the present invention (I). For impurities contained in octafluoropropane, the total amount of compounds containing chlorine atoms in the molecule and the cyclic compound is 50 vol ppm or less, and the total amount of such impurities can also be reduced to 10 vol ppm or less.

This invention (III) and this invention (IV) are description about the use of the high purity octafluoropropane obtained using the manufacturing method of this invention (I).

The high purity octafluoropropane of the present invention (II) can be used as an etching gas in an etching step in the method of manufacturing a semiconductor device, and can also be used as a cleaning gas in a cleaning step in a manufacturing method of a semiconductor device. In the method of manufacturing a semiconductor device such as an LSI or a TFT, a thin film or a thick film is formed using a CVD method, a sputtering method or a vapor deposition method, and is etched in the film to form a circuit pattern. A device for forming a thin film or a thick film, and cleaning is performed to remove unnecessary deposits deposited on the inner wall, jig, pipeline, and the like. This is because unnecessary deposits cause particle generation and often have to be removed to produce a good quality film. In use as an etching or cleaning gas, the octafluoropropanes of the present invention may be diluted with an inert gas such as He, Ar, and N ₂ , or F ₂ , NF ₃ , C ₂ F ₄ , HCl, O ₂ and H ₂ Gas such as can be mixed and used in an appropriate ratio. Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention should not be construed as being limited to these Examples.

Raw material example 1

Thermally decomposes HCF-22 (CHClF ₂ ) on alumina with water vapor to produce TFE (tetrafluoroethylene) .After separating and distilling HFP (hexafluoropropene) obtained as a by-product, A raw material hexafluoropropene having the composition shown in 3 was obtained.

compound Chemical formula Composition (volume%) Hexafluoropropene CF ₃ CF = CF ₂ 99.9685 Tetrafluoroethylene CF ₂ = CF ₂ 0.0033 Chlorotrifluoroethylene CF ₂ = CClF 0.0008 Dichlorotetrafluoroethane CF ₃ CCl ₂ F 0.0011 Chloropentafluoroethane CF ₃ CClF ₂ 0.0192 Pentafluoroethane CF ₃ CHF ₂ 0.0028 Chlorotrifluoroethane CF ₃ CH ₂ Cl 0.0004 Chlorodifluoromethane CHClF ₂ 0.0039

Raw material example 2

Commercially available hexafluoropropenes were analyzed and found to have the compositions shown in Table 4.

compound Chemical formula Composition (volume%) Hexafluoropropene CF ₃ CF = CF ₂ 99.9196 Tetrafluoroethylene CF ₂ = CF ₂ 0.0008 Chlorotrifluoroethylene CF ₂ = CClF 0.0004 Chloropentafluoroethane CF ₃ CClF _E 0.0414 Dichlorodifluoromethane CCl ₂ F ₂ 0.0248 Chlorodifluoromethane CHClF ₂ 0.0069 Chlorodifluoroethylene CF ₂ = CHCl 0.0042 Tetrafluoroethane CF ₃ CH ₂ F 0.0019

Preparation of Fluorinated Catalyst

In a 10 L container containing 0.6 L of purified water, 452 g Cr (NO ₃ ) ₃ · 9H ₂ O and 42 g In (NO ₃ ) ₃ · nH ₂ O (n is approximately 5) are dissolved in 1.2 L of purified water. To obtain a solution, 0.31 L of 28% ammonia water was added dropwise for 1 hour or more while adjusting and controlling the respective flow rates of the two aqueous solutions to achieve a reaction solution of pH 7.5 to 8.5 of the reaction solution. The resulting hydroxide slurry was filtered, washed thoroughly with purified water and then dried at 120 ° C. for 12 hours. The solid thus obtained was milled, mixed with graphite and pelletized with a refiner. Under nitrogen flow, the pellet so obtained was calcined at 400 ° C. for 4 hours to obtain a catalyst precursor. The catalyst sphere was charged to an Inconel-made reactor, and then subjected to a fluorination treatment (activation of the catalyst) at 350 ° C. under atmospheric pressure, under a HF stream diluted with nitrogen, and then under a 100% HF flow. Prepared.

Example 1

An Inconel 600 reactor with an internal diameter of 1 inch and a length of 1 m was charged with 100 ml of the catalyst prepared according to the method described for preparing the fluorinated catalyst, and the temperature was raised to 400 ° C while flowing nitrogen. Thereafter, nitrogen fluoride was supplied at 6.32 NL / hr, and a gas containing hexafluoropropene as the main component was supplied at 3.24 NL / hr as described in Raw Material Example 1. The reaction was started by stopping the supply of nitrogen gas. After two hours, the exhaust gas was washed with an aqueous potassium hydroxide solution to remove the acid component, and the gas composition was analyzed by gas chromatography. As a result, a gas having the composition shown in Table 5 was obtained.

compound Chemical formula Composition (vol%) 2H-heptafluoropropane CF ₃ CHFCF ₃ 99.9611 Trifluoromethane CHF ₃ 0.0053 Hexafuluroethane CF ₃ CF ₃ 0.0192 Pentafluoroethane CF ₃ CHF ₂ 0.0071 Octafluoropropane CF ₃ CF ₂ CF ₃ 0.0004 Hexafluoropropene CF ₃ CF = CF ₂ 0.0052 Chloropentafluoroethane CF ₃ CClF ₂ 0.0008 Tetrafluoroethane CF ₃ CH ₂ F 0.0008 Chlorotrifluoroethane CF ₃ CH ₂ Cl 0.0001

After the acid component was removed, the gas was collected by cooling using a cylinder container and distilled purified to remove the low and high boiling fractions by known methods. The composition obtained after distillation purification was analyzed by gas chromatography and found to have the composition of Table 6.

compound Chemical formula Composition (vol%) 2H-heptafluoropropane CF ₃ CHFCF ₃ 99.9965 Pentafluoroethane CF ₃ CHF ₂ 0.0003 Octafluoropropane CF ₃ CF ₂ CF ₃ 0.0001 Hexafluoropropene CF ₃ CF = CF ₂ 0.0019 Chloropentafluoroethane CF ₃ CClF ₂ 0.0007 Tetrafluoroethane CF ₃ CH ₂ F 0.0005

From the results shown in Table 6, it was found that the chlorine compound contained as an impurity in 2H-heptafluoropropane can be distilled down to less than 0.01 vol%.

Example 2

The fluorination reaction was carried out directly with fluorine gas using a gas mainly composed of 2H-heptafluoropropane after distillation obtained in Example 1. A nickel reactor with an internal diameter of 20.6 mmΦ and a length of 500 mm (heated by an electric heater; the reactor undergoes passivation at a temperature of 500 ° C. with fluorine gas) was supplied at 20 NL / hr and flowed at 400 ° C. Heated.

Hydrogen fluoride (diluent gas) was then fed into the bifurcation at 60 NL / hr, and at one gas flow rate, the gas mainly containing the 2H-heptafluoropropane was supplied at 3.24 NL / hr. Thereafter, fluorine gas was supplied at 3.55 NL / hr at another hydrogen fluoride gas flow rate, the nitrogen gas supply was stopped, and a direct fluorination reaction was performed. After 3 hours, the reaction product gas was washed with aqueous potassium hydroxide solution and aqueous potassium iodide solution, hydrogen fluoride and unreacted fluorine gas were analyzed, the acid component was removed, and analyzed by gas chromatography. As a result, the organic substance was found to have a gas composition shown in Table 7.

compound Chemical formula Composition (vol%) Octafluoropropane CF ₃ CF ₂ CF ₃ 99.1042 Tetrafluoromethane CF ₄ 0.0011 Hexafluoroethane CF ₃ CF ₃ 0.0017 2H-heptafluoropropane CF ₃ CHFCF ₃ 0.8762 Chloropentafluoroethane CF ₃ CClF ₂ 0.0006 Perfluorohexane C ₆ F ₁₄ 0.0162

The amount of unreacted fluorine gas in the reaction outlet gas is 0.26 NL / hr.

After the acid component was removed, the gas was collected by cooling using a cylinder container and distilled purified to remove the low and high boiling fractions by known methods. The composition obtained after distillation purification was analyzed by gas chromatography and found to have the composition of Table 8.

compound Chemical formula Composition (vol%) Octafluoropropane CF ₃ CF ₂ CF ₃ 99.9992 2H-heptafluoropropane CF ₃ CHFCF ₃ 0.0002 Chloropentafluoroethane CF ₃ CClF ₂ 0.0006

From the results shown in Table 8, it was found that the resulting octafluoropropane had a purity of 99.999 vol% or more.

Example 3

The outlet gas containing the unreacted fluorine gas obtained after the direct fluorination reaction in Example 2 was introduced into a nickel reactor having an internal diameter of 20.6 mmΦ and a length of 500 mm. The gas composition was 62.82 NL / hr hydrogen fluoride flow rate, 3.16 NL / hr organic matter flow rate, and about 0.26 NL / hr unreacted fluorine gas flow rate. The reactor temperature was raised to 390 ° C., trifluoromethane such as hydrofluorocarbons were fed at about 0.286 NL / hr from the reactor inlet, and the unreacted fluorine and organic composition were titrated and gas chromatographed. The amount of unreacted fluorine gas in the outlet gas after the reaction with trifluoromethane is 50 ppm or less, and the outlet gas has the composition shown in Table 9.

compound Chemical formula Composition (vol%) Octafluoropropane CF ₃ CF ₂ CF ₃ 91.6849 Tetrafluoromethane CF ₄ 5.2707 Trifluoromethane CHF ₃ 3.0232 Hexafluoroethane CF ₃ CF ₃ 0.0028 2H-heptafluoropropane CF ₃ CHFCF ₃ 0.0029 Chloropentafluoroethane CF ₃ CClF ₂ 0.0006 Perfluorohexane C ₆ F ₁₄ 0.0149

Thereafter, the remaining fluorine gas was removed, and then the outlet gas was washed with an aqueous potassium hydroxide solution to remove hydrogen fluoride. After the acid component was removed, the gas was collected by cooling using a cylinder container and distilled purified to remove the low and high boiling fractions by known methods. The composition obtained after the distillation purification was analyzed by gas chromatography and found to have the composition shown in Table 10.

compound Chemical formula Composition (vol%) Octafluoropropane CF ₃ CF ₂ CF ₃ 99.9993 2H-heptafluoropropane CF ₃ CHFCF ₃ 0.0001 Chloropentafluoroethane CF ₃ CClF ₂ 0.0006

Comparative Example 1

A direct fluorination reaction was carried out to react hexafluoropropene with fluorine gas. A nickel reactor with an internal diameter of 20.6 mmΦ and a length of 500 mm (heated by an electric heater; the reactor undergoes passivation treatment at a temperature of 500 ° C. with fluorine gas) was supplied with nitrogen gas at 60 NL / hr and flowed into a bifurcation 50 Heated at 캜. A gas mainly composed of hexafluoropropane described in Raw Material Example 1 was supplied at a nitrogen gas flow rate of 3.24 NL / hr. Thereafter, fluorine gas was supplied at 3.55 NL / hr at another nitrogen gas flow rate, and a direct fluorination reaction was performed. After 2 hours, the reaction product gas was washed with aqueous potassium hydroxide solution and aqueous potassium iodide solution, and the reaction product was analyzed by gas chromatography by removing unreacted fluorine gas. As a result, the organic material was found to have a gas composition shown in Table 11.

compound Chemical formula Composition (vol%) Octafluoropropane CF ₃ CF ₂ CF ₃ 93.3515 Hexafluoroethane CF ₃ CF ₃ 0.0063 Chlorotrifluoromethane CClF ₃ 0.0039 Chloropentafluoroethane CF ₃ CClF ₂ 0.0204 Dichlorotetrafluoroethane CF ₃ CCl ₂ F 0.0011 Perfluorohexane C ₆ F ₁₄ 6.6122 Octafluorocyclobutane C ₄ F ₈ 0.0046

As shown in the results shown in Table 11, the method for producing octafluoropropane by directly fluorinating hexafluoropropene and fluorine gas was found to be polymerized, cyclized, and yields decreased.

Thereafter, after removing the acid component, the gas was collected by cooling using a cylinder container, and distillation purification was performed to remove a low boiling point fraction and a high boiling point fraction by a known method. The composition obtained after distillation purification was analyzed by gas chromatography and found to have the composition shown in Table 12.

compound Chemical formula Composition (vol%) Octafluoropropane CF ₃ CF ₂ CF ₃ 99.9768 Chloropentafluoroethane CF ₃ CClF ₂ 0.0218 Octafluorocyclobutane C ₄ F ₈ 0.0022

As shown in the results in Table 12, it is difficult to separate and purify to high purity by separating octafluoropropane, chloropentafluoroethane as chlorine compounds and octafluorocyclobutane as ring compounds.

Example 4

The reaction was carried out under the same conditions as in Example 1 except that the hexafluoropropene raw material was changed to Raw Material Example 2. The gas was analyzed after removing the acid component and found to have the composition of Table 13.

compound Chemical formula Composition (vol%) 2H-heptafluoropropane CF ₃ CHFCF ₃ 99.9079 Trifluoromethane CHF ₃ 0.0098 Hexafluoroethane CF ₃ CF ₃ 0.0414 Pentafluoroethane CF ₃ CHF ₂ 0.0028 Chlorotrifluoroethane CClF ₃ 0.0236 Octafluoropropane CF ₃ CF ₂ CF ₃ 0.0005 Hexafluoropropene CF ₃ CF = CF ₂ 0.0049 Chloropentafluoroethane CF ₃ CClF ₂ 0.0004 Tetrafluoroethane CF ₃ CH ₂ F 0.0029 Dichlorodifluoromethane CCl ₂ F ₂ 0.0012 Chlorotetrafluoroethane CF ₃ CHClF 0.0005 Chlorotrifluoroethane CF ₃ CH ₂ Cl 0.0041

After the acid component was removed, the gas was collected by cooling using a cylinder container and distilled purified to remove the low and high boiling fractions by known methods. The composition obtained after purification was analyzed by gas chromatography and observed as shown in Table 14.

compound Chemical formula Composition (vol%) 2H-heptafluoropropane CF ₃ CHFCF ₃ 99.9925 Pentafluoroethane CF ₃ CHF ₂ 0.0009 Octafluoropropane CF ₃ CF ₂ CF ₃ 0.0002 Hexafluoropropene CF ₃ CF = CF ₂ 0.0016 Chloropentafluoroethane CF ₃ CClF ₂ 0.0014 Tetrafluoroethane CF ₃ CH ₂ F 0.0025 Dichlorodifluoromethane CCl ₂ F ₂ 0.0009

From the results shown in Table 14, the salt compound contained as an impurity in 2H-heptafluoropropane can be distilled to reduce the amount to 0.01 vol% or less.

Example 5

The reaction was carried out under the same operations and conditions as in Example 2, except that the purified product described in Example 4 was used instead of 2H-heptafluoropropane. After the acid component was removed, the gas was collected by cooling using a cylinder container and purified by distillation to remove the low and high boiling fractions by known methods. The resulting composition was analyzed by gas chromatography and found to have the composition shown in Table 15.

compound Chemical formula Composition (vol%) Octafluoropropane CF ₃ CF ₂ CF ₃ 99.9979 Chloropentafluoroethane CF ₃ CClF ₂ 0.0015 Dichlorodifluoromethane CCl ₂ F ₂ 0.0006

As shown in the results in Table 15, octafluoropropane with a purity of 99.995 vol% or more can be obtained.

As described above, by using the method of the present invention, high purity octafluoropropane can be prepared using hexafluoropropene containing impurities in the presence of chlorine, and high purity octafluoropropane produced using the present invention. May be used as an etching or cleaning gas in the manufacturing process of semiconductor devices.

Claims (20)

(1) 150 to hexafluoropropene and hydrogen fluoride in the gas phase in the presence of a fluorinated catalyst which is a bulk catalyst obtained by adding at least one member selected from the group consisting of indium, zinc and nickel as the main component of chromium oxide; Reacting at a temperature of 450 ° C. to obtain 2H-heptafluoropropane, (2) preparing octafluoropropane, comprising reacting 2H-heptafluoropropane obtained in step (1) with fluorine gas in a gaseous phase at a temperature of 250 to 500 ° C. without a catalyst. Way. The method of claim 1, wherein the hexafluoropropene is at least one selected from the group consisting of dichlorodifluoromethane, chlorodifluoromethane, chloropentafluoroethane, chlorotetrafluoroethane and chlorotrifluoroethylene. Containing a compound. delete The process according to claim 1, wherein the molar ratio of hydrogen fluoride / hexafluoropropene in step (1) is in the range of 0.8 to 3: 1. The method of claim 1 further comprising the step of removing impurities contained in 2H-heptafluoropropane prior to step (2). 6. The method of claim 5 wherein the impurity is at least one compound selected from the group consisting of tetrafluoromethane, trifluoromethane, chlorotrifluoromethane, hexafluoroethane and pentafluoroethane. 7. The process of claim 5 or 6 wherein the step of removing impurities contained in 2H-heptafluoropropane is a distillation process. The method of claim 1. The chlorine compound contained in 2H-heptafluoropropane is 0.01 vol% or less. The process of claim 1, wherein step (2) is carried out in the presence of a diluent gas, the diluent gas being at least one gas selected from the group consisting of hydrogen fluoride, tetrafluoromethane, hexafluoroethane and octafluoropropane. How to be. The process according to claim 1, wherein the molar ratio of fluorine gas / 2H-heptafluoropropane in step (2) is in the range of 0.9 to 1.5: 1. The process of claim 1 wherein the reactor inlet concentration of 2H-heptafluoropropane in step (2) is 8 mol% or less. The process of claim 1 wherein at least some of the outlet gas of step (2) is circulated and reused as the diluent gas of step (2). The process of claim 1 comprising reacting at least a portion of the outlet gas of step (2) with at least one hydrofluorocarbon to remove unreacted fluorine gas contained in the outlet gas. The method of claim 13, wherein the hydrofluorocarbon is selected from the group consisting of trifluoromethane, tetrafluoroethane, pentafluoroethane and 2H-heptafluoropropane. The process according to claim 1, wherein the hydrogen fluoride contained in the outlet gas of step (2) is separated and the separated hydrogen fluoride is returned to step (1) and / or step (2). The method of claim 1, wherein at least a portion of the octafluoropropane is separated from the gas from which the hydrogen fluoride is separated and the remaining gas is returned to step (1) and / or step (2). delete delete delete delete