Adipic Acid Manufacturing Method

Abstract

The present invention is characterized by comprising a step (hydrogenation step) for reacting 3-hydroxyadipic acid-3, 6-lactone with hydrogen in an aqueous solvent in the presence of a hydrogenation catalyst, and is able to produce adipic acid under industrially advantageous conditions (with a high yield, highly soluble starting materials and a single step without use of a toxic reagent) without discharging dinitrogen monoxide.

Description

[Technical field]

[0001] The present invention relates to a method for producing adipic acid using a substance derived from a biomass resource as a raw material. [Background technology]

[0002] Adipic acid is a raw material for polyamide 6,6. Adipic acid can be industrially produced by nitric acid oxidation of a mixture of cyclohexanone and cyclohexanol (KA oil). However, since a large amount of dinitrogen monoxide gas, which has a high greenhouse effect, is produced as a by-product, a method for producing adipic acid using biomass, which is a renewable resource, or a substance that can be derived from a biomass resource as a raw material has been proposed. Such methods include a method for fermentatively producing adipic acid using sugar or fatty acid as a raw material (Non-Patent Document 1), a method for producing adipic acid by chemically hydrogenating muconic acid produced from sugar through fermentation (Patent Document 1), a method for chemically synthesizing adipic acid from homocitric acid produced from sugar through fermentation via 3-oxoadipic acid and 3-hydroxyadipic acid (Patent Document 2), and a method for chemically synthesizing adipic acid from sugar (Patent Document 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 9-505463 [Patent Document 2] International Publication No. 2014 / 043182 [Patent Document 3] U.S. Patent No. 8,669,393 [Non-patent literature]

[0004] [Non-Patent Document 1] Biochemical Engineering Journal, vol.105, p.16-26(2016). Summary of the Invention [Problem to be solved by the invention]

[0005] The method for producing adipic acid using biomass, which is a renewable resource, or a substance that can be derived from a biomass resource as a raw material is an environmentally friendly method that solves the problem of the conventional method of by-producing nitrous oxide gas, but there are various technical problems from an industrial point of view. Specifically, the method for producing adipic acid by fermentation using sugar or fatty acid as a raw material has a low yield of adipic acid. The method for producing adipic acid by chemically hydrogenating muconic acid produced by fermentation from sugar has low solubility in a solvent, making it difficult to charge the reaction at a high concentration. The method for chemically synthesizing adipic acid from homocitric acid produced by fermentation from sugar has a low fermentation yield of homocitric acid and requires multiple chemical reactions from homocitric acid to adipic acid. In addition, the method for chemically synthesizing adipic acid from sugar requires the use of an equivalent amount of hydrogen bromide to the sugar, but hydrogen bromide is a toxic chemical. Thus, the conventional methods include industrially disadvantageous factors such as poor environmental friendliness, low yield, low solubility, multiple steps, and the use of large amounts of toxic chemicals. [Means for solving the problem]

[0006] As a result of intensive research by the present inventors to solve the above problems, they discovered that adipic acid can be produced under industrially advantageous conditions (high yield, using highly soluble raw materials, in a single process, without using toxic reagents) without emitting nitrous oxide by reacting 3-hydroxyadipic acid-3,6-lactone, a substance that can be derived from biomass resources, with hydrogen in an aqueous solvent in the presence of a hydrogenation catalyst, and thus completed the present invention.

[0007] That is, the present invention comprises the following (1) to (8). (1) A method for producing adipic acid, comprising a step of reacting 3-hydroxyadipic acid-3,6-lactone with hydrogen in an aqueous solvent in the presence of a hydrogenation catalyst (hydrogenation step). (2) The method according to (1), wherein the hydrogenation catalyst contains one or more transition metal elements selected from the group consisting of palladium, platinum, ruthenium, rhodium, rhenium, nickel, cobalt, iron, iridium, osmium, copper and chromium. (3) The method according to (1) or (2), wherein the hydrogenation catalyst is supported on a carrier. (4) The method according to (3), wherein the support has acid catalytic activity. (5) The method according to any one of (1) to (4), wherein the reaction temperature in the hydrogenation step is 100 to 350° C. (6) The method according to any one of (1) to (5), wherein the hydrogenation step is carried out in the absence of ammonia. (7) The method according to any one of (1) to (6), wherein the 3-hydroxyadipic acid fermentation liquor is adjusted to a pH of less than 7 by adding an acid, and the filtrate obtained by passing the liquor through a nanofiltration membrane is subjected to the hydrogenation step. (8) An aqueous solution of adipic acid, in which the content of n-valeric acid per 100 parts by weight of adipic acid is 0.01 to 20 parts by weight. Effect of the Invention

[0008] According to the present invention, adipic acid can be produced under industrially advantageous conditions (high yield, using highly soluble raw materials, in a single process, and without using toxic reagents) without emitting nitrous oxide. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The present invention will now be described in more detail.

[0010] [3-Hydroxyadipic acid-3,6-lactone] 3-Hydroxyadipic acid-3,6-lactone is an organic compound represented by the following chemical formula (1), and can be chemically synthesized, for example, by the reaction shown in Reference Example 1 of the Examples described later.

[0011] [ka]

[0012] In addition, 3-hydroxyadipic acid-3,6-lactone can be produced from 3-oxoadipic acid, which can be derived from biomass resources. In this case, for example, as shown in Scheme 1 below, 3-hydroxyadipic acid-3,6-lactone can be synthesized by hydrogenating and condensing 3-oxoadipic acid.

[0013] [ka]

[0014] 3-Oxoadipic acid is a compound that is biosynthesized in the metabolic process of aromatic compounds such as protocatechuic acid and catechol. As a method for producing 3-oxoadipic acid using this pathway, for example, JP 2012-59 A discloses a method for fermentatively producing 3-oxoadipic acid from protocatechuic acid using recombinant Pseudomonas putida. Here, protocatechuic acid and catechol are substances derived from biomass resources that can be produced by microbial fermentation using sugar as a carbon source. For example, a method for fermentatively producing protocatechuic acid and catechol using glucose as a carbon source is disclosed in the specification of US Pat. No. 5,272,073. Therefore, 3-hydroxyadipic acid-3,6-lactone can be said to be a substance that can be derived from biomass resources.

[0015] 3-Hydroxyadipic acid-3,6-lactone may be a carboxylic acid, a carboxylate, or a carboxylate ester, or a mixture thereof may also be used as the starting material of the present invention, and these are collectively referred to as "3-hydroxyadipic acid-3,6-lactone" in this specification.

[0016] Examples of the carboxylate of 3-hydroxyadipic acid-3,6-lactone include 3-hydroxyadipic acid-3,6-lactone ammonium salt, 3-hydroxyadipic acid-3,6-lactone lithium salt, 3-hydroxyadipic acid-3,6-lactone sodium salt, and 3-hydroxyadipic acid-3,6-lactone potassium salt.

[0017] Examples of carboxylates of 3-hydroxyadipic acid-3,6-lactone include 3-hydroxyadipic acid-3,6-lactone methyl ester, 3-hydroxyadipic acid-3,6-lactone ethyl ester, 3-hydroxyadipic acid-3,6-lactone propyl ester, 3-hydroxyadipic acid-3,6-lactone isopropyl ester, 3-hydroxyadipic acid-3,6-lactone butyl ester, and 3-hydroxyadipic acid-3,6-lactone isobutyl ester.

[0018] [Water-based solvent] In the present invention, adipic acid is produced from 3-hydroxyadipic acid-3,6-lactone in an aqueous solvent. In the present invention, the aqueous solvent means water or a mixed solvent mainly made of water and a water-miscible organic solvent. "Mainly made of water" means that the proportion of water in the mixed solvent is more than 50% by volume, preferably 70% by volume or more, and more preferably 90% by volume or more.

[0019] Examples of water-miscible organic solvents that can be used in the present invention include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol, 1,2-dimethoxyethane, diglyme, tetrahydrofuran, dioxane, γ-butyrolactone, N-methylpyrrolidone, dimethylsulfoxide, dimethylformamide, dimethylacetamide, and acetone.

[0020] The pH of the aqueous solvent is not particularly limited, but in consideration of the prevention of catalyst deterioration, the prevention of by-product formation, corrosiveness to a reaction apparatus, etc., the pH is preferably from 2 to 13, more preferably from 3 to 11, and even more preferably from 4 to 10.

[0021] [Hydrogenation catalyst] In the present invention, a hydrogenation catalyst is used to produce adipic acid from 3-hydroxyadipic acid-3,6-lactone.

[0022] The hydrogenation catalyst refers to a metal and / or metal complex having hydrogenation ability. Here, having hydrogenation ability means having the ability to add hydrogen atoms to unsaturated bonds such as carbon-carbon double bonds (C=C), carbon-carbon triple bonds (C≡C), carbon-oxygen double bonds (C=O), carbon-nitrogen double bonds (C=N), and carbon-nitrogen triple bonds (C≡N) in the presence of hydrogen.

[0023] The hydrogenation catalyst preferably contains a transition metal element, specifically, it preferably contains one or more elements selected from the group consisting of palladium, platinum, ruthenium, rhodium, rhenium, nickel, cobalt, iron, iridium, osmium, copper and chromium, and more preferably contains one or more elements selected from the group consisting of palladium, platinum, nickel, cobalt, iron, copper and chromium.

[0024] The state in which the hydrogenation catalyst is present is not particularly limited, and it may be in any of the following states: cluster state, nanoparticle state, microparticle state, bulk state, a state dispersed in a solution like a colloid, and a state uniformly dissolved in a solvent.

[0025] The hydrogenation catalyst is preferably used supported on a carrier from the viewpoints of saving the amount of metal used, increasing the active surface of the catalyst, etc. The supported amount is usually 0.1 to 20% by weight in elemental terms relative to the carrier.

[0026] The hydrogenation catalyst can be supported on a carrier by a known method such as an impregnation method, a deposition / precipitation method, or a gas phase supporting method.

[0027] Examples of the support for the hydrogenation catalyst include carbon, polymers, metal oxides, metal sulfides, zeolites, clays, heteropolyacids, solid phosphoric acid, and hydroxyapatite. A support having acid catalytic activity is preferred because it can further increase the selectivity for adipic acid.

[0028] Examples of polymers having acid catalytic activity include acidic ion exchange resins. Specifically, styrene-based sulfonic acid type ion exchange resins and phenol-based sulfonic acid type ion exchange resins can be used. For example, Mitsubishi Chemical's "DIAION," LANXESS's "Lewatit," Rohm and Haas's "Amberlite" and "Amberlyst," and Dow's "DOWEX" can be mentioned.

[0029] Examples of metal oxides having acid catalytic activity include oxides containing one or more metal elements selected from the group consisting of Sc, Y, Ce, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Zn, Cd, Al, Ga, In, Si, Ge, Sn, and Pb. More specifically, examples of the oxide include scandium oxide (Sc2O3), cerium oxide (CeO2), anatase type titanium oxide (A-TiO2), rutile type titanium oxide (R-TiO2), zirconium oxide (ZrO2), vanadium oxide (V2O5), niobium oxide (Nb2O5), tantalum oxide (Ta2O5), chromium oxide (Cr2O3), molybdenum oxide (MoO3), tungsten oxide (WO3), manganese oxide (MnO2), iron oxide (Fe2O3, Fe3O4), zinc oxide (ZnO), aluminum oxide (Al2O3), gallium oxide (Ga2O3), indium oxide (In2O3), silicon dioxide (SiO2), germanium oxide (GeO2), tin oxide (SnO2), lead oxide (PbO), and silica-alumina (SiO2-Al2O3).

[0030] Zeolites having acid catalytic activity can be those given a three-letter alphabetical structure code in the database of the International Zeolite Association.Specific examples of such zeolites include those given structure codes such as LTA, FER, MWW, MFI, MOR, LTL, FAU, BEA, CHA, and CON.

[0031] Examples of clays having acid catalytic activity include kaolin, montmorillonite, bentonite, saponite, and acid clay.

[0032] [Hydrogenation process] In the hydrogenation step of 3-hydroxyadipic acid-3,6-lactone, hydrogen may be added to the reactor all at once or successively. The partial pressure of hydrogen is not particularly limited, but if it is too low, the reaction time will be long, while if it is too high, it is undesirable from the viewpoint of equipment safety. Therefore, at the start of the reaction, the partial pressure is preferably 0.1 MPa or more and 10 MPa or less (gauge pressure) at room temperature, more preferably 0.5 MPa or more and 3 MPa or less (gauge pressure).

[0033] The reaction can be carried out using any of the following reactors: a batch reactor, a semi-batch reactor, a continuous reactor, and a continuous tubular reactor. When the reaction is carried out using a solid catalyst carrying a metal / metal complex having hydrogenation ability, the reaction can be carried out using any of the following systems: a suspension bed system, a fixed bed system, a moving bed system, and a fluidized bed system.

[0034] If the reaction temperature is too low, the reaction rate will be slow, and if the reaction temperature is too high, the energy consumption will be high, which is undesirable. From this viewpoint, the reaction temperature is preferably 100 to 350°C, more preferably 120 to 300°C, even more preferably 130 to 280°C, even more preferably 140 to 250°C, even more preferably 150 to 230°C, and even more preferably 160 to 220°C.

[0035] In addition to hydrogen, the atmosphere in the reactor may contain inert gases such as nitrogen, helium, and argon, but the oxygen concentration is preferably 5% by volume or less because this leads to deterioration of the hydrogenation catalyst and the generation of explosive gas. In addition, from the viewpoint of the stability of 3-hydroxyadipic acid-3,6-lactone and adipic acid, the amount of ammonia relative to the 3-hydroxyadipic acid-3,6-lactone raw material is preferably 5% by weight or less, more preferably 3% by weight or less, and even more preferably 0% by weight (i.e., reaction in the absence of ammonia).

[0036] The amount of 3-hydroxyadipic acid-3,6-lactone to be charged to the aqueous solvent is not particularly limited, but a small amount is not industrially preferable. From this viewpoint, the amount of 3-hydroxyadipic acid-3,6-lactone to be charged to the aqueous solvent is preferably 0.1 parts by weight or more, more preferably 0.2 parts by weight or more, and even more preferably 1.0 parts by weight or more.

[0037] [Recovery of adipic acid] Adipic acid can be recovered from the aqueous solution of adipic acid (carboxylic acid, carboxylate, carboxylate ester) produced by subjecting 3-hydroxyadipic acid-3,6-lactone to a hydrogenation process in an aqueous solvent by conventional separation and purification procedures such as filtration, distillation, extraction, and crystallization.

[0038] [Adipic acid] In the present invention, when water, a mixture of water and a primary alcohol, or a mixture of water and a water-miscible organic solvent other than a secondary alcohol is used as the solvent, when the carboxylic acid of 3-hydroxyadipic acid-3,6-lactone is used as the raw material, the carboxylic acid of adipic acid is generated, when the carboxylate of 3-hydroxyadipic acid-3,6-lactone is used as the raw material, the carboxylate of adipic acid is generated, and when the ester of 3-hydroxyadipic acid-3,6-lactone is used as the raw material, a mixture of adipic acid and an adipic acid monoester is generated. In the present invention, when the water-miscible organic solvent mixed with water is a primary or secondary alcohol such as methanol, ethanol, n-propanol, isopropanol, etc., a mixture of adipic acid, an adipic acid monoester, and an adipic acid diester is obtained after the reaction by esterification of the raw material and the generated adipic acid with these alcohols. In this specification, the carboxylic acid, carboxylate, carboxylate ester, and mixtures thereof of adipic acid are collectively referred to as "adipic acid."

[0039] [Various derivatizations] The adipic acid obtained in the present invention can be converted to an adipic acid diester by further subjecting it to an esterification reaction. The esterification method is not particularly limited, but for example, an esterification reaction using an acid catalyst and an alcohol solvent can be mentioned. The acid catalyst used here is not particularly limited, but examples thereof include mineral acids such as sulfuric acid and hydrochloric acid, and solid acids such as silica and strong acidic resins. Other esterification methods include dehydration condensation of alcohol and carboxylic acid using a condensing agent, dehydration condensation of alcohol and carboxylic acid using a Lewis acid catalyst such as boron trifluoride methanol complex, a production method under basic conditions using a metal alkoxide, and a method using an alkylating agent such as diazomethane or an alkyl halide.

[0040] Adiponitrile can be produced from the adipic acid obtained by the present invention by a known method (for example, JP-B-61-24555). Hexamethylenediamine can be produced by hydrogenating the obtained adiponitrile by a known method (for example, JP-T-2000-508305). Furthermore, polyamide 6,6 can be produced by polymerizing the adipic acid obtained by the present invention and the hexamethylenediamine obtained from the adipic acid by a known method (for example, see "Polyamide Resin Handbook" edited by Osamu Fukumoto, Nikkan Kogyo Shuppansha (January 1998)).

[0041] [Production of adipic acid from 3-hydroxyadipic acid fermentation broth] As described above, the present invention is characterized in that adipic acid is produced from 3-hydroxyadipic acid-3,6-lactone contained in an aqueous solvent, i.e., an aqueous solution containing 3-hydroxyadipic acid-3,6-lactone. The aqueous solution containing 3-hydroxyadipic acid-3,6-lactone may be prepared from a 3-hydroxyadipic acid fermentation liquid. Specifically, an acid may be added to the 3-hydroxyadipic acid fermentation liquid to adjust the pH to an acidic condition of less than pH 7, and the filtrate obtained by passing the fermentation liquid through a nanofiltration membrane may be subjected to the hydrogenation step.

[0042] 3-Hydroxyadipic acid is a dicarboxylic acid having six carbon atoms and a hydroxyl group (-OH) at the β-position.

[0043] The 3-hydroxyadipic acid fermentation broth includes not only a culture broth in which 3-hydroxyadipic acid is produced by the action of a microorganism in a liquid medium containing fermentation raw materials such as a carbon source, a nitrogen source, inorganic salts, amino acids, and vitamins, but also a culture broth in which a microorganism is cultured in a liquid medium containing the fermentation raw materials and to which 3-hydroxyadipic acid that has been separately chemically or biologically synthesized has been added. The 3-hydroxyadipic acid fermentation broth can be prepared, for example, by the method disclosed in International Publication WO 2017 / 209102.

[0044] By adding an acid to the 3-hydroxyadipic acid fermentation liquid to adjust the pH to an acidic condition of less than pH 7, 3-hydroxyadipic acid can easily pass through the nanofiltration membrane. Furthermore, by adding an acid to the 3-hydroxyadipic acid fermentation liquid, 3-hydroxyadipic acid-3,6-lactone is produced from the 3-hydroxyadipic acid in the aqueous solution. The lower the pH of the aqueous solution, the more likely it is that the production of 3-hydroxyadipic acid-3,6-lactone will be promoted, but it is necessary to consider the corrosion of the device associated with low pH conditions. In consideration of these factors, the pH is preferably 4.5 or less, more preferably 1.5 to 4.5, and even more preferably 2.0 to 4.0.

[0045] The acid used to adjust the pH of the 3-hydroxyadipic acid fermentation liquor is not particularly limited as long as it can adjust the pH to an acidic condition of less than pH 7. Mineral acids such as sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, and boric acid, and organic acids such as formic acid, acetic acid, and propionic acid can be preferably used.

[0046] The filtration of the 3-hydroxyadipic acid fermentation liquid through the nanofiltration membrane may be performed under pressure. The filtration pressure is not particularly limited, but is preferably in the range of 0.1 MPa to 8 MPa, since a pressure lower than 0.1 MPa reduces the membrane permeation rate, and a pressure higher than 8 MPa may damage the membrane, but is more preferably in the range of 0.5 MPa to 7 MPa, since the membrane permeation flux is high and 3-hydroxyadipic acid can be efficiently permeated.

[0047] In the present invention, the filtration of the 3-hydroxyadipic acid fermentation liquor through a nanofiltration membrane can improve the recovery rate of 3-hydroxyadipic acid or 3-hydroxyadipic acid-3,6-lactone by returning the non-permeated liquid to the raw water and repeatedly filtering it.

[0048] It is preferable to remove microbial cells, proteins, and solids resulting from protein denaturation from the 3-hydroxyadipic acid fermentation liquor before passing it through a nanofiltration membrane.

[0049] The method for removing the microbial cells is not particularly limited, and can be carried out by ordinary procedures such as separation using a microfiltration membrane (MF membrane) or centrifugation.

[0050] The method for removing the protein or solid matter generated by the denaturation of the protein is not particularly limited, and can be carried out by a conventional procedure such as separation using an ultrafiltration membrane (UF membrane).

[0051] The order in which the bacterial cells or proteins are removed is not particularly limited, but it is preferable to remove larger sized bacterial cells first, since this can prevent clogging of the ultrafiltration membrane when removing proteins.

[0052] The nanofiltration membrane material used in the present invention can be a polymeric material such as cellulose acetate polymer, polyamide, polyester, polyimide, vinyl polymer, etc., but is not limited to a membrane made of one of the above materials, and may be a membrane containing multiple membrane materials. The membrane structure may be either an asymmetric membrane having a dense layer on at least one side of the membrane and gradually increasing pore sizes from the dense layer toward the inside of the membrane or the other side, or a composite membrane having a very thin functional layer made of another material on the dense layer of the asymmetric membrane. For example, a composite membrane can be used, which is a nanofiltration membrane made of a polyamide functional layer on a support membrane made of polysulfone as a membrane material, as described in JP-A-62-201606.

[0053] In the present invention, among these, a composite membrane having a polyamide as a functional layer is preferred, which has high pressure resistance, high water permeability, high solute removal performance, and excellent potential. Furthermore, in order to maintain durability against operating pressure, high water permeability, and blocking performance, a structure in which a polyamide is used as a functional layer and is supported by a support made of a porous membrane or nonwoven fabric is preferred. In a nanofiltration membrane having a polyamide as a functional layer, preferred carboxylic acid components of the monomer constituting the polyamide include, for example, aromatic carboxylic acids such as trimesic acid, benzophenone tetracarboxylic acid, trimellitic acid, pyromet acid, isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, diphenyl carboxylic acid, and pyridine carboxylic acid, but in consideration of solubility in a membrane-forming solvent, trimesic acid, isophthalic acid, terephthalic acid, or a mixture thereof is more preferred.

[0054] Preferred amine components of the monomers constituting the polyamide include m-phenylenediamine, p-phenylenediamine, benzidine, methylenebisdianiline, 4,4'-diaminobiphenyl ether, dianisidine, 3,3',4-triaminobiphenyl ether, 3,3',4,4'-tetraaminobiphenyl ether, 3,3'-dioxybenzidine, 1,8-naphthalenediamine, m(p)-monomethylphenylenediamine, 3,3'-monomethylamino-4,4'-diaminobiphenyl ether, 4,N,N'-(4-amino- Examples of the diamine include primary diamines having an aromatic ring such as 2,2'-bis(4-aminophenylbenzoyl)-p(m)-phenylenediamine-2,2'-bis(4-aminophenylbenzimidazole), 2,2'-bis(4-aminophenylbenzoxazole), and 2,2'-bis(4-aminophenylbenzothiazole), and secondary diamines such as piperazine, piperidine, or derivatives thereof. Among them, nanofiltration membranes having a crosslinked polyamide containing piperazine or piperidine as a monomer as a functional layer are preferably used because they have pressure resistance, durability, heat resistance, and chemical resistance. More preferred are nanofiltration membranes having the crosslinked piperazine polyamide or crosslinked piperidine polyamide as the main component. Examples of nanofiltration membranes having a polyamide containing piperazine polyamide as a functional layer include those described in JP-A-62-201606, and specific examples include UTC-60 and UTC-63, which are crosslinked piperazine polyamide-based semipermeable membranes manufactured by Toray Industries, Inc.

[0055] Examples of the spiral-type nanofiltration membrane element used in the present invention include nanofilter modules SU-210, SU-220, SU-600, and SU-610 manufactured by Toray Industries, Inc., including UTC-60 and UTC-63 manufactured by the same company, which have a crosslinked piperazine polyamide functional layer. Other examples include nanofiltration membranes NF-45, NF-90, NF-200, and NF-400 manufactured by Filmtec Co., Ltd., which have a crosslinked piperazine polyamide functional layer, nanofiltration membranes NF99, NF97, and NF99HF manufactured by Alfa Laval Co., Ltd., which have a polyamide functional layer, and GEsepa, a cellulose acetate-based nanofiltration membrane manufactured by GE Osmonics.

[0056] The filtrate of the 3-hydroxyadipic acid fermentation liquor through the nanofiltration membrane can be passed through a reverse osmosis membrane (RO membrane) to concentrate 3-hydroxyadipic acid or 3-hydroxyadipic acid-3,6-lactone on the non-permeated side, and the resulting concentrate may be subjected to the hydrogenation step.

[0057] As the membrane material of the reverse osmosis membrane used in the present invention, generally commercially available polymeric materials such as cellulose acetate polymers, polyamides, polyesters, polyimides, vinyl polymers, etc. can be used, but the membrane is not limited to being made of one type of material, and may be made of a plurality of membrane materials. As the membrane form, any suitable form such as a flat membrane type, a spiral type, a hollow fiber type, etc. can be used.

[0058] Specific examples of the reverse osmosis membrane used in the present invention include polyamide reverse osmosis membranes (UTC) SU-710, SU-720, SU-720F, SU-710L, SU-720L, SU-720LF, SU-720R, SU-710P, SU-720P, SU-810, SU-820, SU-820L, and SU-820FA manufactured by Toray Industries, Inc., and cellulose acetate reverse osmosis membranes SC-L100R, SC-L200R, SC-L200R, and SC-L300R manufactured by Toray Industries, Inc. 1100, SC-1200, SC-2100, SC-2200, SC-3100, SC-3200, SC-8100, SC-8200, NTR-759HR, NTR-729HF, NTR-70SWC, ES10-D, ES20-D, ES20-U, ES15-D, ES15-U, LF10-D manufactured by Nitto Denko Corporation, RO98pHt, RO99, HR98PP, CE4040C-30D manufactured by Alfa Laval, GE Sepa manufactured by GE, and BW30-4040, TW30-4040, XLE-4040, LP-4040, LE-4040, SW30-4040, SW30HRLE-4040 manufactured by Filmtec.

[0059] Filtration through a reverse osmosis membrane is performed under pressure, and since a filtration pressure lower than 1 MPa reduces the membrane permeation rate, and a filtration pressure higher than 8 MPa can damage the membrane, the filtration pressure is preferably in the range of 1 MPa to 8 MPa, more preferably in the range of 1 MPa to 7 MPa, and even more preferably in the range of 2 MPa to 6 MPa.

[0060] [Adipic acid solution] In the present invention, the raw material 3-hydroxyadipic acid-3,6-lactone is converted to adipic acid in an aqueous solvent, and thus an aqueous solvent containing adipic acid is obtained after the reaction. In the present invention, the aqueous adipic acid solution refers to the aqueous solvent containing adipic acid obtained after the reaction.

[0061] When 3-hydroxyadipic acid-3,6-lactone is converted to adipic acid, n-valeric acid (n-pentanoic acid in IUPAC systematic name) is generated as a by-product, and an aqueous adipic acid solution containing a trace amount of n-valeric acid is obtained. The n-valeric acid contained in the aqueous adipic acid solution exists in the form of a carboxylic acid, a carboxylate, a carboxylate ester, or a mixture thereof, and in this specification, these forms are collectively referred to as "n-valeric acid".

[0062] The content of n-valeric acid in the aqueous adipic acid solution is suitably 0.01 to 20 parts by weight, preferably 0.02 to 18 parts by weight, more preferably 0.05 to 16 parts by weight. If the content of n-valeric acid in the aqueous adipic acid solution is more than 20 parts by weight, it may be unsuitable as a polyamide raw material. On the other hand, preparing an aqueous adipic acid solution having an n-valeric acid content of less than 0.01 parts by weight from an aqueous adipic acid solution having an n-valeric acid content of 0.01 to 20 parts by weight relative to 100 parts by weight of adipic acid may not provide any particular advantage as a polyamide raw material compared to the solution before purification, despite imposing an excessive burden on purification. EXAMPLES

[0063] The present invention will be described in more detail below using examples, but the present invention is not limited to the following examples. The reaction results in the examples and comparative examples are defined by the following formula.

[0064] Raw material conversion rate (mol%) = reacted raw material (mol) / feed raw material (mol) × 100.

[0065] Adipic acid selectivity (mol%) = adipic acid production (mol) / reacted raw material (mol) × 100.

[0066] The reaction solution and the aqueous solution of the concentrated reaction solution were analyzed by gas chromatography (GC) and high performance liquid chromatography (HPLC), respectively. The amount of the product was quantified by an absolute calibration curve prepared using a standard sample. The analytical conditions for GC and HPLC are shown below.

[0067] [GC analysis conditions] GC equipment: "GC2010 plus" (Shimadzu Corporation) Column: "InertCap for amines", length 30 m, inner diameter 0.32 mm (GL Sciences) Carrier gas: Helium, constant linear velocity (40.0 cm / sec) Vaporization chamber temperature: 250℃ Detector temperature: 250℃ Column oven temperature: 100°C → (10°C / min) → 230°C 10 min (total 23 min) Detector: FID.

[0068] [HPLC analysis conditions 1] HPLC equipment: "Prominence" (Shimadzu Corporation) Column: "Synergi hydro-RP" (Phenomenex), length 250 mm, inner diameter 4.60 mm, particle size 4 μm Mobile phase: 0.1% by weight phosphoric acid aqueous solution / acetonitrile = 95 / 5 (volume ratio) Flow rate: 1.0mL / min Detector: UV (210 nm) Column temperature: 40°C. Analysis time: 23 minutes.

[0069] The pH of each aqueous solution was analyzed by the following method.

[0070] [pH analysis method] A Horiba pH meter F-52 (Horiba, Ltd.) was used. pH calibration was performed using a pH 4.01 standard solution (FUJIFILM Wako Pure Chemical Industries, Ltd.), a pH 6.86 standard solution (FUJIFILM Wako Pure Chemical Industries, Ltd.), and a pH 9.18 standard solution (FUJIFILM Wako Pure Chemical Industries, Ltd.).

[0071] (Reference Example 1) Preparation of 3-hydroxyadipic acid-3,6-lactone The 3-hydroxyadipic acid-3,6-lactone used in the present invention was prepared by chemical synthesis. First, 1.5 L of ultra-dehydrated tetrahydrofuran (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) was added to 13.2 g (0.1 mol) of succinic acid monomethyl ester (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), and 16.2 g (0.1 mol) of carbonyldiimidazole (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) was added while stirring, and the mixture was stirred at room temperature for 1 hour under a nitrogen atmosphere. 15.6 g (0.1 mol) of malonic acid monomethyl ester potassium salt and 9.5 g (0.1 mol) of magnesium chloride were added to this suspension, and the mixture was stirred at room temperature for 1 hour under a nitrogen atmosphere, and then stirred at 40°C for 12 hours. After the reaction was completed, 0.05 L of 1 mol / L hydrochloric acid was added, extracted with ethyl acetate, and separated and purified by silica gel column chromatography (hexane:ethyl acetate = 1:5), to obtain 13.1 g of pure 3-oxohexanedicarboxylic acid dimethyl ester.

[0072] 0.1L of methanol (Kokusan Chemical Co., Ltd.) was added to 10g (0.05mol) of the obtained 3-oxohexanedicarboxylic acid dimethyl ester, and 0.02L of 5mol / L aqueous sodium hydroxide solution was added while stirring, and the mixture was stirred at room temperature for 2 hours. After the reaction was completed, the mixture was adjusted to pH 1 with 5mol / L hydrochloric acid, and then 2.0g (0.05mol) of sodium borohydride (FUJIFILM Wako Pure Chemical Co., Ltd.) was added and stirred at room temperature for 2 hours. After concentration with a rotary evaporator, 0.1L of ultrapure water was added, and 0.01L of 1mol / L sulfuric acid was added while stirring, and the mixture was stirred at 100°C for 2 hours. After the reaction was completed, the mixture was concentrated with a rotary evaporator, and then separated and purified by silica gel column chromatography (chloroform:methanol=10:1) to obtain 5.8g of pure 3-hydroxyadipic acid-3,6-lactone (carboxylic acid) (light yellow syrup). The NMR spectrum of the obtained 3-hydroxyadipic acid-3,6-lactone is as follows:

[0073] 1 H-NMR (400MHz, D2O): δ2.03 (m, 1H), δ2.04-2.90 (m, 5H), δ5.00 (m, 1H).

[0074] (Example 1) Production of adipic acid 0.144g of 3-hydroxyadipic acid-3,6-lactone (carboxylic acid), 50mL of water, and 0.025g of Palladium, 5% on gamma alumina powder, reduced (5%Pd / Al2O3, Alfa Aesar) were added to a 0.1L stainless steel autoclave (Taiatsu Glass Industry Co., Ltd.). After purging the autoclave with nitrogen, hydrogen gas was added and the hydrogen partial pressure in the autoclave was adjusted to 0.9MPa. The temperature in the autoclave was then raised to 200°C. The gauge pressure at 200°C was 1.5MPa. After keeping at 200°C for 3 hours, the autoclave was allowed to cool to room temperature, the gas in the autoclave was released to return to normal pressure, and the reaction solution was recovered. The catalyst was removed by filtration, and a portion of the filtrate was sampled. The filtrate was also concentrated with a rotary evaporator (Tokyo Rikakikai Co., Ltd.) to obtain a concentrate. The sampled filtrate and 1 g / L aqueous solution of the concentrate were analyzed by GC and HPLC (HPLC analysis condition 1). The results are shown in Table 1. Adipic acid was produced with a high raw material conversion and a high adipic acid selectivity.

[0075] (Example 2) Production of adipic acid The reaction was carried out in the same manner as in Example 1, except that 2.5 g of 3-hydroxyadipic acid-3,6-lactone (carboxylic acid) was used as the raw material. The results are shown in Table 1. Even when the raw material concentration was increased, the raw material conversion rate and adipic acid selectivity were significantly high.

[0076] (Comparative Example 1) Production of Adipic Acid Except for using dioxane instead of water as a solvent, the reaction was carried out in the same manner as in Example 1. The results are shown in Table 1. The raw material conversion rate was only 67.4%.

[0077] (Comparative Example 2) Production of Adipic Acid Except for using tert-butanol instead of water as a solvent, the reaction was carried out in the same manner as in Example 1. The results are shown in Table 1. The raw material conversion was significantly low at 38.9%, and the adipic acid selectivity was also only 87.0%.

[0078] [Table 1]

[0079] (Reference Example 2) Preparation of 3-hydroxyadipic acid The 3-hydroxyadipic acid used in the present invention was prepared by chemical synthesis. First, 1.5 L of ultra-dehydrated tetrahydrofuran (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) was added to 13.2 g (0.1 mol) of succinic acid monomethyl ester (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), and 16.2 g (0.1 mol) of carbonyldiimidazole (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) was added while stirring, and the mixture was stirred at room temperature for 1 hour under a nitrogen atmosphere. 15.6 g (0.1 mol) of malonic acid monomethyl ester potassium salt and 9.5 g (0.1 mol) of magnesium chloride were added to this suspension, and the mixture was stirred at room temperature for 1 hour under a nitrogen atmosphere, and then stirred at 40°C for 12 hours. After the reaction was completed, 0.05 L of 1 mol / L hydrochloric acid was added, extracted with ethyl acetate, and separated and purified by silica gel column chromatography (hexane:ethyl acetate = 1:5), to obtain 13.1 g of pure 3-oxohexanedicarboxylic acid dimethyl ester.

[0080] 0.1L of methanol (Kokusan Chemical Co., Ltd.) was added to 10g (0.05mol) of the obtained 3-oxohexanedicarboxylic acid dimethyl ester, and 0.02L of 5mol / L aqueous sodium hydroxide solution was added while stirring, and the mixture was stirred at room temperature for 2 hours. After the reaction was completed, the mixture was adjusted to pH 1 with 5mol / L hydrochloric acid, and then 2.0g (0.05mol) of sodium borohydride (Wako Pure Chemical Industries, Ltd.) was added and the mixture was stirred at room temperature for 2 hours. After the reaction was completed, the mixture was concentrated with a rotary evaporator and recrystallized with water to obtain 7.2g of pure 3-hydroxyadipic acid. The NMR spectrum of the obtained 3-hydroxyadipic acid is as follows.

[0081] 1 H-NMR (400MHz, CD3OD): δ1.70 (m, 1H), δ1.83 (m, 1H), δ2.42 (m, 4H), δ4.01 (m, 1H).

[0082] (Reference Example 3) Preparation of 3-hydroxyadipic acid fermentation broth 3-Hydroxyadipic acid prepared in Reference Example 2 was added to a culture solution prepared according to the method using Serratia grimesii (NBRC13537) / pBBR1MCS-2:: CgpcaF strain described in Example 14 of WO 2017 / 209102 to prepare 4 L of 3-hydroxyadipic acid fermentation liquid. The supernatant was analyzed by HPLC. 3-hydroxyadipic acid concentration 14 g / L, 3-hydroxyadipic acid-3,6-lactone not detected. pH 6.8.

[0083] (Example 3) Production of adipic acid 4 L of the 3-hydroxyadipic acid fermentation liquid prepared in Reference Example 3 was passed through a microfiltration membrane (porous membrane with a pore size of 0.01 μm or more and less than 1 μm: manufactured by Toray Industries, Inc.). Then, concentrated sulfuric acid (manufactured by Sigma-Aldrich Co.) was added to adjust the pH to 4.0, and the mixture was stirred for 12 hours. This aqueous solution was passed through an ultrafiltration membrane (molecular weight cutoff 10000; manufactured by Toray Industries, Inc.) (3-hydroxyadipic acid-3,6-lactone concentration 0.6 g / L). 3 L of the aqueous solution thus obtained was passed through a nanofiltration membrane under the following nanofiltration membrane treatment conditions to obtain a filtrate (3-hydroxyadipic acid-3,6-lactone concentration 0.5 g / L).

[0084] [Nanofiltration membrane treatment conditions] Separation membrane: UTC-63 (manufactured by Toray Industries, Inc.) Membrane separation device: "SEPA" (registered trademark) CF-II (manufactured by GE W&PT) Operating temperature: 25℃ Filtration pressure: 0.5MPa.

[0085] In a stainless steel autoclave (manufactured by Taiatsu Glass Industry Co., Ltd.) with a capacity of 0.1 L, 30 mL of the filtrate (3-hydroxyadipic acid-3,6-lactone concentration 0.5 g / L) and 0.025 g of Palladium, 5% on gamma alumina powder, reduced (5% Pd / Al2O3, manufactured by Alfa Aesar) were added as a catalyst. After purging the inside of the autoclave with nitrogen, hydrogen gas was added and the hydrogen partial pressure in the autoclave was adjusted to 0.9 MPa. The temperature in the autoclave was then raised to 200°C. The gauge pressure at 200°C was 1.5 MPa. After keeping at 200°C for 3 hours, the mixture was allowed to cool to room temperature, the gas in the autoclave was released to return to normal pressure, and the reaction solution was collected. The catalyst was removed by filtration, and the supernatant adipic acid aqueous solution was analyzed by HPLC, and the adipic acid concentration was 0.1 g / L.

[0086] (Comparative Example 3) Production of Adipic Acid The reaction was carried out in the same manner as in Example 3, except that the aqueous solution after passing through the ultrafiltration membrane was not passed through the nanofiltration membrane, but no adipic acid was produced.

[0087] Example 3 and Comparative Example 3 show that adipic acid can be produced by adding an acid to the 3-hydroxyadipic acid fermentation liquid to adjust the pH to less than 7, passing the liquid through a nanofiltration membrane, and subjecting the filtrate to a hydrogenation process.

[0088] In the following Examples, the reaction solution and the aqueous solution of the concentrated reaction solution were analyzed by HPLC under the following HPLC analysis conditions 2. Under these analysis conditions, in addition to adipic acid, it is possible to detect and quantify n-valeric acid, which is a by-product obtained by conversion of 3-hydroxyadipic acid-3,6-lactone.

[0089] [HPLC analysis conditions 2] HPLC equipment: "Prominence" (Shimadzu Corporation) Column: "Synergi hydro-RP" (Phenomenex), length 250 mm, inner diameter 4.60 mm, particle size 4 μm Mobile phase: 0.1 wt% phosphoric acid aqueous solution / acetonitrile 0-10 min: constant at 95 / 5 (volume ratio), 10-20 min: 95 / 5→80 / 20 (volume ratio), 20-40 min: 80 / 20→30 / 70 (volume ratio), 40-50 min: constant at 30 / 70 (volume ratio) Flow rate: 1.0mL / min Detector: UV (210 nm) Column temperature: 40°C. Analysis time: 50 minutes.

[0090] The selectivity for n-valeric acid was defined by the following formula:

[0091] n-Valeric acid selectivity (mol%) = n-valeric acid production (mol) / reacted raw material (mol) × 100.

[0092] (Example 4) Production of adipic acid An aqueous solution of adipic acid was obtained by carrying out the reaction in the same manner as in Example 1, except that the HPLC analysis was carried out under HPLC analysis condition 2. The results are shown in Table 2.

[0093] (Example 5) Production of adipic acid The reaction was carried out in the same manner as in Example 2, except that HPLC analysis was performed under HPLC analysis condition 2. The results are shown in Table 2.

[0094] (Reference Example 4) Preparation of 3-hydroxyadipic acid-3,6-lactone methyl ester The 3-hydroxyadipic acid-3,6-lactone methyl ester used in the present invention was prepared by chemical synthesis. 100 mL of ultra-dehydrated methanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added to 10.0 g (0.06 mol) of 3-hydroxyadipic acid, and 5 drops of concentrated sulfuric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were added while stirring, and the mixture was refluxed at 70°C for 5 hours. After the reaction was completed, the mixture was concentrated using a rotary evaporator, and then separated and purified by silica gel column chromatography (hexane:ethyl acetate=4:1) to obtain 5.4 g of pure 3-hydroxyadipic acid-3,6-lactone methyl ester (yield 48%). The NMR spectrum of the obtained 3-hydroxyadipic acid-3,6-lactone methyl ester is as follows.

[0095] 1 H-NMR (400MHz, CDCl3): δ1.93-2.02(m, 1H), δ2.44-2.52(m, 1H), δ2.56-2.8 7(m, 2H), δ2.66(dd, 1H), δ2.85(dd, 1H), δ3.73(s, 3H), δ4.87-4.94(m, 1H).

[0096] (Example 6) Production of adipic acid The reaction was carried out in the same manner as in Example 5, except that 2.5 g of 3-hydroxyadipic acid-3,6-lactone methyl ester prepared in Reference Example 4 was used as the raw material, to obtain an aqueous adipic acid solution. The results are shown in Table 2.

[0097] (Example 7) Production of adipic acid 2g of 3-hydroxyadipic acid-3,6-lactone (carboxylic acid), 20mL of water, and 0.1g of Palladium, 5% on gamma alumina powder, reduced (5%Pd / Al2O3, Alfa Aesar) as a catalyst were added to a 0.1L stainless steel autoclave (Taiatsu Glass Industry Co., Ltd.). After purging the autoclave with nitrogen, hydrogen gas was added and the hydrogen partial pressure was adjusted to 0.9MPa. The temperature inside the autoclave was then raised to 200°C. After keeping it at 200°C for 6 hours, it was allowed to cool to room temperature, and the gas inside the autoclave was released to return it to normal pressure. The solution inside the autoclave was collected in a 200mL measuring flask and made up to 100mL with water. The catalyst was precipitated by centrifugation, and the supernatant adipic acid aqueous solution was analyzed by GC and HPLC (HPLC analysis condition 2). The results are shown in Table 2.

[0098] (Example 8) Production of adipic acid The reaction was carried out in the same manner as in Example 7, except that the reaction temperature was 150° C. and the reaction time was 12 hours, to obtain an aqueous adipic acid solution. The results are shown in Table 2.

[0099] (Example 9) Production of adipic acid The reaction was carried out in the same manner as in Example 7, except that the reaction temperature was 160° C. and the reaction time was 9 hours, to obtain an aqueous adipic acid solution. The results are shown in Table 2.

[0100] (Example 10) Production of adipic acid The reaction was carried out in the same manner as in Example 7, except that the reaction temperature was 170° C. and the reaction time was 7 hours, to obtain an aqueous adipic acid solution. The results are shown in Table 2.

[0101] (Example 11) Production of adipic acid The reaction was carried out in the same manner as in Example 7, except that the reaction temperature was 180° C., to obtain an aqueous adipic acid solution. The results are shown in Table 2.

[0102] (Example 12) Production of adipic acid The reaction was carried out in the same manner as in Example 7, except that the reaction temperature was 220° C. and the reaction time was 3 hours, to obtain an aqueous adipic acid solution. The results are shown in Table 2.

[0103] (Example 13) Production of adipic acid The reaction was carried out in the same manner as in Example 10, except that 5% palladium supported on carbon (5% Pd / C, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used as the catalyst and the reaction time was 8 hours, to obtain an aqueous adipic acid solution. The results are shown in Table 2.

[0104] (Example 14) Production of adipic acid The reaction was carried out in the same manner as in Example 10, except that 5% platinum supported carbon (5% Pt / C, manufactured by Sigma-Aldrich) was used as the catalyst and the reaction time was changed to 9 hours, to obtain an aqueous adipic acid solution. The results are shown in Table 2.

[0105] (Example 15) Production of adipic acid The pH of the 3-hydroxyadipic acid-3,6-lactone aqueous solution was adjusted to 6 using 1 mol / L sodium hydroxide aqueous solution (manufactured by Nacalai Tesque, Inc.), nickel on silica-alumina (Ni / SiO2-Al2O3, manufactured by Alfa Aesar) was used as the catalyst, and the reaction time was 8 hours, but the same reaction as in Example 10 was carried out to obtain an aqueous adipic acid solution. The results are shown in Table 2.

[0106] (Example 16) Production of adipic acid The pH of the 3-hydroxyadipic acid-3,6-lactone aqueous solution was adjusted to 6 using 1 mol / L sodium hydroxide aqueous solution (manufactured by Nacalai Tesque, Inc.), Raney nickel (Raney Ni, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used as the catalyst, and the reaction time was set to 6 hours, but the reaction was carried out in the same manner as in Example 10 to obtain an aqueous adipic acid solution. The results are shown in Table 2.

[0107] (Example 17) Production of adipic acid The reaction was carried out in the same manner as in Example 7 except that the hydrogen partial pressure was set to 3.0 MPa, to obtain an aqueous adipic acid solution. The results are shown in Table 2.

[0108] (Example 18) Production of adipic acid 0.189g of 3-hydroxyadipic acid-3,6-lactone (carboxylic acid), 30mL of a water / methanol mixed solvent (60% by volume of water), and 0.025g of Palladium, 5% on gamma alumina powder, reduced (5%Pd / Al2O3, Alfa Aesar) as a catalyst were added to a 0.1L stainless steel autoclave (manufactured by Taiatsu Glass Industry Co., Ltd.). After purging the inside of the autoclave with nitrogen, hydrogen gas was added and the hydrogen partial pressure was adjusted to 0.9MPa. The temperature inside the autoclave was then raised to 170°C. After maintaining at 170°C for 12 hours, it was allowed to cool to room temperature, and the gas inside the autoclave was released to return to normal pressure. The solution inside the autoclave was collected in a 50mL measuring flask and made up to 100mL with methanol. The catalyst was precipitated by centrifugation, and the supernatant adipic acid aqueous solution was analyzed by GC and HPLC (HPLC analysis condition 2). The results are shown in Table 2.

[0109] (Example 19) Production of adipic acid 0.159g of 3-hydroxyadipic acid-3,6-lactone (carboxylic acid), 30mL of a water / dioxane mixed solvent (water 90% by volume), and 0.025g of Palladium, 5% on gamma alumina powder, reduced (5%Pd / Al2O3, Alfa Aesar) as a catalyst were added to a 0.1L stainless steel autoclave (manufactured by Taiatsu Glass Industry Co., Ltd.). After purging the inside of the autoclave with nitrogen, hydrogen gas was added and the hydrogen partial pressure was adjusted to 0.9MPa. The temperature inside the autoclave was then raised to 220°C. After keeping it at 220°C for 3 hours, it was allowed to cool to room temperature, and the gas inside the autoclave was released to return it to normal pressure. The solution inside the autoclave was collected in a 50mL measuring flask and made up to 100mL with water. The catalyst was precipitated by centrifugation, and the supernatant adipic acid aqueous solution was analyzed by GC and HPLC (HPLC analysis condition 2). The results are shown in Table 2.

[0110] (Example 20) Production of adipic acid The reaction was carried out in the same manner as in Example 19, except that tert-butanol was used instead of dioxane, the reaction temperature was 200° C., and the reaction time was 4 hours, to obtain an aqueous adipic acid solution. The results are shown in Table 2.

[0111] [Table 2]

Claims

1. A method for producing adipic acid, comprising: a step of producing a raw material containing 3-hydroxyadipic acid-3,6-lactone as a main component from 3-hydroxyadipic acid; and a step (hydrogenation step) of reacting the raw material with hydrogen in an aqueous solvent in the presence of a hydrogenation catalyst.

2. 2. The method of claim 1, wherein the hydrogenation catalyst comprises one or more transition metal elements selected from the group consisting of palladium, platinum, ruthenium, rhodium, rhenium, nickel, cobalt, iron, iridium, osmium, copper and chromium.

3. 3. The process according to claim 1 or 2, wherein the hydrogenation catalyst is supported on a carrier.

4. The method according to claim 3 , wherein the support is an acid catalytically active support.

5. The method according to any one of claims 1 to 4, wherein the reaction temperature of the hydrogenation step is 100 to 350°C.

6. The process according to any one of claims 1 to 5, wherein the hydrogenation step is carried out in the absence of ammonia.

7. The method according to any one of claims 1 to 6, wherein the 3-hydroxyadipic acid fermentation liquor is adjusted to a pH of less than 7 by adding an acid, and then the filtrate obtained by passing the liquor through a nanofiltration membrane is subjected to the hydrogenation step.

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