JPH10297910A - Purification method of sulfur hexafluoride - Google Patents

Abstract

(57) [Problem] To provide a method for purifying sulfur hexafluoride which easily and efficiently removes harmful impurities from sulfur hexafluoride containing impurities. SOLUTION: A purifying agent comprising a carbonaceous solid comprising sulfur hexafluoride containing impurities, at least one compound selected from the group consisting of an alkaline earth metal compound, an alkali metal aluminate salt and a tetraalkylammonium salt. Contact.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying sulfur hexafluoride, and more particularly to a method for purifying sulfur hexafluoride gas containing harmful impurities by contacting the gas with a purifying agent.

[0002]

BACKGROUND OF THE INVENTION sulfur hexafluoride (hereinafter referred to as "SF _6")
Because of its excellent electrical insulation properties as a gas, its demand is increasing as a gas-insulating medium for circuit breakers and transformers. SF ₆ itself is chemically stable and neither toxic nor corrosive.However, when it is used in, for example, equipment of reduced-type substation equipment, it can be subjected to strong electrical stress such as corona discharge and arcs generated during interruption. Being exposed and decomposed to produce various impurities and cause obstacles. For example, among impurities generated by decomposition due to electric stress, sulfur tetrafluoride (hereinafter referred to as “SF ₄ ”), sulfur difluoride (hereinafter referred to as “SF ₂ ”), and sulfur monofluoride (hereinafter referred to as “SF ₂ ”) "S ₂
F ₂ ) is a very reactive substance,
When a small amount of water exists in the apparatus, it reacts with the water and reacts with hydrogen fluoride (hereinafter referred to as “HF”), sulfur dioxide (hereinafter referred to as “S”).
O ₂ ), thionyl fluoride (hereinafter “SOF ₂ ”), sulfuryl fluoride (hereinafter “SO ₂ F ₂ ”)
Or a very small amount of sulfur pentafluoride (hereinafter referred to as “S ₂ F
₁₀ "). SF ₆ containing these impurities
If the gas continues to be used, an obstacle such as corrosion of a metal member of the equipment will appear. Therefore, the gas is appropriately extracted from the equipment and replaced with a new SF ₆ .

However SF ₆ gas is not only expensive, in situations where not negligible impact on the environment such as global warming, SF ₆ containing the harmful impurities, can be recycled after purification process to recover Has been required. Various purification methods have been proposed to address this problem. For example, as a dry method, a method in which a recovered gas is contacted with activated alumina and X-type synthetic zeolite (Japanese Patent Publication No. 47-6205), an impurity gas component is converted into a solid compound and a product gas using a converting agent. Then, a method of absorbing and removing the produced gas using a gas absorbent (Japanese Patent Application Laid-Open No. 60-54723), and a wet method in which the recovered gas is treated in an alkaline bath (aqueous calcium hydroxide solution). (Hamano, et al .: SF ₆ gas recovery device at high power test station; 1996 National Conference of the Institute of Electrical Engineers of Japan), a method of contacting with a lithium-substituted polymer having a large network structure (Japanese Patent Application Laid-Open No. 6-212506), and the like. .

[0004]

However, there has been a problem in each of the above-mentioned purification methods proposed so far. For example, in the above method, SO ₂ , SOF ₂ , SO ₂ F ₂ ,
Sufficient adsorption effect cannot be obtained for S ₂ F ₁₀ etc.
Is a method in which impurities are reacted with calcium hydroxide to generate hydrogen, and this hydrogen gas is adsorbed and removed. However, there is a problem that flammable hydrogen gas is generated, and sufficient processing capacity cannot be obtained. The method is a wet method and requires large-scale equipment.In addition to the use of expensive absorbents, the wet method involves a large amount of water and other problems. Was not a typical way. The present invention has been made in order to solve the above-described problems, and accordingly, has as its object to provide a method for purifying SF ₆ that can easily and efficiently remove harmful impurities from SF ₆ containing impurities. Is to do.

[0005]

Means for Solving the Problems The present invention to solve the aforementioned problem, is chosen the SF ₆ containing impurities, alkaline earth metal compounds, alkali metal aluminate salt, and the group consisting of tetraalkylammonium salts Contacting with a purifying agent comprising one or more compounds and a carbonaceous solid
₆ purification methods are provided. SF containing the above impurities
₆ is HF, SO ₂ , S ₂ F ₂ , SF ₂ , S
It may include any one or more of the group consisting of F ₄ , S ₂ F ₁₀ , SOF ₂ and SO ₂ F ₂ . The alkaline earth metal compound of the refining agent is preferably selected from the group consisting of oxides, hydroxides, carbonates and nitrates of calcium, magnesium, barium and strontium. Further, the alkali metal aluminate is preferably selected from the group consisting of lithium aluminate, sodium aluminate, potassium aluminate and cesium aluminate. The tetraalkylammonium salt is selected from the group consisting of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetramethylammonium carbonate, tetraethylammonium carbonate, tetramethylammonium chloride, tetraethylammonium chloride, tetramethylammonium aluminate and tetraethylammonium aluminate. Preferably, it is selected. The carbonaceous solid of the refining agent is selected from the group consisting of coke powder, charcoal, coal, pitch, charcoal, activated carbon and carbon black.
Preferably, it is at least one species. The specific surface area of the refining agent is preferably in the range of 80m ² / g~1000m ² / g. Further, the average pore size of the purifying agent is preferably in the range of 7 Å to 1500 Å. The concentration of HF contained in the purified SF ₆ is preferably 0.1 ppm by weight or less. Further, it is preferable that the above-mentioned method for purifying SF ₆ further includes a dehydration step. This dehydration step
It is preferable to use zeolite as a dehydrating agent. The concentration of water contained in the purified SF ₆ is preferably 50 ppm by weight or less.

[0006]

Embodiments of the present invention will be described below. The method for purifying SF _{6 according to} the present invention is applied to gas insulating equipment such as a gas circuit breaker (GCB), for example, and SF ₆ (hereinafter referred to as “SF _6”) which is decomposed by corona discharge or an electric arc generated at the time of interruption to generate harmful impurities. This harmful impurity is removed from "impure SF ₆ ") and applied to a purification process such as recycling. Impurity SF ₆ after being used in these gas insulated devices is generally SF ₄ , SF ₂ , S
Contains ₂ F _2, SO _2, corrosive harmful impurities such as _{SOF 2, SO 2 F 2,} S 2 F 10.

In one embodiment of the purification method of the present invention, a purifying agent comprising an alkaline earth metal compound, an alkali metal aluminate and / or a tetraalkylammonium salt and a carbonaceous solid is charged into, for example, a reaction tube. The impure SF ₆ is allowed to flow as a gas stream through the reaction tube at room temperature. As a result, impurities in the impure SF ₆ are adsorbed by the purifying agent, and SF ₆ containing substantially no harmful impurities (hereinafter referred to as “purified SF ₆ ”) can be simply and effectively recovered.

[0008] In the purification SF ₆ obtained recycled like the gas insulated apparatus, it is preferable that moisture in the refining SF ₆ is less 50 weight ppm. This can be achieved by, for example, adding a dehydration step using zeolite as a dehydrating agent to the above-mentioned SF ₆ purification step.

Hereinafter, the components of the present invention will be described in detail. The refining agent used in the present invention comprises at least one compound selected from the group consisting of an alkaline earth metal compound, an alkali metal aluminate salt and a tetraalkylammonium salt, and a carbonaceous solid.

Examples of the alkaline earth metal compounds include oxides, hydroxides, carbonates and nitrates of calcium, magnesium, barium or strontium. These may be used alone or as a mixture of two or more. Among them, calcium oxides, hydroxides, carbonates and nitrates are preferred, and quick lime, slaked lime or limestone is more preferred in that it is available at low cost and is easy to handle.

Examples of the alkali metal aluminate include lithium aluminate, sodium aluminate, potassium aluminate and cesium aluminate. These may be used alone,
Alternatively, they may be used as a mixture of two or more. Above all, sodium aluminate or potassium aluminate is preferred in view of availability. Particularly, sodium aluminate is preferred.

Examples of the above tetraalkylammonium salts include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetramethylammonium carbonate, tetraethylammonium carbonate, tetramethylammonium chloride, tetraethylammonium chloride, tetramethylammonium aluminate or aluminate And tetraethylammonium acid. These may be used alone or as a mixture of two or more. Among them, tetramethylammonium hydroxide, tetramethylammonium carbonate, tetramethylammonium chloride or tetramethylammonium aluminate is preferred in terms of availability. Particularly, tetramethylammonium carbonate is preferred. Tetramethylammonium carbonate and tetramethylammonium aluminate can be respectively produced by reacting tetramethylammonium hydroxide with carbon dioxide gas or aluminum hydroxide.

Examples of the carbonaceous solid include coke powder, charcoal, coal, pitch, charcoal, activated carbon and carbon black. These are 1
The species may be used alone or as a mixture of two or more. The carbonaceous solid is preferably in the form of powder, fine particles, or pellets. In the case of fine particles, they may be spherical or crushed. These carbonaceous solids have a specific surface area of 100 m ^2.
/ G~2500m within the range of ² / g, especially 500m ² / g
It is preferably in the range of ２０００2000 m ² / g. Particularly preferred examples of carbonaceous solids include charcoal in powdered form and activated carbon in finely divided form.

The purifying agent used in the present invention can be prepared by various methods. For example, if activated carbon or the like as a carbonaceous solid is immersed in an aqueous solution of sodium aluminate or the like, and then dried after stirring, a supported purifying agent is obtained. Also, for example, a mixture of slaked lime powder and charcoal powder and the like at a predetermined ratio, kneading by adding water, forming into a pellet having a particle size that is easy to handle, and then drying, a pellet-type refining agent can be obtained. .

When the purifying agent is of a supported type, for example, the amount of the alkali metal aluminate and / or the tetraalkylammonium salt supported on the carbonaceous solid is, when activated carbon is used as the carbonaceous solid, the supported amount g per 100 ml of activated carbon. In the range of 1 weight / vol% to 30 weight / vol%, especially 5
Weight / volume% to 20 weight / volume%. If the amount is less than 1 weight / volume%, the effect is insufficient.
If the content exceeds%, the pores of the carbonaceous solid are blocked and the efficiency is reduced.

When the refining agent is in the form of a pellet, for example, the mixing ratio of the alkaline earth metal compound and the carbonaceous solid depends on the type of the composition, but may be the same weight ratio or a large ratio of the alkaline earth metal compound. Is preferred. It is necessary to sufficiently dry the purifying agent, whether it is a carrier type or a pellet type, and it is preferable to use an inert gas such as nitrogen, helium, or argon as a drying gas for drying.

The specific surface area of the purifying agent is from 80 m ² / g to 10 m ² / g.
Within the range of 00m ² / g, especially 100m ² / g~700m
It is preferably within the range of ² / g. The average pore size of the purifying agent is preferably in the range of 7 Å to 1500 Å, particularly preferably in the range of 7 Å to 1100 Å. Outside these ranges, the purification efficiency is reduced. The specific surface area and the average pore diameter in the above ranges can be realized by selecting a material, a mixing ratio, a preparation method, and the like when preparing a purifying agent.

When purifying impure SF ₆ using the above-mentioned purifying agent, the impure SF ₆ is brought into contact with this purifying agent.
In this contacting step, the impurity concentration in the impure SF ₆ is preferably 2.0% by weight or less. If the impurities are contained more than this, a large amount of the purification agent is required, and the purification time is long, which is not preferable.

At the time of contact, the impure SF ₆ may be a gas or a liquid, but it is usually preferable to contact it as a gas. As a contact method, any method generally used for fluid-solid contact can be adopted. Accordingly, a fluidized bed system or a moving bed system can be used, but a fixed bed system is generally preferred. When the gas-solid contact method is employed, the pressure in the contact step is not particularly limited, but is preferably in the range of atmospheric pressure to 2 MPa from an economic viewpoint.
The temperature of the contacting step is not particularly limited.
It can be appropriately selected within the range of 0 ° C to 100 ° C.
Unless there are special circumstances, it is preferable to set the contact temperature to normal temperature from an economic viewpoint.

By the above-described step of contacting with a purifying agent, impure SF ₆ can be converted to, for example, 0.1 wt.
pm or less (halogen ion analysis, ion chromatography). Under these purification conditions, the amount of S ions is 0.1 ppm by weight or less (ion chromatography) as SO ₄ ⁻ . Furthermore, other harmful impurities such as SO ₂ , SF ₂ , SF ₄ , SO ₂ F ₂ and S
OF ₂ may also be the detection limit or less in a gas chromatography (GC) and gas chromatography / mass spectrometry (GC / MAS) and (0.1 wt ppm or less).

In order to recycle the purified SF ₆ obtained in the contact step as a gaseous insulating medium, it is necessary to sufficiently remove water which is a factor of SF ₆ decomposition. Therefore, it is preferable to add a dehydration step capable of strictly controlling the water content to the method for purifying SF ₆ of the present invention. This dehydration step is preferably performed by gas-solid contact using a synthetic zeolite or the like as a dehydrating agent after the contacting step. A suitable dehydrating agent for use in this step is a synthetic zeolite, especially from molecular sieves commonly known as "molecular sieves (trade name)"
It is preferable to select and use those having a suitable fine particle size range.

In the gas-solid contact dehydration step using the molecular sieve as a dehydrating agent, it is economical to operate at a pressure in the range of atmospheric pressure to 2 MPa, a temperature in the range of -40 ° C to 100 ° C, and particularly at room temperature. Preferred from a standpoint. By this dehydration step, the water content in the purified SF ₆ is reduced to 50 wt.
m or less, and more preferably 10 ppm by weight or less, which is a particularly preferable moisture content limit.

[0023]

The present invention will be described in more detail with reference to the following examples. Impure SF ₆ sample : The following impure SF ₆ sample was prepared for testing.

(Impurity SF ₆ sample 1) Sulfur hexafluoride (manufactured by Showa Denko KK, purity: 99.999% or more, halogen ion 1)
Weight ppm or less) to the gas insulation
After filling up to the filling pressure of MPa and repeating the gas insulation opening / closing test, this gas was collected in a vacuum-dried and cooled cylinder container to obtain impure SF ₆ sample 1. The analysis results of this sample are shown below. The analysis method was an electron capture type analysis method (G
C / ECD), flame photometry (GC / FPD), thermal conductivity (GC / TCD), gas chromatography / mass spectrometry (GC / MAS), halogen ion analysis (ion chromatography) and moisture The analysis method (crystal oscillator method) was used. The analysis results were expressed in ppm by weight of the gas components excluding water, and H ₂ O was separately expressed in ppm by weight. (Hereinafter, all the analysis results are shown in the same manner.) Component analysis value (unit is ppm by weight); SF ₆ 9.8430 CF ₄ 0.0620 C ₂ F ₆ 0.0063 C ₂ F ₄ 0.0012 SOF ₂ 0.0512 SO ₂ F ₂ 0.0022 SO ₂ 0.0013 HF 0.0328 H ₂ O 0.0086

(Impurity SF ₆ sample 2) To the above impure SF ₆ sample 1, commercially available sulfur tetrafluoride (SF ₄ ) and sulfur pentafluoride (S ₂ F ₁₀ ) were further added, and the impure SF ₆ sample 2 did. The analysis results of this sample are shown below. The analysis method of S ₂ F ₁₀ was based on an electron capture analysis (GC / ECD). Component analysis value (unit is ppm by weight); SF ₆ 9.8422 CF ₄ 0.0620 C ₂ F ₆ 0.0063 C ₂ F ₄ 0.0012 SOF ₂ 0.0512 SO ₂ F ₂ 0.0022 SO ₂ 0. [0013] SF ₄ 0.0005 S ₂ F ₁₀ 0.0003 HF 0.0328 H ₂ O 0.0118

Preparation of Purifying Agent : The following three types of purifying agents were prepared. (Purifying agent 1) 25% aqueous solution of sodium aluminate 40
100 ml of granular activated carbon (specific surface area: 1200 m ² / g, particle size: 0.5 mm to ² mm) was immersed in the mixture, stirred, dried with dry nitrogen gas at 200 ° C. for 3 hours, and supported with water-free sodium aluminate. Activated carbon (NaAlO ₂ carrying amount 10 g / 100 ml activated carbon) was prepared and used as Purifying Agent 1. Purifying agent 1 had a specific surface area of about 570 m ² / g and an average pore diameter of about 14 Å.

(Purifying agent ² ) 100 m of granular activated carbon (specific surface area: 1200 m ² / g, particle size: 0.5 mm to ² mm) is added to 40 ml of a 25% aqueous solution of tetramethylammonium hydroxide.
After immersion, stirring and drying at 50 ° C. for 5 hours with dry nitrogen gas, tetramethylammonium-supported activated carbon ((CH ₃ ) ₄ NOH supported water-free amount 10 g / 100 ml)
(Activated carbon) was prepared and used as a purification agent 2. Purifying agent 2 had a specific surface area of about 560 m ² / g and an average pore diameter of about 13 Å.

(Purifying agent 3) Charcoal having a particle size of 250 μm or less and slaked lime having a particle size of 250 μm or less are blended at a weight ratio of 1: 3, and water is added thereto while mixing with a Henschel mixer, and the mixture is granulated. After drying at 4 ° C. for 4 hours, heat treatment was performed at 800 ° C. for 8 hours in a nitrogen atmosphere, and dehydration and firing were performed. The obtained fired product was sized into pellets of 2 mm to 4 mm to prepare a purifying agent 3. Purifying agent 3 is mainly composed of carbon (C) and calcium oxide (CaO), and has a specific surface area of about 120 m.
² / g and an average pore diameter of about 1000 Å.

Purification Experiment : (Example 1) A SUS cylinder having a capacity of 75 ml was filled with 40 ml of the above-mentioned purifying agent 1 and the above impure SF was added thereto.
₆ Sample 1 was supplied at room temperature at a rate of 12 NL / hr.
Gas was collected at the outlet of the cylinder, and gas analysis and halogen ion analysis were performed. In the halogen ion analysis, an outlet gas was blown into ultrapure water for a certain period of time, and the sample was analyzed by ion chromatography. The analysis results are shown below. Component analysis (unit weight ppm, - below measurement _{limit); SF 6 99.9467 CF 4 0.0482} C 2 F 6 0.0051 C 2 F 4 - SOF 2 - SO 2 F 2 - SO 2 - HF ^{_{- F - <0.001 SO 4 -}} 0.004 from H ₂ O 0.0129 the above results, the purification agent 1, impure SF ₆ sample 1
It is clear that the harmful impurities in it have been effectively removed.

(Example 2) A SUS cylinder having a capacity of 75 ml was filled with 40 ml of the above-mentioned purifying agent 2, and the impure SF ₆ sample 1 was supplied thereto at room temperature at a rate of 20 NL / hr. Gas was collected at the outlet of the cylinder, and gas analysis and halogen ion analysis were performed in the same manner as in Example 1. The analysis results are shown below. Component analysis (unit weight ppm, - below measurement _{limit); SF 6 99.9415 CF 4 0.0528} C 2 F 6 0.0057 C 2 F 4 - SOF 2 - SO 2 F 2 - SO 2 - HF ^- F - <0.01 SO ₄ - from 0.01 H ₂ O to about 150 above results, the purification agent 1, impure SF ₆ sample 1
It is clear that the harmful impurities in it have been effectively removed.

Example 3 An experiment was conducted to remove water from the outlet gas obtained in Example 2. SU with a capacity of 75 ml
An S cylinder was filled with 60 ml of a commercially available synthetic zeolite (Molecular sieve 3A manufactured by Union Showa), and the outlet gas obtained in Example 2 was introduced into the cylinder to analyze the moisture in the exhaust gas. The analysis value was 5 ppm by weight or less. It is clear that the water in the SF ₆ sample was effectively removed to below a predetermined limit by the method of Example 3.

Example 4 Two SUS cylinders each having a capacity of 75 ml were connected in series, the first cylinder was filled with 40 ml of the purifying agent 3, and the second cylinder was charged with the purifying agent 1
Was filled, and impure SF ₆ sample 1 was supplied from the first cylinder at room temperature at a rate of 20 NL / hr. Gas was collected at the outlet of the second cylinder, and gas analysis and halogen ion analysis were performed in the same manner as in Example 1. The analysis results are shown below. Component analysis (unit weight ppm, - below measurement _{limit); SF 6 99.9579 CF 4 0.0389} C 2 F 6 0.0032 C 2 F 4 - SOF 2 - SO 2 F 2 - SO 2 - HF ^{_{- F - <0.001 SO 4 -}} 0.002 from H ₂ O 0.005 the above results, the combination purifier 3 and purification agent 1 is effective in removing harmful impurities impure SF ₆ in a sample 1 Not only perfluorocarbons (CF ₄ , C ₂ F ₆ )
It can be seen that the method is also effective in removing slag.

Example 5 A SUS cylinder having a capacity of 75 ml was filled with 40 ml of the purifying agent 1 described above, and the impure SF ₆ sample 2 was supplied thereto at room temperature at a rate of 12 NL / hr. Gas was collected at the outlet of the cylinder, and gas analysis and halogen ion analysis were performed in the same manner as in Example 1. The analysis method of S ₂ F ₁₀ is electron capture type analysis (GC /
ECD). The analysis results are shown below. Component analysis (unit weight ppm, - below measurement _{limit); SF 6 99.8423 CF 4 0.0472} C 2 F 6 0.0050 C 2 F 4 - SOF 2 - SO 2 F 2 - SO 2 - SF _{4 - S 2 F 10 <0.0001} HF - F - <0.001 SO 4 - 0.003 from H ₂ O 0.0124 the above results, the purification agent 1, impure SF ₆ sample 2
It is clear that the SF ₄ and S ₂ F ₁₀ therein were effectively removed as well as other harmful impurities.

[0034]

According to the method for purifying sulfur hexafluoride of the present invention, sulfur hexafluoride containing impurities is converted into an alkaline earth metal compound,
Since it is to be brought into contact with a refining agent comprising one or more compounds selected from an alkali metal aluminate salt or a tetraalkylammonium salt and a carbonaceous solid, a large-scale facility is not required, and it is simple and effective. Harmful impurities can be removed. Further, in the purification method of the present invention, by adding a dehydration step, water which is a factor of SF ₆ decomposition can be removed, and the purified SF ₆ can be recycled as a gas insulating medium.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiroki Ohno 5-1 Ogimachi, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Showa Denko KK Chemical Research Laboratory (72) Inventor Tetsuo Nakajo 5-1 Ogimachi, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture (72) Inventor Toshio Oi 5-1 Ogimachi, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture In-house Kawasaki Plant (72) Inventor Kuniomi Marumo 5- Ogimachi, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture 1 Showa Denko KK Chemical Research Laboratory

Claims (12)

[Claims] 1. A method comprising the steps of: removing sulfur hexafluoride containing impurities from a carbonaceous solid comprising at least one compound selected from the group consisting of an alkaline earth metal compound, an alkali metal aluminate salt and a tetraalkylammonium salt; A method for purifying sulfur hexafluoride to be brought into contact with a preparation. 2. Hydrogen fluoride, sulfur dioxide gas as impurities,
The sulfur hexafluoride comprising at least one of the group consisting of sulfur monofluoride, sulfur difluoride, sulfur tetrafluoride, sulfur pentafluoride, thionyl fluoride and sulfuryl fluoride, according to claim 1, A method for purifying sulfur hexafluoride in contact with a purifying agent. 3. The hexafluoride according to claim 1, wherein the alkaline earth metal compound is selected from the group consisting of oxides, hydroxides, carbonates and nitrates of calcium, magnesium, barium and strontium. A method for purifying sulfur. 4. The method for purifying sulfur hexafluoride according to claim 1, wherein the alkali metal aluminate is selected from the group consisting of lithium aluminate, sodium aluminate, potassium aluminate and cesium aluminate. . 5. The method of claim 1, wherein the tetraalkylammonium salt is tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetramethylammonium carbonate, tetraethylammonium carbonate, tetramethylammonium chloride,
The method for purifying sulfur hexafluoride according to claim 1, wherein the method is selected from the group consisting of tetraethylammonium chloride, tetramethylammonium aluminate, and tetraethylammonium aluminate. 6. The carbonaceous solid is coke powder, charcoal,
The method for purifying sulfur hexafluoride according to claim 1, wherein the method is at least one selected from the group consisting of coal, pitch, charcoal, activated carbon, and carbon black. 7. The purification agent has a specific surface area of 80 m ² / g to 10 m ² / g.
Method for purifying sulfur hexafluoride according to claim 1 is in the range of 00m ² / g. 8. The refining agent of claim 1, wherein the average pore size is in the range of 7 Å to 1500 Å.
The method for purifying sulfur hexafluoride according to the above. 9. The method for purifying sulfur hexafluoride according to claim 1, wherein the concentration of hydrogen fluoride contained in the purified sulfur hexafluoride is 0.1 ppm by weight or less. 10. The method for purifying sulfur hexafluoride according to claim 1, further comprising a dehydration step. 11. The method for purifying sulfur hexafluoride according to claim 9, wherein the dehydrating step uses zeolite as a dehydrating agent. 12. The method for purifying sulfur hexafluoride according to claim 10, wherein the concentration of water contained in the purified sulfur hexafluoride is 50 ppm by weight or less.