Catalyst composition for decomposing sulfur hexafluoride and method for decomposing sulfur hexafluoride

Abstract

To provide a catalyst composition and a method for decomposing sulfur hexafluoride which can easily and inexpensively decompose sulfur hexafluoride without requiring a special device and can greatly reduce the running cost and environmental load of the decomposition process.SOLUTION: A catalyst composition for decomposing sulfur hexafluoride comprises a 9-fluorenol derivative, a base and a solvent.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a catalyst composition for decomposing sulfur hexafluoride and a method for decomposing sulfur hexafluoride. [Background technology]

[0002] Sulfur hexafluoride (SF6) gas has excellent insulating properties and is flame-retardant, and is used industrially in gas circuit breakers and other applications, as well as in medical settings as a retention gas during retinal detachment surgery, due to its high specific gravity and non-toxicity to the human body. However, its greenhouse effect is about 22,800 times that of carbon dioxide, and its life span in the atmosphere is very long, so its emissions are strictly regulated. Used sulfur hexafluoride (SF6) gas is basically recovered, refined, and then reused, or decomposed using high-temperature treatment or plasma, which consumes a large amount of energy. Similarly, there are known examples of decomposition by ultraviolet irradiation using several catalysts, but it requires continuous irradiation of high-energy ultraviolet rays and is considered to have low decomposition efficiency.

[0003] For example, Patent Document 1 describes a method for decomposing SF6 gas in which SF6 gas or a gas containing SF6 gas is heated and decomposed by inductively coupled thermal plasma. The thermal plasma has a high temperature of about 10,000 K, and is highly capable as a heating source, and is said to be capable of decomposing SF6 gas stably at a high processing speed for a long period of time.

[0004] In addition, examples have been reported in which the physical energy required for decomposition is replaced by the chemical energy possessed by organic compounds or organometallic compounds. Patent Document 2 describes a method for decomposing sulfur hexafluoride by reacting sulfur hexafluoride with an organic alkali metal compound. According to this method, sulfur hexafluoride can be decomposed in a safe manner under mild conditions.

[0005] On the other hand, in Non-Patent Document 1, the present inventors have reported an example of generating organic radicals from nitroalkanes using 9-fluorenol as a catalyst. 9-fluorenol is easy to handle and may be used as an organic one-electron reducing agent. However, there was no suggestion of decomposing sulfur hexafluoride. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2001-300298 A [Patent Document 2] JP 2010-13342 A [Non-patent literature]

[0007] [Non-Patent Document 1] Kashihara, M. et al., Synlett 2023, 34, 1482-1486 Summary of the Invention [Problem to be solved by the invention]

[0008] The high-temperature decomposition process of Patent Document 1, which uses inductively coupled thermal plasma, requires a large amount of energy, which causes problems in terms of decomposition cost, safety, etc. Furthermore, in the decomposition method of Patent Document 2, which uses an organic alkali metal compound, not only is the preparation of the reactant very costly, but special preparations such as blocking air and moisture may also be required to handle the compound, so further improvements were required.

[0009] As a result of investigations conducted in light of the current situation, the inventors discovered that sulfur hexafluoride can be decomposed easily and inexpensively using a catalyst composition containing a 9-fluorenol derivative, a base and a solvent, and thus completed the present invention.

[0010] The present invention has been made to solve the above-mentioned problems, and aims to provide a catalyst composition and a method for decomposing sulfur hexafluoride that can decompose sulfur hexafluoride easily, inexpensively, and safely without the need for special equipment, and that can significantly reduce the running costs and environmental load of the decomposition process. [Means for solving the problem]

[0011] The above problem is solved by providing a catalytic composition for decomposing sulfur hexafluoride, the catalytic composition comprising a 9-fluorenol derivative, a base and a solvent.

[0012] In this case, it is a preferred embodiment that the 9-fluorenol derivative is an alcohol derivative represented by the following formula (1) or a ketone derivative represented by the following formula (2).

[0013] [ka]

[0014] [ka] [In formulas (1) and (2), R 1 ~R 8 are each independently a hydrogen atom, an alkyl group, a vinyl group, an alkynyl group, an aryl group, an alkoxy group, an aryloxy group, an amino group, a nitro group, a sulfanyl group, a sulfinyl group, a sulfonyl group, a heteroaromatic ring group, a perfluoroalkyl group, a carbonyl group, or a halogen atom; R 1 and R 2 , R 2 and R 3 , R 3 and R 4 , R 5 and R 6 , R 6 and R 7 , or R 7 and R 8 may form a ring structure.]

[0015] The solvent is preferably an alcohol-based solvent.

[0016] The above-mentioned problem is also solved by providing a method for decomposing sulfur hexafluoride, which comprises contacting sulfur hexafluoride with a catalyst composition containing a 9-fluorenol derivative, a base, and a solvent, and reacting the sulfur hexafluoride at 25 to 140°C.

[0017] In a preferred embodiment, the reaction further comprises a step of monitoring the reaction status, and the monitoring step is a method of adding an aqueous lead acetate solution to the reaction solution to confirm the formation of a black precipitate and / or a method of quantifying fluoride ions from the reaction solution.

[0018] In another preferred embodiment, the 9-fluorenol derivative consisting of an alcohol derivative represented by the following formula (1) is used as an organic one-electron reducing agent to reductively decompose sulfur hexafluoride, and the ketone derivative consisting of the following formula (2) generated after electron transfer is regenerated by alcohol into the 9-fluorenol derivative consisting of the alcohol derivative represented by the following formula (1).

[0019] [ka]

[0020] [ka] [In formulas (1) and (2), R 1 ~R 8 are each independently a hydrogen atom, an alkyl group, a vinyl group, an alkynyl group, an aryl group, an alkoxy group, an aryloxy group, an amino group, a nitro group, a sulfanyl group, a sulfinyl group, a sulfonyl group, a heteroaromatic ring group, a perfluoroalkyl group, a carbonyl group, or a halogen atom; R 1 and R 2 , R 2 and R 3 , R 3 and R 4 , R 5 and R6 , R 6 and R 7 , or R 7 and R 8 may form a ring structure.] Effect of the Invention

[0021] The catalyst composition of the present invention can decompose sulfur hexafluoride safely, easily and inexpensively without the need for special equipment. The 9-fluorenol derivative contained in the catalyst composition of the present invention can be used repeatedly as a stable catalyst, so that the running costs and environmental load of the decomposition process can be significantly reduced. In addition, since it can be handled stably in the atmosphere and the entire device does not need to be large-scale, it can be made compact and portable, reducing the transportation effort and cost that have been required for the recovery of sulfur hexafluoride up to now, and realizing on-site decomposition processing. [Brief description of the drawings]

[0022] [Figure 1] A schematic diagram of the assumed reaction mechanism for the decomposition cycle of sulfur hexafluoride when 9-fluorenol is used as a one-electron reducing agent is shown. SET (Single Electron Transfer) stands for single electron transfer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The catalyst composition of the present invention is a catalyst composition for decomposing sulfur hexafluoride, and is characterized by comprising a 9-fluorenol derivative, a base and a solvent.

[0024] As will be seen from the examples described later, in Comparative Example 1, in which no 9-fluorenol derivative was used, no fluoride ions were detected from the reaction solution, and the decomposition reaction of sulfur hexafluoride did not proceed. In addition, in Comparative Example 2, in which no base was used, no fluoride ions were detected from the reaction solution, and the decomposition reaction of sulfur hexafluoride did not proceed. In contrast, the present inventors have found through their studies that by using a catalyst composition containing a 9-fluorenol derivative, a base, and a solvent, fluoride ions are detected from the reaction solution, and elemental sulfur is generated as a decomposition product of sulfur hexafluoride. Thus, the significance of the present invention is great because sulfur hexafluoride can be decomposed easily, inexpensively, and safely.

[0025] The 9-fluorenol derivative used in the present invention includes an alcohol derivative represented by 9-fluorenol and a ketone derivative represented by fluorenone. These alcohol derivatives and ketone derivatives may have a substituent. In addition, since a ketone derivative represented by fluorenone is regenerated into an alcohol derivative represented by 9-fluorenol in a reaction system for decomposing sulfur hexafluoride, the ketone derivative may be used, or the alcohol derivative may be used. Specifically, a preferred embodiment is an alcohol derivative represented by the following formula (1) or a ketone derivative represented by the following formula (2).

[0026] [ka]

[0027] [ka] [In formulas (1) and (2), R 1 ~R 8 are each independently a hydrogen atom, an alkyl group, a vinyl group, an alkynyl group, an aryl group, an alkoxy group, an aryloxy group, an amino group, a nitro group, a sulfanyl group, a sulfinyl group, a sulfonyl group, a heteroaromatic ring group, a perfluoroalkyl group, a carbonyl group, or a halogen atom; R 1 and R2 , R 2 and R 3 , R 3 and R 4 , R 5 and R 6 , R 6 and R 7 , or R 7 and R 8 may form a ring structure.]

[0028] In the above formulas (1) and (2), R 1 ~R 8 are each independently a hydrogen atom, an alkyl group, a vinyl group, an alkynyl group, an aryl group, an alkoxy group, an aryloxy group, an amino group, a nitro group, a sulfanyl group, a sulfinyl group, a sulfonyl group, a heteroaromatic ring group, a perfluoroalkyl group, a carbonyl group, or a halogen atom; R 1 and R 2 , R 2 and R 3 , R 3 and R 4 , R 5 and R 6 , R 6 and R 7 , or R 7 and R 8 may form a ring structure.

[0029] R 1 ~R 8The alkyl group used in may be a straight-chain or branched-chain alkyl group, or a cyclic cycloalkyl group. Examples of the alkyl group include straight-chain or branched-chain alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, n-hexyl, isohexyl, 2-ethylhexyl, n-heptyl, n-octyl, 2-butyloctyl, n-nonyl, and n-decyl; and cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptanyl, cyclooctanyl, cyclononanyl, and cyclodecanyl. Among them, alkyl groups having 1 to 12 carbon atoms are preferred, alkyl groups having 1 to 10 carbon atoms are more preferred, and alkyl groups having 1 to 8 carbon atoms are even more preferred.

[0030] The alkyl group may have other substituents, and examples of such other substituents include aryl groups such as a phenyl group and a naphthyl group; heteroaromatic groups such as a pyridyl group, a thienyl group, a furyl group, a pyrrolyl group, an imidazolyl group, a pyrazinyl group, an oxazolyl group, a thiazolyl group, a pyrazolyl group, a benzothiazolyl group, and a benzimidazolyl group; methoxy groups, ethoxy groups, propoxy groups, isopropoxy groups, butoxy groups, isobutoxy groups, sec-butoxy groups, tert-butoxy groups, pentyloxy groups, alkoxy groups such as an isopentyloxy group, a neopentyloxy group, a hexyloxy group, a cyclohexyloxy group, a heptyloxy group, an octyloxy group, a nonyloxy group, a decyloxy group, or a dodecyloxy group; alkylthio groups such as a methylthio group, an ethylthio group, a propylthio group, or a butylthio group; arylthio groups such as a phenylthio group or a naphthylthio group; tri-substituted silyloxy groups such as a tert-butyldimethylsilyloxy group or a tert-butyldiphenylsilyloxy group; an acetoxy group, Acyloxy groups such as a propanoyloxy group, a butanoyloxy group, a pivaloyloxy group, and a benzoyloxy group; alkoxycarbonyl groups such as a methoxycarbonyl group, an ethoxycarbonyl group, a propoxycarbonyl group, an isopropoxycarbonyl group, a butoxycarbonyl group, an isobutoxycarbonyl group, a sec-butoxycarbonyl group, a tert-butoxycarbonyl group, a pentyloxycarbonyl group, a hexyloxycarbonyl group, a heptyloxycarbonyl group, and an octyloxycarbonyl group; alkylsulfinyl groups such as methylsulfinyl group and ethylsulfinyl group; arylsulfinyl groups such as phenylsulfinyl group; sulfonic acid ester groups such as methylsulfonyloxy group, ethylsulfonyloxy group, phenylsulfonyloxy group, methoxysulfonyl group, ethoxysulfonyl group, phenyloxysulfonyl group; amino group; hydroxyl group; cyano group; nitro group; halogen atoms such as fluorine atom, chlorine atom, bromine atom, iodine atom, and the like.

[0031] R 1 ~R 8The alkynyl group used in may be linear or branched, and examples thereof include ethynyl, propynyl, propargyl, butynyl, pentynyl, hexynyl, and phenylethynyl groups. Among these, alkynyl groups having 2 to 10 carbon atoms are preferred, and alkynyl groups having 2 to 8 carbon atoms are more preferred. These alkynyl groups may have other substituents, and examples of such other substituents include the same as those exemplified in the description of the alkyl group.

[0032] R 1 ~R 8 Examples of the aryl group used in the formula (1) include a phenyl group, a naphthyl group, an anthryl group, and a phenanthryl group. Among them, an aryl group having 6 to 14 carbon atoms is preferable, and an aryl group having 6 to 10 carbon atoms is more preferable. These aryl groups may have other substituents, and as such other substituents, the same ones as those exemplified in the explanation of the alkyl group can be used.

[0033] R 1 ~R 8 Examples of the alkoxy group used in include a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, an n-pentyloxy group, an isopentyloxy group, a neopentyloxy group, an n-hexyloxy group, an isohexyloxy group, a 2-ethylhexyloxy group, an n-heptyloxy group, an n-octyloxy group, an n-nonyloxy group, and an n-decyloxy group. Among them, an alkoxy group having 1 to 10 carbon atoms is preferred, an alkoxy group having 1 to 8 carbon atoms is more preferred, and an alkoxy group having 1 to 6 carbon atoms is even more preferred. These alkoxy groups may have other substituents, and as such other substituents, the same ones as those exemplified in the explanation of the alkyl group can be used.

[0034] R 1 ~R 8Examples of the aryloxy group used in the above include a phenoxy group, a naphthyloxy group, an anthryloxy group, and a phenanthryloxy group. Among them, an aryloxy group having 6 to 14 carbon atoms is preferable, and an aryloxy group having 6 to 10 carbon atoms is more preferable. These aryloxy groups may have other substituents, and as such other substituents, the same ones as those exemplified in the explanation of the alkyl group can be used.

[0035] R 1 ~R 8 The amino group used in may be a primary amino group (-NH2), a secondary amino group, or a tertiary amino group. A secondary amino group is -NHR 9 (R 9 is an arbitrary monovalent substituent, and R 9 Examples of the secondary amino group include an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an acetyl group, a benzoyl group, a benzenesulfonyl group, a tert-butoxycarbonyl group, etc. Specific examples of the secondary amino group include a methylamino group, an ethylamino group, a propylamino group, an isopropylamino group, etc. 9 R is an alkyl group, such as a secondary amino group, a phenylamino group, or a naphthylamino group. 9 and a secondary amino group in which R is an aryl group. 9 The hydrogen atom of the alkyl group or aryl group in may be further substituted with an acetyl group, a benzoyl group, a benzenesulfonyl group, a tert-butoxycarbonyl group, etc. The tertiary amino group is -NR 9 R 10 (R 9 and R 10 is any monovalent substituent), and R 10 As for R 9 can be used, and R 9 and R 10 may be the same or different. Specific examples of the tertiary amino group include a dimethylamino group, a diethylamino group, a dibutylamino group, an ethylmethylamino group, a diphenylamino group, and a methylphenylamino group.9 and R 10 is at least one selected from the group consisting of an alkyl group and an aryl group.

[0036] R 1 ~R 8 Examples of the sulfanyl group used in the above include alkylthio groups such as methylthio, ethylthio, propylthio, and butylthio groups; and arylthio groups such as phenylthio, naphthylthio, anthrylthio, and phenanthrylthio groups. Among these, alkylthio groups having 1 to 12 carbon atoms and / or arylthio groups having 6 to 14 carbon atoms are preferred, and alkylthio groups having 1 to 10 carbon atoms and / or arylthio groups having 6 to 10 carbon atoms are more preferred. These sulfanyl groups may have other substituents, and as such other substituents, the same ones as those exemplified in the explanation of the alkyl group can be used.

[0037] R 1 ~R 8 Examples of the sulfinyl group used in include alkylsulfinyl groups such as methylsulfinyl group, ethylsulfinyl group, propylsulfinyl group, and butylsulfinyl group; and arylsulfinyl groups such as phenylsulfinyl group, naphthylsulfinyl group, anthrylsulfinyl group, and phenanthrylsulfinyl group. Among them, alkylsulfinyl groups having 1 to 12 carbon atoms and / or arylsulfinyl groups having 6 to 14 carbon atoms are preferred, and alkylsulfinyl groups having 1 to 10 carbon atoms and / or arylsulfinyl groups having 6 to 10 carbon atoms are more preferred. These sulfinyl groups may have other substituents, and as such other substituents, the same ones as those exemplified in the explanation of the alkyl group can be used.

[0038] R 1 ~R 8Examples of the sulfonyl group used in the formula include alkylsulfonyl groups such as methylsulfonyl group, ethylsulfonyl group, propylsulfonyl group, and butylsulfonyl group; and arylsulfonyl groups such as phenylsulfonyl group, naphthylsulfonyl group, anthrylsulfonyl group, and phenanthrylsulfonyl group. Among them, alkylsulfonyl groups having 1 to 12 carbon atoms and / or arylsulfonyl groups having 6 to 14 carbon atoms are preferred, and alkylsulfonyl groups having 1 to 10 carbon atoms and / or arylsulfonyl groups having 6 to 10 carbon atoms are more preferred. These sulfonyl groups may have other substituents, and as such other substituents, the same ones as those exemplified in the explanation of the alkyl group can be used.

[0039] R 1 ~R 8 Examples of the heteroaromatic ring group used in include a pyridyl group, a furyl group, a thienyl group, a pyrrolyl group, an imidazolyl group, a pyrazinyl group, an oxazolyl group, a thiazolyl group, a pyrazolyl group, a benzothiazolyl group, a benzoimidazolyl group, etc. These heteroaromatic ring groups may have other substituents, and as such other substituents, the same ones as those exemplified in the explanation of the alkyl group can be used.

[0040] R 1 ~R 8 The perfluoroalkyl group used in may be linear or branched, and examples thereof include a trifluoromethyl group, a pentafluoroethyl group, a heptafluoropropyl group, a nonafluorobutyl group, and an undecafluoropentyl group. Among them, a perfluoroalkyl group having 1 to 8 carbon atoms is preferable, and a perfluoroalkyl group having 1 to 6 carbon atoms is more preferable. These perfluoroalkyl groups may have other substituents, and as such other substituents, the same ones as those exemplified in the explanation of the alkyl group can be used.

[0041] R 1 ~R 8Examples of the carbonyl group used in the formula include alkylcarbonyl groups such as acetyl, propionyl, butyryl, and isobutyryl; arylcarbonyl groups such as benzoyl; alkylcarbonyloxy groups such as acetyloxy, propionyloxy, butyryloxy, and isobutyryloxy; alkoxycarbonyl groups such as methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, isopropoxycarbonyl, butoxycarbonyl, and isobutoxycarbonyl; and alkoxycarbonyloxy groups such as methoxycarbonyloxy, ethoxycarbonyloxy, propoxycarbonyloxy, isopropoxycarbonyloxy, butoxycarbonyloxy, and isobutoxycarbonyloxy. These carbonyl groups may have other substituents, and as such other substituents, the same ones as those exemplified in the explanation of the alkyl group can be used.

[0042] R 1 ~R 8 Examples of the halogen atom used include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc. Among them, at least one selected from the group consisting of a fluorine atom and a chlorine atom is preferably used.

[0043] In the above formulas (1) and (2), R 1 and R 2 , R 2 and R 3 , R 3 and R 4 , R 5 and R 6 , R 6 and R 7 , or R 7 and R 8 may form a ring structure. The ring structure is preferably an aromatic ring which may have a substituent. The aromatic ring is preferably a benzene ring or a naphthalene ring, and more preferably a benzene ring.

[0044] In the catalyst composition of the present invention, the content of the 9-fluorenol derivative is not particularly limited, but it is preferable that the 9-fluorenol derivative is contained in 0.05 to 50 mmol per 5 mL of the solvent contained in the catalyst composition of the present invention. If the content of the 9-fluorenol derivative is less than 0.05 mmol, the decomposition of sulfur hexafluoride may be insufficient, so it is more preferable that the content is 0.1 mmol or more, and even more preferable that the content is 0.5 mmol or more. On the other hand, if the content of the 9-fluorenol derivative exceeds 50 mmol, the cost may be high and the 9-fluorenol derivative may not dissolve in the solvent, so it is more preferable that the content is 30 mmol or less, even more preferable that the content is 20 mmol or less, and particularly preferable that the content is 10 mmol or less.

[0045] The base used in the present invention is not particularly limited as long as it can abstract a proton. For example, it may be an inorganic base such as carbonates such as cesium carbonate (Cs2CO3), sodium carbonate (Na2CO3), potassium carbonate (K2CO3), lithium carbonate (Li2CO3), sodium hydrogen carbonate (NaHCO3), potassium hydrogen carbonate (KHCO3), etc.; phosphates such as potassium phosphate and sodium phosphate; alkoxides such as sodium methoxide, potassium methoxide, sodium ethoxide, potassium isopropyl oxide, etc.; hydroxides such as sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, etc.; or triethylamine, N,N-diisopropylethylamine, 1,1,3,3-tetramethylglucose, etc. The base may be an organic base such as an amine base such as anidine (TMG), 1,8-diazabicyclo[5.4.0]-7-undecene (DBU), 1,5-diazabicyclo[4.3.0]-5-nonene (DBN), 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD), 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), 1,8-bis(dimethylamino)naphthalene (DMAN), 1,4-diazabicyclo[2.2.2]octane (DABCO), etc.; a pyridine base such as pyridine, 2,6-dimethylpyridine, N,N-dimethyl-4-aminopyridine (DMAP), etc. Among them, the base is preferably at least one selected from the group consisting of carbonates, phosphates, and hydroxides, and more preferably a carbonate. Among the carbonates, cesium carbonate (Cs2CO3) is preferably used.

[0046] In the catalyst composition of the present invention, the molar ratio of the 9-fluorenol derivative to the base (base / 9-fluorenol derivative) is preferably 1 to 50, more preferably 1.2 to 30, and even more preferably 1.5 to 20, from the viewpoint that the 9-fluorenol derivative acts as a catalyst and the base serves as the overall electron source in the reductive decomposition of SF.

[0047] Examples of the solvent used in the present invention include water; alcohol-based solvents such as methanol, ethanol, 1-propanol, 2-propanol, and 1-butanol; aliphatic hydrocarbon-based solvents such as n-pentane and n-hexane; aromatic hydrocarbon-based solvents such as benzene, toluene, and xylene; ether-based solvents such as dimethyl ether, ethyl methyl ether, diethyl ether, 1,4-dioxane, and tetrahydrofuran; halogen-based solvents such as chloroform, chlorobenzene, o-dichlorobenzene, m-dichlorobenzene, dichloromethane, 1,2-dichloroethane, and 1,1-dichloroethane; aprotic polar solvents such as dimethyl sulfoxide, N,N-dimethylformamide, and N-methylpyrrolidone; ester-based solvents such as ethyl acetate and butyl acetate; ketone-based solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; carbonate-based solvents such as dimethyl carbonate, diethyl carbonate, ethylene carbonate, and propylene carbonate; and nitrile-based solvents such as acetonitrile, propionitrile, and benzonitrile. These solvents can be used alone or in combination of two or more. Among them, at least one selected from the group consisting of water, alcohol-based solvents, aliphatic hydrocarbon-based solvents, aromatic hydrocarbon-based solvents, ether-based solvents, halogen-based solvents, and aprotic polar solvents is preferably used. In order to regenerate a ketone derivative represented by fluorenone into an alcohol derivative represented by 9-fluorenol in a reaction system for decomposing sulfur hexafluoride and function as a catalyst, the solvent is preferably an alcohol-based solvent, and more preferably at least one selected from the group consisting of methanol, ethanol, and isopropyl alcohol. The alcohol-based solvent may contain other solvents such as water within a range that does not impair the effects of the present invention. The content of the other solvent is preferably 100 parts by mass or less, more preferably 50 parts by mass or less, relative to 100 parts by mass of the alcohol-based solvent.

[0048] In the catalyst composition of the present invention, the content of the solvent is not particularly limited, but the catalyst composition of the present invention preferably contains 50 to 95 parts by mass of the solvent, more preferably contains 60 to 92 parts by mass, and even more preferably contains 70 to 90 parts by mass, relative to 100 parts by mass of the total amount of the catalyst composition of the present invention.

[0049] The method for decomposing sulfur hexafluoride using the catalyst composition of the present invention is not particularly limited. A method is preferably adopted in which a catalyst composition containing a 9-fluorenol derivative, a base, and a solvent is contacted with sulfur hexafluoride and reacted at 25 to 140°C. Thus, unlike high-temperature treatment using plasma that consumes a large amount of energy, the decomposition method of the present invention can decompose sulfur hexafluoride easily and safely without requiring special equipment and at low cost, and can significantly reduce the running cost and environmental load of the decomposition process.

[0050] If the temperature during the reaction is less than 25° C., the decomposition reaction of sulfur hexafluoride may not proceed, and therefore the temperature is preferably 40° C. or higher, more preferably 60° C. or higher, and even more preferably 80° C. or higher. On the other hand, if the temperature during the reaction exceeds 140° C., there is a risk of promoting deactivation of the 9-fluorenol derivative, and therefore the temperature is preferably 130° C. or lower, more preferably 120° C. or lower, and even more preferably 110° C. or lower.

[0051] The pressure (absolute pressure) during the reaction is not particularly limited. The reaction may be carried out under atmospheric pressure or at a pressure higher than atmospheric pressure. From the viewpoint of efficiently advancing the decomposition reaction of sulfur hexafluoride, it is preferable to carry out the reaction at a pressure higher than atmospheric pressure, and the pressure is preferably 1.2 atm or higher, more preferably 1.5 atm or higher, and even more preferably 2 atm or higher. On the other hand, the pressure is preferably 10 atm or lower, and more preferably 5 atm or lower.

[0052] The time for the reaction is not particularly limited, and is preferably 0.5 to 50 hours. If the time for the reaction is less than 0.5 hours, the decomposition reaction of sulfur hexafluoride may not proceed, so the time is more preferably 1 hour or more, and even more preferably 1.5 hours or more. On the other hand, the time for the reaction is more preferably 40 hours or less, even more preferably 30 hours or less, and particularly preferably 20 hours or less.

[0053] A preferred embodiment of the present invention includes a step of monitoring the reaction status in the reaction, and the monitoring step is a method of confirming the generation of a black precipitate by adding an aqueous lead acetate solution to the reaction solution, and / or a method of quantifying fluoride ions from the reaction solution. The monitoring step allows the progress of the decomposition reaction of sulfur hexafluoride to be confirmed. Therefore, a preferred embodiment also includes a step of appropriately terminating the reaction depending on the progress. The monitoring step is not particularly limited as long as it is a method that can confirm the decomposition product of sulfur hexafluoride, but as is clear from the examples described below, it is possible to confirm that elemental sulfur is generated as a decomposition product of sulfur hexafluoride, so a method of adding an aqueous lead acetate solution to the reaction solution to confirm the generation of a black precipitate is preferably adopted. In addition, it is possible to confirm that fluoride ions derived from fluorine constituting sulfur hexafluoride are generated, so a method of quantifying fluoride ions from the reaction solution is also preferably adopted. From the viewpoint of efficiently monitoring whether sulfur hexafluoride is decomposed, a more preferred embodiment is a method of quantifying fluoride ions from the reaction solution.

[0054] The decomposition method of the present invention is characterized in that sulfur hexafluoride is reductively decomposed using the 9-fluorenol derivative as an organic one-electron reducing agent. Although the present invention is not limited to a specific theory, FIG. 1 shows a schematic diagram of the assumed reaction mechanism of the decomposition cycle of sulfur hexafluoride when fluorenol is used as a one-electron reducing agent. A proton is extracted from an alcohol derivative represented by 9-fluorenol by the base to generate an anion, which is a catalytically active species, and sulfur hexafluoride can be reductively decomposed by electron transfer to sulfur hexafluoride. At this time, the alcohol derivative represented by 9-fluorenol is oxidized and converted to a ketone derivative represented by fluorenone, but it can be easily regenerated to an alcohol derivative represented by 9-fluorenol in the reaction system. Therefore, it can be seen that the decomposition reaction of sulfur hexafluoride proceeds catalytically. That is, a preferred embodiment of the present invention is a method in which the 9-fluorenol derivative consisting of the alcohol derivative represented by the above formula (1) is used as an organic one-electron reducing agent to reductively decompose sulfur hexafluoride, and the ketone derivative represented by the above formula (2) generated after electron transfer is regenerated by alcohol into the 9-fluorenol derivative consisting of the alcohol derivative represented by the above formula (1).

[0055] The decomposition method of the present invention is not limited to a batch process, and the decomposition reaction can be continuously performed by a flow process. Examples of the flow process include a system in which sulfur hexafluoride and the solvent are introduced into a reaction tube filled with a catalyst containing the 9-fluorenol derivative and the base represented by an inorganic base, and the decomposition product or solution is recovered at the outlet, and a system in which sulfur hexafluoride, the solvent, and the base represented by an organic base are introduced into a reaction tube filled with a catalyst containing the 9-fluorenol derivative, and the decomposition product or solution is recovered at the outlet. EXAMPLES

[0056] The present invention will now be described in more detail with reference to examples.

[0057] Example 1 Under nitrogen, a stir bar, 180 mg (1 mmol) of 9-fluorenol, 489 mg (1.5 mmol) of cesium carbonate (Cs2CO3), and 5 mL of 2-propanol were added to a 20 mL test tube. The test tube was placed in an on-head pressure vessel, sealed, and connected to a sulfur hexafluoride gas cylinder to pressurize the entire vessel to 4 atmospheres. This was heated and stirred at 100°C for 18 hours. The reaction solution was then cooled to room temperature, the solvent was distilled off under reduced pressure, and 4-fluorophenol was added as an internal standard substance. Analysis by 19F NMR using heavy water revealed that 2.1 mmol of fluoride ions were detected. On the other hand, after a similar reaction, an aqueous solution of lead(II) acetate was added and the mixture was heated and stirred at 60°C for 20 minutes. This produced a black precipitate believed to be lead sulfide, indicating that elemental sulfur had been produced as a decomposition product of sulfur hexafluoride. The results are summarized in Table 1.

[0058] Example 2 The mixture was heated and stirred at 100°C for 18 hours in the same manner as in Example 1, except that 1.5 mmol of tripotassium phosphate (K3PO4) was used instead of cesium carbonate. When analyzed by 19F NMR in the same manner as in Example 1, only a very small amount of fluoride ions was detected. The obtained results are summarized in Table 1.

[0059] Example 3 The mixture was heated and stirred at 100°C for 18 hours in the same manner as in Example 1, except that 1.5 mmol of potassium carbonate (K2CO3) was used instead of cesium carbonate. When analyzed by 19F NMR in the same manner as in Example 1, 0.033 mmol of fluoride ions were detected. The obtained results are summarized in Table 1.

[0060] Example 4 The mixture was heated and stirred at 100°C for 18 hours in the same manner as in Example 1, except that 1.5 mmol of sodium carbonate (Na2CO3) was used instead of cesium carbonate. When analyzed by 19F NMR in the same manner as in Example 1, only a very small amount of fluoride ions was detected. The obtained results are summarized in Table 1.

[0061] Example 5 The reaction mixture was heated and stirred at 100° C. for 18 hours in the same manner as in Example 1, except that 5 mL of 1,4-dioxane was used instead of 2-propanol. When analyzed by 19F NMR in the same manner as in Example 1, 1.2 mmol of fluoride ions were detected. The results are summarized in Table 1.

[0062] Example 6 Instead of heating and stirring at 100° C. for 18 hours in Example 1, the mixture was heated and stirred at 100° C. for 3 hours. When analyzed by 19F NMR in the same manner as in Example 1, 1.8 mmol of fluoride ions were detected. The results are summarized in Table 1.

[0063] Example 7 In Example 1, the mixture was stirred at room temperature (25° C.) for 6 hours instead of heating and stirring at 100° C. for 18 hours. When analyzed by 19F NMR in the same manner as in Example 1, 1.4 mmol of fluoride ions were detected. The results are summarized in Table 1.

[0064] Example 8 In Example 1, the mixture was heated and stirred at 120° C. for 6 hours instead of 100° C. for 18 hours. When analyzed by 19F NMR in the same manner as in Example 1, 2.1 mmol of fluoride ions were detected. The results are summarized in Table 1.

[0065] Example 9 The procedure of Example 1 was repeated except that 1 mmol of 2,7-dimethoxy-9-fluorenol was used instead of 9-fluorenol, and the mixture was heated and stirred at 100° C. for 18 hours. Analysis by 19F NMR in the same manner as in Example 1 detected 1.7 mmol of fluoride ions. The results are summarized in Table 1.

[0066] Example 10 The mixture was heated and stirred at 100° C. for 6 hours in the same manner as in Example 1, except that the total pressure was changed from 4 atm to 5 atm. When analyzed by 19F NMR in the same manner as in Example 1, 2.7 mmol of fluoride ions were detected. The obtained results are summarized in Table 1.

[0067] Example 11 A stirring bar, 180 mg (1 mmol) of 9-fluorenol, and 489 mg (1.5 mmol) of cesium carbonate (Cs2CO3) were added to a 20 mL Schlenk flask. The Schlenk flask was sealed and degassed using a vacuum pump, and then replaced with SF6 gas at 1 atm. 5 mL of 2-propanol was added. This was heated and stirred at 100°C for 6 hours. Analysis by 19F NMR in the same manner as in Example 1 detected 2.0 mmol of fluoride ions. The results are summarized in Table 1.

[0068] Comparative Example 1 The reaction mixture was heated and stirred at 100° C. for 18 hours in the same manner as in Example 1, except that 9-fluorenol was not used. Analysis by 19F NMR in the same manner as in Example 1 revealed that the amount of fluoride ions was 0 mmol. The results are summarized in Table 1.

[0069] Comparative Example 2 The mixture was heated and stirred at 100° C. for 18 hours in the same manner as in Example 1, except that cesium carbonate was not used. When analyzed by 19F NMR in the same manner as in Example 1, the amount of fluoride ions was 0 mmol. The obtained results are summarized in Table 1.

[0070] [Table 1]

Claims

1. A catalytic composition for decomposing sulfur hexafluoride, comprising: A catalyst composition comprising a 9-fluorenol derivative, a base and a solvent.

2. The catalyst composition according to claim 1, wherein the 9-fluorenol derivative is an alcohol derivative represented by the following formula (1) or a ketone derivative represented by the following formula (2): 【Chemistry 1】 【Chemistry 2】 [In formulas (1) and (2), R １ ~R ８ are each independently a hydrogen atom, an alkyl group, a vinyl group, an alkynyl group, an aryl group, an alkoxy group, an aryloxy group, an amino group, a nitro group, a sulfanyl group, a sulfinyl group, a sulfonyl group, a heteroaromatic ring group, a perfluoroalkyl group, a carbonyl group, or a halogen atom; R １ and R ２ , R ２ and R ３ , R ３ and R ４ , R ５ and R ６ , R ６ and R ７ , or R ７ and R ８ may form a ring structure.

3. 3. The catalyst composition according to claim 1, wherein the solvent is an alcohol-based solvent.

4. A method for decomposing sulfur hexafluoride, comprising the steps of: A method for decomposing sulfur hexafluoride, comprising contacting a catalyst composition containing a 9-fluorenol derivative, a base and a solvent with sulfur hexafluoride and reacting the catalyst composition at 25 to 140°C.

5. 5. The method for decomposing sulfur hexafluoride according to claim 4, further comprising a step of monitoring the reaction status during the reaction, the monitoring step being a method of confirming the formation of a black precipitate by adding an aqueous lead acetate solution to the reaction solution and / or a method of quantifying fluoride ions from the reaction solution.

6. The method for decomposing sulfur hexafluoride according to claim 4 or 5, characterized in that sulfur hexafluoride is reductively decomposed using the 9-fluorenol derivative consisting of an alcohol derivative represented by the following formula (1) as an organic one-electron reducing agent, and a ketone derivative represented by the following formula (2) generated after electron transfer is regenerated by an alcohol into the 9-fluorenol derivative consisting of the alcohol derivative represented by the following formula (1). 【Chemistry 3】 【Chemistry 4】 [In formulas (1) and (2), R １ ~R ８ are each independently a hydrogen atom, an alkyl group, a vinyl group, an alkynyl group, an aryl group, an alkoxy group, an aryloxy group, an amino group, a nitro group, a sulfanyl group, a sulfinyl group, a sulfonyl group, a heteroaromatic ring group, a perfluoroalkyl group, a carbonyl group, or a halogen atom; R １ and R ２ , R ２ and R ３ , R ３ and R ４ , R ５ and R ６ , R ６ and R ７ , or R ７ and R ８ may form a ring structure.

Images