Method for recovering ionic liquid

Abstract

The present invention provides a method for easily and efficiently recovering an ionic liquid from a liquid mixture that contains the ionic liquid and an organic acid.　This method for recovering an ionic liquid is characterized by subjecting a liquid mixture (A) that contains an ionic liquid, an organic acid and a solvent (excluding an organic acid) to distillation.

Description

Method for recovering ionic liquid

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

[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 is difficult to remove the organic acid by distillation from such a mixture, possibly due to an interaction between the organic acid and the ionic liquid, making it difficult to separate and recover the ionic liquid from the mixture.

[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 problems, the inventors of the present disclosure have discovered that the ionic liquid mixture can be recovered simply and efficiently by adding a solvent to a mixture containing an ionic liquid and an organic acid and then distilling the mixture. 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, which comprises distilling a mixed liquid (A) containing an ionic liquid, an organic acid, and a solvent (excluding the organic acid).

[0010] In the method of the present disclosure, it is preferable to mix a solvent (excluding the organic acid) with the mixed liquid (B) containing the ionic liquid and the organic acid, and then distill the mixture.

[0011] The solvent is preferably a polar solvent.

[0012] The HSP value of the above solvent at 25 ° C. [(MPa) 0.5 ] is preferably 15 or more.

[0013] The ionic liquid preferably contains an imidazolium cation or a quaternary ammonium cation as a cationic component.

[0014] The ionic liquid preferably contains a carboxylate anion as the anion component.

[0015] The organic acid is preferably a carboxylic acid.

[0016] The solvent is at least one selected from the group consisting of cyclohexanol, 1-hexanol, 1-heptanol, 2-octanol, and 2-ethylhexanol, and the content of the ionic liquid in the mixed liquid (A) is preferably 0.3 to 9 wt %.

[0017] The pressure during the distillation is preferably 1519 hPa or less.

[0018] 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.

[0019] The method for recovering an ionic liquid according to the present disclosure (hereinafter sometimes referred to as the "method of the present disclosure") is a method for recovering an ionic liquid by distilling a mixed liquid (A) containing an ionic liquid, an organic acid, and a solvent (excluding the organic acid). The solvent (excluding the organic acid) may be referred to as solvent (X).

[0020] [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 is referred to as mixed liquid (B). Also, in this specification, a mixed liquid containing an ionic liquid, an organic acid, and a solvent (X) is referred to as mixed liquid (A). The mixed liquid (A) is not particularly limited as long as it contains an ionic liquid, an organic acid, and a solvent (X), but it is preferably a mixed liquid (B) containing an ionic liquid and an organic acid and a solvent (X) blended with the solvent. The mixed liquid (B) is not particularly limited as long as it contains an ionic liquid and an organic acid, but it may be, for example, a mixed liquid 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 (hereinafter, sometimes referred to as "mixed liquid (B1)"). The mixed liquid (B1) contains, for example, an esterified product (an 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, solvents other than the ionic liquid, etc. 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 be any liquid as long as it contains at least the organic acid derived from the esterifying agent and the ionic liquid.

[0021] 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.

[0022] 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).

[0023] 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.

[0024] <Raw Material> First, the raw material will be described. The raw material means a starting material to be esterified by an 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).

[0025] The polysaccharide may be biomass containing polysaccharides (polysaccharide-containing biomass). The polysaccharide-containing biomass is not particularly limited as long as it contains polysaccharides, but examples 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 and the like obtained by refining these biomasses can also be used. The polysaccharide-containing biomass may be in a polysaccharide state after various pretreatments, such as cutting and drying, as necessary, followed by a process of separating and extracting polysaccharides (e.g., cellulose). The polysaccharides may be used alone or in combination of two or more.

[0026] 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.

[0027] <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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] The saturated aldehyde is not particularly limited, but examples thereof include propanal, hexanal, octanal, and nonanal.

[0032] 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.

[0033] 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.

[0034] The allyl alcohol is not particularly limited, but examples thereof include methallyl alcohol, acrylic alcohol, 2-hydroxymethyl-1-butene, and α-hydroxymethylstyrene.

[0035] <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.

[0036] <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.

[0037] 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.

[0038] 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).

[0039] As the solvent (S), a solvent exemplified as the solvent (X) described later can also be used. In this case, the distillation operation can be carried out without blending (adding) the solvent (X) separately to the mixed liquid (B1).

[0040] 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).

[0041] [Distillation] The method of the present disclosure is characterized by distilling the mixed liquid (A) to recover the ionic liquid. Alternatively, the mixed liquid (A) may be prepared by blending the solvent (X) with the mixed liquid (B), followed by distillation. That is, during the distillation, the solvent (X) may be blended into a mixed liquid containing at least an ionic liquid and an organic acid. The method of blending the solvent (X) with the mixed liquid (B), i.e., the method of preparing the mixed liquid (A), is not particularly limited. For example, the solvent (X) may be blended (added) after mixing the ionic liquid and the organic acid, or may be mixed together with the ionic liquid and the organic acid. When the mixed liquid (B) is the mixed liquid (B1), the solvent (X) may be blended into the system before the reaction to carry out various reactions, resulting in the mixed liquid (B1) containing the solvent (X). Alternatively, the mixed liquid (B1) may be prepared by blending the solvent (X) with the mixed liquid (B1) after the reaction.

[0042] In the method of the present disclosure, the mixed liquid (A) may be distilled as is (i.e., without pretreatment), or may be distilled after pretreatment. Such pretreatment may involve subjecting the mixed liquid (A) to heat treatment for a certain period of time, forming a reaction product (e.g., a carboxylate ester) by reaction between an organic acid (e.g., a carboxylic acid) and a solvent (e.g., an alcohol), and then removing the reaction product by distillation. However, in the method of the present disclosure, since the mixed liquid (A) contains specific components, the organic acid and the ionic liquid can be separated by distillation, resulting in the effect of being able to recover the ionic liquid simply and efficiently. In other words, the method of the present disclosure achieves the above-mentioned effective effect without requiring the above-mentioned pretreatment. Therefore, in the method of the present disclosure, it is preferable to distill the mixed liquid (A) as is (e.g., without pretreatment such as heat treatment for a certain period of time).

[0043] The operation of distilling the mixed liquid (A) to separate the ionic liquid is not particularly limited, but may be, for example, a continuous distillation operation in which the mixed liquid (B) and the solvent (X) are continuously charged into a distillation apparatus, or a batch distillation operation in which the solvent (X) is previously blended with the mixed liquid (B) into a distillation apparatus. Alternatively, a semi-batch distillation operation in which either the mixed liquid (B) or the solvent (X) is previously charged into the distillation apparatus and the remaining is continuously charged may be performed. The distillation operation may be performed under reduced pressure conditions (reduced pressure type), atmospheric pressure conditions (atmospheric pressure type), and pressurized conditions (pressurized type), but is preferably under atmospheric pressure conditions (atmospheric pressure type) or reduced pressure conditions (reduced pressure type). In particular, it is preferable to perform the distillation operation under reduced pressure conditions without under pressurized conditions. By performing the distillation operation under reduced pressure conditions without under pressurized conditions, the organic acid described below can be extracted as a pure organic acid without reacting with the ionic liquid or the solvent (X). The ionic liquid and solvent (X) from which the organic acid has been extracted also do not react with each other and are extracted as a pure ionic liquid and a pure solvent, respectively.

[0044] The temperature during distillation of the mixed solution (A) can be appropriately selected so as to separate the organic acid from the solvent (X), and is not particularly limited. For example, it is preferably 0°C or higher, more preferably 10°C or higher, even more preferably 15°C or higher, and particularly preferably 20°C or higher. The temperature during distillation of the mixed solution (A) is preferably 400°C or lower, more preferably 350°C or lower, even more preferably 300°C or lower, even more preferably 250°C or lower, even more preferably 200°C or lower, even more preferably 150°C or lower, even more preferably 130°C or lower, even more preferably 100°C or lower, even more preferably 95°C or lower, and even more preferably 90°C or lower. The temperature during distillation of the mixed solution (A) is preferably 0 to 150°C, more preferably 10 to 130°C, even more preferably 15 to 100°C, even more preferably 20 to 95°C, and particularly preferably 20 to 90°C. The temperature during distillation of the mixed solution (A) is also preferably 20 to 150°C.

[0045] The pressure when distilling the mixed solution (A) is, for example, preferably 0.1 hPa or more, more preferably 0.5 hPa or more, even more preferably 0.8 hPa or more, even more preferably 1 hPa or more, even more preferably 5 hPa or more. The pressure when distilling the mixed solution (A) is, for example, preferably 1519 hPa or less, more preferably 1013 hPa or less, even more preferably 1000 hPa or less, even more preferably 800 hPa or less, even more preferably 500 hPa or less, even more preferably 300 hPa or less, even more preferably 100 hPa or less, even more preferably 50 hPa or less. The pressure when distilling the mixed solution (A) is preferably 0.5 to 1519 hPa, more preferably 1 to 1013 hPa, even more preferably 5 to 100 hPa. When the pressure during distillation of the mixed liquid (A) is within the above-mentioned range, the organic acid described below does not react with the ionic liquid or the solvent (X) (for example, a reaction such as an esterification reaction between an organic acid and a solvent such as an alcohol does not occur).

[0046] The time for distilling the mixed liquid (A) is not particularly limited, and for example, the time until the distillation of the organic acid from the mixed liquid (A) stops can be set as the distillation time.

[0047] In the above distillation operation, reflux may be carried out as necessary. In particular, when the organic acid distilled by distillation and the solvent (X) are separated into liquids, it is preferable to reflux the solvent (X) phase.

[0048] The distillation apparatus used in the distillation operation is not particularly limited, and any known or commonly used distillation apparatus can be used, such as a simple distillation apparatus, a multi-stage distillation apparatus, a vacuum distillation apparatus, a molecular distillation apparatus, or a steam distillation apparatus.

[0049] The distillation operation allows the ionic liquid to be separated from the mixed liquid (A). Generally, the distillation operation results in the production of an organic acid or a mixed liquid of an organic acid and a solvent (X) as a fraction, and the production of an ionic liquid or a mixed liquid containing a high concentration of an ionic liquid as a residue. The ionic liquid can be separated from the mixed liquid containing the ionic liquid by further known or conventional purification methods such as distillation, or the mixed liquid can be used directly for other purposes (for example, the esterification reaction of polysaccharide-containing biomass described below). In other words, according to the method of the present disclosure, a highly pure ionic liquid can be obtained by the simple method of distillation in an easy-to-handle state.

[0050] As described above, the distillation procedure yields the organic acid as a fraction and the ionic liquid as a residue. This allows the ionic liquid to be recovered in a form separated from the organic acid. The structural formula of the recovered ionic liquid is preferably the same as the structural formula of the ionic liquid (in the mixed liquid (A) or the mixed liquid (B)) before distillation.

[0051] Next, the ionic liquid will be described. The ionic liquid is a liquid component separated from the organic acid by the distillation operation (distillation 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 is preferably non-volatile. [Ionic Liquid] In this specification, the term "ionic liquid" refers to a salt composed of a cation component and an anion component, and may be any of an acidic ionic liquid, a neutral ionic liquid, and a basic ionic liquid, or may be any of a water-soluble ionic liquid and a water-insoluble ionic liquid. In this specification, the liquidity of an ionic liquid can be determined by the acid dissociation constant (pKa, calculated value in vacuum) of the conjugate acid of the anion. For example, a basic ionic liquid has an acid dissociation constant of 2 to 19. Only one type of the ionic liquid may be used, or two or more types may be used.

[0052] 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.

[0053] 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).

[0054]

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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).

[0060]

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] Examples of the pyrrolidinium cation include cations represented by the following formula (3): The cation represented by formula (3) also includes its tautomers.

[0066]

[0067] 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.

[0068] 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.

[0069] 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.

[0070] As the pyrrolidinium cation, a 1-butyl-1-methylpyrrolidinium cation is particularly preferred.

[0071] The piperidinium cation includes a cation represented by the following formula (4): The cation represented by formula (4) also includes its tautomers.

[0072]

[0073] 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.

[0074] 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.

[0075] 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.

[0076] The piperidinium cation is preferably a 1-butyl-1-methylpiperidinium cation.

[0077] 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.

[0078]

[0079] 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.

[0080] 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.

[0081] R 34~R 37 is preferably an alkyl group, more preferably a straight-chain alkyl group having 1 to 6 carbon atoms.

[0082] Examples of the quaternary ammonium cation include ammonium cations such as trimethylpropylammonium, trimethylbutylammonium, triethylmethylammonium, trioctylmethylammonium, tetramethylammonium, tetraethylammonium, tetrabutylammonium, tetrapentylammonium, and tetrahexylammonium.

[0083] 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.

[0084]

[0085] 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.

[0086] 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.

[0087] Examples of the quaternary phosphonium cation include quaternary phosphonium cations such as tetramethylphosphonium, tetraethylphosphonium, tetrabutylphosphonium, tetrahexylphosphonium, tetraoctylphosphonium, triethylmethylphosphonium, and tributylethylphosphonium.

[0088] Anion Component Examples of the anion component in the ionic liquid 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.

[0089] The halogen anion is not particularly limited, but for example, a fluoride ion (F - ), chloride ions (Cl - ), iodine ion (I - ), bromide ion (Br - ) etc.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] The above-mentioned ionic liquids can be commercially available products or can be produced by known techniques.

[0094] 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 in the distillation operation. 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.

[0095] In the mixed liquid (A), the content of the ionic liquid is preferably 0.1 wt % or more, more preferably 0.3 wt % or more, even more preferably 0.5 wt % or more, particularly preferably 1 wt % or more, and most preferably 2 wt % or more.

[0096] In addition, the solvent (X) has an HSP value at 25 ° C. [(MPa) 0.5 ] is 18.5 to 21.5 linear or branched monoalcohol, and HSP value at 25 ° C [(MPa) 0.5

[0039] When the solvent (X) is at least one selected from the group consisting of monoalcohols having an alicyclic skeleton of 21.6 to 23, the content of the ionic liquid in the mixed solution (A) is preferably 9.9% by weight or less, more preferably 9.5% by weight or less, even more preferably 9% by weight or less, even more preferably 8% by weight or less, even more preferably 7% by weight or less, and even more preferably 5% by weight or less. In particular, when the solvent (X) is at least one selected from the group consisting of cyclohexanol, 1-hexanol, 1-heptanol, 2-octanol, and 2-ethylhexanol, the content of the ionic liquid in the mixed solution is more preferably 0.3 to 9% by weight, even more preferably 0.5 to 8% by weight, and particularly preferably 1 to 7% by weight.

[0097] Furthermore, when the solvent (X) is water, the content of the ionic liquid in the mixed liquid (A) is preferably 45% by weight or less, more preferably 40% by weight or less, even more preferably 30% by weight or less, even more preferably 20% by weight or less, even more preferably 9.9% by weight or less, even more preferably 9.5% by weight or less, even more preferably 9% by weight or less, and even more preferably 5% by weight or less. By having the amount of ionic liquid blended in the mixed liquid (A) within the above range, the ionic liquid can be recovered from the mixed liquid (A) simply and efficiently.

[0098] [Organic Acid] Next, the organic acid will be described. The organic acid is a component separated from the ionic liquid by the above-mentioned distillation operation. Examples of the organic acid 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 It is also preferable that the organic acid is a carboxylic acid of the formula:

[0033] One kind of the organic acid may be used alone, or two or more kinds thereof may be used together.

[0099] The organic acid may be derived from the esterifying agent. Examples of the esterifying agent include acid anhydrides. For example, when an ionic liquid is used as a solvent and an acid anhydride is used as an esterifying agent in the esterification of a polysaccharide, the resulting mixed liquid (B2) may contain the ionic liquid and 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) described above.

[0100] 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.

[0101] 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 (A) is within the above range, the ionic liquid tends to be easily and efficiently recovered from the mixed liquid (A). Note that when the mixed liquid (A) is prepared by blending the solvent (X) 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.

[0102] The content of the organic acid in the mixed solution (A) is, for example, preferably 0.01% by weight or more, more preferably 0.1% by weight or more, even more preferably 0.3% by weight or more, and particularly preferably 0.4% by weight or more. 0.5 ] is 18.5 to 21.5 linear or branched monoalcohol, and HSP value at 25 ° C [(MPa) 0.5

[0049] When the solvent (X) is at least one selected from the group consisting of monoalcohols having an alicyclic skeleton of 21.6 to 23, the content of the organic acid in the mixed liquid (A) is, for example, preferably 4.9% by weight or less, more preferably 4.5% by weight or less, even more preferably 4% by weight or less, still more preferably 3% by weight or less, and particularly preferably 2% by weight or less. In particular, when the solvent (X) is at least one selected from the group consisting of cyclohexanol, 1-hexanol, 1-heptanol, 2-octanol, and 2-ethylhexanol, the content of the organic acid in the mixed liquid (A) is more preferably 0.1 to 4% by weight, even more preferably 0.3 to 3% by weight, and particularly preferably 0.4 to 2% by weight.

[0103] Furthermore, when the solvent (X) is water, the content of the organic acid in the mixed liquid (A) is, for example, preferably 30% by weight or less, more preferably 20% by weight or less, even more preferably 15% by weight or less, even more preferably 10% by weight or less, even more preferably 7% by weight or less, even more preferably 4.9% by weight or less, and even more preferably 4% by weight or less. Furthermore, the content of the organic acid in the mixed liquid (A) 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, and even more preferably 0.2% by weight or more. When the amount of the organic acid in the mixed liquid (A) is within the above range, the ionic liquid and the organic acid can be separated from the mixed liquid (A), and the ionic liquid can be recovered simply and efficiently.

[0104] [Solvent (X)] Next, the solvent (X) will be described. The solvent (X) may already be contained in the mixed liquid (B), may be newly blended into the mixed liquid (B), or may already be contained in the mixed liquid (B) and further blended into the mixed liquid (B). The solvent (X) has the function of separating the ionic liquid and the organic acid when the mixed liquid (A) is subjected to a distillation operation. The solvent (X) is not particularly limited as long as it is a solvent other than the organic acid, and examples thereof include polar solvents such as water, alcohols, alkanediols, amides, lactams, sulfoxides, sulfones, ethers, ketones, nitriles, and esters. Only one type of solvent (X) may be used, or two or more types may be used.

[0105] Examples of the alcohols include linear or branched monoalcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutanol, tert-butanol, tert-pentanol, 1-hexanol, 2-hexanol, 2-ethylhexanol, tert-butylcarbinol, 1-heptanol, 2-heptanol, 1-octanol, 2-octanol, and allyl alcohol (preferably C 1-12 Monoalcohols, more preferably C 3-10 Monoalcohols, particularly preferably C 5-8 monoalcohols); monoalcohols having an alicyclic skeleton such as cyclohexanol (preferably C 3-12 Monoalcohols, particularly preferably C 5-10 Examples of the alkanediols include 1,2-C monoalcohols such as 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, and 1,2-heptanediol. 1-12 Alkanediols: 1,3-C alkanediols such as 1,3-hexanediol, 1,3-heptanediol, and 2-ethyl-1,3-hexanediol 1-12 Examples of the amides include N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMAc). Examples of the lactams include 2-pyrrolidone, N-methyl-2-pyrrolidone (NMP), and N-vinyl-2-pyrrolidone. Examples of the sulfoxides include dimethyl sulfoxide (DMSO). Examples of the sulfones include cyclic sulfones such as sulfolane. Examples of the ethers include diethyl ether, 1,3-dioxolane, 1,4-dioxane, and tetrahydrofuran. Examples of the ketones include acetone, methyl ethyl ketone, and methyl isobutyl ketone. Examples of the nitriles include acetonitrile. Examples of the esters include methyl acetate, ethyl acetate, and butyl acetate.

[0106] HSP value of solvent (X) at 25 ° C [(MPa) 0.5] is not particularly limited, but is, for example, preferably 15 or more, more preferably 18 or more, and even more preferably 20 or more. The upper limit of the HSP value is also not particularly limited, but is, for example, preferably 80, more preferably 60, even more preferably 50, even more preferably 40, even more preferably 30, even more preferably 25, even more preferably 22, and even more preferably 21. When the HSP value of the solvent (X) at 25 ° C. is within the above range, the ionic liquid tends to be easily and efficiently recovered from the mixed liquid (A). Note that the HSP value [(MPa) 0.5 ] is determined by the Hansen method (Allan F. M. Barton. Chem. Rev., 1975, 75(6), pp731-753) and is represented by the following formula: HSP value = (δ D 2 +δ P 2 +δ H 2 ) 0.5 Dispersion term δ D : Energy due to intermolecular dispersion forces Polar term δ P : Energy due to intermolecular dipole interactions Hydrogen bond term δ H : Energy due to hydrogen bonds between molecules

[0107] The HSP value may be obtained using various estimation methods (such as the atomic group contribution method and computer simulation), and can be calculated using, for example, computer software Hansen Solubility Parameters in Practice (HSPiP).

[0108] From the viewpoint of easily and efficiently recovering the ionic liquid from the mixed liquid (A), the solvent (X) is preferably water, alcohols, amides, lactams, or sulfoxides, and more preferably a solvent having an HSP value at 25°C [(MPa) 0.5 a linear or branched monoalcohol having an HSP value at 25°C [(MPa) 0.5a monoalcohol having an alicyclic skeleton having an HSP value at 25°C [(MPa) 0.5 ] is 15 to 30 (more preferably 18 to 28, even more preferably 20 to 27, particularly preferably 23 to 26); 0.5 ] is 15 to 30 (more preferably 18 to 28, even more preferably 20 to 27, particularly preferably 22.5 to 25); lactams having an HSP value at 25 ° C. [(MPa) 0.5 ] is 15 to 30 (more preferably 20 to 29, and even more preferably 23 to 28).

[0109] In the method of the present disclosure, the solvent (X) is a solvent having an HSP value at 25 ° C. [(MPa) 0.5 ] is 18.5 to 21.5, and a linear or branched monoalcohol having an HSP value at 25 ° C. [(MPa) 0.5

[0039] is preferably at least one selected from the group consisting of monoalcohols having an alicyclic skeleton in which the .gamma.-(N-octanol) is 21.6 to 23 (referred to as solvent (X1)), and among these, at least one selected from the group consisting of cyclohexanol, 1-hexanol, 1-heptanol, 2-octanol, and 2-ethylhexanol (referred to as solvent (X2)) is more preferred, and at least one selected from the group consisting of 1-hexanol, 1-heptanol, 2-octanol, and 2-ethylhexanol (referred to as solvent (X3)) is even more preferred. Solvent (X1) has an extremely strong ability to separate the ionic liquid from the organic acid, and therefore allows the ionic liquid to be recovered simply and efficiently.

[0110] Furthermore, as the solvent (X), it is preferable to use the following solvents (X'1), (X'2), (X'3), (X'4) and (X'5) (hereinafter collectively referred to as solvent (X'N)) in combination with the above-mentioned solvents (X1), (X2) and (X3) (hereinafter collectively referred to as solvent (XN)). As the solvent (X) to be used in combination with the solvent (XN), from the viewpoints of compatibility with the ionic liquid and solubility of the esterified polysaccharide, at least one solvent (referred to as solvent (X'1)) selected from the group consisting of amides, lactams, sulfoxides and sulfones is preferred, and the HSP value at 25°C [(MPa) 0.5 ] is 23 to 26, and the HSP value at 25 ° C [(MPa) 0.5 At least one solvent selected from the group consisting of lactams having an HSP value [(MPa)0.5] at 25°C of 22.5 to 25, sulfoxides having an HSP value [(MPa)0.5] at 25°C of 23 to 28, and sulfones having an HSP value [(MPa)0.5] at 25°C of 24 to 28 (referred to as solvent (X'2)) is more preferred, at least one solvent selected from the group consisting of N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), and dimethyl sulfoxide (DMSO) (referred to as solvent (X'3)) is even more preferred, at least one solvent selected from the group consisting of N,N-dimethylformamide (DMF) and N-methyl-2-pyrrolidone (NMP) (referred to as solvent (X'4)) is even more preferred, and N-methyl-2-pyrrolidone (NMP) (solvent (X'5)) is particularly preferred. That is, the solvent (X) to be used in combination with the solvent (XN) is preferably the solvent (X'N).

[0111] The solvent (X'N) 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). That is, when the mixed liquid (A) contains the solvent (X'N), the process for including the solvent (X'N) may be any of the above. When the solvent (X'N) is already contained in the mixed liquid (B) from the beginning, the solvent (X'N) may be included as the solvent (S). That is, when the mixed liquid (B) is the mixed liquid (B1), the solvent (S) becomes the solvent (X'N) as it is when the mixed liquid (A) is obtained.

[0112] The boiling point of the solvent (X) is not particularly limited, but is, for example, preferably 20 to 300° C., more preferably 40 to 280° C., and even more preferably 50 to 250° C. When the solvent (X) contains two or more solvents, the boiling point may be the value for a mixture of the two or more solvents.

[0113] The latent heat of vaporization of the solvent (X) is not particularly limited, but is, for example, preferably 40 to 1000 kcal / kg, more preferably 60 to 800 kcal / kg, and even more preferably 80 to 600 kcal / kg. When the solvent (X) contains two or more solvents, the latent heat of vaporization may be the value for a mixture of the two or more solvents.

[0114] The content of solvent (X) contained in mixed liquid (A) is not particularly limited, but is preferably 9.09 wt% or more, more preferably 16.7 wt% or more, even more preferably 23.1 wt% or more, even more preferably 28.6 wt% or more, and particularly preferably 33.3 wt% or more. The content of solvent (X) contained in mixed liquid (A) is not particularly limited, but is preferably 99.1 wt% or less, more preferably 98.8 wt% or less, even more preferably 98.4 wt% or less, even more preferably 98.0 wt% or less, even more preferably 97.6 wt% or less, even more preferably 90 wt% or less, and even more preferably 80 wt% or less. When solvent (X) is blended with mixed liquid (B), it is preferable to prepare the resulting mixed liquid (A) so that it is within the above range.

[0115] The amount of solvent (X) blended into mixed liquid (B) is, for example, preferably 10 to 10,000 parts by weight, more preferably 20 to 8,000 parts by weight, even more preferably 30 to 6,000 parts by weight, even more preferably 40 to 5,000 parts by weight, and even more preferably 50 to 4,000 parts by weight, relative to 100 parts by weight of mixed liquid (B). When the amount of solvent (X) blended into mixed liquid (B) is within the above range, the ionic liquid tends to be easily and efficiently recovered from mixed liquid (A).

[0116] The amount of solvent (X) per mole of ionic liquid blended into the mixed solution (B) is, for example, preferably 1 mole or more, more preferably 3 moles or more, even more preferably 5 moles or more, even more preferably 7 moles or more, even more preferably 10 moles or more, and even more preferably 15 moles or more. The amount of solvent (X) per mole of ionic liquid blended into the mixed solution (B) is, for example, preferably 500 moles or less, more preferably 300 moles or less, even more preferably 200 moles or less, even more preferably 100 moles or less, and even more preferably 80 moles or less. The preferred range of the amount of solvent (X) per mole of ionic liquid blended into the mixed solution (B) is 1 to 500 moles, more preferably 3 to 300 moles, even more preferably 5 to 200 moles, even more preferably 7 to 100 moles, and particularly preferably 10 to 80 moles. By having the amount of solvent (X) within the above range, the ionic liquid in the mixed solution (A) tends to be recovered in high yield.

[0117] When the solvent (X) contained in the mixed liquid (A) is a combination of solvent (XN) and solvent (X'N), the preferred amounts of solvent (XN) and solvent (X'N) will be described. The amount of solvent (XN) per mole of solvent (X'N) is preferably 1 mole or more, more preferably 5 moles or more, and even more preferably 10 moles or more. The amount of solvent (XN) per mole of solvent (X'N) is preferably 500 moles or less, more preferably 300 moles or less, and even more preferably 200 moles or less. The amount of solvent (XN) per mole of solvent (X'N) is preferably 1 to 500 moles, more preferably 5 to 300 moles, and even more preferably 10 to 200 moles. The above-mentioned preferred ranges of the amounts of solvent (XN) and solvent (X'N) are also applicable when they are incorporated into the mixed liquid (B).

[0118] [Composition, composition for distillation] This embodiment encompasses a composition containing an ionic liquid, an organic acid, and a solvent (X). With this composition, the ionic liquid and the organic acid can be separated by distillation under normal pressure or reduced pressure, and a mixed liquid containing the ionic liquid and the solvent (X) can be suitably obtained. The composition in this embodiment is preferably for distillation. Hereinafter, it will be described as a composition for distillation.

[0119] Preferred embodiments of the ionic liquid contained in the distillation composition are the same as the preferred embodiments described in the above section [Ionic Liquid]. Preferred embodiments of the organic acid contained in the distillation composition are the same as the preferred embodiments described in the above section [Organic Acid]. Preferred embodiments of the solvent (X) contained in the distillation composition are the same as the preferred embodiments described in the above section [Solvent (X)]. Preferred distillation conditions for the distillation composition are the same as the preferred embodiments described in the above section [Distillation]. In particular, the above-mentioned mixed liquid (A) can be read as the distillation composition, and the types and amounts of preferred components, distillation conditions, etc. can be referenced. The distillation composition is obtained by blending the solvent (X) with the mixed liquid (B) containing the ionic liquid and the organic acid. Therefore, the types and amounts of preferred components, distillation conditions, etc. of the distillation composition can be referenced not only for the mixed liquid (A) but also for the mixed liquid (B).

[0120] 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.

[0121] The present disclosure will be explained in more detail below using examples, but the present disclosure is not limited to these examples.

[0122] The specifications of the evaporator used in the examples are as follows: Product name: Rotary evaporator N-1110 Manufacturer: Tokyo Rikakikai Co., Ltd.

[0123] The specifications of the NMR apparatus used in the examples are as follows: Product name: JNM-ECZ600R Manufacturer: JEOL Ltd.

[0124] Example 1 Water / Acetic Acid / EmimOAc 3.92 g of water (HSP value = 47.8 (MPa) 0.5 A mixed solution containing 0.26 g of water, 0.26 g of acetic acid, and 0.74 g of EmimOAc (water:acetic acid:EmimOAc (molar ratio) = 50:1:1) was prepared. This mixed solution was evaporated for 30 minutes under conditions of 25 hPa and 60 ° C. The residual liquid in the flask was sampled, and the composition of the flask residual liquid calculated from the NMR quantification results was acetic acid:EmimOAc (molar ratio) = 0.58:1. This showed that 41.4 wt % of acetic acid was distilled off by adding water.

[0125] Example 2 Methanol / Acetic Acid / EmimOAc 6.96 g of methanol (HSP value = 29.4 (MPa) 0.5 A mixed solution containing 0.28 g of methanol, 0.28 g of acetic acid, and 0.74 g of EmimOAc (methanol:acetic acid:EmimOAc (molar ratio) = 50:1:1) was prepared. This mixed solution was evaporated for 3 hours under conditions of 25 hPa and 60 °C. The residual liquid in the flask was sampled, and the composition of the flask residual liquid calculated from the NMR quantification results was acetic acid:EmimOAc (molar ratio) = 0.96:1, which indicated that 10.5 wt% of acetic acid was distilled off by adding methanol.

[0126] Example 3 DMSO / Acetic Acid / EmimOAc 17.00 g of DMSO (dimethyl sulfoxide, HSP value = 26.7 (MPa) 0.5 A mixed solution containing 0.26 g of acetic acid and 0.75 g of EmimOAc (DMSO:acetic acid:EmimOAc (molar ratio) = 50:1:1) was prepared. This mixed solution was evaporated for 16 hours under conditions of 10 hPa and 95 °C. The residual liquid in the flask was sampled, and the composition of the flask residual liquid calculated from the NMR quantification results was acetic acid:EmimOAc (molar ratio) = 0.64:1. This shows that 36.8 wt% of acetic acid was distilled off by adding DMSO.

[0127] Example 4 Ethanol / Acetic Acid / EmimOAc 10.00 g of ethanol (HSP value = 26.5 (MPa) 0.5 A mixed solution containing 0.26 g of ethanol, 0.26 g of acetic acid, and 0.75 g of EmimOAc (ethanol:acetic acid:EmimOAc (molar ratio) = 50:1:1) was prepared. This mixed solution was evaporated for 1 hour under conditions of 10 hPa and 60 °C. The residual liquid in the flask was sampled, and the composition of the flask residual liquid calculated from the NMR quantification results was acetic acid:EmimOAc (molar ratio) = 0.91:1. This shows that 7.6 wt% of acetic acid was distilled off by adding ethanol.

[0128] Example 5 DMF / Acetic Acid / EmimOAc 15.85 g of DMF (N,N-dimethylformamide, HSP value = 24.9 (MPa) 0.5 A mixed solution containing 0.26 g of DMF, 0.26 g of acetic acid, and 0.74 g of EmimOAc (DMF:acetic acid:EmimOAc (molar ratio) = 50:1:1) was prepared. This mixed solution was evaporated for 16 hours under conditions of 10 hPa and 65 °C. The residual liquid in the flask was sampled, and the composition of the flask residual liquid calculated from the NMR quantification results was acetic acid:EmimOAc (molar ratio) = 0.76:1. This shows that 23.2 wt% of acetic acid was distilled off by adding DMF.

[0129] Example 6 1-propanol / acetic acid / EmimOAc 13.07 g of 1-propanol (HSP value = 24.6 (MPa)0.5 A mixed solution containing 0.27 g of acetic acid, 0.74 g of EmimOAc (1-propanol:acetic acid:EmimOAc (molar ratio) = 50:1:1) was prepared. This mixed solution was evaporated for 3 hours under conditions of 10 hPa and 60°C. The residual liquid in the flask was sampled, and the composition of the flask residual liquid calculated from the NMR quantification results was acetic acid:EmimOAc (molar ratio) = 0.88:1, which indicated that 17.6 wt% of acetic acid was distilled off by adding 1-propanol.

[0130] Example 7 2-Propanol / Acetic Acid / EmimOAc 13.05 g of 2-propanol (HSP value = 23.6 (MPa) 0.5 A mixed solution containing 0.27 g of acetic acid, 0.73 g of EmimOAc (2-propanol:acetic acid:EmimOAc (molar ratio) = 50:1:1) was prepared. This mixed solution was evaporated for 30 minutes under conditions of 10 hPa and 60°C. The residual liquid in the flask was sampled, and the composition of the flask residual liquid calculated from the NMR quantification results was acetic acid:EmimOAc (molar ratio) = 0.95:1, which indicated that 8.6 wt% of acetic acid was distilled off by adding 2-propanol.

[0131] Example 8 1-butanol / acetic acid / EmimOAc 15.83 g of 1-butanol (HSP value = 23.2 (MPa) 0.5 A mixed solution containing 0.27 g of acetic acid, 0.74 g of EmimOAc (1-butanol:acetic acid:EmimOAc (molar ratio) = 50:1:1) was prepared. This mixed solution was evaporated for 2.5 hours under conditions of 10 hPa and 60°C. The residual liquid in the flask was sampled, and the composition of the flask residual liquid calculated from the NMR quantification results was acetic acid:EmimOAc (molar ratio) = 0.80:1, which indicated that 27.8 wt% of acetic acid was distilled off by adding 1-butanol.

[0132] Example 9 NMP / Acetic Acid / EmimOAc 21.56 g of NMP (N-methyl-2-pyrrolidone, HSP value = 23.0 (MPa) 0.5A mixed solution containing 0.27 g of NMP, 0.27 g of acetic acid, and 0.77 g of EmimOAc (NMP:acetic acid:EmimOAc (molar ratio) = 50:1:1) was prepared. This mixed solution was evaporated for 16 hours under conditions of 10 hPa and 105°C. The residual liquid in the flask was sampled, and the composition of the flask residual liquid calculated from the NMR quantification results was acetic acid:EmimOAc (molar ratio) = 0.47:1. This shows that 54.8 wt% of acetic acid was distilled off by adding NMP.

[0133] Example 10 Cyclohexanol / Acetic Acid / EmimOAc 21.77 g of cyclohexanol (HSP value = 22.4 (MPa) 0.5 A mixed solution containing 0.26 g of acetic acid and 0.75 g of EmimOAc (cyclohexanol: acetic acid: EmimOAc (molar ratio) = 50:1:1) was prepared. This mixed solution was evaporated for 16 hours under conditions of 10 hPa and 90 ° C. The residual liquid in the flask was sampled, and the composition of the flask residual liquid calculated from the NMR quantification results was acetic acid: EmimOAc (molar ratio) = 0.22:1, which indicated that 77.7 wt % of acetic acid was distilled off by adding cyclohexanol.

[0134] Example 11 2-butanol / acetic acid / EmimOAc 16.12 g of 2-butanol (HSP value = 22.2 (MPa) 0.5 A mixed solution containing 0.27 g of acetic acid, 0.74 g of EmimOAc (2-butanol:acetic acid:EmimOAc (molar ratio) = 50:1:1) was prepared. This mixed solution was evaporated at 10 hPa and 60°C for 2.5 hours. The residual liquid in the flask was sampled, and the composition of the flask residual liquid calculated from the NMR quantification results was acetic acid:EmimOAc (molar ratio) = 0.93:1, indicating that 8.5 wt% of acetic acid was distilled off by adding 2-butanol.

[0135] Example 12 tert-butyl alcohol / acetic acid / EmimOAc 16.1 g of tert-butyl alcohol (HSP value = 21.8 (MPa) 0.5A mixed solution containing 0.26 g of acetic acid, 0.75 g of EmimOAc (tert-butyl alcohol:acetic acid:EmimOAc (molar ratio) = 50:1:1) was prepared. This mixed solution was evaporated for 1 hour under conditions of 10 hPa and 60°C. The residual liquid in the flask was sampled, and the composition of the flask residual liquid calculated from the NMR quantification results was acetic acid:EmimOAc (molar ratio) = 0.94:1. This shows that 4.9 wt% of acetic acid was distilled off by adding tert-butyl alcohol.

[0136] Example 13 1-Hexanol / Acetic Acid / EmimOAc 22.20 g of 1-hexanol (HSP value = 21.0 (MPa) 0.5 A mixed solution containing 1-hexanol, 0.27 g of acetic acid, and 0.73 g of EmimOAc (1-hexanol:acetic acid:EmimOAc (molar ratio) = 50:1:1) was prepared. This mixed solution was evaporated for 2.5 hours under conditions of 10 hPa and 85°C. The residual liquid in the flask was sampled, and the composition of the flask residual liquid calculated from the NMR quantification results was acetic acid:EmimOAc (molar ratio) = 0.18:1, which indicated that 82.8 wt% of acetic acid was distilled off by adding 1-hexanol.

[0137] Example 14 1-heptanol / acetic acid / EmimOAc 25.44 g of 1-heptanol (HSP value = 20.5 (MPa) 0.5 A mixed solution containing 0.27 g of acetic acid, 0.73 g of EmimOAc (1-heptanol:acetic acid:EmimOAc (molar ratio) = 50:1:1) was prepared. This mixed solution was evaporated for 2.5 hours under conditions of 10 hPa and 90°C. The residual liquid in the flask was sampled, and the composition of the flask residual liquid calculated from the NMR quantification results was acetic acid:EmimOAc (molar ratio) = 0.004:1, which indicated that 99.6 wt% of the acetic acid was distilled off by adding 1-heptanol.

[0138] Example 15 2-Octanol / Acetic Acid / EmimOAc 28.25 g of 2-octanol (HSP value = 20.1 (MPa) 0.5A mixed solution containing 0.26 g of acetic acid, 0.75 g of EmimOAc (2-octanol:acetic acid:EmimOAc (molar ratio) = 50:1:1) was prepared. This mixed solution was evaporated for 16 hours under conditions of 10 hPa and 100°C. The residual liquid in the flask was sampled, and the composition of the flask residual liquid calculated from the NMR quantification results was acetic acid:EmimOAc (molar ratio) = 0.002:1, indicating that 99.8 wt% of the acetic acid was distilled off by adding 2-octanol.

[0139] Example 16 2-Ethylhexanol / Acetic Acid / EmimOAc 28.29 g of 2-ethylhexanol (HSP value = 20.1 (MPa) 0.5 A mixed solution containing 0.26 g of acetic acid, 0.75 g of EmimOAc (2-ethylhexanol:acetic acid:EmimOAc (molar ratio) = 50:1:1) was prepared. This mixed solution was evaporated for 16 hours under conditions of 10 hPa and 105°C. The residual liquid in the flask was sampled, and the composition of the flask residual liquid calculated from the NMR quantification results was acetic acid:EmimOAc (molar ratio) = 0.01:1, indicating that 98.9 wt% of the acetic acid was distilled off by adding 2-ethylhexanol.

[0140] Example 17 Water / Acetic Acid / EmimOAc 0.82 g of water (HSP value = 47.8 (MPa) 0.5 A mixed solution containing 0.26 g of water, 0.26 g of acetic acid, and 0.74 g of EmimOAc (water:acetic acid:EmimOAc (molar ratio) = 10:1:1) was prepared. This mixed solution was evaporated for 30 minutes using an evaporator under conditions of 25 hPa and 60 ° C. The residual liquid in the flask was sampled, and the composition of the flask residual liquid calculated from the NMR quantification results was acetic acid:EmimOAc (molar ratio) = 0.94:1. This shows that 5.3 wt % of acetic acid was distilled off by adding water.

[0141] Example 18 Water / Acetic Acid / EmimOAc 1.62 g of water (HSP value = 47.8 (MPa) 0.5A mixed solution containing 0.26 g of water, 0.26 g of acetic acid, and 0.74 g of EmimOAc (water:acetic acid:EmimOAc (molar ratio) = 20:1:1) was prepared. This mixed solution was evaporated for 30 minutes using an evaporator at 25 hPa and 60 °C. The residual liquid in the flask was sampled, and the composition of the flask residual liquid calculated from the NMR quantification results was acetic acid:EmimOAc (molar ratio) = 0.74:1. This shows that 26.4 wt% of acetic acid was distilled off by adding water.

[0142] Example 19 Water / Acetic Acid / EmimOAc 7.97 g of water (HSP value = 47.8 (MPa) 0.5 A mixed solution containing 0.26 g of acetic acid and 0.74 g of EmimOAc (water:acetic acid:EmimOAc (molar ratio) = 100:1:1) was prepared. This mixed solution was evaporated for 30 minutes using an evaporator at 25 hPa and 60 °C. The residual liquid in the flask was sampled, and the composition of the flask residual liquid calculated from the NMR quantification results was acetic acid:EmimOAc (molar ratio) = 0.41:1. This shows that 59.1 wt% of acetic acid was distilled off by adding water.

[0143] Example 20 Water / Acetic Acid / EmimOAc 15.66 g of water (HSP value = 47.8 (MPa) 0.5 A mixed solution containing 0.26 g of acetic acid and 0.74 g of EmimOAc (water:acetic acid:EmimOAc (molar ratio) = 200:1:1) was prepared. This mixed solution was evaporated for 30 minutes using an evaporator under conditions of 25 hPa and 60 ° C. The residual liquid in the flask was sampled, and the composition of the flask residual liquid calculated from the NMR quantification results was acetic acid:EmimOAc (molar ratio) = 0.32:1. This shows that 68.1 wt % of acetic acid was distilled off by adding water.

[0144] Example 21 Water / Acetic Acid / EmimOAc 23.49 g of water (HSP value = 47.8 (MPa) 0.5A mixed solution containing 0.26 g of acetic acid and 0.74 g of EmimOAc (water:acetic acid:EmimOAc (molar ratio) = 300:1:1) was prepared. This mixed solution was evaporated for 30 minutes using an evaporator under conditions of 25 hPa and 60 ° C. The residual liquid in the flask was sampled, and the composition of the flask residual liquid calculated from the NMR quantification results was acetic acid:EmimOAc (molar ratio) = 0.27:1. This shows that 73.3 wt % of acetic acid was distilled off by adding water.

[0145] Example 22: 2-Octanol / NMP / Acetic Acid / EmimOAc 38.1 parts by weight of 2-octanol, 1 part by weight of NMP, 0.17 parts by weight of acetic acid, and 1 part by weight of EmimOAc were prepared. Next, these four components were mixed to obtain a mixed solution (2-octanol:NMP:acetic acid:EmimOAc (molar ratio) = 50:1.72:0.50:1). Next, batch distillation was performed on this mixed solution. Note that, for the batch distillation, an Oldershaw 20-plate distillation column was used. Regarding the batch distillation process, (1) the overhead pressure was reduced stepwise from atmospheric pressure to 26.6 hPa, (2) once the pressure stabilized, the temperature was increased under total reflux conditions, (3) once the temperature in the column stabilized, the temperature was maintained under total reflux conditions for 1 hour, (4) the reflux ratio was changed to 5, and distillation was initiated, and (5) a sample was taken 30 minutes after the distillation time, and the composition was analyzed. The oil bath temperature was set to 150° C. As a result, all of the acetic acid was distilled off 30 minutes after the total reflux operation. In other words, by blending 2-octanol and NMP, it was possible to remove all of the acetic acid.

[0146] Example 23 The structural formula of the EmimOAc recovered in Example 1 is the same as that of the EmimOAc before distillation (i.e., before evaporation).

[0147] Example 24 When cellulose (0.18, Sigma-Aldrich trade name "Avicel PH-101", number average degree of polymerization 105) was mixed with each of the EmimOAc (1 g) recovered in Examples 1, 13, 14, 15, 16, and 22 and stirred, the cellulose dissolved. This phenomenon proves that the ionic liquid recovered by the method of the present disclosure can be reused.

[0148] Comparative Example 1 (No Solvent Used) A mixed solvent containing 52 g of acetic acid and 148 g of EmimOAc (acetic acid:EmimOAc (molar ratio) = 1.0:1.0) was prepared and heated to 145°C at 53 hPa. However, under these conditions, no distillate was obtained, and it was found that a gas-liquid equilibrium state was not reached. In other words, it was found that when no solvent was blended into the mixed solvent, it was impossible to distill off acetic acid.

[0149] Comparative Example 2 (No Solvent Used) A mixed solvent containing 69 g of acetic acid and 131 g of EmimOAc (acetic acid:EmimOAc (molar ratio) = 1.5:1.0) was prepared and heated to 145°C at 53 hPa. However, under these conditions, no distillate was obtained, and it was found that a gas-liquid equilibrium state was not reached. In other words, it was found that when no solvent was blended into the mixed solvent, it was impossible to distill off acetic acid.

[0150] Comparative Example 3: No Solvent Used A mixed solvent containing 80 g of acetic acid and 120 g of EmimOAc (acetic acid:EmimOAc (molar ratio) = 1.9:1.0) was prepared and heated to 145°C at 53 hPa. However, under these conditions, no distillate was obtained, and it was found that a gas-liquid equilibrium state was not reached. In other words, it was found that when no solvent was blended into the mixed solvent, it was impossible to distill off acetic acid.

[0151] [Supplementary explanation for Examples 1 to 22] In Examples 1 to 21, the weight percentages of EmimOAc and acetic acid in the mixture before evaporation under reduced pressure are shown below. In Example 22, the weight percentages of EmimOAc and acetic acid in the mixture before batch distillation are shown below. Example 1: EmimOAc 15.0 wt%, acetic acid 5.31 wt% Example 2: EmimOAc 9.29 wt%, acetic acid 3.28 wt% Example 3: EmimOAc 4.11 wt%, acetic acid 1.45 wt% Example 4: EmimOAc 6.72 wt%, acetic acid 2.37 wt% Example 5: EmimOAc 4.38 wt%, acetic acid 1.55 wt% Example 6: EmimOAc 5.26 wt%, acetic acid 1.86 wt% Example 7: EmimOAc 5.26 wt%, acetic acid 1.86 wt% Example 8: EmimOAc 4.32 wt%, acetic acid 1.53 wt% Example 9: EmimOAc Example 10: EmimOAc 3.28% by weight, acetic acid 1.16% by weight Example 11: EmimOAc 4.32% by weight, acetic acid 1.53% by weight Example 12: EmimOAc 4.32% by weight, acetic acid 1.53% by weight Example 13: EmimOAc 3.19% by weight, acetic acid 1.12% by weight Example 14: EmimOAc 2.82% by weight, acetic acid 0.99% by weight Example 15: EmimOAc 2.52% by weight, acetic acid 0.89% by weight Example 16: EmimOAc 2.52% by weight, acetic acid 0.89% by weight Example 17: 41.5 wt% EmimOAc, 14.6 wt% acetic acid Example 18: 28.8 wt% EmimOAc, 10.2 wt% acetic acid Example 19: 8.38 wt% EmimOAc, 2.96 wt% acetic acid Example 20: 4.44 wt% EmimOAc, 1.57 wt% acetic acid Example 21: 3.02 wt% EmimOAc, 1.07 wt% acetic acid Example 22: 2.48 wt% EmimOAc, 0.42 wt% acetic acid

[0152] To summarize the above, the configuration of the present invention and its variations are described below. [1] A method for recovering an ionic liquid, characterized by distilling a mixed liquid (A) containing an ionic liquid, an organic acid, and a solvent (excluding the organic acid) (i.e., "solvent (X)"). [2] The method for recovering an ionic liquid according to [1], characterized by blending a solvent (excluding the organic acid) with a mixed liquid (B) containing the ionic liquid and the organic acid, and distilling the resulting mixture. [3] The method for recovering an ionic liquid according to [2], wherein the mixed liquid (B) is a mixed liquid containing a reaction product obtained when a specific raw material is esterified with an esterifying agent using an ionic liquid as a solvent. [4] The method for recovering an ionic liquid according to [3], wherein the raw material is a polysaccharide (e.g., at least one 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). [5] The method for recovering an ionic liquid according to [3] or [4], 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. [6] The method for recovering an ionic liquid according to [5], 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. [7] The method for recovering an ionic liquid according to any one of [2] to [6], wherein the mixed liquid (B) contains a solvent (solvent (S)) other than the ionic liquid.[8] 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. 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). [9] The method for recovering an ionic liquid according to any one of [1] to [8], wherein the mixed liquid (A) is subjected to a distillation operation without undergoing pretreatment.

[10] The method for recovering an ionic liquid according to any one of [1] to [9], wherein the temperature during distillation of the mixed liquid (A) is 0°C or higher, 10°C or higher, 15°C or higher, 20°C or higher, 400°C or lower, 350°C or lower, 300°C or lower, 250°C or lower, 200°C or lower, 150°C or lower, 130°C or lower, 100°C or lower, 95°C or lower, 90°C or lower, 0 to 150°C, 10 to 130°C, 15 to 100°C, 20 to 95°C, 20 to 90°C, and / or 20 to 150°C.

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

[10] , wherein the pressure during distillation of the mixed liquid (A) is 0.1 hPa or more, 0.5 hPa or more, 0.8 hPa or more, 1 hPa or more, 5 hPa or more, 1519 hPa or less, 1013 hPa or less, 1000 hPa or less, 800 hPa or less, 500 hPa or less, 300 hPa or less, 100 hPa or less, 50 hPa or less, 0.5 to 1519 hPa, 1 to 1013 hPa, and / or 5 to 100 hPa.

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

[11] , wherein the structural formula of the recovered ionic liquid is the same as the structural formula of the ionic liquid (in the mixed liquid (A) or the mixed liquid (B)) before distillation.

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

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

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

[12] , 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. 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.

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

[13] or

[14] , 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.

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

[13] to

[15] , wherein the piperidinium cation is a cation represented by the 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.

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

[13] to

[16] , 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.

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

[13] to

[17] , 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.

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

[13] to

[18] , wherein the ionic liquid is a phosphonium cation represented by the formula (I) or (II), and the anion components thereof are selected from the group consisting of a halogen anion, a pseudohalogen anion, a carboxylate anion, a phosphate anion, an amino acid anion, a phenolate, a pyrimidine olate, a tetrafluoroborate ion (BF 4- ), sulfomethyl ion (CH3SO3 - ), methylphosphonate, sulfate ion, and PF6 -

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

[19] , wherein the ionic liquid contains at least one selected from the group consisting of:

[0022]

[0023]

[0024]

[0025]

[0026]

[0027]

[0028]

[0029]

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

[19] , wherein the ionic liquid contains at least one selected from the group consisting of:

[0029]

[0030]

[0031]

[0032]

[0033]

[0034]

[0035]

[0036]

[0037]

[0038]

[0039]

[0040]

[0041]

[0042]

[0043]

[0044]

[0045]

[0046]

[0047]

[0048]

[0049]

[0050]

[0051]

[0052]

[0053]

[0054]

[0055]

[0056]

[0057]

[0058]

[0059]

[0060]

[0061]

[0062]

[0063]

[0064]

[0065]

[0066]

[0067]

[0068]

[0069]

[0070]

[0071]

[0072]

[0073]

[0074]

[0075]

[0076]

[0077]

[0078]

[0079]

[0080]

[0081]

[0082]

[0083]

[0084]

[0085]

[0086]

[0087]

[0088]

[0089]

[0090] [1091 0.5 ] is 18.5 to 21.5 linear or branched monoalcohol, and HSP value at 25 ° C [(MPa) 0.5 The method for recovering an ionic liquid according to any one of [1] to

[23] , wherein the content of the ionic liquid in the mixed solution (A) is 9.9 wt % or less, 9.5 wt % or less, 9 wt % or less, 8 wt % or less, 7 wt % or less, or 5 wt % or less, when the solvent (X) is at least one selected from the group consisting of monoalcohols having an alicyclic skeleton of 21.6 to 23.

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

[24] , wherein the content of the ionic liquid in the mixed solution is 0.3 to 9 wt %, 0.5 to 8 wt %, and / or 1 to 7 wt %, when the solvent (X) is at least one selected from the group consisting of cyclohexanol, 1-hexanol, 1-heptanol, 2-octanol, and 2-ethylhexanol.

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

[25] , wherein when the solvent (X) is water, the content of the ionic liquid in the mixed solution (A) is 45% by weight or less, 40% by weight or less, 30% by weight or less, 20% by weight or less, 9.9% by weight or less, 9.5% by weight or less, 9% by weight or less, or 5% by weight or less.

[27] 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 and / or C 1-7

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

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

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

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

[28] , wherein the content of the carboxylic acid 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.

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

[29] , 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.

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

[30] , wherein the content of the organic acid in the mixed liquid (A) is 0.01% by weight or more, 0.1% by weight or more, 0.3% by weight or more, or 0.4% by weight or more.

[32] The solvent (X) has an HSP value at 25°C [(MPa) 0.5 ] is 18.5 to 21.5 linear or branched monoalcohol, and HSP value at 25 ° C [(MPa) 0.5

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

[32] , wherein the content of organic acid in mixed solution (A) is 0.1 to 4 wt %, 0.3 to 3 wt %, or 0.4 to 2 wt % when solvent (X) is at least one selected from the group consisting of monoalcohols having an alicyclic skeleton of 21.6 to 23.

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

[33] , wherein the content of organic acid in mixed solution (A) is 0.1 to 4 wt %, 0.3 to 3 wt %, or 0.4 to 2 wt % when solvent (X) is at least one selected from the group consisting of cyclohexanol, 1-hexanol, 1-heptanol, 2-octanol, and 2-ethylhexanol.

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

[33] , wherein when the solvent (X) is water, the content of organic acid in the mixed solution (A) is 30% by weight or less, 20% by weight or less, 15% by weight or less, 10% by weight or less, 7% by weight or less, 4.9% by weight or less, 4% by weight or less, 0.01% by weight or more, 0.05% by weight or more, 0.1% by weight or more, and / or 0.2% by weight or more.

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

[34] , wherein the solvent (X) is at least one selected from the group consisting of water, alcohols, alkanediols, amides, lactams, sulfoxides, sulfones, ethers, ketones, nitriles, and esters.

[36] The alcohols are linear or branched monoalcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutanol, tert-butanol, tert-pentanol, 1-hexanol, 2-hexanol, 2-ethylhexanol, tert-butylcarbinol, 1-heptanol, 2-heptanol, 1-octanol, 2-octanol, and allyl alcohol; 1-12 Monoalcohol, C 3-10 Monoalcohol, or C 5-8

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

[35] , wherein the alcohol is a monoalcohol having an alicyclic skeleton such as cyclohexanol, C 3-12 Monoalcohol, or C 5-10

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

[35] or

[36] , wherein the alkanediol is a monoalcohol.

[38] The alkanediol is a 1,2-C diol such as 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, or 1,2-heptanediol. 1-12

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

[35] to

[37] , wherein the alkanediol is a 1,3-C alkanediol such as 1,3-hexanediol, 1,3-heptanediol, or 2-ethyl-1,3-hexanediol. 1-12The method for recovering an ionic liquid according to any one of

[35] to

[38] , wherein the amide is at least one selected from the group consisting of N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMAc).

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

[35] to

[39] , wherein the amide is at least one selected from the group consisting of N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMAc).

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

[35] to

[40] , wherein the lactam is at least one selected from the group consisting of 2-pyrrolidone, N-methyl-2-pyrrolidone (NMP), and N-vinyl-2-pyrrolidone.

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

[35] to

[41] , wherein the sulfoxide is dimethyl sulfoxide (DMSO).

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

[35] to

[42] , wherein the sulfone is a cyclic sulfone such as sulfolane.

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

[35] to

[43] , wherein the ether is at least one selected from the group consisting of diethyl ether, 1,3-dioxolane, 1,4-dioxane, and tetrahydrofuran.

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

[35] to

[44] , wherein the ketone is at least one selected from the group consisting of acetone, methyl ethyl ketone, and methyl isobutyl ketone.

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

[35] to

[45] , wherein the nitrile is acetonitrile.

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

[35] to

[46] , wherein the ester is at least one selected from the group consisting of methyl acetate, ethyl acetate, and butyl acetate.

[48] The HSP value [(MPa) of the solvent (X) at 25°C 0.5

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

[48] , wherein the solvent (X) is at least one selected from the group consisting of water, alcohols, amides, lactams, and sulfoxides.

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

[48] , wherein the solvent (X) has an HSP value at 25°C [(MPa) 0.5

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

[49] , wherein the solvent (X) is a linear or branched monoalcohol having an HSP value at 25°C [(MPa) 0.5

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

[50] , wherein the solvent (X) is a monoalcohol having an alicyclic skeleton with an HSP value [(MPa) 0.5

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

[51] , wherein the solvent (X) has an HSP value at 25°C [(MPa) 0.5

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

[52] , wherein the solvent (X) is a lactam having an HSP value at 25°C [(MPa) 0.5

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

[53] , wherein the solvent (X) has an HSP value at 25°C [(MPa) 0.5 ] is 18.5 to 21.5, and the HSP value at 25 ° C. [(MPa) 0.5

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

[54] , wherein the solvent (X) is at least one selected from the group consisting of monoalcohols having an alicyclic skeleton of 21.6 to 23 (solvent (X1)); at least one selected from the group consisting of cyclohexanol, 1-hexanol, 1-heptanol, 2-octanol, and 2-ethylhexanol (solvent (X2)); or at least one selected from the group consisting of 1-hexanol, 1-heptanol, 2-octanol, and 2-ethylhexanol (solvent (X3)).

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

[54] , wherein the solvent (X) is at least one selected from the group consisting of amides, lactams, sulfoxides, and sulfones (solvent (X'1)); 0.5 ] is 23 to 26, and the HSP value at 25 ° C [(MPa) 0.5

[0033] The method for recovering an ionic liquid according to any one of [1] to

[55] , wherein the solvent is at least one selected from the group consisting of lactams having an HSP value [(MPa)0.5] at 25°C of 22.5 to 25, sulfoxides having an HSP value [(MPa)0.5] at 25°C of 23 to 28, and sulfones having an HSP value [(MPa)0.5] at 25°C of 24 to 28 (solvent (X'2)); at least one selected from the group consisting of N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), and dimethyl sulfoxide (DMSO) (solvent (X'3)); at least one selected from the group consisting of N,N-dimethylformamide (DMF) and N-methyl-2-pyrrolidone (NMP) (solvent (X'4)); or N-methyl-2-pyrrolidone (NMP) (solvent (X'5)).

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

[56] , wherein the solvent (X) is a combination of the solvent (X1), (X2), or (X3) (collectively referred to as solvent (XN)) and the solvent (X'1), (X'2), (X'3), (X'4), or (X'5) (collectively referred to as solvent (X'N)).

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

[57] , wherein the content of the solvent (X) in the mixed liquid (A) is 9.09 wt% or more, 16.7 wt% or more, 23.1 wt% or more, 28.6 wt% or more, 33.3 wt% or more, 99.1 wt% or less, 98.8 wt% or less, 98.4 wt% or less, 98.0 wt% or less, 97.6 wt% or less, 90 wt% or less, and / or 80 wt% or less.

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

[58] , wherein the amount of solvent (X) blended into the mixed solution (B) is 10 to 10,000 parts by weight, 20 to 8,000 parts by weight, 30 to 6,000 parts by weight, 40 to 5,000 parts by weight, or 50 to 4,000 parts by weight, relative to 100 parts by weight of the mixed solution (B).

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

[59] , wherein the amount of solvent (X) blended into the mixed solution (B) relative to 1 mole of the ionic liquid is 1 mole or more, 3 moles or more, 5 moles or more, 7 moles or more, 10 moles or more, 15 moles or more, 500 moles or less, 300 moles or less, 200 moles or less, 100 moles or less, 80 moles or less, 1 to 500 moles, 3 to 300 moles, 5 to 200 moles, 7 to 100 moles, and / or 10 to 80 moles.

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

[60] , wherein the solvent (X) contained in the mixed solution (A) is a combination of solvent (XN) and solvent (X'N), and the amount of solvent (XN) relative to 1 mole of solvent (X'N) is 1 mole or more, 5 moles or more, 10 moles or more, 500 moles or less, 300 moles or less, 200 moles or less, 1 to 500 moles, 5 to 300 moles, or 10 to 200 moles.

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

[61] , wherein the solvent (X) is at least one selected from the group consisting of cyclohexanol, 1-hexanol, 1-heptanol, 2-octanol, and 2-ethylhexanol, and the content of the ionic liquid in the mixed solution (A) is 0.3 to 9 wt%.

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

[62] , wherein the pressure during the distillation is 1519 hPa or less.

[64] A distillation composition containing an ionic liquid, an organic acid, and a solvent (excluding organic acids), wherein the solvent of the distillation composition is at least one selected from the group consisting of cyclohexanol, 1-hexanol, 1-heptanol, 2-octanol, and 2-ethylhexanol, the ionic liquid is at least one selected from the group consisting of EmimOAc and EDmimOAc, the organic acid is acetic acid, the content of the ionic liquid in the composition is 0.3 to 9 wt%, and the content of the organic acid in the composition is 0.1 to 4 wt%.

[0153] 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, Distillation of a mixture (A) containing an ionic liquid, an organic acid, and a solvent (except the organic acid), The ionic liquid contains one or more cation components selected from imidazolium cation, pyridinium cation, pyrrolidinium cation, piperidinium cation, quaternary ammonium cation, and quaternary phosphonium cation, A method for recovering an ionic liquid, characterized by separating the organic acid from the ionic liquid by the aforementioned distillation.

2. A method for recovering an ionic liquid according to claim 1, characterized by adding a solvent (except for the organic acid) to a mixture (B) containing an ionic liquid and an organic acid and distilling it.

3. The method for recovering an ionic liquid according to claim 1 or 2, wherein the solvent is a polar solvent.

4. HSP value of the aforementioned solvent at 25°C [(MPa)] ０．５ A method for recovering an ionic liquid according to claim 1 or 2, wherein the value of ] is 15 or more.

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

6. 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.

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

8. The method for recovering an ionic liquid according to claim 1 or 2, wherein the solvent is at least one selected from the group consisting of cyclohexanol, 1-hexanol, 1-heptanol, 2-octanol, and 2-ethylhexanol, and the content of the ionic liquid in the mixed solution (A) is 0.3 to 9% by weight.

9. The method for recovering an ionic liquid according to claim 1 or 2, wherein the pressure during the distillation is 1519 hPa or less.