Method for producing anhydro sugar alcohol

Abstract

To provide a technique for improving the yield of an anhydrosugar alcohol and an execution form of a continuous reaction and an effective production method of an anhydrosugar alcohol.SOLUTION: There is provided a method for producing an anhydrosugar alcohol which comprises: a step of conducting a dehydration reaction of a sugar alcohol in a two phase system formed from an organic solvent phase containing an organic solvent and a catalyst layer containing a catalyst; and / or a step of extracting an anhydrosugar alcohol using an organic solvent from a reaction product obtained by the dehydration reaction of a sugar alcohol, wherein a cyclic ether having 6 or more carbon atoms and a boiling point of 93°C or more is used as the organic solvent. The reaction temperature in the dehydration reaction step preferably is 93°C or more.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing anhydro sugar alcohol, and particularly to a method for producing anhydro sugar alcohol with high yield and efficiency. In the present invention, "anhydro sugar alcohol" is a general term for "monoanhydro sugar alcohol" and "dianhydro sugar alcohol".

Background Art

[0002] Conventionally, it has been known that anhydro sugar alcohol can be obtained by dehydrating and cyclizing sugar alcohols such as mannitol, iditol, sorbitol, xylitol, and erythritol. The obtained anhydro sugar alcohol can be used as a raw material or intermediate in chemical synthesis. In particular, isosorbide obtained by dehydrating and cyclizing two molecules of water from sorbitol and erythritan obtained by dehydrating and cyclizing one molecule of water from erythritol are industrially useful and can be used as raw materials for pharmaceuticals and agricultural chemicals, synthetic intermediates, electrolytes for batteries and capacitors, solvents for inks and adhesives, surfactants, and raw materials for manufacturing plastics and polymers. For example, isosorbide is useful as a raw material monomer used in the production of polyurethanes, polycarbonates, polycarbonate diols, and polyesters. In addition, sorbitol, which is the raw material of isosorbide, and erythritol, which is the raw material of erythritan, can be derived from various natural resources. Therefore, isosorbide and erythritan can be considered renewable raw materials in polymer production.

[0003] The reaction to obtain anhydro sugar alcohol by dehydration of sugar alcohol is generally carried out in the liquid phase due to the properties of the raw materials and products. Also, generally a catalyst is required, and examples of using organic or inorganic solid acid catalysts that can be separated and reused in the dehydration reaction have been reported. For example, Patent Document 1 discloses using cationic ion exchange resins such as sulfonated polystyrene and mixtures thereof as catalysts. Also, Non-Patent Documents 1 to 3 disclose using inorganic solid acids such as metal oxides doped with sulfate groups and niobic acid which is a kind of isopolyacid as catalysts. Furthermore, Patent Documents 2 and 3 disclose using acidic zeolite as a catalyst.

[0004] Since the dehydration reaction is an equilibrium reaction, in order to efficiently proceed the dehydration reaction, it has been reported that a method of removing the generated water outside the reactor is effective. In addition, when the product is isosorbide, a method of withdrawing the product together with water outside the reactor has also been proposed. For example, in the method disclosed in Patent Document 2, water, or water and isosorbide are distilled off under vacuum conditions at the reaction temperature and removed from the reaction system. Also, in the method disclosed in Patent Document 3, water, or water and isosorbide are evaporated by flowing a gas at the reaction temperature and removed from the reaction system. On the other hand, in order to avoid the reaction solution becoming viscous as the dehydration progresses, a method of using a solvent (Patent Document 4) and a method of using an autoclave or the like to prevent the generated water from going outside the reactor (Patent Document 5) have also been disclosed.

[0005] Patent Document 4 proposes a method of performing the dehydration reaction of sorbitol using xylene as a solvent, extracting the generated isosorbide with xylene, separating the extraction solvent and isosorbide thereafter, and then returning the extraction solvent to the reactor.

[0006] Also, Patent Document 6 uses a cyclic ether as a solvent, specifically THP (tetrahydropyran (C 5 H 10By performing the dehydration reaction of sorbitol using, for example, a boiling point of 88°C, etc., a method is disclosed for improving the extraction efficiency of isosorbide and avoiding side reactions such as the polymerization of isosorbide.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Non - Patent Documents

[0008]

Non - Patent Document 1

Non - Patent Document 2

Non - Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0009] However, it has been difficult to obtain anhydro sugar alcohol with high efficiency by any of the above - mentioned conventional methods. In particular, in the method using an organic solvent, although phase separation from the catalyst and raw materials can be achieved, no organic solvent has been proposed that satisfies all of the boiling point of the solvent that controls the reaction temperature, the extraction efficiency of the product, the compatibility with water, and the stability against an acid catalyst. For example, if the boiling point of the organic solvent used is low, it becomes difficult to carry out the dehydration reaction, which is an endothermic reaction, at a high reaction temperature, and the progress of the reaction is suppressed. Further, if the extraction efficiency of the product by the organic solvent is low, demerits such as the need for a large amount of solvent occur. In the case of a solvent miscible with water, more energy is required for the separation of the water produced in the dehydration reaction. These are factors that are regarded as inefficient in the manufacture of chemicals in the coming era.

[0010] The present invention has been made in view of such circumstances, and an object thereof is to provide a technique for increasing the yield of anhydro sugar alcohol, and a form for carrying out a continuous reaction and an efficient method for producing anhydro sugar alcohol.

Means for Solving the Problems

[0011] As a result of intensive studies on the method using an organic solvent among the methods for producing anhydro sugar alcohol by intramolecular dehydration of sugar alcohol in the presence of a catalyst, the present inventors have found that when a specific cyclic ether is used as the organic solvent and the dehydration reaction of sugar alcohol is carried out in the presence of this cyclic ether and a catalyst, the apparent reaction rate increases, and at the same time the product selectively migrates to the cyclic ether, facilitating the separation of the catalyst and the product after the reaction is completed, and enabling the production of anhydro sugar alcohol with high efficiency. Further, it has been found that it is also possible to continuously supply the raw material to the reactor and extract the product from the reactor, and to produce anhydro sugar alcohol with high efficiency and high quality.

[0012] That is, the gist of the present invention is as follows [1] to [6].

[0013] [1] A step of performing a dehydration reaction of a sugar alcohol in a two-phase system formed from an organic solvent phase containing an organic solvent and a catalyst phase containing a catalyst, and / or from a reaction mixture containing a catalyst obtained by the dehydration reaction of the sugar alcohol, extracting a monoanhydro sugar alcohol and / or a dianhydro sugar alcohol (hereinafter referred to as "anhydro sugar alcohol") using an organic solvent. A method for producing an anhydro sugar alcohol, comprising: The method for producing an anhydro sugar alcohol, characterized in that a cyclic ether having 6 or more carbon atoms and a boiling point of 93 °C or higher is used as the organic solvent.

[0014] [2] The method for producing an anhydro sugar alcohol according to [1], wherein the reaction temperature in the dehydration reaction step is equal to or higher than the azeotropic point of the cyclic ether and water.

[0015] [3] The method for producing an anhydro sugar alcohol according to [2], wherein the reaction temperature in the dehydration reaction step is 93 °C or higher.

[0016] [4] The method for producing an anhydro sugar alcohol according to [3], wherein the reaction temperature in the dehydration reaction step is equal to or lower than the boiling point of the cyclic ether.

[0017] [5] The method for producing an anhydro sugar alcohol according to any one of [1] to [4], wherein the cyclic ether is methyltetrahydropyran.

[0018] [6] The method for producing an anhydro sugar alcohol according to any one of [1] to [5], wherein the catalyst contains a heteropolyacid.

Advantages of the Invention

[0019] According to the present invention, a technique for producing an anhydro sugar alcohol in a high yield can be provided. That is, the cyclic ether solvent used in the present invention has a boiling point of 93 °C or higher, which is higher than that of conventional organic solvents. Therefore, it is possible to perform a dehydration reaction at a higher reaction temperature, promoting the progress of the reaction and improving the reaction rate. In addition, since it is a cyclic ether having 6 or more carbon atoms, the extraction efficiency of the product anhydro sugar alcohol is also high, and the product can be selectively extracted and recovered into the organic solvent phase efficiently without using a large amount of solvent, and the separation from the catalyst phase can also be easily performed. Thus, since the separation of the catalyst and the product after the reaction is facilitated, high-purity anhydro sugar alcohol can be easily obtained in a high yield. In addition, it becomes possible to continuously supply the raw material to the reactor and extract the product from the reactor, and it is possible to produce high-efficiency and high-quality anhydro sugar alcohol with excellent operability.

Mode for Carrying Out the Invention

[0020] Hereinafter, the present invention will be described in detail. However, the description of the constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention is not limited to these contents, and various modifications can be made within the scope of the gist thereof and implemented.

[0021] The method for producing anhydro sugar alcohol of the present invention includes a step of performing a dehydration reaction of sugar alcohol in a two-phase system formed from an organic solvent phase containing an organic solvent and a catalyst phase containing a catalyst (dehydration reaction step), and / or from a reaction mixture containing a catalyst obtained by the dehydration reaction of sugar alcohol, a step of extracting monoanhydro sugar alcohol and / or dianhydro sugar alcohol (hereinafter, these are referred to as "anhydro sugar alcohol") using an organic solvent (extraction step). The method for producing anhydro sugar alcohol is characterized in that a cyclic ether having 6 or more carbon atoms and a boiling point of 93°C or higher is used as the organic solvent. The reaction temperature in the dehydration reaction step is preferably equal to or higher than the azeotropic point of the cyclic ether used and water, more preferably 93°C or higher, and still more preferably equal to or lower than the boiling point of the cyclic ether used at 93°C or higher.

[0022] Hereinafter, the raw materials, organic solvents, catalysts, reaction conditions, etc. used in the method for producing anhydro sugar alcohol according to the present embodiment (hereinafter, may be appropriately referred to as "the production method according to the present embodiment") will be described.

[0023] (Raw materials) In the production method according to the present embodiment, a sugar alcohol (including monoanhydro sugar alcohol) is used as a raw material for the reaction, that is, a reactant for the dehydration reaction. Also included is the case where monoanhydro sugar alcohol is the raw material for the main reaction.

[0024] The sugar alcohol used as a raw material is not particularly limited, but hexitol, pentitol, and tetritol are preferred examples. More preferred sugar alcohols include sorbitol, mannitol, galactitol, iditol, xylitol, arabinitol, ribitol, erythritol, and threitol. Even more preferred sugar alcohols include sorbitol, xylitol, and erythritol, and particularly preferred is sorbitol.

[0025] When sorbitol is used as a raw material, the resulting anhydro sugar alcohol is at least one of sorbitan, which is a monoanhydro sugar alcohol, and isosorbide, which is a dianhydro sugar alcohol. Sorbitan is sorbitan formed by one - molecule dehydration from sorbitol, and preferably 1,4 - sorbitan.

[0026] Also, when xylitol is used as a raw material, a cyclized C5 monoanhydro sugar alcohol is obtained as a product. When erythritol is used as a raw material, erythritan, which is a monoanhydro sugar alcohol, is obtained as a product. When mannitol is used as a raw material, the resulting anhydro sugar alcohol is at least one of mannitane, which is a monoanhydro sugar alcohol, and isomannide, which is a dianhydro sugar alcohol.

[0027] Examples of the monoanhydro sugar alcohol used as a raw material include sorbitan, preferably 1,4-sorbitan. When sorbitan is used as a raw material, the product anhydro sugar alcohol is isosorbide, a dianhydro sugar alcohol. Therefore, the raw material may be any of sugar alcohol, monoanhydro sugar alcohol, and mixtures thereof.

[0028] In the production method of the present embodiment, as the sugar alcohol and monoanhydro sugar alcohol serving as raw materials, those derived from natural resources such as cellulose and glucose by chemical synthesis methods or saccharification fermentation methods can be used. In this case, the sugar alcohol and monoanhydro sugar alcohol derived by chemical synthesis methods or the like may be used as raw materials in a mixture state without isolation and purification, or those isolated and purified may be used.

[0029] The purity of the raw material (starting material) subjected to the dehydration reaction of this production method (for example, the content of sugar alcohol and / or monoanhydro sugar alcohol in the starting material, and the total content when both are included) is not particularly limited, but preferably the purity excluding water is 90% or more (90% by mass or more), more preferably 95% or more (95% by mass or more), and still more preferably 98% or more (98% by mass or more). By increasing the purity of the starting material, it is possible to suppress the increase in by-products caused by impurities to an extent that cannot be ignored in the dehydration reaction. Thereby, the efficiency in the separation process of by-products and the purification process of the product can be improved.

[0030] As a method of isolation and purification for increasing the purity of the raw material (starting material), there is a method using activated carbon, cation (acidic) ion exchange resin, and / or anion (basic) ion exchange resin (IER). There are no particular restrictions on the order of treatment, whether it is a batch method or a fixed-bed continuous method using a column. The combined use of multiple IERs or the use of a mixture is also preferably used. In the above-mentioned activated carbon treatment and IER treatment, the starting material (raw material) may be provided in the state of an aqueous solution dissolved in water.

[0031] Since sorbitol can be obtained by reducing glucose, it is easily available industrially. It can also be obtained by reducing sugar (glucose) solutions obtained through various saccharification and purification processes of non-edible biomass such as cellulose and wood. Therefore, among sugar alcohols as starting materials, sorbitol is particularly preferred. Sorbitan and isosorbide obtained from the dehydration reaction of sorbitol are useful as raw materials for various chemicals and pharmaceuticals, and also as raw material monomers for the production of polymers such as polyurethanes, polycarbonates, and polyesters.

[0032] (Organic solvents used in the dehydration reaction step and extraction step) In the production method of the present embodiment, the organic solvent used in the dehydration reaction step is an organic solvent that can form a two-phase system together with the catalyst phase. That is, it is preferably one that does not dissolve the catalyst, dissolves the target product anhydro sugar alcohol, and does not dissolve the starting material sugar alcohol. Also, it is preferably one that has stability under acidic conditions and does not cause reactions such as decomposition. Furthermore, it is particularly preferred that it has the property of layer separation into two phases with water and has low compatibility with water. Moreover, it is more preferable that the organic solvent has the property of azeotroping with water.

[0033] In the production method according to the present embodiment, a cyclic ether having 6 or more carbon atoms and a boiling point of 93°C or higher (where the oxygen atom, which is the functional group of the ether, is part of the ring) is used as such an organic solvent. As the cyclic ether having 6 or more carbon atoms and a boiling point of 93°C or higher, a 5-membered or 6-membered cyclic ether that is stable to acids and has substituents such as one or more alkyl groups on the ring, thereby having 6 or more carbon atoms, is preferred.

[0034] There is no particular limitation on the upper limit of the carbon number of the cyclic ether having 6 or more carbon atoms and a boiling point of 93°C or higher used in the production method according to the present embodiment, but it is usually 12 or less, preferably 10 or less. Also, there is no particular limitation on the upper limit of the boiling point, but it is usually 160°C or less, preferably 140°C or less.

[0035] Examples of such cyclic ethers include dimethyltetrahydropyran, ethyltetrahydropyran, trimethyltetrahydrofuran, ditetrahydrofurfuryl compounds, ethyltetrahydrofuran, and methyltetrahydropyran. More specifically, examples of dimethyltetrahydropyran include 2,6-dimethyltetrahydropyran, 2,5-dimethyltetrahydropyran, 2,4-dimethyltetrahydropyran, and 2,3-dimethyltetrahydropyran. Examples of ethyltetrahydropyran include 2-ethyltetrahydropyran, 3-ethyltetrahydropyran, and 4-ethyltetrahydropyran. Examples of trimethyltetrahydrofuran include 2,3,4-trimethyltetrahydrofuran and 2,3,5-trimethyltetrahydrofuran. An example of a ditetrahydrofurfuryl compound is 2,2'-ditetrahydrofurfurylpropane. Examples of methyltetrahydropyran include 2-methyltetrahydropyran, 3-methyltetrahydropyran, and 4-methyltetrahydropyran. Examples of ethyltetrahydropyran include 2-ethyltetrahydropyran, 3-ethyltetrahydropyran, and 4-ethyltetrahydropyran. Also, as the cyclic ether, a compound having a dioxolane structure, a dioxane structure, or a dioxabicyclo structure is also effective. Examples of the compound having a dioxabicyclo structure include dioxabicyclooctane and dioxabicyclodecane. Among these, methyltetrahydropyran is particularly preferred from the viewpoints of high boiling point, extraction efficiency of anhydro sugar alcohol, stability of the two-phase system with water, compatibility with water, chemical stability, etc. Among methyltetrahydrofurans, 4-methyltetrahydropyran (boiling point 105 °C) is particularly preferred. These cyclic ethers may be used alone or in combination of two or more.

[0036] The origin of these cyclic ethers, such as methyltetrahydropyran, is not particularly limited, and any kind can be used. For example, it may be produced by dehydrative cyclization of 3-methyl-1,5-pentanediol derived from fossil resources synthesized from isobutene using carbon monoxide as a carbon extender, or it may be derived from biomass-derived furfural derivatives. The present invention can also be applied to a method for producing methyltetrahydropyran from 3-methyl-1,5-pentanediol. That is, by mixing a catalyst and 3-methyl-1,5-pentanediol and heating them, under azeotropic conditions with water, dehydrative cyclization of 3-methyl-1,5-pentanediol to 4-methyltetrahydropyran occurs. Since the produced 4-methyltetrahydropyran forms a two-phase system with the catalyst phase and water, separation from the catalyst and water becomes easy. By continuously supplying the raw material 3-methyl-1,5-pentanediol and continuously extracting the methyltetrahydropyran phase while performing the dehydration reaction, it is also possible to continuously advance the reaction.

[0037] Note that the cyclic ether thus obtained may contain impurities by-produced in the reaction during production. Also, as the cyclic ether, commercially available products can be used, but commercially available cyclic ethers may contain additives such as polymerization inhibitors (e.g., dibutylhydroxytoluene (BHT)). The impurities contained in the cyclic ether are factors that lower the purity of the product, and the polymerization inhibitor may alter the acid catalyst and the target anhydro sugar alcohol, which is not preferable. Therefore, it is preferable to purify the cyclic ether by distillation or the like before use, remove these impurities and additives in advance, and increase the purity to 98% or more, particularly 99% or more, and then use it as a dehydration reaction solvent.

[0038] In the above-mentioned Patent Document 6, it is described that a cyclic ether is used as an organic solvent. In the exemplification of cyclic ethers, there is a description of "substituted (preferably alkyl group-substituted) or unsubstituted tetrahydropyran such as tetrahydropyran (THP)", but specific examples of substituted tetrahydropyran are not given. Also, Patent Document 6 states that "more preferably, it contains one or more selected from 1,2-dimethoxyethane, tetrahydrofuran (THF), tetrahydropyran (THP), 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and cyclopentyl methyl ether, and even more preferably, it contains one or more selected from tetrahydropyran (THP), 3-methyltetrahydrofuran, and 2,5-dimethyltetrahydrofuran, and particularly preferably, it contains tetrahydropyran (THP).". In the examples of Patent Document 6 as well, as cyclic ethers, only tetrahydropyran (boiling point: 88 °C), 2,5-dimethyltetrahydrofuran (boiling point: 92 °C), and 3-methyltetrahydrofuran (boiling point: 89 °C) are used, and there is no suggestion of using a cyclic ether having 6 or more carbon atoms and a boiling point of 93 °C or higher and the effects thereof.

[0039] When an organic solvent is used in the dehydration reaction step prior to the extraction step, there are no particular restrictions on the organic solvent. Specifically, esters such as methyl acetate, lactones such as γ-butyrolactone, and ethers are preferred. Preferably, an ether can be used, and an aliphatic ether is particularly preferred. Examples of aliphatic ethers include chain ethers (dialkoxyalkanes (including aliphatic chain alkyl oxy and alicyclic alkyl oxy) such as 1,2-dimethoxyethane; dialkyl (including aliphatic chain alkyl and alicyclic alkyl) ethers such as diethyl ether, dibutyl ether, ETBE (ethyl tertiary butyl ether), cyclopentyl methyl ether (preferably symmetric or asymmetric dialkyl ethers having two alkyl (including aliphatic chain alkyl and alicyclic alkyl) groups with 1 to 5 carbon atoms)), cyclic ethers (those in which the oxygen atom, which is the functional group of the ether, is part of the ring) (substituted (preferably alkyl group substituted) or unsubstituted tetrahydrofuran such as tetrahydrofuran (THF), 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran; substituted (preferably alkyl group substituted) or unsubstituted tetrahydropyran such as tetrahydropyran (THP), etc.).

[0040] The organic solvent used in the dehydration reaction step and the extraction step preferably does not have an aromatic structure, carbon-carbon double bonds, carbonyl groups, or hydroxyl groups. One of the reasons is that substitution reactions and addition reactions occur under acidic conditions. In that regard, compounds having only aliphatic chain or alicyclic structures (preferably ether compounds) are preferred. If the structure of the organic solvent used is represented by C, H, and O, it contains at least one O (oxygen), preferably H / C is 1.5 or more and 3 or less, more preferably 1.6 or more and 2.5 or less, still more preferably 1.7 or more and 2.3 or less, and particularly preferably 1.8 or more and 2.1 or less. The organic solvent used may contain elements other than carbon, hydrogen, and oxygen, but preferably consists only of carbon, hydrogen, and oxygen.

[0041] In addition, the solubility of the anhydro sugar alcohol in the organic solvent to be used is not particularly limited, but usually a solvent having miscibility above the melting point of the anhydro sugar alcohol is preferred, and an organic solvent having a high solubility at a temperature below the melting point is preferred. Taking isosorbide as an example of the anhydro sugar alcohol, the solubility at 25°C is 1.0 g / 100 mL or more, preferably 1.5 g / 100 mL or more, more preferably 2.0 g / 100 mL or more, still more preferably 2.5 g / 100 mL or more, and particularly preferably 3.0 g / 100 mL or more. These solvents may be used alone or in combination of two or more, and another organic solvent immiscible with water may be used in combination. Further, the organic solvent phase is usually formed only of the organic solvent, but inclusion of components other than the organic solvent to such an extent that the effects of the present invention are not inhibited is not excluded.

[0042] On the other hand, the solubility of the starting sugar alcohol in the organic solvent to be used is not particularly limited, but an organic solvent having a low solubility of the sugar alcohol is preferred. Taking sorbitol as an example of the starting sugar alcohol, the solubility at 25°C is 20 g / 100 mL or less, preferably 10 g / 100 mL or less, more preferably 5.0 g / 100 mL or less, and particularly preferably 3.0 g / 100 mL or less.

[0043] Furthermore, it is preferable that the organic solvent to be used does not dissolve the intermediate in the dehydration reaction. Taking 1,4-sorbitan, which is an intermediate in the dehydration reaction from sorbitol to isosorbide, as an example of the intermediate, the solubility at 25°C is 20 g / 100 mL or less, preferably 10 g / 100 mL or less, more preferably 5.0 g / 100 mL or less, and particularly preferably 3.0 g / 100 mL or less.

[0044] The solubility of the raw materials and products in the above organic solvents can also be defined as the partition coefficient in the water-organic solvent two-phase system. Regarding the organic solvents used in the present invention, in terms of the partition coefficient in 10 mL of water / 10 mL of organic solvent (hereinafter simply referred to as "partition coefficient"), taking 1.0 g of sorbitol as an example of the raw material sugar alcohol, the partition coefficient at 25 °C is usually 6 / 1 or more, preferably 7 / 1 or more, more preferably 8 / 1 or more, still more preferably 9 / 1 or more, and particularly preferably 10 / 1 or more. Taking 1.0 g of isosorbide as an example of the product anhydro sugar alcohol, the partition coefficient at 25 °C is usually 10 / 1 or less, preferably 9 / 1 or less, more preferably 8 / 1 or less, still more preferably 7 / 1 or less, and particularly preferably 6 / 1 or less. By selecting such an organic solvent, the anhydro sugar alcohol produced in the dehydration reaction can be smoothly extracted into the organic solvent to avoid contact with the catalyst and avoid undesirable side reactions. At the same time, the contact efficiency between the raw material and the catalyst can be increased, and a sufficient reaction rate can be obtained, resulting in a dramatic improvement in yield and productivity.

[0045] There is no particular limitation on the boiling point of the organic solvent to be used, but it is preferably 90 °C or higher and 160 °C or lower, more preferably 93 °C or higher and 140 °C or lower, still more preferably 100 °C or higher and 130 °C or lower, and particularly preferably 105 °C or higher and 120 °C or lower. In this method, since the boiling point of the organic solvent and the azeotropic point with water govern the reaction temperature of the dehydration reaction, a higher boiling point enables a higher reaction temperature, leading to an increase in the reaction rate and an improvement in productivity. On the other hand, if the reaction temperature is too high, undesirable reactions such as decomposition of the organic solvent increase.

[0046] There is no particular limitation on the solubility of the organic solvent used in water (at 25°C), but it is preferably 0.01 g / L or more and 5 g / L or less, more preferably 0.02 g / L or more and 4 g / L or less, still more preferably 0.03 g / L or more and 3 g / L or less, and particularly preferably 0.04 g / L or more and 2 g / L or less. If the solubility of the organic solvent used in water is low, when discarding the water separated from the organic solvent / water distilled off in the reaction, the operation of recovering the organic solvent dissolved in the water is reduced, and at the same time, it also has a favorable effect on the extraction of the anhydro sugar alcohol produced in the reactor into the organic solvent and the dehydration reaction rate.

[0047] (Dehydration catalyst) The dehydration catalyst used in the production method of the present embodiment is not particularly limited as long as it can dehydrate sugar alcohol, but it is usually an inorganic protonic acid, which does not dissolve in the organic solvent and forms a two-phase (layer) and has strong acidic properties. The type thereof is not particularly limited, but it preferably contains one or more selected from sulfuric acid, sulfonic acid, phosphoric acid, fluorosulfuric acid, isopolyacid, heteropolyacid, acidic ion exchange resin, and polyvalent cation ion exchange montmorillonite clay catalyst, more preferably contains one or more selected from sulfuric acid, acidic ion exchange resin, isopolyacid, and heteropolyacid, and particularly preferably contains heteropolyacid.

[0048] As the type of heteropolyacid, the Dawson type and the Keggin type are preferred, and the Keggin type is particularly preferred. Among the heteropolyacids having a Keggin type structure, silicotungstic acid, phosphotungstic acid, and phosphomolybdic acid are preferred, and these may be partially deficient or substituted.

[0049] In order to advance the dehydration reaction, the raw material sugar alcohol and its intermediate must be able to access the active site of the dehydration catalyst. Therefore, as a more effective catalyst form, a non-solid acid catalyst that dissolves in the raw material sugar alcohol and can act molecularly is preferred. These acid catalysts are preferably subjected to treatments such as heating and dehydration under an inert gas stream in advance as a pretreatment and partially neutralizing to adjust the acidity before use in the dehydration reaction.

[0050] Also, as an effective acid catalyst, it is preferable that the proton density (the number of moles of protons per unit volume of a solid or liquid at normal pressure and room temperature) is higher. When the acid catalyst forms two phases with an organic solvent as the catalyst phase, the more compact the catalyst phase is, the more efficiently the contact with the raw material sugar alcohol and the transfer of the product to the organic solvent proceed, and as a result, the reaction can be carried out efficiently. The preferable proton density (normal pressure, room temperature) is usually 1 mmol / cm 3 or more, preferably 5 mmol / cm 3 or more, more preferably 10 mol / cm 3 or more, particularly preferably 20 mmol / cm 3 or more.

[0051] When subjecting the dehydration catalyst to a dehydration reaction, the dehydration catalyst may be filled in the reactor in advance and the raw material and the organic solvent may be introduced later, or the dehydration catalyst may be mixed with the raw material and the organic solvent and then introduced into the reactor. The amount of the dehydration catalyst is not particularly limited, but is preferably 1% by mass or more and 500% by mass or less, more preferably 2% by mass or more and 200% by mass or less, still more preferably 5% by mass or more and 100% by mass or less based on the total mass of the raw material sugar alcohol and the monoanhydro sugar alcohol.

[0052] (Mode of dehydration reaction) In the production method of the present embodiment, the dehydration reaction in the dehydration reaction step is preferably carried out under heating conditions. For example, the dehydration reaction may be carried out in a reactor filled with a dehydration catalyst and an organic solvent and heated. The form of the reaction may be batch type or continuous type. For example, the dehydration reaction of sorbitol may be carried out at a reaction temperature of 100 °C with 5 mmol of a heteropolyacid as a dehydration catalyst with respect to 0.1 mol of sorbitol.

[0053] The reaction temperature of the dehydration reaction in the dehydration reaction step of the production method according to this embodiment is preferably equal to or higher than the azeotropic point of the cyclic ether, which is an organic solvent, and water, preferably 90°C or higher and 160°C or lower, more preferably 93°C or higher and 140°C or lower, still more preferably 100°C or higher and 130°C or lower, and particularly preferably 105°C or higher and 120°C or lower. By setting the reaction temperature below the above upper limit, polymerization due to intermolecular reactions of the raw materials, intermediates, and products can be suppressed. By setting the reaction temperature above the above lower limit, it is possible to suppress the increase in side reactions involving intermediates such as monomolecular dehydrates to an unacceptable level and obtain a sufficient dehydration reaction rate.

[0054] When the reaction temperature is higher than the boiling point of the organic solvent used, the solvent evaporates and needs to be replenished. In that case, methods such as separately supplying a new solvent or refluxing the evaporated solvent back to the reactor are preferably used. On the other hand, for the purpose of suppressing the evaporation of the organic solvent and saving energy, it is also preferably carried out to set the reaction temperature below the boiling point of the cyclic ether, which is an organic solvent. In the case of an organic solvent that forms an azeotrope with water, the amount of water soluble in the organic solvent continuously changes from the azeotropic composition of the azeotrope to 0% of the boiling point of the organic solvent, and the amount of water soluble affects the extraction performance of the organic solvent and the acid strength of the acid catalyst. Therefore, the extraction performance of the organic solvent for the product and intermediate and the performance of the acid catalyst can be controlled by the reaction temperature.

[0055] When a substance that forms an azeotrope with water is used as the organic solvent, the reaction temperature depends on the azeotropic temperature. Furthermore, instead of directly refluxing the azeotroped solvent to the reactor, it may be separately cooled and collected, the water may be removed from the organic solvent by changing the distillation conditions, or it may be returned to the reactor after removing the water with a dehydrating agent or the like. Furthermore, when an organic solvent that is immiscible with water is used, the separately collected azeotrope may be allowed to stand and separated into two phases (layers), and only the organic solvent phase may be returned to the reactor or reused.

[0056] The reaction pressure of the dehydration reaction is not particularly limited, but is preferably 0.08 MPa or more and 1 MPa or less in absolute pressure, more preferably 0.09 MPa or more and 0.5 MPa or less, and even more preferably 0.1 MPa or more and 0.2 MPa or less. It is also preferably carried out to adjust the azeotropic temperature (reaction temperature) by adjusting the pressure. As the atmosphere gas in the reactor, for example, inert substances such as helium, nitrogen, argon, and carbon dioxide that do not have an adverse effect on the dehydration reaction can be used.

[0057] The supply method of the sugar alcohol (including monoanhydro sugar alcohol) used as the raw material is not particularly limited, but methods such as melting and supplying as a liquid or supplying as an aqueous solution can be used. When supplying the raw material as an aqueous solution, if the amount of water is too large, the efficiency of the dehydration reaction may decrease. In that case, a method of preliminarily heating the aqueous solution before introducing it into the dehydration reactor to distill and separate a predetermined proportion of water and concentrating the sugar alcohol used as the raw material is also preferably used.

[0058] In the production method according to this embodiment, since the organic solvent phase and the catalyst phase form two phases (layers) in the reactor, after the completion of the dehydration reaction, by collecting only the organic solvent phase without going through a special catalyst separation operation, the product dissolved in the organic solvent phase can be obtained. In that case, it is preferable to lower the temperature of the reactor to such an extent that the product does not precipitate. When the organic solvent phase and the catalyst phase are difficult to separate, a method of separately providing a separation tank, transferring the reaction mixture thereto, and separating the organic solvent phase and the catalyst phase is also preferably used.

[0059] In the production method according to this embodiment, since the intermediate is more likely to be distributed in the organic solvent phase than the raw material, and the product is more likely to be distributed in the organic solvent phase than the intermediate, high-purity anhydro sugar alcohol can be easily obtained by collecting the organic solvent phase. For example, taking the production of isosorbide by dehydration of sorbitol as an example, the molar ratio of the intermediate (1,4-sorbitan) to the raw material and the product (isosorbide) in the organic solvent phase collected after the reaction is preferably 1 or more, more preferably 2 or more, still more preferably 4 or more, and particularly preferably 8 or more. Also, the molar ratio of the product (isosorbide) to the intermediate (1,4-sorbitan) in the organic solvent phase collected after the reaction is preferably 1 or more, more preferably 2 or more, still more preferably 4 or more, and particularly preferably 8 or more.

[0060] In addition, in the production method according to this embodiment, since the highly hydrophilic impurities and by-products derived from the raw material remain in the catalyst phase, by collecting only the organic solvent phase, the product can be obtained in a form with impurities removed as a result. Furthermore, by bringing the obtained organic solvent phase into contact with another solvent that is immiscible with the organic solvent phase or by washing the obtained organic solvent phase with another solvent that is immiscible with the organic solvent phase, it is possible to remove or recover impurities, by-products, or intermediates from the obtained organic solvent phase. That is, it is possible to increase the content and purity of isosorbide in the organic solvent phase obtained by this method. Examples of the solvent that is immiscible with the organic solvent phase include various alcohols, water, and sorbitol, and water and sorbitol are preferably used suitably. At that time, the amount of the solvent used for contact and washing is not particularly limited, but if it is too much, a large amount of isosorbide will migrate together with impurities, by-products, or intermediates, resulting in poor efficiency. When contact and washing are performed using water or sorbitol as the solvent, the catalyst that slightly mixes into the organic solvent phase can be removed without treatment such as neutralization.

[0061] In addition, by adopting an overflow method, a suction method, etc., the reaction can be continuously continued while continuously removing the organic solvent phase. In that case, by continuously supplying the raw material to the reactor, it is also possible to continuously continue the reaction over a long period of time.

[0062] In the production method according to this embodiment, the catalyst phase after the reaction (in the case of a solid catalyst, the catalyst surface or the inside of the particles) may contain the product. In that case, the product can be recovered by adding an organic solvent to the catalyst phase and performing an extraction operation (extraction step). At that time, the extraction operation may be performed after neutralizing the catalyst with a base or the like or treating it. The organic solvent used for extraction is preferably one that does not dissolve the catalyst, dissolves the anhydro sugar alcohol that is the target product, and does not dissolve the sugar alcohol that is the raw material. Further, it preferably has stability under acidic conditions and does not cause reactions such as self-decomposition or polymerization. Those having the property of azeotroping with water are more preferable, and those having the property of separating into two phases (layers) with water are particularly preferable.

[0063] In addition, in the dehydration reaction of sugar alcohol for the production of anhydro sugar alcohol, without using an organic solvent, by adding an organic solvent after the reaction is completed, at least one of the sugar alcohol that is the raw material, water, catalyst, by-products, impurities, reaction intermediates and the anhydro sugar alcohol that is the product can be extracted from the mixture (reactants) containing the anhydro sugar alcohol by the organic solvent (extraction step). Also in that case, similar to the above description, the extraction operation may be performed after neutralizing the catalyst with a base or the like or performing a removal treatment such as filtration.

[0064] In the extraction step after the dehydration reaction step using an organic solvent and also in the extraction step after the dehydration reaction step performed without using an organic solvent, as the organic solvent to be used, those exemplified as the organic solvent used in the above-described dehydration reaction step are preferably used.

[0065] In addition, the organic solvent used in this extraction step is not particularly limited, and examples include those exemplified as the organic solvent used in the above-described dehydration reaction step. The organic solvent used in the dehydration reaction step does not have to be the same as the organic solvent used in the extraction step, and they may be different. However, in terms of solvent preparation, management, handling, etc., it is preferable to use the same cyclic ether.

[0066] In the extraction step, the organic solvent used for extraction also varies depending on the anhydro sugar alcohol content in the catalyst phase and the type of organic solvent used, but it is preferably about 0.5 to 5 volume times that of the catalyst phase. The extraction step may be repeated multiple times.

[0067] In the production method according to this embodiment, preferably, the catalyst is separated and recovered after extracting the catalyst phase from the reactor. Examples of the method for separating and recovering the catalyst include filtration, crystallization, and extraction. During these operations, water, a solvent, an acid, or an alkali may be added to improve operability. Also, in order to continuously continue the reaction, a method of extracting a part of the catalyst from the catalyst phase and replenishing it with a new catalyst is preferably used.

[0068] The separated and recovered catalyst can be reused in the dehydration reaction again after undergoing regeneration such as purification. At that time, the products and polymers attached to the catalyst can be removed or separated and recovered by treatment such as washing with water or an organic solvent. Also, when an acid or an alkali is used in the separation and recovery of the catalyst, it is preferable to remove those acids and alkalis before reusing them in the dehydration reaction.

[0069] Furthermore, a method of regenerating the catalyst by removing polymers and the like attached to the catalyst by drying, firing treatment, etc. is also preferably used. In this case, the firing treatment of the catalyst is preferably carried out at a temperature such that the structure of the catalyst does not collapse due to heat. The firing temperature during catalyst regeneration is preferably 250°C or higher and 600°C or lower, more preferably 300°C or higher and 550°C or lower, and even more preferably 350°C or higher and 500°C or lower.

[0070] (Purification and Uses of the Generated Anhydro Sugar Alcohol) In the production method according to the present embodiment, the target product, anhydro sugar alcohol (monoanhydro sugar alcohol and / or dianhydro sugar alcohol), is separated from the catalyst in a form dissolved in an organic solvent after the dehydration reaction. The proportion of the target product in the substances dissolved in the organic solvent at that time is usually 70% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and particularly preferably 97% by mass or more. In this embodiment, since a relatively high-purity anhydro sugar alcohol can be obtained, the anhydro sugar alcohol can be precipitated from the organic solvent as it is to obtain the anhydro sugar alcohol and used for a desired application, but the organic solvent phase may be further purified if necessary. The purification method is not particularly limited, but activated carbon treatment, ion exchange resin treatment, crystallization, distillation, etc. are preferably used. Among these, a plurality of purification methods may be combined and carried out. It may be.

[0071] Also, it is also preferable to purify anhydro sugar alcohols by distillation under reduced pressure. Taking isosorbide as an example, the distillation operation under reduced pressure is exemplified. After collecting the organic solvent from the organic solvent phase after the dehydration reaction and removing the organic solvent with an evaporator or the like, it is possible to distill at 149 to 156 °C under a reduced pressure of 2 to 4 torr using a distillation apparatus equipped with a Claisen head. The obtained isosorbide usually has a purity of 98% or more as the area ratio of gas chromatography and a white color tone. The amount of 1,4-sorbitan is usually 2% by mass or less.

[0072] The obtained anhydro sugar alcohol itself can be used as a raw material or additive for various chemicals, pharmaceuticals, and surfactants, and can also be used as a raw material for various polymers such as polycarbonate.

[0073] In addition, in the production method according to the present embodiment, the yield of the product anhydro sugar alcohol is preferably 30 mol% or more, more preferably 40 mol% or more, still more preferably 50 mol% or more, and particularly preferably 60 mol% or more.

[0074] In addition, in the manufacturing method according to the present embodiment, high-purity anhydro sugar alcohol is obtained. The solid content of the anhydro sugar alcohol obtained by precipitation, distillation, or the like is a white solid, and the YI value measured with a color difference meter is preferably 3.0 or less, more preferably 2.0 or less, and particularly preferably 1.0 or less. Furthermore, the solid content of the anhydro sugar alcohol preferably has an APHA value of 50 or less, more preferably 30 or less, and particularly preferably 20 or less when measured with a color difference meter in the same manner.

[0075] In the manufacturing method according to the present embodiment described above, in the presence of a specific organic solvent and a catalyst, the organic solvent phase and the catalyst phase coexist, and a dehydration reaction step of performing a dehydration reaction of sugar alcohol while removing water by a reactive distillation method if desired is included, and at least one of monoanhydro sugar alcohol and dianhydro sugar alcohol is produced. Alternatively, under the above conditions, dianhydro sugar alcohol is produced by performing a dehydration reaction of monoanhydro sugar alcohol. Thereby, the rate of the dehydration reaction can be improved, and the product can be produced with high selectivity. Therefore, the yield of anhydro sugar alcohol can be increased.

[0076] In addition, the concentration of intermediates and products and the contact with the catalyst are prevented, and side reactions such as polymerization, carbonization, and decomposition due to intermolecular condensation thereof can also be suppressed. Therefore, the purification step of the obtained anhydro sugar alcohol can be simplified. Further, the purity of the anhydro sugar alcohol after purification is also high, and it is excellent as a raw material for various chemicals and polymers. Furthermore, the catalyst used for dehydration can be easily separated, and a continuous reaction over a long time can be carried out by continuously supplying raw materials and separating products.

[0077] Therefore, according to the manufacturing method of the present embodiment, it is possible to reduce changes in reaction temperature and pressure, as well as changes in the concentration and residence time of raw materials, intermediates, products, and by-products, which are caused by an increase in the production scale of anhydro sugar alcohol and changes in various factors during the production process. As a result, the target anhydro sugar alcohol can be efficiently produced. Therefore, the manufacturing method according to the present embodiment is an industrially advantageous method.

Examples

[0078] Hereinafter, the method for producing isosorbide by the dehydration reaction of sorbitol will be described as an example to more specifically explain the present invention. However, the present invention is not limited to these examples in any way.

[0079] (Example 1) Using 4-methyltetrahydropyran (boiling point: 105 °C) as the organic solvent and 26-hydrate of keitungstannic acid (proton density: about 2.5 mmol / cm 3 ) as the dehydration catalyst, isosorbide was produced by the dehydration reaction of sorbitol. The azeotropic point of 4-methyltetrahydropyran and water is 85 °C. As 4-methyltetrahydropyran, 4-methyltetrahydropyran (Tokyo Chemical Industry reagent) was previously distilled and purified to remove BHT, which is a polymerization inhibitor, and then used.

[0080] The specific procedure is as follows.

[0081] A jacketed 300 mL four-necked flask equipped with a reflux condenser, a Dean-Stark type water content measuring receiver, and a Teflon-coated thermocouple was charged with 120 mmol of D-sorbitol (Kishida Chemical reagent, special grade), 12 mmol of 26-hydrate of keitungstannic acid (Kishida Chemical reagent, special grade), and 150 mL of 4-methyltetrahydropyran. The reactor was heated using silicone oil circulated from a circulating thermostat, and the contents were stirred by rotating a Teflon stirring blade with a three-one motor. While stirring, a dehydration reaction was carried out under normal pressure and in a nitrogen atmosphere. The time when the temperature in the reactor rose and the organic solvent began to evaporate violently and reflux was taken as the reaction start time. At the start point, it was confirmed that the mixture separated into two phases: 4-methyltetrahydropyran and a mixed layer of the catalyst and sorbitol. The water (produced by the dehydration reaction of the raw material) that evaporated together with the organic solvent during the dehydration reaction was collected in a moisture determination receiver. The rate was about 4 mL / h. The reaction was stopped 1 hour after the start of the reaction, and the reactor was immediately cooled. In the above operation, the temperature in the reactor (reaction temperature) at the start of the reaction was 102 °C, but as the dehydration reaction progressed, the temperature in the reactor (reaction temperature) gradually increased and was 107 °C immediately before the reaction stopped. It was also confirmed that during the reaction and at the time of reaction stop, the inside of the reactor was a two-phase system of an organic solvent phase and a catalyst phase.

[0082] After cooling the reactor to room temperature, all 125 mL of the organic solvent phase in the reactor was collected with a pipette. Further, 100 mL of the organic solvent was added to the remaining catalyst phase, and the mixture was stirred at 85 °C (oil bath temperature) for 1 hour to extract isosorbide and the like contained in the catalyst phase, and it was recovered together with the organic solvent. Using a part of the recovered organic solvent, phenyl ether (Tokyo Chemical Industry reagent 99%) was added as an internal standard substance, and N-trimethylsilylimidazole (Tokyo Chemical Industry reagent) was added in the presence of pyridine, and the mixture was heated at 70 °C for 20 minutes or more to prepare an analytical sample. The products and the like were analyzed with a gas chromatograph equipped with a capillary column DB-1 (Agilent Technologies 0.25 μm, 0.250 mm Φ × 60 m).

[0083] As a result, it was confirmed that isosorbide was obtained in a yield of 71 mol% in total, 55 mol% from the organic solvent phase after the dehydration reaction and 16 mol% from the portion extracted from the catalyst phase using the organic solvent, based on the charged amount of sorbitol. Also, the mole fraction of isosorbide in the organic solvent phase was about 95%.

[0084] (Example 2) As the dehydrating solvent, instead of 12 mmol of potassium tungstate 26-hydrate, 24 mmol of sulfuric acid (manufactured by Junsei Chemical, 95% pure) with a proton density of about 35 mmol / cm 3 was used, and the dehydration reaction of sorbitol was initiated in the same manner as in Example 1. At the start point, it was confirmed that it was separated into two phases of a mixed layer of 4-methyltetrahydropyran, the catalyst, and sorbitol. The water (produced in the dehydration reaction of the raw material) evaporated together with the organic solvent during the dehydration reaction formed a two-layer with the organic solvent and was collected in the water quantifier. The rate was about 2.4 mL / h. The reaction was stopped when 2.5 hours had elapsed since the start of the reaction, and the reactor was immediately cooled. The temperature inside the reactor (reaction temperature) at the start of the reaction was 104°C, and as the dehydration reaction proceeded, the temperature inside the reactor (reaction temperature) gradually increased and was 106°C immediately before the reaction was stopped. In addition, it was confirmed that a two-phase system of the organic solvent phase and the catalyst phase was established inside the reactor even during the reaction and at the time of reaction stop.

[0085] Recovery of the organic solvent phase, extraction, recovery of isosorbide, etc. from the catalyst phase using the same organic solvent as used in the reaction, preparation of the analysis sample, and analysis of the product, etc. were carried out in the same manner as in Example 1. As a result, it was confirmed that 59 mol% was obtained from the organic solvent phase after the dehydration reaction and 14 mol% was obtained from the portion extracted from the catalyst phase using the organic solvent, for a total of 73 mol% of isosorbide based on the charged amount of sorbitol. Also, the molar fraction of isosorbide in the organic solvent phase was about 93%.

[0086] (Comparative Example 1) As the organic solvent, the dehydration reaction of sorbitol was carried out in the same manner as in Example 1, using tetrahydropyran (boiling point: 88°C, reagent from Tokyo Chemical Industry, nominal purity > 98%) as it was instead of 4-methyltetrahydropyran. The azeotropic point of tetrahydropyran and water is 75°C. At the start point of the reaction, it was confirmed that it was separated into two phases of a mixed layer of methyltetrahydropyran, the catalyst, and sorbitol. Water (produced in the dehydration reaction of the raw material) that evaporated together with the organic solvent during the dehydration reaction formed a two-layer with the organic solvent and was collected in the water quantifier. The rate was about 1 mL / h. The reaction was stopped when 6 hours had elapsed since the start of the reaction, and the reactor was immediately cooled. The temperature inside the reactor (reaction temperature) at the start of the reaction was 85°C, and as the dehydration reaction proceeded, the temperature inside the reactor (reaction temperature) gradually increased and was 89°C immediately before the reaction stopped. In addition, it was confirmed that a two-phase system of an organic solvent phase and a catalyst phase was established inside the reactor during the reaction and at the time of reaction stop.

[0087] Recovery of the organic solvent phase, extraction, recovery of isosorbide, etc. from the catalyst phase using the same organic solvent as used in the reaction, preparation of the analysis sample, and analysis of the product, etc. were carried out in the same manner as in Example 1. As a result, it was confirmed that 46 mol% of isosorbide was obtained, 31 mol% from the organic solvent phase after the dehydration reaction and 15 mol% from the portion extracted from the catalyst phase using the organic solvent, based on the charged amount of sorbitol. Also, the molar fraction of isosorbide in the organic solvent phase was about 85%.

[0088] From the results of Example 1, Example 2, and Comparative Example 1, by the method of the present invention, when a cyclic ether having 6 or more carbon atoms and a boiling point of 93°C or higher is used as the organic solvent for the dehydration reaction at a temperature of 93°C or higher, and further the extraction after the reaction is carried out using a cyclic ether having 6 or more carbon atoms and a boiling point of 93°C or higher as the organic solvent, it can be seen that the progress of the reaction becomes faster, the separation of the catalyst and the product after the reaction end, and the selective extraction of the product become easy, and anhydro sugar alcohol can be efficiently produced.

Claims

**Claim 1** A step of performing a dehydration reaction of a sugar alcohol in a two-phase system formed from an organic solvent phase containing an organic solvent and a catalyst phase containing a catalyst, and / or from a reaction mixture containing a catalyst obtained by the dehydration reaction of the sugar alcohol, extracting a monoanhydro sugar alcohol and / or a dianhydro sugar alcohol (hereinafter referred to as "anhydro sugar alcohol") using an organic solvent, the method for producing an anhydydro sugar alcohol comprising: The method for producing an anhydydro sugar alcohol, characterized in that a cyclic ether having 6 or more carbon atoms and a boiling point of 100°C or higher is used as the organic solvent. **Claim 2** The method for producing an anhydydro sugar alcohol according to Claim 1, wherein the reaction temperature in the dehydration reaction step is 90°C or higher and 160°C or lower. **Claim 3** The method for producing an anhydydro sugar alcohol according to Claim 1 or 2, wherein the cyclic ether has 12 or fewer carbon atoms and a boiling point of 160°C or lower. **Claim 4** The method for producing an anhydydro sugar alcohol according to any one of Claims 1 to 3, wherein the cyclic ether is a 5-membered or 6-membered cyclic ether. **Claim 5** The method for producing an anhydydro sugar alcohol according to any one of Claims 1 to 4, wherein the cyclic ether is methyltetrahydropyran. **Claim 6** The method for producing an anhydydro sugar alcohol according to any one of Claims 1 to 5, wherein the catalyst contains a heteropolyacid.