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

Abstract

To provide a method for efficiently purifying difluoromethane (HFC-32).SOLUTION: The present disclosure provides a method for producing purified difluoromethane (HFC-32), the method including an extractive distillation step of bringing a composition containing HFC-32 and a component X into contact with a solvent A to obtain a composition where an amount of the component X is reduced from the composition. The component X is at least one selected from the group consisting of pentafluoroethane (HFC-125), 1,1,1-trifluoroethane (HFC-143a), and dichlorodifluoromethane (CFC-12), and the solvent A is at least one of an amine and a fluorinated ether.SELECTED DRAWING: None

Description

[Technical field]

[0001] This disclosure relates to methods for producing purified difluoromethane (HFC-32) and compositions containing HFC-32. [Background technology]

[0002] HFC-32 is useful as a source of refrigerant or mixed refrigerants in combination with other components (eg, HFC-410A, which is a mixed refrigerant of HFC-32 and HFC-125).

[0003] In relation to the present disclosure, for example, Patent Document 1 discloses a method for separating HFC-32 and HFC-125. In detail, it discloses "a method for separating HFC-32 and HFC-125 from a first mixture by using an extractant comprising methylene chloride, comprising the steps of adding said extractant to the first mixture to produce a second mixture, separating HFC-32 and HFC-125 in the second mixture by extractively distilling the second mixture in an extractive distillation zone of a distillation column, and thereby recovering HFC-125 as an overhead product of the column and HFC-32 from the bottom of the column." [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2007-91762 A Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure aims to provide a method for efficiently purifying HFC-32 and compositions containing HFC-32. [Means for solving the problem]

[0006] The present disclosure includes, for example, the aspects described in the following sections. Item 1. The method includes an extractive distillation step of contacting a composition containing difluoromethane (HFC-32) and component X with a solvent A to obtain a composition in which the component X is reduced from the composition; The component X is at least one selected from the group consisting of pentafluoroethane (HFC-125), 1,1,1-trifluoroethane (HFC-143a), and dichlorodifluoromethane (CFC-12); The solvent A is at least one of an amine and a fluorinated ether. A method for producing refined HFC-32. Item 2. The method according to item 1, further comprising a distillation step of distilling a composition containing the component X and the solvent A obtained from the bottom of the extractive distillation column through the extractive distillation step to separate the component X from the solvent A. Item 3. The method according to item 1 or 2, wherein the extractive distillation step using a first distillation column for carrying out the extractive distillation step is carried out under a pressure of 0.05 to 5 MPaG (gauge pressure). Item 4. The method according to item 2 or 3, wherein the distillation step using the second distillation column for carrying out the distillation step is carried out under a pressure of 0.05 to 3 MPaG (gauge pressure). Item 5. The method according to any one of items 1 to 4, further comprising a solvent recovery step of recovering the solvent A used in the extractive distillation step and recycling the recovered solvent A to the extractive distillation step. Item 6. The amine is represented by the general formula: NR 1 R 2 R 3 [In the formula, R 1 , R 2 and R 3 are the same or different and each represents a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms which may have a substituent. 1 , R 2 and R 3 except when all are hydrogen. 6. The method according to any one of items 1 to 5, wherein the compound is represented by the formula: Item 7. The method according to any one of items 1 to 6, wherein the amine is at least one selected from the group consisting of monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, mono-n-propylamine, di-n-propylamine, tri-n-propylamine, mono-isopropylamine, and di-isopropylamine. Item 8. The fluorinated ether is represented by the general formula R 4 -OR 5 [In the formula, R 4 and R 5 C n H m F l Here, n is an integer of 1 to 20, m+l=2n+1, and m and l are integers of 0 or more. 8. The method according to any one of items 1 to 7, wherein the compound is represented by the formula: Item 9. The method according to any one of items 1 to 8, wherein the fluorinated ether is at least one selected from the group consisting 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). Item 10. A composition containing difluoromethane (HFC-32), component X, and substance A, wherein the total concentration of the three components is 99.5% by mass or more based on the entire composition; The component X is at least one selected from the group consisting 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 the component X is more than 0 mass% and 0.4 mass% or less with respect to the entire composition, and the content of the substance A is more than 0 mass% and 0.1 mass% or less with respect to the entire composition. composition. 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 based on the entire composition; The substance A is at least one of an amine and a fluorinated ether; and The content of the substance A is more than 0% by mass and 0.1% by mass or less with respect to the entire composition. composition. Item 12. A composition containing difluoromethane (HFC-32) and component X, wherein the total concentration of the two components is 99.5% by mass or more based on the entire composition; The component X is at least one selected from the group consisting of pentafluoroethane (HFC-125), 1,1,1-trifluoroethane (HFC-143a), and dichlorodifluoromethane (CFC-12); and The content of the component X is more than 0% by mass and 0.4% by mass or less with respect to the entire composition. composition. Effect of the Invention

[0007] According to the present disclosure, it is possible to efficiently purify HFC-32. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram showing an outline of the process for producing purified HFC-32 in the present disclosure, in which HFC-125, HFC-143a, and CFC-12 constituting component X mean that at least one of the three components is contained. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] As a result of intensive research, the present inventors have found that HFC-32 can be efficiently purified by a production method including an extractive distillation step of contacting a composition containing HFC-32 and at least one member (component X) selected from the group consisting of pentafluoroethane (HFC-125), 1,1,1-trifluoroethane (HFC-143a), and dichlorodifluoromethane (CFC-12), with a specific solvent, and obtaining a composition in which the content of component X has been reduced from the composition.

[0010] The present disclosure was completed as a result of further research based on this knowledge.

[0011] In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits (i.e., "greater than or equal to, less than or equal to").

[0012] In this specification, an azeotropic composition means a composition that has no difference between the compositions of the liquid phase and the vapor phase under a constant pressure and behaves as if it were a single substance.

[0013] In this specification, the term "azeotrope-like composition" refers to a composition that can form an azeotropic composition and has a composition that is close to the azeotropic composition and exhibits behavior similar to that of an azeotropic composition. An azeotrope-like composition can be distilled and / or refluxed with little change in composition. Therefore, an azeotrope-like composition can be handled almost equally to an azeotropic composition. One characteristic of an azeotrope-like composition is that the difference in pressure between the boiling point curve and the dew point curve in a pressure-composition diagram is within 5%.

[0014] In this specification, the normal boiling point means the boiling point at a standard atmospheric pressure of 1013.25 hPa.

[0015] In this specification, the gauge pressure is a relative pressure based on the atmospheric pressure, and means the pressure difference obtained by subtracting the atmospheric pressure from the absolute pressure. In this specification, the gauge pressure is expressed with the letter "G", for example, MPaG. On the other hand, when the letter "G" is not added, it means the absolute pressure.

[0016] In this specification, the "purity" of a refrigerant refers to the component ratio (mol % or mass %) determined by quantitative analysis using gas chromatography.

[0017] In this specification, the main component means a component that is contained in an amount of preferably 85 mol% to 99.9 mol%, more preferably 90 mol% to 99.9 mol%, still more preferably 95 mol% to 99.9 mol%, and particularly preferably 99 mol% to 99.9 mol%.

[0018] In this specification, extractive distillation refers to a distillation operation in which an extracting solvent is added to a mixture of two or three components that are very close in standard boiling point and difficult to separate by normal distillation, and have a relative volatility (relative volatility) close to 1, or a mixture of a combination with an azeotropic composition, to prepare a mixture for extraction, and by making the relative volatility of the original two or three components farther away from 1, separation by distillation becomes easier. Note that if the relative volatility is 1, separation by distillation is impossible.

[0019] In this specification, the relative volatility (α) is defined as the ratio of the mole fraction of liquid phase component A to the mole fraction of liquid phase component B when a composition containing at least the target component A and the target component B is in a gas-liquid equilibrium state. A , the mole fraction of liquid phase component B is x B The mole fraction of gas phase component A in equilibrium with the liquid phase is y A , the mole fraction of gas phase component B is y B In this case, the relative volatility of component A to component B is α A→B =(y A / x A ) / (y B / x B ) It is defined as follows.

[0020] In this specification, when component A is HFC-32 and component B is HFC-125, the relative volatility of component A to component B, that is, the "relative volatility of HFC-32 to HFC-125", is expressed as α 32→125 It is written as follows.

[0021] The present disclosure includes the following embodiments.

[0022] The process of the present disclosure is a process for producing purified HFC-32, comprising the steps of: The method includes an extractive distillation step of contacting a composition containing difluoromethane (HFC-32) and component X with a solvent A to obtain a composition in which the component X is reduced from the composition, The component X is at least one selected from the group consisting of pentafluoroethane (HFC-125), 1,1,1-trifluoroethane (HFC-143a), and dichlorodifluoromethane (CFC-12); The solvent A is at least one of an amine and a fluorinated ether.

[0023] In the extractive distillation step, it is preferable to apply the manufacturing method of the present disclosure, particularly when the composition containing HFC-32 and component X (also referred to as the "composition for extractive distillation" or "raw material composition") is an azeotropic composition or an azeotrope-like composition. Here, component X, HFC-125, HFC-143a, and CFC-12, can all become an azeotropic composition or an azeotrope-like composition in a mixture with HFC-32. In recent years, the recovery of used refrigerants (particularly mixed refrigerants) and the recycling of specific components have been promoted, so that in the present disclosure, for example, used HFC-410A (mixed refrigerant of HFC-32 and HFC-125) can be applied as the composition for extractive distillation (raw material composition).

[0024] (Extractive distillation process) The extractive distillation step in the production method of the present disclosure is a step of contacting a composition (composition for extractive distillation) containing component X (at least one selected from the group consisting of HFC-125, HFC-143a, and CFC-12) and HFC-32 with a solvent A (at least one of an amine and a fluorinated ether) to obtain a composition in which the component X has been reduced from the composition. In other words, the extractive distillation step is a step of extractively distilling a composition (composition for extractive distillation) containing component X and HFC-32 in the presence of solvent A to obtain a composition in which the component X has been reduced from the composition. In this disclosure, "reduction" in the extractive distillation step means reducing the content ratio of a specific compound (composition X) in the composition for extractive distillation.

[0025] The above-mentioned composition for extractive distillation contains component X and HFC-32 in a total concentration of 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. For example, when the main component of component X is HFC-125, the composition for extractive distillation may be a composition (particularly an azeotropic composition or an azeotrope-like composition) containing HFC-125 and HFC-32 preferably in the total concentration described above after recovering used HFC-410A and removing easily separable by-products through a prior separation step (any distillation step, etc.) as necessary.

[0026] Also, similarly, ·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) A used recovered mixed refrigerant containing one or more components X such as those mentioned above and HFC-32 as constituent components can be subjected to any distillation process or the like to obtain a composition for extractive distillation.

[0027] The composition for extractive distillation preferably consists of only HFC-32 and component X, but it is permissible for the composition for extractive distillation to contain unavoidable impurities due to the conditions of the preparation process thereof.

[0028] HFC-125 (standard boiling point: -48.1°C), which is a type of component X, and HFC-32 (standard boiling point: -51.7°C) are azeotropic or azeotrope-like, and the azeotropic or azeotrope-like composition of HFC-125 and HFC-32 has a boiling point that is lower than the boiling points of both HFC-125 and HFC-32 (the azeotropic composition at 0.1013 MPa is HFC-32 / HFC-125=87.8 / 12.2 (mol%), temperature is -51.8°C). In addition, HFC-143a (standard boiling point: -47.3°C), which is a type of component X, and HFC-32 (standard boiling point: -51.7°C) are azeotropic or azeotrope-like, and the azeotropic composition or azeotrope-like composition of HFC-143a and HFC-32 has a boiling point that is lower than the boiling points of both HFC-143a and HFC-32 (the azeotropic composition at 0.1013 MPa is HFC-32 / HFC-143a=77.8 / 22.2 (mol%), temperature is -52.5°C). Furthermore, HFC-12 (standard boiling point: -29.8°C), which is one type of component X, and HFC-32 (standard boiling point: -51.7°C) are azeotropic or azeotrope-like, and the azeotropic or azeotrope-like composition of HFC-12 and HFC-32 has a boiling point at a temperature lower than the boiling points of both HFC-12 and HFC-32 (azeotropic composition HFC-32 / HFC-12=96.5 / 3.5 (mol%) at 0.1013 MPa, temperature -51.7°C). The composition of the extractive distillation composition supplied to the extractive distillation step is preferably 50.0% or more and 99.999% or less, more preferably 70.0% or more and 99.999% or less, in terms of the molar ratio of HFC-32. Furthermore, the composition containing HFC-32 as a main component obtained by extractive distillation preferably has a molar ratio of HFC-32 of 99.500% or more, more preferably 99.900% or more, and even more preferably 99.999% or more.

[0029] The extractive distillation step is preferably a step of contacting the composition for extractive distillation with a solvent A and subjecting it to extractive distillation to obtain a composition containing HFC-32 and substantially not containing component X.

[0030] In this specification, "substantially free of component X" means that the content of component X in the composition obtained in the extractive distillation step (the total amount of HFC-125, HFC-143a, and CFC-12 when two or more of them are contained) is preferably less than 1 mass%, more preferably less than 0.5 mass%, and particularly preferably less than 0.1 mass%.

[0031] In the above extractive distillation step, solvent A, which is at least one of amine and fluorinated ether, is used as the extractive solvent. The extractive solvent in the present disclosure is preferably composed of at least one of amine and fluorinated ether, but it is acceptable for it to contain unavoidable impurities to the extent that they do not affect the extractive distillation step. Hereinafter, the solvent A is also simply referred to as the extractive solvent in the present disclosure.

[0032] The amine may be any liquid amine that can be used as an extraction solvent, and may be a amine having the general formula: NR 1 R 2 R 3 [In the formula, R 1 , R 2 and R 3 are the same or different and each represents a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms which may have a substituent. 1 , R 2 and R 3 except when all are hydrogen. It is preferable that the amine is an amine represented by the following formula:

[0033] The amine preferably has a normal boiling point of -10 to 160°C.

[0034] The amine is preferably at least one selected from the group consisting of monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, mono-n-propylamine, di-n-propylamine, tri-n-propylamine, mono-isopropylamine, and di-isopropylamine. Among these amines, at least one of diethylamine and triethylamine is more preferable because the operating conditions of the distillation column are easily adjusted to pressure and temperature that are easy to operate. The CasNo. and normal boiling points of these amines are shown in Table 1 below.

[0035] [Table 1]

[0036] These amines can be used alone or in combination of two or more kinds.

[0037] The fluorinated ether may be any fluorinated ether that can be used as an extraction solvent. 4 -OR 5 [In the formula, R 4 and R 5 C n H m F l Here, n is an integer of 1 to 20, m+l=2n+1, and m and l are integers of 0 or more. It is preferable that the fluorinated ether is represented by the following formula:

[0038] The fluorinated ether is preferably at least one selected from the group consisting 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). Among these fluorinated ethers, at least one selected from the group consisting of HFE-7100, HFE-7200, and HFE-7300 is particularly preferable from the viewpoint of handling, operating temperature, etc. The CasNo. and normal boiling point of these fluorinated ethers are shown in Table 2 below.

[0039] [Table 2]

[0040] (However, since HFE-7100 and HFE-7200 are two-component mixtures, the CasNo. of the constituent components is listed together.) These fluorinated ethers can be used alone or in combination of two or more kinds.

[0041] The mixing ratio of the amine and the fluorinated ether in the solvent A is not limited, and the solvent A may contain only the amine, the fluorinated ether, or a mixture of these two in any ratio.

[0042] Regarding the temperature range of the standard boiling point in the above extractive distillation step, the temperature difference between the extractive solvent and the compound to be separated in the extractive distillation step is sufficient to allow separation by simple distillation, stripping, etc., usually a temperature difference of 20°C or more, but if the standard boiling point is too high, the extractive solvent itself may be decomposed. Therefore, from the viewpoint of efficiently performing the extractive distillation, the standard boiling point of the extractive solvent is preferably 30 to 135°C, more preferably 35 to 120°C, even more preferably 40 to 100°C, and particularly preferably 50 to 90°C.

[0043] The amount of the extractive solvent used in the above extractive distillation step is preferably 1 to 30 molar equivalents, and more preferably 5 to 25 molar equivalents, relative to the composition for extractive distillation supplied to the extractive distillation column.

[0044] The concentration of component X in the composition for extractive distillation in the above extractive distillation step is preferably 50 mol % or less, more preferably 30 mol % or less, and even more preferably 10 mol % or less.

[0045] The number of theoretical plates of the extractive distillation column used in the extractive distillation step is preferably 10 or more, more preferably 20 or more. From an economical viewpoint, the number of theoretical plates of the extractive distillation column used in the extractive distillation step is preferably 100 or less, more preferably 70 or less.

[0046] In the above extractive distillation step, it is preferable to supply the extractive solvent to the upper stage of the extractive distillation column. In addition, it is preferable that the extractive solvent used in the above extractive distillation step is the extractive solvent recovered and recycled in the extractive solvent recovery step described below.

[0047] In the above extractive distillation step, the pressure at which the extractive distillation is carried out (pressure in the first distillation column) is preferably 0.05 to 5 MPaG (gauge pressure). The lower limit of the pressure is preferably 0.05 MPaG, more preferably 0.1 MPaG, even more preferably 0.25 MPaG, and particularly preferably 0.5 MPaG. The upper limit of the pressure is preferably 5 MPaG, more preferably 4 MPaG, even more preferably 3 MPaG, and particularly preferably 2 MPaG.

[0048] The above extractive distillation step can be carried out as a discontinuous or continuous operation, and from an industrial point of view, it is preferable to carry out the extractive distillation step as a continuous operation. Furthermore, by repeating the extractive distillation, the distillate components can be highly purified.

[0049] In the above extractive distillation step, when HFC-32 is distilled from the above extractive distillation composition, it is preferable to use an extractive solvent that, when added, has a relative volatility (specific volatility) of HFC-32 to component X of 1.70 or more, preferably 2.00 or more. This increases the gas phase molar fraction of HFC-32, increasing the amount of HFC-32 in the gas phase, making it possible to separate HFC-32 from the top of the extractive distillation column, and obtaining the extractive solvent and component X from the bottom of the extractive distillation column.

[0050] (Extraction solvent recovery process) The production method of the present disclosure preferably includes an extractive solvent recovery step of recovering the extractive solvent used in the extractive distillation step and recycling the recovered extractive solvent to the extractive distillation step.

[0051] The extractive solvent recovery step includes a distillation step (hereinafter also referred to as a "distillation step") of distilling a composition containing the component X and the solvent A obtained from the bottom of the extractive distillation column through the extractive distillation step to separate the component X from the solvent A, and can be carried out by recovering the extractive solvent from the composition containing the solvent A and recycling it to the extractive distillation step. Note that the distillation step of separating the component X from the solvent A is preferably a distillation step of separating a composition containing the component X as a main component from a composition containing the extractive solvent as a main component.

[0052] The number of theoretical plates of the solvent recovery column (second distillation column) used in the distillation step is preferably 5 or more, more preferably 10 or more. From an economical viewpoint, the number of theoretical plates of the solvent recovery column is preferably 40 or less, more preferably 30 or less.

[0053] In the above distillation step, the pressure at which the distillation is carried out 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.

[0054] By the above distillation step, a composition containing component X as a main component can be separated from the top of the solvent recovery column, and a composition containing the extraction solvent as a main component can be obtained from the bottom of the solvent recovery column.

[0055] The above-mentioned extraction solvent recovery step can be carried out by recovering the extraction solvent from the composition containing the extraction solvent as a main component obtained from the bottom of the column in the above-mentioned distillation step and recycling it to the extractive distillation step. Note that the extraction solvent recovered from the bottom of the column can also be subjected to an optional separation step such as rectification to remove impurities as necessary before recycling to the extractive distillation step.

[0056] The above distillation step can be carried out as a discontinuous operation or a continuous operation, and from an industrial point of view, it is preferable to carry out the distillation step as a continuous operation.

[0057] The production method of the present disclosure preferably includes an extractive distillation step and an extractive solvent recovery step, and more preferably includes an optional prior distillation step for increasing the purity of the extractive distillation composition, an extractive distillation step, and an extractive solvent recovery step.

[0058] (Composition containing HFC-32, component X, and substance A (refrigerant 1)) The present disclosure encompasses a composition (hereinafter also referred to as "refrigerant 1") containing difluoromethane (HFC-32), component X, and substance A. Component X is the same as that described in the extractive distillation step, and is at least one selected from the group consisting of pentafluoroethane (HFC-125), 1,1,1-trifluoroethane (HFC-143a), and dichlorodifluoromethane (CFC-12). The type of substance A is the same as that of solvent A described in the extractive distillation step, and is at least one of amines and fluorinated ethers.

[0059] Refrigerant 1 is a composition containing HFC-32, component X, and substance A, in which the total concentration of the three components is 99.5 mass% or more relative to the entire composition, the content of component X is more than 0 mass% and not more than 0.4 mass% relative to the entire composition, and the content of substance A is more than 0 mass% and not more than 0.1 mass% relative to the entire composition. Refrigerant 1 is a composition containing refined HFC-32 finally obtained in the manufacturing method of the present disclosure, in which trace amounts of component X and extraction solvent (solvent A) remain. The expression "more than 0 mass%" can also be expressed as "0.01 mass% or more."

[0060] 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, based on the entire composition.

[0061] It is particularly preferred that refrigerant 1 consists solely of HFC-32, component X, and substance A, although it is acceptable for unavoidable impurities to be present.

[0062] The use of the refrigerant 1 is not limited, but it can be used as an air conditioning refrigerant, a heat transfer medium, a refrigerant for car air conditioners, and the like.

[0063] (Composition containing HFC-32 and component X (refrigerant 2)) The present disclosure encompasses a composition (hereinafter also referred to as "refrigerant 2") containing difluoromethane (HFC-32) and component X. The type of component X is the same as that described above.

[0064] Refrigerant 2 is a composition containing HFC-32 and component X, in which the total concentration of the two components is 99.5 mass% or more relative to the entire composition, and the content of component X is more than 0 mass% and not more than 0.4 mass% relative to the entire composition. Refrigerant 2 is a composition containing refined HFC-32 finally obtained in the production method of the present disclosure, in which a trace amount of component X remains. The expression "more than 0 mass%" can also be expressed as "0.01 mass% or more."

[0065] The total concentration of the two components in the 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, based on the total composition.

[0066] It is particularly preferable that refrigerant 2 consists of only HFC-32 and component X, but it is acceptable for unavoidable impurities to be contained.

[0067] The use of the refrigerant 2 is not limited, but it can be used as an air conditioning refrigerant, a heat transfer medium, a refrigerant for car air conditioners, and the like.

[0068] (Compositions containing purified HFC-32) The present disclosure encompasses, as a composition containing purified HFC-32, a composition containing HFC-32 and substance A (hereinafter also referred to as "composition 1"). The type of substance A is the same as that described above.

[0069] Composition 1 is a composition containing HFC-32 and substance A, in which the total concentration of the two components is 99.5 mass% or more relative to the entire composition, and the content of substance A is more than 0 mass% and 0.1 mass% or less relative to the entire composition. Note that composition 1 is a composition containing purified HFC-32 finally obtained in the manufacturing method of the present disclosure, in which a trace amount of extraction solvent (solvent A) remains. Note that the expression "more than 0 mass%" can also be expressed as "0.01 mass% or more."

[0070] 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, based on composition 1.

[0071] It is particularly preferable that composition 1 consists only of HFC-32 and substance A, but it is acceptable for it to contain unavoidable impurities.

[0072] The use of composition 1 is not limited, but it can be used, for example, as a leak detector, stabilizer, tracer, etc. when using a refrigerant. EXAMPLES

[0073] The present disclosure will be specifically described below with reference to examples, but the present disclosure is not limited to these examples.

[0074] In the examples, the concentrations of each component such as HFC-32 were measured using the following measuring device and under the following measuring conditions.

[0075] Measurement equipment: Gas chromatography (using FID detector) How to calculate the concentration of each component: Concentration of HFC-32 = moles of HFC-32 / (moles of HFC-32 + moles of component X) Concentration of component X = moles of component X / (moles of HFC-32 + moles of component X)

[0076] Examples 1 to 5 and Comparative Examples 1 to 14 For a composition containing 70 mol % of HFC-32 and 30 mol % of HFC-125, each solvent was added in an amount 6 times the moles of the composition. 32→125 was measured.

[0077] In Example 1, diethylamine was used as the solvent, and the relative volatility α 32→125 In Example 2, triethylamine was used as the solvent, and the relative volatility α 32→125 In Example 3, HFE-7300 was used as the solvent, and the relative volatility α 32→125 In Example 4, HFE-7200 was used as the solvent, and the relative volatility α 32→125 In Example 5, HFE-7100 was used as the solvent, and the relative volatility α 32→125 In Comparative Example 1, isopropyl alcohol (IPA) was used as the solvent, and the relative volatility α 32→125In Comparative Example 2, tetrahydrofuran (THF) was used as the solvent, and the relative volatility α 32→125 In Comparative Example 3, ethanol was used as the solvent, and the relative volatility α 32→125 In Comparative Example 4, 2-butanol was used as the solvent, and the relative volatility α 32→125 In Comparative Example 5, methyl ethyl ketone (MEK) was used as the solvent, and the relative volatility α 32→125 In Comparative Example 6, n-propanol was used as the solvent, and the relative volatility α 32→125 In Comparative Example 7, ethyl acetate was used as the solvent, and the relative volatility α 32→125 In Comparative Example 8, isobutanol was used as the solvent, and the relative volatility α 32→125 In Comparative Example 9, methanol was used as the solvent, and the relative volatility α 32→125 In Comparative Example 10, acetone was used as the solvent, and the relative volatility α 32→125 In Comparative Example 11, hexane was used as the solvent, and the relative volatility α 32→125 In Comparative Example 12, 5-fluoropropanol was used as the solvent, and the relative volatility α 32→125 In Comparative Example 13, trifluoroethanol was used as the solvent, and the relative volatility α 32→125 In Comparative Example 14, acetonitrile was used as the solvent, and the relative volatility α 32→125 was 0.69.

[0078] The results are summarized in Table 3 below.

[0079] [Table 3]

[0080] From the above results, it was found that amines such as diethylamine and triethylamine, and fluorinated ethers such as HFE-7300, HFE-7200, and HFE-7100 were effective as extraction solvents.

[0081] Each of the solvents used in Examples 1 to 5 had a relative volatility α of HFC-32 to HFC-143a at 5°C. 32→143a , and the relative volatility α of HFC-32 to HFC-12 at 5°C 32→12 are both greater than 1.70 and have been found to be effective not only for the separation of HFC-32 from HFC-125 by extractive distillation, but also for the separation of HFC-32 from HFC-143a and / or HFC-12 by extractive distillation.

[0082] Example 6 In accordance with the flow diagram shown in FIG. 1, a purified HFC-32 was produced using a composition for extractive distillation containing HFC-32 and component X (HFC-125) as a raw material and HFE-7100 as an extractive solvent by a process consisting of an extractive distillation step and an extractive solvent recovery step.

[0083] (Extractive distillation process) The extractive distillation composition was fed to the extractive distillation column at a flow rate of 956 mol / hr from the 45th plate from the top of the column having a theoretical number of 70 plates. The extractive solvent (HFE-7100) was fed to the extractive distillation column at a flow rate of 9650 mol / hr from the 3rd plate. The operating pressure of the extractive distillation column was 0.5 MPaG, and the column top temperature was -10°C.

[0084] (Extraction solvent recovery process) The bottoms withdrawn from the column bottom in the extractive distillation process were fed to the fifth plate from the top of an extractive solvent recovery column (hereinafter referred to as the "solvent recovery column") having 15 theoretical plates, and HFC-125 was recovered from the top with a purity of 99.99%. The operating pressure of the solvent recovery column was 0.4 MPaG, and the column top temperature was -9°C.

[0085] The bottoms containing HFE-7100 (flow rate of HFE-7100: 144 mol / hr) extracted from the bottom of the recovery column were recycled to the extractive distillation step.

[0086] The mass balance of Example 6 according to the process of FIG. 1 was 667.1 mol / hr HFC-32, 289.1 mol / hr HFC-125, and 9650.6 mol / hr HFE-7100 (extraction solvent) in F1. 6.7 mol / hr HFC-32, 289.1 mol / hr HFC-125, and 9650.2 mol / hr HFE-7100 (extraction solvent) in F2. 660.4 mol / hr HFC-32, 0.0014 mol / hr HFC-125, and trace amounts (less than 0.1 ppm) of HFE-7100 (extraction solvent) in F3. Trace amounts (less than 0.1 ppm) of HFC-32, 0.005 mol / hr HFC-125, and 9650.6 mol / hr HFE-7100 (extraction solvent) in F4. In F5, the rates of HFC-32 were 6.7 mol / hr, HFC-125 289.1 mol / hr, and HFE-7100 (extraction solvent) 0.002 mol / hr. Table 4 below shows the content of the three components at each of positions F1, F2, F3, F4, and F5 in the process of Example 6 (the total content of the three components is 100 mol%).

[0087] [Table 4]

[0088] The amines shown in Examples 1 and 2 and the fluorinated ethers shown in Examples 3 to 5 all have a relative volatility α of HFC-32 relative to component X (HFC-125, HFC-143a, HFC-12). 32→成分X is 1.70 or more, which is larger than the comparative examples (1.69 or less), and indicates that the separation efficiency is improved compared to the comparative examples in that a relatively high HFC-32 concentration in the gas phase can be secured. Therefore, in the separation of component X and HFC-32, the process of the present disclosure, which uses at least one extractant (solvent A) selected from amine and fluorinated ether in the extractive distillation step, is very effective. [Explanation of symbols]

[0089] 1. Extractive distillation tower 2. Solvent recovery tower

Claims

1. The method includes an extractive distillation step of contacting a composition containing difluoromethane (HFC-32) and component X with a solvent A to obtain a composition in which the component X is reduced from the composition, The component X is at least one selected from the group consisting of pentafluoroethane (HFC-125), 1,1,1-trifluoroethane (HFC-143a), and dichlorodifluoromethane (CFC-12); The solvent A is at least one of an amine and a fluorinated ether; A method for producing purified HFC-32.

2. The production method according to claim 1, further comprising a distillation step of distilling a composition containing the component X and the solvent A obtained from the bottom of the extractive distillation column through the extractive distillation step to separate the component X and the solvent A.

3. The production method according to claim 1, wherein the extractive distillation step using the first distillation column performing the extractive distillation step is performed under a pressure of 0.05 to 5 MPaG (gauge pressure).

4. The method according to claim 2, wherein the distillation step using the second distillation column for performing the distillation step is performed under a pressure of 0.05 to 3 MPaG (gauge pressure).

5. The method according to claim 1, further comprising a solvent recovery step of recovering the solvent A used in the extractive distillation step and recycling the recovered solvent A to the extractive distillation step.

6. The amine has the general formula: NR １ R ２ R ３ [In the formula, R １ , R ２ and R ３ are the same or different and each represents a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms which may have a substituent. １ , R ２ and R ３ except when all are hydrogen. The method according to claim 1 , wherein the compound is represented by the formula:

7. The method according to claim 1, wherein the amine is at least one selected from the group consisting of monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, mono-n-propylamine, di-n-propylamine, tri-n-propylamine, mono-isopropylamine, and di-isopropylamine.

8. The fluorinated ether has the general formula R ４ -O-R ５ [In the formula, R ４ and R ５ are the same or different 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 of 0 or more. The method according to claim 1 , wherein the compound is represented by the formula:

9. The fluorinated ether is at least one selected from the group consisting 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). The method according to claim 1,

10. A composition containing difluoromethane (HFC-32), a component X, and a substance A, wherein the total concentration of the three components is 99.5 mass% or more based on the entire composition, The component X is at least one selected from the group consisting 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 the component X is more than 0 mass% and 0.4 mass% or less with respect to the entire composition, and the content of the substance A is more than 0 mass% and 0.1 mass% or less with respect to the entire composition. composition.

11. A composition containing difluoromethane (HFC-32) and a substance A, wherein the total concentration of the two components is 99.5% by mass or more based on the entire composition; The substance A is at least one of an amine and a fluorinated ether; and The content of the substance A is more than 0% by mass and 0.1% by mass or less with respect to the total amount of the composition. composition.

12. A composition containing difluoromethane (HFC-32) and component X, wherein the total concentration of the two components is 99.5 mass% or more based on the entire composition, The component X is at least one selected from the group consisting of pentafluoroethane (HFC-125), 1,1,1-trifluoroethane (HFC-143a), and dichlorodifluoromethane (CFC-12); and The content of the component X is more than 0 mass% and 0.4 mass% or less with respect to the entire composition. composition.

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