Production method of 2,5-furandicarboxylic acid

Abstract

To provide a method of producing FDCA by an oxidation of HMF, capable of reducing a residual ratio of an intermediate product and obtaining the FDCA at a high production rate.SOLUTION: A method of producing 2,5-furandicarboxylic acid includes an oxidation process of selectively oxidizing a hydroxy group and a formyl group included in 5-hydroxymethylfurfural under a presence of two or more kinds of metal catalyst. As the metal catalyst, platinum and palladium are included. Thus, through combining the prescribed two or more kinds of metal catalyst, a residual ratio of an intermediate product such as DFF, HMFCA and FFCA can be reduced to obtain the FDCA at a high production rate.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing 2,5-furandicarboxylic acid (hereinafter referred to as "FDCA") from 5-hydroxymethylfurfural (hereinafter referred to as "HMF"). [Background technology]

[0002] In recent years, in order to achieve a carbon-neutral society, high-performance bioplastics such as polyethylene furanoate (PEF) have been attracting attention as an alternative polymer to polyethylene terephthalate (PET), a petroleum product. PEF is a polymer produced by polycondensation or ring-opening polymerization of FDCA and ethylene glycol. FDCA, which is used as a raw material for PEF, can be produced by oxidizing HMF, which can be derived from cellulose, for example. However, there are only a limited number of catalysts that can convert the hydroxyl and formyl groups of HMF with high selectivity. Therefore, there has been active research into catalysts that can selectively oxidize the hydroxyl and formyl groups of HMF.

[0003] For example, Patent Document 1 discloses a method for producing FDCA by oxidizing HMF in the presence of a precious metal-containing activated carbon-supported metal catalyst, water, and oxygen. Patent Document 1 also describes the use of platinum as the precious metal.

[0004] Patent Document 2 discloses a method for producing FDCA from HMF, which comprises the steps of oxidizing HMF in an alkaline aqueous solution containing caustic alkali to produce FDCA and its intermediate, and adding a chlorine-based oxidizing agent to the aqueous solution after the oxidation and oxidizing the intermediate to produce FDCA. Patent Document 2 describes an example in which the method for oxidizing HMF is air oxidation using a precious metal catalyst, and uses a palladium-supported carbon catalyst as the precious metal catalyst.

[0005] Furthermore, Patent Document 3 discloses a method for producing FDCA, which includes carboxylating a furan-based compound or a derivative thereof containing a hydroxyl group and a carbonyl group in the presence of a catalyst containing noble metal nanoparticles in a support having a spinel structure. Patent Document 3 describes HMF as an example of the furan-based compound, MnCo2O4 as an example of the support having a spinel structure, and ruthenium as an example of the noble metal.

[0006] Thus, when producing FDCA by oxidizing the hydroxyl and formyl groups of HMF, it has been common to use one type of metal catalyst alone. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2015-83559 A [Patent Document 2] JP 2009-29751 A [Patent Document 3] Special Publication No. 2019-513538 Summary of the Invention [Problem to be solved by the invention]

[0008] However, when only one type of metal catalyst is used for the oxidation of HMF as in Patent Documents 1 to 3, a large amount of intermediates produced during the production of FDCA from HMF remains, resulting in a low production ratio of FDCA.

[0009] Therefore, an object of the present invention is to reduce the residual rate of intermediates and obtain FDCA at a high production rate in a method for producing FDCA by oxidation of HMF. [Means for solving the problem]

[0010] For this purpose, the technology disclosed in this specification is a method for producing 2,5-furandicarboxylic acid, which includes an oxidation step of selectively oxidizing the hydroxyl groups and formyl groups of 5-hydroxymethylfurfural in the presence of two or more metal catalysts, the metal catalysts including platinum and palladium.

[0011] Here, the metal catalyst used in combination with platinum and palladium in the oxidation step preferably contains one or more transition metals (excluding platinum and palladium). In this case, the transition metal may be one or more metal elements selected from the group consisting of ruthenium, chromium, gold, silver, copper, iron, nickel and cobalt. In the oxidation step, the total amount of the metal catalyst may be 0.01 mol to 0.1 mol per 1 mol of 5-hydroxymethylfurfural. The metal catalyst may also include a platinum catalyst in which platinum is supported on a carbon support, and a palladium catalyst in which palladium is supported on a carbon support. The metal catalyst may include a transition metal catalyst in which the transition metal is supported on a carbon support. Effect of the Invention

[0012] According to the present invention, in the method for producing FDCA by oxidation of HMF, a combination of two or more specific metal catalysts is used, thereby reducing the residual rate of intermediates and enabling FDCA to be produced at a high production rate. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 shows the structures of the raw materials, intermediates, and target products in the production of FDCA using HMF as a raw material. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0015] [FDCA manufacturing method] The method for producing FDCA according to the present invention includes an oxidation step of selectively oxidizing the hydroxyl and formyl groups of HMF in the presence of two or more metal catalysts, which in the present invention include at least two metal catalysts, platinum (Pt) and palladium (Pd).

[0016] Here, the process of producing FDCA using HMF will be described with reference to Figure 1. Figure 1 shows the structures of the raw materials, intermediates and target product in the production of FDCA using HMF as the raw material.

[0017] (HMF) The raw material HMF is a furan compound having one hydroxyl group and one formyl group. HMF can be synthesized using sugars such as glucose as raw materials. The sugars used as raw materials for HMF may be natural or synthetic, or may be a mixture of these. Specifically, the raw sugars may be selected from monosaccharides, disaccharides, and polysaccharides. These sugars may be used alone or in combination of two or more. Furthermore, sugars (aldohexoses) that can be produced from pulp, rice husks, etc. may be used as raw sugars for HMF. Pulp and rice husks are easily available, so the supply of raw materials is stable, and HMF can be synthesized efficiently and at low cost. As a result, the production efficiency and cost reduction of FDCA can be achieved.

[0018] (Reaction steps in the oxidation process) As shown in Figure 1, three types of intermediates are generated in the process of oxidizing HMF to produce FDCA. The intermediates are 2,5-diformylfuran (hereinafter referred to as "DFF"), 5-(hydroxymethyl)furan-2-carboxylic acid (hereinafter referred to as "HMFCA"), and 5-formyl-2-furan carboxylic acid (FFCA). HMF has one hydroxyl group and one formyl group, and FDCA is generated when both of the two functional groups of HMF are oxidized to carboxyl groups (carboxylic acids), such as hydroxyl group → formyl group → carboxyl group (alcohol → aldehyde → carboxylic acid) or formyl group → carboxyl group (aldehyde → carboxylic acid). In other words, the process of producing FDCA from HMF goes through multiple reaction steps, such as the oxidation reaction of HMF → DFF, the oxidation reaction of HMF → HMFCA, the oxidation reaction of DFF → FFCA, the oxidation reaction of HMFCA → FFCA, and the oxidation reaction of FFCA → FDCA.

[0019] (Metal component of metal catalyst) The inventors of the present invention have come to the following conclusion while investigating the optimum catalyst for the oxidation reaction of HMF. Since the most effective catalysts are different for each of the above-mentioned reaction steps, when one type of metal catalyst (Pt, Pd, Ru, etc.) is used alone, it is possible that the catalytic effect, i.e., the effect of accelerating the reaction rate, is likely to be exhibited in a specific reaction step, but the reaction acceleration effect is low in other reaction steps. As a result, it is considered that the production ratio of intermediates such as DFF, HMFCA, and FFCA will be high, and the production ratio of FDCA will be low. For example, the inventors of the present invention speculate that when only a Pt catalyst is used, the oxidation reaction proceeds quickly in the reaction step from HMF to DFF, but the effect of accelerating the oxidation reaction in the subsequent reaction steps from DFF to FFCA and FFCA to FDCA will not be very great.

[0020] Therefore, in the method for producing FDCA according to the present invention, in the oxidation step for selectively oxidizing the hydroxyl group and formyl group of HMF, two or more specific metal catalysts are used in combination to obtain a sufficient acceleration effect of the oxidation reaction in all reaction steps from HMF to FDCA. Specifically, in the oxidation step, by using two or more metal catalysts containing at least Pt and Pd as metal components in combination, it is considered that the oxidation reaction in reaction steps other than the reaction step from HMF to DFF (for example, the reaction step from DFF to FFCA and the reaction step from FFCA to FDCA) can be accelerated, unlike the case where a Pt catalyst is used alone. This reduces the residual rate of the intermediates DFF, HMFCA, and FFCA, and allows FDCA to be produced at a high production ratio. Combining multiple catalysts is not usually considered, as there is a risk that the effects of other catalysts may be offset.

[0021] Here, in order to produce FDCA at a higher production ratio, it is preferable that the metal catalyst (hereinafter referred to as "co-catalyst") used in combination with Pt and Pd in ​​the oxidation step contains one or more transition metals (excluding Pt and Pd). As the co-catalyst, for example, transition metals of groups 8, 9, 10 and 11 (hereinafter referred to as "late transition metals"), as well as chromium (Cr), manganese (Mn) and the like may be used. Among these transition metals, the co-catalyst is preferably one or more metal elements selected from the group consisting of Ru, Cr, Au, Ag, Cu, Fe, Ni and Co, and particularly preferably Ru. By using these co-catalysts, the oxidation reaction in the reaction stages of HMF→HMFCA, DFF→FFCA, HMFCA→FFCA and FFCA→FDCA can be dramatically accelerated by the synergistic effect with the catalytic effect of Pd. For example, the present inventors speculate that the use of a Ru catalyst together with a Pt catalyst and a Pd catalyst is particularly effective in accelerating the oxidation reaction in reaction steps such as DFF→FFCA and FFCA→FDCA.

[0022] (Metal catalyst carrier) As the metal catalyst of the present invention, a metal catalyst in which a metal component is supported on a carrier is used. The carrier is used to improve the dispersibility of the metal component and improve the reaction activity, but it is also considered to have the effect of promoting the oxidation reaction by interacting with the reaction substrate. The carrier usable for the metal catalyst of the present invention is not particularly limited, but examples thereof include activated carbon (carbon), zeolite, silica, alumina, titania, zirconia, diatomaceous earth, other metal oxides, and porous bodies. From the viewpoint of increasing the effect of accelerating the oxidation reaction from HMF to FDCA, it is preferable to use activated carbon as a carrier. The form of the activated carbon is not particularly limited, and may be powder, granular, fibrous, cylindrical, honeycomb, etc., but from the viewpoint of improving the workability during catalyst preparation and the dispersibility in the reaction solution, powder and granular are preferable.

[0023] (Shape and size of metal catalyst) The metal components and carriers of the metal catalyst of the present invention are as described above, and the preferred metal catalyst of the present invention is a combination of a Pt / C catalyst in which Pt is supported on a carbon carrier and a Pd / C catalyst in which Pd is supported on a carbon carrier. The shape of the metal catalyst of the present invention is not particularly limited, but from the viewpoint of improving the workability during catalyst preparation and the dispersibility in the reaction solution, and accelerating the oxidation reaction in the case of flow synthesis to increase the production ratio of FDCA, the shape of the Pt / C catalyst and the Pd / C catalyst is preferably bead-shaped (particulate). In this case, the particle diameter of the bead-shaped Pt / C catalyst and the Pd / C catalyst is preferably 100 μm to 500 μm, more preferably 100 μm to 400 μm, and even more preferably 200 μm to 300 μm.

[0024] Furthermore, when a co-catalyst is used as the third metal catalyst, it is preferable that the catalyst contains a transition metal catalyst in which the transition metal is supported on a carbon support. In this case, the transition metal catalyst is preferably in a powder form from the viewpoints of improving workability during catalyst preparation and dispersibility in the reaction solution, as well as accelerating the oxidation reaction to increase the production ratio of FDCA.

[0025] (Amount of metal catalyst used) In the oxidation step of the FDCA production method of the present invention, the amount of metal catalyst used is not particularly limited, but from the viewpoint of increasing the production ratio of FDCA while also taking into consideration economic efficiency, the total amount of metal catalyst per mol of HMF is preferably 0.01 mol to 0.1 mol, more preferably 0.01 mol to 0.08 mol, and even more preferably 0.01 mol to 0.05 mol.

[0026] (Ratio of each metal catalyst) The amount of the platinum catalyst used is preferably 20 mol % to 40 mol %, and more preferably 30 mol % to 40 mol %, when the total amount of the metal catalysts is taken as 100 mol %. The amount of the palladium catalyst used is preferably 20 mol % to 40 mol %, and more preferably 30 mol % to 40 mol %, when the total amount of the metal catalyst is taken as 100 mol %. The amount of the co-catalyst used is preferably 40 mol % or less (more than 0 mol %), and more preferably 20 mol % to 40 mol %, when the total amount of the metal catalyst is taken as 100 mol %. By using each catalyst in the above ratio range, the production ratio of FDCA can be increased and economic efficiency is also improved.

[0027] (Method of preparing metal catalyst) The metal catalyst of the present invention can be prepared by a known method. For example, the above-mentioned precursors of Pt, Pd, other metals, etc., and precursors of other metal components as necessary are adsorbed on a carrier such as activated carbon or Si, and then a reduction treatment is performed to obtain the metal catalyst of the present invention. In addition, a commercially available product may be used as the metal catalyst of the present invention. Examples of commercially available products include those described in the examples below.

[0028] Methods for adsorbing metal components onto a support include known methods such as impregnation, deposition precipitation, ion exchange, and equilibrium adsorption. The impregnation method involves immersing a support in a solution of a precursor of the metal component, and then removing the solvent. The deposition precipitation method involves preparing an aqueous solution of the precursor of the metal component and the metal salts that are the raw materials for the metal oxide support, and adding this to an alkaline aqueous solution to precipitate hydroxides or carbonates. The ion exchange method involves transferring metal cations or complex anions to hydroxyl groups on the surface or H groups on the surface of the support that have ion exchange capacity. + , O.H. - The equilibrium adsorption method is a method in which a support is immersed in an aqueous solution of a precursor of a metal component, and then the metal component that is not adsorbed on the surface of the support is removed by filtration.

[0029] After the metal component is adsorbed on the carrier as described above, the carrier may be washed with water, dried and calcined as necessary, and then reduced to prepare a metal catalyst. The drying and calcination temperatures may be appropriately set based on known conditions. The reduction may be performed by either a liquid phase reduction method or a gas phase reduction method, and the temperature and time of the reduction may be appropriately set based on known conditions. Each metal component may be supported individually on a carrier, or a plurality of metal components may be supported simultaneously on a single carrier.

[0030] (Reaction solution) In the method for producing FDCA of the present invention, a reaction solution is prepared by dissolving the raw material HMF in an aqueous solvent. The aqueous solvent is not particularly limited as long as it contains at least water and can dissolve HMF, but from the viewpoint of production efficiency and economics, it is preferable to use a polar solvent. In addition to water, examples of the polar solvent include aprotic organic solvents and ionic liquids having polarity, with water being particularly preferable. Examples of the aprotic organic solvent include dimethyl sulfoxide, dimethylacetamide, N,N-dimethylformamide, cyclohexanone, ethyl acetate, and dichloromethane. Examples of the ionic liquid include imidazolium salts and pyridinium salts.

[0031] From the viewpoints of improving the solubility of the product and the yield of FDCA while preventing leaching of the catalyst (elution of metals such as Pt and Pd), the concentration of HMF in the reaction solution is preferably 0.050 M or more and 10 M or less, more preferably 0.10 M or more and 5.0 M or less, and even more preferably 0.20 M or more and 2.5 M or less, relative to the total amount of the reaction solution. In addition to the raw material HMF, a base such as potassium carbonate (K2CO3), sodium carbonate (Na2CO3), potassium hydroxide (KOH), or sodium hydroxide (NaOH) may be added to the reaction solution in order to convert the carboxylic acid of FDCA into a potassium salt to increase water solubility and prevent FDCA from precipitating in the reaction solution.

[0032] (oxygen) The oxygen used in the oxidation step of the present invention is not particularly limited, and may be, for example, oxygen gas, air, or a gas obtained by diluting air with an inert gas such as nitrogen or argon to a predetermined oxygen concentration, and may be supplied to the reaction system. Any method may be used for supplying oxygen to the reaction system at a predetermined pressure and flow rate. The pressure of oxygen during the reaction may be controlled, for example, by adjusting a back pressure regulator (BPR) connected to the reactor (in the case of flow synthesis) or by adjusting the pressure inside the autoclave (in the case of batch synthesis). The flow rate of oxygen may be controlled by a mass flow controller connected to an oxygen cylinder or a mixer of oxygen and other gases. The oxygen concentration may be controlled by mixing air and an inert gas for dilution with a known mixer.

[0033] (Synthesis method) The method for synthesizing FDCA of the present invention is not particularly limited, and may be either flow synthesis or batch synthesis. Flow synthesis is a synthesis method in which an oxidation reaction is carried out while continuously supplying the raw materials HMF and oxygen to a reactor. As the reactor, for example, a column reactor in which a metal catalyst is packed in a column can be used. In addition, the reaction solution after the oxidation reaction may be collected all at once after the reaction is completed, or may be collected continuously while the oxidation reaction is being carried out.

[0034] Batch synthesis is a synthesis method in which the reaction solution in which the raw material HMF is dissolved and the catalyst are all charged in advance into a reactor, and oxygen is passed through the reaction solution in the reactor to carry out the oxidation reaction. For example, an autoclave can be used as the reactor. The reaction solution after the oxidation reaction is collected all at once after the reaction is completed. Batch synthesis is suitable for synthesizing products with complex structures, but it is difficult to control the reaction and productivity, and the energy efficiency tends to be low. On the other hand, flow synthesis can improve energy efficiency because it is possible to control the reaction time and productivity by changing the supply rate of the raw materials. Thus, flow synthesis is more energy efficient than batch synthesis and also reduces waste emissions, so flow synthesis is considered to be preferable industrially from the viewpoints of energy saving and productivity.

[0035] (Reaction temperature) The temperature of the oxidation reaction in the oxidation step is preferably 80°C or higher and 160°C or lower, more preferably 90°C or higher and 140°C or lower, and even more preferably 100°C or higher and 120°C or lower, from the viewpoints of suppressing the decomposition of HMF, increasing the production ratio of FDCA, and accelerating the reaction rate.

[0036] (Reaction time) In the oxidation step, the time for the oxidation reaction is, for example, preferably 8 to 20 hours in the case of batch synthesis, more preferably 10 to 18 hours, and even more preferably 12 to 16 hours, from the viewpoint of increasing the production ratio of FDCA and preventing leaching of the catalyst. In the case of flow synthesis, the production ratio of FDCA can be increased even in a shorter reaction time. For example, depending on the reaction conditions, it is possible to complete the reaction of oxidizing HMF to FDCA in about several minutes to several tens of minutes.

[0037] (Reaction pressure) From the viewpoint of increasing the production ratio of FDCA and improving productivity, the pressure during the oxidation reaction in the oxidation step is preferably 0.2 MPa or more and 1.5 MPa or less, more preferably 0.3 MPa or more and 1.4 MPa or less, and even more preferably 0.4 MPa or more and 1.3 MPa or less. The pressure during the reaction may be, for example, the indicated pressure of a plunger pump that sends a reaction solution to the reactor by connecting a BPR to the reactor.

[0038] (oxygen supply) From the viewpoint of increasing the production ratio of FDCA and improving the yield, the amount of oxygen supplied in the oxidation step is preferably 8 to 17 equivalents relative to the amount of HMF charged, more preferably 9 to 16 equivalents, and even more preferably 10 to 15 equivalents. Note that, in the method for producing FDCA of the present invention, 1 equivalent of oxygen means the amount (mol) of oxygen supplied per 1 mol of HMF, which is the raw material.

[0039] (Method of identification of FDCA) FDCA can be identified by 1H-NMR (Nuclear Magnetic Resonance) and 13C-NMR. NMR measurements can be performed, for example, using deuterated dimethyl sulfoxide (DMSO) as a measurement solvent and a JEOL ECS-400 (400 MHz (1H-NMR), 10 MHz (13C-NMR)) as a measurement instrument.

[0040] (FDCA production ratio) The production ratio of FDCA can be determined by analyzing the reaction solution after the oxidation reaction by high performance liquid chromatography (HPLC) or a mass spectrometer, and calculating the peak area ratios of the raw material HMF, the intermediate (a mixture of DFF, HMFCA, and FFCA), and the target product FDCA from the HPLC chart. The HPLC analysis can be performed, for example, as follows.

[0041] As a column, for example, COSMOSIL Packed Column 5C18-MS-II (4.6 ID×150 mm, Code: 38019-81) manufactured by Nacalai Tesque can be used. The column temperature may be, for example, room temperature. As the mobile phase, for example, a mixed solution of 5 mM aqueous sulfuric acid (liquid A) and acetonitrile (liquid B) can be used. For example, the flow rate of the measurement solution may be 1 mL / min, and the measurement wavelength may be 280 nm (the maximum absorption wavelength of FDCA detected by a photodetector (Photodiode Array)).

[0042] Furthermore, gradient analysis may be used. In this case, for example, the ratio of solution A to solution B in the mobile phase may be changed as follows: 0 to 2 minutes: The concentration ratio of solutions A and B is 95% solution A:5% solution B. 2 minutes to 12 minutes: The concentration ratio of solutions A and B is changed linearly over time from 95% solution A:5% solution B to 88% solution A:12% solution B (linear gradient). 12 to 20 minutes: The concentration ratio of solutions A and B is 70% A:30% B. 20 to 25 minutes: The concentration ratio of solutions A and B is 95% solution A:5% solution B.

[0043] In addition to confirming the purity of FDCA in the above gradient analysis, in order to confirm the absence of impurities, it is desirable to confirm that no other peaks exist in the range of 0% to 100% of solution B.

[0044] In addition, when performing HPLC analysis, by connecting a mass spectrometer to the HPLC measurement equipment, it is possible to identify FDCA and measure the production ratio at the same time.

[0045] In the present invention, when the FDCA production ratio (peak area ratio on the HPLC chart) measured in this manner is 70% or more, it is determined that the FDCA production ratio is high and the object of the present invention is achieved, and when it is 80% or more, it is determined that the effects of the present invention are excellent.

[0046] (Isolation and purification of FDCA) FDCA synthesized by oxidation of HMF is dissolved in the reaction solution in an alkaline environment. Therefore, in order to use FDCA as a raw material for PEF, etc., it is necessary to isolate FDCA from the reaction solution. In order to isolate FDCA, an acid is added to the reaction solution to create an acidic environment, and the FDCA dissolved in the reaction solution crystallizes and precipitates. The precipitated FDCA is collected, for example, by filtration, to obtain solid FDCA. When creating an acidic environment in the reaction solution, the reaction solution may be concentrated under reduced pressure and an acid may be added to the concentrated solution. The acid added to create an acidic environment in the reaction solution is not particularly limited, and examples of the acid that can be used include hydrochloric acid (HCl) and sulfuric acid (H2SO4). The collected FDCA may be purified to improve its purity. For example, the FDCA can be purified by washing, recrystallization, drying, and, if necessary, decolorization.

[0047] [Uses of FDCA] The use of FDCA produced by the production method of the present invention is not particularly limited, but it can be suitably used, for example, as a raw material for producing PEF.

[0048] In addition, although various modified examples have been described above, these modified examples may be combined together to form a configuration. In addition, the present disclosure is not limited to the above-described embodiment, and may be embodied in various forms without departing from the gist of the present disclosure. EXAMPLES

[0049] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0050] [Catalyst preparation] (Pt / C catalyst) "Pt / C, Beads (Pt 5%)" (Pt / C catalyst with a Pt content of 5% by mass) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. was used.

[0051] (Pd / C catalyst) "Pd / C, Beads (Pd 5%)" (Pd / C catalyst with a Pd content of 5% by mass) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. was used.

[0052] (Ru / C catalyst) We used "Ruthenium 5% on Carbon (wetted with ca. 50% Water)" (Ru / C catalyst with Ru content of 5% by mass) manufactured by Tokyo Chemical Industry Co., Ltd. (Cas No. 7440-18-8).

[0053] [Synthesis of FDCA] FDCA was synthesized by oxidizing HMF as follows: After the oxidation reaction, the reaction solution was analyzed by HPLC to calculate the peak area ratios of the raw material HMF, the intermediate (a mixture of DFF, HMFCA, and FFCA), and the target product FDCA, and the production ratios of HMF, the intermediate, and FDCA were obtained.

[0054] Example 1 In Example 1, flow synthesis of FDCA was performed by oxidizing HMF using a ternary catalyst consisting of a mixture of particulate Pt / C catalyst (particle size: 200 μm), particulate Pd / C catalyst (particle size: 200 μm), and powdered Ru / C catalyst. Specifically, first, the raw materials HMF and 1 equivalent of potassium carbonate relative to HMF were added to distilled water, and the mixture was diluted with water so that the concentration of HMF became 0.1 M to prepare a reaction solution. A column (column reactor) with an inner diameter of 4 mm and a length of 5 cm was used as the reactor, and three types of metal catalysts were packed in the column reactor so that the molar ratio of Pt / C catalyst:Pd / C catalyst:Ru / C catalyst was 1:1:1. The total amount of metal catalysts packed was 420 mg (0.16 mmol). The amount of each metal catalyst packed was 111.1 mg (0.052 mmol) of Pd / C catalyst, 203.9 mg (0.052 mmol) of Pt / C catalyst, and 104.3 mg (0.052 mmol) of Ru / C catalyst.

[0055] Next, the reaction solution was continuously pumped into a column reactor filled with a metal catalyst using a plunger pump, and 12 equivalents of oxygen were continuously supplied to the raw material HMF, to carry out the oxidation reaction of HMF. The flow rate of the reaction solution was adjusted to 0.10 mL / min. The flow rate of oxygen was adjusted to 1.2 mL / min using a mass flow controller. The reaction temperature was kept at 100°C by heating the column reactor. The pressure during the reaction was 0.3 MPa, as confirmed by connecting a 20 psi (0.14 MPa) BPR to the column reactor and checking the indicated pressure of the plunger pump. The residence time in the oxidation reaction was 3.1 minutes, and the reaction time was 10 minutes. That is, the reaction solution that flowed out was collected for 10 minutes.

[0056] The reaction solution after the oxidation reaction was analyzed by HPLC, and the production ratio of HMF was 0, the production ratio of intermediates was 11%, and the production ratio of FDCA was 89%. That is, in Example 1, FDCA was obtained as the main product. The type and amount of the metal catalyst in Example 1, and the production ratio of each compound are shown in Table 1 below.

[0057] (Example 2, Comparative Examples 1 to 5) In Example 2 and Comparative Examples 1 to 5, in order to confirm the difference in the production ratio of FDCA depending on the number and combination of metal catalysts, batch synthesis of FDCA was performed by oxidizing HMF using one or more metal catalysts selected from Pt / C catalyst, Pd / C catalyst, and Ru / C catalyst. All of the metal catalysts used were in powder form. Specifically, the air in a 15 mL screw-cap test tube was first replaced with nitrogen and then with oxygen. Next, 0.5 mmol (63 mg) of HMF, 1 equivalent of potassium carbonate (0.5 mmol, 69 mg) relative to HMF, 1.0 mL of distilled water, and a predetermined amount of each metal catalyst were added to the screw-cap test tube whose inside had been replaced with oxygen to prepare a reaction solution.

[0058] The amount of each metal catalyst added was 40 mg (2 mol%) of Pt / C catalyst, 20 mg (2 mol%) of Pd / C catalyst, and 20 mg (2 mol%) of Ru / C catalyst in Example 2. In Comparative Example 1, the amount of Pt / C catalyst was 100 mg (5 mol%). In Comparative Example 2, the amount of Pd / C catalyst was 50 mg (5 mol%). In Comparative Example 3, the amount of Pt / C catalyst was 50 mg (5 mol%). In Comparative Example 4, the amount of Pt / C catalyst was 40 mg (2 mol%) and the amount of Ru / C catalyst was 20 mg (2 mol%). In Comparative Example 5, the amount of Pd / C catalyst was 20 mg (2 mol%) and the amount of Ru / C catalyst was 20 mg (2 mol%).

[0059] Next, the screw-cap test tube was capped with a septum, and a balloon filled with oxygen gas was attached to the screw-cap test tube. The oxygen gas pressure in the balloon was 1 atm. The screw-cap test tube was then placed in an oil bath, and the oxidation reaction of HMF was carried out at 100°C for 15 hours.

[0060] The reaction solution after the oxidation reaction was filtered through Celite, and a portion was collected and analyzed by HPLC. The types and amounts of metal catalysts in Example 2 and Comparative Examples 1 to 5, as well as the production ratios of each compound, are shown in Table 1 below. As shown in Table 1, in Example 2, which contained at least Pt and Pd as metal catalysts and Ru as a promoter, the production ratio of FDCA was very high at 94%, whereas in Comparative Examples 1 to 3, which contained only one type of metal catalyst, and Comparative Examples 4 and 5, which contained two or more types of metal catalysts but did not contain either Pt or Pd, the production ratio of FDCA was low at less than 70%.

[0061] (Examples 3 to 8) In Examples 3 to 8, in order to confirm the difference in the production ratio of FDCA depending on the ratio of each metal catalyst, batch synthesis of FDCA was performed by oxidizing HMF using three types of metal catalysts, Pt / C catalyst, Pd / C catalyst, and Ru / C catalyst. All of the metal catalysts used were in powder form.

[0062] A reaction solution was prepared by adding 1 equivalent of potassium carbonate relative to the raw material HMF and a specified amount of each metal catalyst to distilled water, and diluting with distilled water so that the HMF concentration was 0.1 M. The amount of each metal catalyst added was as shown in Table 1 below.

[0063] Next, the screw-cap test tube was capped with a septum, and a balloon filled with oxygen gas was attached to the screw-cap test tube. The oxygen gas pressure in the balloon was 1 atm. The screw-cap test tube was then placed in an oil bath, and the oxidation reaction of HMF was carried out at 100°C for 16 hours.

[0064] The reaction solution after the oxidation reaction was filtered through Celite, and a portion was collected and analyzed by HPLC. The types and amounts of metal catalysts and the production ratios of each compound in Examples 3 to 8 are shown in Table 1 below. As shown in Table 1, the production ratio of FDCA was high, at 80% or more, in all Examples.

[0065] (Examples 9 to 10) In Examples 9 and 10, in order to confirm the difference in the production ratio of FDCA depending on the ratio of each metal catalyst, batch synthesis of FDCA was performed by oxidizing HMF using three types of metal catalysts, Pt / C catalyst, Pd / C catalyst, and Ru / C catalyst. All of the metal catalysts used were in powder form. Specifically, the oxidation reaction of HMF was carried out in the same manner as in Example 2, except that the amount of metal catalyst added was the amount shown in Table 1 below, and the reaction time was 5 hours.

[0066] The reaction solution after the oxidation reaction was filtered through Celite, and a portion was collected and analyzed by HPLC. The types and amounts of metal catalysts and the production ratios of each compound in Examples 9 and 10 are shown in Table 1 below. As shown in Table 1, the production ratio of FDCA was high, at 80% or more, in all Examples. In particular, when the ratio of Pt / C catalyst:Pd / C catalyst:Ru / C catalyst was 1:1:1, the production ratio of FDCA was extremely high.

[0067] (Examples 11 to 13) In Examples 11 to 13, in order to confirm the difference in the production ratio of FDCA depending on the type of transition metal used as a promoter in a ternary catalyst containing Pt and Pd, batch synthesis of FDCA was performed by oxidizing HMF using three types of metal catalysts, namely, Pt / C catalyst, Pd / C catalyst, and the metal catalyst shown in the following Table 1. All of the metal catalysts used were in powder form.

[0068] Specifically, first, the air in a 15 mL screw-top test tube was replaced with nitrogen and then with oxygen. Next, 0.5 mmol (63 mg) of HMF, 1 equivalent of potassium carbonate (0.5 mmol, 69 mg) relative to HMF, 1.0 mL of distilled water, 20 mg (1 mol%) of Pt / C catalyst with a Pt content of 5 mass%, 11 mg (1 mol%) of Pd / C catalyst with a Pd content of 5 mass%, and 5 mol% of various promoters were added to the screw-top test tube whose inside had been replaced with oxygen to prepare a reaction solution. As the promoter, CrO3 was used in Example 11, Ag2O in Example 12, and Cu2O in Example 13.

[0069] Next, the screw-cap test tube was capped with a septum, and a balloon filled with oxygen gas was attached to the screw-cap test tube. The oxygen gas pressure in the balloon was 1 atm. The screw-cap test tube was then placed in an oil bath, and the oxidation reaction of HMF was carried out at 100°C for 16 hours.

[0070] The reaction solution after the oxidation reaction was filtered through Celite, and a portion was collected and analyzed by HPLC. The types and amounts of metal catalysts and the production ratios of each compound in Examples 11 to 13 are shown in Table 1 below. As shown in Table 1, the production ratio of FDCA was high, at 80% or more, in all Examples. In particular, in Examples 12 and 13, which used CrO3 or Ag2O as the co-catalyst, the production ratio of FDCA was extremely high.

[0071] [Table 1]

[0072] (Reference example 1~Reference example 6) In Reference Examples 1 to 6, in order to confirm the tendency of the difference in the production ratio of FDCA depending on the type of transition metal used as a promoter in a binary or ternary catalyst containing Pt and Pd, batch synthesis of FDCA was performed by oxidizing HMF using three types of metal catalysts, namely, Pt / C catalyst, Pd / C catalyst, and the metal catalysts shown in the following Table 2. All of the metal catalysts used were in powder form.

[0073] Specifically, first, the air in a 15 mL screw-top test tube was replaced with nitrogen and then with oxygen. Next, 0.5 mmol (63 mg) of HMF, 1.1 equivalents of potassium carbonate (0.5 mmol, 69 mg) relative to HMF, 1.0 mL of distilled water, 40 mg (1 mol%) of Pt / C catalyst with a Pt content of 5 mass%, 11 mg (1 mol%) of Pd / C catalyst with a Pd content of 10 mass%, and 5 mol% of various promoters (shown in Table 1) were added to the screw-top test tube whose inside had been replaced with oxygen to prepare a reaction solution. In addition, in Reference Example 6, a binary catalyst was used, and no promoter was used.

[0074] Next, the screw-cap test tube was capped with a septum, and then a balloon filled with oxygen gas was attached to the screw-cap test tube. The pressure of the oxygen gas in the balloon was 1 atm. The screw-cap test tube was then placed in an oil bath, and the oxidation reaction of HMF was carried out at 100°C for 5 hours. In Reference Examples 1 to 6, the reaction time was shortened to 5 hours in order to confirm only the tendency of the oxidation reaction.

[0075] The reaction solution after the oxidation reaction was filtered through Celite, and a portion was collected and analyzed by HPLC. The types and amounts of metal catalysts and the production ratios of each compound in Reference Examples 1 to 6 are shown in Table 2 below. As shown in Table 2, when the Ru / C catalyst was used (Reference Example 1), HMF was completely consumed (reacted), and the production ratio of FDCA was the highest. In addition, when the CrO3 catalyst and the Ag2O catalyst were used (Reference Examples 2 and 3), HMF was almost completely consumed (reacted) as in the case of the Ru / C catalyst, but the proportion of intermediates was higher than in the case of the Ru / C catalyst. When the TiO2 catalyst was used (Reference Example 5), the consumption of HMF was almost the same as in the case of the binary catalyst (Reference Example 6), but the intermediates were oxidized to FDCA more than in the case of the binary catalyst. When the C5H6NO3ClCr catalyst was used (Reference Example 5), the tendency was almost the same as in the case of the binary catalyst (Reference Example 6).

[0076] [Table 2]

Claims

1. The method includes an oxidation step of selectively oxidizing a hydroxy group and a formyl group of 5-hydroxymethylfurfural in the presence of two or more metal catalysts, The method for producing 2,5-furandicarboxylic acid contains platinum and palladium as the metal catalyst.

2. The method for producing 2,5-furandicarboxylic acid according to claim 1, wherein the metal catalyst used in combination with platinum and palladium contains one or more transition metals (excluding platinum and palladium).

3. The method for producing 2,5-furandicarboxylic acid according to claim 2, wherein the transition metal is one or more metal elements selected from the group consisting of ruthenium, chromium, gold, silver, copper, iron, nickel and cobalt.

4. The method for producing 2,5-furandicarboxylic acid according to any one of claims 1 to 3, wherein the total amount of the metal catalyst is 0.01 mol to 0.1 mol per 1 mol of 5-hydroxymethylfurfural.

5. The method for producing 2,5-furandicarboxylic acid according to any one of claims 1 to 3, wherein the metal catalyst comprises a platinum catalyst in which platinum is supported on a carbon support and a palladium catalyst in which palladium is supported on a carbon support.

6. The method for producing 2,5-furandicarboxylic acid according to claim 2 or 3, wherein the metal catalyst comprises a transition metal catalyst in which the transition metal is supported on a carbon support.

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