Method for purifying (z)-1-chloro-2,3,3,3-tetrafluoropropene

Abstract

Provided is a purification method for 1224yd(Z) that can efficiently separate 244bb from a composition containing (Z)-1-chloro-2,3,3,3-tetrafluoropropene (1224yd(Z)) and 2-chloro-1,1,1,2-tetrafluoropropane (244bb), thereby obtaining a purified product of 1224yd(Z) containing 1224yd(Z) at a high concentration. A purification method for 1224yd(Z) that separates at least a portion of 244bb from a composition containing 1224yd(Z) and 244bb by distilling the aforementioned composition in the presence of an extraction solvent containing at least one compound selected from the group consisting of an alcohol, an ether, a nitrile, a ketone, a carbonate, an amide, an ester, a sulfoxide, a hydrocarbon, a chlorinated hydrocarbon, and a fluorinated hydrocarbon.

Description

Technical Field

[0001] This invention relates to a method for purifying (Z)-1-chloro-2,3,3,3-tetrafluoropropene. Background Technology

[0002] Hydrochlorofluorocarbons (HCFCs) have a detrimental effect on the ozone layer, and therefore their production is planned to be regulated. Examples of HCFCs include 3,3-dichloro-1,1,1,2,2-pentafluoropropane (HCFC-225ca) and 1,3-dichloro-1,1,2,2,3-pentafluoropropane (HCFC-225cb), but with the regulation of HCFCs, there is a desire to develop compounds that can replace them.

[0003] An example of a compound that can replace HCFCs is 1-chloro-2,3,3,3-tetrafluoropropene (HCFO-1224yd, hereinafter also referred to as "1224yd"). 1224yd has a low global warming potential (GWP) and is a novel compound that is useful in applications such as cleaning agents, solvents, refrigerants, foaming agents, and aerosols.

[0004] A known method for manufacturing 1224yd is as follows: 2,3,3,3-tetrafluoropropene (HFO-1234yf, hereinafter also referred to as "1234yf") is reacted with chlorine to obtain 1,2-dichloro-2,3,3,3-tetrafluoropropane (HCFC-234bb, hereinafter also referred to as "234bb"). This 234bb is then subjected to a dehydrochlorination reaction in the liquid phase in the presence of a base to produce 1224yd (see, for example, Patent Document 1).

[0005] Here, components such as unreacted raw materials, intermediates, or byproducts other than the target substance (1224yd) in the reaction mixture generated by the above method are separated by distillation or the like, thereby producing a high concentration of 1224yd. However, when byproducts containing boiling points very close to 1224yd are present as components other than 1224yd, it is difficult to separate them using conventional distillation. As a method for separating components with such very close boiling points, a so-called extractive distillation method is known. The extractive distillation method is a method in which an extraction solvent that changes the relative volatility is added to a mixture containing two components with very close boiling points, or an azeotropic or near-azeotropic composition consisting of two components, and distillation is performed, thereby separating one component (see, for example, Patent Document 2).

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: International Publication No. 2017 / 110851

[0009] Patent Document 2: International Publication No. 2016 / 080283 Summary of the Invention

[0010] The problem the invention aims to solve

[0011] The inventors have discovered that the reaction mixture obtained in the method for manufacturing 1224yd using the above-mentioned 1234yf as a raw material contains, in addition to the target compound 1224yd, hydrogen chloride generated by the above-mentioned chlorination reaction and 2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb, hereinafter also referred to as "244bb"), a byproduct of the reaction of 1234yf.

[0012] Here, 1224yd exists in both Z and E configurations, with the Z configuration being more stable than the E configuration. Therefore, a purification method for 1224yd(Z) is particularly needed. However, the boiling points of 1224yd(Z) and 244bb are very close; for example, the boiling point of 1224yd(Z) is approximately 14–15 °C, and the boiling point of 244bb is approximately 15.2 °C (both at atmospheric pressure). Therefore, it is evident that when 244bb remains in the reaction mixture containing 1224yd(Z), it is difficult to separate 1224yd(Z) and 244bb using conventional methods such as distillation. Furthermore, when applying extractive distillation to industrial applications to separate 1224yd(Z) and 244bb, the choice of extraction solvent is the most crucial factor, requiring optimization of distillation conditions for each extraction solvent used.

[0013] The boiling point difference between 1224yd(Z) and 244bb is only about 0.2–1.2 °C, as mentioned above. Therefore, the conditions for separating 1224yd(Z) and 244bb are very stringent, even compared to typical extractive distillation. Consequently, it is difficult to predict which extraction solvent can be used to efficiently separate the two from a mixture containing 1224yd(Z) and 244bb, for example, using a distillation column with fewer stages, to obtain a high concentration of 1224yd(Z).

[0014] The purpose of this invention is to provide a purification method for 1224yd(Z), which can efficiently separate 244bb from a composition containing 1224yd(Z) and 244bb, thereby obtaining a purified product of 1224yd(Z) containing 1224yd(Z) at a high concentration.

[0015] Solution for solving the problem

[0016] The present invention provides a method for purifying (Z)-1-chloro-2,3,3,3-tetrafluoropropene with the structure shown below.

[0017] [1] A purification method for 1224yd(Z) comprising separating at least a portion of 244bb from a composition comprising (Z)-1-chloro-2,3,3,3-tetrafluoropropene (1224yd(Z)) and 2-chloro-1,1,1,2-tetrafluoropropane (244bb) by distillation in the presence of an extraction solvent, wherein the extraction solvent comprises at least one compound selected from the group consisting of alcohols, ethers, nitriles, ketones, carbonates, amides, esters, sulfoxides, hydrocarbons, chlorinated hydrocarbons and fluorinated hydrocarbons.

[0018] [2] According to the purification method described in [1], the molar amount of 1224yd(Z) in the aforementioned composition is in the ratio of 1 to 99 mol% to the total molar amount of 1224yd(Z) and 244bb.

[0019] [3] According to the purification method described in [1] or [2], wherein the boiling point of the aforementioned extraction solvent is 40℃~250℃.

[0020] [4] The purification method according to any one of [1] to [3], wherein the amount of the aforementioned extraction solvent is 0.1:1 to 1000:1 in terms of the molar ratio of extraction solvent to 244bb.

[0021] [5] The purification method according to any one of [1] to [4], wherein the aforementioned extraction solvent is a solvent that makes the relative volatility of 1224yd(Z) relative to 244bb greater than 1.

[0022] [6] The purification method according to any one of [1] to [4], wherein the aforementioned extraction solvent is a solvent that makes the relative volatility of 1224yd(Z) relative to 244bb 1.01 or higher.

[0023] [7] The purification method according to any one of [1] to [4], wherein the aforementioned extraction solvent is a solvent that makes the relative volatility of 1224yd(Z) relative to 244bb less than 1.

[0024] [8] The purification method according to any one of [1] to [4], wherein the aforementioned extraction solvent is a solvent that makes the relative volatility of 1224yd(Z) relative to 244bb less than 0.96.

[0025] [9] The purification method according to any one of [1] to [4], wherein the aforementioned extraction solvent is at least one compound selected from the group consisting of CF3CH2OCF2CF2H, CF3CF2CF2CF2CF2CF2H, 1,2-dichloro-2,3,3,3-tetrafluoropropane and 1,3-dichloro-1,1,2,2,3-pentafluoropropane.

[0026]

[10] The purification method according to any one of [1] to [4], wherein the aforementioned extraction solvent is at least one compound selected from the group consisting of CF3CH2OCF2CF2H, CF3CF2CF2CF2CF2CF2H and 1,2-dichloro-2,3,3,3-tetrafluoropropane.

[0027]

[11] The purification method according to any one of [1] to [4], wherein the aforementioned extraction solvent is at least one compound selected from the group consisting of N,N-dimethylformamide, tetrahydrofuran, acetone, ethyl acetate, toluene, acetonitrile, carbon tetrachloride, methanol, trichloroethylene, chloroform, n-hexane and 1,1-dichloro-2,3,3,3-tetrafluoropropene.

[0028]

[12] The purification method according to any one of [1] to [4], wherein the aforementioned extraction solvent is at least one compound selected from the group consisting of N,N-dimethylformamide, tetrahydrofuran, acetone, ethyl acetate, toluene, acetonitrile, carbon tetrachloride and methanol.

[0029] In this specification, "extractive distillation" refers to a distillation operation in which an extractive solvent is added to a composition containing two components with very similar boiling points, or forming an azeotropic or azeotropic combination, that are difficult to separate by conventional distillation, and whose relative volatility is close to 1. This significantly alters the relative volatility of the two original components, making separation easier. The solvent affects the vapor-liquid equilibrium of the two components, thus changing their relative volatility.

[0030] As the relative volatility in this specification, the relative volatility of 1224yd(Z) relative to 244bb is used as shown by the following formula.

[0031] The relative volatility of 1224yd(Z) relative to 244bb = (mole fraction of 1224yd(Z) in the gas phase (%) / mole fraction of 244bb in the gas phase (%)) / (mole fraction of 1224yd(Z) in the liquid phase (%) / mole fraction of 244bb in the liquid phase (%))

[0032] In addition, in this specification, "distillate" refers to the substance distilled from the top side of the distillation column, and "boiler product" refers to the substance distilled from the bottom side of the distillation column.

[0033] Furthermore, in this specification, the term "main component" refers to components other than the main component that are present in relatively small amounts. It is considered sufficient if the amount of the "main component" is 50 mol% or more of the total, but specifically 60 mol% or more, for example, 80 mol% or more. Additionally, unless otherwise specified in this specification, the boiling point of the compound is at atmospheric pressure (1.013 × 10⁻⁶). 5The value under Pa). In this specification, “~” indicates the range of values, which includes the values ​​recorded before and after it as the lower limit and upper limit.

[0034] It should be noted that in this specification, for carbon halides, the abbreviation of the compound is listed in parentheses after the compound name, and is used in place of the compound name as needed. Additionally, for compounds with intramolecular double bonds and exhibiting E and Z configurations, (E) and (Z) are respectively added to the end of the compound's abbreviation to indicate the E and Z configurations. If the E and Z configurations are not explicitly stated in the compound's name or abbreviation, the name or abbreviation refers to the collective term encompassing the E, Z, and mixtures of E and Z configurations. Furthermore, as abbreviations, sometimes only the numbers following the hyphen (-) and the lowercase English letters are used.

[0035] The effects of the invention

[0036] The purification method of the present invention can efficiently separate 244bb from a composition containing 1224yd(Z) and 244bb to obtain a purified product containing 1224yd(Z) at a high concentration. Detailed Implementation

[0037] The embodiments of the present invention will be described in detail below. The present invention is not limited to the following embodiments.

[0038] The purification method for 1224yd(Z) in this embodiment involves distilling a composition containing 1224yd(Z) and 244bb in the presence of an extraction solvent containing at least one compound selected from the group consisting of alcohols, ethers, nitriles, ketones, carbonates, amides, esters, sulfoxides, hydrocarbons, fluorinated hydrocarbons, and chlorinated hydrocarbons, thereby separating at least a portion of 244bb from the aforementioned composition. Hereinafter, the "composition containing 1224yd(Z) and 244bb" will also be referred to as the "distillation composition".

[0039] The boiling points of 1224yd(Z) and 244bb are very close. Therefore, 1224yd(Z) and 244bb form azeotropic or azeotropic compositions across almost the entire compositional range. Specifically, for compositions containing 99–1 mol% 1224yd(Z) and 1–99 mol% 244bb relative to their total content, the relative volatility is 1.00 ± 0.01. Mixtures of 1224yd(Z) and 244bb within this compositional range have a relative volatility of 1.011 × 10⁻⁶. 6 The boiling point at Pa is 15.0℃.

[0040] An azeotropic composition is a composition defined above where the relative volatility of 1224yd(Z) relative to 244bb is 1. An azeotropic composition is defined as one in which the composition of the gas phase generated by the vaporization of the liquid phase is the same as that of the liquid phase, or the composition of the liquid phase generated by the liquefaction of the gas phase is the same as that of the gas phase. The composition of the azeotropic composition does not change due to evaporation or condensation. It should be noted that the composition of the azeotropic composition changes depending on pressure conditions.

[0041] An azeotropic-like composition is a composition in which the relative volatility of 1224yd(Z) relative to 244bb is very close to 1, as defined above. An azeotropic-like composition is a composition that exhibits behavior similar to that of an azeotropic composition. That is, the composition of the gas phase generated by the vaporization of the liquid phase of the azeotropic-like composition is substantially the same as the composition of the liquid phase, or the composition of the liquid phase generated by the liquefaction of the gas phase is substantially the same as the composition of the gas phase.

[0042] Azeotropic compositions, i.e., those with a relative volatility of 1, cannot be separated by distillation because the gas and liquid phases are composed of the same substance. For azeotropic-like compositions, the closer the relative volatility is to 1, the more difficult it is to separate them by distillation.

[0043] In the purification method of 1224yd(Z) of this embodiment, an extraction solvent with a relative volatility of 1224yd(Z) relative to 244bb greater than 1 or less than 1 is used, and at least a portion of 244bb in the distillation composition is separated by extractive distillation, thereby obtaining a purified product of 1224yd(Z) containing 1224yd(Z) at a higher concentration. In other words, by using a solvent with high affinity for either 244bb or 1224yd(Z), either 1224yd(Z) or 244bb is made less volatile, thereby making the ratio of 1224yd(Z) to the total amount of 1224yd(Z) and 244bb in the distillate or effluent after distillation greater than the content ratio of 1224yd(Z) to the total amount of 1224yd(Z) and 244bb in the distillation composition.

[0044] Specifically, if an extraction solvent is used that makes the relative volatility of 1224yd(Z) relative to 244bb greater than 1, the molar fraction of 1224yd(Z) in the gas phase increases, and therefore the following components can be easily extracted by extractive distillation: as a distillate, the component in which the content ratio of 1224yd(Z) relative to the total amount of 1224yd(Z) and 244bb is higher than that of the distillation composition; and as a flask product, the component in which the content ratio of 244bb relative to the total amount of 1224yd(Z) and 244bb is higher than that of the distillation composition. Conversely, if an extraction solvent is used that makes the relative volatility of 1224yd(Z) relative to 244bb less than 1, the molar fraction of 244bb in the gas phase increases, thus allowing the following components to be easily extracted by extractive distillation: as a distillate, the component with a higher content of 244bb relative to the total amount of 1224yd(Z) and 244bb compared to the distillation composition; and as a residue, the component with a higher content of 1224yd(Z) relative to the total amount of 1224yd(Z) and 244bb compared to the distillation composition.

[0045] Thus, by using the purification method of 1224yd(Z) in this embodiment, a purified product containing 1224yd(Z) at a high concentration can be obtained by distilling the composition for distillation in the presence of the aforementioned extraction solvent.

[0046] (Composition for distillation)

[0047] The distillation composition comprises 1224yd(Z) and 244bb. The distillation composition may also be formed solely of 1224yd(Z) and 244bb. Furthermore, the distillation composition may also contain other components besides 1224yd(Z) and 244bb, provided that the effects of the invention are not impaired.

[0048] The content of 1224yd(Z) in the distillation composition is not particularly limited, but from the viewpoint of distillation efficiency, it is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more.

[0049] As a distillation composition of this embodiment, an example example is a reaction mixture obtained by reacting 2,3,3,3-tetrafluoropropene (1234yf) with chlorine to obtain 1,2-dichloro-2,3,3,3-tetrafluoropropane (234bb), and then dehydrochlorinating the 234bb in the liquid phase in the presence of a base to produce 1224yd.

[0050] Other components included in the distillation composition besides 1224yd(Z) and 244bb, besides 1224yd(E) other than 1224yd(Z) generated in the manufacturing method of 1224yd using 1234yf as a raw material, unreacted raw material 1234yf, and intermediate product 234bb, include byproducts from the reaction process such as 1,1,2-trichloro-2,3,3,3-tetrafluoropropane (HCFC-224ba) and 1,1,1,2-tetrachloro-2,3,3,3-tetrafluoropropane (CFC-214bb). These other components can be separated by conventional methods such as distillation. Therefore, before performing the purification method of this embodiment, considering distillation efficiency, other components can be removed to the desired extent by conventional methods such as distillation. Alternatively, after performing the purification method of this embodiment, they can be separated from 1224yd(Z) or 244bb by conventional methods such as distillation.

[0051] (Extraction solvent)

[0052] The extraction solvent in this embodiment is at least one compound selected from the group consisting of alcohols, ethers, nitriles, ketones, carbonates, amides, esters, sulfoxides, hydrocarbons, chlorinated hydrocarbons, and fluorinated hydrocarbons.

[0053] Here, "alcohol" refers to a compound having at least one hydroxyl group and no halogen atom, preferably an aliphatic alcohol with 1 to 6 carbon atoms in its main chain, and more preferably an aliphatic alcohol with 1 to 4 carbon atoms. Specifically, examples include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, 1-pentanol, 2-pentanol, 1-ethyl-1-propanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 3-methyl-2-butanol, neopentanol, 1-hexanol, 2-methyl-1-pentanol, 4-methyl-2-pentanol, and 2-ethyl-1-butanol. Among these, methanol, ethanol, and 2-propanol are preferred from the perspective of ease of acquisition and productivity in the distillation process, with methanol being the most preferred.

[0054] Ethers are compounds having at least one ether bond and lacking halogen atoms, and can be cyclic or linear. The carbon number of the ether is preferably 1 to 6, more preferably 1 to 4. Specifically, examples include dimethyl ether, diethyl ether, dipropyl ether, diisopropyl ether, ethylmethyl ether, ethylpropyl ether, ethylisopropyl ether, 1,3-dioxolane, 1,4-dioxane, trimethoxyethane, triethoxyethane, furan, 2-methylfuran, and tetrahydrofuran (THF). Among these, 1,3-dioxolane, 1,4-dioxane, and THF are preferred from the perspective of ease of acquisition and productivity in the distillation process, with THF being the most preferred.

[0055] Nitriles refer to those with the general formula: R 1 -CN(R1 The compound shown represents an unsubstituted aliphatic hydrocarbon group. As a nitrile, R in the above general formula is preferred. 1 Nitriles having 1 to 5 carbon atoms. Specifically, examples include acetonitrile, propionitrile, butyronitrile, and isobutyronitrile. Among these, acetonitrile is preferred in terms of ease of acquisition and productivity in the distillation process.

[0056] Ketones refer to those with the general formula: R 2 -C(=O)-R 3 (R 2 and R 3 The compounds are represented by unsubstituted aliphatic hydrocarbon groups that are the same as or different from each other. As ketones, R in the above general formula is preferred. 2 and R 3 The number of carbon atoms are 1 to 2 and R 2 and R 3 Ketones with a total carbon number of 2 to 4. Specifically, examples include acetone, methyl ethyl ketone, and diethyl ketone. Among these, acetone is preferred from the perspectives of ease of acquisition and productivity in the distillation process.

[0057] The carbonate is preferably a chain carbonate or an aliphatic cyclic carbonate with 1 to 6 carbon atoms. Specifically, examples include dimethyl carbonate, diethyl carbonate, ethylene carbonate, and propylene carbonate. Among these, dimethyl carbonate and diethyl carbonate are preferred in terms of ease of acquisition and productivity in the distillation process.

[0058] Amides can be categorized as chain amides with 3 to 5 carbon atoms or aliphatic cyclic amides, with tertiary amides in which all hydrogen atoms of the amino group are substituted by alkyl groups being preferred. Specifically, formamide, acetamide, N,N-dimethylformamide (DMF), and N,N-dimethylacetamide are examples. Among these, DMF and N,N-dimethylacetamide are preferred from the perspective of ease of acquisition and productivity in the distillation process, with DMF being the most preferred.

[0059] As an ester, it is a compound having an ester group other than a carbonate group. Examples of esters include chain esters with 3 to 6 carbon atoms or aliphatic cyclic esters, with chain esters with 4 to 6 carbon atoms being preferred. Specifically, examples of esters include methyl acetate, ethyl acetate, propyl acetate, butyl acetate, etc. Among these, ethyl acetate is preferred from the perspective of ease of acquisition and productivity in the distillation process.

[0060] Sulfoxide refers to the general formula: R 4 -S(=O)-R 5 (R 4 and R 5 The compound represented by ) indicates unsubstituted aliphatic hydrocarbon groups that are the same as or different from each other. Specifically, from the perspective of ease of acquisition and productivity in the distillation process, R in the above general formula is preferred. 4 and R5 Both are dimethyl sulfoxide (DMSO) of methyl groups.

[0061] Examples of hydrocarbons include aliphatic chain hydrocarbons with 3 to 6 carbon atoms, aliphatic cyclic hydrocarbons with 3 to 6 carbon atoms, and aromatic hydrocarbons with 6 to 10 carbon atoms. Aliphatic chain hydrocarbons with 3 to 6 carbon atoms or aromatic hydrocarbons with 6 to 10 carbon atoms are preferred. Specifically, examples include n-pentane, isopentane, n-hexane, cyclohexane, benzene, and toluene. Among these, n-hexane and toluene are preferred from the perspective of ease of acquisition and productivity in the distillation process, with toluene being the most preferred.

[0062] Chlorinated hydrocarbons are compounds in which one or more hydrogen atoms of the hydrocarbon backbone are replaced by chlorine atoms, and which do not contain fluorine atoms. Chlorinated hydrocarbons are preferably compounds with an aliphatic chain hydrocarbon or aliphatic cyclic hydrocarbon backbone having 1 to 4 carbon atoms. Specific examples of chlorinated hydrocarbons include dichloromethane, chloroform (CHCl3), carbon tetrachloride (CCl4), 1,2-dichloropropane, perchloroethylene, and trichloroethylene. Among these, chloroform, carbon tetrachloride, and trichloroethylene are preferred from the perspective of ease of acquisition and productivity in the distillation process, with carbon tetrachloride being the most preferred.

[0063] Fluorinated hydrocarbons are compounds in which one or more hydrogen atoms of a hydrocarbon backbone are replaced by fluorine atoms. Fluorinated hydrocarbons are preferably compounds with an aliphatic chain hydrocarbon or aliphatic cyclic hydrocarbon backbone having 1 to 10 carbon atoms. Fluorinated hydrocarbons may have ether bonds or double bonds between carbon-carbon bonds. In addition, hydrogen atoms of the hydrocarbon may be replaced by chlorine atoms, hydroxyl groups, etc.

[0064] Examples of fluorinated hydrocarbons that do not have ether bonds or double bonds between carbon-carbon bonds include CF3CF2CF2CF2CF2CF2CH2CH3 (e.g., manufactured by ACG Corporation, trade name: AC6000), CF3CF2CF2CF2CF2CF2H (e.g., manufactured by ACG Corporation, trade name: AC2000), and CF3CF2CHFCHFCF3 (e.g., manufactured by DuPont, trade name: HFC4310).

[0065] In addition, examples of fluorinated hydrocarbons that also contain chlorine atoms include CClF2CF2CHClF (HCFC-225cb) and HCFC-234bb.

[0066] Examples of those with double bonds and chlorine atoms include 1,1-dichloro-2,3,3,3-tetrafluoropropene (CFO-1214ya).

[0067] As fluorinated hydrocarbons, CF3CF2CF2CF2CF2CF2CH2CH3, CF3CF2CF2CF2CF2CF2H, HCFC-225cb, HCFC-234bb, and CFO-1214ya are preferred in terms of ease of acquisition and productivity in the distillation process.

[0068] From the perspective of ease of acquisition and productivity in the distillation process, the following are preferred fluorinated hydrocarbons with ether bonds between carbon-carbon bonds: CF3CH2OCF2CF2H (e.g., manufactured by ACG Corporation, trade name: AE3000), tetrafluoropropanol, CF3CF2CF2CF2OCF3 (e.g., manufactured by Sumitomo 3M Corporation, trade name: Novec7100), and CF3CF2CF2CF2OCH2CH3 (e.g., manufactured by Sumitomo 3M Corporation, trade name: Novec7200). CF3CF2CF(CH3)OCF(CF3)2 (e.g., manufactured by Sumitomo 3M Corporation, trade name: Novec7300), compounds represented by formula (1) (e.g., manufactured by Sumitomo 3M Corporation, trade name: FC-77), compounds represented by formula (2) (e.g., manufactured by Solvay Corporation, trade name: SV-55), compounds represented by formula (3) (e.g., manufactured by Solvay Corporation, trade names: HT-70, HT-80, HT-110, HT-135).

[0069]

[0070]

[0071] In equation (2), m1 and n1 are integers from 1 to 20.

[0072]

[0073] In equation (3), m2 and n2 are integers from 1 to 20.

[0074] As an extraction solvent, among the aforementioned compounds, those with a boiling point of 40–250°C are preferred, and those with a boiling point of 40–160°C are more preferred. If the boiling point of the extraction solvent is within the aforementioned range, the productivity in the distillation process is further improved. When a mixed solvent of two or more compounds is used as the extraction solvent, the boiling point of the mixed solvent is preferably within the aforementioned range.

[0075] The extraction solvents mentioned above are classified as follows: solvents that have an affinity for 244bb only among 1224yd(Z) and 244bb, thereby making 244bb less volatile and thus resulting in a relative volatility of 1224yd(Z) relative to 244bb greater than 1 (hereinafter also referred to as "first extraction solvents"); and solvents that have an affinity for 1224yd(Z) only among 1224yd(Z) and 244bb, thereby making 1224yd(Z) less volatile and thus resulting in a relative volatility of 1224yd(Z) relative to 244bb less than 1 (hereinafter also referred to as "second extraction solvents").

[0076] For the first extraction solvent, when the extraction solvent is added to the mixture of 244bb and 1224yd(Z) according to the method described later and the relative volatility of 1224yd(Z) relative to 244bb is measured, the relative volatility is preferably 1.01 or more, and more preferably 1.02 or more. By making the relative volatility of 1224yd(Z) relative to 244bb above the aforementioned lower limit, 1224yd(Z) becomes more volatile.

[0077] Furthermore, when using compounds containing fluorine atoms as extraction solvents, the relative volatility of 1224yd(Z) relative to 244bb tends to increase. Therefore, compounds containing fluorine atoms, namely the aforementioned fluorinated hydrocarbons, are preferred as the first extraction solvent.

[0078] As the first extraction solvent, from the perspective of efficient separation of 244bb and 1224yd(Z), CF3CH2OCF2CF2H (e.g., AE3000), CF3CF2CF2CF2CF2CF2H (e.g., AC2000), HCFC-234bb, and HCFC-225cb are preferred, CF3CH2OCF2CF2H, CF3CF2CF2CF2CF2CF2H, and HCFC-234bb are more preferred, and CF3CH2OCF2CF2H and CF3CF2CF2CF2CF2CF2H are most preferred. The first extraction solvent can be formed from one of these, or from two or more as needed.

[0079] For the second extraction solvent, when the extraction solvent is added to the mixture of 244bb and 1224yd(Z) according to the method described later and the relative volatility of 1224yd(Z) relative to 244bb is measured, the relative volatility is preferably 0.98 or less, more preferably 0.96 or less, and even more preferably 0.90 or less. By keeping the relative volatility of 1224yd(Z) relative to 244bb below the aforementioned upper limit, 244bb becomes more volatile.

[0080] When using a compound without fluorine atoms as the extraction solvent, the relative volatility of 1224yd(Z) relative to 244bb tends to decrease. Therefore, as the second extraction solvent, a compound without fluorine atoms is preferred, i.e., alcohols, ethers, nitriles, ketones, carbonates, amides, esters, sulfoxides, hydrocarbons, and chlorinated hydrocarbons are preferred. More preferably, alcohols, ethers, nitriles, ketones, amides, esters, sulfoxides, hydrocarbons, and chlorinated hydrocarbons are preferred.

[0081] For efficient separation of 244bb and 1224yd(Z), the preferred second extraction solvents are DMF, THF, acetone, ethyl acetate, toluene, acetonitrile, carbon tetrachloride, methanol, trichloroethylene, chloroform, n-hexane, and CFO-1214ya. More preferred are DMF, THF, acetone, ethyl acetate, toluene, acetonitrile, carbon tetrachloride, and methanol. Most preferred are DMF, THF, acetone, and ethyl acetate. The second extraction solvent can be formed from one of these solvents, or from two or more solvents as needed.

[0082] When the extraction solvent is added to a mixture of 244bb and 1224yd(Z), the relative volatility of 1224yd(Z) relative to 244bb can be determined as follows: An extraction solvent is added to a 5:1 (molar ratio) mixture of 1224yd(Z) and 244bb at a molar ratio of 40:50:10 (extraction solvent: 1224yd(Z): 244bb), and this mixture is used as the test sample. The test sample is added to a distillation apparatus and slowly heated to boiling under atmospheric pressure with an external heater. After the boiling state stabilizes, it is maintained for a certain period of time to stabilize the composition within the distillation apparatus. Then, samples of the test sample are collected from the gas and liquid phases, respectively, and analyzed by gas chromatography to determine the molar ratio of 1224yd(Z) to 244bb. The relative volatility of 1224yd(Z) relative to 244bb after adding the extraction solvent is then calculated based on the molar ratio.

[0083] The amount of solvent used in the purification method of the present invention is not particularly limited, but is preferably 0.1:1 to 1000:1 in the molar ratio of solvent to 244bb.

[0084] (Distillation)

[0085] In the purification method of the present invention, a distillation apparatus commonly used for distillation, such as a plate column, a packed column, or other distillation column, is used. Distillation composition and extraction solvent are supplied to this distillation column for extraction distillation. A distillation column made of carbon steel with an internally lined glass, stainless steel, or at least one of the following: tetrafluoroethylene resin, trichlorofluoroethylene resin, vinylidene fluoride resin, tetrafluoroethylene / perfluoroalkoxyethylene copolymer resin, etc., can be used.

[0086] The supply of the distillation composition and the extraction solvent to the distillation column can be arbitrary, as long as the distillation composition is distilled in the presence of the extraction solvent within the distillation column. They can be supplied either first or simultaneously. For example, the extraction solvent can be added to the distillation composition before it is supplied to the distillation column. However, from the viewpoint of distillation efficiency, it is preferable to supply the extraction solvent, etc., to the distillation column where the distillation composition is supplied, so that the distillation composition and the extraction solvent come into contact within the distillation column, and distillation is carried out simultaneously with mixing.

[0087] There are no particular restrictions on the various conditions of extractive distillation, such as operating temperature, operating pressure, reflux ratio, total number of sections in the distillation column, location of the addition section, and location of the extraction solvent supply section; these can be appropriately selected to achieve the separation objective. Since both 1224yd(Z) and 244bb have low boiling points, extractive distillation under pressure is preferred, for example, set to 0–5 × 10⁻⁵. 6 Pa, preferably set to 0~3×10 6 Pa, preferably set to 0~2×10 6 Pa (gauge pressure).

[0088] Furthermore, the temperatures at the top and bottom of the distillation column are determined based on the operating pressure and the composition of the distillate and the effluent. Considering the temperatures of the condensers and reheaters located at the top and bottom of the column, for economical distillation operations, the temperature at the top of the column is preferably set to -60 to 100°C, and the temperature at the bottom of the column is preferably set to 50 to 200°C. Extractive distillation can be carried out batchwise or continuously. Depending on the circumstances, it can also be a semi-continuous process where the distillate and effluent are extracted intermittently, or the distillation composition is fed in intermittently. However, the extraction solvent is preferably continuously supplied to the distillation column.

[0089] The first extraction solvent makes the relative volatility of 1224yd(Z) relative to 244bb greater than 1. Therefore, by extractive distillation of the distillation composition containing 1224yd(Z), 244bb, and the first extraction solvent, a distillate with a high content of 1224yd(Z) relative to the total amount of 1224yd(Z) and 244bb compared to the distillation composition is obtained from the top side of the distillation column, preferably a distillate with 1224yd(Z) as the main component.

[0090] Compared to the distillation composition, the distillate has a higher content of 1224yd(Z) relative to the total amount of 1224yd(Z) and 244bb. Preferably, the composition is not limited as long as 1224yd(Z) is included as the main component. The molar fraction (%) of 1224yd(Z) in the distillate relative to the total amount of 1224yd(Z) and 244bb is preferably 90 mol% or more. Furthermore, since the distillate contains the first extraction solvent, a purified product containing 1224yd(Z) at a higher concentration can be obtained by redistilling it.

[0091] Additionally, a bottom product containing 244bb is obtained from the bottom side of the distillation column. The bottom product also contains 1224yd(Z), but the molar fraction of 1224yd(Z) relative to the total of 1224yd(Z) and 244bb is significantly reduced compared to the total molar fraction of 1224yd(Z) relative to the total of 1224yd(Z) and 244bb in the distillation composition. Preferably, the molar fraction of 1224yd(Z) in the bottom product relative to the total of 1224yd(Z) and 244bb is reduced to, for example, less than 1 / 10 of the total molar fraction of 1224yd(Z) relative to the total of 1224yd(Z) and 244bb in the distillation composition.

[0092] Furthermore, since the effluent contains the first extraction solvent, by redistilling it and performing the same extraction distillation as described above, the molar fraction of 1224yd(Z) in the effluent relative to the total of 1224yd(Z) and 244bb can be further reduced.

[0093] Thus, in this embodiment, by using the first extraction solvent, at least a portion of 244bb is efficiently separated from the distillation composition into the distillate, yielding a purified product of 1224yd(Z) as the distillate. The content ratio of 1224yd(Z) relative to the total amount of 1224yd(Z) and 244bb is higher than that of the distillation composition, preferably containing 1224yd(Z) as the main component, i.e., containing 1224yd(Z) at a higher concentration. Both the first extraction solvent in the distillate and the first extraction solvent in the distillate can be separated by conventional distillation.

[0094] The second extraction solvent makes the relative volatility of 1224yd(Z) relative to 244bb less than 1. Therefore, by extractive distillation of the distillation composition containing 1224yd(Z), 244bb, and the second extraction solvent, a distillate with a high content of 244bb relative to the total amount of 1224yd(Z) and 244bb compared to the total amount of the distillation composition is obtained from the top side of the distillation column, preferably a distillate with 244bb as the main component.

[0095] At this point, the distillate also contains 1224yd(Z), but the mole fraction of 1224yd(Z) relative to the total of 1224yd(Z) and 244bb is significantly reduced compared to the total mole fraction of 1224yd(Z) relative to the total of 1224yd(Z) and 244bb in the distillate. Preferably, the mole fraction of 1224yd(Z) in the distillate relative to the total of 1224yd(Z) and 244bb is reduced to, for example, less than 1 / 10 of the total mole fraction of 1224yd(Z) relative to the total of 1224yd(Z) and 244bb in the distillate.

[0096] Furthermore, since the distillate contains a second extraction solvent, by redistilling it and performing the same extractive distillation as described above, the molar fraction of 1224yd(Z) in the distillate relative to the total of 1224yd(Z) and 244bb can be further reduced.

[0097] Furthermore, a bottom product containing 1224yd(Z) can be obtained from the bottom of the distillation column. Compared to the distillation composition, the bottom product has a higher content of 1224yd(Z) relative to the total amount of 1224yd(Z) and 244bb, preferably containing 1224yd(Z) as the main component, and more preferably having a mole fraction (%) of 1224yd(Z) relative to the total amount of 1224yd(Z) and 244bb of 90 mol% or more. In addition, since the bottom product contains a second extraction solvent, by redistilling it and performing the same extractive distillation as described above, the mole fraction of 244bb in the bottom product relative to the total amount of 1224yd(Z) and 244bb can be further reduced.

[0098] Thus, by using a second extraction solvent, 1224yd(Z) is efficiently separated from the distillation composition into the still product. Both the second extraction solvent in the still product and the second extraction solvent in the distillate can be separated by conventional distillation.

[0099] Example

[0100] The following embodiments illustrate the present invention in detail. However, the present invention is not limited to the following embodiments.

[0101] [Analysis Conditions]

[0102] In the following determinations of relative volatility, the composition of the resulting liquids was analyzed using gas chromatography (GC). A DB-1301 column (60 m length × 250 μm inner diameter × 1 μm thickness, manufactured by Agilent / Technology Co., Ltd.) was used.

[0103] [Determination of relative volatility]

[0104] Using an Osmer-type equilibrium distillation apparatus, 1224yd(Z), 244bb, and the extraction solvent were added and heated to boiling (approximately 50°C), then refluxed at atmospheric pressure. The mixing ratio of the extraction solvent, 1224yd(Z), and 244bb was 40:50:10 in all examples, expressed as extraction solvent:1224yd(Z):244bb. It should be noted that the mixing ratio of 224yd(Z) and 244bb without the extraction solvent was 50:10, expressed as 1224yd(Z):244bb. Heating was adjusted appropriately with a suitable dropwise rate of vapor-phase condensate, and the mixture was kept at a stable boiling state for 2 hours to confirm pressure and boiling point stability.

[0105] Subsequently, samples were collected from both the liquid and gas phases and analyzed by gas chromatography. Using the analytical results, the relative volatility of 1224yd(Z) relative to 244bb was calculated using the formula for relative volatility described above. For each example, the relative volatility of 1224yd(Z) relative to 244bb in a mixture containing 1224yd(Z), 244bb, and the extraction solvent is shown in Table 1.

[0106] [Table 1]

[0107]

[0108] Table 1 shows that AE3000 (CF3CH2OCF2CF2H), AC2000 (CF3CF2CF2CF2CF2CF2H), HCFC-234bb, and HCFC-225cb can be used as the first extraction solvent. That is, it can be seen that by using these as extraction solvents, the relative volatility of 1224yd(Z) relative to 244bb can be increased. Therefore, it can be seen that if these first extraction solvents are used for extractive distillation, the distillate from the distillation column will have a higher content ratio of 1224yd(Z) relative to the total amount of 1224yd(Z) and 244bb compared to the distillation composition; that is, a purified product containing 1224yd(Z) at a higher concentration can be obtained.

[0109] It is also known that DMF, THF, acetone, ethyl acetate, toluene, acetonitrile, carbon tetrachloride, methanol, trichloroethylene, chloroform, n-hexane, and CFO-1214ya can be used as a second extraction solvent. That is, it is known that by using these as extraction solvents, the relative volatility of 1224yd(Z) relative to 244bb can be reduced. Therefore, it is known that if extraction distillation is performed using these second extraction solvents, the content ratio of 1224yd(Z) relative to the total amount of 1224yd(Z) and 244bb in the distillation column effluent is higher than that of the distillation composition, i.e., a purified product containing 1224yd(Z) at a higher concentration can be obtained.

Claims

1. A method for purifying (Z)-1-chloro-2,3,3,3-tetrafluoropropene, comprising separating at least a portion of 2-chloro-1,1,1,2-tetrafluoropropene from a composition comprising (Z)-1-chloro-2,3,3,3-tetrafluoropropene and 2-chloro-1,1,1,2-tetrafluoropropane by distillation in the presence of an extraction solvent. The extraction solvent is either a first extraction solvent having a relative volatility of (Z)-1-chloro-2,3,3,3-tetrafluoropropene relative to 2-chloro-1,1,1,2-tetrafluoropropane of 1.02 or higher, or a second extraction solvent having a relative volatility of (Z)-1-chloro-2,3,3,3-tetrafluoropropene relative to 2-chloro-1,1,1,2-tetrafluoropropane of 0.98 or lower. The first extraction solvent is at least one compound selected from the group consisting of CF3CH2OCF2CF2H and CF3CF2CF2CF2CF2H. The second extraction solvent is at least one compound selected from the group consisting of N,N-dimethylformamide, tetrahydrofuran, acetone, ethyl acetate, toluene, acetonitrile, carbon tetrachloride, methanol, trichloroethylene, chloroform, n-hexane, and 1,1-dichloro-2,3,3,3-tetrafluoropropene. The amount of the extraction solvent is in the range of 0.1:1 to 1000:1, expressed as the molar ratio of extraction solvent to 2-chloro-1,1,1,2-tetrafluoropropane.

2. The purification method according to claim 1, wherein, The molar amount of (Z)-1-chloro-2,3,3,3-tetrafluoropropene in the composition is in the ratio of 1 to 99 moles to the total molar amount of (Z)-1-chloro-2,3,3,3-tetrafluoropropene and 2-chloro-1,1,1,2-tetrafluoropropane.

3. The purification method according to claim 1 or 2, wherein, The extraction solvent is a second extraction solvent in which the relative volatility of (Z)-1-chloro-2,3,3,3-tetrafluoropropene relative to 2-chloro-1,1,1,2-tetrafluoropropane is less than 0.

96.

4. The purification method according to claim 1 or 2, wherein, The extraction solvent is at least one compound selected from the group consisting of N,N-dimethylformamide, tetrahydrofuran, acetone, ethyl acetate, toluene, acetonitrile, carbon tetrachloride, and methanol.

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