Method for removing silicon tetrafluoride, method for regenerating specific metal salt, removal cycle method, and method for producing high-purity organic fluorine compound

Abstract

Provided is a removal method in which a mixture containing silicon tetrafluoride and at least one organic fluorine compound selected from the group consisting of fluorocarbons and fluoroolefins is brought into contact with at least one metal salt selected from the group consisting of metal fluorides, alkali metal hydroxides, alkali metal carbonates, and alkali metal hydrogen carbonates, and at least a portion of the silicon tetrafluoride is removed from the mixture.

Description

Method for removing silicon tetrafluoride, method for regenerating specific metal salt, removal cycle method, and method for producing high-purity organofluorine compound

[0001] The present disclosure relates to a method for removing silicon tetrafluoride, a method for regenerating a specific metal salt, a removal cycle method, and a method for producing a high-purity organofluorine compound.

[0002] Fluorocarbons and fluoroolefins are produced using hydrogen fluoride (HF). The raw material of HF is fluorite, and it is known that SiF ４ is by-produced when a silicon component is mixed into the fluorite (see, for example, Non-Patent Document 1). When at least one organofluorine compound selected from the group consisting of fluorocarbons and fluoroolefins is synthesized using HF containing SiF ４ , a mixture of the organofluorine compound and SiF ４ is obtained. Both the organofluorine compound and silicon tetrafluoride (SiF ４ ) have applications as semiconductor etching gases.

[0003] Andrew A. Lindley, Journal of Geoscience and Environment Protection, 2023, 11, 1-16

[0004] However, since SiF ４ is a gas at normal temperature and normal pressure, it is difficult to separate it from gaseous organofluorine compounds.

[0005] Accordingly, an object of one embodiment of the present disclosure is to provide a removal method capable of selectively removing SiF ４ from a mixture with an organofluorine compound, a method for regenerating a specific metal salt used in the removal method, a removal cycle method, and a method for producing a high-purity organofluorine compound. ４

[0006] ​This disclosure includes the following aspects: <1> A removal method for removing at least a portion of silicon tetrafluoride from a mixture comprising at least one organofluorine compound selected from the group consisting of fluorocarbons and fluoroolefins and silicon tetrafluoride, by contacting the mixture with at least one metal salt selected from the group consisting of metal fluorides, alkali metal hydroxides, alkali metal carbonates and alkali metal bicarbonates. <2> The removal method according to <1>, wherein the organofluorine compound is at least one selected from the group consisting of non-chlorinated fluorocarbons and non-chlorinated fluoroolefins. <3> The removal method according to <1> or <2>, wherein the number of carbon atoms in the organofluorine compound is independently 2 or 3. <4> The removal method according to any one of <1> to <3>, wherein the number of carbon atoms in the organofluorine compound is 3. <5> The removal method according to any one of <1> to <4>, wherein the organofluorine compound comprises at least one selected from the group consisting of tetrafluoroethylene, trifluoroethylene, 1,1-difluoroethylene, (E)-1,2-difluoroethylene, (Z)-1,2-difluoroethylene, pentafluoroethane, 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane, 1,1,1-trifluoroethane, 1,1,2-trifluoroethane, 1,1-difluoroethane, 1,2-difluoroethane, and monofluoroethane. <6> The removal method according to any one of <1> to <5>, wherein the contact is carried out at a temperature of 200°C or less. <7> The removal method according to any one of <1> to <6>, wherein the contact is carried out in a gaseous state of the mixture. <8> The removal method according to any one of <1> to <7>, wherein the contact time is 0.1 seconds or more. <9> The removal method according to any one of <1> to <8>, wherein the contact is carried out under pressure conditions of -0.5 to 1.5 MPa. <10> The removal method according to any one of <1> to <9>, wherein the metal fluoride is used in an amount of 2 equivalents or more relative to silicon tetrafluoride. <11> The removal method according to any one of <1> to <10>, wherein the water content in the mixture is 10 equivalents or less relative to silicon tetrafluoride.<12> The removal method according to any one of <1> to <11>, wherein the water content in the mixture is 20 mol% or less. <13> The removal method according to any one of <1> to <12>, wherein the hydrogen fluoride content in the mixture is 10 mol% or less. <14> A regeneration method, comprising performing the removal method according to any one of <1> to <13>, then heating to desorb at least a part of silicon tetrafluoride from the metal salt, thereby regenerating the metal salt. <15> The regeneration method according to <14>, wherein the heating is carried out at 400°C or higher. <16> A removal cycle method, comprising bringing the metal salt regenerated by the regeneration method according to <14> into contact with a mixture comprising at least one organofluorine compound selected from the group consisting of fluorocarbons and fluoroolefins, and silicon tetrafluoride, to remove at least a part of the silicon tetrafluoride from the mixture. <17> A method for producing a high-purity organofluorine compound, comprising bringing a mixture comprising at least one organofluorine compound selected from the group consisting of fluorocarbons and fluoroolefins, and silicon tetrafluoride, into contact with at least one metal salt selected from the group consisting of metal fluorides, alkali metal hydroxides, alkali metal carbonates and alkali metal hydrogencarbonates, to remove at least a part of the silicon tetrafluoride from the mixture.

[0007] According to the present disclosure, from an organofluorine compound and SiF ４ from the mixture, SiF ４ can be provided a removal method capable of selectively removing, a method for regenerating the specific metal salt used in the removal method, a removal cycle method, and a method for producing a high-purity organofluorine compound.

[0008] In this disclosure, numerical ranges indicated using "~" mean a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. In numerical ranges described in stages in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Also, in numerical ranges described in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the values ​​shown in the examples. In this disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In this disclosure, the amount of each component means the total amount of multiple substances if there are multiple substances corresponding to each component, unless otherwise specified.

[0009] In this disclosure, a metal fluoride means a metal salt containing an anionic fluorine atom (fluoride ion). ２ SiF ６ It is distinct from fluorine-containing metal compounds that contain covalently bonded fluorine atoms, such as (where M is a metal).

[0010] <Removal Method> The removal method of this disclosure involves at least one organofluorine compound selected from the group consisting of fluorocarbons and fluoroolefins and silicon tetrafluoride (SiF ４ This method involves contacting a mixture containing (hereinafter also referred to as a "specific mixture") with at least one metal salt selected from the group consisting of metal fluorides, alkali metal hydroxides, alkali metal carbonates, and alkali metal bicarbonates (hereinafter also referred to as a "specific metal salt") to remove at least a portion of silicon tetrafluoride from the mixture.

[0011] By the above method, organofluorine compounds and SiF ４ SiF ４ The reason why certain metal salts and SiF are selectively removed is not clear, but ４ When reacted, for example, in the case of metal fluorides (MF, where M is a metal), SiF is produced by the following reaction. ４It is thought that these substances are adsorbed onto MF. Alkali metal hydroxides, alkali metal carbonates, and alkali metal bicarbonates, like MF, are alkaline, and therefore exhibit acidic behavior in SiF. ４ It is presumed to be something that attracts and adsorbs.

[0012]

[0013] The removal method of this disclosure involves contacting a specific metal salt with a mixture containing an organofluorine compound and silicon tetrafluoride. The removal method of this disclosure focuses on the property that organofluorine compounds are not easily adsorbed by the specific metal salt, while silicon tetrafluoride is adsorbed by the specific metal salt. Therefore, HF and SiF produced from fluorite ４ From a mixture containing , organofluorine compounds and Si F ４ After converting to a mixture containing , SiF ４ According to the removal method of this disclosure, which selectively removes HF and SiF ４ This allows for simplification of the purification process in mixtures containing the aforementioned substances. Furthermore, given that the removal method of this disclosure exhibits low adsorption to specific metal salts of organofluorine compounds, it can be applied to a wide range of organofluorine compounds.

[0014] The following describes in detail how to remove this disclosure.

[0015] (Specific mixture) The specific mixture used in the removal method of this disclosure comprises at least one organofluorine compound selected from the group consisting of fluorocarbons and fluoroolefins, and silicon tetrafluoride.

[0016] The organofluorine compounds are not particularly limited and may consist of carbon atoms and fluorine atoms, or they may be hydroorganofluorine compounds (HFC, HFO) further containing hydrogen atoms, or they may be chlorofluorocarbons (CFC), hydrochlorofluorocarbons (HCFC), chlorofluoroolefins (CFO), and hydrochlorofluoroolefins (HCFO) further containing chlorine atoms, or they may further contain oxygen atoms.

[0017] From the viewpoint of boiling point, the organofluorine compound preferably has 1 to 5 carbon atoms, more preferably 1 to 4, even more preferably 2 or 3, and particularly preferably 2 carbon atoms.

[0018] The organofluorine compound is preferably at least one selected from the group consisting of non-chlorine fluorocarbons and non-chlorine fluoroolefins. If the organofluorine compound is a compound that does not contain chlorine atoms, for example, when a fluoroolefin is produced by carrying out a de-HF reaction using a fluorocarbon obtained by the removal method of this disclosure, it is possible to suppress the degradation of the catalyst used in the de-HF reaction by chlorine atoms.

[0019] Specific examples of organofluorine compounds include, for example, tetrafluoroethylene, trifluoroethylene, 1,1-difluoroethylene, (E)-1,2-difluoroethylene, (Z)-1,2-difluoroethylene, pentafluoroethane, 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane, 1,1,1-trifluoroethane, 1,1,2-trifluoroethane, 1,1-difluoroethane, 1,2-difluoroethane, and monofluoroethane. The methods for producing these compounds are not limited, and known methods can be applied.

[0020] SiF in a specific mixture ４ The content of is not particularly limited and may be 1 mol% or more, 2 mol% or more, 3 mol% or more, 4 mol% or more, 5 mol% or more, 10 mol% or more, 20 mol% or more, or 30 mol% or more. SiF in the mixture ４ The content may be 90 mol% or less, 80 mol% or less, or 70 mol% or less.

[0021] SiF in a specific mixture ４ The content is determined by analyzing it using a gas chromatograph and gas chromatograph-mass spectrometer, and then converting it based on the gas chromatography relative sensitivity from the area ratio (GCAare%).

[0022] The water content in the specific mixture is preferably 20 mol% or less, more preferably 15 mol% or less, even more preferably 10 mol% or less, and particularly preferably 5 mol% or less. When the water content in the mixture is within the above range, water and SiF ４ The generation of HF due to the reaction with SiF is suppressed. ４ Because it competes with and adsorbs onto specific metal salts, the SiF generated is due to HF. ４ The decrease in the amount of adsorption to the specific metal salt is suppressed. From the above viewpoint, it is preferable that the water content in the specific mixture be low, but from the viewpoint of the cost of dehydration treatment of the mixture and the difficulty of process control, it may be as low as the detection limit, or 5 mol% or more.

[0023] The water content in the mixture relative to silicon tetrafluoride is preferably 10 equivalents or less, more preferably 5 equivalents or less, even more preferably 3 equivalents or less, particularly preferably 1 equivalent or less, and extremely preferably 0.5 equivalents or less. When the water content relative to silicon tetrafluoride is within the above range, water and SiF ４ The generation of HF due to the reaction with SiF is suppressed. ４ Because it competes with and adsorbs onto specific metal salts, the SiF generated is due to HF. ４ The decrease in the amount of adsorption to the specific metal salt is suppressed. From the above viewpoint, it is preferable that the water content in the specific mixture be low, but from the viewpoint of the cost of dehydration treatment of the mixture and the difficulty of process control, it may be at the detection limit, 0.01 equivalents or more, or 0.05 equivalents or more.

[0024] A common method for measuring water content is to use a dew point meter.

[0025] Furthermore, from the above viewpoint, the HF content in the mixture is preferably 10 mol% or less, more preferably 8 mol% or less, even more preferably 5 mol% or less, and particularly preferably 3 mol% or less. From the above viewpoint, a lower HF content in the mixture is preferable, but from the viewpoint of the cost of purifying the mixture and the difficulty of process control, it may be 1 mol% or more, or even 2 mol% or more.

[0026] The HF content in a specific mixture is determined by analyzing it using a gas chromatograph and gas chromatograph-mass spectrometer, and then converting the area ratio (GCAare%) based on the relative sensitivity of gas chromatography.

[0027] The water content mentioned above refers to the water content in the specific mixture when it is brought into contact with the specific metal salt. When contact is carried out using a reactor as described later, the water content may be replaced with the water content in the specific mixture before it is introduced into the reactor. Similarly, the HF content mentioned above refers to the HF content in the specific mixture when it is brought into contact with the specific metal salt. When contact is carried out using a reactor as described later, the HF content may be replaced with the HF content in the specific mixture before it is introduced into the reactor.

[0028] The specific mixture contains organofluorine compounds and SiF ４ In addition, an inert gas may be included. Preferably, the inert gas is at least one selected from the group consisting of nitrogen, hydrogen, carbon dioxide, and helium. When the specific mixture contains an inert gas, the molar ratio of the organofluorine compound to the inert gas is preferably 0.1 to 5.0, more preferably 0.5 to 3.0, and even more preferably 0.5 to 2.0.

[0029] (Specific Metal Salts) A specific metal salt is at least one selected from the group consisting of metal fluorides, alkali metal hydroxides, alkali metal carbonates, and alkali metal bicarbonates. Examples of metal fluorides include alkali metal fluorides and alkaline earth metal fluorides, specifically NaF, KF, CsF, and MgF. ２ CaF ２ Examples include RbF, etc. Specific examples of alkali metal hydroxides include NaOH, KOH, RbOH, CsOH, etc. Specific examples of alkali metal carbonates include Na ２ CO ３ _K ２ CO ３ , Rb ２ CO ３ , Cs ２ CO ３Examples include NaHCO3. Specifically, examples of alkali metal bicarbonates include NaHCO3. ３ , KHCO ３ , RbHCO ３ , CsHCO ３ These are some examples.

[0030] Among these, metal fluorides are preferred as specific metal salts from the viewpoint of reactivity, alkali metal fluorides are more preferred, and NaF, KF, and CsF are even more preferred.

[0031] The amount of specific metal salt used is preferably 2 equivalents or more, more preferably 5 equivalents or more, and even more preferably 10 equivalents or more, relative to silicon tetrafluoride. If the specific metal salt is used in amounts above the lower limit, SiF ４ It is easily and reliably adsorbed. There is no particular upper limit on the amount of specific metal salt used relative to silicon tetrafluoride. For example, when performing continuous operation, a large excess of specific metal salt may be placed in the reactor in advance, and the specific mixture containing silicon tetrafluoride may be passed through it to bring the specific mixture into contact with the specific metal salt. Thus, there is no upper limit on the amount of specific metal salt used relative to silicon tetrafluoride, but for example, the amount of specific metal salt used relative to silicon tetrafluoride may be 500 equivalents or less, 100 equivalents or less, or 50 equivalents or less.

[0032] (Contact conditions) In the removal method of this disclosure, a specific metal salt is brought into contact with the mixture.

[0033] The temperature at contact is SiF to the specific metal salt. ４ Due to the ease of adsorption, a temperature of 200°C or lower is preferred, 150°C or lower is more preferred, 100°C or lower is still preferred, and it may also be 80°C or lower, 50°C or lower, or 35°C or lower. From the viewpoint of reaction efficiency, the temperature at contact is preferably 10°C or higher, more preferably 20°C or higher, even more preferably 25°C or higher, and particularly preferred to be 30°C or higher. External heating may or may not be performed during contact.

[0034] Since the method is carried out within the temperature range described above, it is preferable that the removal method of this disclosure is carried out in contact with the specific mixture while it is in a gaseous state.

[0035] The contact time between the organofluorine compound and the specific metal salt is preferably 0.1 seconds or more, more preferably 1 second or more, and even more preferably 3 seconds or more. The contact time is preferably 60 seconds or less, more preferably 30 seconds or less, and even more preferably 20 seconds or less. If the contact time is above the lower limit, SiF ４ It is readily adsorbed onto specific metal salts, and if the value is kept below the above upper limit, productivity is excellent.

[0036] The pressure at contact is not particularly limited, but from the viewpoint of improving the removal rate, -0.5 to 1.5 MPa is preferred, -0.5 to 1.0 MPa is more preferred, and atmospheric pressure to 0.5 MPa is even more preferred. In this disclosure, pressure means gauge pressure.

[0037] The reactor used in the removal method of this disclosure is not limited in shape or structure, as long as it can withstand the above-mentioned temperature and pressure. Examples of reactors include cylindrical vertical reactors and U-shaped reactors. Examples of reactor materials include glass, stainless steel, iron, nickel, and alloys mainly composed of iron or nickel. The reactor may be equipped with heating means such as an electric heater for heating the inside of the reactor.

[0038] The reactor described above may be filled with a specific metal salt, and a specific mixture may be circulated through it. In this case, the contact time described above is calculated using the following formula.

[0039] Contact time (seconds) = [Length of the reactor filled with the specific metal salt (cm)] / [Linear velocity (cm / second)] Linear velocity refers to the rate at which the specific mixture passes through the specific metal salt per unit time.

[0040] The linear velocity u varies depending on the diameter of the reaction tube, but is preferably 0.1 to 100 cm / second, and more preferably 1 to 30 cm / second. The linear velocity u is the linear velocity of the specific mixture calculated from the volume of the mixture and the specific metal salt introduced into the reactor. If the linear velocity u of the specific mixture is above the lower limit, productivity improves. In particular, if the linear velocity u is 1 cm / second or higher, the specific mixture flows more uniformly through the specific metal salt. If the linear velocity u of the specific mixture is below the upper limit, the removal rate improves. In particular, if the linear velocity u is 30 cm / second or lower, temperature control by exothermic reaction becomes easier. u = V / S (I) where V is the flow rate (cm) of the specific mixture through which the specific metal salt flows. ３ The value is ( / second), and S is the cross-sectional area (cm²) of a specific mixture of specific metal salts in the direction of flow. ２ ) indicates.

[0041] <Regeneration Method> The regeneration method of this disclosure is a method of regenerating a specific metal salt by heating after performing the removal method of this disclosure to remove at least a portion of silicon tetrafluoride from the specific metal salt.

[0042] The heating temperature is the temperature of the adsorbed SiF ４ From the viewpoint of effectively removing the specific metal salt, a temperature of 400°C or higher is preferred, 450°C or higher is more preferred, 500°C or higher is even more preferred, 600°C or higher is particularly preferred, and 700°C or higher is extremely preferred. From the viewpoint of the melting point, the heating temperature is preferably 1000°C or lower, more preferably 900°C or lower, and even more preferably 800°C or lower.

[0043] The heating time is SiF ４ It is preferable to adjust the time appropriately depending on the amount of adsorption, for example, it may be 1 minute or more, 2 minutes or more, or 5 minutes or more. The upper limit is not particularly limited, but from the viewpoint of reducing production costs and processing time, it may be 10 minutes or less.

[0044] Using the reactor described above, SiF is produced from the mixture. ４ If the SIF is removed, the inflow of the mixture into the reactor is stopped and the reaction tube is heated, and the specific metal salt packed in the reaction tube is converted to SiF. ４ As the substance is released, the specific metal salt is regenerated, and SiF is released from the outlet. ４SiF leaks out. Thus, the removal method and regeneration method of this disclosure adjust the temperature of the specific metal salt to release SiF to the specific metal salt. ４ This is a simple method for performing suction and detachment.

[0045] <Removal Cycle Method> The removal cycle method of this disclosure is a method of contacting a specific metal salt regenerated by the regeneration method of this disclosure with a specific mixture to remove at least a portion of silicon tetrafluoride from the specific mixture. By the regeneration method of this disclosure, SiF ４ The specific metal salt that was regenerated by removing SiF was then used again. ４ It can adsorb the specific metal salt. Therefore, the regenerated specific metal salt may be applied to the removal method of this disclosure.

[0046] Thus, the removal cycle method of this disclosure can be performed by combining the removal method and the regeneration method of this disclosure, and the removal method and the regeneration method of this disclosure may be performed repeatedly. The removal cycle method of this disclosure adjusts the temperature of the specific metal salt to obtain SiF from the specific metal salt. ４ This is a simple method that allows for repeated adsorption and desorption. The regeneration method and removal cycle method of this disclosure allow for the reuse of specific metal salts, thereby reducing the environmental burden in terms of reducing resource consumption and waste.

[0047] <Manufacturing Method> The method for producing the high-purity organofluorine compound of this disclosure is a method of contacting a mixture (specific mixture) containing at least one organofluorine compound selected from the group consisting of fluorocarbons and fluoroolefins and silicon tetrafluoride with at least one metal salt (specific metal salt) selected from the group consisting of metal fluorides, alkali metal hydroxides, alkali metal carbonates and alkali metal bicarbonates, thereby removing at least a portion of silicon tetrafluoride from the mixture.

[0048] In the manufacturing method, fluorocarbons and fluoroolefins, specific mixtures, specific metal salts, and contacts are all synonymous with those described in the removal method.

[0049] The manufacturing method of this disclosure involves SiF in a specific mixture. ４Because it is possible to selectively remove certain substances, it is possible to purify fluorocarbons and fluoroolefins to a high degree. Furthermore, since the manufacturing method of this disclosure has low adsorption properties to specific metal salts of organofluorine compounds, it can be applied to a wide range of organofluorine compounds. In this disclosure, "high purity" means that the purity of the organofluorine compound after applying the manufacturing method of this disclosure is higher than that of the specific mixture before applying the manufacturing method of this disclosure.

[0050] The present disclosure will be further described below with reference to examples, but the present disclosure is not limited to the following examples unless it exceeds the spirit of the disclosure. Examples 1 to 3 and 8 are examples, and Examples 4 to 7 are comparative examples.

[0051] [Example 1] 88.12 mol% 1,1,1,2-tetrafluoroethane (HFC-134a), 9.50 mol% 1,1,2-trifluoroethylene (HFO-1123), and 2.38 mol% SiF ４ The mixed gas was passed through NaF (22 g in powder form) at 25°C for a contact time of 1 second at a pressure of 0 MPa (gauge pressure). At this time, the water content was 2 equivalents relative to silicon tetrafluoride, and the hydrogen fluoride content in the mixed gas was 5 mol% or less. The gas after passing through was analyzed using a gas chromatograph and a gas chromatograph-mass spectrometer (GCMS). Specifically, the analysis was performed using a gas chromatograph (product name "GC6850", manufactured by Agilent) with a column (product name "DB-1", manufactured by Agilent, length 60 m, inner diameter 0.25 mm, film thickness 1 μm). Furthermore, a gas chromatograph (product name "DB-1", manufactured by Agilent, length 60 m, inner diameter 0.25 mm, film thickness 1 μm) was attached to the gas chromatograph of a gas chromatograph-mass spectrometer (gas chromatograph: product name "GC7890A", manufactured by Agilent, and mass spectrometer: product name "5975C", manufactured by Agilent), and the ionization mode of the mass spectrometer was set to electron ionization (EI) for analysis. The gas after passing through was SiF ４ The signal from which it originated had disappeared.

[0052] [Example 2] In Example 1, NaF (22 g in powder form) is replaced with KF (43 g), resulting in 89.35 mol% 1,1,1,2-tetrafluoroethane (HFC-134a), 8.52 mol% 1,1,2-trifluoroethylene (HFO-1123), and 2.13 mol% SiF ４ Except for using a mixed gas, the procedure was the same, and the gas after passing through was analyzed by GCMS, and SiF ４ The signal from which it originated had disappeared.

[0053] [Example 3] In Example 1, NaF (22 g in powder form) is replaced with CsF (23 g), resulting in 89.48 mol% 1,1,1,2-tetrafluoroethane (HFC-134a), 8.42 mol% 1,1,2-trifluoroethylene (HFO-1123), and 2.10 mol% SiF ４ Except for using a mixed gas, the procedure was the same, and the gas after passing through was analyzed by GCMS, and SiF ４ The signal from which it originated had disappeared.

[0054] [Example 4] In Example 1, NaF (22 g in powder form) is replaced with MS3A molecular sieve (16 g), resulting in 87.88 mol% 1,1,1,2-tetrafluoroethane (HFC-134a), 9.70 mol% 1,1,2-trifluoroethylene (HFO-1123), and 2.42 mol% SiF ４ Except for using a mixed gas, the procedure was the same, and the gas after passing through was analyzed by GCMS, and SiF ４ The original signal had not disappeared.

[0055] [Example 5] In Example 1, NaF (22 g in powder form) is replaced with silica sand (22 g), resulting in 88.76 mol% 1,1,1,2-tetrafluoroethane (HFC-134a), 8.99 mol% 1,1,2-trifluoroethylene (HFO-1123), and 2.25 mol% SiF ４ Except for using a mixed gas, the procedure was the same, and the gas after passing through was analyzed by GCMS, and SiF ４ The original signal had not disappeared.

[0056] [Example 6] In Example 1, NaF (22 g in powder form) was replaced with Na ２ SiF ６Replace (26g) with 88.77 mol% 1,1,1,2-tetrafluoroethane (HFC-134a), 8.98 mol% 1,1,2-trifluoroethylene (HFO-1123), and 2.25 mol% SiF ４ Except for using a mixed gas, the procedure was the same, and the gas after passing through was analyzed by GCMS, and SiF ４ The original signal had not disappeared.

[0057] [Example 7] In Example 1, NaF (22 g in powder form) is K ２ SiF ６ Replace (26g) with 88.15 mol% 1,1,1,2-tetrafluoroethane (HFC-134a), 9.48 mol% 1,1,2-trifluoroethylene (HFO-1123), and 2.37 mol% SiF ４ Except for using a mixed gas, the procedure was the same, and the gas after passing through was analyzed by GCMS, and SiF ４ The original signal had not disappeared.

[0058] [Example 8] (Regeneration of metal salts) After stopping the inflow of organofluorine compounds into the reactor, Na ２ SiF ６ When heated to 650°C, SiF ４ The release of SiF was confirmed. ４ Due to the release of Na ２ SiF ６ It is presumed that it is being regenerated into NaF.

[0059] The disclosure of Japanese Patent Application No. 2025-067005 is incorporated in its entirety by reference. All documents, patent applications, and technical standards in this disclosure are incorporated by reference to the same extent as if each individual document, patent application, and technical standard had been specifically and individually noted as being incorporated by reference.

Claims

1. A removal method for removing at least a portion of silicon tetrafluoride from a mixture comprising at least one organofluorine compound selected from the group consisting of fluorocarbons and fluoroolefins and silicon tetrafluoride, by contacting the mixture with at least one metal salt selected from the group consisting of metal fluorides, alkali metal hydroxides, alkali metal carbonates and alkali metal bicarbonates.

2. The removal method according to claim 1, wherein the organofluorine compound is at least one selected from the group consisting of non-chlorine fluorocarbons and non-chlorine fluoroolefins.

3. The removal method according to claim 1, wherein the number of carbon atoms in each of the organofluorine compounds is independently 2 or 3.

4. The removal method according to claim 1, wherein the number of carbon atoms in the organofluorine compound is 3.

5. The removal method according to claim 1, wherein the organofluorine compound comprises at least one selected from the group consisting of tetrafluoroethylene, trifluoroethylene, 1,1-difluoroethylene, (E)-1,2-difluoroethylene, (Z)-1,2-difluoroethylene, pentafluoroethane, 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane, 1,1,1-trifluoroethane, 1,1,2-trifluoroethane, 1,1-difluoroethane, 1,2-difluoroethane, and monofluoroethane.

6. The removal method according to claim 1, wherein the contact is performed at a temperature of 200°C or less.

7. The removal method according to claim 1, wherein the contact is carried out in which the mixture is in a gaseous state.

8. The removal method according to claim 1, wherein the contact time is 0.1 seconds or more.

9. The removal method according to claim 1, wherein the contact is performed under pressure conditions of -0.5 to 1.5 MPa.

10. The removal method according to claim 1, wherein the metal fluoride is used in an amount of 2 equivalents or more relative to silicon tetrafluoride.

11. The removal method according to claim 1, wherein the water content in the mixture is 10 equivalents or less relative to silicon tetrafluoride.

12. The removal method according to claim 1, wherein the water content in the mixture is 20 mol% or less.

13. The removal method according to claim 1, wherein the hydrogen fluoride content in the mixture is 10 mol% or less.

14. A regeneration method for regenerating a metal salt, comprising performing the removal method described in any one of claims 1 to 13, and then heating to remove at least a portion of silicon tetrafluoride from the metal salt.

15. The regeneration method according to claim 14, wherein the heating is performed at 400°C or higher.

16. A removal cycle method comprising contacting the metal salt regenerated by the regeneration method described in claim 14 with a mixture containing at least one organofluorine compound selected from the group consisting of fluorocarbons and fluoroolefins and silicon tetrafluoride, thereby removing at least a portion of silicon tetrafluoride from the mixture.

17. A method for producing a high-purity organofluorine compound, comprising contacting a mixture containing at least one organofluorine compound selected from the group consisting of fluorocarbons and fluoroolefins and silicon tetrafluoride with at least one metal salt selected from the group consisting of metal fluorides, alkali metal hydroxides, alkali metal carbonates and alkali metal bicarbonates, thereby removing at least a portion of silicon tetrafluoride from the mixture.

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