Apparatus for producing adipic acid, and method for producing adipic acid

Abstract

The present invention provides an apparatus for producing adipic acid from muconic acid under industrially advantageous conditions, and a method for producing adipic acid. [Solution] An apparatus for producing adipic acid, comprising: a supply means (A) for supplying muconic acid, alcohol, water, a hydrogenation catalyst, and hydrogen to a hydrogenation reactor (B); a hydrogenation reactor (B); a means (C) for recovering adipic acid and a mixture of alcohol and water from the hydrogenation reaction products discharged from the hydrogenation reactor (B); and a means (D) for recycling the mixture of alcohol and water recovered by means (C) to the supply means (A).

Description

Technical Field

[0001] The present invention relates to an adipic acid production apparatus, an adipic acid production method, adipic acid, and a method for producing polyamide.

Background Art

[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), but a large amount of nitrous oxide gas with a high greenhouse effect is by-produced. Therefore, a method for producing adipic acid using biomass, which is a renewable resource, or a substance derivable from biomass resources as a raw material is desired. As such a method, a method for producing adipic acid by hydrogenating muconic acid, which is a substance derivable from biomass resources (Patent Document 1, Patent Document 2) has been proposed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] Regarding a method for producing adipic acid using muconic acid, which can be derived from biomass resources, Patent Document 1 describes a method for producing adipic acid in high yield by reacting muconic acid with hydrogen in an alcohol solvent in the presence of a hydrogenation catalyst. The produced adipic acid is recovered by separating the catalyst, evaporating and distilling off the alcohol to concentrate it, and then crystallizing it in alcohol. However, because adipic acid has high solubility in alcohol, it is in principle difficult to avoid adipic acid loss in the crystallization process. To reduce adipic acid loss in the crystallization process, it is preferable to perform crystallization in water, where adipic acid has low solubility. In order to produce adipic acid in an alcohol solvent and then perform crystallization in water, it is necessary to replace the alcohol solvent with water. Replacement with water is achieved by evaporating the alcohol, adding water, and repeating the process of evaporating the alcohol again. In this process, a mixture of alcohol and water is obtained on the evaporation side. However, in order to recycle the alcohol as a solvent for muconate hydrolysis, it is necessary to separate the alcohol from the mixture of alcohol and water. Separating the alcohol from the mixture of alcohol and water requires additional separation equipment, such as permeation membrane separation, in addition to the usual distillation apparatus, which leads to a larger apparatus.

[0005] Patent Document 2 describes a method for producing adipic acid by reacting muconic acid with hydrogen in an aqueous liquid in the presence of a hydrogenation catalyst. It states that water is particularly advantageous as the aqueous liquid, but according to the inventors' investigation, the production of adipic acid was not confirmed when muconic acid was hydrogenated in water, and it was found that water is not a suitable solvent. Patent Document 2 indicates that the aqueous liquid may contain an organic solvent, but alcohol-based solvents are not given as examples of organic solvents to be included in the aqueous liquid because they have the disadvantage of reducing the yield of adipic acid.

[0006] If the hydrogenation of muconic acid could be carried out in a mixed solvent of alcohol and water, it would be possible to recycle the alcohol without requiring additional alcohol separation equipment, but there is no description or suggestion of such a technology. [Means for solving the problem]

[0007] The inventors of the present invention conducted intensive research to solve the above problems and, as a result, discovered that adipic acid can be produced in high yield and the alcohol can be easily recovered by reacting muconic acid, a substance that can be derived from biomass resources, with hydrogen in a mixed solvent of alcohol and water in the presence of a hydrogenation catalyst, thereby completing the present invention.

[0008] In other words, the present invention has the following configuration. [1] An apparatus for producing adipic acid, comprising: a supply means (A) for supplying muconic acid, alcohol, water, a hydrogenation catalyst, and hydrogen to a hydrogenation reactor (B); a hydrogenation reactor (B); a means (C) for recovering adipic acid and a mixture of alcohol and water from the hydrogenation reaction products discharged from the hydrogenation reactor (B); and a means (D) for recycling the mixture of alcohol and water recovered by means (C) to the supply means (A). [2] A method for producing adipic acid, comprising a hydrogenation step of reacting muconic acid with hydrogen in a mixed solvent of alcohol and water in the presence of a hydrogenation catalyst to obtain a hydrogenation reaction product. [3] The method for producing adipic acid according to [2] above, wherein the alcohol is one or more alcohols selected from the group consisting of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, and tert-butanol. [4] The method for producing adipic acid according to [2] or [3] above, wherein the alcohol content in the mixed solvent is 70% by mass or more and 95% by mass or less. [5] A method for producing adipic acid according to any one of [2] to [4] above, comprising an alcohol recovery step of recovering a mixture of alcohol and water from the hydrogenation reaction product obtained in the hydrogenation step. [6] A method for producing adipic acid according to [5] above, comprising a recycling step of recycling the mixture of alcohol and water recovered in the alcohol recovery step to a hydrogenation step. [7] Adipic acid obtained by any of the methods for producing adipic acid described in [2] to [6] above. [8] A method for producing polyamide comprising the following steps (1) and (2). (1) A step of producing adipic acid by the method for producing adipic acid described in any of [2] to [6] above. (2) A step of polymerizing the adipic acid obtained in step (1) with a diamine. [Effects of the Invention]

[0009] The present invention makes it possible to produce adipic acid from muconic acid in high yield without requiring large-scale equipment for alcohol recovery. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic flow diagram of an adipic acid production apparatus as one embodiment of the present invention. [Figure 2] This is a schematic flowchart of an adipic acid production apparatus, illustrating another embodiment of the present invention. [Modes for carrying out the invention]

[0011] The present invention will be described in more detail below.

[0012] The present invention provides a method for producing adipic acid, which includes a hydrogenation step in which muconic acid is reacted with hydrogen in a mixed solvent of alcohol and water in the presence of a hydrogenation catalyst to obtain a hydrogenation reaction product. The components are described below.

[0013] [Muconic acid] In the present invention, muconic acid (IUPAC name: hexa-2,4-dienedioic acid) is not particularly limited as long as it is muconic acid, and may be cis,cis-muconic acid, cis,trans-muconic acid, trans,trans-muconic acid, or a mixture thereof, but cis,cis-muconic acid is preferred from the viewpoint of availability.

[0014] Itaconic acid can be derived from biomass resources. For example, International Publication No. 2011 / 085311 discloses a method for fermentatively producing cis,cis-itaconic acid from glucose by microbial fermentation, and International Publication No. 2018 / 199111 discloses a method for fermentatively producing cis,cis-itaconic acid from lignin-derived aromatic compounds.

[0015] In the present invention, itaconic acid may be a carboxylic acid (-COOH), carboxylate (-COO - ) or carboxylic acid ester (-COOR), or a mixture thereof, and these can be used as starting materials in the present invention. In this specification, these are collectively referred to as "itaconic acid".

[0016] Examples of the carboxylate of itaconic acid include ammonium itaconate, lithium itaconate, sodium itaconate, potassium itaconate, magnesium itaconate, calcium itaconate, and the like.

[0017] Examples of the carboxylic acid ester of itaconic acid include monomethyl itaconate, dimethyl itaconate, monoethyl itaconate, diethyl itaconate, mono-n-propyl itaconate, di-n-propyl itaconate, monoisopropyl itaconate, diisopropyl itaconate, and the like.

[0018] [Mixed solvent of alcohol and water] In the present invention, adipic acid is produced from itaconic acid in a mixed solvent of alcohol and water. The alcohol in the present invention is not particularly limited, but is preferably one or more alcohols selected from the group consisting of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, and tert-butanol, more preferably one or more alcohols selected from the group consisting of ethanol, n-propanol, and isopropanol, and even more preferably ethanol.

[0019] The alcohol content in the mixed solvent of alcohol and water is 10% by mass or more and 99% by mass or less, preferably 50% by mass or more and 97% by mass or less, and more preferably 70% by mass or more and 95% by mass or less.

[0020] [Hydrogenation catalyst] In this invention, adipic acid is produced from muconic acid in the presence of a hydrogenation catalyst. The hydrogenation catalyst used in this invention is not particularly limited as long as it has 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) in the presence of hydrogen.

[0021] The hydrogenation catalyst preferably contains a transition metal element, more preferably one or more selected from the group consisting of palladium, platinum, ruthenium, rhodium, rhenium, nickel, cobalt, iron, iridium, osmium, copper, and chromium, and even more preferably one or more selected from the group consisting of palladium, platinum, rhodium, rhenium, and nickel.

[0022] The state in which the hydrogenation catalyst exists is not particularly limited, but it may be in a cluster state, a nanoparticle state, a microparticle state, a bulk state, a state dispersed in solution like a colloid, or a state uniformly dissolved in a solvent.

[0023] Hydrogenation catalysts are preferably used supported on a carrier, as this allows for savings in the amount of metal used and increases the active surface area of ​​the catalyst. The amount of catalyst supported is typically 0.1 to 20% by weight relative to the carrier in terms of elemental composition.

[0024] The hydrogenation catalyst can be supported onto a carrier by known methods such as impregnation, precipitation, or gas-phase support.

[0025] Examples of supports for hydrogenation catalysts include carbon, polymers, metal oxides, metal sulfides, zeolites, clays, heteropoly acids, solid phosphoric acid, and hydroxyapatite.

[0026] Examples of carbon-based carriers include carbon, activated carbon, carbon black, and graphite.

[0027] As polymer-based carriers, styrene-based sulfonic acid type ion exchange resins and phenol-based sulfonic acid type ion exchange resins can be used. Examples include "DIAION" from Mitsubishi Chemical Corporation, "Levatit" from Lanxess, "Amberlite" and "Amberlist" from Rohm & Haas, and "DOWEX" from Dow.

[0028] Examples of metal oxide-based supports 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 include scandium oxide (Sc2O3), cerium oxide (CeO2), anatase titanium oxide (A-TiO2), rutile 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).

[0029] As zeolite carriers, zeolites that have been assigned a three-letter alphabetical structural code in the International Zeolite Association database can be used. Specifically, examples include zeolites that have been assigned structural codes such as LTA, FER, MWW, MFI, MOR, LTL, FAU, BEA, CHA, and CON.

[0030] Examples of clay-based carriers include kaolin, montmorillonite, bentonite, saponite, and acid clay.

[0031] [Hydrogenation process] In the hydrogenation step, where muconic acid is reacted with hydrogen to obtain the hydrogenation reaction product, the hydrogen may be added to the reactor all at once or sequentially.

[0032] 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 the partial pressure of hydrogen is undesirable from a safety standpoint for the equipment. Therefore, it is preferably 0.1 MPa to 10 MPa (gauge pressure), and more preferably 0.5 MPa to 3 MPa (gauge pressure).

[0033] The reaction can be carried out using any of the following reactor types: batch reactor, semi-batch reactor, continuous tank reactor, or tubular reactor. When using a solid catalyst supported on a carrier, the reaction can be carried out using any of the following methods: suspension bed, fixed bed, moving bed, or fluidized bed.

[0034] The reaction temperature is not particularly limited, but if it is too low the reaction rate will be slow, and if it is too high the reaction temperature will be high, which is undesirable. From this viewpoint, the reaction temperature is preferably 10 to 200°C, more preferably 30 to 150°C, and even more preferably 40 to 100°C.

[0035] The atmosphere in the reactor may contain inert gases such as nitrogen, helium, and argon in addition to hydrogen, but the oxygen concentration is preferably 5% by volume or less, more preferably 3% by volume or less, and even more preferably 0% by volume (i.e., reaction in the absence of oxygen) because these can lead to catalyst degradation and the generation of detonating gases.

[0036] The amount of muconic acid added to a mixed solvent of alcohol and water is not particularly limited, but a small amount is industrially undesirable. From this viewpoint, the amount of muconic acid added to 100 parts by weight of a mixed solvent of alcohol and water is preferably 1 part by weight or more, more preferably 5 parts by weight or more, and even more preferably 10 parts by weight or more.

[0037] In the present invention, the hydrogenation reaction product refers to a mixture of unreacted raw materials, reaction intermediates, by-products, adipic acid, a mixed solvent of alcohol and water, and a hydrogenation catalyst obtained after the hydrogenation step.

[0038] [Recovery of adipic acid] The adipic acid (carboxylic acid, carboxylate salt, carboxylic acid ester) contained in the hydrogenation reaction product can be recovered by conventional separation and purification operations such as filtration, concentration, and crystallization. When muconic acid carboxylic acid is used as a raw material, adipic acid carboxylic acid is produced; when muconic acid carboxylate is used as a raw material, adipic acid carboxylate is produced; and when muconic acid ester is used as a raw material, adipic acid monoester and adipic acid diester are produced. In this specification, adipic acid carboxylic acid, carboxylate salt, carboxylic acid ester, and mixtures thereof are collectively referred to as "adipic acid."

[0039] The adipic acid of the present invention is obtained by the method for producing adipic acid of the present invention. Conventional adipic acid production processes from fossil resources produce large amounts of nitrous oxide (N2O), which has a high greenhouse effect, as a by-product, whereas the method for producing adipic acid of the present invention does not produce nitrous oxide as a by-product. Therefore, the adipic acid of the present invention is an adipic acid with a low environmental impact.

[0040] [Alcohol recovery process] The present invention's method for producing adipic acid preferably includes an alcohol recovery step in which a mixture of alcohol and water is recovered from the hydrogenation reaction product obtained in the hydrogenation step. The method for recovering the mixture of alcohol and water from the hydrogenation reaction product is not particularly limited, but a general distillation method can be used. More specifically, the mixture can be recovered by evaporating alcohol and water in an evaporator to generate a mixed vapor of alcohol and water, which is then cooled and condensed in a condenser.

[0041] There are no particular restrictions on the pressure or temperature during evaporation; depending on the type of alcohol, evaporation can be performed at a pressure between 1 Pa and atmospheric pressure (normal pressure, approximately 101 kPa) and at a temperature between 20°C and 250°C.

[0042] Distillation methods such as simple distillation and multi-stage distillation can be used. Furthermore, the supply method for the hydrogenation reaction products used in alcohol recovery can be either a batch method or a continuous method.

[0043] The subsequent adipic acid crystallization step is preferably carried out in water from the viewpoint of adipic acid solubility. Therefore, the proportion of water in the evaporator can be increased by repeating the process of evaporating the alcohol and water mixture in an evaporator, adding water to the evaporator, and evaporating the alcohol and water mixture again. In this process, the alcohol and water mixture can be recovered on the evaporation side.

[0044] [Recycling Process] In the method for producing adipic acid of the present invention, it is preferable to include a recycling step in which the mixture of alcohol and water recovered in the alcohol recovery step is recycled to the hydrogenation step. By recycling the mixture of alcohol and water recovered in the alcohol recovery step to the hydrogenation step of muconic acid, the efficiency of alcohol utilization can be increased. The method for preparing the mixed solvent of alcohol and water used in the hydrogenation step of muconic acid from the mixture of alcohol and water recovered in the alcohol recovery step is not particularly limited, but water may be added as appropriate to lower the alcohol concentration, or the mixture may be subjected to distillation. Conversely, alcohol may be added as appropriate to increase the alcohol concentration, or the mixture may be subjected to distillation.

[0045] [Adipic acid production equipment] The present invention provides an adipic acid production apparatus comprising: a supply means (A) for supplying muconic acid, alcohol, water, a hydrogenation catalyst, and hydrogen to a hydrogenation reactor (B); a hydrogenation reactor (B); a means (C) for recovering adipic acid and a mixture of alcohol and water from the hydrogenation reaction products discharged from the hydrogenation reactor (B); and a means (D) for recycling the mixture of alcohol and water recovered by means (C) to the supply means (A).

[0046] The means (A) for supplying muconic acid, alcohol, water, hydrogenation catalyst, and hydrogen to the hydrogenation reactor (B) are not particularly limited as long as each substance can be supplied to the hydrogenation reactor, but refer to means for transferring each substance to the hydrogenation reactor (B) through piping using mechanical energy, gas pressure, self-gravity, etc. Specifically, examples include various pumps such as gear pumps and cylinder pumps, and the use of pressurized gases such as nitrogen and helium. The supply amount can be measured and controlled by a densimeter, flow meter, etc.

[0047] The hydrogenation reactor (B) is not particularly limited as long as it can hydrogenate muconic acid. Specifically, examples of reactors include batch reactors, semi-batch reactors, continuous tank reactors, and tubular reactors. The hydrogenation reactor (B) is equipped with a heater, various measuring instruments such as a pressure gauge and a thermometer, and a discharge mechanism for the hydrogenation reaction product. Batch reactors, semi-batch reactors, and continuous tank reactors are equipped with stirring means. In a tubular reactor, there is an inlet at one end for the raw materials to flow in, and the hydrogenation reaction product is discharged at the other end. In the reactor, the hydrogenation catalyst may be dispersed or fixed and packed in place.

[0048] The means (C) for recovering adipic acid and the alcohol-water mixture from the hydrogenation reaction product is not particularly limited as long as it can separate and purify the adipic acid and the alcohol-water mixture from the hydrogenation reaction mixture. Specifically, examples include means for separating the hydrogenation catalyst from the hydrogenation reaction product, means for separating the alcohol-water mixture, means for separating the adipic acid, and means for drying the separated adipic acid.

[0049] Examples of methods for separating the hydrogenation catalyst from the hydrogenation reaction product include filtration devices and centrifuges.

[0050] Examples of means for separating the alcohol-water mixture from the hydrogenation reaction product include evaporators and distillation apparatuses.

[0051] Examples of methods for separating adipic acid from hydrogenation reaction products include evaporators and crystallizers.

[0052] Examples of methods for drying the separated adipic acid include a dryer.

[0053] Means (D) for recycling the alcohol and water mixture recovered by means (C) to supply means (A) include means for transferring the alcohol and water mixture from the alcohol and water mixture recovery means to supply means (A), and evaporators, distillation apparatuses, mixing apparatuses, etc., to match the composition of the alcohol and water mixed solvent used in the hydrogenation process.

[0054] Figure 1 shows an example of an adipic acid production apparatus. In the adipic acid production apparatus of Figure 1, muconic acid, alcohol, water, a hydrogenation catalyst, and hydrogen 1 are supplied to the hydrogenation reactor (B) 3 using supply means (A) 2. From the hydrogenation reaction product obtained in the hydrogenation reactor (B), adipic acid 5 and a mixture of alcohol and water 6 are recovered using means (C) 4 for recovering adipic acid and a mixture of alcohol and water. The mixture of alcohol and water 6 is recycled to supply means (A) 2 using recycling means (D) 7.

[0055] Figure 2 shows another example of an adipic acid production apparatus. It is configured similarly to the adipic acid production apparatus shown in Figure 1, but in means (C) 4 for recovering adipic acid and a mixture of alcohol and water, the hydrogenation catalyst is separated using means 8 for separating the hydrogenation catalyst, the mixture of alcohol and water is separated using means 9 for separating the mixture of alcohol and water, the adipic acid is separated using means 10 for separating adipic acid, and the adipic acid is dried using means 11 for drying adipic acid to obtain adipic acid 5. If the mixture of alcohol and water is not completely separated by means 9 for separating the mixture of alcohol and water, the mixture of alcohol and water 6 can also be recovered by means 10 for separating adipic acid.

[0056] By recovering alcohol, the amount of waste alcohol can be reduced, thereby mitigating the environmental burden. In the adipic acid production apparatus of the present invention, a hydrogenation reaction can be carried out using a mixed solvent of alcohol and water, and the alcohol-water mixture can be recycled as a hydrogenation reaction solvent without increasing the alcohol content in the recovered alcohol-water mixture above 99% by mass. Therefore, in the adipic acid production apparatus of the present invention, alcohol can be recovered without using additional separation equipment such as permeation vaporization membrane separation when recovering alcohol.

[0057] [Method for producing polyamide] The present invention provides a method for producing polyamide, comprising the following steps (1) and (2). (1) Steps for producing adipic acid by the method for producing adipic acid of the present invention (2) A step of polymerizing the adipic acid obtained in step (1) with a diamine.

[0058] Step (1) is as described above.

[0059] Step (2) can be carried out, for example, by polymerizing adipic acid and a diamine by a known method (for example, the method described in section 3.2 on page 134 of "Polyamide Resin Handbook" edited by Osamu Fukumoto, Nikkan Kogyo Shimbun (January 1988)). The diamine is not particularly limited as long as it is a compound having amino groups at both ends, but 1,4-butanediamine, 1,5-pentanediamine, and hexamethylenediamine can be preferably used.

[0060] [Various derivatization] The adipic acid obtained in this invention can be converted to an adipic acid diester by further esterification. The esterification method is not particularly limited, but examples include esterification reactions using an acid catalyst and an alcohol solvent. The acid catalyst used here is not particularly limited, but examples include mineral acids such as sulfuric acid and hydrochloric acid, and solid acids such as silica and strongly 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 a boron trifluoride methanol complex, a production method using a metal alkoxide under basic conditions, and a method using an alkylating reagent such as diazomethane or alkyl halide.

[0061] Adiponitrile can be produced from the adipic acid obtained in the present invention by a known method (for example, the method described in Example 1 of U.S. Patent No. 3,661,973). Hexamethylenediamine can be produced by hydrogenating the obtained adiponitrile by a known method (for example, the method described in Example 1 of U.S. Patent No. 3,758,584). In the polyamide production method of the present invention, hexamethylenediamine derived from the adipic acid produced in the present invention can also be used as the hexamethylenediamine. [Examples]

[0062] 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. Adipic acid yield (%) = Amount of adipic acid produced (mol) / Raw material supplied (mol) × 100.

[0063] The aqueous solution concentrate of the reaction solution was analyzed by high-performance liquid chromatography (HPLC). The product was quantified using an absolute calibration curve prepared with standard samples.

[0064] (Comparative Example 1) Production of adipic acid 8.8 g of cis,cis-muconic acid (manufactured by Sigma-Aldrich), 80 g of ethanol (manufactured by Fujifilm Wako Co., Ltd.; 99.4% by mass of ethanol / 0.6% by mass of water), and 0.035 g of Pd / C (STD type, manufactured by Fujifilm Wako Co., Ltd., water content 50 wt%) were added to a 0.2 L glass inner cylinder (manufactured by Taikaku Glass Industry Co., Ltd.). The glass inner cylinder was placed in a stainless steel autoclave (manufactured by Taikaku Glass Industry Co., Ltd.) and sealed. While stirring at 300 rpm using a single-stage stirring blade, the autoclave was purged with nitrogen, and then hydrogen gas was added to adjust the hydrogen partial pressure inside the autoclave to 0.9 MPa. Subsequently, the temperature inside the autoclave was raised to 80°C. After maintaining the temperature at 80°C for 3 hours, it was allowed to cool to room temperature, the gas inside the autoclave was released to return to atmospheric pressure, and the reaction solution was collected. Pd / C was removed by filtration, and the filtrate was concentrated using a rotary evaporator (manufactured by Tokyo Rikakikai Co., Ltd.) to obtain a concentrate. A 1 g / L aqueous solution of the concentrate was analyzed by HPLC, and the amount of adipic acid produced was measured to calculate the adipic acid yield. The results are shown in Table 1.

[0065] (Comparative Example 2) Production of adipic acid The reaction was carried out in the same manner as in Example 1, except that ultrapure water was used instead of ethanol. The results are shown in Table 1.

[0066] (Example 1) Production of adipic acid The reaction was carried out in the same manner as in Comparative Example 1, except that a mixed solvent of ethanol and water (95% by mass of ethanol / 5% by mass of water) was used instead of ethanol. The results are shown in Table 1.

[0067] (Example 2) Production of adipic acid The reaction was carried out in the same manner as in Comparative Example 1, except that a mixed solvent of ethanol and water (90% by mass of ethanol / 10% by mass of water) was used instead of ethanol. The results are shown in Table 1.

[0068] (Example 3) Production of adipic acid The reaction was carried out in the same manner as in Comparative Example 1, except that a mixed solvent of ethanol and water (80% by mass of ethanol / 20% by mass of water) was used instead of ethanol. The results are shown in Table 1.

[0069] (Example 4) Production of adipic acid The reaction was carried out in the same manner as in Comparative Example 1, except that a mixed solvent of ethanol and water (70% by mass of ethanol / 30% by mass of water) was used instead of ethanol. The results are shown in Table 1.

[0070] (Example 5) Production of adipic acid The reaction was carried out in the same manner as in Example 3, except that 16.3 g of cis,cis-muconic acid (manufactured by Sigma-Aldrich) and 0.070 g of Pd / C (STD type, manufactured by Fujifilm Wako Co., Ltd., water content 50 wt%) were used, and the stirring speed was 600 ppm. The results are shown in Table 1.

[0071] (Example 6) Production of adipic acid The reaction was carried out in the same manner as in Example 5, except that 24.4 g of cis,cis-muconic acid (manufactured by Sigma-Aldrich) and 0.105 g of Pd / C (STD type, manufactured by Fujifilm Wako Co., Ltd., water content 50 wt%) were used, and a two-stage stirring blade was employed. The results are shown in Table 1.

[0072] [Table 1]

[0073] Comparative Example 1 shows that adipic acid can be produced in high yield when alcohol is used as the solvent, but complex separation operations such as permeation vaporization membrane separation are required for alcohol recycling. Furthermore, Comparative Example 2 revealed that adipic acid is difficult to produce when water is used as the solvent.

[0074] On the other hand, Examples 1 to 6 demonstrated that adipic acid can be produced in high yield by using a mixed solvent of alcohol and water that can be recovered by a general distillation method. Similarly, Examples 1 to 6 demonstrated that adipic acid can be produced in high yield from high-concentration muconic acid even when using a mixed solvent of alcohol and water. [Explanation of symbols]

[0075] 1. Muconic acid, alcohol, water, hydrogenation catalyst, and hydrogen 2 Supply means (A) 3. Hydrogenation reactor (B) 4. Means for recovering a mixture of adipic acid, alcohol, and water (C) 5. Adipic acid 6. A mixture of alcohol and water 7. Means (D) for recycling the mixture of alcohol and water into supply means (A). 8. Means for separating the hydrogenation catalyst 9. Means for separating a mixture of alcohol and water. 10. Means for separating adipic acid 11. Means for drying adipic acid

Claims

1. An apparatus for producing adipic acid, comprising: a supply means (A) for supplying muconic acid, alcohol, water, a hydrogenation catalyst, and hydrogen to a hydrogenation reactor (B); a hydrogenation reactor (B); a means (C) for recovering adipic acid and a mixture of alcohol and water from the hydrogenation reaction products discharged from the hydrogenation reactor (B); and a means (D) for recycling the mixture of alcohol and water recovered by means (C) to the supply means (A).

2. A method for producing adipic acid, comprising a hydrogenation step of reacting muconic acid with hydrogen in a mixed solvent of alcohol and water in the presence of a hydrogenation catalyst to obtain a hydrogenation reaction product.

3. The method for producing adipic acid according to claim 2, wherein the alcohol is one or more alcohols selected from the group consisting of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, and tert-butanol.

4. The method for producing adipic acid according to claim 2 or 3, wherein the alcohol content in the mixed solvent is 70% by mass or more and 95% by mass or less.

5. A method for producing adipic acid according to any one of claims 2 to 4, comprising an alcohol recovery step of recovering a mixture of alcohol and water from the hydrogenation reaction product obtained in the hydrogenation step.

6. A method for producing adipic acid according to claim 5, comprising a recycling step of recycling the mixture of alcohol and water recovered in the alcohol recovery step to a hydrogenation step.

7. Adipic acid obtained by the method for producing adipic acid according to any one of claims 2 to 6.

8. A method for producing polyamide comprising the following steps (1) and (2). (1) A step of producing adipic acid by the method for producing adipic acid described in any one of claims 2 to 6. (2) A step of polymerizing the adipic acid obtained in step (1) with a diamine.

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