JP5207677B2 - Process for producing 2,5-furandicarboxylic acid - Google Patents

Description

  The present invention relates to a method for producing 2,5-furandicarboxylic acid.

  5-Hydroxymethylfurfural (hereinafter abbreviated as 5-HMF) can be obtained by dehydrating hexoses such as fructose and glucose, and can be used as an intermediate for surfactants, plastics and resins. It is a useful compound that can be used. 5-HMF is oxidized by various oxidizing agents and catalysts, and 2,5-diformylfuran (hereinafter abbreviated as DFF), 2-carboxy-5-formylfuran (hereinafter abbreviated as CFF), 2,5- Flange carboxylic acid (hereinafter abbreviated as FDCA) is manufactured. For example, as a method using a catalyst, in Patent Document 1, CFF and FDCA are synthesized by air-oxidizing 5-HMF using a platinum-supported carbon catalyst. In Patent Document 2, DFF, CFF, and FDCA are produced by air-oxidizing 5-HMF together with a Co / Mn / Zr / Br catalyst under high temperature and high pressure. In Patent Document 3, 5-HMF is mixed with air in a dimethyl sulfoxide (hereinafter abbreviated as DMSO) together with cuprous chloride and 2,2,6,6-tetramethylpiperidinooxy (hereinafter abbreviated as TEMPO). DFF is manufactured by oxidation.

In addition, in the method using an oxidizing agent, in Non-Patent Document 1, 5-HMF is allowed to coexist with nitric acid at a high temperature of 100 ° C. for 16 hours to 64 hours, or potassium permanganate with respect to an aqueous 5-HMF solution at room temperature. FDCA is synthesized by a method of oxidizing 5-HMF by dropwise addition of a pyridine solution. Non-Patent Document 1 further provides a method for producing DFF, and DFF is produced from 5-HMF by adding barium permanganate at 80 degrees in an organic solvent.
JP-A-2-88569 Special table 2003-528868 gazette JP-A-3-101672 TONI EL HAJJ, ANTOINE MASROUA, JEAN-CLAUDE MARTIN, GERARD D ▲ E ▼ SCOTES, BULLETIN DE LA SOCI ▲ E ▼ T ▲ E ▼ CHIMIQUE DE FRANCE. 1987, no. 5, p. 855-860

  In the method of producing FDCA by oxidizing 5-HMF with a platinum catalyst in Patent Document 1, FDCA can be obtained in a high yield, but since the production unit price is high because a large amount of noble metal catalyst is used, There is a problem in application to industrial production. Further, in the method of producing FDCA by oxidizing 5-HMF with a catalyst under high temperature and high pressure in Patent Document 2, energy required for heating and pressurization is required, and the apparatus becomes complicated. Application to production is difficult. In the method of producing FDCA by oxidizing air with 5-HMF in a DMSO solution using a catalyst in Patent Document 3, DMSO, which is a high-boiling organic solvent, is used as a solvent, and thus there is a problem such as a large environmental load. There is. Patent Document 3 discloses DFF production, but does not disclose any FDCA production.

  Further, in the method of producing FDCA by oxidizing 5-HMF using nitric acid in Non-Patent Document 1, the yield of FDCA is as low as 24%, and further, reaction conditions at high temperatures are required. You need extra energy. In the method of oxidizing 5-HMF by dropwise addition of a pyridine solution of potassium permanganate, an organic solvent having a larger environmental load than water is used, and the yield of FDCA is about 70%. There is a problem that it is efficient.

  Therefore, it has been desired to construct a method that can produce FDCA inexpensively and efficiently under mild reaction conditions without requiring an expensive catalyst or solvent.

  Accordingly, as a result of intensive studies to solve the above-mentioned problems, the present inventors have found that, in an aqueous solution and in an alkaline environment, the Cannizzaro reaction for CFF and 5-hydroxymethyl-2-furancarboxylic acid which is a by-product of the reaction. It was found that FDCA can be efficiently produced at low cost by combining with an oxidation reaction in the presence of a catalyst (hereinafter abbreviated as HMFA).

That is, the manufacturing method of FDCA according to the present invention is:
A method for producing FDCA by a Cannizzaro reaction for CFF in an aqueous solution in an alkaline environment,
Wherein the aqueous solution Cannizzaro reaction is carried out by adding the catalyst and oxidizing agent, back to the CFF by oxidizing HMFA by-produced in the reaction, and subjected to the Cannizzaro reaction,
The alkaline environment is characterized by adding 5.0 equivalents or more and 25 equivalents or less of alkali to the CFF .

Moreover, in this invention, it is possible to implement, producing | generating CFF within a reaction system from 5-HMF as a raw material. Therefore, the second FDCA manufacturing method according to the present invention is:
A process for producing 2,5-furandicarboxylic acid (hereinafter abbreviated as FDCA) by a Cannizzaro reaction with 2-carboxy-5-formylfuran (hereinafter abbreviated as CFF) in an aqueous solution in an alkaline environment, A catalyst and an oxidizing agent are added to an aqueous solution in which the reaction is performed, and 5-hydroxymethyl-2-furancarboxylic acid (hereinafter abbreviated as HMFA) by-produced in the reaction is oxidized and returned to CFF, and the cannizzaro Subjected to reaction,
The CFF is produced in the aqueous solution starting from 5-HMF ;
The alkaline environment is characterized by adding 5.0 equivalents or more and 20 equivalents or less of alkali to the 5-HMF .

  According to the present invention, FDCA can be efficiently produced under mild conditions such as normal temperature and pressure without using an expensive noble metal catalyst or solvent.

  According to the method for producing FDCA according to the present invention, FDCA can be produced at low cost from CFF or 5-HMF under mild conditions by using a combination of a Cannizzaro reaction and an oxidation reaction with an oxidizing agent in the presence of a catalyst. be able to.

  The present invention relates to a Cannizzaro reaction to CFF in an alkaline environment in solution and an oxidation reaction by an oxidizing agent in the presence of a catalyst of 5-hydroxymethyl-2-furancarboxylic acid (HMFA) which is a byproduct of the reaction. This is a method for producing FDCA using CFF as a raw material by combination.

That is, in the FDCA manufacturing method according to the present invention,
(I) a reaction for producing FDCA and HMFA by a Cannizzaro reaction for CFF;
(Ii) A reaction in which the HMFA is oxidized with an oxidizing agent in the presence of a catalyst to produce CFF proceeds in parallel.

(In the above reaction formula, CR represents the Cannizzaro reaction, and OR represents the oxidation reaction.)
As a result, in the method for producing FDCA according to the present invention, HMFA, which is a by-product, is oxidized by a catalyst and returned to CFF, thereby suppressing accumulation of HMFA and increasing the amount of FDCA, which is a target product, to be produced be able to.

  The Cannizzaro reaction is a reaction in which an aldehyde is converted to a corresponding carboxylic acid and alcohol by an alkali, and occurs when there is no hydrogen in the adjacent carbon of the aldehyde. In particular, it is a disproportionation reaction to carboxylic acid and alcohol by two molecules of aldehyde.

The catalyst used for the oxidation reaction may be any catalyst that can perform the oxidation reaction under conditions that do not inhibit the Cannizzaro reaction. In the present invention, cupric bromide as the preferred form, 2,2'-bipyridine, has been described an example of using a catalyst comprising TEMPO, Besides, for _{example, MnFe 1.5 Ru 0.35 Cu 0.15 O} 4 catalyst , Ru—Co (OH) ₂ —CeO ₂ , CuCl / TEMPO, Pd (OAc) _{2 and the} like. The catalyst is a catalyst for synthesizing aldehyde from alcohol. Moreover, since it can react in aqueous solution, without using an organic solvent, it has the characteristics which can synthesize | combine to a carboxylic acid by combining with a cannizzaro reaction. Therefore, by these catalysts, HMFA which is a by-product can be oxidized and returned to CFF. The form of the catalyst is not particularly limited. Furthermore, the amount of the catalyst used is not particularly limited, but it is preferably used in an amount of 0.1 equivalent or more with respect to CFF as a raw material from the viewpoint of the yield of FDCA.

  The oxidant used for the oxidation reaction is not particularly limited, but a gas containing molecular oxygen such as oxygen gas and air can be used. Moreover, as another oxidizing agent, permanganate, hydrogen peroxide, chlorite, hypochlorite, or the like can be used.

  The concentration of CFF in the aqueous solution is not particularly limited, but is preferably 0.1% by weight or more and 20% by weight or less, and more preferably 1.0% by weight or more and 10% by weight or less from the viewpoint of production efficiency.

  As the alkali to be added, for example, any of alkali metal compounds, alkaline earth metal compounds, ammonium ions, other organic bases, etc. may be used, either one of alkali metal hydroxides and alkaline earth metal hydroxides or Two or more are preferably used. For example, examples of the alkali metal hydroxide include sodium hydroxide and potassium hydroxide, and examples of the alkaline earth metal hydroxide include barium hydroxide and calcium hydroxide. Among these, it is particularly preferable to use any one of sodium hydroxide and potassium hydroxide or a combination thereof. These alkalis are preferably used as an aqueous solution from the viewpoint of handling.

  The amount of alkali to be added can be adjusted so that CFF cannizzaro reaction can be performed and HMFA as a by-product is oxidized to prevent the formation of CFF. is not. For example, the amount of alkali is preferably 1.0 equivalent or more and 30 equivalents or less, and 5.0 equivalents or more and 25 equivalents or less with respect to CFF, from the viewpoint of the implementation conditions of the Cannizzaro reaction and oxidation reaction. Is more preferably 10 equivalents or more and 20 equivalents or less.

  The reaction temperature is not particularly limited as long as it is a temperature condition in which the CFF cannizzaro reaction can be performed and the by-product HMFA can be oxidized to produce CFF. These reactions can be carried out, for example, at 10 ° C. to 80 ° C., and can be heated as necessary. However, room temperature (around 25 ° C.) is preferable for reducing energy consumption.

  In the present invention, in addition to CFF, 5-HMF, DFF, 2,5-dihydroxymethylfuran (hereinafter abbreviated as DHMF) or HMFA can be used as a starting material. From these compounds, CFF can be produced by a combination of an oxidation reaction with an oxidizing agent and a Cannizzaro reaction in the presence of a catalyst. As described above, FDCA can be produced from CFF by a combination of a Cannizzaro reaction and an oxidation reaction with an oxidizing agent in the presence of a catalyst. Therefore, FDCA can be produced using 5-HMF or the like as a starting material.

  Hereinafter, the production route to FDCA using 5-HMF as a starting material will be described as an example.

  When 5-HMF is subjected to a Cannizzaro reaction and an oxidation reaction by an oxidizing agent in the presence of a catalyst, a reaction in which DFF is generated by oxidation of 5-HMF (reaction route (1)) and a Cannizzaro reaction of 5-HMF Causes a reaction to generate HMFA (reaction route (2)) and DHMF (reaction route (3)).

  The produced DFF further undergoes a Cannizzaro reaction, and CFF (reaction route (4)) and 5-HMF (reaction route (5)) are produced. From the produced CFF, as described above, FDCA (reaction route (6)) and HMFA (reaction route (7)) are produced by the Cannizzaro reaction, and at this time, the oxidation reaction of HMFA by the oxidizing agent in the presence of the catalyst ( The amount of FDCA produced increases under conditions where reaction pathway (8) occurs. 5-HMF generated by the Cannizzaro reaction of DFF is oxidized again (reaction path (1)) to generate DFF.

  Moreover, CFF is produced | generated by oxidation from HMFA produced | generated by the Cannizzaro reaction (reaction path | route (3)) of 5-HMF, and FDCA is produced | generated from CFF as mentioned above.

  Moreover, 5-HMF is produced again from DHMF produced by the Cannizzaro reaction of 5-HMF by oxidation (reaction route (9)). HMFA produced by the 5-HMF Cannizzaro reaction is oxidized to produce CFF as shown in the reaction route (8).

  The above reactions are collectively shown in the following reaction formula.

(In the above reaction formula, CR represents the Cannizzaro reaction, and OR represents the oxidation reaction.)
The above reaction is the main reaction under conditions where 5-HMF undergoes a Cannizzaro reaction and an oxidation reaction with an oxidizing agent in the presence of a catalyst. Therefore, when 5-HMF is placed under predetermined conditions, the reaction proceeds in the direction in which CFF is generated, that is, in the direction in which FDCA is generated, and FDCA can be produced in high yield.

  In addition, when 5-HMF causes a Cannizzaro reaction, DHMF that does not proceed in the CFF generation direction is generated. Accordingly, it is preferable to efficiently produce FDCA by proceeding with the oxidation reaction of 5-HMF in advance to produce DFF and CFF, and then adding an alkali to cause the Cannizzaro reaction during the reaction. . When the 5-HMF oxidation reaction proceeds in advance, it can be carried out under either acidic or alkaline conditions, but it is particularly preferred to carry out under alkaline conditions such that the oxidation reaction takes place preferentially over the Canizzaro reaction. . Moreover, it is preferable that after all 5-HMF is oxidized, an alkali is added to cause the Cannizzaro reaction.

  Below, the manufacturing method of FDCA which uses 5-HMF as a starting material which concerns on this invention is demonstrated in detail. In the following description, the catalyst is added in the order of cupric bromide, 2,2′-bipyridine, and TEMPO. However, the present invention is not limited to this, and other catalysts described above can be used. . Further, the addition method and order of the catalyst may be any method and order. Furthermore, although the alkali is added as an aqueous solution, the present invention is not limited to this, and it may be added as a solution or as a solid. Similarly, the addition method and order of the catalyst, alkali, and raw material are not limited to the method and order described below, and any order and method may be used.

  First, cupric bromide, 2,2'-bipyridine, and TEMPO are added as catalysts to the reaction vessel, and water is added and stirred for 5 minutes to suspend the catalyst.

  At this time, the ratio of cupric bromide, 2,2′-bipyridine, and TEMPO may be any ratio, but the molar ratio of 2,2′-bipyridine to cupric bromide is 0.00. It is preferably 5 or more and 3 or less, particularly preferably 1 or more and 2 or less. Since 2,2′-bipyridine is coordinated to cupric bromide, the molar ratio of 2,2′-bipyridine to cupric bromide is set to 1 or more, whereby 2,2′-bipyridine is converted to This is because the amount can be sufficient for coordination.

  Next, an alkali is added to the solution in which the catalyst is suspended to make the solution alkaline. At this time, the alkali is preferably added as an aqueous solution.

  The amount of alkali to be added is preferably 1.0 equivalent or more and 30 equivalents or less, and 2.0 equivalents or more from the viewpoint of the conditions of the Cannizzaro reaction and the oxidation reaction in the presence of a catalyst with respect to 5-HMF. It is more preferably 25 equivalents or less, and particularly preferably 5.0 equivalents or more and 20 equivalents or less. If the amount of alkali is too small, the system will not be in an alkaline environment necessary for oxidation, and oxidation of 5-HMF may not proceed sufficiently. Therefore, it is desirable to carry out at 1.0 equivalent or more. If the amount of alkali is too large, the Cannizzaro reaction becomes dominant and the amount of CFF produced decreases.

  Thereafter, 5-HMF is added to perform a Cannizzaro reaction and an oxidation reaction to generate FDCA via CFF. The oxidizing agent used in the oxidation reaction is not particularly limited, but is preferably a gas containing oxygen such as oxygen and air. In this case, the oxidation reaction can be advanced by bubbling.

  At this time, the concentration of 5-HMF in the aqueous solution is not particularly limited, but is preferably 0.1% by weight or more and 10% by weight or less from the viewpoint of efficiency, and is 1.0% by weight or more and 5.0% by weight. % Or less is more preferable.

  The present invention also provides a method for adding alkali during the reaction in the method for producing FDCA from 5-HMF. For example, in the initial stage of the reaction, the oxidation reaction is allowed to proceed under conditions such that the 5-HMF Cannizzaro reaction does not occur or hardly occurs. And the yield of FDCA can be improved by adding an alkali after oxidizing a certain amount or all 5-HMF to DFF, making reaction progress to the production | generation direction of CFF and FDCA. At this time, the ratio of the amount of alkali added to the amount of alkali added to the solution used for the reaction in advance is preferably 2 or more.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Reference Examples. However, Examples and Reference Examples do not limit the present invention. That is, the present invention is not limited to the experimental conditions used in the following examples and reference examples.

  First, as a reference example, an example in which FDCA is generated from CFF only by the Cannizzaro reaction without adding a catalyst for the oxidation reaction is shown.

(Reference Example 1)
Sodium hydroxide (0.57 g) and water are added so that the concentration of CFF (0.2 g) is 1.0 wt% to prepare a CFF aqueous solution. At this time, sodium hydroxide is equivalent to 10 equivalents relative to CFF. The prepared CFF aqueous solution was stirred at room temperature and normal pressure to carry out the reaction. After the reaction for 46 hours, the production rate of FDCA and by-products (HMFA) and the residual rate of CFF were calculated by high performance liquid chromatography (hereinafter abbreviated as HPLC). The production rate of FDCA was 18.6%, The production rate of HMFA was 14.8%, and the residual rate of CFF was 62.6%.

(Reference Example 2)
The amount of sodium hydroxide added was 20 equivalents relative to CFF, and the reaction was carried out under the same conditions as in Reference Example 1 under other conditions. As a result, the production rate of FDCA was 38.1%, the production rate of HMFA was 34.2%, and the residual rate of CFF was 31.0%.

  The results of Reference Examples 1 and 2 are summarized in Table 1.

  Next, the Example about manufacture of FDCA which combined the Cannizzaro reaction and the oxidation reaction with respect to CFF is shown.

( Reference Example A )
The molar ratio of cupric bromide, 2,2′-bipyridine, and TEMPO was set to 1/1/1, and weighed 0.25 g, 0.17 g, and 0.17 g respectively (about 0 to CFF each). .3 equivalents) After suspending the catalyst for 5 minutes, 0.07 ml of 10M aqueous sodium hydroxide was added to make the solution alkaline. At this time, sodium hydroxide is 0.2 equivalent to CFF. To this aqueous solution, 0.5 g of CFF was added, and water was added so that the CFF concentration was 1.0% by weight. The solution was bubbled to cause an oxidation reaction. The reaction temperature was 25 ° C.

  After bubbling for 14 hours, the product was identified and quantified by HPLC. As a result, the production rate of FDCA was 12.3% and the residual rate of CFF was 86.5%.

(Example 2)
2. Weigh cupric bromide, 2,2′-bipyridine, and TEMPO in 0.41 g, 0.28 g, and 0.28 g each (about 0.5 equivalent to CFF), and add 10M aqueous sodium hydroxide solution. The reaction was carried out under the same conditions as in Reference Example A except for 5 ml (10 equivalents to CFF) and other conditions (excluding the reaction time). After 10 hours of bubbling, the production rate of FDCA was 71.7% and the residual rate of CFF was 6.7%.

(Example 3)
2. Weigh cupric bromide, 2,2′-bipyridine, and TEMPO at 0.57 g, 0.40 g, and 0.40 g each (about 0.7 equivalents relative to CFF), and add 10M aqueous sodium hydroxide solution. The reaction was carried out under the same conditions as in Reference Example A except for 5 ml (10 equivalents to CFF) and other conditions (excluding the reaction time). After 10 hours of bubbling, the production rate of FDCA was 88.3% and the residual rate of CFF was 0.8%.

The results of Reference Example A and Examples 2 and 3 are summarized in Table 2.

  Next, the Example about CFF manufacture from 5-HMF is shown.

(Reference Example 3)
The molar ratio of cupric bromide, 2,2'-bipyridine, and TEMPO was measured at a ratio of 1/1/1 by 0.10 g, 0.07 g, and 0.07 g, respectively (for 5-HMF, respectively). (About 0.1 equivalent) After suspending the catalyst for 5 minutes, 1.5 ml of 10M aqueous sodium hydroxide solution was added to make the solution alkaline. At this time, sodium hydroxide becomes 2.0 equivalent with respect to 5-HMF. To this aqueous solution, 0.5 g of 5-HMF was added, and water was added so that the concentration of 5-HMF was 1.0% by weight. The solution was oxidized by air bubbling at a reaction temperature of 25 ° C.

  After 25 hours, the product was identified and quantified by HPLC. As a result, the production rate of CFF was 53.1% and the residual rate of 5-HMF was 4.1%. At this time, 28.5% of DFF was produced as a by-product.

(Reference Example 4)
Weigh cupric bromide, 2,2'-bipyridine, and TEMPO 0.27g, 0.19g, and 0.19g each (approximately 0.3 equivalents to 5-HMF), and add 10M aqueous sodium hydroxide solution. The amount was 1.5 ml (2.0 equivalents relative to 5-HMF), and other conditions (excluding the reaction time) were the same as in Reference Example 3 to oxidize 5-HMF.

  The production rate of CFF after 13 hours was 78.3%, 5-HMF did not remain, and the production rate of DFF as a by-product was 2.1%.

(Reference Example 5)
Cupric bromide, 2,2′-bipyridine, and TEMPO were weighed out in amounts of 0.45 g, 0.31 g, and 0.31 g, respectively (about 0.5 equivalent to 5-HMF), and 10M aqueous sodium hydroxide solution was added. Oxidation of 5-HMF was performed under the same conditions as in Reference Example 3 except for 0.8 ml (1.0 equivalent to 5-HMF) and other conditions (excluding the reaction time).

  The production rate of CFF after 10 hours was 87.5%, there was no remaining 5-HMF, and the production rate of DFF as a by-product was 3.4%.

  The results of Reference Examples 3 to 5 are summarized in Table 3.

  Next, the Example about manufacture of FDCA characterized by adding an alkali in the middle of reaction is shown.

Example 4
The molar ratio of cupric bromide, 2,2′-bipyridine, and TEMPO was measured at a ratio of 1/1/1 by 0.45 g, 0.32 g, and 0.32 g, respectively (with respect to 5-HMF. After suspending the catalyst for 5 minutes, 4.0 ml of 10M aqueous sodium hydroxide solution was added to make the solution alkaline. At this time, sodium hydroxide becomes 5.0 equivalent with respect to 5-HMF. To this aqueous solution, 0.5 g of 5-HMF was added, and water was added so that the concentration of 5-HMF was 1.0% by weight. The solution was oxidized by air bubbling.

  After 20 hours, the product was identified and quantified by HPLC. As a result, the production rate of FDCA was 49.8%, and 5-HMF did not remain. At this time, 13.4% of CFF and 3.1% of HMFA were produced as by-products.

( Reference Example B )
The reaction was started in the same manner as in Example 4 except that the amount of 10M sodium hydroxide aqueous solution was 0.8 ml (sodium hydroxide was 1.0 equivalent with respect to 5-HMF).

  After 3 hours, it was confirmed by HPLC that all of 5-HMF had been consumed, and 0.8 ml of 10M aqueous sodium hydroxide solution (1.0 equivalent of sodium hydroxide relative to 5-HMF used) was added dropwise to this solution. Added, and air bubbling was performed.

  After 18 hours, the product was identified and quantified by HPLC. As a result, the production rate of FDCA was 56.8%, the production rate of CFF was 8.2%, and the production rate of HMFA was 14.3%. There was no remaining 5-HMF.

(Example 6)
In Reference Example B , the amount of 10 M aqueous sodium hydroxide solution added in an additional amount was 3.2 mL (sodium hydroxide was 4.0 equivalents relative to 5-HMF used) all at once, and other conditions (10 M The reaction was conducted under the same conditions as in Reference Example B except for the reaction time after addition of the aqueous sodium hydroxide solution.

  After 20 hours, the product was identified and quantified by HPLC. As a result, the production rate of FDCA was 69.5%, the production rate of CFF was 1.5%, and the production rate of HMFA was 17.0%. There was no remaining 5-HMF.

(Example 7)
Bubbling was carried out while adding 3.2 ml of 10 M sodium hydroxide added in Example 6 in small portions over 4 hours at a rate of 0.8 ml per hour, and other conditions (after addition of 10 M aqueous sodium hydroxide solution) The reaction was carried out under the same conditions as in Example 6.

  After 9 hours, the production rate of FDCA was 80.9%, the production rate of CFF was 0.6%, and the production rate of HMFA was 7.2%. There was no remaining 5-HMF.

(Example 8)
The 5-HMF concentration was adjusted to 5.0% by weight, and the reaction was carried out under the same conditions as in Example 6 except for other conditions (excluding the reaction time after addition of a 10M aqueous sodium hydroxide solution).

  After 11 hours, the production rate of FDCA was 67.2%, the production rate of CFF was 0.7%, and the production rate of HMFA was 27.1%. There was no remaining 5-HMF.

The results of Reference Example B and Examples 4 , 6, 7, and 8 are summarized in Table 4.

  In Examples 4 to 7, the concentration of 5-HMF is 1.0% by weight, and in Example 8 it is 5.0% by weight. In Examples 6 and 8, a sodium hydroxide aqueous solution was added all at once 3 hours after the start of bubbling, and Example 7 was a small amount of sodium hydroxide at 0.8 ml per hour for 4 hours 3 hours after the start of bubbling. Added in increments.

(Reference Example 6)
The molar ratio of cupric bromide, 2,2'-bipyridine, and TEMPO was measured at a ratio of 1/1/1 by 0.45 g, 0.31 g, and 0.31 g, respectively (with respect to 5-HMF, respectively) The catalyst was suspended for about 5 minutes. Thereafter, 0.5 g of 5-HMF was added without adding 10 M aqueous sodium hydroxide solution, and water was added so that the 5-HMF concentration was 1.0 weight percent to prepare an aqueous solution. The solution was oxidized by air bubbling at a reaction temperature of 25 ° C.

  After 15 hours, when the product was identified and quantified by HPLC, the production rate of FDCA was 0%, the production rate of CFF was 12.8%, the production rate of HMFA was 1.5%, and the production rate of DFF was It was 31.5%. The residual ratio of 5-HMF was 43.4%.

Claims (16)

A process for producing 2,5-furandicarboxylic acid (hereinafter abbreviated as FDCA) by a Cannizzaro reaction with 2-carboxy-5-formylfuran (hereinafter abbreviated as CFF) in an aqueous solution in an alkaline environment, A catalyst and an oxidizing agent are added to an aqueous solution in which the reaction is performed, and 5-hydroxymethyl-2-furancarboxylic acid (hereinafter abbreviated as HMFA) by-produced in the reaction is oxidized and returned to CFF, and the cannizzaro subjected to the reaction,
The alkaline environment is obtained by adding 5.0 equivalents or more and 25 equivalents or less of alkali to the CFF .   The method for producing FDCA according to claim 1, wherein the alkaline environment is obtained by adding 10.0 equivalents of alkali to the CFF. A process for producing 2,5-furandicarboxylic acid (hereinafter abbreviated as FDCA) by a Cannizzaro reaction with 2-carboxy-5-formylfuran (hereinafter abbreviated as CFF) in an aqueous solution in an alkaline environment, A catalyst and an oxidizing agent are added to an aqueous solution in which the reaction is performed, and 5-hydroxymethyl-2-furancarboxylic acid (hereinafter abbreviated as HMFA) by-produced in the reaction is oxidized and returned to CFF, and the cannizzaro Subjected to reaction,
The CFF is produced in the solution starting from 5-hydroxymethylfurfural (hereinafter abbreviated as 5-HMF),
The alkaline environment, the relative 5-HMF, 5.0 manufacturing method of F DCA you characterized by comprising the addition of equivalent or more 20 equivalents or less of alkali.   The method for producing FDCA according to claim 3, wherein the alkaline environment is obtained by adding 5.0 equivalents of alkali to the 5-HMF. 5. The method for producing FDCA according to claim 4 , wherein 2,5-diformylfuran (hereinafter abbreviated as DFF) and HMFA are used in the process of generating the CFF from the 5-HMF. The main generation path for generating the CFF from the 5-HMF is as follows:
A pathway for oxidizing the 5-HMF with an oxidizing agent in the presence of a catalyst to produce DFF;
The method for producing FDCA according to claim 5 , comprising a route for producing CFF and 5-HMF by a Cannizzaro reaction for the DFF. The method for producing FDCA according to claim 6 , wherein the 5-HMF produced by the Cannizzaro reaction on the DFF is oxidized with an oxidizing agent in the presence of a catalyst to produce DFF again. The main generation path for generating the CFF from the 5-HMF is as follows.
A pathway for producing HMFA and 2,5-dihydroxymethylfuran (hereinafter abbreviated as DHMF) by the Cannizzaro reaction for 5-HMF;
The method for producing FDCA according to claim 5 , comprising a pathway in which the HMFA is oxidized with an oxidizing agent in the presence of a catalyst to produce CFF. The method for producing FDCA according to claim 8 , wherein DHMF produced by the Cannizzaro reaction on 5-HMF is oxidized with an oxidizing agent in the presence of a catalyst to produce 5-HMF again. The main generation path for generating the CFF from the 5-HMF is as follows.
A method for manufacturing FDCA, comprising a combination of paths for generating CFF according to any one of claims 6 to 9 . The said catalyst consists of cupric bromide, 2,2'-bipyridine, 2,2,6,6-tetramethylpiperidinooxy, The claim in any one of Claim 1 thru | or 10 characterized by the above-mentioned. The manufacturing method of FDCA of description. The method for producing FDCA according to any one of claims 1 to 11 , wherein the oxidizing agent is oxygen or air containing oxygen. The method for producing FDCA according to any one of claims 1 to 12 , wherein the alkali is added during the reaction. The method for producing FDCA according to claim 13 , wherein the alkali is added when all of the 5-HMF is consumed.   The method for producing FDCA according to claim 13 or 14, wherein the ratio of the amount of alkali added to the amount of alkali added to the solution used in the reaction in advance is 2 or more. The alkali, FDCA method according to any one of claims 1 to 15, characterized in that sodium hydroxide or potassium hydroxide.