CN116675660B

CN116675660B - Preparation method of FDCA and FDCA product

Info

Publication number: CN116675660B
Application number: CN202310453374.8A
Authority: CN
Inventors: 柯希贤; 张海峰; 李天源
Original assignee: Putian Dakai New Materials Co ltd
Current assignee: Putian Dakai New Materials Co ltd
Priority date: 2023-04-25
Filing date: 2023-04-25
Publication date: 2024-04-23
Anticipated expiration: 2043-04-25
Also published as: CN116675660A

Abstract

The application provides a preparation method of FDCA and an FDCA product, comprising the following steps: mixing metal salt, solid alkali, a first oxidant and water to obtain a catalyst; mixing the catalyst, 5-hydroxymethylfurfural and water, adding a second oxidant, reacting for 1-10 hours at 25-80 ℃, and adjusting the pH value to 1 to obtain an FDCA crude product; the mass ratio of the 5-hydroxymethylfurfural to the catalyst to the water is 1:0.05-0.5: (2-10); the molar ratio of the 5-hydroxymethylfurfural to the second oxidant is 1:2-20 parts; the solid alkali is magnesium oxide, magnesium hydroxide, hydrotalcite and an alkaline molecular sieve. Compared with the prior art, the raw materials used by the technical method are cheap and easy to obtain, the catalyst has strong stability, can be repeatedly used and easily separated after calcination, meets the requirement of industrialization, and the FDCA crude product prepared by the method has the characteristics of light color, low salt content, low raw material requirement, high purity of solid products and stable production, can be directly dried without yellowing, and does not need freeze drying.

Description

Preparation method of FDCA and FDCA product

Technical Field

The application relates to the technical field of chemical industry, in particular to a preparation method of FDCA and an FDCA product.

Background

2,5-Furandicarboxylic acid (2, 5-furandicarboxylicacid, FDCA) is an important platform compound derived from biomass resources, and more than hundred derivatives have very important application prospects, and can be used as a monomer for synthesizing bio-based polymers. 2,5-furandicarboxylic acid has a similar structure to terephthalic acid, but has a furan ring structure which is easier to degrade in nature than benzene rings, so that 2,5-furandicarboxylic acid can be used for replacing terephthalic acid to synthesize a more environment-friendly high polymer polyester material.

More information about the above solutions can also be found in the following documents:

The Chinese patent document of publication No. 106890659A discloses the preparation of a high-dispersion supported nano gold-palladium bimetallic catalyst and the application of the catalyst in catalyzing the oxidation reaction of 5-hydroxymethylfurfural. The hydroxyapatite and calcium aluminum hydrotalcite hybrid composite double carrier is prepared by an in-situ growth method, and then the high-dispersion supported nano gold-palladium double-metal catalyst is synthesized by an ion exchange method. The catalyst has good catalytic effect in the reaction of preparing 2, 5-furandicarboxylic acid by oxidizing 5-hydroxymethylfurfural, and the conversion rate of 5-hydroxymethylfurfural and the selectivity of 2, 5-furandicarboxylic acid are respectively 90-100% and 80-90%. However, the noble metal catalyst used in the method has high cost and the catalyst preparation process is complex, so that the noble metal catalyst is difficult to apply to the later industrialized production.

The Chinese patent document with publication number CN115073404A discloses a magnetic nano catalyst for producing 2, 5-furandicarboxylic acid, which can be magnetically separated, recovered and reused after the reaction is finished, and solves the problem of energy consumption caused by the difficulty in extremely fine separation of nano catalyst particles in production. However, in order to achieve both magnetic and catalytic effects, the preparation process of the magnetic catalyst becomes complicated, the energy consumption is high, water needs to be distilled off in a rotary manner each time of preparation and recycling, the catalyst is dried at 100 ℃ for 12 hours, calcined at 500 ℃ for 2 hours, and the yield of FDCA under the action of the catalyst is not quite high.

In the process of implementing the present invention, the inventor finds that the following problems exist in the prior art:

In industry, 2, 5-furandicarboxylic acid is usually prepared by catalytic oxidation under alkaline conditions by using 5-Hydroxymethylfurfural (HMF) as a raw material, and the obtained crude product often contains more impurities such as monomethyl acids, acyl groups, humins, salts and the like. When 2, 5-furandicarboxylic acid is used in the synthesis of polymeric polyester materials, these impurities terminate the growth of the polyester molecular chain, affect the polyester properties, and also form color bodies, resulting in coloration of the 2, 5-furandicarboxylic acid and the polyester material.

Disclosure of Invention

In view of the above problems, there is a need to provide a method for preparing FDCA with improved purity, which is used to solve the problem that the crude FDCA product in the prior art contains more impurities.

To achieve the above object, the present inventors provide a method for preparing FDCA, comprising the steps of:

mixing metal salt, solid alkali, a first oxidant and water to obtain a catalyst;

Mixing the catalyst, 5-hydroxymethylfurfural and water, adding a second oxidant, reacting for 1-10 hours at 25-80 ℃, and regulating the pH value to 1 to obtain a product FDCA;

The solid alkali is at least one of magnesium oxide, magnesium hydroxide, hydrotalcite and an alkaline molecular sieve.

Specifically, solid alkali and a first oxidant can be added into the aqueous solution of the metal salt, the reaction temperature is controlled to be 30 ℃, and the mixture is stirred for 1 hour, filtered by suction and dried for 24 hours at 110 ℃. In actual use, the catalyst is not required to be dried, and the raw materials of the catalyst are used for quantification.

The metal salt is used as a catalyst raw material and provides metal elements required by the catalyst. The oxidant adopted in the preparation of the catalyst is a first oxidant, and metal ions are changed into metal ions in a high valence state after reacting with the first oxidant, so that the catalytic activity is provided.

The solid base acts as a support and provides a basic site. The solid alkali adopts at least one of magnesium oxide, magnesium hydroxide, hydrotalcite and alkaline molecular sieve, and the substances contain magnesium element and can be singly or in combination.

The magnesium oxide, magnesium hydroxide, hydrotalcite and basic molecular sieves act as catalyst supports. The metal salt catalyst particles are very fine and the filtration is very slow. And the magnesium oxide, the magnesium hydroxide, the hydrotalcite and the alkaline molecular sieve are used for loading the metal salt catalyst, so that the separation effect of the metal salt catalyst and the reaction liquid is greatly improved.

Wherein, magnesium oxide, magnesium hydroxide, hydrotalcite and basic molecular sieve play a role of providing basic sites, which can improve the activity and catalytic efficiency of the catalyst, and the catalyst has catalytic effect only under basic conditions. The alkalinity provided by the magnesium oxide, the magnesium hydroxide, the hydrotalcite and the alkaline molecular sieve can enable the generated FDCA solid to be dissolved in water, can avoid the influence of direct precipitation and adsorption of the FDCA solid on the surface of the catalyst on the contact area of the catalyst and the reaction liquid, and can avoid the occurrence of the condition of catalyst deactivation.

More importantly, after magnesium oxide, magnesium hydroxide, hydrotalcite and an alkaline molecular sieve are added, the obtained FDCA product is white, is not afraid of high temperature and air, and does not turn yellow. This has great significance for subsequent processing.

Mixing the catalyst, 5-hydroxymethylfurfural and water, adding a second oxidant, reacting at 25-80 ℃ for 1-10h, and regulating the pH value to 1-3 to obtain the product FDCA. The catalyst, 5-hydroxymethylfurfural and water are mixed and a second oxidant is added. The oxidation reaction of 5-hydroxymethylfurfural to 2, 5-furandicarboxylic acid is an exothermic reaction, and if the reaction is directly mixed with a second oxidant, a large amount of heat is emitted, so that the reaction rate of the side reaction of HMF is increased, and the product yield of FDCA is greatly reduced. Meanwhile, the decomposition rate of the oxidant is also accelerated, and the spraying danger exists.

The reaction for preparing the 2, 5-furandicarboxylic acid by oxidizing the 5-hydroxymethylfurfural can be carried out at normal temperature and normal pressure. After the reaction, the pH is regulated to 1-3, and FDCA solid is separated out, thus obtaining the crude product of FDCA.

In contrast to the prior art, the above-described technical method converts metal ions into metal ions of a high valence state by a first oxidizing agent, and the solid alkali carries a metal salt to form a catalyst; the catalyst and the second oxidant are used for catalytic oxidation of 5-hydroxymethylfurfural to prepare a high-purity and high-quality FDCA crude product. The raw materials used by the method are cheap and easy to obtain, the catalyst has strong stability, can be repeatedly used and easily separated after calcination, meets the requirement of industrialization, and the FDCA crude product prepared by the method has the characteristics of light color, low salt content, low raw material requirement, high purity of solid products and stable production, can be directly dried and does not turn yellow, and does not need freeze drying.

Further, the mass ratio of each substance in the catalyst is as follows:

metal salt: solid base: a first oxidizing agent: water = 1: (0.5-5): (0.5-5): (5-20).

The ratio of the metal salt, the solid base, the first oxidant and the water is controlled within the above range, so that the obtained catalyst has better catalytic effect.

Further, the mass ratio of the 5-hydroxymethylfurfural to the catalyst to the water is 1: (0.5-3): (5-15). The water content can be calculated through the mass ratio of the catalyst raw materials, and the catalyst can be dried, so that the water quality can be calculated conveniently.

Further, the molar ratio of the 5-hydroxymethylfurfural to the second oxidant is 1: (5-10). The molar ratio of 5-hydroxymethylfurfural to the second oxidant is controlled within the above range to achieve sufficient conversion of HMF to FDCA.

Further, the first oxidizing agent is at least one of persulfate, potassium persulfate, hypochlorite, and perchlorate. The first oxidizing agent may be selected from any of the above, and is not limited thereto.

Further, the second oxidant is one of hydrogen peroxide, hypochlorite and perchlorate. Specifically, there is a matching relationship between the metal salt and the second oxidizing agent: the iron-based metal salt is used together with hydrogen peroxide, and the cobalt base and the nickel base are used together with hypochlorite and perchlorate.

The first oxidizing agent is used to oxidize the low valence metal ions to higher valence metal ions, and the first oxidizing agent has no requirement on the pH of the system. And the second oxidant is to oxidize hydroxymethyl and aldehyde group into carboxyl under the condition of PH > 7, and has higher requirement on the oxidizing property of the second oxidant. The second oxidant may be used in place of the first oxidant to prepare the catalyst, but the first oxidant may not necessarily be used to oxidize 5-hydroxymethylfurfural.

Further, the metal salt is at least one of ferrous sulfate, ferrous chloride, ferrous nitrate, cobalt sulfate, cobalt chloride, cobalt nitrate, cobalt acetate, nickel chloride, nickel sulfate, nickel phosphate, nickel acetate and nickel nitrate.

Still further, the metal salt is at least one of cobalt sulfate, cobalt chloride, cobalt nitrate, cobalt acetate, nickel sulfate, nickel chloride and nickel nitrate.

Iron, cobalt and nickel are fourth period VIII elements, are common non-noble metals in the catalytic oxidation field, and have an electron layer structure of 3d64s2, 3d74s2 and 3d84s2. In the same valence state, the nuclear charge numbers of iron, cobalt and nickel are sequentially increased, so that the capability of obtaining electrons is sequentially enhanced, the oxidizing property is gradually increased, and the oxidizing property is shown as follows: iron-based < cobalt-based < nickel-based metal salts, so nickel-based and cobalt-based metal salts are preferred. In view of cost, cobalt sulfate, cobalt chloride, cobalt nitrate, cobalt acetate, nickel sulfate, nickel chloride and nickel nitrate, which are commonly used in the market, are preferable.

Further, the method also comprises the step of separating the catalyst: the reaction solution of the crude FDCA product is filtered or centrifuged, the catalyst is separated, washed with water to ph=7, and calcined at 400-700 ℃ for 4-8 hours to obtain the catalyst. The catalyst prepared from the metal salt, the solid alkali and the first oxidant has strong stability, can be repeatedly used after calcination, and is easier to separate.

Compared with the prior art, the technical scheme has the following beneficial effects:

1. The method has the advantages that the reaction temperature is mild, the reaction system is simple, the reaction time is effectively shortened, the high-purity FDCA can be prepared, the complex operations such as loading and pyrolysis are not needed, the reaction is carried out at normal temperature and normal pressure, and the requirement on reaction equipment is reduced;

2. The catalyst is a composite material of non-noble metal oxide, magnesium oxide, hydrotalcite and other solid alkali, and can be efficiently separated and reused;

3. The FDCA solid product obtained by the method has low inorganic salt content, the sample is white, and the sample is directly dried in the air without yellowing, so that the energy consumption of post-treatment can be reduced, the overall production efficiency can be improved, and the method has the characteristic of being suitable for industrial production.

In a second aspect, the present application provides an FDCA product prepared by the method for preparing FDCA according to the first aspect. The FDCA product is white, is not afraid of high temperature and air, and cannot turn yellow, and has great significance for subsequent processing.

The FDCA crude product prepared by the method has light color and low salt content, can be directly dried without yellowing, and does not need freeze drying; the used raw materials are cheap and easy to obtain, the catalyst has strong stability, can be reused after calcination and is easier to separate, and the method meets the requirement of industrialization. The 2, 5-furandicarboxylic acid finished product prepared by the method has the characteristics of low raw material requirement, high purity of solid products and stable production

The foregoing summary is merely an overview of the present application, and is provided to enable those skilled in the art to make and use the present application more clearly and to enable one skilled in the art to make and use the present application.

Detailed Description

In order to describe the possible application scenarios, technical principles, practical embodiments, and the like of the present application in detail, the following description is made with reference to the specific embodiments. The embodiments described herein are only for more clearly illustrating the technical aspects of the present application, and thus are only exemplary and not intended to limit the scope of the present application.

Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearances of the phrase "in various places in the specification are not necessarily all referring to the same embodiment, nor are they particularly limited to independence or relevance from other embodiments. In principle, in the present application, as long as there is no technical contradiction or conflict, the technical features mentioned in each embodiment may be combined in any manner to form a corresponding implementable technical solution.

Unless defined otherwise, technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application pertains; the use of related terms herein is for the purpose of describing particular embodiments only and is not intended to limit the application.

In the description of the present application, the term "and/or" is a representation for describing a logical relationship between objects, which means that three relationships may exist, for example a and/or B, representing: there are three cases, a, B, and both a and B. In addition, the character "/" herein generally indicates that the front-to-back associated object is an "or" logical relationship.

In the present application, terms such as "first" and "second" are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual number, order, or sequence of such entities or operations.

Without further limitation, the use of the terms "comprising," "including," "having," or other like terms in this specification is intended to cover a non-exclusive inclusion, such that a process, method, or article of manufacture that comprises a list of elements does not include additional elements but may include other elements not expressly listed or inherent to such process, method, or article of manufacture.

As in the understanding of "review guidelines," the expressions "greater than", "less than", "exceeding" and the like are understood to exclude this number in the present application; the expressions "above", "below", "within" and the like are understood to include this number. Furthermore, in the description of embodiments of the present application, the meaning of "a plurality of" is two or more (including two), and similarly, the expression "a plurality of" is also to be understood as such, for example, "a plurality of" and the like, unless specifically defined otherwise.

In the description of embodiments of the present application, spatially relative terms such as "center," "longitudinal," "transverse," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "vertical," "top," "bottom," "inner," "outer," "clockwise," "counter-clockwise," "axial," "radial," "circumferential," etc., are used in the description of embodiments of the present application and are based on the orientation or positional relationship shown in the embodiments for convenience of description of the embodiments of the present application or for ease of understanding of the reader, and are not intended to indicate or imply that the devices or components referred to must have a particular position, a particular orientation, or be constructed or operated in a particular orientation and therefore should not be construed as limiting embodiments of the present application.

Unless specifically stated or limited otherwise, the terms "mounted," "connected," "affixed," "disposed," and the like as used in the description of embodiments of the application should be construed broadly. For example, the "connection" may be a fixed connection, a detachable connection, or an integral arrangement; the device can be mechanically connected, electrically connected and communicated; it can be directly connected or indirectly connected through an intermediate medium; which may be a communication between two elements or an interaction between two elements. The specific meaning of the above terms in the embodiments of the present application can be understood by those skilled in the art to which the present application pertains according to circumstances.

In the examples, FDCA was detected by high performance liquid chromatography, and the standard was characterized by an external standard curve method and then measured.

Example 1:

2g of magnesium oxide and 2g of sodium bisulfate are added into 20g of ferrous chloride solution (10%wt), the reaction temperature is controlled to be 30 ℃, the mixture is stirred for 1 hour and then filtered by suction, and the obtained solid product is dried for 24 hours at 110 ℃ to obtain the catalyst solid.

To a 50mL round bottom flask, 2gHMF g of catalyst, 10g of water and 10 times of substrate molar equivalent of hydrogen peroxide are added, the reaction is carried out for 2 hours at 40 ℃, after the reaction is finished, the filtration is carried out, the pH of the filtrate is adjusted to 1-3, the filtration is carried out to obtain a FDCA solid crude product, and the FDCA solid is sampled, dissolved in water, diluted and fixed in volume for HPLC detection.

Example 2:

To 20g of nickel nitrate solution (5% wt) were added 4g of magnesium hydroxide and 2g of potassium monopersulfate, the reaction temperature was controlled at 30℃and after stirring for 1 hour, suction filtration was carried out, and the obtained solid product was dried at 110℃for 24 hours, to obtain a catalyst solid.

2GHMF g of catalyst, 10g of water and 10 times of substrate molar equivalent of sodium hypochlorite are added into a 50mL round bottom flask, the mixture is reacted for 2 hours at 40 ℃, after the reaction is finished, the mixture is filtered, the pH of the filtrate is adjusted to 1-3, the filtrate is filtered to obtain a FDCA solid crude product, and the FDCA solid is sampled, dissolved in water, diluted and fixed in volume for HPLC detection.

Example 3:

2g of hydrotalcite and 4g of sodium hypochlorite are added into 20g of cobalt sulfate solution (10%wt), the reaction temperature is controlled to be 30 ℃, the mixture is stirred for 1 hour and then is filtered by suction, and the obtained solid product is dried for 24 hours at 110 ℃ to obtain the catalyst solid.

To a50 mL round bottom flask, 2gHMF g of catalyst, 10g of water and 5 times of substrate molar equivalent of sodium perchlorate are added, the reaction is carried out for 1h at 60 ℃, after the reaction is finished, the filtration is carried out, the pH of the filtrate is adjusted to 1-3, the filtration is carried out to obtain a FDCA solid crude product, and the FDCA solid is sampled, dissolved in water, diluted and fixed in volume for HPLC detection.

Example 4:

adding 4g of alkaline molecular sieve and 4g of sodium persulfate into 20g of cobalt acetate solution (5%wt), controlling the reaction temperature to be 30 ℃, stirring for 1h, carrying out suction filtration, and drying the obtained solid product at 110 ℃ for 24h to obtain the catalyst solid.

Example 5:

To 20g of nickel chloride solution (5% wt) were added 4g of magnesium hydroxide and 4g of sodium perchlorate, the reaction temperature was controlled at 30℃and after stirring for 1 hour, suction filtration was carried out, and the obtained solid product was dried at 110℃for 24 hours, to obtain a catalyst solid.

2GHMF g of catalyst, 10g of water and 10 times of substrate molar equivalent of sodium hypochlorite are added into a 50mL round bottom flask, the mixture is reacted for 1h at 80 ℃, after the reaction is finished, the mixture is filtered, the pH of the filtrate is adjusted to 1-3, the filtrate is filtered to obtain a FDCA solid crude product, and the FDCA solid is sampled, dissolved in water, diluted and fixed in volume for HPLC detection.

Example 6:

To 20g of a cobalt sulfate solution (5% by weight), 4g of magnesium oxide and 4g of sodium hydrogen sulfate were added, the reaction temperature was controlled at 30℃and after stirring for 1 hour, suction filtration was carried out, and the obtained solid product was dried at 110℃for 24 hours, to obtain a catalyst solid.

Example 7:

2g of magnesium hydroxide, 2g of hydrotalcite and 4g of potassium peroxymonosulfate are added into 20g of cobalt sulfate solution (5%wt), the reaction temperature is controlled to be 30 ℃, the mixture is stirred for 1 hour and then filtered by suction, and the obtained solid product is dried for 24 hours at 110 ℃ to obtain the catalyst solid.

To a 50mL round bottom flask, 2gHMF g of catalyst, 10g of water and 10 times of substrate molar equivalent of sodium perchlorate are added, the reaction is carried out for 2 hours at 40 ℃, after the reaction is finished, the filtration is carried out, the pH of the filtrate is adjusted to 1-3, the filtration is carried out to obtain a FDCA solid crude product, and the FDCA solid is sampled, dissolved in water, diluted and fixed in volume for HPLC detection.

Comparative example 1

To 20g of a cobalt sulfate solution (5% by weight), 4g of sodium hydroxide and 4g of sodium persulfate were added, the reaction temperature was controlled at 30℃and after stirring for 1 hour, suction filtration was carried out, and the obtained solid product was dried at 110℃for 24 hours, to obtain a catalyst solid.

To a 50mL round bottom flask, 2gHMF g of catalyst, 4g of sodium hydroxide, 10g of water and 10 times of sodium hypochlorite with molar equivalent of substrate are added, the reaction is carried out for 1h at 80 ℃, after the reaction is finished, the filtration is carried out, the pH of the filtrate is adjusted to 1-3, the filtration is carried out to obtain a FDCA solid crude product, and the FDCA solid is sampled, dissolved in water, diluted and fixed in volume for HPLC detection.

Comparative example 2

Only one additional step was performed as described in [ comparative example 1], and 1g of activated carbon was added to the charge in a 50mL round bottom flask.

TABLE 1 catalytic oxidation results of different catalysts on 5-hydroxymethylfurfural

1. The theoretical yield of FDCA is calculated by taking all the obtained solid as FDCA; as in comparative example 1, a liquid base (e.g., naOH, naHCO ₃) was used to provide alkalinity, and the resulting FDCA was acidic and soluble in the system. The FDCA solid must be obtained by adding a liquid acid (such as sulfuric acid hydrochloride) to adjust the pH of the system to 1-3. However, many salts such as NaCl/Na ₂SO₄ are formed at the same time as the precipitation of the FDCA solid, and these sodium salts are precipitated together by the inclusion of the FDCA solid, and the salt content reaches 20 to 30% of the FDCA content, so that the theoretical yield of FDCA in comparative example 1 is 117.96%.

2. FDCA purity is the result obtained by taking a solid crude product and carrying out HPLC detection;

3. actual yield of crude FDCA = theoretical yield of crude FDCA purity;

4. Characterization of the optical quality of the FDCA samples and the extent of the yellow-blue color of the samples are expressed as b values in the color space for non-self-illumination (i.e., CIE1976L a b) specified by the international commission on illumination 1976;

5. The actual yield of the FDCA crude product is lower than the theoretical yield of the FDCA crude product, which indicates that inorganic salt is separated out in the process of adjusting the pH of the reaction filtrate to 1-3.

6. The catalyst filtration time is the time taken to filter the catalyst from the reaction solution, and all examples were carried out under the same conditions in the same equipment.

As can be seen from Table 1, comparative example 2, which had 1g of activated carbon added more than comparative example 1, greatly improved the purity of the FDCA product. The purity of the FDCA obtained in the examples 1-6 reaches more than 88%, and the FDCA crude product with the same purity and quality can be obtained without adsorption by using activated carbon.

The FDCA product of comparative example 1 increased in b x value after drying and turned yellow. The FDCA products prepared in examples 1-6 of this embodiment still have a small b-value after drying, and the FDCA products are light in color and low in salt content, and can be directly dried without yellowing, without freeze drying.

The data of the catalyst recovery rate can be used for obtaining the conclusion that the catalyst of the scheme has strong stability, can be reused after calcination and is easier to separate, and the catalyst recovery rates of the examples 1-6 reach more than 86 percent. Wherein, the actual yield of FDCA of example 6 reaches 91.85%, the purity reaches 94.85%, and the recovery rate of the catalyst reaches 91.46%.

Finally, it should be noted that, although the embodiments have been described in the text of the present application, the scope of the present application is not limited thereby. All technical schemes generated by replacing or modifying equivalent structures or equivalent processes based on the essential idea of the application and by directly or indirectly implementing the technical schemes of the embodiments in other related technical fields and the like by utilizing the content written in the description of the application are included in the patent protection scope of the application.

Claims

1. A method for preparing FDCA, comprising the steps of:

Mixing a metal salt, solid alkali, a first oxidant and water to obtain a catalyst, wherein the metal salt is at least one of cobalt sulfate, cobalt chloride, cobalt nitrate and cobalt acetate;

mixing the catalyst, 5-hydroxymethylfurfural and water, adding a second oxidant, reacting for 1-10 hours at 25-80 ℃, and adjusting the pH to 1-3 to obtain an FDCA crude product; the mass ratio of the 5-hydroxymethylfurfural to the catalyst to the water is 1:0.05-0.5: (2-10); the molar ratio of the 5-hydroxymethylfurfural to the second oxidant is 1:2-20,

The first oxidant is at least one of persulfate, hypochlorite and perchlorate, the second oxidant is at least one of hydrogen peroxide, hypochlorite and perchlorate, and the solid alkali is at least one of magnesium oxide and magnesium hydroxide.

2. The method for preparing FDCA according to claim 1, wherein the mass ratio of each substance in the catalyst is:

3. The method for preparing FDCA according to claim 1, wherein the mass ratio of the 5-hydroxymethylfurfural, the catalyst to water is 1: (0.5-3): (5-15).

4. The method for preparing FDCA according to claim 1, wherein the molar ratio of said 5-hydroxymethylfurfural to the second oxidant is 1: (5-10).

5. The method for producing FDCA according to claim 1, further comprising:

A step of separating the catalyst: the reaction solution of the crude FDCA product is filtered or centrifuged, the catalyst is separated, washed with water to ph=7, and calcined at 400-700 ℃ for 4-8 hours to obtain the catalyst.