Method for recovering ionic liquid

Abstract

Provided is a method for simply and efficiently recovering an ionic liquid from a liquid mixture including the ionic liquid and an organic acid.　This method for recovering an ionic liquid from a liquid mixture including the ionic liquid and an organic acid is characterized in that the ionic liquid is water-soluble, at least one of water and an organic solvent (excluding organic acids) is blended into the liquid mixture, and the organic acid is separated by extraction.

Description

Method for recovering ionic liquid

[0001] The present disclosure relates to a method for recovering ionic liquids by extraction.

[0002] In recent years, ionic liquids have been proposed as solvents for dissolving biomass containing polysaccharides such as cellulose and lignocellulose (hereinafter sometimes referred to as "polysaccharide-containing biomass"), and a technology has been introduced that uses such ionic liquids to derivatize polysaccharides in a homogeneous reaction. Ionic liquids have extremely low volatility, do not pose the risk of contamination or ignition due to evaporation, and have a strong ability to dissolve cellulose and other substances, so research and development is underway to use them as solvents for processing polysaccharides.

[0003] For example, Example 1 of Patent Document 1 describes that 120 mg of bagasse (sugarcane residue) was dissolved in 4 g of 1-ethyl-3-methylimidazolium acetate, an ionic liquid (bagasse concentration in the ionic liquid: 3 wt %), and the solution was dried under vacuum overnight at 80°C with stirring, and then 4 mL of isopropenyl acetate was added to the reaction system, and the resulting reaction solution was reprecipitated with methanol and filtered to obtain a solid polysaccharide derivative (cellulose acetate).

[0004] Since ionic liquids are very expensive, methods for recovering and reusing them after the reaction have been investigated. For example, Patent Document 2 describes a method for separating and recovering an ionic liquid from a mixed solution containing two or more solutes, including an ionic liquid, using an ion exchange membrane. Patent Document 3 describes a method for separating and recovering an ionic liquid having a quaternary ammonium skeleton with an alkoxyalkyl group as the cation component or a nitrogen-containing heterocyclic five-membered skeleton with an alkoxyalkyl group and an amino group as the anion component, by crystallizing the ionic liquid and then washing with a solvent such as ethyl acetate. Patent Document 4 describes a method for separating and recovering an ionic liquid containing impurities by dissolving the ionic liquid in a mixed solvent of a polar aprotic organic solvent and a nonpolar organic solvent, followed by lowering the temperature of the solution to crystallize the ionic liquid from the solution. Patent Document 5 describes a method for purifying an ionic liquid, in which the ionic liquid is partially crystallized from the melt and the crystalline product is separated from the remaining melt.

[0005] International Publication No. 2016 / 068053 JP 2015-96255 A JP 2012-144441 A JP 2010-184902 A JP 2008-523005 A

[0006] However, as in Patent Document 1, when cellulose acetate is produced from polysaccharide-containing biomass, the esterification reaction of the polysaccharide-containing biomass is carried out in the presence of polysaccharide-containing biomass and an esterifying agent as raw materials and an ionic liquid as a solvent. However, an organic acid derived from the esterifying agent is generated as a by-product of the reaction. Therefore, the reaction solution after the esterification reaction is a mixture containing the organic acid and the ionic liquid. Although the reason for this is not clear, it has been difficult to separate and recover the ionic liquid from such a mixture, possibly due to an interaction between the organic acid and the ionic liquid.

[0007] Therefore, an object of the present disclosure is to provide a method for simply and efficiently recovering an ionic liquid from a mixed liquid containing an ionic liquid and an organic acid.

[0008] As a result of intensive research aimed at solving the above-mentioned problems, the inventors of the present disclosure have found that the ionic liquid can be recovered simply and efficiently by adding at least one selected from the group consisting of water and an organic solvent to a mixed liquid containing the ionic liquid and an organic acid and then extracting the mixed liquid. The invention of the present disclosure was completed based on these findings.

[0009] That is, the present disclosure provides a method for recovering an ionic liquid from a mixed liquid containing an ionic liquid and an organic acid, wherein the ionic liquid is water-soluble, the method comprising blending at least one selected from the group consisting of water and organic solvents (excluding organic acids) with the mixed liquid, and separating the organic acid by extraction.

[0010] The ionic liquid preferably contains an imidazolium cation or a quaternary ammonium cation as a cationic component.

[0011] The ionic liquid preferably contains a carboxylate anion as the anion component.

[0012] The organic acid is preferably a carboxylic acid.

[0013] The organic solvent is preferably at least one selected from the group consisting of ethers, ketones, esters, aryls, alkanes, and cycloalkanes.

[0014] The organic solvent is preferably at least one selected from the group consisting of ethers, ketones, and esters.

[0015] The organic acid is C 1-7 Preferably, the carboxylic acid is

[0016] According to the method for recovering an ionic liquid of the present disclosure, the ionic liquid can be recovered simply and efficiently from a mixed liquid containing an ionic liquid and an organic acid.

[0017] The method for recovering an ionic liquid according to the present disclosure is a method for recovering an ionic liquid from a mixed solution containing an ionic liquid and an organic acid, wherein the ionic liquid is water-soluble, and the mixed solution is blended with at least one organic solvent selected from the group consisting of water and an organic solvent (excluding organic acids), and the organic acid is separated by extraction. Hereinafter, the method for recovering an ionic liquid according to the present disclosure may be referred to as the "method of the present disclosure." Furthermore, the at least one organic solvent selected from the group consisting of water and an organic solvent (excluding organic acids) may be referred to as water and / or an organic solvent (excluding organic acids).

[0018] [Mixed Liquid] The mixed liquid (A) and the mixed liquid (B) will be described below. In this specification, a mixed liquid containing an ionic liquid and an organic acid will be referred to as mixed liquid (B). In addition, in this specification, a mixed liquid containing an ionic liquid, an organic acid, water, and an organic solvent (excluding organic acids) will be referred to as mixed liquid (A). The mixed liquid (A) contains an ionic liquid, an organic acid, water, and an organic solvent (excluding organic acids), and is not particularly limited as long as the ionic liquid is water-soluble. However, it is preferable that water and / or an organic solvent (excluding organic acids) is blended with the mixed liquid (B) containing the ionic liquid and an organic acid. The mixed liquid (B) contains an ionic liquid and an organic acid, and is not particularly limited as long as the ionic liquid is water-soluble. However, it may be, for example, a mixed liquid (hereinafter, sometimes referred to as "mixed liquid (B1)") containing a reaction product obtained when using an ionic liquid as a solvent and esterifying a specific raw material with an esterifying agent or the like. The mixed liquid (B1) contains, for example, the target esterified product (the esterified product of the raw material), an organic acid derived from the esterifying agent, and an ionic liquid. The mixed liquid (B1) may further contain unreacted raw materials, unreacted esterifying agent, by-products other than the organic acid, a solvent other than the ionic liquid, and the like. The mixed liquid (B1) may also be one from which some or all of the components other than the ionic liquid and the organic acid have been removed by a known or conventional method. That is, the mixed liquid (B1) may contain at least the organic acid derived from the esterifying agent and the ionic liquid.

[0019] The mixed liquid (B1) will be described below in the case where the raw material is a polysaccharide. That is, the mixed liquid (B) refers to an embodiment in which the mixed liquid (B) is a mixed liquid obtained by esterifying a polysaccharide with an esterifying agent using an ionic liquid as a solvent (hereinafter, sometimes referred to as "mixed liquid (B2)"). The mixed liquid (B2) contains, for example, an esterified product of the target polysaccharide, an organic acid derived from the esterifying agent, and an ionic liquid. The mixed liquid (B2) may further contain unreacted polysaccharide, unreacted esterifying agent, by-products other than the organic acid, a solvent other than the ionic liquid, and the like. Furthermore, the mixed liquid (B2) may be one from which some or all of the components other than the ionic liquid and the organic acid have been removed by a known or conventional method.

[0020] To summarize the above, the mixed liquid (B1) is an example of a specific embodiment of the mixed liquid (B), and is a mixed liquid (B) that uses an ionic liquid as a solvent and contains a reaction product obtained when a specific raw material is esterified with an esterifying agent or the like; the mixed liquid (B2) is an example of a more specific embodiment of the mixed liquid (B1), and is a mixed liquid (B) in which the raw material to be esterified with the esterifying agent is a polysaccharide; and the mixed liquid (B) is a mixed liquid that conceptually encompasses the mixed liquid (B1) and the mixed liquid (B2). Here, it should be noted again that in this embodiment, the mixed liquid (B) is not limited to the mixed liquid (B1) or the mixed liquid (B2).

[0021] Hereinafter, the raw materials, the esterifying agent, the ionic liquid, and the solvent other than the ionic liquid when the mixed liquid (B) is the mixed liquid (B1) will be described in detail.

[0022] <Raw Material> First, the raw material will be described. The raw material refers to the starting material to be esterified by the esterifying agent. The raw material is preferably a polysaccharide. Here, as described above, when the raw material is a polysaccharide, the mixed liquid (B1) refers to the mixed liquid (B2). The polysaccharide may be biomass containing a polysaccharide (polysaccharide-containing biomass). The polysaccharide-containing biomass is not particularly limited as long as it contains a polysaccharide, and examples thereof include bagasse (sugarcane residue); kenaf; wood such as cedar, eucalyptus, red pine, poplar, lauan, cypress, macumba, and Sitka spruce; shells of crustaceans such as crabs and shrimp; grains such as rice, wheat, corn, and sorghum; tubers such as potato, sweet potato, and cassava; and other cellulosic plant-derived materials (pulp waste liquor, rice straw, rice husks, fruit fiber, fruit kernel shells such as ginkgo nuts, and empty fruit bunches). Pulp or the like obtained by refining these biomasses can also be used. The polysaccharide-containing biomass may be in the form of a polysaccharide after being subjected to various pretreatments such as cutting and drying as necessary, followed by a process of separating and extracting polysaccharides (e.g., cellulose). Only one type of polysaccharide may be used, or two or more types may be used.

[0023] The polysaccharides are not particularly limited, but examples thereof include cellulose, hemicellulose, xylan, mannan, glucomannan, glucuronoxylan, starch, amylose, amylopectin, glycogen, dextrin, pectin, chitin, chitosan, agarose, carrageenan, isolichenan, laminaran, lichenan, glucan, inulin, levan, fructan, galactan, arabinan, pentosan, alginic acid, pectinic acid, protuberic acid, colominic acid, porphyran, fucoidan, ascophyllan, locust bean gum, guar gum, tamarind gum, tara gum, and gum arabic.

[0024] <Esterification Agent> Next, the esterification agent will be described. The esterification agent is a compound for esterifying raw materials such as polysaccharides. The esterification agent is not particularly limited, and a compound corresponding to the type of target esterification product can be appropriately selected and used. Among these, the esterification agent is preferably one or more selected from the group consisting of linear ester compounds, cyclic ester compounds, unsaturated aldehydes, saturated aldehydes, acid halides, acid anhydrides, and allyl alcohols. Among these, acid anhydrides are preferred from the viewpoints of ease of handling and the yield of the obtained esterification product. The esterification agent can be used alone or in combination of two or more.

[0025] The chain ester compound is not particularly limited, but examples thereof include alkyl carboxylates such as methyl acetate, and alkenyl carboxylates such as isopropenyl acetate and vinyl acetate.

[0026] The cyclic ester compound is not particularly limited, but examples thereof include lactones such as β-propiolactone, δ-valerolactone, γ-butyrolactone, ε-caprolactone, α,α-dimethyl-β-propiolactone, β-ethyl-δ-valerolactone, α-methyl-ε-caprolactone, β-methyl-ε-caprolactone, γ-methyl-ε-caprolactone, and 3,3,5-trimethyl-ε-caprolactone; and lactides such as glycolide and lactide.

[0027] The unsaturated aldehyde is not particularly limited, but examples thereof include aromatic aldehydes such as 2-butenal, 2-hexenal, 2-decenal, 2-undecenal, 2-dienal, 2,4-heptadienal, 2,4-decadienal, cinnamaldehyde, and benzaldehyde.

[0028] The saturated aldehyde is not particularly limited, but examples thereof include propanal, hexanal, octanal, and nonanal.

[0029] The acid halide is not particularly limited, and examples thereof include carboxylic acid halides such as carboxylic acid fluorides, carboxylic acid chlorides, carboxylic acid bromides, carboxylic acid iodides, etc. Specific examples of carboxylic acid halides include acetyl fluoride, acetyl chloride, acetyl bromide, acetyl iodide, propionyl fluoride, propionyl chloride, propionyl bromide, propionyl iodide, butyryl fluoride, butyryl chloride, butyryl bromide, butyryl iodide, benzoyl fluoride, benzoyl chloride, benzoyl bromide, and benzoyl iodide.

[0030] The acid anhydride is not particularly limited, but examples thereof include acetic anhydride, propionic anhydride, butyric anhydride, valeric anhydride, caproic anhydride, enanthic anhydride, caprylic anhydride, pelargonic anhydride, capric anhydride, lauric anhydride, myristic anhydride, palmitic anhydride, stearic anhydride, oleic anhydride, linoleic anhydride, linolenic anhydride, benzoic anhydride, phthalic anhydride, maleic anhydride, succinic anhydride, etc. Among these, acetic anhydride is particularly preferred.

[0031] The allyl alcohol is not particularly limited, but examples thereof include methallyl alcohol, acrylic alcohol, 2-hydroxymethyl-1-butene, and α-hydroxymethylstyrene.

[0032] <Ionic Liquid> Next, an ionic liquid will be described. An ionic liquid is a solvent (particularly a solvent for dissolving raw materials) for dissolving and / or dispersing raw materials (e.g., polysaccharides). Specific examples of ionic liquids are described later in the section [Ionic Liquid]. Therefore, specific examples of ionic liquids will be omitted here. As the ionic liquid, each of the specific ionic liquids exemplified in the section [Ionic Liquid] can be used.

[0033] <Solvents other than ionic liquids [Solvent (S)]> Next, solvents other than ionic liquids will be described. Herein, in this specification, the above solvents may be referred to as "solvents (S)." Solvent (S) is a solvent that, when used together with an ionic liquid, can further demonstrate the function of dissolving and / or dispersing raw materials, and is also referred to as a co-solvent for the ionic liquid.

[0034] The solvent (S) is not particularly limited, but can be appropriately selected in consideration of its compatibility with the ionic liquid. Furthermore, when the raw material is a polysaccharide, i.e., when the mixed liquid (B) is a mixed liquid obtained by esterifying a polysaccharide, the solvent (S) can be appropriately selected in consideration of its affinity with the polysaccharide or the esterified product of the polysaccharide, the viscosity of the mixture of the polysaccharide and the ionic liquid, and the like. Furthermore, the solvent (S) is preferably one that does not react with the ionic liquid and has high solubility in the polysaccharide and the esterified product of the polysaccharide when mixed with the ionic liquid. Only one type of solvent (S) may be used, or two or more types may be used.

[0035] Specific examples of the solvent (S) include nitriles such as acetonitrile; sulfoxides such as dimethyl sulfoxide (DMSO); sulfones such as cyclic sulfones (e.g., sulfolane); ethers such as cyclic ethers (e.g., 1,3-dioxolane, 1,4-dioxane, tetrahydrofuran); amides such as N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMAc); lactams such as N-methyl-2-pyrrolidone (NMP); lactones such as γ-butyrolactone; and amines such as pyridine. Among these, from the viewpoint of compatibility with the ionic liquid and the solubility of the esterified product of the polysaccharide, the solvent (S) is preferably at least one selected from the group consisting of sulfoxides, sulfones, amides, and lactams, more preferably at least one selected from the group consisting of dimethyl sulfoxide (DMSO), sulfolane, N,N-dimethylformamide (DMF), and N-methyl-2-pyrrolidone (NMP), still more preferably at least one selected from the group consisting of N,N-dimethylformamide (DMF) and N-methyl-2-pyrrolidone (NMP), and particularly preferably N-methyl-2-pyrrolidone (NMP).

[0036] The organic solvent to be blended in the mixed solution (B) can also be used as the solvent (S). When an organic solvent is used as the solvent (S), the extraction operation can be carried out without blending (adding) an organic solvent to the obtained mixed solution (B1), which is preferable from the viewpoint of avoiding complicated operations.

[0037] The above is a detailed description of the raw materials, the esterifying agent, the ionic liquid, and the solvent other than the ionic liquid when the mixed liquid (B) is the mixed liquid (B1).

[0038] [Extraction] The method of the present disclosure is characterized by separating the ionic liquid and the organic acid by an extraction step for a mixed liquid (B) containing an ionic liquid and an organic acid. Specifically, water and / or an organic solvent (excluding the organic acid) is added to the mixed liquid (B) to produce the mixed liquid (A) while contacting the water with the organic solvent, and the ionic liquid and the organic acid are separated using the resulting mixed liquid (A). This series of operations is referred to as extraction. Hereinafter, the organic solvent (excluding the organic acid) will also be referred to as the organic solvent (Or), as described below. The extraction operation of the present disclosure is a liquid-liquid extraction.

[0039] That is, the method of the present disclosure is characterized in that, during extraction, water and / or the organic solvent (Or) is added to a mixed solution (B) containing at least an ionic liquid and an organic acid. The method of adding water and / or the organic solvent (Or) to the mixed solution (B), i.e., the method of preparing the mixed solution (A), is not particularly limited. For example, methods for preparing the mixed liquid (A) include: [1] a method for preparing the mixed liquid (A) by adding the organic solvent (Or) to a mixed liquid (B) containing an ionic liquid, an organic acid, and water; [2] a method for preparing the mixed liquid (A) by adding water and the organic solvent (Or) to a mixed liquid (B) containing an ionic liquid, an organic acid, and water; [3] a method for preparing the mixed liquid (A) by adding water to a mixed liquid (B) containing an ionic liquid, an organic acid, and the organic solvent (Or); [4] a method for preparing the mixed liquid (A) by adding water and the organic solvent (Or) to a mixed liquid (B) containing an ionic liquid, an organic acid, and the organic solvent (Or); [5] a method for preparing the mixed liquid (A) by adding water and the organic solvent (Or) to a mixed liquid (B) containing an ionic liquid and an organic acid; and [6] a method for preparing the mixed liquid (A) by adding water to a mixed liquid containing an ionic liquid, an organic acid, water, and the organic solvent (Or). [7] A method of preparing a mixed solution (A) by adding the organic solvent (Or) to a mixed solution containing an ionic liquid, an organic acid, water, and the organic solvent (Or); or [8] A method of preparing a mixed solution (A) by adding water and the organic solvent (Or) to a mixed solution containing an ionic liquid, an organic acid, water, and the organic solvent (Or). The water and / or organic solvent (Or) may be blended (added) after mixing the ionic liquid and the organic acid, or may be mixed all at once with the ionic liquid and the organic acid. When the mixed solution (B) is the mixed solution (B1), water and / or the organic solvent (Or) may be blended (added) to a system before the esterification reaction of a specific raw material to carry out various reactions, resulting in the mixed solution containing at least one selected from the group consisting of water and the organic solvent (Or). Alternatively, the mixed solution may be prepared by blending (adding) at least one selected from the group consisting of water and the organic solvent (Or) to the mixed solution after the reaction (i.e., the mixed solution (B1)).

[0040] In the method of the present disclosure, the mixed solution (B) may be subjected to extraction directly (i.e., without pretreatment), or the mixed solution (B) may be subjected to pretreatment and then extraction. Examples of such pretreatment include treatment with a strong acid such as sulfuric acid, hydrochloric acid, or nitric acid. Pretreatment with a strong acid may convert the ionic liquid in the mixed solution (B) into a strong acid salt, which may increase the amount of ionic liquid that moves to the aqueous phase after subsequent extraction. However, in the method of the present disclosure, since the mixed solution (B) contains specific components, organic acids can be separated by extraction, resulting in the effect of easily and efficiently recovering the ionic liquid. In other words, the method of the present disclosure achieves the above-described effective effect without requiring the pretreatment. Therefore, it is preferable to perform the extraction on the mixed solution (B) directly (i.e., without pretreatment). In other words, it is preferable that the structural formula of the ionic liquid recovered by the method of the present disclosure is the same as the structural formula of the ionic liquid (in the mixed solution (B)) before extraction.

[0041] The ionic liquid and the organic acid are separated by extracting the mixed liquid (B). Alternatively, the ionic liquid and the organic acid may be separated by blending water and / or an organic solvent (Or) with the mixed liquid (B) and extracting the mixture. Here, it is preferable that the organic acid is extracted into the organic solvent phase (oil phase), and the ionic liquid is extracted into the aqueous phase. This allows the ionic liquid to be recovered in a form separated from the organic acid. Specifically, the mixture of the ionic liquid and water is finally recovered by, for example, distilling it.

[0042] The operation of recovering the ionic liquid by extraction with the mixed liquid (B) (extraction operation) can be carried out using an apparatus that brings the aqueous phase and the oil phase (organic solvent phase) into contact with each other, such as a mixer-settler extraction column, a perforated plate type, a packed column type, a baffle column type, a vibrating perforated plate type, a stirring and mixing type, a pulsating packed type, or a centrifugal extraction type.

[0043] The temperature at which the mixed liquid (B) is extracted is not particularly limited, but is, for example, preferably 0 to 100°C, more preferably 1 to 90°C, even more preferably 3 to 80°C, and particularly preferably 5 to 70°C.

[0044] The pressure when extracting the mixed liquid (B) is not particularly limited, but is preferably, for example, 10 to 2000 hPa, more preferably 100 to 1500 hPa, and even more preferably 500 to 1200 hPa (for example, normal pressure).

[0045] The extraction procedure allows the ionic liquid to be separated from the mixed liquid (B). Generally, the extraction procedure yields an aqueous phase containing mainly the ionic liquid and water, and an oil phase containing mainly an organic acid and an organic solvent. The ionic liquid can also be separated from the aqueous phase containing the ionic liquid and water by a known or conventional purification method, such as evaporation of water. In other words, the method of the present disclosure allows high-purity ionic liquid to be obtained by the simple method of extraction.

[0046] [Ionic Liquid] Next, the ionic liquid will be described. The ionic liquid is a liquid component separated from the organic acid by the above-mentioned extraction operation (extraction step). Furthermore, when the mixed liquid (B) is the mixed liquid (B1), the ionic liquid is also a solvent (particularly a solvent for dissolving the raw material) for dissolving and / or dispersing the raw material (e.g., polysaccharides). The ionic liquid of the present disclosure is water-soluble.

[0047] The ionic liquid of the present disclosure is not particularly limited as long as it is a water-soluble ionic liquid, and may be, for example, at least one water-soluble ionic liquid selected from the group consisting of acidic ionic liquids, neutral ionic liquids, and basic ionic liquids. In this specification, "ionic liquid" refers to a salt composed of a cation component and an anion component, and its liquidity can be specified by the acid dissociation constant (pKa, calculated value in vacuum) of the conjugate acid of the anion. For example, basic ionic liquids have an acid dissociation constant of 2 to 19. Only one type of ionic liquid may be used, or two or more types may be used.

[0048] Cationic Component Examples of the cationic component in the ionic liquid include imidazolium cation, pyridinium cation, pyrrolidinium cation, piperidinium cation, quaternary ammonium cation, and quaternary phosphonium cation.

[0049] Examples of the imidazolium cation include cations represented by the following formula (1): The cation represented by formula (1) also includes its tautomers and cations represented by structural formulas that have a resonance relationship with formula (1).

[0050]

[0051] In formula (1), R 1 and R 3 are the same or different and are a substituted or unsubstituted alkyl group, alkenyl group, alkoxyalkyl group, or substituted or unsubstituted phenyl group, R 2 , R 4 , and R 5 are the same or different and are a hydrogen atom, a substituted or unsubstituted alkyl group, an alkenyl group, an alkoxyalkyl group, or a substituted or unsubstituted phenyl group.

[0052] R 1 ~R 5Examples of the substituted or unsubstituted alkyl group in the formula (I) include linear or branched alkyl groups having 1 to 20 (preferably 1 to 10, more preferably 2 to 6, and even more preferably 2 to 4) carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, butyl, hexyl, and octyl groups. These alkyl groups may have a sulfo group bonded to the terminal. Examples of the alkenyl group include linear or branched alkenyl groups having 2 to 20 (preferably 2 to 10, more preferably 2 to 6, and even more preferably 2 to 4) carbon atoms, such as vinyl, 1-propenyl, 2-propenyl, 1-butenyl, 2-butenyl, 1-pentenyl, 2-pentenyl, 1-hexenyl, 2-hexenyl, and 1-octenyl groups. Examples of the alkoxyalkyl group include a straight-chain or branched alkoxyalkyl group having 2 to 20 (preferably 2 to 10, more preferably 2 to 6, and even more preferably 2 to 4) carbon atoms, such as a methoxymethyl group, an ethoxymethyl group, a 1-methoxyethyl group, a 2-methoxyethyl group, a 1-ethoxyethyl group, or a 2-ethoxyethyl group. Examples of the substituted or unsubstituted phenyl group include a phenyl group which may be substituted with 1 to 2 groups selected from a hydroxyl group, a halogen atom, a lower alkoxy group, a lower alkenyl group, a methylsulfonyloxy group, a substituted or unsubstituted lower alkyl group, a substituted or unsubstituted amino group, a substituted or unsubstituted phenyl group, a substituted or unsubstituted phenoxy group, and a substituted or unsubstituted pyridyl group.

[0053] R 1 and R 3 is preferably an alkyl group, an alkenyl group, or a substituted or unsubstituted phenyl group, and more preferably a linear alkyl group having 1 to 6 carbon atoms. 1 and R 3 It is particularly preferred that one of R is a linear alkyl group having 1 to 4 carbon atoms and the other is a linear alkyl group having 2 to 6 carbon atoms, and the numbers of carbon atoms of these alkyl groups are different. 2 , R 4 and R 5is preferably a hydrogen atom, an alkyl group, an alkenyl group, or a substituted or unsubstituted phenyl group, and more preferably a hydrogen atom or an alkyl group.

[0054] Examples of the imidazolium cation include imidazolium cations such as 1,3-dimethylimidazolium, 1-ethyl-3-methylimidazolium, 1-butyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium, 1-octyl-3-methylimidazolium, 1-decyl-3-methylimidazolium, 1-tetradecyl-3-methylimidazolium, 1-hexadecyl-3-methylimidazolium, 1-octadecyl-3-methylimidazolium, 1-allyl-3-methylimidazolium, 1-ethyl-2,3-dimethylimidazolium, 1-butyl-2,3-dimethylimidazolium, and 1-hexyl-2,3-dimethylimidazolium. Among these, the 1-ethyl-3-methylimidazolium cation (Emidazolium + ) is particularly preferred.

[0055] Examples of the pyridinium cation include cations represented by the following formula (2): The cation represented by formula (2) also includes its tautomers and cations represented by structural formulas that have a resonance relationship with formula (2).

[0056]

[0057] In formula (2), R 6 is an alkyl group, an alkenyl group, an alkoxyalkyl group, or a substituted or unsubstituted phenyl group, and R 7 ~R 11 are the same or different and are a hydrogen atom, an alkyl group, an alkenyl group, an alkoxyalkyl group, or a substituted or unsubstituted phenyl group.

[0058] R 6 ~R 11 The alkyl group, alkenyl group, alkoxyalkyl group, and substituted or unsubstituted phenyl group in the formula (1) are R 1 ~R 5 Examples of the same are as those described above.

[0059] R 6 is preferably an alkyl group, more preferably a linear alkyl group having 1 to 6 carbon atoms. 6 ~R 11 is preferably a hydrogen atom or an alkyl group, more preferably a hydrogen atom.

[0060] Examples of the pyridinium cation include pyridinium cations such as 1-ethylpyridinium, 1-butylpyridinium, 1-hexylpyridinium, 1-butyl-4-methylpyridinium, 1-butyl-3-methylpyridinium, 1-hexyl-4-methylpyridinium, 1-hexyl-3-methylpyridinium, 1-octyl-4-methylpyridinium, 1-octyl-3-methylpyridinium, 1-butyl-3,4-dimethylpyridinium, and 1-butyl-3,5-dimethylpyridinium, and among these, the 1-octyl-4-methylpyridinium cation is particularly preferred.

[0061] Examples of the pyrrolidinium cation include cations represented by the following formula (3): The cation represented by formula (3) also includes its tautomers.

[0062]

[0063] In formula (3), R 12 and R 13 are the same or different and are an alkyl group, an alkenyl group, an alkoxyalkyl group, or a substituted or unsubstituted phenyl group; R 14 ~R 21 are the same or different and are a hydrogen atom, an alkyl group, an alkenyl group, an alkoxyalkyl group, or a substituted or unsubstituted phenyl group.

[0064] R 12 ~R 21 The alkyl group, alkenyl group, alkoxyalkyl group, and substituted or unsubstituted phenyl group in the formula (1) are R 1 ~R 5 Examples of the same are as those described above.

[0065] R 12and R 13 is preferably an alkyl group, more preferably a linear alkyl group having 1 to 6 carbon atoms. 14 ~R 21 is preferably a hydrogen atom or an alkyl group, more preferably a hydrogen atom.

[0066] As the pyrrolidinium cation, a 1-butyl-1-methylpyrrolidinium cation is particularly preferred.

[0067] The piperidinium cation includes a cation represented by the following formula (4): The cation represented by formula (4) also includes its tautomers.

[0068]

[0069] In formula (4), R 22 and R 23 are the same or different and are an alkyl group, an alkenyl group, an alkoxyalkyl group, or a substituted or unsubstituted phenyl group; R 24 ~R 33 are the same or different and are a hydrogen atom, an alkyl group, an alkenyl group, an alkoxyalkyl group, or a substituted or unsubstituted phenyl group.

[0070] R 22 ~R 33 The alkyl group, alkenyl group, alkoxyalkyl group, and substituted or unsubstituted phenyl group in the formula (1) are R 1 ~R 5 Examples of the same are as those described above.

[0071] R 22 and R 23 is preferably an alkyl group, more preferably a linear alkyl group having 1 to 6 carbon atoms. 24 ~R 33 is preferably a hydrogen atom or an alkyl group, more preferably a hydrogen atom.

[0072] The piperidinium cation is preferably a 1-butyl-1-methylpiperidinium cation.

[0073] Examples of the quaternary ammonium cation include ammonium cations represented by the following formula (5): The cation represented by formula (5) also includes its tautomers.

[0074]

[0075] In formula (5), R 34 ~R 37 are the same or different and are an alkyl group, an alkenyl group, an alkoxyalkyl group, or a substituted or unsubstituted phenyl group.

[0076] R 34 ~R 37 Examples of the alkyl group in the formula (I) include a linear or branched alkyl group having 1 to 20 (preferably 1 to 10, more preferably 2 to 6, and even more preferably 2 to 4) carbon atoms, such as a methyl group, ethyl group, n-propyl group, isopropyl group, butyl group, hexyl group, or octyl group. Examples of the alkenyl group include a linear or branched alkenyl group having 2 to 20 (preferably 2 to 10, more preferably 2 to 6, and even more preferably 2 to 4) carbon atoms, such as a vinyl group, 1-propenyl group, 2-propenyl group, 1-butenyl group, 2-butenyl group, 1-pentenyl group, 2-pentenyl group, 1-hexenyl group, 2-hexenyl group, or 1-octenyl group. Examples of the alkoxyalkyl group include a straight-chain or branched alkoxyalkyl group having 2 to 20 (preferably 2 to 10, more preferably 2 to 6, and even more preferably 2 to 4) carbon atoms, such as a methoxymethyl group, an ethoxymethyl group, a 1-methoxyethyl group, a 2-methoxyethyl group, a 1-ethoxyethyl group, or a 2-ethoxyethyl group. Examples of the substituted or unsubstituted phenyl group include a phenyl group which may be substituted with 1 to 2 groups selected from a hydroxyl group, a halogen atom, a lower alkoxy group, a lower alkenyl group, a methylsulfonyloxy group, a substituted or unsubstituted lower alkyl group, a substituted or unsubstituted amino group, a substituted or unsubstituted phenyl group, a substituted or unsubstituted phenoxy group, and a substituted or unsubstituted pyridyl group.

[0077] R 34~R 37 is preferably an alkyl group, more preferably a straight-chain alkyl group having 1 to 6 carbon atoms.

[0078] Examples of the quaternary ammonium cation include ammonium cations such as trimethylpropylammonium, trimethylbutylammonium, triethylmethylammonium, trioctylmethylammonium, tetramethylammonium, tetraethylammonium, tetrabutylammonium, tetrapentylammonium, and tetrahexylammonium.

[0079] Examples of the quaternary phosphonium cation include phosphonium cations represented by the following formula (6): The cation represented by formula (6) also includes its tautomers.

[0080]

[0081] In formula (6), R 38 ~R 41 are the same or different and are an alkyl group, an alkenyl group, an alkoxyalkyl group, or a substituted or unsubstituted phenyl group.

[0082] R 38 ~R 41Examples of the alkyl group in the formula (I) include a linear or branched alkyl group having 1 to 20 (preferably 1 to 10, more preferably 2 to 6, and even more preferably 2 to 4) carbon atoms, such as a methyl group, ethyl group, n-propyl group, isopropyl group, butyl group, hexyl group, or octyl group. Examples of the alkenyl group include a linear or branched alkenyl group having 2 to 20 (preferably 2 to 10, more preferably 2 to 6, and even more preferably 2 to 4) carbon atoms, such as a vinyl group, 1-propenyl group, 2-propenyl group, 1-butenyl group, 2-butenyl group, 1-pentenyl group, 2-pentenyl group, 1-hexenyl group, 2-hexenyl group, or 1-octenyl group. Examples of the alkoxyalkyl group include a straight-chain or branched alkoxyalkyl group having 2 to 20 (preferably 2 to 10, more preferably 2 to 6, and even more preferably 2 to 4) carbon atoms, such as a methoxymethyl group, an ethoxymethyl group, a 1-methoxyethyl group, a 2-methoxyethyl group, a 1-ethoxyethyl group, or a 2-ethoxyethyl group. Examples of the substituted or unsubstituted phenyl group include a phenyl group which may be substituted with 1 to 2 groups selected from a hydroxyl group, a halogen atom, a lower alkoxy group, a lower alkenyl group, a methylsulfonyloxy group, a substituted or unsubstituted lower alkyl group, a substituted or unsubstituted amino group, a substituted or unsubstituted phenyl group, a substituted or unsubstituted phenoxy group, and a substituted or unsubstituted pyridyl group.

[0083] Examples of the quaternary phosphonium cation include quaternary phosphonium cations such as tetramethylphosphonium, tetraethylphosphonium, tetrabutylphosphonium, tetrahexylphosphonium, tetraoctylphosphonium, triethylmethylphosphonium, and tributylethylphosphonium.

[0084] Anion Component Examples of the anion component in the ionic liquid of the present disclosure include halogen anions, pseudohalogen anions, carboxylate anions, phosphate anions, amino acid anions, phenolates, pyrimidine olates, and tetrafluoroborate ions (BF 4- ), sulfomethyl ion (CH3SO3- ), methylphosphonate, sulfate ion, PF6 - etc.

[0085] The halogen anion is not particularly limited, but for example, a fluoride ion (F - ), chloride ions (Cl - ), iodine ion (I - ), bromide ion (Br - ) etc.

[0086] The pseudohalogen anion is not particularly limited, but examples thereof include a cyan anion, a thiocyanate anion, a cyanate anion, a fulminate anion, and an azide anion.

[0087] The carboxylate anion is not particularly limited, and examples thereof include monocarboxylate anions or dicarboxylate anions having 1 to 18 carbon atoms. Examples of the carboxylate anion include formate anion, acetate anion, propionate anion, butyrate anion, valerate anion, fumarate anion, oxalate anion, lactate anion, and pyruvate anion. In terms of enabling the ionic liquid to be recovered simply and efficiently, the anion component of the ionic liquid is preferably a carboxylate anion (OAc). - ) is preferably included.

[0088] The phosphate anion is not particularly limited, and examples thereof include phosphate anion and phosphate ester anions having 1 to 40 carbon atoms. Examples of the phosphate ester anion include methyl phosphate monoester anion, octyl phosphate monoester anion, octyl phosphate diester anion, lauryl phosphate monoester anion, lauryl phosphate diester anion, stearyl phosphate monoester anion, stearyl phosphate diester anion, eicosyl phosphate monoester anion, and eicosyl phosphate diester anion.

[0089] The above-mentioned ionic liquids can be commercially available products or can be produced by known techniques.

[0090] The ionic liquid is an arbitrary combination of the cation component and the anion component. For example, an ionic liquid containing an imidazolium cation or a quaternary ammonium cation as the cation component is preferred. The imidazolium cation is particularly preferred because of the skeleton of formula (1) in terms of affinity and separation efficiency during extraction operations. Furthermore, an ionic liquid containing a carboxylate anion as the anion component is preferred. More specifically, at least one selected from the group consisting of 1-ethyl-3-methylimidazolium acetate (EmimOAc), 1-ethyl-2,3-dimethylimidazolium acetate (EDmimOAc), 1-butyl-3-methylimidazolium acetate, 1-hexyl-3-methylimidazolium acetate, and tetrabutylammonium acetate is more preferred. Furthermore, the ionic liquid is more preferably at least one selected from the group consisting of 1-ethyl-3-methylimidazolium acetate (EmimOAc) and 1-ethyl-2,3-dimethylimidazolium acetate (EDmimOAc), and 1-ethyl-3-methylimidazolium acetate (EmimOAc) is particularly preferred.

[0091] [Organic Acid] Next, organic acids will be described. The organic acids are components separated from the ionic liquid by the above extraction operation. Examples of organic acids include carboxylic acids such as formic acid, acetic acid, propionic acid, and trifluoroacetic acid (preferably C 1-18 Carboxylic acids, more preferably C 1-10 Carboxylic acids, more preferably C 1-6 Carboxylic acids, particularly preferably C 2-4 Carboxylic acid). 9-18 It is also preferred that the carboxylic acid is C 1-7 Carboxylic acids are also preferred. The organic acids may be used singly or in combination of two or more.

[0092] The organic acid may be derived from the esterifying agent. Examples of the esterifying agent include acid anhydrides. For example, when an acid anhydride is used as the esterifying agent in esterifying a polysaccharide, the resulting mixed liquid (B2) may contain the acid anhydride and / or an organic acid derived from the acid anhydride. The method of the present disclosure can be suitably used when recovering an ionic liquid from the mixed liquid (B2).

[0093] When the organic acid is a carboxylic acid, C relative to the total amount of the carboxylic acid 1-6 The content of the carboxylic acid is, for example, preferably 70% by weight or more, more preferably 80% by weight or more, even more preferably 90% by weight or more, still more preferably 95% by weight or more, and particularly preferably 99% by weight or more. In this case, the ratio of C to the total amount of carboxylic acid is 1-6 The upper limit of the carboxylic acid content is preferably, for example, 100% by weight.

[0094] The molar ratio of the ionic liquid to the organic acid (ionic liquid:organic acid) contained in the mixed liquid (A) is not particularly limited, but is preferably 1:100 to 100:1, more preferably 10:90 to 90:10, even more preferably 20:80 to 80:20, and particularly preferably 30:70 to 70:30. When the ratio of the ionic liquid to the organic acid contained in the mixed liquid is within the above range, the ionic liquid tends to be easily and efficiently recovered from the mixed liquid. Note that when the mixed liquid (A) is prepared by blending the above solvent with the mixed liquid (B), the molar ratio of the ionic liquid to the organic acid contained in the mixed liquid (B) is also preferably within the above range.

[0095] [Water] Next, water will be described. Water may already be contained in the mixed liquid (B), may be newly added to the mixed liquid (B), or may already be contained in the mixed liquid (B) and then further added to the mixed liquid (B). Water forms the aqueous phase in the mixed liquid (A) by contacting with an organic solvent (excluding organic acids) described below. The water in the present disclosure is not particularly limited, and for example, industrial water, tap water, ion-exchanged water, purified water, distilled water, etc. can be used.

[0096] The amount of water used in the method of the present disclosure is not particularly limited, but is preferably 0.01 moles or more, more preferably 0.1 moles or more, even more preferably 1 mole or more, even more preferably 5 moles or more, even more preferably 10 moles or more, even more preferably 15 moles or more, even more preferably 20 moles or more, and even more preferably 25 moles or more, relative to 1 mole of ionic liquid. Furthermore, the amount of water is, for example, preferably 1000 moles or less, more preferably 500 moles or less, even more preferably 300 moles or less, even more preferably 250 moles or less, even more preferably 200 moles or less, even more preferably 150 moles or less, even more preferably 100 moles or less, even more preferably 75 moles or less, even more preferably 50 moles or less, and even more preferably 40 moles or less, relative to 1 mole of ionic liquid. Furthermore, the amount of water is preferably 0.01 to 1000 moles, more preferably 0.1 to 500 moles, even more preferably 1 to 300 moles, and preferably 25 to 40 moles, relative to 1 mole of ionic liquid. When the amount of water contained in the mixed liquid (A) is within the above range, the ratio of the ionic liquid contained in the aqueous phase becomes high, and as a result, it tends to be possible to easily and efficiently recover the ionic liquid from the mixed liquid (A) and / or the mixed liquid (B).

[0097] [Organic Solvent (excluding organic acids) [Organic Solvent (Or)]] Next, organic solvents (excluding organic acids) will be described. Herein, in this specification, the organic solvent may be referred to as "organic solvent (Or)." The organic solvent (Or) may already be contained in the mixed liquid (B), may be newly added to the mixed liquid (B), or may already be contained in the mixed liquid (B) and then further added to the mixed liquid (B). The organic solvent (Or) forms the oil phase in the mixed liquid (A) by contacting with the water described above. The organic solvent (Or) is not particularly limited as long as it is an organic solvent excluding the organic acids and forms an oil phase (organic solvent phase) when mixed with water. For example, at least one organic solvent selected from the group consisting of ethers, ketones, esters, aryls, alkanes, and cycloalkanes may be used. One or more organic solvents (Or) may be used in combination.

[0098] The ethers are not particularly limited, but examples thereof include dialkyl ethers such as diethyl ether, diisopropyl ether, and methyl tert-butyl ether, as well as dioxane. The ketones are not particularly limited, but examples thereof include methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and acetophenone. The esters are not particularly limited, but examples thereof include methyl acetate, ethyl acetate, butyl acetate, and isopropyl acetate. The aryls are not particularly limited, but examples thereof include benzene, toluene, xylene, methoxybenzene, and ethylbenzene. The alkanes are not particularly limited, but examples thereof include n-hexane and n-heptane. The cycloalkanes are not particularly limited, but examples thereof include cyclohexane.

[0099] From the viewpoint of being able to easily and efficiently recover the ionic liquid from the mixed liquid (A), the organic solvent (Or) is preferably at least one selected from the group consisting of ethers, ketones, and esters, more preferably at least one selected from the group consisting of ethers (particularly dialkyl ethers) and esters, even more preferably at least one selected from the group consisting of diethyl ether, diisopropyl ether, and ethyl acetate, and particularly preferably ethyl acetate.

[0100] In the method of the present disclosure, the amount of the organic solvent (Or) is not particularly limited, but is preferably, for example, 1 part by weight or more, more preferably 10 parts by weight or more, even more preferably 20 parts by weight or more, even more preferably 30 parts by weight or more, and even more preferably 50 parts by weight or more, relative to 100 parts by weight of the total amount of the ionic liquid, organic acid, and water contained in the mixed solution (A). The amount of the organic solvent (Or) is also not particularly limited, but is, for example, preferably 10,000 parts by weight or less, more preferably 6,000 parts by weight or less, even more preferably 5,000 parts by weight or less, even more preferably 4,000 parts by weight or less, and even more preferably 2,000 parts by weight or less, relative to 100 parts by weight of the total amount of the ionic liquid, organic acid, and water contained in the mixed solution (A). The upper and lower limits of the amount of organic solvent (Or) are preferably 1 to 10,000 parts by weight, more preferably 10 to 6,000 parts by weight, even more preferably 20 to 5,000 parts by weight, even more preferably 30 to 4,000 parts by weight, and even more preferably 50 to 2,000 parts by weight, relative to 100 parts by weight of the total amount of ionic liquid, organic acid, and water contained in the mixed liquid (A). When the amount of organic solvent (Or) blended in the mixed liquid (A) is within the above range, the ratio of organic acid contained in the oil phase increases, and as a result, the ionic liquid tends to be easily and efficiently recovered from the mixed liquid (A).

[0101] [Other Solvents [Solvent (T)]] In the method of the present disclosure, the mixed liquid (A) may further contain a solvent in addition to the ionic liquid, organic acid, water, and organic solvent (Or). Hereinafter, such a solvent will be referred to as "other solvent" and also as "solvent (T)". The solvent (T) may already be contained in the mixed liquid (B), may be newly added to the mixed liquid (B), or may already be contained in the mixed liquid (B) and further added to the mixed liquid (B). In other words, when the mixed liquid (A) contains the solvent (T), the process of including the solvent (T) may be any of the above. When the solvent (T) is already contained in the mixed liquid (B) from the beginning, the solvent (T) may be included as the solvent (S). In other words, when the mixed liquid (B) is the mixed liquid (B1), the solvent (S) becomes the solvent (T) as it is when the mixed liquid (A) is obtained.

[0102] Specific examples of the solvent (T) include the solvents described as "solvents other than ionic liquids [solvent (S)]" that can be contained in the mixed liquid (B).

[0103] Among the above-mentioned solvents (T), at least one selected from the group consisting of sulfoxides, sulfones, amides, and lactams is preferred from the viewpoints of compatibility with the ionic liquid and solubility of the esterified polysaccharide. Among these, when separating organic acids, the use of at least one selected from the group consisting of dimethyl sulfoxide (DMSO), sulfolane, N,N-dimethylformamide (DMF), and N-methyl-2-pyrrolidone (NMP) tends to increase the distribution ratio of the ionic liquid to the aqueous phase. This tendency becomes more pronounced when at least one selected from the group consisting of N,N-dimethylformamide (DMF) and N-methyl-2-pyrrolidone (NMP) is used, and becomes even more pronounced when N-methyl-2-pyrrolidone (NMP) is used.

[0104] The content of the solvent (T) contained in the mixed liquid (A) is not particularly limited, but is preferably 0.01% by weight or more, more preferably 0.05% by weight or more, even more preferably 0.1% by weight or more, even more preferably 0.3% by weight or more, and particularly preferably 0.5% by weight or more. The content of the solvent (T) contained in the mixed liquid (A) is not particularly limited, but is preferably 30% by weight or less, more preferably 20% by weight or less, even more preferably 10% by weight or less, even more preferably 5% by weight or less, and particularly preferably 4% by weight or less. When the solvent (T) is blended with the mixed liquid (B), it is preferable to prepare the resulting mixed liquid (A) so that it falls within the above range.

[0105] The content of the solvent (T) contained in the mixed liquid (B) is not particularly limited, but is, for example, preferably 1% by weight or more, more preferably 3% by weight or more, even more preferably 5% by weight or more, still more preferably 10% by weight or more, and particularly preferably 15% by weight or more. The content of the solvent (T) contained in the mixed liquid (B) is not particularly limited, but is, for example, preferably 90% by weight or less, more preferably 80% by weight or less.

[0106] [Composition, Extraction Composition] This embodiment encompasses a composition containing a water-soluble ionic liquid, an organic acid, water, and an organic solvent (excluding the organic acid). The composition may further contain other solvents. This composition allows for the production of a highly pure ionic liquid by extraction. The composition of this embodiment is preferably for use in extraction. Hereinafter, the composition will be described as an extraction composition.

[0107] Preferred embodiments of the water-soluble ionic liquid contained in the extraction composition are the same as those described in the above section [Ionic Liquid]. Preferred embodiments of the organic acid contained in the extraction composition are the same as those described in the above section [Organic Acid]. Preferred embodiments of the water contained in the extraction composition are the same as those described in the above section [Water]. Preferred embodiments of the organic solvent (excluding organic acids) contained in the extraction composition are the same as those described in the above section [Organic Solvent (excluding organic acids) [Organic Solvent (Or)]]. Preferred embodiments of the other solvents contained in the extraction composition are the same as those described in the above section [Other Solvents [Solvent (T)]]. Preferred extraction conditions for the extraction composition are the same as those described in the above section [Extraction]. In particular, the above-mentioned mixture (A) can be read as the extraction composition, and the preferred types and amounts of components, extraction conditions, etc. can be referenced. The extraction composition can be obtained by blending water and / or the organic solvent (Or) with a mixture (B) containing an ionic liquid and an organic acid. Therefore, the types and amounts of each of the preferred components of the extraction composition, distillation conditions, etc. can be referenced not only for the mixed solution (A) but also for the mixed solution (B).

[0108] The ionic liquid in the extraction composition is preferably at least one selected from the group consisting of 1-ethyl-3-methylimidazolium acetate (EmimOAc) and 1-ethyl-2,3-dimethylimidazolium acetate (EDmimOAc), and 1-ethyl-3-methylimidazolium acetate (EmimOAc) is more preferred. The organic acid in the extraction composition is preferably acetic acid.

[0109] The organic solvent of the extraction composition is preferably at least one selected from the group consisting of ethers, ketones, and esters, and more preferably at least one selected from the group consisting of ethers (particularly dialkyl ethers) and esters.

[0110] The other solvent is preferably at least one selected from the group consisting of dimethyl sulfoxide, N,N-dimethylformamide, and N-methyl-2-pyrrolidone, more preferably at least one selected from the group consisting of N,N-dimethylformamide and N-methyl-2-pyrrolidone, and particularly preferably N-methyl-2-pyrrolidone.

[0111] The configurations and combinations thereof in the above-described embodiments are merely examples, and additions, omissions, substitutions, and other modifications of the configurations are possible as appropriate within the scope of the present disclosure. The present disclosure is not limited to the embodiments, but is limited only by the claims.

[0112] The present disclosure will be explained in more detail below using examples, but the present disclosure is not limited to these examples.

[0113] The specifications of the NMR apparatus used in the examples are as follows: Product name: JNM-ECZ600R Manufacturer: JEOL Ltd.

[0114] Example 1 0.73 g of EmimOAc and 0.27 g of acetic acid were mixed, and 0.79 g of water was added to prepare a mixed solution. The molar ratio of EmimOAc:acetic acid:water in the mixed solution was 1:1:10. Ethyl acetate was then added in an amount 10 times the weight of the mixed solution and stirred. After standing at room temperature for 1 hour, 1 ml of each was sampled from the aqueous phase and the ethyl acetate phase, and the component weights were quantified by NMR. The following results were obtained: Distribution ratio of acetic acid (acetic acid concentration in ethyl acetate / acetic acid concentration in water) = 0.115 Distribution ratio of EmimOAc (EmimOAc concentration in ethyl acetate / EmimOAc concentration in water) = 0.00132

[0115] Example 2 0.73 g of EmimOAc and 0.26 g of acetic acid were mixed, and 1.57 g of water was added to prepare a mixed solution. The molar ratio of EmimOAc:acetic acid:water in the mixed solution was 1:1:20. Ethyl acetate was then added in an amount 10 times the weight of the mixed solution and stirred. After standing at room temperature for 1 hour, 1 ml of each was sampled from the aqueous phase and the ethyl acetate phase, and the component weights were quantified by NMR. The following results were obtained: Distribution ratio of acetic acid (acetic acid concentration in ethyl acetate / acetic acid concentration in water) = 0.318 Distribution ratio of EmimOAc (EmimOAc concentration in ethyl acetate / EmimOAc concentration in water) = 0.00117

[0116] Example 3: 0.73 g of EmimOAc and 0.27 g of acetic acid were mixed, and 2.39 g of water was added to prepare a mixed solution. The molar ratio of EmimOAc:acetic acid:water in the mixed solution was 1:1:30. Ethyl acetate was then added in an amount 10 times the weight of the mixed solution and stirred. After standing at room temperature for 1 hour, 1 ml of each sample was taken from the aqueous phase and the ethyl acetate phase, and the weights of the components were quantified by NMR. The following results were obtained: Distribution ratio of acetic acid = 0.369 Distribution ratio of EmimOAc = 0.00096

[0117] Example 4: 0.73 g of EmimOAc and 0.27 g of acetic acid were mixed, and 7.86 g of water was added to prepare a mixture. The molar ratio of EmimOAc:acetic acid:water in the mixture was 1:1:100. Ethyl acetate was then added in an amount 10 times the weight of the mixture and stirred. After standing at room temperature for 1 hour, 1 ml of each was sampled from the aqueous phase and the ethyl acetate phase, and the component weights were quantified by NMR. The following results were obtained: Acetic acid distribution ratio (acetic acid concentration in ethyl acetate / acetic acid concentration in water) = 0.427. The EmimOAc distribution ratio (EmimOAc concentration in ethyl acetate) was not detected.

[0118] Example 5 0.73 g of EmimOAc and 0.27 g of acetic acid were mixed, and 2.40 g of water was added to prepare a mixed solution. The molar ratio of EmimOAc:acetic acid:water in the mixed solution was 1:1:30. Diethyl ether was then added in an amount 10 times the weight of the mixed solution and stirred. After standing at room temperature for 1 hour, 1 ml samples were taken from each of the aqueous phase and the diethyl ether phase, and the component weights were quantified by NMR. The following results were obtained: Distribution ratio of acetic acid (acetic acid concentration in diethyl ether / acetic acid concentration in water) = 0.561 Distribution ratio of EmimOAc (EmimOAc concentration in diethyl ether / EmimOAc concentration in water) = 0.00335

[0119] Example 6 0.73 g of EmimOAc and 0.27 g of acetic acid were mixed, and 2.40 g of water was added to prepare a mixed solution. The molar ratio of EmimOAc:acetic acid:water in the mixed solution was 1:1:30. Diisopropyl ether was then added in an amount 10 times the weight of the mixed solution and stirred. After standing at room temperature for 1 hour, 1 ml samples were taken from each of the aqueous phase and the diisopropyl ether phase, and the component weights were quantified by NMR. The following results were obtained: Distribution ratio of acetic acid (acetic acid concentration in diisopropyl ether / acetic acid concentration in water) = 0.172 Distribution ratio of EmimOAc (EmimOAc concentration in diisopropyl ether / EmimOAc concentration in water) = 0.00883

[0120] Example 7 0.73 g of EmimOAc and 0.27 g of acetic acid were mixed, and 3.86 g of water was added to prepare a mixed solution. The molar ratio of EmimOAc:acetic acid:water in the mixed solution was 1:1:50. Ethyl acetate was then added in an amount 10 times the weight of the mixed solution and stirred. After standing at room temperature for 1 hour, 1 ml of each was sampled from the aqueous phase and the ethyl acetate phase, and the component weights were quantified by NMR. The following results were obtained: Distribution ratio of acetic acid (acetic acid concentration in ethyl acetate / acetic acid concentration in water) = 0.401 Distribution ratio of EmimOAc (EmimOAc concentration in ethyl acetate / EmimOAc concentration in water) = 0.000935

[0121] Example 8 0.73 g of EmimOAc and 0.27 g of acetic acid were mixed, and 1.57 g of water and 0.43 g of NMP were added to prepare a mixed solution. The molar ratio of EmimOAc:acetic acid:water:NMP in the mixed solution was 1:1:20:1. Ethyl acetate was then added in an amount 10 times the weight of the mixed solution and stirred. After standing at room temperature for 1 hour, 1 ml of each was sampled from the aqueous phase and the ethyl acetate phase, and the component weights were quantified by NMR. The following results were obtained: Distribution ratio of acetic acid (acetic acid concentration in ethyl acetate / acetic acid concentration in water) = 0.286 Distribution ratio of EmimOAc (EmimOAc concentration in ethyl acetate / EmimOAc concentration in water) = 0.000990 Distribution ratio of NMP (NMP concentration in ethyl acetate / NMP concentration in water) = 0.386

[0122] Therefore, it has been proven that when extracting a mixture containing an ionic liquid (e.g., EmimOAc) and an organic acid (e.g., acetic acid) with water and an organic solvent (e.g., ethyl acetate) to separate the organic acid, if it is desired to partition the ionic liquid more toward the aqueous phase, it is preferable to further add an organic solvent such as NMP.

[0123] Example 9 The structural formula of EmimOAc recovered from the aqueous phase in Example 3 is the same as that of EmimOAc before extraction (before recovery).

[0124] Example 10: After evaporating the water from the EmimOAc and water mixture recovered in Example 3, the resulting EmimOAc (1 g) was mixed with cellulose (0.18 g, Sigma-Aldrich's "Avicel PH-101" product name, number-average degree of polymerization: 105) and stirred, resulting in dissolution of the cellulose. This phenomenon demonstrates that the ionic liquid recovered by the method of the present disclosure can be reused.

[0125] Comparative Example 1: A mixture was prepared by mixing 0.75 g of EmimOAc and 0.27 g of acetic acid. The EmimOAc:acetic acid (molar ratio) in the mixture was 1:1. Ethyl acetate was then added in an amount 10 times the weight of the mixture and stirred, resulting in separation into two phases: an ethyl acetate phase (upper phase) and an acetic acid phase (lower phase). After standing at room temperature for 1 hour, 1 ml of the mixture was sampled and the component weights were quantified by NMR. It was found that the ethyl acetate phase contained 46.3 wt% of EmimOAc and 51.6 wt% of acetic acid. It was also found that the acetic acid phase contained 53.7 wt% of EmimOAc.

[0126] To summarize the above, the configuration of the present invention and its variations are described below. [1] A method for recovering an ionic liquid from a mixed liquid (B) containing an ionic liquid and an organic acid, wherein the ionic liquid is water-soluble, the method comprising blending at least one selected from the group consisting of water and an organic solvent (excluding organic acids) (also referred to as organic solvent (Or)) with the mixed liquid (B), and separating the organic acid by extraction. [2] The method for recovering an ionic liquid according to [1], wherein the mixed liquid (B) is a mixed liquid (B1) containing a reaction product obtained when a specific raw material is esterified with an esterifying agent using an ionic liquid as a solvent. [3] The method for recovering an ionic liquid according to [2], wherein the raw material is a polysaccharide (e.g., one or more selected from the group consisting of cellulose, hemicellulose, xylan, mannan, glucomannan, glucuronoxylan, starch, amylose, amylopectin, glycogen, dextrin, pectin, chitin, chitosan, agarose, carrageenan, isolichenan, laminaran, lichenan, glucan, inulin, levan, fructan, galactan, arabinan, pentosan, alginic acid, pectinic acid, protuberic acid, colominic acid, porphyran, fucoidan, ascophyllan, locust bean gum, guar gum, tamarind gum, tara gum, and gum arabic). [4] The method for recovering an ionic liquid according to [2] or [3], wherein the esterifying agent is one or more selected from the group consisting of a chain ester compound, a cyclic ester compound, an unsaturated aldehyde, a saturated aldehyde, an acid halide, an acid anhydride, and allyl alcohol. [5] The method for recovering an ionic liquid according to [4], wherein the acid anhydride is one or more selected from the group consisting of acetic anhydride, propionic anhydride, butyric anhydride, valeric anhydride, caproic anhydride, enanthic anhydride, caprylic anhydride, pelargonic anhydride, capric anhydride, lauric anhydride, myristic anhydride, palmitic anhydride, stearic anhydride, oleic anhydride, linoleic anhydride, linolenic anhydride, benzoic anhydride, phthalic anhydride, maleic anhydride, and succinic anhydride. [6] The method for recovering an ionic liquid according to any one of [1] to [5], wherein the mixed liquid (B) contains a solvent (solvent (S)) other than the ionic liquid.[7] The solvent (S) is selected from the group consisting of nitriles such as acetonitrile; sulfoxides such as dimethyl sulfoxide (DMSO); sulfones such as cyclic sulfones (e.g., sulfolane); ethers such as cyclic ethers (e.g., 1,3-dioxolane, 1,4-dioxane, tetrahydrofuran); amides such as N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMAc); lactams such as N-methyl-2-pyrrolidone (NMP); lactones such as γ-butyrolactone; and amines such as pyridine. The method for recovering an ionic liquid according to [6], wherein the selected ionic liquid is at least one selected from the group consisting of sulfoxides, sulfones, amides, and lactams, at least one selected from the group consisting of dimethyl sulfoxide (DMSO), sulfolane, N,N-dimethylformamide (DMF), and N-methyl-2-pyrrolidone (NMP), at least one selected from the group consisting of N,N-dimethylformamide (DMF) and N-methyl-2-pyrrolidone (NMP), or N-methyl-2-pyrrolidone (NMP).[8] A method for preparing a mixed liquid (A) containing an ionic liquid, an organic acid, water, and an organic solvent (Or) by blending at least one selected from the group consisting of water and an organic solvent (Or) with a mixed liquid (B) includes a method for preparing the mixed liquid (A) by adding the organic solvent (Or) to a mixed liquid (B) containing an ionic liquid, an organic acid, and water; a method for preparing the mixed liquid (A) by adding water and the organic solvent (Or) to a mixed liquid (B) containing an ionic liquid, an organic acid, and water; a method for preparing the mixed liquid (A) by adding water to a mixed liquid (B) containing an ionic liquid, an organic acid, and the organic solvent (Or); a method for preparing the mixed liquid (A) by adding water and the organic solvent (Or) to a mixed liquid (B) containing an ionic liquid, an organic acid, and the organic solvent (Or). the organic solvent (Or) added to a mixed solution (B) containing an ionic liquid and an organic acid; the organic solvent (Or) added to a mixed solution (B) containing an ionic liquid and an organic acid; the organic solvent (Or) added to a mixed solution containing an ionic liquid, an organic acid, water, and the organic solvent (Or); the organic solvent (Or) added to a mixed solution containing an ionic liquid, an organic acid, water, and the organic solvent (Or); or the organic solvent (Or) added to a mixed solution containing an ionic liquid, an organic acid, water, and the organic solvent (Or). [9] The ionic liquid recovery method according to any one of [1] to [8], wherein the mixed solution (B) is subjected to an extraction operation without pretreatment.

[10] The ionic liquid recovery method according to any one of [1] to [9], wherein the structural formula of the recovered ionic liquid is the same as the structural formula of the ionic liquid in the mixed solution (B) before extraction.

[11] The method for recovering an ionic liquid according to any one of [1] to

[10] , wherein the temperature during extraction of mixed liquid (B) is 0 to 100°C, 1 to 90°C, 3 to 80°C, or 5 to 70°C.

[12] The method for recovering an ionic liquid according to any one of [1] to

[11] , wherein the pressure during extraction of mixed liquid (B) is 10 to 2000 hPa, 100 to 1500 hPa, or 500 to 1200 hPa (for example, atmospheric pressure).

[13] The method for recovering an ionic liquid according to any one of [1] to

[12] , wherein the ionic liquid is a salt composed of a cation component and an anion component.

[14] The method for recovering an ionic liquid according to any one of [1] to

[13] , wherein the ionic liquid contains, as a cationic component, at least one selected from the group consisting of imidazolium cation, pyridinium cation, pyrrolidinium cation, piperidinium cation, quaternary ammonium cation, and quaternary phosphonium cation.

[15] The method for recovering an ionic liquid according to any one of [1] to

[14] , wherein the ionic liquid contains, as a cationic component, an imidazolium cation or a quaternary ammonium cation.

[16] The method for recovering an ionic liquid according to any one of [1] to

[14] , wherein the imidazolium cation is a cation represented by the formula (1) (wherein R 1 and R 3 are the same or different and are a substituted or unsubstituted alkyl group, alkenyl group, alkoxyalkyl group, or substituted or unsubstituted phenyl group, R 2 , R 4 , and R 5 and are the same or different and are a hydrogen atom, a substituted or unsubstituted alkyl group, an alkenyl group, an alkoxyalkyl group, or a substituted or unsubstituted phenyl group.

[17] The method for recovering an ionic liquid according to

[14] or

[15] , wherein the pyridinium cation is a cation represented by the above formula (2) (wherein R 6 is an alkyl group, an alkenyl group, an alkoxyalkyl group, or a substituted or unsubstituted phenyl group, and R 7 ~R 11 and are the same or different and are a hydrogen atom, an alkyl group, an alkenyl group, an alkoxyalkyl group, or a substituted or unsubstituted phenyl group.

[18] The method for recovering an ionic liquid according to any one of

[14] to

[16] , wherein the pyrrolidinium cation is a cation represented by the above formula (3) (wherein R 12 and R 13 are the same or different and are an alkyl group, an alkenyl group, an alkoxyalkyl group, or a substituted or unsubstituted phenyl group; R 14 ~R 21and are the same or different and are a hydrogen atom, an alkyl group, an alkenyl group, an alkoxyalkyl group, or a substituted or unsubstituted phenyl group.

[19] The method for recovering an ionic liquid according to any one of

[14] to

[17] , wherein the piperidinium cation is a cation represented by the above formula (4) (wherein R 22 and R 23 are the same or different and are an alkyl group, an alkenyl group, an alkoxyalkyl group, or a substituted or unsubstituted phenyl group; R 24 ~R 33 and are the same or different and are a hydrogen atom, an alkyl group, an alkenyl group, an alkoxyalkyl group, or a substituted or unsubstituted phenyl group.

[20] The method for recovering an ionic liquid according to any one of

[14] to

[18] , wherein the quaternary ammonium cation is a cation represented by the formula (5) (wherein R 34 ~R 37 and are the same or different and are an alkyl group, an alkenyl group, an alkoxyalkyl group, or a substituted or unsubstituted phenyl group.

[21] The method for recovering an ionic liquid according to any one of

[14] to

[19] , wherein the quaternary phosphonium cation is an ammonium cation represented by the formula (6) (wherein R 38 ~R 41 are the same or different and are an alkyl group, an alkenyl group, an alkoxyalkyl group, or a substituted or unsubstituted phenyl group.

[22] The method for recovering an ionic liquid according to any one of

[14] to

[20] , wherein the ionic liquid is a phosphonium cation represented by the formula (I) or (II).

[23] The method for recovering an ionic liquid according to any one of

[14] to

[20] , wherein the ionic liquid is a phosphonium cation represented by the formula (I) or (II).

[24] The method for recovering an ionic liquid according to any one of

[14] to

[20] , wherein the ionic liquid is a phosphonium cation represented by the formula (I) or (II).

[25] The method for recovering an ionic liquid according to any one of

[14] to

[20] , wherein the ionic liquid is a phosphonium cation represented by the formula (I) or (II).

[26] The method for recovering an ionic liquid according to any one of

[14] to

[20] , wherein the ionic liquid is a phosphonium cation represented by the formula (I) or (II).

[27] The method for recovering an ionic liquid according to any one of

[14] to

[20] , wherein the ionic liquid is a phosphonium cation represented by the formula (I) or (II).

[28] The method for recovering an ionic liquid according to any one of

[14] to

[20] , wherein the ionic liquid is a phosphonium cation represented by the formula (I).

[29] The method for recovering an ionic liquid according to any one of

[14] to

[20] , wherein the ionic liquid is a phosphonium cation represented by the formula (I).

[30] The method for recovering an ionic liquid according to any one of

[14] to

[20] , 4- ), sulfomethyl ion (CH3SO3 - ), methylphosphonate, sulfate ion, and PF6 -

[23] The method for recovering an ionic liquid according to any one of [1] to

[22] , wherein the ionic liquid contains a carboxylic acid anion as an anion component.

[24] The method for recovering an ionic liquid according to any one of [1] to

[22] , wherein the organic acid is selected from the group consisting of carboxylic acid, C 1-18 Carboxylic acid, C 1-10 Carboxylic acid, C 1-6 Carboxylic acid, C 2-4 Carboxylic acid, C 9-18 Carboxylic acid, and / or C 1-7

[25] The method for recovering an ionic liquid according to any one of [1] to

[24] , wherein the organic acid is at least one selected from the group consisting of formic acid, acetic acid, propionic acid, and trifluoroacetic acid.

[26] The method for recovering an ionic liquid according to any one of [1] to

[24] , wherein the organic acid is a carboxylic acid, and the C relative to the carboxylic acid (total amount) is 1-6The method for recovering an ionic liquid according to any one of [1] to

[25] , wherein the carboxylic acid content is 70% by weight or more, 80% by weight or more, 90% by weight or more, 95% by weight or more, or 99% by weight or more.

[27] The method for recovering an ionic liquid according to any one of [1] to

[26] , wherein the molar ratio of the ionic liquid to the organic acid (ionic liquid:organic acid) contained in the mixed liquid (A) or the mixed liquid (B) is 1:100 to 100:1, 10:90 to 90:10, 20:80 to 80:20, or 30:70 to 70:30.

[28] The method for recovering an ionic liquid according to any one of [1] to

[27] , wherein the amount of water used or the amount of water contained in the mixed solution (A) is 0.01 mol or more, 0.1 mol or more, 1 mol or more, 5 mol or more, 10 mol or more, 15 mol or more, 20 mol or more, 25 mol or more, 1000 mol or less, 500 mol or less, 300 mol or less, 250 mol or less, 200 mol or less, 150 mol or less, 100 mol or less, 75 mol or less, 50 mol or less, 40 mol or less, 0.01 to 1000 mol, 0.1 to 500 mol, 1 to 300 mol, and / or 25 to 40 mol per 1 mol of the ionic liquid.

[29] The method for recovering an ionic liquid according to any one of [1] to

[28] , wherein the organic solvent (Or) is at least one selected from the group consisting of ethers, ketones, esters, aryls, alkanes, and cycloalkanes.

[30] The method for recovering an ionic liquid according to any one of [1] to

[29] , wherein the organic solvent (Or) is at least one selected from the group consisting of ethers, ketones, and esters.

[31] The method for recovering an ionic liquid according to any one of [1] to

[30] , wherein the organic solvent (Or) is an ether (particularly a dialkyl ether) or an ester.

[32] The method for recovering an ionic liquid according to any one of [1] to

[31] , wherein the ether is at least one selected from the group consisting of dialkyl ethers (diethyl ether, diisopropyl ether, or methyl tert-butyl ether) and dioxane; the ketone is at least one selected from the group consisting of methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and acetophenone; the ester is at least one selected from the group consisting of methyl acetate, ethyl acetate, butyl acetate, and isopropyl acetate; the aryl is at least one selected from the group consisting of benzene, toluene, xylene, methoxybenzene, and ethylbenzene; the alkane is at least one selected from the group consisting of n-hexane and n-heptane; and / or the cycloalkane is cyclohexane.

[33] The method for recovering an ionic liquid according to any one of [8] to

[32] , wherein the amount of the organic solvent (Or) is 1 part by weight or more, 10 parts by weight or more, 20 parts by weight or more, 30 parts by weight or more, 50 parts by weight or more, 10,000 parts by weight or less, 6,000 parts by weight or less, 5,000 parts by weight or less, 4,000 parts by weight or less, 2,000 parts by weight or less, 1 to 10,000 parts by weight, 10 to 6,000 parts by weight, 20 to 5,000 parts by weight, 30 to 4,000 parts by weight, and / or 50 to 2,000 parts by weight, relative to 100 parts by weight of the total amount of the ionic liquid, organic acid, and water contained in the mixed solution (A).

[34] The method for recovering an ionic liquid according to any one of [8] to

[33] , wherein the mixed solution (A) further contains a solvent (solvent (T)) in addition to the ionic liquid, organic acid, water, and organic solvent (Or).

[35] The method for recovering an ionic liquid according to

[34] , wherein the solvent (T) is at least one selected from the group consisting of sulfoxides, sulfones, amides, and lactams.

[36] The method for recovering an ionic liquid according to

[34] or

[35] , wherein the solvent (T) is at least one selected from the group consisting of dimethyl sulfoxide (DMSO), sulfolane, N,N-dimethylformamide (DMF), and N-methyl-2-pyrrolidone (NMP), at least one selected from the group consisting of N,N-dimethylformamide (DMF) and N-methyl-2-pyrrolidone (NMP), or N-methyl-2-pyrrolidone (NMP).

[37] The method for recovering an ionic liquid according to any one of

[34] to

[36] , wherein the content of the solvent (T) contained in the mixed solution (A) is 0.01 wt% or more, 0.05 wt% or more, 0.1 wt% or more, 0.3 wt% or more, 0.5 wt% or more, 30 wt% or less, 20 wt% or less, 10 wt% or less, 5 wt% or less, and / or 4 wt% or less.

[38] The method for recovering an ionic liquid according to any one of

[34] to

[37] , wherein the content of the solvent (T) contained in the mixed solution (B) is 1 wt% or more, 3 wt% or more, 5 wt% or more, 10 wt% or more, 15 wt% or more, 90 wt% or less, and / or 80 wt% or less.

[39] The organic acid is C. 1-7 The method for recovering an ionic liquid according to any one of [1] to

[38] , wherein the organic acid is a carboxylic acid of the formula (I).

[40] A composition comprising a water-soluble ionic liquid, an organic acid, water, and an organic solvent (excluding the organic acid).

[41] The composition according to

[40] , wherein the ionic liquid is for use in extraction.

[42] The composition according to

[40] or

[41] , wherein the ionic liquid in the composition is at least one selected from the group consisting of 1-ethyl-3-methylimidazolium acetate (EmimOAc) and 1-ethyl-2,3-dimethylimidazolium acetate (EDmimOAc), or 1-ethyl-3-methylimidazolium acetate (EmimOAc).

[43] The composition according to

[40] to

[42] , wherein the organic acid in the composition is acetic acid.

[44] The composition according to any one of

[40] to

[43] , wherein the organic solvent of the composition is at least one selected from the group consisting of ethers, ketones, and esters, or at least one selected from the group consisting of ethers (particularly dialkyl ethers) and esters.

[45] The composition according to any one of

[40] to

[44] , further comprising at least one selected from the group consisting of dimethyl sulfoxide, N,N-dimethylformamide, and N-methyl-2-pyrrolidone, at least one selected from the group consisting of N,N-dimethylformamide and N-methyl-2-pyrrolidone, or N-methyl-2-pyrrolidone.

[0127] According to the method for recovering an ionic liquid of the present disclosure, the ionic liquid can be recovered simply and efficiently from a mixed liquid containing an ionic liquid and an organic acid.

Claims

1. A method for recovering an ionic liquid from a mixture containing an ionic liquid and an organic acid, The aforementioned ionic liquid is water-soluble, A method for recovering an ionic liquid, characterized by adding water and an organic solvent (excluding organic acids) to the aforementioned mixture, wherein the amount of water is 1 to 300 moles per mole of the ionic liquid, and separating the organic acids by extraction.

2. The method for recovering an ionic liquid according to claim 1, wherein the ionic liquid contains an imidazolium cation or a quaternary ammonium cation as a cationic component.

3. The method for recovering an ionic liquid according to claim 1 or 2, wherein the ionic liquid contains a carboxylic acid anion as an anionic component.

4. The method for recovering an ionic liquid according to claim 1 or 2, wherein the organic acid is a carboxylic acid.

5. The method for recovering an ionic liquid according to claim 1 or 2, wherein the organic solvent is at least one selected from the group consisting of ethers, ketones, esters, aryls, alkanes, and cycloalkanes.

6. The method for recovering an ionic liquid according to claim 1 or 2, wherein the organic solvent is at least one selected from the group consisting of ethers, ketones, and esters.

7. The aforementioned organic acid is C １－７ A method for recovering an ionic liquid according to claim 1 or 2, wherein the carboxylic acid is...