Method for separating vinylidene fluoride and trifluoromethane, composition, and method for producing composition

Abstract

A method for separating vinylidene fluoride and trifluoromethane, which comprises: a step in which a mixture containing vinylidene fluoride and trifluoromethane is mixed with a compound having a boiling point of-60 to 0 DEG C to obtain a mixture for extraction; and a step in which the mixture for extraction is distilled to obtain a distillate having vinylidene fluoride as the main component and a bottom product having a compound having a boiling point of-60 to 0 DEG C as the main component and further containing trifluoromethane.

Description

TECHNICAL FIELD

[0001] The present application relates to a separation method of vinylidene fluoride and trifluoromethane, and a composition and a production method of the composition. BACKGROUND

[0002] Vinylidene fluoride is useful as a monomer of a fluororesin.

[0003] For example, Patent Literature 1 describes a separation method of vinylidene fluoride and trifluoroethane, characterized by comprising: a step of adding, to a first mixture containing vinylidene fluoride and trifluoroethane, a first extraction solvent selected from at least one of the group consisting of an alcohol having 1 to 3 carbon atoms, a ketone, an ester, an amide, an ether, a sulfoxide, and a nitrile to obtain a second mixture; and an extractive distillation step of subjecting the second mixture to distillation to obtain a distillate mainly containing vinylidene fluoride and a bottom product mainly containing the first extraction solvent and containing trifluoroethane.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: International Publication No. 2015 / 072305 SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] However, in Patent Literature 1, as the extraction solvent, at least one selected from the group consisting of an alcohol having 1 to 3 carbon atoms, a ketone, an ester, an amide, an ether, a sulfoxide, and a nitrile is used, and there is a tendency that energy required for distillation for recovering the extraction solvent is high.

[0009] An object of one embodiment of the present application is to provide a separation method of vinylidene fluoride and trifluoromethane that can obtain high-purity vinylidene fluoride from a mixture containing vinylidene fluoride and trifluoromethane and can recover an extraction solvent with lower energy than in the past, a composition related to the separation method, and a production method of the composition.

[0010] MEANS FOR SOLVING THE PROBLEMS

[0011] The present disclosure includes the following modes.

[0012] <1>

[0013] A separation method of vinylidene fluoride and trifluoromethane includes:

[0014] a step of mixing a mixture containing vinylidene fluoride and trifluoromethane with a compound having a boiling point of -60 to 0°C to obtain an extraction mixture; and

[0015] distilling the mixture for extraction to obtain a distillate in which the main component is vinylidene fluoride and a bottom product in which the main component is a compound having a boiling point of -60 to 0°C and which also contains trifluoromethane.

[0016] <2>

[0017] The separation method of vinylidene fluoride and trifluoromethane according to <1>, wherein the interaction distance Ra of trifluoromethane with the compound having a boiling point of -60 to 0°C calculated from the value of the Hansen solubility parameter R23 is less than the interaction distance Ra of vinylidene fluoride with the compound having a boiling point of -60 to 0°C. VdF .

[0018] <3>

[0019] The separation method of vinylidene fluoride and trifluoromethane according to <2>, wherein the ratio of the interaction distance Ra R23 to the interaction distance Ra VdF is 0.81 or less.

[0020] <4>

[0021] The separation method of vinylidene fluoride and trifluoromethane according to any one of <1> to <3>, wherein the compound having a boiling point of -60 to 0°C has a boiling point of -60 to -10°C.

[0022] <5>

[0023] The separation method of vinylidene fluoride and trifluoromethane according to any one of <1> to <4>, wherein the compound having a boiling point of -60 to 0°C has a boiling point of -60 to -30°C.

[0024] <6>

[0025] The separation method of vinylidene fluoride and trifluoromethane according to any one of <1> to <5>, wherein the compound having a boiling point of -60 to 0°C is a hydrofluorocarbon.

[0026] <7>

[0027] The separation method of vinylidene fluoride and trifluoromethane according to any one of <1> to <5>, wherein the compound having a boiling point of -60 to 0°C is at least one selected from the group consisting of difluoromethane, chlorofluoromethane, ammonia, isocyanic acid, ethyl azide, azido propylene, formyl fluoride, formaldehyde, and sulfur dioxide.

[0028] <8>

[0029] The separation method of vinylidene fluoride and trifluoromethane according to any one of <1> to <7>, wherein the ratio of the molar amount of the compound having a boiling point of -60 to 0°C to the total molar amount of vinylidene fluoride and trifluoromethane in the extraction mixture is 1 to 100.

[0030] <9>

[0031] The separation method of vinylidene fluoride and trifluoromethane according to any one of <1> to <8>, wherein the process of distilling the bottom product to recover the compound having a boiling point of -60 to 0°C is further included.

[0032] <10>

[0033] The separation method of vinylidene fluoride and trifluoromethane according to <9>, wherein the recovered compound having a boiling point of -60 to 0°C is reused in the process of obtaining the extraction mixture.

[0034] <11>

[0035] A composition comprising vinylidene fluoride, trifluoromethane, and a compound having a boiling point of -60 to 0°C, the content of vinylidene fluoride being 99 mol% or more relative to the total amount of the composition.

[0036] <12>

[0037] A method for producing a composition, comprising:

[0038] a process of mixing a mixture containing vinylidene fluoride and trifluoromethane with a compound having a boiling point of -60 to 0°C to obtain an extraction mixture; and

[0039] a process of distilling the extraction mixture to obtain a composition in which the main component is vinylidene fluoride.

[0040] Effects of the Invention

[0041] According to one embodiment of the present invention, there are provided: a separation method of vinylidene fluoride and trifluoromethane capable of obtaining high-purity vinylidene fluoride from a mixture containing vinylidene fluoride and trifluoromethane and capable of recovering an extraction solvent with lower energy than in the past; a composition related to the above separation method; and a method for producing a composition. DETAILED DESCRIPTION

[0042] In the present disclosure, a numerical range indicated using “~” means a range in which the values recited before and after “~” are respectively taken as the minimum value and the maximum value.

[0043] In the numerical ranges described in stages in this disclosure, the upper limit or lower limit described in a certain numerical range may also be replaced by the upper limit or lower limit of the numerical range described in another stage. In addition, in the numerical ranges described in this disclosure, the upper limit or lower limit described in a certain numerical range may also be replaced by the value shown in the Examples.

[0044] In the present disclosure, a combination of two or more preferred aspects is a more preferred aspect.

[0045] In the present disclosure, when there are a plurality of substances corresponding to each component, the amount of each component refers to the total amount of the plurality of substances unless otherwise specified.

[0046] In the present disclosure, the “distillate” refers to a substance distilled from the top side of a distillation column, and the “bottom product” refers to a substance distilled from the bottom side of a distillation column.

[0047] In this disclosure, the term "main component" means that the amount of components other than the main component is relatively small. The amount of the "main component" is preferably 50 mol% or more of the total, more preferably 60 mol% or more, further preferably 70 mol% or more, and most preferably 80 mol% or more.

[0048] In the present invention, unless otherwise specified, the boiling point of a compound is the value at normal pressure, which is 1.013×10 5 Pa.

[0049] [Method for Separating VdF and R23]

[0050] The method for separating vinylidene fluoride (VdF) and trifluoromethane (R23) disclosed herein includes the following steps: a step of mixing a mixture containing VdF and R23 with a compound having a boiling point of -60 to 0°C to obtain an extraction mixture; and a step of distilling the extraction mixture to obtain a distillate whose main component is VdF and a bottom product whose main component is a compound having a boiling point of -60 to 0°C and further containing R23.

[0051] According to the method for separating VdF and R23 disclosed herein, high-purity VdF can be obtained from a mixture containing VdF and R23, and the extraction solvent can be recovered from the mixture of R23 and the extraction solvent after separation of VdF using lower energy than conventional methods, and the separability of R23 from the extraction solvent is also excellent.

[0052] VdF is useful as a monomer of a fluororesin, but for example, when a polymerization reaction is performed using a composition containing VdF and R23 as an impurity, in the latter half of the polymerization step, R23 that is not consumed in the polymerization reaction accumulates inside the reactor, hindering the polymerization reaction. As a result, there is a tendency for the rate of the polymerization reaction to decrease or for the polymerization reaction to stop, making it impossible to obtain the target polymer. Therefore, it is desirable to separate VdF and R23 and obtain high-purity VdF. However, the boiling point of VdF is -83°C, and the boiling point of R23 is -82°C. Since the boiling points of VdF and R23 are close, and the mixture of VdF and R23 has an azeotropic composition, it is difficult to separate and purify VdF and R23 by ordinary distillation.

[0053] Therefore, Patent Literature 1 describes performing extractive distillation using at least one extraction solvent selected from the group consisting of alcohols, ketones, esters, amides, ethers, sulfoxides, and nitriles having 1 to 3 carbon atoms. The extraction solvent described in Patent Literature 1 has a boiling point as high as 40°C to 250°C. Since the extraction solvent has a high boiling point, there is a tendency for distillation for recovering the extraction solvent contained in the bottom product after extractive distillation to require a large amount of energy.

[0054] The present inventors and others have found that by using a compound having a boiling point of -60 to 0°C as an extraction solvent, it is possible to recover the extraction solvent with less energy than in the past.

[0055] Hereinafter, each step of the method for separating VdF and R23 according to the present disclosure will be described.

[0056] <mixing step>

[0057] The method for separating VdF and R23 according to the present disclosure includes a step of mixing a mixture containing VdF and R23 with a compound having a boiling point of -60 to 0°C to obtain an extraction mixture (hereinafter also referred to as "mixing step").

[0058] (mixture containing VdF and R23)

[0059] The mixture containing VdF and R23 can contain other components in addition to VdF and R23, but from the viewpoint of efficiently obtaining high-purity VdF, it is preferable for the content of other components to be small. As other components, for example, fluorinated olefins other than VdF and hydrofluorocarbons other than R23 can be given.

[0060] The total content of VdF and R23 is, for example, 50 mol% or more, can be 80 mol% or more, can be 90 mol% or more, can be 99 mol% or more, and can be 100 mol%, with respect to the total amount of the mixture containing VdF and R23.

[0061] The molar ratio of VdF to R23 in the mixture containing VdF and R23 is not particularly limited. From the viewpoint of production efficiency, the ratio of the molar amount of R23 to the molar amount of VdF (i.e., the molar ratio) is preferably 0.01 to 1, more preferably 0.01 to 0.5, and further preferably 0.01 to 0.1.

[0062] As the mixture containing VdF and R23, for example, a reaction product containing VdF obtained by reacting various raw materials can be used for the purpose of manufacturing VdF.

[0063] For example, a reaction product containing VdF can be obtained by a dehydrochlorination reaction using chlorodifluoroethane as a raw material. In addition, a reaction product containing VdF can be obtained by a dehydrochlorination reaction using chlorodifluoromethane and chloromethane as raw materials.

[0064] (Compound having a boiling point of -60 to 0°C)

[0065] A compound having a boiling point of -60 to 0°C (hereinafter also referred to as "compound C") is positioned as an extraction solvent. Compound C can be one or two or more.

[0066] The boiling point of compound C is -60°C or higher, and thus the difference from the boiling point of R23 is large, and R23 is easily separated. In addition, the boiling point of compound C is 0°C or lower, and thus when distillation column bottoms are distilled to recover compound C, it is possible to recover with lower energy than in the past.

[0067] From the viewpoints of the decrease in the bottom temperature of the distillation column at the time of recovery by distillation and the reduction in the amount of heat required for heating, the boiling point of compound C is preferably -60 to -10°C, and more preferably -60 to -30°C.

[0068] Specifically, compound C is preferably a hydrofluorocarbon (HFC). As the HFC, for example, difluoromethane (HFC-32) can be given. The HFC is preferable in that the reactivity with other compounds is low and self-decomposition does not occur. In addition, the HFC is preferable in that the redox property is low, and thus the deterioration of the manufacturing apparatus can be suppressed.

[0069] In addition, compound C is preferably at least one selected from the group consisting of difluoromethane (HFC-32), chlorofluoromethane (HCFC-31), ammonia, isocyanic acid, ethyl azide, azido propylene, formyl fluoride, formaldehyde, and sulfur dioxide.

[0070] Among them, from the viewpoint of separation, compound C is preferably HFC-32.

[0071] From the viewpoint of separation, it is preferable that the interaction distance Ra R23Smaller than the interaction distance Ra between VdF and compound C VdF From the perspective of separating VdF and R23 with high efficiency, the interaction distance Ra R23 Relative to the interaction distance Ra VdF The ratio (Ra R23 / Ra VdF ) is preferably 0.81 or less, more preferably 0.79 or less, and further preferably 0.64 or less.

[0072] Here, the interaction distance Ra VdF and interaction distance Ra R23 They are represented by the following formulae (1) and (2), respectively.

[0073] Formula (1): Ra VdF =[4×(δD VdF -δD C ) 2 +(δP VdF -δP C ) 2 +(δH VdF -δH C ) 2 ] 0.5

[0074] Formula (2): Ra R23 =[4×(δD R23 -δD C ) 2 +(δP R23 -δP C ) 2 +(δH R23 -δH C ) 2 ] 0.5

[0075] In formulas (1) and (2), δD VdF ,δP VdF and δH VdF They represent the dispersion term, polar term and hydrogen bond term in the Hansen solubility parameter of VdF, δD R23 ,δP R23 and δH R23 They represent the dispersion term, polar term and hydrogen bond term in the Hansen solubility parameter of R23, δD C ,δP C and δH C They represent the dispersion term, polar term, and hydrogen bond term in the Hansen solubility parameter of boiling point compound C, and the unit is (MPa) 1 / 2 .

[0076] Note that the dispersion term, the polarity term, and the hydrogen bond term in the Hansen solubility parameter of each of the above compounds are values calculated from literature values or the chemical structure of the compound by computer software (Hansen Solubility Parameters in Practice (HSPiP) version 4). The Hansen solubility parameter of a mixture containing two or more compounds is calculated as the vector sum of the values obtained by multiplying the Hansen solubility parameter of each compound by the volume ratio of each compound with respect to the entire mixture.

[0077] In the process of obtaining the extraction mixture, from the viewpoint of separating VdF and R23 with high efficiency, the ratio of the molar amount of compound C to the total molar amount of VdF and R23 in the extraction mixture (i.e., "compound C / (VdF+R23)") is preferably 1 to 100, more preferably 1 to 50.

[0078] For example, as described later, when a mixture containing VdF and R23 is supplied to the extractive distillation column, and further, compound C is supplied to the extractive distillation column, "compound C / (VdF+R23)" represents the molar ratio of the supply amount of compound C supplied to the extractive distillation column to the total supply amount of VdF and R23 supplied to the extractive distillation column.

[0079] The mixing method of the mixture containing VdF and R23 and compound C is not particularly limited. Compound C can be added to the mixture containing VdF and R23, or the mixture containing VdF and R23 can be added to compound C.

[0080] In addition, the timing of obtaining the extraction mixture is not particularly limited as long as it is before distillation of the extraction mixture.

[0081] From the viewpoint of the distillation efficiency of the extraction mixture described later, it is preferable to supply compound C to the extractive distillation column to which the mixture containing VdF and R23 is supplied, to prepare the extraction mixture in the extractive distillation column, and to perform distillation at the same time as the preparation ends.

[0082] In the extraction mixture, as other components other than VdF, R23, and compound C, other components that can be contained in the above mixture containing VdF and R23 can be mentioned.

[0083] <Extractive distillation process>

[0084] The separation method of VdF and R23 of the present disclosure includes a process of distilling the extraction mixture to obtain a distillate in which VdF is a main component and a bottom product in which a compound having a boiling point of -60 to 0°C and also containing trifluoromethane are contained (hereinafter also referred to as "extraction separation process").

[0085] The extractive distillation process can be performed using a distillation apparatus commonly used, such as a distillation column such as a plate column, a packed column, and the like. The various conditions of the extractive distillation process, such as the operating temperature, the operating pressure, the reflux ratio, the total number of plates of the distillation column, the position of the feed plate, the position of the extractant feed plate, and the like, are not particularly limited and can be appropriately selected in order to achieve the intended separation. In the case where a distillation column is used as a plate column in the extractive distillation process, the number of plates of the distillation column can be, for example, 1 to 100, and is preferably 30 or more, and more preferably 50 or more from the viewpoint of obtaining VdF having high purity. VdF and R23 each have a low boiling point, and thus it is preferable to perform the extractive distillation under pressure, for example, at a pressure of 0 to 5 MPaG (gauge pressure).

[0086] Further, the temperature at the top and the bottom of the distillation column is determined depending on the operating pressure and the composition of the distillate and the bottom product. In order to economically perform the distillation operation, the temperature at the top is preferably -60 to 100°C, and the temperature at the bottom is preferably -10 to 300°C, taking into account the temperature of the condensers and the reboilers provided at the top and the bottom. The extractive distillation can be batchwise or continuous, and can also be semi-continuous in which the distillate and the bottom product are intermittently taken out, or the feed is intermittently performed, as appropriate. For the extractant, it is preferable to continuously supply to the distillation apparatus.

[0087] Compound C has an affinity with R23. Therefore, by performing extractive distillation on an extractive mixture containing VdF and R23 and Compound C, a distillate in which VdF is the main component can be obtained from the top side of the extractive distillation column. The distillate is not limited in composition as long as it contains VdF as the main component, and the mole fraction of VdF in the distillate is preferably 90 mol% or more, and more preferably 99 mol% or more. In addition, the mole fraction of R23 in the distillate is preferably 1 / 10 or less, and more preferably 1 / 100 or less, of the mole fraction of R23 in the extractive mixture. The mole fraction of R23 in the distillate is preferably 10 mol% or less, and more preferably 1 mol% or less.

[0088] A bottom product in which Compound C is the main component and also contains R23 can be obtained from the bottom side of the extractive distillation column. The bottom product is not limited in composition as long as it contains Compound C as the main component, and the mole fraction of Compound C in the bottom product is preferably 30 mol% or more, and more preferably 50 mol% or more.

[0089] <Distillation Process>

[0090] The separation method of VdF and R23 of the present disclosure preferably further includes a process of distilling the bottom product to recover Compound C (hereinafter also referred to as "distillation process").

[0091] The distillation step can be performed using the same distillation apparatus as the above extraction distillation step. The various conditions of the distillation step, such as the operation temperature, the operation pressure, the reflux ratio, the total number of plates of the distillation column, the position of the feed plate, and the like, are not particularly limited and can be appropriately selected in order to achieve the target separation.

[0092] By the distillation step, compound C is separated from VdF and R23, and compound C can be recovered.

[0093] In the distillation step, a bottom product containing compound C is obtained from the bottom side of the distillation column. The recovered compound C is preferably reused in the above extraction distillation step. In the separation method of VdF and R23 of the present disclosure, since the boiling points of R23 and compound C are greatly different, the separation of R23 and compound C is excellent. Therefore, compound C of high purity can be recovered, and reuse is suitable.

[0094] [Composition]

[0095] The composition of one embodiment of the present disclosure is a composition containing VdF, R23, and compound C, in which the content of VdF is 99 mol% or more, preferably 99.5 mol% or more, and more preferably 99.9 mol% or more, relative to the total amount of the composition.

[0096] In the composition of one embodiment of the present disclosure, R23 and compound C are impurities, and it is preferable that they be less, and it is desirable that they not be contained substantially. However, from the viewpoint of simplifying the manufacturing process, compound C can also be contained.

[0097] The content of R23 is preferably 1 mol% or less, more preferably 0.5 mol% or less, and further preferably 0.1 mol% or less, relative to the total amount of the composition. In addition, the content of R23 is preferably 1 mol ppm or more, more preferably 5 mol ppm or more, and further preferably 10 mol ppm or more, relative to the total amount of the composition.

[0098] The content of compound C is preferably 1 mol% or less, more preferably 0.5 mol% or less, and further preferably 0.1 mol% or less, relative to the total amount of the composition. In addition, the content of R23 is preferably 1 mol ppm or more, more preferably 5 mol ppm or more, and further preferably 10 mol ppm or more, relative to the total amount of the composition.

[0099] The composition of one embodiment of the present disclosure can contain other components in addition to VdF, R23, and compound C. As the other components, the same components as those that can be contained in the above mixture containing VdF and R23 can be given.

[0100] For the composition containing VdF, R23, and the compound C, and having a content of VdF of 99 mass% or more with respect to the total amount of the composition, for example, it is possible to obtain by subjecting a mixture containing VdF and R23 to separation using the above separation method.

[0101] [Method for producing the composition]

[0102] The method for producing the composition of one embodiment of the present disclosure includes a step of mixing a mixture containing VdF and R23 with the compound C to obtain an extraction mixture, and a step of distilling the extraction mixture to obtain a composition in which VdF is a main component.

[0103] The step of obtaining the extraction mixture is the same as the step of obtaining the extraction mixture in the separation method of one embodiment of the present disclosure.

[0104] The step of distilling the extraction mixture to obtain a composition in which VdF is a main component is the same as the step of distilling the extraction mixture to obtain a distillate in which VdF is a main component in the separation method of one embodiment of the present disclosure.

[0105] In addition, the method for producing the composition of one embodiment of the present disclosure can include a step of mixing a mixture containing VdF and R23 with the compound C to obtain an extraction mixture, and a step of distilling the extraction mixture to separately obtain a composition in which VdF is a main component and a composition in which the compound C is a main component and further contains R23.

[0106] Example

[0107] Hereinafter, the present disclosure will be specifically described by examples, but the present disclosure is not limited to these examples.

[0108] As the extraction solvent (the compound C), HFC-32 (hereinafter referred to as "R32") was used.

[0109] Interaction distance Ra between R23 and R32 R23 : 3.6

[0110] Interaction distance Ra between VdF and R32 VdF : 6.8

[0111] [Gas-liquid equilibrium test (VdF and R23)]

[0112] A gas-liquid equilibrium test was performed using VdF and R23.

[0113] In a 75 mL autoclave with a pressure gauge, VdF and R23 were added, and the temperature was slowly increased to a predetermined pressure using an external heater. After the pressure reached the predetermined value, the temperature was maintained for a certain period of time to stabilize the composition in the autoclave. Next, samples of the test sample were collected from the gas phase and the liquid phase, respectively, and analyzed by gas chromatography to determine the molar ratio of VdF to R23.

[0114] In addition, the relative volatility was calculated using the concentration of VdF in the gas phase (VdF gas phase concentration), the concentration of R23 in the gas phase (R23 gas phase concentration), the concentration of VdF in the liquid phase (VdF liquid phase concentration), and the concentration of R23 in the liquid phase (R23 liquid phase concentration).

[0115] Relative volatility α = {(VdF gas phase concentration / R23 gas phase concentration) / (VdF liquid phase concentration / R23 liquid phase concentration)}

[0116] The measurement results and the calculation results are shown in Table 1.

[0117] <Gas-liquid equilibrium test (VdF, R23, and R32)>

[0118] A gas-liquid equilibrium test was performed using VdF, R23, and R32.

[0119] In a 75 mL autoclave with a pressure gauge, VdF, R23, and R32 were added, and the temperature was slowly increased to a predetermined pressure using an external heater. After the pressure reached the predetermined value, the temperature was maintained for a certain period of time to stabilize the composition in the autoclave. Next, samples of the test sample were collected from the gas phase and the liquid phase, respectively, and analyzed by gas chromatography to determine the molar ratio of VdF, R23, and R32. In addition, the relative volatility was calculated.

[0120] The measurement results and the calculation results are shown in Table 2.

[0121] [Table 1]

[0122]

[0123] [Table 2]

[0124]

[0125] As shown in Table 1, in the range where the VdF gas phase concentration is 9.2 mol% to 27.6 mol%, the relative volatility is greater than 1, and a large amount of R23 is present in the liquid phase. On the other hand, in the range where the VdF gas phase concentration is 42.3 mol% to 87.1 mol%, the relative volatility is less than 1, and it is known that the mixture of VdF and R23 is an azeotrope.

[0126] As shown in Table 2, by adding R32, the relative volatility of VdF and R23 becomes 1.657. The concentration of VdF exceeds 80 mol% relative to the total amount of VdF and R23, and if it is these two components of VdF and R23, the relative volatility is less than 1 (Table 1), and by adding R32, the relative volatility becomes greater than 1, and it is known that R23 is extracted into the liquid phase.

[0127] The results of the above-mentioned gas-liquid equilibrium test were reflected using a process simulator Chemcad, and simulation of extractive distillation and simulation of distillation were performed. In the simulation, a distillation column having the same number of plates was used, and extractive distillation was performed in Example 1, and ordinary distillation was performed in Example 2. The results are shown in Table 3. Example 1 is a comparative example, and Example 2 is an embodiment.

[0128] [Table 3]

[0129]

[0130] As shown in Table 3, in Example 1, the purity of VdF is 98.01 mol%, and in contrast, in Example 2, it is 99.94 mol%.

[0131] Further, in the past, when the boiling point of the extractive solvent is as high as 40 to 250°C, there has been a tendency for distillation for recovering the extractive solvent contained in the bottom product after extractive distillation to require a large amount of energy. In contrast, in Example 2, the boiling point of the extractive solvent is -60 to 0°C, and it is possible to recover the extractive solvent with lower energy than in the past.

[0132] Note that the contents of R23 and R32 in the distillate in extractive distillation are small amounts, and therefore, 0.00 is described in Table 3, but in detail, the content of R23 is 563 ppm mol, and the content of R32 is 16 ppm mol.

[0133] Note that the disclosure of Japanese Patent Application No. 2023-030193, filed on February 28, 2023, is incorporated herein by reference in its entirety. In addition, all documents, patent applications, and technical standards cited in the present specification are incorporated herein by reference to the same extent as if each individual document, patent application, or technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. A method for separating vinylidene fluoride and trifluoromethane, comprising: A step of mixing a mixture containing vinylidene fluoride and trifluoromethane with a compound having a boiling point of -60 to 0°C to obtain an extraction mixture; as well as A step of distilling the extraction mixture to obtain a distillate whose main component is vinylidene fluoride and a bottom product whose main component is a compound having a boiling point of -60 to 0°C and further contains trifluoromethane.

2. The method for separating vinylidene fluoride and trifluoromethane according to claim 1, wherein: The interaction distance Ra between trifluoromethane and the compound with a boiling point of -60 to 0°C obtained from the value of the Hansen solubility parameter R23 Less than the interaction distance Ra between vinylidene fluoride and the compound with a boiling point of -60 to 0°C VdF .

3. The method for separating vinylidene fluoride and trifluoromethane according to claim 2, wherein: The interaction distance Ra R23 Relative to the interaction distance Ra VdF The ratio is below 0.

81.

4. The method for separating vinylidene fluoride and trifluoromethane according to any one of claims 1 to 3, wherein The compound with a boiling point of -60 to 0°C has a boiling point of -60 to -10°C.

5. The method for separating vinylidene fluoride and trifluoromethane according to any one of claims 1 to 3, wherein The compound with a boiling point of -60 to 0°C has a boiling point of -60 to -30°C.

6. The method for separating vinylidene fluoride and trifluoromethane according to any one of claims 1 to 3, wherein The compound with a boiling point of -60 to 0° C. is a hydrofluorocarbon.

7. The method for separating vinylidene fluoride and trifluoromethane according to any one of claims 1 to 3, wherein The compound with a boiling point of -60 to 0° C. is at least one selected from the group consisting of difluoromethane, chlorofluoromethane, ammonia, isocyanic acid, ethyl azide, propylene azide, formyl fluoride, formaldehyde and sulfur dioxide.

8. The method for separating vinylidene fluoride and trifluoromethane according to any one of claims 1 to 3, wherein In the extraction mixture, the ratio of the molar amount of the compound having a boiling point of -60 to 0°C to the total molar amount of vinylidene fluoride and trifluoromethane is 1 to 100.

9. The method for separating vinylidene fluoride and trifluoromethane according to any one of claims 1 to 3, wherein The method further includes distilling the bottom product to recover the compound having a boiling point of -60 to 0°C.

10. The method for separating vinylidene fluoride and trifluoromethane according to claim 9, wherein: The recovered compound having a boiling point of -60 to 0°C is reused in the step of obtaining the extraction mixture.

11. A composition comprising vinylidene fluoride, trifluoromethane and a compound having a boiling point of -60 to 0°C, wherein the content of the vinylidene fluoride is 99 mol% or more relative to the total amount of the composition.

12. A method for producing a composition, comprising: A step of mixing a mixture containing vinylidene fluoride and trifluoromethane with a compound having a boiling point of -60 to 0°C to obtain an extraction mixture; as well as A step of distilling the extraction mixture to obtain a composition whose main component is vinylidene fluoride.

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