JP2002069014A - Method for producing octafluoropropane and applicatoin thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing octafluoropropane to be used in the production process for semiconductor devices, and to provide a high-purity octafluoropropane produced by the method, and to provide its applications. SOLUTION: This method for producing octafluoropropane comprises the step (1) of reacting hexafluoropropene with hydrogen fluoride in a vapor phase at 150-450 deg.C in the presence of a fluorinating catalyst, to form 2H- heptafluoropropane and step (2) of reacting the 2H-heptafluoropropane obtained in the step (1) with a fluorine gas in the absence of catalyst in a vapor phase at 250-500 deg.C to obtain the objective octafluoropropane.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing octafluoropropane, an octafluoropropane product and its use.

[0002]

2. Description of the Related Art Octafluoropropane is used, for example, as a dry etching gas or a cleaning gas in a semiconductor device manufacturing process. The production method includes: (1) a method of directly fluorinating hexafluoropropene with fluorine gas (Japanese Patent Publication No. 62-15772); and (2) a method of electrolytically fluorinating hexafluoropropene in hydrogen fluoride. (Japanese Patent Publication No. 62-61115) (3) A method of reacting hexafluoropropene with fluorine in the presence of a catalyst (Japanese Patent Publication No. 45455/1992) (4) Reacting hexafluoropropene with a higher metal fluoride A method (Japanese Patent Publication No. 62-54777) is known.

[0003] However, these methods use tetrafluoromethane (CF ₄ ), hexafluoroethane (C ₂ F).
₆ ) and the like are generated by cleavage, radical addition produces C ₆ F ₁₂ , C ₆ F _{14 and the} like, and cycloaddition produces a four-membered ring and the like. Propane yield and selectivity decrease. Furthermore, among these impurities, there are compounds that are difficult to separate by a distillation operation, and there is a problem that it is difficult to obtain high-purity octafluoropropane. In particular, when hexafluoropropene is used as a starting material, chloropentafluoroethane (CFC-1) contained as an impurity is used.
15) hardly reacts with fluorine gas and is contained in octafluoropropane, which is the target substance, and it is difficult to separate by distillation operation due to its close boiling point. Therefore, it is difficult to obtain high-purity octafluoropropane. It was difficult.

[0004]

SUMMARY OF THE INVENTION The present invention has been made under such a background, and the present invention relates to a method for producing octafluoropropane used in a semiconductor device manufacturing process, a high-purity octafluoropropane. It is an object to provide propane and its use.

[0005]

The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, (1) in the presence of a fluorination catalyst, hexafluoropropene and hydrogen fluoride in the gaseous phase in 150-150. Reaction at 450 ° C. to obtain 2H-heptafluoropropane, (2) 2H obtained in step (1)
A step of obtaining octafluoropropane by reacting heptafluoropropane and fluorine gas in a gas phase at 250 to 500 ° C. in the absence of a catalyst to obtain octafluoropropane, and found that high-purity octafluoropropane can be produced by using a production method, The present invention has been completed.

That is, the present invention (I) comprises (1) a step of reacting hexafluoropropene and hydrogen fluoride in the gas phase at 150 to 450 ° C. in the presence of a fluorination catalyst to obtain 2H-heptafluoropropane; (2) reacting 2H-heptafluoropropane obtained in step (1) with fluorine gas in the gas phase at 250 to 500 ° C. in the absence of a catalyst to obtain octafluoropropane. A method for producing fluoropropane, wherein in the present invention (I), hexafluoropropene is at least one selected from the group consisting of dichlorodifluoromethane, chlorodifluoromethane, chloropentafluoroethane, chlorotetrafluoroethane and chlorotrifluoroethylene. , And a fluorinated catalyst in step (1). Is a bulk catalyst containing chromium oxide as a main component, and at least one selected from the group consisting of indium, zinc and nickel, and a hydrogen fluoride / hexafluoropropene molar ratio. It is a preferred embodiment that the ratio is in the range of 0.8 to 3.

In the present invention (I), the step (2)
Before the step of removing impurities contained in 2H-heptafluoropropane, wherein the impurities are selected from the group consisting of tetrafluoromethane, trifluoromethane, chlorotrifluoromethane, hexafluoroethane and pentafluoroethane. It is a preferred embodiment that the compound is at least one compound, the step of removing the impurities is a distillation step, and the chlorine compound contained in 2H-heptafluoropropane is 0.01 vol% or less.

In the present invention (I), the step (2)
Is performed in the presence of a diluent gas, wherein the diluent gas is
Being at least one member selected from the group consisting of hydrogen fluoride, tetrafluoromethane, hexafluoroethane, and octafluoropropane; in step (2), the molar ratio of fluorine gas / 2H-heptafluoropropane is 0.9 to 0.9; It is a preferred embodiment that the range is 1.5 and the concentration of 2H-heptafluoropropane at the reactor inlet is 8 mol% or less.

Furthermore, in the present invention (I), at least a part of the outlet gas of the step (2) is circulated and reused as a diluent gas of the step (2), and at least one of the outlet gases of the step (2) is used. Part and reacting the hydrofluorocarbons, including a step of removing unreacted fluorine gas in the outlet gas, the hydrofluorocarbons,
Being at least one compound selected from the group consisting of trifluoromethane, tetrafluoroethane, pentafluoroethane, and 2H-heptafluoropropane; and separating and separating hydrogen fluoride contained in the outlet gas of step (2). Hydrogen fluoride in step (1) and / or step (2)
It is a preferred embodiment to return to the above, to separate at least a part of octafluoropropane from the gas from which hydrogen fluoride has been separated, and to return the remaining gas to the step (1) and / or the step (2).

The present invention (II) has a purity of 99.995 vo.
An octafluoropropane product containing 1% or more of octafluoropropane, wherein the total amount of a compound containing a chlorine atom in a molecule and a cyclic compound is 5%.
A preferred embodiment is below 0 volppm. Further, the present invention (III) is an etching gas containing the above octafluoropropane product, and the present invention (IV) is a cleaning gas containing the above octafluoropropane product. Gas.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. Hexafluoropropene used in the present invention _{(I) (CF 3 CF =} CF 2) , for example chlorodifluoromethane sub in the production step of tetrafluoroethylene (CF ₂ = CF ₂₎ by the thermal decomposition of (CHClF ₂₎ Biological Or propane, propylene or partially halogenated C3 non-cyclic hydrocarbons obtained by chlorofluorination to dehalogenate as described in JP-A-4-14503. Is obtained by However, hexafluoropropene obtained by these methods contains impurities such as dichlorodifluoromethane, chlorodifluoromethane, chloropentafluoroethane, chlorotetrafluoroethane, and chlorotrifluoroethylene, which contain chlorine atoms in the molecule. Often have. The present invention provides a process for producing octafluoropropane from hexafluoropropene, which may contain these impurities, as a starting material. Here, an intermediate 2H-heptafluoropropane and a target octafluoropropane are provided. Table 1 shows the boiling points of fluoropropane and these impurities.

[0012]

[Table 1] As is clear from the boiling point shown in Table 1, the boiling point of the compound containing a chlorine atom in the molecule contained in the starting material hexafluoropropene is close to the boiling point of octafluoropropane, and it is difficult to separate the compound by distillation alone. It is.

Therefore, the process for producing octafluoropropane according to the present invention (I) comprises first reacting hexafluoropropene and hydrogen fluoride in the gas phase in the presence of a fluorination catalyst at a reaction temperature of 1: 1.
Step (1) of reacting at 50 to 450 ° C. to obtain 2H-heptafluoropropane is performed. Step (1) has the following two points. That is, [1] when hexafluoropropene is directly fluorinated with fluorine gas, or when directly fluorinated with fluorine gas in the presence of a catalyst or a higher metal fluoride, a cleavage reaction of a carbon-carbon bond, Various by-products are generated by a radical addition reaction, a cycloaddition reaction and the like. For this reason, it has been difficult not only to reduce the yield and the selectivity but also to obtain high-purity octafluoropropane. The present invention suppresses the generation of by-products due to these reactions by adding hydrogen fluoride to hexafluoropropene in the presence of a catalyst to obtain 2H-heptafluoropropane as an intermediate with high yield and selectivity. be able to.

[2] As described above, hexafluoropropene often contains a compound containing a chlorine atom in the molecule as an impurity, and it is difficult to separate these compounds by distillation. . In the present invention, hydrogen fluoride is added to hexafluoropropene to give an intermediate 2
At the same time as the reaction for obtaining H-heptafluoropropane, a compound containing a chlorine atom in the molecule can be fluorinated using hydrogen fluoride and converted into a compound that can be easily separated by distillation.

The reaction of adding hydrogen fluoride to hexafluoropropene proceeds 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 that is usually used can be used. Hexafluoropropene contains chlorine-based impurities, and when the chlorine-based impurities are fluorinated and converted to other compounds, the reaction temperature is higher, so the activity (performance) and stability (lifetime) As an excellent catalyst, it is preferable to use a bulk catalyst comprising a chromium oxide as a main component and adding at least one of indium, zinc and nickel thereto. A supported catalyst (for example, an alumina carrier) may be used, but a bulk catalyst is preferred in view of activity and stability. These catalysts can be activated for fluorination treatment with hydrogen fluoride before use in the reaction and used in the reaction.

In step (1), it depends on the type and content of impurities in hexafluoropropene.
The reaction temperature ranges from 150 to 450 ° C, preferably from 200 to 350 ° C. When CFC-115 is contained as an impurity in hexafluoropropene, the reaction temperature is preferably in the range of 350 to 450 ° C, and more preferably 350 to 400 ° C. When the reaction temperature is 450 ° C. or higher, the stability of the catalyst tends to decrease, which is not preferable. On the other hand, when the temperature is 150 ° C. or lower, the conversion of the target reaction is reduced, and the fluorination reaction of the impurity compound is slow. The molar ratio of hydrogen fluoride to hexafluoropropene (FC-1216) (HF / FC-121
6) is preferably 0.8 to 3.0, more preferably 1.0 to 2.0. If the molar ratio of hydrogen fluoride to hexafluoropropene is 0.8 or less, the conversion of hexafluoropropylene decreases, and if the molar ratio is 3.0 or more, the cost of the unreacted HF recovery equipment increases, which is not preferable.

As described above, hexafluoropropene as a raw material may contain a compound containing a chlorine atom in a molecule as an impurity, and it is usually difficult to separate these impurities by a distillation operation. Examples of the compound containing a chlorine atom in the molecule include chlorodifluoromethane, chloropentafluoroethane, dichlorodifluoromethane, chlorotrifluoroethylene, chlorotetrafluoroethane, and the like. The present invention (I) is a step of reacting hexafluoropropene, which is the main reaction, with hydrogen fluoride in the presence of a fluorination catalyst to obtain 2H-heptafluoropropane, and distilling these chlorine-containing compounds in a distillation step. Convert to other fluorine compounds that are easy to separate.

For example, a chlorine compound can be converted to another fluorine compound by the following reactions (2) to (5). CHClF ₂ + HF → CHF ₃ + HCl (2) CF ₂ = CCIF + 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) Table 2 shows the boiling points of these fluorinated compounds and the intermediate, 2H-heptafluoropropane.

[0019]

[Table 2] As is clear from Table 2, the intermediate 2H-heptafluoropropane and the compound fluorinated according to the above reaction clearly have a large difference in boiling point, and can be easily separated by distillation.

Next, the gas containing 2H-heptafluoropropane as a main component obtained in the step (1) is led to a deoxidizing step for separating hydrogen chloride and unreacted hydrogen fluoride.
Hydrogen chloride and hydrogen fluoride are further separated by distillation, and hydrogen chloride is neutralized with an aqueous alkali solution. Hydrogen fluoride may be returned to the step of fluorinating hexafluoropropene, or may be neutralized with an aqueous alkali solution.
After separating hydrogen chloride and hydrogen fluoride in the deacidification step, 2H-
The gas containing heptafluoropropane as a main component is subsequently subjected to the step (2), but before that, it is led to a distillation column and 2H-
It is preferable to remove impurities contained in heptafluoropropane.

The impurities contained in 2H-heptafluoropropane include tetrafluoromethane, trifluoromethane, chlorotrifluoromethane, hexafluoroethane, pentafluoroethane and the like, and these impurities can be removed by distillation. preferable. In the distillation column, tetrafluoromethane, trifluoromethane, chlorotrifluoromethane, hexafluoroethane, and pentafluoroethane, which have low boiling points, are extracted from the top of the distillation column, and 2H-heptafluoropropane is extracted from the bottom. It is. The gas containing 2H-heptafluoropropane as a main component is used as a raw material for a direct fluorination reaction with fluorine gas, and is contained in 2H-heptafluoropropane regardless of the presence or absence of distillation after the deoxidizing step. The chlorine compound as an impurity is preferably 0.01 vol% or less, more preferably 0.005 vol%.
% Or less.

Next, the step (2) will be described. In the step (2), octafluoropropane is obtained by reacting 2H-heptafluoropropane obtained in the fluorination step of the above step (1) with fluorine gas at a reaction temperature of 250 to 500 ° C. in the gas phase without using a catalyst. This is a direct fluorination reaction step and has the following three points. That is, [1] When a perfluorocarbon is produced by reacting a hydrofluorocarbon with a fluorine gas, very large heat of reaction is involved. The heat of reaction is proportional to the number of moles of reacting fluorine per molecule, and the larger the amount of fluorine, the greater the heat of reaction, which tends to cause carbon-carbon bond cleavage, polymerization, cycloaddition, and, in some cases, explosion. In addition, the yield is reduced, which causes problems in industrial production and operation. For this reason, as a method for suppressing rapid generation of reaction heat in the direct fluorination method, there are a method of diluting fluorine with another inert gas (for example, nitrogen, helium, etc.) and a method of diluting an organic substance as a substrate. The inert gas such as nitrogen and helium is not an advantageous method from the viewpoint of cost in consideration of separation and purification in the distillation step from perfluorocarbon as a target substance, and the present invention (I)
Can solve the above problem by using at least one selected from hydrogen fluoride, tetrafluoromethane, hexafluoroethane, and octafluoropropane as a diluent gas.

[2] In the present invention (I), the reaction substrate 2
The reaction is carried out by reducing the concentration of H-heptafluoropropane at the inlet of the reactor with a diluent gas to an explosion range or less, specifically, to 8 mol% or less. As described above, the direct fluorination reaction using fluorine gas uses extremely reactive fluorine gas, so the organic compound (particularly, a compound containing hydrogen) serving as a substrate burns or explodes when exposed to fluorine gas. There is a risk of doing. In step (2), since 2H-heptafluoropropane containing a hydrogen atom is used as a substrate, prevention of explosion of 2H-heptafluoropropane and fluorine gas is an important point. In order to prevent the explosion, it is necessary to prevent the mixed gas composition from being within the explosion range. The present inventors have studied the explosion range between 2H-heptafluoropropane and fluorine gas, and found that
The lower limit of the explosion range of H-heptafluoropropane was found to be 8 mol% or less, and a safe range for the reactor inlet concentration of 2H-heptafluoropropane can be set.

[3] In the direct fluorination reaction of reacting 2H-heptafluoropropane with fluorine gas, the use of excess 2H-heptafluoropropane relative to fluorine gas eliminates the need for a step of removing fluorine gas. ,
This brings great difficulty to subsequent separation and purification. In step (2) of the present invention (I), an excess molar amount of fluorine gas can be used relative to 2H-heptafluoropropane in order to increase the reaction efficiency. The reaction product gas flowing out of the reaction step mainly contains excess fluorine gas in addition to perfluorocarbon and hydrogen fluoride. As a method of treating an excessive amount of fluorine gas, a method of reacting with an inorganic oxide such as alumina and soda lime is known, but this method generates water by the reaction, which causes corrosion of equipment materials and the like. Is not preferred. In the present invention (I), the excess fluorine gas can be removed by contacting it with a 1.1 times molar equivalent of hydrofluorocarbon with respect to the excess fluorine gas.

The direct fluorination reaction of reacting 2H-heptafluoropropane with fluorine gas is represented by the following formula (6)
Proceed according to. CF ₃ CHFCF ₃ + F ₂ → CF ₃ CF ₂ CF ₃ + HF (6) This reaction may be carried out without a catalyst, although a catalyst may be used. Further, as described above, the direct fluorination reaction for reacting hydrofluorocarbon and fluorine gas has a large heat of reaction, and it is preferable to carry out the reaction in the presence of a diluent gas. Hydrogen fluoride, tetrafluoromethane, hexafluoroethane, at least one selected from octafluoropropane can be used as the diluting gas,
Preferably, hydrogen fluoride and / or octafluoropropane is used, and more preferably, a gas rich in hydrogen fluoride is used.

Before introducing 2H-heptafluoropropane and fluorine gas into the reactor, one or both of them are diluted with a diluent gas and then introduced into the reactor. The concentration of 2H-heptafluoropropane as a substrate at the inlet of the reactor is preferably 8 mol% or less, which is less than the explosion range, and more preferably 6% or less. 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, and more preferably 0.9 to 1.5.
A concentration in the range of 2 is preferred. When the fluorine concentration is such that the molar ratio of fluorine gas / 2H-heptafluoropropane is 0.9 or less, the conversion of 2H-heptafluoropropane becomes low. . When the molar ratio of fluorine gas / 2H-heptafluoropropane is 1.5 or more, when the outlet gas of step (2) is circulated and reused as the diluent gas of step (2), the circulating gas (diluent gas) This is not preferable because the concentration of fluorine therein becomes high and problems such as explosion occur.

2H-heptafluoropropane diluted with a diluent gas to a concentration below the explosion range and fluorine gas can react in the gas phase. The reaction temperature is preferably from 250 to 500C, preferably from 350 to 450C. When the reaction temperature is 250 ° C. or lower, the reaction is slow, and when the reaction temperature is 500 ° C. or higher, the cleavage of the carbon-carbon bond of octafluoropropane, which is the target substance, tends to proceed, which is not preferable.

The outlet gas in this step (2) is mainly hydrogen fluoride and octafluoropropane.
Can circulate at least a part of this outlet gas and reuse it as a diluent gas in the step (2). In addition, since unreacted fluorine gas may be contained in the outlet gas, as a method of detecting the concentration of unreacted fluorine gas, only a small part of the outlet gas is added to a solution containing a metal iodide which continuously flows. Is continuously introduced to generate iodine, and a method of continuously quantifying the generated iodine by measuring the transmittance of visible light of a specific wavelength range of the solution to calculate the concentration of unreacted fluorine gas is used. Can be. In addition, as a method of detecting a fluorine compound and obtaining a reaction rate, a method of measuring the concentration of perfluorocarbon, hydrofluorocarbon, and hydrogen fluoride contained in a mixed gas using infrared spectroscopy can be used. Continuous operation can be performed under safe conditions.

The outlet gas in the step (2) may be recycled and reused as a diluent gas, and when it contains unreacted fluorine gas, for example, about the same amount of 2H-heptafluoropropane as the supplied It is preferable that the outlet gas is extracted to lead to a step of removing unreacted fluorine, and the excess fluorine gas is contacted with 1.1 times mol of hydrofluorocarbon in a stoichiometric ratio to remove the fluorine gas. The contact temperature in the fluorine gas removal step varies depending on the type of hydrofluorocarbon, but is preferably 250 to 500.
C, more preferably 350 to 450C. The fluorine concentration in the outlet gas after the fluorine removal step is usually 50 ppm
Or less, and can be 10 ppm or less depending on conditions. As the hydrofluorocarbon to be reacted with an excessive fluorine gas, trifluoromethane, tetrafluoroethane, pentafluoroethane, and 2H-heptafluoropropane can be used.

The outlet gas of the step (2) is, except for a part of the gas reused as a diluent gas in the step (2), if a fluorine gas remains, passes through a fluorine removal step and then to a decompression step. Be guided. The main components of the gas are hydrogen fluoride and octafluoropropane. In the condensation step, hydrogen fluoride is separated into liquid by cooling, and octafluoropropane is mainly separated as a gas. The separated hydrogen fluoride is subjected to a fluorination step (1) and / or a direct fluorination step (2).
And can be reused by circulation. The gas mainly containing octafluoropropane separated as a gas passes through a dehydration step and is pressurized by a compressor and introduced into a distillation column.

The gas mainly containing octafluoropropane introduced into the distillation column has, for example, a low-boiling component extracted from the top in the first distillation column. Examples of low boiling components include inert gas, tetrafluoromethane, hexafluoroethane, and the like, which can be directly used as a diluent gas in the fluorination step (2). On the other hand, the gas containing octafluoropropane as the main component extracted from the bottom is led to the second distillation column, where octafluoropropane is extracted as a low-boiling component from the top of the second distillation column, and goes to the product process. Be guided. The high-boiling components extracted from the bottom in the second distillation column can be returned to the step (2) and used as a diluent gas, and in some cases, may be subjected to a decomposition treatment using a harmless agent or the like.

Octafluoropropane, which is the target product led to the product process, is further purified if necessary, and in some cases is led to a product tank through a dehydration process. Octafluoropropane guided to the product tank is analyzed by using an analysis method such as (1) TCD method, FID method and ECD method of gas chromatography (GC), and (2) gas chromatography-mass spectrometer (GC-MS). To determine the purity. The present invention (II) provides a purity of 99.995 vol obtained by using the production method of the present invention (I).
% Of high-purity octafluoropropane, and impurities contained in octafluoropropane include a compound containing a chlorine atom in a molecule and a cyclic compound in a total amount of 50 v
olppm or less, and the total amount of these impurities is 10 vol.
It can be below ppm.

Next, the present invention (III) and (IV)
The use of high-purity octafluoropropane obtained by using the production method of the present invention (I) will be described. The present invention (I
The high-purity octafluoropropane of I) can be used as an etching gas in an etching step in a semiconductor device manufacturing process. It is also used as a cleaning gas in a cleaning step in a semiconductor device manufacturing process. In a manufacturing process of a semiconductor device such as an LIS or a TFT, a thin film or a thick film is formed by using a CVD method, a sputtering method, an evaporation method, or the like, and etching is performed to form a circuit pattern. In an apparatus for forming a thin film or a thick film, cleaning is performed to remove unnecessary deposits accumulated on the inner wall of the apparatus, a jig, a pipe, and the like. This is because the generation of unnecessary deposits causes the generation of particles, and it is necessary to remove the deposits as needed to produce a high-quality film. When used as an etching or cleaning gas, the octafluoropropane of the present invention may be diluted with an inert gas such as He, Ar, N ₂ or the like, or may be diluted with F ₂ , NF ₃ , C ₂ F ₄ , HCl, O ₂ or the like.
_2, were mixed in suitable proportions and gas H ₂ or the like may be used.

[0034]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples, but the present invention is not limited to these Examples. [Raw material example 1] HFP (hexafluoropropene) obtained as a by-product in a process of producing TFE (tetrafluoroethylene) by pyrolyzing HCFC-22 (CHClF ₂ ) together with water vapor on alumina with steam, and after performing a distillation operation A raw material hexafluoropropene having the composition shown in Table 3 was obtained.

[0035]

[Table 3]

[Raw material example 2] When commercially available hexafluoropropene was analyzed, it had the composition shown in Table 4.

[Table 4]

[0037] container 10L containing the pure water 0.6 L [Production of a fluorination catalyst], Cr (NO ₃₎ of 452 g ₃ · 9H
While stirring a solution obtained by dissolving ₂ O and 42 g of In (NO ₃ ) ₃ .nH ₂ O (n is about 5) in 1.2 L of pure water, and 0.31 L of 28% ammonia water, stirring the reaction solution PH is 7.5-
The two aqueous solutions were added dropwise over about one hour while controlling the flow rates of the two aqueous solutions so as to be in the range of 8.5. The obtained hydroxide slurry is separated by filtration, washed well with pure water,
Dry at 120 ° C. for 12 hours. After crushing the obtained solid,
It was mixed with graphite and pelletized by a tablet press. The pellet was fired at 400 ° C. for 4 hours under a nitrogen stream to obtain a catalyst precursor. The catalyst precursor was charged into an Inconel reactor, and at 350 ° C. under normal pressure under a nitrogen-diluted HF gas stream,
Next, a fluorination treatment (catalyst activation treatment) was performed under a 100% HF stream to prepare a catalyst.

Example 1 An Inconel 600 type reactor having an inner diameter of 1 inch and a length of 1 m was charged with 100 ml of the catalyst prepared by the method shown in the above [Production of fluorination catalyst], and the temperature was increased while flowing nitrogen. Was set to 400 ° C. Hydrogen fluoride was supplied at 6.32 NL / hr, and then [raw material example 1].
Was supplied at a rate of 3.24 NL / hr. The supply of nitrogen gas was stopped, and the reaction was started. Two hours later, the exhaust gas was washed with an aqueous potassium hydroxide solution to remove acid components, and the gas composition was analyzed by gas chromatography. As a result, a gas having the composition shown in Table 5 was obtained.

[0039]

[Table 5]

The gas from which the acid content had been removed was collected by cooling using a cylinder vessel, and distillation purification was performed by a known method to cut low boiling and high boiling components. When the composition obtained after the purification by distillation was analyzed by gas chromatography, it had the composition shown in Table 6.

[0041]

[Table 6] From the results shown in Table 6, the impurity chlorine compound contained in 2H-heptafluoropropane was subjected to a distillation operation,
It turned out that it can be set to 0.01 vol% or less.

Example 2 Using the gas obtained in Example 1 and containing 2H-heptafluoropropane as a main component after distillation, a direct fluorination reaction with fluorine gas was performed. Nickel reactor having an inner diameter of 20.6 mmΦ and a length of 500 mm (electric heater heating: the reactor is a fluorine gas at a temperature of 500
At 20 ° C.) and nitrogen gas at 20 NL / hr.
While supplying, the temperature was set to 400 ° C. Next, hydrogen fluoride (diluting gas) was bifurcated and supplied at 60 NL / hr, and the gas containing 2H-heptafluoropropane as a main component was supplied at 3.24 NL / hr to one gas. Then, fluorine gas is added to the other hydrogen fluoride gas flow.
The gas was supplied at 55 NL / hr, the supply of nitrogen gas was stopped, and a direct fluorination reaction was performed. After 3 hours, the reaction product gas was washed with an aqueous solution of potassium hydroxide and an aqueous solution of potassium iodide, hydrogen fluoride and unreacted fluorine gas were analyzed, and then acid components were removed and analyzed by gas chromatography. However, the gas composition of the organic substance was as shown in Table 7.

[0043]

[Table 7]

On the other hand, the amount of unreacted fluorine gas in the reaction outlet gas was 0.26 NL / hr. The gas from which the acid content had been removed was collected by cooling using a cylinder vessel, and distillation purification was performed by a known method to cut low boiling and high boiling components. When the composition obtained after the distillation purification was analyzed by gas chromatography, it had the composition shown in Table 8.

[0045]

[Table 8] From the results shown in Table 8, it was found that the purity of the obtained octafluoropropane was 99.999 vol% or more.

Example 3 The outlet gas of the direct fluorination reaction containing the unreacted fluorine gas obtained in Example 2 was introduced into a nickel reactor having an inner diameter of 20.6 mm and a length of 500 mm. The gas composition was 62.82 NL / h of hydrogen fluoride.
r, organic matter 3.16 NL / hr, unreacted fluorine gas about 0.26 NL / hr, the reactor temperature was raised to 390 ° C., and trifluoromethane as hydrofluorocarbon was added at about 0.286 NL / hr through the reactor inlet. hr, and the unreacted fluorine and organic composition were analyzed by titration and gas chromatography, respectively. The amount of unreacted fluorine gas in the outlet gas after reacting with trifluoromethane is 50
ppm or less, and the gas composition was as shown in Table 9.

[0047]

[Table 9]

Next, the outlet gas from which the remaining fluorine gas was removed was washed with an aqueous potassium hydroxide solution to remove hydrogen fluoride. The gas from which the acid content had been removed was collected by cooling using a cylinder vessel, and distillation purification was performed by a known method to cut low boiling and high boiling components. The gas obtained after the purification by distillation was analyzed by gas chromatography and found to have the composition shown in Table 10.

[0049]

[Table 10]

Comparative Example 1 A direct fluorination reaction was performed in which hexafluoropropene was reacted with fluorine gas. Nickel reactor having an inner diameter of 20.6 mmΦ and a length of 500 mm (electric heater heating: the reactor is a fluorine gas at a temperature of 500
The temperature was set to 50 ° C. while supplying nitrogen gas in two branches at 60 NL / hr. A gas containing hexafluoropropene as a main component shown in [Raw material example 1] is supplied to one nitrogen gas stream at 3.24 NL / hr,
Next, fluorine gas was added to the other nitrogen gas stream at 3.55N.
L / hr and the fluorination reaction was performed directly. Two hours later, the reaction product gas was washed with an aqueous solution of potassium hydroxide and an aqueous solution of potassium iodide to remove unreacted fluorine gas, and analyzed by gas chromatography. The gas composition was as shown in Table 11. .

[0051]

[Table 11] As is clear from the results shown in Table 11, the method of producing octafluoropropane by directly fluorinating hexafluoropropene and fluorine gas may cause polymerization, cycloaddition, and the like, and the yield may be reduced. Do you get it.

Next, the gas from which the acid content had been removed was collected by cooling using a cylinder vessel, and distillation purification was performed by a known method to cut low boiling and high boiling components. When the composition obtained after the distillation purification was analyzed by gas chromatography, it had the composition shown in Table 12.

[Table 12] As is clear from the results in Table 12, it is difficult to separate octafluoropropane from chloropentafluoroethane, which is a chlorine compound, and octafluorocyclobutane, which is a cyclic compound, and to purify them with high purity.

Example 4 A reaction was conducted under the same operation and conditions as in Example 1 except that the raw material for hexafluoropropene was changed to [Raw material example 2], and the gas after acid removal was analyzed. The composition shown in FIG.

[Table 13]

The gas from which the acid content has been removed is collected by cooling using a cylinder vessel, subjected to distillation purification in which low-boiling and high-boiling components are cut off by a known method, and the composition obtained after the distillation purification is subjected to gas chromatography. As a result of the analysis at-, it had the composition shown in Table 14.

[Table 14] From the results shown in Table 14, chlorine compounds as impurities contained in 2H-heptafluoropropane were distilled,
It turned out that it can be set to 0.01 vol% or less.

(Example 5) 2H-Heptafluoropropene was reacted under the same operation and conditions as in (Example 2) except that the purified distilled product of (Example 4) was used, and the gas after removing the acid component was removed. The composition obtained by cooling and collecting in a cylinder and purifying by distillation to cut low-boiling components and high-boiling components by a known method was analyzed by gas chromatography to find that it had the composition shown in Table 15.

[Table 15] As is apparent from the results shown in Table 15, the purity was 99.
Octafluoropropane having a content of 995 vol% or more can be obtained.

[0056]

As described above, according to the method of the present invention, high-purity octafluoropropane can be produced using hexafluoropropene which may contain chlorine-based impurities. High-purity octafluoropropane manufactured by using the method described above can be used as an etching gas or a cleaning gas in a semiconductor device manufacturing process.

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Claims (20)

[Claims] 1. A method for producing octafluoropropane, comprising the following two steps. (1) Hexafluoropropene and hydrogen fluoride are reacted in the gas phase at 150 to 450 ° C. in the presence of a fluorination catalyst,
Step of obtaining H-heptafluoropropane (2) 250-500 ° C. in the gas phase without using 2H-heptafluoropropane and fluorine gas obtained in step (1) in the presence of a catalyst.
Obtaining octafluoropropane by reacting with 2. The method according to claim 1, wherein the hexafluoropropene contains at least one compound selected from the group consisting of dichlorodifluoromethane, chlorodifluoromethane, chloropentafluoroethane, chlorotetrafluoroethane and chlorotrifluoroethylene. Item 10. The method for producing octafluoropropane according to Item 1. 3. The method according to claim 1, wherein in the step (1), the fluorination catalyst contains chromium oxide as a main component, and comprises indium,
At least one selected from the group consisting of zinc and nickel
The method for producing octafluoropropane according to claim 1 or 2, which is a bulk catalyst obtained by adding a seed. 4. The process for producing octafluoropropane according to claim 1, wherein in the step (1), the molar ratio of hydrogen fluoride / hexafluoropropene is in the range of 0.8 to 3. 5. The method for producing octafluoropropane according to claim 1, further comprising a step of removing impurities contained in 2H-heptafluoropropane before the step (2). 6. The production of octafluoropropane according to claim 5, wherein the impurity is at least one compound selected from the group consisting of tetrafluoromethane, trifluoromethane, chlorotrifluoromethane, hexafluoroethane and pentafluoroethane. Method. 7. The method for producing octafluoropropane according to claim 5, wherein the step of removing impurities contained in 2H-heptafluoropropane is a distillation step. 8. The chlorine compound contained in 2H-heptafluoropropane is 0.01 vol% or less.
8. The method for producing octafluoropropane according to any one of items 1 to 7. 9. The step (2) is performed in the presence of a diluent gas, wherein the diluent gas is at least one selected from the group consisting of hydrogen fluoride, tetrafluoromethane, hexafluoroethane, and octafluoropropane. The method for producing octafluoropropane according to any one of claims 1 to 8, wherein 10. In the step (2), fluorine gas / 2
The molar ratio of H-heptafluoropropane is 0.9 to 1.5.
The method for producing octafluoropropane according to any one of claims 1 to 9, wherein 11. The process for producing octafluoropropane according to claim 1, wherein in step (2), the concentration of 2H-heptafluoropropane at the inlet of the reactor is 8 mol% or less. 12. The method for producing octafluoropropane according to claim 1, wherein at least a part of the outlet gas in step (2) is circulated and reused as a diluent gas in step (2). 13. The method according to claim 1, further comprising the step of reacting at least a part of the outlet gas of step (2) with a hydrofluorocarbon to remove unreacted fluorine gas in the outlet gas.
13. The method for producing octafluoropropane according to any one of 12. 14. The production of octafluoropropane according to claim 13, wherein the hydrofluorocarbon is at least one compound selected from the group consisting of trifluoromethane, tetrafluoroethane, pentafluoroethane, and 2H-heptafluoropropane. Method. 15. The method according to claim 1, wherein hydrogen fluoride contained in the outlet gas of the step (2) is separated, and the separated hydrogen fluoride is returned to the step (1) and / or the step (2). A process for producing the octafluoropropane described. 16. The method according to claim 1, wherein at least part of octafluoropropane is separated from the gas from which hydrogen fluoride has been separated, and the remaining gas is returned to step (1) and / or step (2).
16. The method for producing octafluoropropane according to any one of items 15 to 15. 17. An octafluoropropane product containing octafluoropropane having a purity of 99.995 vol% or more. 18. The octafluoropropane product according to claim 17, wherein the total amount of the compound containing a chlorine atom in the molecule and the cyclic compound is 50 vol ppm or less. 19. An etching gas comprising the octafluoropropane product according to claim 17 or 18. 20. A cleaning gas comprising the octafluoropropane product according to claim 17 or 18.