JP2002003415A - Method for producing hexafluoroethane and its use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for economically producing FC-116 (hexafluoroethane) by the use of HFC-125 (pentafluoroethane(s)) comprising compound(s) containing in the molecule chlorine atom(s), and to provide uses of the FC-116. SOLUTION: This method comprises the following process: crude HFC-125 comprising compound(s) containing in the molecule chlorine atom(s) is reacted with hydrogen fluoride in the presence of a fluorinating catalyst to convert CFC-115 as the main component in the crude HFC-125 to FC-116 and HFC-125 comprising the FC-116 is then reacted with a fluorine gas in a vapor phase in the presence of a diluent gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for reacting pentafluoroethane containing a compound containing a chlorine atom in a molecule with hydrogen fluoride in the gas phase in the presence of a fluorination catalyst to obtain chlorine in the molecule. A process for fluorinating a compound containing atoms, and a method for producing hexafluoroethane comprising a step of reacting pentafluoroethane containing a fluorinated compound and fluorine gas in the gas phase in the presence of a diluent gas and Regarding its use.

[0002]

2. Description of the Related Art Pentafluoroethane (hereinafter "HFC-
125 "or that" CF ₃ CHF ₂ ". ) Is used, for example, as a low-temperature refrigerant or as a raw material for producing hexafluoroethane (hereinafter referred to as “FC-116” or “CF ₃ CF ₃ ”). As a method for producing HFC-125, the following method is conventionally known.
For example, (1) perchlorethylene (CCl ₂ = CC
l ₂ ) or a method of fluorinating its fluoride with hydrogen fluoride (JP-A-5-97724, JP-A-6-506)
221 and JP-A-7-76534 and JP-A-7-76534
-118182, JP-A No. 8-268932 and JP-Hei 9-511515), (2) chloropentafluoroethane (CClF ₂ CF ₃₎ How hydrogenolysis (Japanese Patent No. 2540409), ( 3) a method of reacting fluorine gas with halogen-containing ethylene (JP-A-1-38034).

[0003] When these methods for producing HFC-125 are used, a compound containing a chlorine atom in a molecule is contained as a main impurity in the target product, HFC-125. As the compound containing a chlorine atom in the molecule, for example, a compound containing one carbon atom in the molecule, chloromethane, chlorodifluoromethane, chlorotrifluoromethane, a compound containing two carbon atoms in the molecule, Examples thereof include chloropentafluoroethane, dichlorotetrafluoroethane, chlorotetrafluoroethane, chlorotrifluoroethane, and chlorotrifluoroethylene which is an unsaturated compound.

When FC-116 is produced by a direct fluorination reaction of reacting HFC-125 with fluorine gas (F ₂ ), the compound containing a chlorine atom in the molecule is contained in HFC-125. In this case, chlorine, hydrogen chloride, chlorine fluoride, or different kinds of chlorofluorocarbons are produced by the reaction with fluorine gas. HFC-125
Hydrofluorocarbons (HFCs) and perfluorocarbons (PFC) that do not contain chlorine atoms in the molecule
Although no particular problem arises even if they are contained, for example, chloromethane (CH ₃ Cl) or chlorodifluoromethane (CHClF ₂ ) reacts with fluorine gas to generate chlorotrifluoromethane (CCIF ₃ ). FC-116 and chlorotrifluoromethane (hereinafter referred to as “CF
C-13 ". ) Forms an azeotropic composition, so that there is a problem that removal of CFC-13 is difficult even when distillation, adsorption purification, or the like is performed. Therefore, when producing FC-116 by reacting HFC-125 with fluorine gas, it is desirable to use HFC-125 containing as little as possible a compound containing a chlorine atom in the molecule.

According to the conventional method for producing HFC-125, the total amount of compounds containing a chlorine atom in a molecule contained in HFC-125 is about 1 vol.
May be included. For this reason, it is conceivable to remove these compounds contained in HFC-125 and repeat the distillation operation in order to increase the purity of HFC-125. However, it is economical to increase the distillation cost and generate distillation loss. In addition, some compounds containing a chlorine atom in the molecule may form an azeotrope or azeotrope-like mixture with HFC-125. is there. In particular, chloropentafluoroethane (hereinafter “CFC-115” or “CCIF ₂
CF ₃ ". ) Is typically several thousand p
pm or more, but HFC-125 and CFC
Since -115 forms an azeotrope, it is difficult to separate it by distillation, which is a general separation and purification technique.

CFC-11 contained in HFC-125
Various methods have been proposed for the method of separating 5. For example, (1) a method of adding a third component to a mixture of HFC-125 and CFC-115 and performing extractive distillation (JP-A-6-510980, JP-A-7-133240, JP-A-7-258123) Gazette, JP-A-8-30
No. 82, JP-A-8-143486, JP-A-1
0-513190), (2) A method of removing CFC-115 contained in HFC-125 using an adsorbent (Japanese Patent Application Laid-Open No. 6-92879, Japanese Patent Application Laid-Open No. 8-50884).
No. 79), (3) CF contained in HFC-125
A method for converting C-115 to HFC-125 in the presence of a hydrogenation catalyst (JP-A-7-509238, JP-A-8-40949, JP-A-8-301801, and JP-A-10-87525) Gazette).

However, the method (1) uses a CFC-
A step of recovering the third component from the mixture of 115 and the third component is required, and the method (2) requires a step of regenerating the adsorbent. Further, the method (3) has a problem that the catalyst life is shortened by the generated hydrogen chloride.

[0008]

SUMMARY OF THE INVENTION The present invention has been made under such a background, and the present invention is to produce FC-116 which is used as an etching gas or a cleaning gas in a semiconductor device manufacturing process. The method comprises the steps of: using a HFC containing a compound containing a chlorine atom in the molecule.
It is an object of the present invention to provide a method for economically producing FC-116 using 125 and a use thereof.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, in a method for producing FC-116, a crude compound containing a compound containing a chlorine atom in a molecule as an impurity. HFC-125 is reacted with hydrogen fluoride in the presence of a fluorination catalyst, and mainly contains CF
The direct fluorination reaction in which C-115 is converted to FC-116 and HFC-125 containing FC-116 and fluorine gas are reacted in the gas phase in the presence of a diluting gas to solve the above-mentioned problem. They have found that they can do this and have completed the present invention. The present invention is a method for producing FC-116 shown in the following [1] to [19] and uses thereof.

[1] A method for producing hexafluoroethane, comprising the following two steps: (1) Pentafluoroethane containing a compound containing a chlorine atom in the molecule is reacted with hydrogen fluoride in the gas phase in the presence of a fluorination catalyst to fluorinate the compound containing a chlorine atom in the molecule. (2) a step of reacting pentafluoroethane containing a fluorinated compound and a fluorine gas obtained in the step (1) in the presence of a diluent gas in the gas phase [2] the intramolecular At least one compound selected from the group consisting of chloromethanetan, chlorotrifluoromethane, chloropentafluoroethane, dichlorotetrafluoroethane, chlorotetrafluoroethane, chlorotrifluoroethane and chlorotrifluoroethylene The method for producing hexafluoroethane according to the above [1], which is a compound of the above [1]. [3] The method for producing hexafluoroethane according to [1] or [2], wherein the total amount of the compound containing a chlorine atom in the molecule contained in pentafluoroethane is 1 vol% or less. [4] The method for producing hexafluoroethane according to [1] or [2], wherein the total amount of the compound containing a chlorine atom in the molecule contained in pentafluoroethane is 0.5 vol% or less. [5] The production of hexafluoroethane according to any one of the above [1] to [4], wherein in the step (1), the fluorination catalyst is a bulk catalyst obtained by adding indium to chromium oxide. Method.

[6] In the above step (1), the reaction temperature for reacting with hydrogen fluoride in the presence of a fluorination catalyst is 1
The method for producing hexafluoroethane according to any one of the above [1] to [5], which is in a range of 50 to 480 ° C. [7] In the step (1), the molar ratio of hydrogen fluoride / organic substance is in the range of 0.5 to 5, [1] to [6].
The method for producing hexafluoroethane according to any one of the above. [8] The method for producing hexafluoroethane according to any one of the above [1] to [7], further comprising a step of removing an acid component containing hydrogen chloride to be formed before the step (2).

[9] Before the step (2), chlorotetrafluoroethane and / or chlorotrifluoroethane are separated, and the separated chlorotetrafluoroethane and / or chlorotrifluoroethane is returned to the step (1). The method for producing hexafluoroethane according to any one of the above [1] to [8], including a step. [10] In the above (1) to (2), the total amount of the compound containing a chlorine atom in the molecule contained in pentafluoroethane is 0.02 vol% or less in the step (2).

The method for producing hexafluoroethane according to any one of [9].

[11] In any one of the above [1] to [10], wherein in the step (2), the fluorinated compound contained in pentafluoroethane contains hexafluoroethane as a main component. 3. The method for producing hexafluoroethane according to item 1. [12] In the step (2), the diluent gas is a gas containing at least one selected from the group consisting of tetrafluoromethane, hexafluoroethane, octafluoropropane, and hydrogen fluoride. [11] The method for producing hexafluoroethane according to any of [11]. [13] The method for producing hexafluoroethane according to any one of the above [1] to [12], wherein in the step (2), the diluent gas is a gas rich in hydrogen fluoride. [14] In the step (2), the reaction temperature between pentafluoroethane containing a fluorinated compound and fluorine gas is in the range of 250 to 500 ° C.
[13] The method for producing hexafluoroethane according to any of [13]. [15] In the above (1) to (2), the reaction temperature between pentafluoroethane containing a fluorinated compound and fluorine gas is in the range of 350 to 450 ° C.
[14] The method for producing hexafluoroethane according to any of [14].

[16] A hexafluoroethane product containing hexafluoroethane having a purity of 99.9997 vol% or more. [17] 1 vol. Of a compound containing a chlorine atom in the molecule
ppm or less, and 1 volp
pm or less, the hexafluoroethane product according to the above [16]. [18] An etching gas comprising the hexafluoroethane product according to [16] or [17]. [19] A cleaning gas containing the hexafluoroethane product according to [16] or [17].

That is, the present invention provides a method for reacting HFC-125 containing a compound containing a chlorine atom in the molecule with hydrogen fluoride in the gas phase in the presence of a fluorination catalyst to obtain a compound containing a chlorine atom in the molecule. Fluorinating the compound to be obtained, and the HFC-containing fluorinated compound obtained in the above step.
Reacting 125 with fluorine gas in the gas phase in the presence of a diluent gas, the method comprising the steps of: "including FC-116 having a purity of 99.9997 vol% or more." FC-116 product "," etching gas characterized by containing said FC-116 product "and" cleaning gas characterized by containing said FC-116 product ". .

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method for producing FC-116 of the present invention and its use will be described in more detail.
As described above, HFC-125 used in the present invention is generally perchlorethylene (CCl ₂ = CC).
l ₂₎ or produced by fluorinating with hydrogen fluoride (HF) and fluorides thereof, a compound containing a chlorine atom derived from the starting material in the HFC-125, chloromethane, chlorodifluoromethane, chloro Examples include trifluoromethane, chloropentafluoroethane, dichlorotetrafluoroethane, chlorotetrafluoroethane, chlorotrifluoroethane, and the like. In order to purify HFC-125 containing these compounds to high purity, a method by a known distillation operation or the like is adopted. However, since the compound and HFC-125 form an azeotropic mixture or an azeotropic mixture, However, separation and purification are extremely difficult, and it is necessary to increase the number of distillation columns and the number of distillation columns, and thus there is a problem in that equipment costs and energy costs are increased, and it is not economical.

The present invention firstly fluorinates a compound containing a chlorine atom in a molecule contained as an impurity in HFC-125 with hydrogen fluoride at an elevated temperature in the presence of a fluorination catalyst. Fluorocarbon (HFC)
Or perfluorocarbon (PFC). For example, CFC- contained as an impurity in HFC-125
115 and chlorotetrafluoroethane (hereinafter referred to as “HCFC
-124 ". ) When fluorinated with hydrogen fluoride, the reaction represented by the following formula (1) or (2) occurs. CF ₃ CCIF ₂ + HF → CF ₃ CF ₃ + HCl (1) CF ₃ CHClF + HF → CF ₃ CHF ₂ + HCl (2) The product is HFC or PFC containing no chlorine atom, and hydrogen chloride is generated as a by-product.

The compounds which are converted into HFC or PFC by the fluorination reaction include the above-mentioned chloromethane, chlorodifluoromethane, chlorotrifluoromethane, chloropentafluoroethane, dichlorotetrafluoroethane, chlorotetrafluoroethane, chlorotrifluoroethane and the like. These compounds are usually contained in HFC-125 in a total amount of several thousand ppm or more. HF containing these compounds
When C-125 is reacted with fluorine gas, a methane-based compound is mainly converted to CFC-13, and an ethane-based compound is converted to CFC-115. Therefore, CFC- is mainly contained in FC-116 obtained after the reaction. 13 and CFC-1
15 is included as an impurity.

CFC-115 hardly reacts with fluorine gas at low temperatures. However, according to the study results of the present inventors, for example, when the reaction temperature is 400 ° C., HFC-12
5 has a concentration of about 800 ppm of CFC-115.
In the following cases, C formed by decomposition of CFC-115
Although the amount of FC-13 is 1 ppm or less, CFC-11
5 exceeds about 2000 ppm, the CFC
-13 is generated at about 2 ppm. CFC-13 is FC-
Since it forms an azeotrope with 116, it is a compound that is difficult to remove by distillation, adsorption purification operation or the like even at a low concentration. Therefore, by reaction with fluorine gas, CFC-
It is preferable that not only the compound producing 13 be removed from the raw material HFC-125, but also that the content of CFC-115 be as low as possible.

The total amount of the compound containing a chlorine atom in the molecule contained in HFC-125 used in the present invention is 1 v
ol% or less, more preferably 0.5 vol%
Or less, more preferably 0.3 vol% or less. The concentration of a compound containing a chlorine atom in the molecule is 1 vo
If the amount exceeds 1%, a reaction at a high temperature is required, and the life of the fluorination catalyst is shortened. At the same time, a side reaction proceeds, and the productivity decreases.

Examples of the fluorination catalyst include chromium,
Known catalysts such as a supported catalyst or a bulk catalyst containing nickel, zinc or the like as a main component may be used, but the catalyst used in the present invention is a bulk catalyst obtained by adding a small amount of indium to chromium oxide. preferable. The reaction temperature in the step of fluorinating a compound containing a chlorine atom in the molecule is 150.
The temperature range is preferably from 480 ° C to 480 ° C.
The reaction temperature is also affected by the concentration of the compound contained in HFC-125, but a preferable temperature can be selected depending on the type. For example, in the case of the reaction of CFC-115 represented by the above formula (1), the temperature is preferably 400 ° C. or more, and in the case of the reaction of HCFC-124 represented by the formula (2), the temperature is preferably 300 ° C. or more.

Further, chlorodifluoromethane (hereinafter referred to as "H
CFC-22 ". ) And hydrogen fluoride,
The reaction represented by the following formula (3) occurs. CHClF ₂ + HF → CHF ₃ + HCl (3) In this reaction, the reaction temperature is preferably 150 ° C. or higher,
A temperature of 400 ° C. or higher is not preferable because the reverse reaction proceeds.

In the step of fluorinating a compound containing a chlorine atom in the molecule, the reaction temperature may vary depending on the type of the compound as described above. Therefore, usually one reactor is sufficient, but it is preferable to use two or more reactors when a plurality of compounds are contained and the respective optimum reaction temperature ranges are different or when the concentration of the compounds is high.

The amount of HF used is expressed as a molar ratio (HF / organic material) to an organic material (raw material gas) containing HFC-125.
The range is preferably from 0.5 to 5, and more preferably from 0.5 to 2. If it is less than 0.5, the reaction hardly proceeds, and if it is more than 5, it is not economical because the reactor becomes large. Further, the reaction pressure in the step of fluorinating a compound containing a chlorine atom in a molecule is preferably in the range of atmospheric pressure to 1.5 MPa, and if it exceeds 1.5 MPa, there is a problem that the pressure resistance of the device is required. It is unfavorable.

The present invention uses the reaction conditions as described above,
The reaction with hydrogen fluoride is performed in the presence of a fluorination catalyst,
The reaction product contains HFC-125, impurities mainly containing HFC and PFC containing no chlorine atom, and hydrogen chloride as a by-product. Here, in the case of HFC-125, as the reaction temperature increases, a side reaction with hydrogen chloride represented by the following formula (4) progresses, and CF ₃ CHF ₂ + HCl → CF ₃ CHClF + HF (4) When 1,1,1,2-tetrafluoroethane (hereinafter, referred to as “HFC-134a”) is included, a side reaction with hydrogen chloride represented by the following formula (5) proceeds. CF ₃ CH ₂ F + HCl → CF ₃ CH ₂ Cl + HF (5) For this reason, after performing the fluorination step (1), it is preferable to remove generated acid components including hydrogen chloride.

The purpose of the acid removal is to remove unreacted hydrogen fluoride (excess hydrogen fluoride) and by-product hydrogen chloride. Hydrogen fluoride has no effect in the direct fluorination reaction step, but hydrogen chloride has an adverse effect such as formation of chlorine-containing compounds and chlorine fluoride as shown in the above formula (4) or (5). It is preferable to remove them because they may affect them. The acid removing step is performed before the next direct fluorination reaction step. As a method for removing the acid, for example, (1) When there is a large amount of unreacted hydrogen fluoride, the effluent containing the acid is removed. Lead to the distillation column, extract hydrogen chloride from the top,
Method of extracting organic matter and hydrogen fluoride from the bottom, (2)
A method in which the generated hydrogen chloride and unreacted hydrogen fluoride are brought into contact with a purifying agent, (3) a method of washing and removing with water or alkaline water, and the like. The acid removal method used in the present invention is not particularly limited. For example, the method (3) can be used. As the alkali, for example, an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution can be used. The absorbed hydrogen fluoride may be collected and reused, and the gas that has passed through the cleaning liquid is dehydrated using a dehydrating agent such as zeolite.

Further, HFC-125 having undergone an acid removing step
The gas containing as a main component may contain, as impurities, HCFC or CFC that has not been completely fluorinated by the reaction with hydrogen fluoride, and is directly distilled before the fluorination reaction step.
It is preferable to remove HCFC and CFC.

Here, HFC-125 and HFC-12
The main compounds that may be included in 5 are shown in Table 1 together with the boiling points.

[Table 1]

The gas containing HFC-125 as a main component is led to a distillation column, where CF ₄ , CHF ₃ , and FC-11 having low boiling points are used.
6. HFC-125 and CFC-115 are withdrawn from the top of the distillation column and HCFC-1 having a higher boiling point than the bottom portion
24 and CF ₃ CH ₂ Cl are extracted. The high-boiling components extracted from the bottom portion are circulated to the reaction with hydrogen fluoride in the step (1). Here, H extracted from the top of the tower
The total amount of the compound containing a chlorine atom in the molecule contained in the distillate containing FC-125 as a main component is 0.02 vol.
1% or less is preferable, and a distillate containing HFC-125 as a main component is used as a raw material for a direct fluorination reaction with fluorine gas.

Next, the step (2) of reacting a gas containing HFC-125 as a main component with a fluorine gas will be described. The step (2) is performed in the presence of a diluting gas,
The gas containing C-125 as a main component is set to a concentration lower than the explosion range. Specifically, the concentration of HFC-125 at the inlet of the reactor is preferably about 6 mol% or less. As the diluent gas, a gas containing at least one selected from the group consisting of tetrafluoromethane, hexafluoroethane, octafluoropropane, and hydrogen fluoride is used, and a diluent gas rich in hydrogen fluoride is preferably used.

The amount of fluorine gas used was HFC-1
Molar ratio to a gas containing 25 as a main component (F ₂ / HFC-1
25) is preferably in the range of 0.5 to 2, and more preferably in the range of 0.9 to 1.3. Reaction temperature is 250-50
It is in the range of 0 ° C, preferably in the range of 350 to 450 ° C. If the temperature is higher than 500 ° C., the desired product FC-116 is cleaved to produce CF _{4, which} is not preferable. When CFC-115 is contained as an impurity, CFC-1
It is not preferable because CFC-13 is generated by cleavage of Fifteen. If the temperature is lower than 250 ° C., the reaction proceeds slowly, which is not preferable.

The method of purifying the gas distilled after the reaction step (2) is not particularly limited. First, the remaining unreacted fluorine gas is removed by, for example, adding trifluoromethane as HFC. . Subsequently, distillation is performed, for example, first, hydrogen fluoride and organic substances are separated. The separated hydrogen fluoride is reused as a diluent gas for the direct fluorination reaction in the step (2), but can also be used as a raw material for the fluorination reaction in the step (1). Here, the composition of the separated organic substance greatly differs depending on the diluent gas used for the reaction. When a gas rich in hydrogen fluoride or the same FC-116 as the target substance is used as the diluent gas, the obtained organic substance is FC- 116 is the main component. When tetrafluoromethane or octafluoropropane is used as the diluent gas, distillation is performed again to purify. In any case, high-purity FC- 116 can be obtained.

The purification of the organic substance by distillation depends on its composition ratio. For example, a low-boiling inert gas or CF ₄ is extracted from the top of the first distillation column, and FC-116 is removed from the bottom part.
Is extracted and introduced into the second distillation column. Next, an inert gas and trifluoromethane having a low boiling point are extracted from the top of the second distillation column, and a gas containing FC-116 as a main component extracted from the bottom portion is supplied to the next third distillation column. Led to high purity FC-11 from the top
Purification is performed by extracting 6. In the third distillation, the gas containing CFC-115 recovered from the bottom portion may be circulated to the step (1) of the reaction with hydrogen fluoride.

The thus purified FC-116 contains almost no impurities and has high purity FC-11.
6 can be obtained. Its purity is 99.9997 vo
1% or more, a compound containing a chlorine atom in a molecule contained as an impurity is 1 volppm or less, and pentafluoroethane is 1 volppm or less. As a method for analyzing FC-116 having a purity of 99.9997 vol% or more, gas chromatography (GC) T
CD method, FID method (including precut method), E
CD method or gas chromatography-mass spectrometer (G
C-MS) or the like.

Next, applications of FC-116 obtained by using the production method of the present invention will be described. High purity FC-
116 can be used as an etching gas in an etching step in a semiconductor device manufacturing process.
Further, it can be used as a cleaning gas in a cleaning step in a semiconductor device manufacturing process. In a process for 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, 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 deposited on an inner wall of the apparatus, a jig, 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 in order to produce a high-quality film.

The etching method using FC-116 is as follows.
It can be performed under various dry etching conditions such as plasma etching and microwave etching. FC-116 and an inert gas such as He, N ₂ , Ar or HCl,
It may be used by mixing with a gas such as O ₂ and H _{2 at} an appropriate ratio.

[0036]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. [Raw material example 1] Tetrachloroethylene (CCl ₂ = CCl ₂ ) and HF were reacted at a reaction pressure of 0.4 M in the presence of a fluorination catalyst.
Pa, a reaction temperature of 300 ° C., and a HF / tetrachloroethylene molar ratio of 4 (first reaction). Further, a reaction pressure of about 0.4 MPa, a reaction temperature of 330 ° C., and an HF / intermediate (CF
_The reaction (second reaction) was performed with a molar ratio of ₃ CHCl ₂ + CF ₃ CHClF) of 4. After the reaction, acid components are removed and distillation is performed by a known method, and the distillate is subjected to gas chromatography.
As a result, the crude HF having the composition shown in Table 2 was obtained.
C-125 (HFC-125 raw material 1) was obtained.

[0037]

[Table 2]

[Raw material example 2] HFC obtained by the above method
-125 Raw material 1 was further subjected to repeated distillation by a known method, and the distillate was analyzed by gas chromatography. As a result, crude HFC-125 (HFC-125) having a composition shown in Table 3 was obtained.
-125 raw material 2) was obtained.

[0039]

[Table 3]

[Catalyst Example 1] 10 L containing 0.6 L of pure water
In a container ( ₂ ), a solution obtained by dissolving 452 g of Cr (NO ₃ ) ₃ .9H ₂ O in 1.2 L of pure water and 0.31 L of 28% aqueous ammonia were stirred while the pH of the reaction solution was 7. 5-
It dripped over about 1 hour, controlling so that it might be in the range of 8.5. The resulting slurry of hydroxide is filtered off,
After washing well with pure water, it was dried at 120 ° C. The obtained solid was pulverized, mixed with graphite, and pelletized by a tableting machine. The pellets are placed at 400 ° C. in a nitrogen stream for 4 hours.
After calcining for a time, a catalyst precursor was obtained. The catalyst precursor is then charged into an Inconel reactor and fluorinated at 350 ° C. under normal pressure under a nitrogen-diluted HF stream, then under a 100% HF stream, and further at 450 ° C. under a nitrogen-diluted HF stream. Treatment (activation of the catalyst) was performed to prepare the catalyst.

[Catalyst Example 2] 10 L containing 0.6 L of pure water
The container, Cr (NO ₃₎ of 452g ₃ · 9H ₂ O and 42
g of In (NO ₃ ) ₃ .nH ₂ O (n is about 5) in pure water 1.
While stirring the solution dissolved in 2 L and 0.31 L of 28% aqueous ammonia, the flow rates of the two aqueous solutions were controlled so that the pH of the reaction solution was in the range of 7.5 to 8.5. The solution was dropped over about 1 hour. The obtained slurry of hydroxide was separated by filtration and washed well with pure water.
For 12 hours. The obtained solid was pulverized, mixed with graphite, and pelletized by a tableting machine. The pellet was fired at 400 ° C. for 4 hours under a nitrogen stream to obtain a catalyst precursor. Filling the catalyst precursor into an Inconel reactor,
A fluorination treatment (activation of the catalyst) was performed in the same manner as in Catalyst Example 1 to prepare a catalyst.

Example 1 150 ml of the catalyst prepared in [Catalyst Example 1] was charged into an Inconel 600 type reactor having an inner diameter of 1 inch and a length of 1 m, and the temperature was increased to 440 ° C. while flowing nitrogen.
And Hydrogen fluoride was supplied at 3.5 NL / hr, and then HFC-125 raw material 1 obtained in [raw material example 1] was used.
It was supplied at 5 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 solution of potassium hydroxide to remove acid components, and the gas composition was analyzed by gas chromatography. As a result, a gas having the composition shown in Table 4 was obtained.

[0043]

[Table 4]

(Example 2) A reaction was carried out under the same conditions and operations as in Example 1 except that 150 ml of the catalyst prepared in [Catalyst Example 2] was charged, and analysis was performed. Table 5 shows the analysis results.

[0045]

[Table 5] As is clear from the analysis results shown in Table 5, when a fluorination catalyst obtained by adding indium to chromium is used, CFC
It can be seen that the conversion of -115 to FC-116 is improved.

(Comparative Example 1) A reaction was performed under the same conditions and operations as in Example 1 except that the reaction temperature was changed to 300 ° C, and analysis was performed. Table 6 shows the results of the analysis.

[0047]

[Table 6] As is clear from the analysis results shown in Table 6, it is found that the conversion rate of CFC-115 is poor when the reaction temperature is low.

Comparative Example 2 A reaction was performed under the same conditions and operation as in Example 1 except that the reaction temperature was changed to 500 ° C., and analysis was performed. Table 7 shows the analysis results.

[0049]

[Table 7] As is clear from the analysis results shown in Table 7, it can be seen that chlorine compounds other than CFC-115, which are considered to be affected by by-product hydrogen chloride, are increasing. In addition, it was found that the catalyst under the high temperature reaction was severely deteriorated.

Example 3 150 ml of the catalyst prepared in [Catalyst Example 2] was charged into an Inconel 600 type reactor having an inner diameter of 1 inch and a length of 2 m, and the temperature was raised to 430 ° C. while flowing nitrogen.
Then, hydrogen fluoride was supplied at 5.0 NL / hr, and then the HFC-125 raw material 2 obtained in [Raw material example 2] was 8.0.
Supplied at NL / hr. The supply of nitrogen gas was stopped, and two hours after the start of the reaction, the exhaust gas was washed with an aqueous potassium hydroxide solution to remove acid components. The gas composition was analyzed by gas chromatography. Obtained.

[0051]

[Table 8]

Example 4 A gas having the composition shown in Table 8 after removal of the acid component was collected by cooling and purified by distillation using a known method. Table 9 shows the result of analyzing the gas obtained after the purification.

[0053]

[Table 9] As is clear from the analysis results shown in Table 9, it can be seen that chlorotetrafluoroethane can be almost completely removed by distillation.

Example 5 A direct fluorination reaction with fluorine gas was carried out using the gas obtained in Example 4 and containing HFC-125 after distillation and purification as a main component. Inner diameter 20.6
mmΦ, 500 mm long Inconel 600 type reactor (electric heater heating: reactor is fluorine gas and temperature 500
C.), and nitrogen gas was supplied at 30 NL / h.
The temperature was set to 420 ° C. while supplying r. Next, 50 NL / hr of hydrogen fluoride and a gas containing HFC-125 as a main component were flowed to one side of the gas stream obtained by branching the diluent gas at 3.5 NL / hr. Thereafter, 3.85 NL / fluorine gas was similarly supplied to the other of the gas streams from which the dilution gas was branched.
hr and the reaction was carried out. After 3 hours, the reaction product gas was washed with an aqueous solution of potassium hydroxide and an aqueous solution of potassium iodide to remove hydrogen fluoride and unreacted fluorine gas.
Next, the composition of the gas was analyzed by gas chromatography. The results of the analysis are shown in Table 10.

[0055]

[Table 10]

Next, the gas after removing the acid content is collected by cooling.
Purification was performed by distillation. The analysis of the purified gas was performed by TCD method, FID method, ECD method and GC-MS method of gas chromatography, and the analysis results are shown in Table 11.

[0057]

[Table 11] As is clear from the analysis results shown in Table 11, the purified F
C-116 contained almost no other impurities, and high-purity FC-116 was obtained, the purity of which was 99.9997.
It turns out that it is more than vol%.

(Comparative Example 3) Inner diameter 20.6 mmΦ, length 5
A 00 mm Inconel 600 type reactor (electric heater heating: the reactor was subjected to a passivation treatment at a temperature of 500 ° C. with fluorine gas) while supplying nitrogen gas at 30 NL / hr,
The temperature was 420 ° C. Next, 50 NL / h of hydrogen fluoride
r, 3.5 NL / h of the HFC-125 raw material 1 obtained in [raw material example 1] was added to one of the gas streams from which the dilution gas was branched.
r flow. Thereafter, 3.85 NL / hr of a fluorine gas was supplied to the other of the gas streams from which the diluent gas was branched, to carry out a reaction. After 3 hours, the reaction product gas was washed with an aqueous solution of potassium hydroxide and an aqueous solution of potassium iodide to remove hydrogen fluoride and unreacted fluorine gas. Next, the composition of the gas was analyzed by gas chromatography. The results of the analysis are shown in Table 12.

[0059]

[Table 12] As is clear from the analysis results shown in Table 12, HFC- containing a compound containing a chlorine atom in the molecule as an impurity was used.
It can be seen that when 125 reacts with fluorine gas, CFC-13 chlorotrifluoromethane, which is a hardly separable substance, is generated.

Next, the gas having the composition shown in Table 12 after the removal of the acid component was collected by cooling and purified by distillation. Table 13 shows the results of analyzing the gas obtained after the purification.

[0061]

[Table 13] As is clear from the analysis results shown in Table 13, CFC-1
It can be seen that 3 is a compound that is difficult to separate.

[0062]

As described above, high-purity FC-116 can be produced using HFC-125 containing a compound containing a chlorine atom in the molecule. The high-purity FC-116 can be used as an etching gas or a cleaning gas in a semiconductor device manufacturing process.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Toshio Oi 5-1 Ogimachi, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Showa Denko K.K. BD52 BD60 BE01 BE53 4H039 CA51 CD20 5F004 AA15 BB13 BB14 CA01 DA00 DA22 DA23 DA24 DA25 DA26 DA29

Claims (19)

[Claims] 1. A method for producing hexafluoroethane, comprising the following two steps. (1) Pentafluoroethane containing a compound containing a chlorine atom in the molecule is reacted with hydrogen fluoride in the gas phase in the presence of a fluorination catalyst to fluorinate the compound containing a chlorine atom in the molecule. (2) a step of reacting pentafluoroethane containing a fluorinated compound and a fluorine gas obtained in the step (1) in the gas phase in the presence of a diluting gas; 2. The compound containing a chlorine atom in the molecule is selected from chloromethanetan, chlorotrifluoromethane, chloropentafluoroethane, dichlorotetrafluoroethane, chlorotetrafluoroethane, chlorotrifluoroethane and chlorotrifluoroethylene. The method for producing hexafluoroethane according to claim 1, wherein the method is at least one compound selected from the group consisting of: 3. The method for producing hexafluoroethane according to claim 1, wherein the total amount of the compound containing a chlorine atom in the molecule contained in pentafluoroethane is 1 vol% or less. 4. The total amount of a compound containing a chlorine atom in a molecule contained in pentafluoroethane is 0.5 vol.
% Or less, the method for producing hexafluoroethane according to claim 1 or 2. 5. The method for producing hexafluoroethane according to claim 1, wherein in the step (1), the fluorination catalyst is a bulk catalyst obtained by adding indium to chromium oxide. . 6. In the step (1), the reaction temperature for reacting with hydrogen fluoride in the presence of a fluorination catalyst is 150.
The method for producing hexafluoroethane according to any one of claims 1 to 5, wherein the temperature is in the range of from 480C to 480C. 7. The method according to claim 1, wherein in the step (1), a molar ratio of hydrogen fluoride / organic substance is in a range of 0.5 to 5.
7. The method for producing hexafluoroethane according to any one of 6. 8. The method for producing hexafluoroethane according to claim 1, further comprising, before the step (2), a step of removing an acid component containing generated hydrogen chloride. 9. Prior to the step (2), chlorotetrafluoroethane and / or chlorotrifluoroethane is separated, and the separated chlorotetrafluoroethane and / or chlorotrifluoroethane is subjected to the step (1). The method for producing hexafluoroethane according to any one of claims 1 to 8, further comprising a step of returning to the above. 10. The method according to claim 1, wherein in the step (2), the total amount of the compound containing a chlorine atom in the molecule contained in pentafluoroethane is 0.02 vol% or less.
10. The method for producing hexafluoroethane according to any one of claims 9 to 9. 11. The method according to claim 1, wherein in the step (2), the fluorinated compound contained in pentafluoroethane contains hexafluoroethane as a main component.
11. The method for producing hexafluoroethane according to any one of items 10 to 10. 12. The method according to claim 1, wherein in the step (2), the diluent gas is a gas containing at least one selected from the group consisting of tetrafluoromethane, hexafluoroethane, octafluoropropane, and hydrogen fluoride. 11
The method for producing hexafluoroethane according to any one of the above. 13. The method for producing hexafluoroethane according to claim 1, wherein in the step (2), the diluting gas is a gas rich in hydrogen fluoride. 14. The method according to claim 1, wherein in the step (2), the reaction temperature between pentafluoroethane containing a fluorinated compound and fluorine gas is in the range of 250 to 500 ° C. For producing hexafluoroethane. 15. The method according to claim 1, wherein in the step (2), a reaction temperature between pentafluoroethane containing a fluorinated compound and fluorine gas is in a range of 350 to 450 ° C. For producing hexafluoroethane. 16. A hexafluoroethane product comprising hexafluoroethane having a purity of 99.9997 vol% or more. 17. The compound containing a chlorine atom in the molecule is 1 volppm or less, and pentafluoroethane is 1 volppm or less.
The hexafluoroethane product according to claim 16, which is not more than volppm. 18. An etching gas comprising the hexafluoroethane product according to claim 16 or 17. 19. A cleaning gas containing the hexafluoroethane product according to claim 16 or 17.