Method for producing purified difluoromethane (HFC-32) and composition containing HFC-32

Abstract

The present invention provides a method for efficiently purifying difluoromethane (HFC-32). Specifically disclosed is a method for producing purified HFC-32, which comprises: an extraction distillation step wherein a composition containing difluoromethane (HFC-32) and a component X, which is selected from the group consisting of pentafluoroethane (HFC-125), 1, 1, 1, 3, 3, 3-pentafluoroethane (HFC-125), 1, 1, 3, 3, 3-pentafluoroethane (HFC-125), 1, 1, 3, 3, 3-pentafluoroethane (HFC-125), 1, 1, 3, 3, 3-pentafluoroethane (HFC-125), 1, 1, 3, 3, 3-pentafluoroethane (HFC-125) the solvent A is at least one of 1, 1, 1-trifluoroethane (HFC-143a) and dichlorodifluoromethane (CFC-12), and the solvent A is at least one of amine and fluorinated ether.

Description

Technical Field

[0001] This invention relates to a method for producing purified difluoromethane (HFC-32) and compositions containing HFC-32. Background Technology

[0002] HFC-32 is useful as a refrigerant or as a raw material for mixed refrigerants obtained by combining it with other components (e.g., HFC-410A as a mixed refrigerant of HFC-32 and HFC-125).

[0003] Regarding the present invention, for example, Patent Document 1 discloses a method for separating HFC-32 and HFC-125. Specifically, it discloses "a method for separating HFC-32 and HFC-125 from a first mixture using an extractant containing dichloromethane, comprising: adding the extractant to the first mixture to generate a second mixture; separating HFC-32 and HFC-125 from the second mixture by extracting and distilling the second mixture in an extractive distillation zone of a distillation column, thereby recovering HFC-125 as the top product of the column and recovering HFC-32 from the bottom of the column."

[0004] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2007-91762 Summary of the Invention

[0005] The technical problem that the invention aims to solve The purpose of this invention is to provide a method for efficiently purifying HFC-32 and a composition containing HFC-32.

[0006] Technical solutions for solving technical problems The present invention includes, for example, the solutions described below.

[0007] Item 1. A method for producing purified HFC-32, comprising: contacting a composition containing difluoromethane (HFC-32) and component X with solvent A to obtain an extractive distillation step from which component X is reduced. The aforementioned component X is at least one selected from pentafluoroethane (HFC-125), 1,1,1-trifluoroethane (HFC-143a), and dichlorodifluoromethane (CFC-12). Solvent A is at least one of an amine and a fluorinated ether.

[0008] Item 2. The manufacturing method as described in Item 1 above, further comprising: distilling the composition containing the above-mentioned component X and the above-mentioned solvent A obtained from the bottom of the extraction distillation column after the above-mentioned extraction distillation process, and a distillation process to separate the above-mentioned component X and the above-mentioned solvent A.

[0009] Item 3. The manufacturing method as described in Item 1 or 2 above, wherein the above-described extraction distillation process is carried out at a pressure of 0.05 to 5 MPaG (gauge pressure) using a first distillation column for performing the above-described extraction distillation process.

[0010] Item 4. The manufacturing method as described in Item 2 or 3 above, wherein the distillation process using a second distillation column for performing the distillation process is carried out at a pressure of 0.05 to 3 MPaG (gauge pressure).

[0011] Item 5. The manufacturing method as described in any one of items 1 to 4 above, further comprising: a solvent recovery step of recovering the solvent A used in the extraction distillation step and recycling the recovered solvent A in the extraction distillation step.

[0012] Item 6. The manufacturing method according to any one of items 1 to 5 above, wherein the amine is derived from the general formula: NR 1 R 2 R 3 express, Formula NR 1 R 2 R 3 In the middle, R 1 R 2 and R 3 "Same" or "different" refers to hydrogen or a hydrocarbon group having 1 to 3 carbon atoms that may have substituents, excluding R. 1 R 2 and R 3 The case where all the molecules are hydrogen.

[0013] Item 7. The manufacturing method according to any one of items 1 to 6 above, wherein the amine is selected from at least one of monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, mono-n-propylamine, di-n-propylamine, tri-n-propylamine, monoisopropylamine, and diisopropylamine.

[0014] Item 8. The manufacturing method as described in any one of items 1 to 7 above, wherein the fluorinated ether is produced by general formula R 4 -OR 5 express, Formula R 4 -OR 5 In the middle, R 4 and R 5 Same or different, indicating C n H m Fl Where n is an integer from 1 to 20, m + l = 2n + 1, and m and l are integers greater than or equal to 0.

[0015] Item 9. The manufacturing method according to any one of items 1 to 8 above, wherein the fluorinated ether is at least one selected from 1,1,1,2,2,3,3,4,4-nonafluoro-4-methoxybutane (HFE-7100), 1,1,1,2,2,3,3,4,4-nonafluoro-4-ethoxybutane (HFE-7200), and 1,1,1,2,2,3,4,5,5,5-decafluoro-3-methoxy-4-(trifluoromethyl)pentane (HFE-7300).

[0016] Item 10. A composition containing three components: difluoromethane (HFC-32), component X, and substance A, wherein the total concentration of the three components is 99.5% by mass or more relative to the total composition. The aforementioned component X is at least one selected from pentafluoroethane (HFC-125), 1,1,1-trifluoroethane (HFC-143a), and dichlorodifluoromethane (CFC-12). Substance A is at least one of an amine and a fluorinated ether, and The content of the above-mentioned component X is more than 0% by mass and less than 0.4% by mass relative to the whole composition, and the content of the above-mentioned substance A is more than 0% by mass and less than 0.1% by mass relative to the whole composition.

[0017] Item 11. A composition containing difluoromethane (HFC-32) and substance A, wherein the total concentration of the two components is 99.5% by mass or more relative to the total composition. Substance A is at least one of an amine and a fluorinated ether, and The content of substance A is greater than 0% by mass and less than 0.1% by mass relative to the total composition.

[0018] Item 12. A composition comprising difluoromethane (HFC-32) and component X, wherein the total concentration of the two components is 99.5% by mass or more relative to the total composition. The aforementioned component X is at least one selected from pentafluoroethane (HFC-125), 1,1,1-trifluoroethane (HFC-143a), and dichlorodifluoromethane (CFC-12), and... The content of the above-mentioned component X is more than 0% by mass and less than 0.4% by mass relative to the total composition.

[0019] Item 13. A method for producing purified HFC-32, comprising: contacting a composition containing difluoromethane (HFC-32) and component X with solvent A to obtain an extractive distillation step from which component X is reduced. The aforementioned component X is at least one selected from pentafluoroethane (HFC-125), 1,1,1-trifluoroethane (HFC-143a), and dichlorodifluoromethane (CFC-12). Solvent A is at least one of amine and fluorinated ether. The above-mentioned extraction distillation process is carried out using a first distillation column for the above-mentioned extraction distillation process at a pressure of 0.05 to 5 MPaG (gauge pressure). The distillation process described above is carried out using a second distillation column for performing the distillation process at a pressure of 0.05 to 3 MPaG (gauge pressure). The aforementioned amine is selected from at least one of monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, mono-n-propylamine, di-n-propylamine, tri-n-propylamine, monoisopropylamine, and diisopropylamine. The aforementioned fluorinated ether is selected from at least one of 1,1,1,2,2,3,3,4,4-nonafluoro-4-methoxybutane (HFE-7100), 1,1,1,2,2,3,3,4,4-nonafluoro-4-ethoxybutane (HFE-7200), and 1,1,1,2,2,3,4,5,5,5-decafluoro-3-methoxy-4-(trifluoromethyl)pentane (HFE-7300).

[0020] Invention Effects According to the present invention, HFC-32 can be purified efficiently. Attached Figure Description

[0021] Figure 1 This is a schematic diagram illustrating the process of manufacturing purified HFC-32 according to the present invention. In the diagram, HFC-125, HFC-143a, and CFC-12 constituting component X refer to the presence of at least one of these three components. Detailed Implementation

[0022] After conducting in-depth research, the inventors of this invention discovered that HFC-32 can be efficiently purified by a manufacturing method including the following extraction distillation step, wherein the extraction distillation step involves contacting a composition containing HFC-32 and at least one of pentafluoroethane (HFC-125), 1,1,1-trifluoroethane (HFC-143a), and dichlorodifluoromethane (CFC-12) (component X) with a specific solvent to obtain a composition in which component X is reduced from the above composition.

[0023] This invention is based on this discovery and the results of further repeated research.

[0024] In this specification, the numerical range indicated by “~” means the range including the values ​​recorded before and after “~” as the lower and upper limits (i.e., “above” and “below”).

[0025] In this specification, an azeotropic composition refers to a composition in which the liquid and gas phases are indistinguishable under certain pressure, and the composition behaves like a single substance.

[0026] In this specification, an azeotropic-like composition refers to a composition that has a composition similar to an azeotropic composition and exhibits behavior similar to that of an azeotropic composition. An azeotropic-like composition can be distilled and / or refluxed substantially without change in composition. Therefore, an azeotropic-like composition can be treated substantially the same as an azeotropic composition. Furthermore, as a characteristic of an azeotropic-like composition, an example is that the pressure difference between the boiling point curve and the dew point curve in the pressure-composition diagram is within 5%.

[0027] In this specification, the standard boiling point refers to the boiling point at standard atmospheric pressure of 1013.25 hPa.

[0028] In this specification, gauge pressure refers to relative pressure based on atmospheric pressure, which is the pressure difference between absolute pressure and atmospheric pressure. In this specification, gauge pressure is indicated by "G", such as MPaG. On the other hand, pressure without "G" indicates absolute pressure.

[0029] In this specification, the “purity” of a refrigerant refers to the percentage of components (mol% or mass%) obtained by quantitative analysis using gas chromatography.

[0030] In this specification, the main component refers to a component that preferably contains 85 mol% to 99.9 mol%, more preferably 90 mol% to 99.9 mol%, further preferably 95 mol% to 99.9 mol%, and particularly preferably 99 mol% to 99.9 mol%.

[0031] In this specification, extractive distillation refers to the distillation operation in which an extraction solvent is added to a mixture of two or three components with very similar standard boiling points and relative volatility (specific volatility) close to 1, or a mixture of components with azeotropic compositions, which are difficult to separate by ordinary distillation, to prepare an extraction mixture. This process facilitates separation by reducing the relative volatility of the initial two or three components to a value far below 1. Specifically, components with a relative volatility of 1 cannot be separated by distillation.

[0032] In this specification, the relative volatility (α) is defined as the mole fraction of liquid component A when the composition containing at least target component A and target component B is in vapor-liquid equilibrium. A Let the mole fraction of liquid phase component B be x. B Let the mole fraction of the gas phase component A, which is in equilibrium with the liquid phase, be y. A And let the mole fraction of gas phase component B be y. B In this case, the relative volatility of component A relative to component B is defined as: α A→B = (y A / x A ) / (y B / x B ).

[0033] In this specification, when component A is designated as HFC-32 and component B as HFC-125, the relative volatility of component A relative to component B, i.e., the "relative volatility of HFC-32 relative to HFC-125", is denoted as α. 32→125 .

[0034] The present invention includes the following embodiments.

[0035] The manufacturing method of the present invention is a method for manufacturing purified HFC-32, which includes: The composition containing difluoromethane (HFC-32) and component X is contacted with solvent A to obtain an extraction distillation process in which component X is reduced from the above composition. The aforementioned component X is at least one selected from pentafluoroethane (HFC-125), 1,1,1-trifluoroethane (HFC-143a), and dichlorodifluoromethane (CFC-12). Solvent A is at least one of an amine and a fluorinated ether.

[0036] In the extractive distillation process, especially when the composition containing HFC-32 and component X (also referred to as the "extractive distillation composition" or "raw material composition") is an azeotropic or azeotropic-like composition, the manufacturing method of the present invention is preferred. Specifically, HFC-125, HFC-143a, and CFC-12, as component X, can all be azeotropic or azeotropic-like compositions when mixed with HFC-32. In recent years, due to the promotion of the recovery of used refrigerants (especially mixed refrigerants) and the recycling of specific components, in the present invention, used HFC-410A (a mixed refrigerant of HFC-32 and HFC-125) can be used as the extractive distillation composition (raw material composition), for example.

[0037] (Extraction and distillation process) The extraction distillation step in the manufacturing method of the present invention involves contacting a composition (extraction distillation composition) containing component X (at least one selected from HFC-125, HFC-143a, and CFC-12) and HFC-32 with solvent A (at least one selected from amine and fluorinated ether) to obtain a composition in which component X is reduced. In other words, the extraction distillation step involves extracting and distilling a composition (extraction distillation composition) containing component X and HFC-32 in the presence of solvent A to obtain a composition in which component X is reduced. Furthermore, in the present invention, "reduction" in the extraction distillation step refers to reducing the proportion of a specific compound (component X) in the extraction distillation composition.

[0038] The above-mentioned extractive distillation composition contains, preferably, 99.5% by mass or more, more preferably 99.7% by mass or more, even more preferably 99.8% by mass or more, and even more preferably 99.9% by mass or more, in total concentration. As the above-mentioned extractive distillation composition, for example, when the main component of component X is HFC-125, it is possible to use a composition (especially an azeotropic composition or a near-azeotropic composition) that contains HFC-125 and HFC-32 in the above-mentioned total concentration after recovering used HFC-410A and removing easily separable byproducts through a separation process (any distillation process, etc.) as needed.

[0039] Additionally, from the same source ·HFC-407A (HFC-32+HFC-125+HFC-134a) ·HFC-407B (HFC-32+HFC-125+HFC-134a) ·HFC-407C (HFC-32+HFC-125+HFC-134a) ·HFC-407D (HFC-32+HFC-125+HFC-134a) ·HFC-407E (HFC-32+HFC-125+HFC-134a) ·HFC-407F (HFC-32+HFC-125+HFC-134a) ·HFC-407H (HFC-32+HFC-125+HFC-134a) ·HFC-407I (HFC-32+HFC-125+HFC-134a) ·HFC-410B (HFC-32+HFC-125) ·HFC-425A (HFC-32+HFC-134a+HFC-227ea) ·HFC-427A (HFC-32+HFC-125+HFC-134a+HFC-143a) ·R-438A (HFC-32+HFC-125+HFC-134a+R-600+R601a) ·R-439A (HFC-32+HFC-125+R600a) ·R-442A (HFC-32+HFC-125+HFC-134a+HFC-152a+HFC-227ea) ·R-444A (HFC-32+HFC-152a+HFO-1234ze(E)) ·R-448A (HFC-32+HFC-125+HFC-134a+HFO-1234ze(E)+HFO-1234yf) ·R-449A (HFC-32+HFC-125+HFC-134a+HFO-1234yf) ·R-452A (HFC-32+HFC-125+HFO-1234yf) ·HFC-458A (HFC-32+HFC-125+HFC-134a+HFC-227ea+HFC-236fa) ·R-463A (R-744+HFC-32+HFC-125+HFO-1234yf+HFC-134a) ·R-466A (HFC-32+HFC-125+CF3I) ·R-504 (HFC-32+HCFC-115) Used recycled materials containing one or more components of X and HFC-32 as constituent components can be used as extract distillation compositions through any distillation process.

[0040] The above-mentioned extractive distillation composition preferably consists only of HFC-32 and component X, but depending on the conditions of the preparation process of the above-mentioned extractive distillation composition, the presence of unavoidable impurities is permissible. Furthermore, the statement above, "the extractive distillation composition contains preferably 99.5% by mass or more of component X and HFC-32 in total concentration," means that the extractive distillation composition substantially consists only of HFC-32 and component X, or that even if other components are present, they are merely unavoidable impurities.

[0041] HFC-125 (standard boiling point: -48.1℃) and HFC-32 (standard boiling point: -51.7℃), as components X, exhibit azeotropic or azeotropic-like behavior. The azeotropic or azeotropic composition of HFC-125 and HFC-32 has a boiling point that is lower than the boiling point of either HFC-125 or HFC-32 (the azeotropic composition at 0.1013 MPa is HFC-32 / HFC-125 = 87.8 / 12.2 (mol%), at a temperature of -51.8℃). In addition, HFC-143a (standard boiling point: -47.3℃) and HFC-32 (standard boiling point: -51.7℃), which are components X, exhibit azeotropic or azeotropic-like behavior. The azeotropic or azeotropic-like composition of HFC-143a and HFC-32 has a boiling point that is lower than the boiling point of either HFC-143a or HFC-32 (the azeotropic composition at 0.1013 MPa is HFC-32 / HFC-143a = 77.8 / 22.2 (mol%), at a temperature of -52.5℃). Furthermore, CFC-12 (standard boiling point: -29.8°C) and HFC-32 (standard boiling point: -51.7°C), which are components X, exhibit azeotropic or azeotropic-like behavior. The azeotropic or azeotropic-like composition of CFC-12 and HFC-32 has a boiling point lower than that of either CFC-12 or HFC-32 (the azeotropic composition at 0.1013 MPa is HFC-32 / CFC-12 = 96.5 / 3.5 (mol%), at a temperature of -51.7°C). The composition of the extractive distillation composition supplied to the above-mentioned extractive distillation process is preferably 50.0% to 99.999% or less based on the molar ratio of HFC-32, more preferably 70.0% to 99.999% or less. Furthermore, the composition of the HFC-32-based composition obtained by extraction distillation is preferably 99.500% or more, more preferably 99.900% or more, and even more preferably 99.999% or more, based on the molar ratio of HFC-32.

[0042] The above-mentioned extraction distillation process is preferably carried out by contacting the above-mentioned extraction distillation composition with solvent A to obtain a composition containing HFC-32 but substantially free of component X.

[0043] In this specification, "substantially free of component X" means that the content of component X in the composition obtained by the above-described extraction and distillation process (the total amount of component X if it contains two or more of HFC-125, HFC-143a, and CFC-12) is preferably less than 1% by mass, more preferably less than 0.5% by mass, and particularly preferably less than 0.1% by mass.

[0044] In the above-described extractive distillation process, solvent A, consisting of at least one of an amine and a fluorinated ether, is used as the extraction solvent. The extraction solvent in this invention preferably consists of only at least one of an amine and a fluorinated ether, but unavoidable impurities are permissible to the extent that they do not affect the extractive distillation process. Hereinafter, solvent A will also be referred to simply as the extraction solvent of this invention.

[0045] The amines mentioned above can be any liquid amine that serves as an extraction solvent, preferably of the general formula: NR 1 R 2 R 3 The amine shown.

[0046] Formula NR 1 R 2 R 3 In the middle, R 1 R 2 and R 3 "Same" or "different" indicates hydrogen or a hydrocarbon group with 1 to 3 carbon atoms that may have substituents. However, it does not include R. 1 R 2 and R 3 The case where all the molecules are hydrogen.

[0047] In addition, the above-mentioned amine preferably has a standard boiling point of -10 to 160°C.

[0048] The amines described above are preferably selected from at least one of monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, mono-n-propylamine, di-n-propylamine, tri-n-propylamine, monoisopropylamine, and diisopropylamine. Among these amines, at least one of diethylamine and triethylamine is more preferred, as the operating conditions of the distillation column can be easily adjusted to easily operable pressure and temperature. The CAS numbers and standard boiling points of these amines are shown in Table 1 below.

[0049] [Table 1] These amines can be used alone or in combination of two or more.

[0050] The aforementioned fluorinated ethers can be any fluorinated ether that serves as an extraction solvent, preferably those of the general formula R. 4 -OR 5 The fluorinated ether shown. Formula R 4 -OR 5 In the middle, R 4 and R 5 Same or different, indicating C n H m F l , where n is an integer from 1 to 20, m + l = 2n + 1, and m and l are integers greater than or equal to 0.

[0051] As the aforementioned fluorinated ether, at least one is preferably selected from 1,1,1,2,2,3,3,4,4-nonafluoro-4-methoxybutane (HFE-7100), 1,1,1,2,2,3,3,4,4-nonafluoro-4-ethoxybutane (HFE-7200), and 1,1,1,2,2,3,4,5,5,5-decafluoro-3-methoxy-4-(trifluoromethyl)pentane (HFE-7300). From the viewpoint of operability, operating temperature, etc., at least one selected from HFE-7100, HFE-7200, and HFE-7300 is particularly preferred among these fluorinated ethers. The CAS numbers and standard boiling points of these fluorinated ethers are shown in Table 2 below.

[0052] [Table 2] HFE-7100 and HFE-7200 are both two-component mixtures, so the Cas numbers of the two components are recorded together.

[0053] These fluorinated ethers can be used alone or in combination of two or more.

[0054] The mixing ratio of the amine and the fluorinated ether in solvent A is not limited; it can be either the amine alone, the fluorinated ether alone, or a mixture of the two in any proportion.

[0055] Regarding the temperature range of the standard boiling point in the above-mentioned extractive distillation process, the temperature difference between the extraction solvent and the compound to be separated in the extractive distillation process only needs to be sufficient to allow separation by single distillation, stripping, etc., typically a temperature difference of 20°C or more. However, if the standard boiling point is too high, the extraction solvent itself may decompose. Therefore, from the viewpoint of efficiently performing extractive distillation, the standard boiling point of the extraction solvent is preferably 30–135°C, more preferably 35–120°C, even more preferably 40–100°C, and particularly preferably 50–90°C.

[0056] The amount of extraction solvent used in the above-mentioned extraction distillation process is preferably 1 molar equivalent or more and 30 molar equivalents or less relative to the extraction distillation composition supplied to the extraction distillation column, more preferably 5 molar equivalents or more and 25 molar equivalents or less.

[0057] The concentration of component X in the extraction distillation composition used in the above-mentioned extraction distillation process is preferably 50 mol% or less, more preferably 30 mol% or less, and even more preferably 10 mol% or less.

[0058] The theoretical plate number of the extractive distillation column used in the above-described extractive distillation process is preferably 10 or more, more preferably 20 or more. Furthermore, from an economic point of view, the theoretical plate number of the extractive distillation column used in the above-described extractive distillation process is preferably 100 or less, more preferably 70 or less.

[0059] In the above-described extractive distillation process, it is preferable to supply the extraction solvent to the upper section of the extractive distillation column. Furthermore, the extraction solvent used in the above-described extractive distillation process is preferably an extraction solvent that has been recovered and recycled in the extraction solvent recovery process described later.

[0060] In the above-described extraction distillation process, the pressure for extraction distillation (pressure of the first distillation column) is preferably 0.05–5 MPaG (gauge pressure). The lower limit of the pressure is preferably 0.05 MPaG, more preferably 0.1 MPaG, further preferably 0.25 MPaG, and particularly preferably 0.5 MPaG. The upper limit of the pressure is preferably 5 MPaG, more preferably 4 MPaG, further preferably 3 MPaG, and particularly preferably 2 MPaG.

[0061] The above-described extraction and distillation process can be carried out in a discontinuous or continuous manner; from an industrial point of view, continuous operation is preferred. Furthermore, by repeating the extraction and distillation, the purity of the distillate components can be achieved.

[0062] In the above-described extractive distillation process, when HFC-32 is distilled off from the extractive distillation composition, when adding the extraction solvent, it is preferable to use an extraction solvent in which the relative volatility (specific volatility) of HFC-32 relative to component X is 1.70 or higher, preferably 2.00 or higher. This increases the vapor mole fraction of HFC-32, resulting in an increase in HFC-32 in the vapor phase. Consequently, HFC-32 can be separated from the top of the extractive distillation column, and the extraction solvent and component X can be obtained from the bottom of the extractive distillation column.

[0063] (Extraction solvent recovery process) The manufacturing method of the present invention preferably includes an extraction solvent recovery step, which involves recovering the extraction solvent used in the above-mentioned extraction distillation process and recycling the recovered extraction solvent in the above-mentioned extraction distillation process.

[0064] The aforementioned extraction solvent recovery process includes distilling the composition containing the aforementioned component X and the aforementioned solvent A obtained from the bottom of the extraction distillation column after the aforementioned extraction distillation process, and a distillation process that separates the aforementioned component X and the aforementioned solvent A (hereinafter also referred to as the "distillation process"). This process can be implemented by recovering the extraction solvent from the composition containing the aforementioned solvent A and recycling it in the extraction distillation process. Furthermore, the distillation process that separates the aforementioned component X and the aforementioned solvent A is preferably a distillation process that separates the composition containing component X as the main component and the composition containing the extraction solvent as the main component.

[0065] The solvent recovery column (second distillation column) used in the above distillation process preferably has 5 or more theoretical plates, more preferably 10 or more. Furthermore, from an economic point of view, the solvent recovery column preferably has 40 or fewer theoretical plates, more preferably 30 or fewer.

[0066] In the above distillation process, the pressure for distillation is preferably 0.05 to 3 MPaG (gauge pressure). The lower limit of the pressure is preferably 0.05 MPaG, more preferably 0.1 MPaG. The upper limit of the pressure is preferably 3 MPaG, more preferably 2.5 MPaG.

[0067] Through the above distillation process, a composition containing component X as the main component can be separated from the top of the solvent recovery tower, and a composition containing the extraction solvent as the main component can be obtained from the bottom of the solvent recovery tower.

[0068] The aforementioned extraction solvent recovery process can be implemented by recovering the extraction solvent from the composition containing the extraction solvent as the main component obtained from the bottom of the distillation column in the aforementioned distillation process, and recycling it in the extractive distillation process. Furthermore, before recycling the extraction solvent recovered from the bottom of the column in the extractive distillation process, it can also be further subjected to any separation process, such as rectification, to remove impurities, as needed.

[0069] The distillation process described above can be carried out in a discontinuous or continuous manner, but from an industrial point of view, continuous operation is preferred.

[0070] The manufacturing method of the present invention preferably includes an extraction distillation step and an extraction solvent recovery step, and more preferably consists of any prior distillation step for improving the purity of the composition for extraction distillation, an extraction distillation step, and an extraction solvent recovery step.

[0071] (A composition containing HFC-32, component X and substance A (refrigerant 1)) This invention comprises a composition containing difluoromethane (HFC-32), component X, and substance A (hereinafter also referred to as "refrigerant 1"). Component X is the same as the item described in the extraction distillation step above, and is at least one selected from pentafluoroethane (HFC-125), 1,1,1-trifluoroethane (HFC-143a), and dichlorodifluoromethane (CFC-12). Furthermore, substance A is the same as the solvent A described in the extraction distillation step above, and is at least one selected from amines and fluorinated ethers.

[0072] Refrigerant 1 is a composition containing three components: HFC-32, component X, and substance A. The total concentration of these three components is 99.5% by mass or more relative to the entire composition, and the content of component X is more than 0% by mass and less than 0.4% by mass relative to the entire composition, while the content of substance A is more than 0% by mass and less than 0.1% by mass relative to the entire composition. Furthermore, refrigerant 1 is a composition in which component X and the extraction solvent (solvent A) remain in trace amounts in the purified HFC-32-containing composition finally obtained in the manufacturing method of the present invention. The description of "more than 0% by mass" can also be written as "more than 0.01% by mass".

[0073] The total concentration of the three components in refrigerant 1 is preferably 99.7% by mass or more, more preferably 99.8% by mass or more, and even more preferably 99.9% by mass or more, relative to the overall composition.

[0074] Refrigerant 1 is particularly preferably composed of only HFC-32, component X and substance A, but unavoidable impurities are permissible.

[0075] The application of refrigerant 1 is not limited; for example, it can be used as a refrigerant for air conditioning, a heat transfer medium, or a refrigerant for automotive air conditioning.

[0076] (A composition containing HFC-32 and component X (refrigerant 2)) This invention comprises a composition containing difluoromethane (HFC-32) and component X (hereinafter also referred to as "refrigerant 2"). Component X is the same as described above.

[0077] Refrigerant 2 is a composition containing HFC-32 and component X, wherein the total concentration of the two components is 99.5% by mass or more relative to the entire composition, and the content of component X is more than 0% by mass and less than 0.4% by mass relative to the entire composition. Furthermore, refrigerant 2 is a composition in which component X remains in trace amounts in the purified HFC-32-containing composition finally obtained in the manufacturing method of the present invention. The description of more than 0% by mass can also be written as 0.01% by mass or more.

[0078] The total concentration of the two components in refrigerant 2 is preferably 99.7% by mass or more, more preferably 99.8% by mass or more, and even more preferably 99.9% by mass or more, relative to the entire composition.

[0079] Refrigerant 2 is particularly preferably composed of only HFC-32 and component X, but unavoidable impurities are permissible.

[0080] The application of refrigerant 2 is not limited; for example, it can be used as a refrigerant for air conditioning, a heat transfer medium, or a refrigerant for automotive air conditioning.

[0081] (The purified composition containing HFC-32) In this invention, the purified composition containing HFC-32 comprises a composition containing HFC-32 and substance A (hereinafter also referred to as "Composition 1"). The type of substance A is the same as described above.

[0082] Composition 1 is a composition containing HFC-32 and substance A, wherein the total concentration of the two components is 99.5% by mass or more relative to the entire composition, and the content of substance A is more than 0% by mass and less than 0.1% by mass relative to the entire composition. Furthermore, Composition 1 is a composition in which trace amounts of the extraction solvent (solvent A) remain in the purified HFC-32-containing composition finally obtained in the manufacturing method of the present invention. The description of more than 0% by mass can also be written as 0.01% by mass or more.

[0083] The total concentration of the two components in composition 1 is preferably 99.7% by mass or more, more preferably 99.8% by mass or more, and even more preferably 99.9% by mass or more relative to composition 1.

[0084] Composition 1 is particularly preferably composed of only HFC-32 and substance A, allowing for the presence of unavoidable impurities.

[0085] The use of composition 1 is not limited, for example, it can be used as a leak detector, stabilizer, tracer, etc. when using refrigerants.

[0086] Example The following embodiments are described in detail to illustrate the present invention. However, the present invention is not limited to these embodiments.

[0087] In the embodiments, the concentrations of various components such as HFC-32 were measured using the following measuring apparatus and measuring conditions.

[0088] Measurement apparatus: Gas chromatography (using an FID detector) Methods for calculating the concentration of each component: • The concentration of HFC-32 = the number of moles of HFC-32 / (the number of moles of HFC-32 + the number of moles of component X) • Concentration of component X = Number of moles of component X / (Number of moles of HFC-32 + Number of moles of component X) Examples 1-5 and Comparative Examples 1-14 For a composition containing 70 mol% HFC-32 and 30 mol% HFC-125, an additional 6 mol of each solvent was added relative to the above composition, and the relative volatility α of HFC-32 relative to HFC-125 at 5°C was measured. 32→125.

[0089] In Example 1, diethylamine was used as a solvent, with a relative volatility α. 32→125 The value is 2.53. In Example 2, triethylamine was used as the solvent, with a relative volatility α. 32→125 The value is 2.08. In Example 3, HFE-7300 was used as the solvent, with a relative volatility α. 32→125 The value is 2.00. In Example 4, HFE-7200 was used as the solvent, with a relative volatility α. 32→125 The value is 1.77. In Example 5, HFE-7100 was used as the solvent, with a relative volatility α. 32→125 The value is 1.73. In Comparative Example 1, isopropanol (IPA) was used as the solvent, and the relative volatility α was 1.73. 32→125 The value was 1.66. In Comparative Example 2, tetrahydrofuran (THF) was used as the solvent, and the relative volatility α was... 32→125 The value was 1.49. In Comparative Example 3, ethanol was used as the solvent, and the relative volatility α was... 32→125 The value was 1.48. In Comparative Example 4, 2-butanol was used as the solvent, and the relative volatility α was... 32→125 The value was 1.43. In Comparative Example 5, methyl ethyl ketone (MEK) was used as the solvent, and the relative volatility α was... 32→125 The value was 1.43. In Comparative Example 6, n-propanol was used as the solvent, and the relative volatility α was... 32→125 The value is 1.40. In Comparative Example 7, ethyl acetate was used as the solvent, and the relative volatility α was... 32→125 The value was 1.40. In Comparative Example 8, isobutanol was used as the solvent, and the relative volatility α was... 32→125 The value was 1.32. In Comparative Example 9, methanol was used as the solvent, and the relative volatility α was... 32→125 The value was 1.26. In Comparative Example 10, acetone was used as a solvent, and the relative volatility α was... 32→125 The value is 1.24. In Comparative Example 11, hexane was used as the solvent, and the relative volatility α was... 32→125 The value was 1.18. In Comparative Example 12, 5-fluoropropanol was used as the solvent, and the relative volatility α was... 32→125 The value was 0.92. In Comparative Example 13, trifluoroethanol was used as the solvent, and the relative volatility α was... 32→125 The value is 0.74. In Comparative Example 14, acetonitrile was used as a solvent, and the relative volatility α was... 32→125 It is 0.69.

[0090] The results are summarized in Table 3 below.

[0091] [Table 3] The results above show that amines such as diethylamine and triethylamine, as well as fluorinated ethers such as HFE-7300, HFE-7200, and HFE-7100, are effective extraction solvents.

[0092] Furthermore, it is known that the relative volatility α of HFC-32 relative to HFC-143a at 5°C for each solvent used in Examples 1-5 is [not specified]. 32→143a And the relative volatility α of HFC-32 relative to CFC-12 at 5°C. 32→12 All values ​​are above 1.70, which is effective not only for the separation of HFC-32 and HFC-125 by extractive distillation, but also for the separation of HFC-32 and HFC-143a and / or CFC-12 by extractive distillation.

[0093] Example 6 according to Figure 1 The flowchart shown illustrates the process of producing purified HFC-32 using an extractive distillation composition containing HFC-32 and component X (HFC-125) as raw material, and HFE-7100 as the extraction solvent, through a process consisting of an extractive distillation step and an extraction solvent recovery step.

[0094] (Extraction and distillation process) The extractive distillation composition was supplied to the extractive distillation column from the 45th section above the top of the column, which had 70 theoretical plates, at a flow rate of 956 mol / hr. The extraction solvent (HFE-7100) was supplied from the 3rd section of the extractive distillation column at a flow rate of 9650 mol / hr. The operating pressure of the extractive distillation column was 0.5 MPaG, and the top temperature was -10°C.

[0095] (Extraction solvent recovery process) The bottom liquid drawn from the bottom of the extractive distillation column is fed into the fifth section above the top of an extraction solvent recovery column (hereinafter referred to as the "solvent recovery column") with 15 theoretical plates, and HFC-125 is recovered from the top of the column with a purity of 99.99%. The solvent recovery column operates at a pressure of 0.4 MPaG and a top temperature of -9°C.

[0096] In addition, the bottom liquid containing HFE-7100 drawn from the bottom of the recovery tower (HFE-7100 flow rate: 144 mol / hr) is recycled in the extraction distillation process.

[0097] pass Figure 1Material balances for Example 6 of the process: In F1, HFC-32 was 667.1 mol / hr, HFC-125 was 289.1 mol / hr, and HFE-7100 (extraction solvent) was 9650.6 mol / hr. In F2, HFC-32 was 6.7 mol / hr, HFC-125 was 289.1 mol / hr, and HFE-7100 (extraction solvent) was 9650.2 mol / hr. In F3, HFC-32 was 660.4 mol / hr, HFC-125 was 0.0014 mol / hr, and HFE-7100 (extraction solvent) was trace (below 0.1 ppm). In F4, HFC-32 was trace (below 0.1 ppm), HFC-125 was 0.005 mol / hr, and HFE-7100 (extraction solvent) was 9650.6 mol / hr. In F5, HFC-32 was 6.7 mol / hr, HFC-125 was 289.1 mol / hr, and HFE-7100 (extraction solvent) was 0.002 mol / hr. Table 4 below shows the details of the content of these three components at each position of F1, F2, F3, F4, and F5 in the process of Example 6 (the total content of the three components is 100 mol%).

[0098] [Table 4] In the amines shown in Examples 1-2 and the fluorinated ethers shown in Examples 3-5, the relative volatility α of HFC-32 relative to component X (HFC-125, HFC-143a, CFC-12) is... 32→成分X All values ​​are above 1.70, which is higher than those of the comparative examples (below 1.69), ensuring a relatively high concentration of HFC-32 in the gas phase. Therefore, the separation efficiency is higher than that of the comparative examples. Thus, the process of the present invention, which uses at least one extraction solvent (solvent A) from amines and fluorinated ethers in the extraction distillation step, is very effective in the separation of component X and HFC-32.

[0099] Symbol Explanation 1: Extraction distillation tower; 2: Solvent recovery tower.

Claims

1. A method for manufacturing purified HFC-32, characterized in that, include: The composition containing difluoromethane (HFC-32) and component X is contacted with solvent A to obtain an extractive distillation process in which the composition reduces the content of component X. The component X is selected from at least one of pentafluoroethane (HFC-125), 1,1,1-trifluoroethane (HFC-143a), and dichlorodifluoromethane (CFC-12). Solvent A is at least one of amine and fluorinated ether.

2. The manufacturing method as described in claim 1, characterized in that, Also includes: The composition containing component X and solvent A obtained from the bottom of the extraction distillation column after the extraction distillation process is distilled, and the distillation process separates component X and solvent A.

3. The manufacturing method as described in claim 1 or 2, characterized in that: The extractive distillation process is carried out using a first distillation column for the extractive distillation process at a pressure of 0.05 to 5 MPaG on a gauge.

4. The manufacturing method as described in claim 2 or 3, characterized in that: The distillation process is carried out using a second distillation column for performing the distillation process at a pressure of 0.05 to 3 MPaG on a gauge.

5. The manufacturing method according to any one of claims 1 to 4, characterized in that, Also includes: A solvent recovery process is performed to recover solvent A used in the extraction distillation process and to recycle the recovered solvent A in the extraction distillation process.

6. The manufacturing method according to any one of claims 1 to 5, characterized in that: The amine is of the general formula: NR 1 R 2 R 3 express, In the formula, R 1 R 2 and R 3 The same or different denotes hydrogen or hydrocarbon groups having 1 to 3 carbon atoms that may have substituents, excluding R. 1 R 2 and R 3 The case where all molecules are hydrogen.

7. The manufacturing method according to any one of claims 1 to 6, characterized in that: The amine is selected from at least one of monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, mono-n-propylamine, di-n-propylamine, tri-n-propylamine, monoisopropylamine, and diisopropylamine.

8. The manufacturing method according to any one of claims 1 to 7, characterized in that: The fluorinated ether is of general formula R 4 -OR 5 express, In the formula, R 4 and R 5 Representing C in the same or different ways n H m F l , where n is an integer from 1 to 20, m + l = 2n + 1, and m and l are integers greater than or equal to 0.

9. The manufacturing method according to any one of claims 1 to 8, characterized in that: The fluorinated ether is selected from at least one of 1,1,1,2,2,3,3,4,4-nonafluoro-4-methoxybutane (HFE-7100), 1,1,1,2,2,3,3,4,4-nonafluoro-4-ethoxybutane (HFE-7200), and 1,1,1,2,2,3,4,5,5,5-decafluoro-3-methoxy-4-(trifluoromethyl)pentane (HFE-7300).

10. A composition containing difluoromethane (HFC-32), component X, and substance A, characterized in that: The total concentration of the three components is greater than 99.5% by mass relative to the composition as a whole. The component X is selected from at least one of pentafluoroethane (HFC-125), 1,1,1-trifluoroethane (HFC-143a), and dichlorodifluoromethane (CFC-12). The substance A is at least one of an amine and a fluorinated ether, and, The content of component X is greater than 0% by mass and less than 0.4% by mass relative to the whole composition, and the content of substance A is greater than 0% by mass and less than 0.1% by mass relative to the whole composition.

11. A composition containing difluoromethane (HFC-32) and substance A, characterized in that: The total concentration of the two components is greater than 99.5% by mass relative to the composition as a whole. The substance A is at least one of an amine and a fluorinated ether, and, The content of substance A is greater than 0% by mass and less than 0.1% by mass relative to the total composition.

12. A composition containing difluoromethane (HFC-32) and component X, characterized in that: The total concentration of the two components is greater than 99.5% by mass relative to the composition as a whole. The component X is selected from at least one of pentafluoroethane (HFC-125), 1,1,1-trifluoroethane (HFC-143a), and dichlorodifluoromethane (CFC-12), and, The content of component X is greater than 0% by mass and less than 0.4% by mass relative to the whole composition.

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