Catalyst for selective catalytic oxidation of 5-hydroxymethylfurfural to prepare 5-hydroxymethyl-2-furancarboxylic acid, preparation method and application

Abstract

The present application relates to a kind of catalyst for selectively catalyzing oxidation 5-hydroxymethyl furfural to prepare 5-hydroxymethyl-2-furan carboxylic acid and preparation method and application.Catalyst is carbon modified basic magnesium carbonate nanosheet, with basic magnesium carbonate nanosheet as inorganic alkaline base, its surface in situ is covered or grown with carbon quality modification layer;Morphology is the two-dimensional nanosheet with the lateral size distribution of 200~300 nm, the thickness of 15~25 nm, and the random stacking state between sheet layer, form loose three-dimensional porous structure.5-hydroxymethyl furfural, N-hydroxy phthalimide, catalyst and reaction solvent acetonitrile are added into reactor under oxygen atmosphere;After reaction, the reaction liquid is treated, and 5-hydroxymethyl-2-furan carboxylic acid is separated.5-hydroxymethyl-2-furan carboxylic acid is as high as 95.1%, and conversion rate is 90.1%.Without strong base or noble metal, high directional synthesis of 5-hydroxymethyl-2-furan carboxylic acid is realized, and the prominent problems of low selectivity of target product and wide product distribution in prior art are solved.

Description

Technical Field

[0001] This invention belongs to the field of green selective oxidation and organic free radical catalysis technology, specifically a catalyst for the selective catalytic oxidation of 5-hydroxymethylfurfural to prepare 5-hydroxymethyl-2-furanic acid, its preparation method, and its application. Background Technology

[0002] 5-Hydroxymethylfurfural (5-HMF) can be obtained from the dehydration of sugars and is an important biomass platform molecule. Selective oxidation of 5-HMF yields oxygen-containing derivatives such as 5-hydroxymethyl-2-furanic acid, 2,5-dicarboxyfuran, 5-formyl-2-furanic acid, and 2,5-furandicarboxylic acid, which can be further used in the synthesis of polymers and fine chemicals. Among these, 5-HMF, due to its unique intramolecular functional group arrangement, has become a key monomer for the synthesis of green surfactants, high-value pharmaceutical intermediates, and high-performance bio-based polyesters, playing an irreplaceable role in promoting the carbon-neutral transformation of the chemical industry.

[0003] Existing catalytic oxidation systems for the preparation of 5-hydroxymethylfurfural to 5-hydroxymethyl-2-furanic acid are mostly noble metal catalytic systems. For example, Schade et al. (Schade OR, et al. Green Chem, 2018, 20(15): 3530-41.) developed a ZrO2-supported Ag-based catalyst that can catalytically oxidize 5-hydroxymethylfurfural to 5-hydroxymethyl-2-furanic acid in 1 h at 50 °C, 1.0 MPa air atmosphere, and 4.0 molar equivalents of NaOH, achieving a yield of 98%. However, these methods suffer from problems such as high cost of noble metals, complex preparation processes, environmental pollution caused by metal loss, and difficulties in recycling.

[0004] Chinese patent CN118546113A discloses a nanosheet-like S-type heterojunction BiOI / g-C3N4 photocatalyst that achieves the selective oxidation of 5-hydroxymethylfurfural to 5-hydroxymethyl-2-furanic acid in an aqueous phase system at room temperature and pressure using visible light as the light source, with a maximum yield of 43.6%. Although this system achieves a mild and green conversion of biomass platform compounds, its reaction process is highly dependent on a dedicated photocatalytic reactor and visible light source, and the highest yield of the target product is less than 45%, making it difficult to adapt to the needs of industrial-scale continuous production.

[0005] Chinese patent CN118908917A discloses a method for alkali-free catalytic oxidation of 5-hydroxymethylfurfural. This method involves adding persulfate (PMS) as an oxidant to an aqueous solution of 5-hydroxymethylfurfural and using metal oxides or palladium on carbon as a catalyst, followed by thermal catalysis at 30–150 °C or at a concentration of 100–800 mW / cm³. 2The oxidative conversion of 5-hydroxymethylfurfural under photocatalytic conditions can produce products such as 5-formyl-2-furanic acid, 2,5-diformylfuran, 5-hydroxymethyl-2-furanic acid, or 2,5-furandicarboxylic acid. In some examples, the yield of 5-hydroxymethyl-2-furanic acid reached as high as 54.3%. However, the reaction process is highly dependent on the addition of a strong oxidizing persulfate, which increases the production cost and the difficulty of product separation. In addition, the photocatalytic path depends on a dedicated light source and reactor, while the selectivity of 5-hydroxymethyl-2-furanic acid under the thermocatalytic path is generally low and the product distribution is wide, making it difficult to achieve efficient, targeted, and large-scale preparation of a single target product. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a method for the selective catalytic oxidation of 5-hydroxymethylfurfural to prepare 5-hydroxymethyl-2-furanic acid, thereby solving the technical problems of high cost of precious metal catalytic systems, easy degradation of substrates and difficulty in product separation due to strong base systems, and low selectivity of target products in existing technologies.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A catalyst for the selective catalytic oxidation of 5-hydroxymethylfurfural to prepare 5-hydroxymethyl-2-furanic acid was developed. The catalyst was carbon-modified basic magnesium carbonate nanosheets. The basic magnesium carbonate nanosheets served as an inorganic basic substrate, with a carbon-modified layer in situ coated or grown on their surface. The morphology consisted of two-dimensional nanosheets with a lateral size distribution of 200-300 nm and a thickness of 15-25 nm. The layers were randomly stacked to form a loose three-dimensional porous structure.

[0009] The method for preparing the catalyst of the present invention includes the following steps:

[0010] (1) Add deionized water and anhydrous ethanol to the container, add magnesium nitrate hexahydrate under magnetic stirring, and add urea after it is completely dissolved. Stir to obtain a dissolved solution.

[0011] (2) Add glucose to the solution obtained in step (1) and continue stirring for 30-60 min to obtain a solution;

[0012] (3) Transfer the solution obtained in step (2) to a high-pressure reactor lined with polytetrafluoroethylene and react at 140~160℃ for 16~18 h; let the reactor cool naturally to room temperature, use a sand core funnel for vacuum filtration, and collect the grayish-white precipitate; wash it several times with deionized water and ethanol, and then dry it in a vacuum drying oven to obtain powder;

[0013] (4) Place the powder obtained from drying in step (3) in a tube furnace, heat it to 350~400℃ under a nitrogen atmosphere, keep it at that temperature for 60~90 min, and cool it naturally to room temperature to obtain catalyst carbon modified basic magnesium carbonate nanosheets.

[0014] In step (1), the volume ratio of deionized water to anhydrous ethanol is (1.5~2.5):1; the concentration of magnesium nitrate hexahydrate in the mixed solvent is 0.3~0.4 mol L. -1 The molar ratio of urea to magnesium nitrate hexahydrate is (4~6):1.

[0015] In step (2), the molar ratio of glucose to magnesium nitrate hexahydrate in step (1) is (0.20~0.30):1, and stirring is continued for 30~60 min;

[0016] The nitrogen heating rate in step (4) is 4.0~5.0 ℃ min. -1 .

[0017] The application of the catalyst of the present invention for the selective catalytic oxidation of 5-hydroxymethylfurfural to prepare 5-hydroxymethyl-2-furanic acid involves adding 5-hydroxymethylfurfural, N-hydroxyphthalimide, the catalyst and the reaction solvent acetonitrile to a reactor and reacting them under an oxygen atmosphere. After the reaction is completed, the reaction solution is post-treated to separate and obtain 5-hydroxymethyl-2-furanic acid.

[0018] The molar ratio of N-hydroxyphthalimide to 5-hydroxymethylfurfural is 0.05~0.15:1; the mass concentration of the catalyst in the reaction solvent is 1~1.5 g / L. -1 The initial concentration of 5-hydroxymethylfurfural in the reaction solvent was 0.2–0.5 mol / L. -1 .

[0019] The reaction is carried out under normal pressure and oxygen conditions, at a temperature of 40-50°C, for a time of 12-14 hours.

[0020] The post-processing includes: after the reaction is completed, the reaction solution is filtered or centrifuged to recover the catalyst; the obtained filtrate is concentrated under reduced pressure to recover the solvent, and then recrystallized or extracted to obtain purified 5-hydroxymethyl-2-furanic acid.

[0021] The catalyst is pre-stirred with a solution of the substrate 5-hydroxymethylfurfural before the addition of N-hydroxyphthalimide.

[0022] Compared with the prior art, the present invention has at least the following advantages:

[0023] First, this invention uses oxygen as the sole oxidant, and the reaction temperature is only 40-50℃ under normal pressure. It eliminates the need for any precious or transition metal catalysts, avoiding the high cost and metal pollution associated with precious metal catalysts (such as Ag-based catalysts) in existing technologies. Compared to the photocatalytic system disclosed in Chinese Patent CN118546113A, this invention requires no dedicated light source or photoreactor and can proceed efficiently under ordinary thermocatalytic conditions. Compared to the method in Chinese Patent CN118908917A that relies on persulfate as a strong oxidant, this invention uses only green oxygen, with water as the only byproduct, simplifying post-treatment and significantly reducing production costs and environmental impact.

[0024] Secondly, the reaction exhibits high selectivity and excellent substrate conversion. Through the synergistic catalysis of N-hydroxyphthalimide and C@Mg-NS, highly selective oxidation of 5-hydroxymethylfurfural to 5-hydroxymethyl-2-furanic acid was achieved under mild conditions. Under optimal conditions, the selectivity for 5-hydroxymethyl-2-furanic acid reached 95.1%, and the conversion rate reached 90.1%. This highly targeted synthesis of 5-hydroxymethyl-2-furanic acid was achieved without the need for strong bases or precious metals, solving the prominent problems of low target product selectivity and wide product distribution in existing technologies.

[0025] Third, the catalyst is easy to recover, simple to operate, and has a user-friendly post-treatment process. After being recycled 5 times, the conversion rate of 5-hydroxymethylfurfural by the catalyst C@Mg-NS only decreased from 90.1% to 88.0%, and the selectivity of 5-hydroxymethyl-2-furan carboxylic acid remained above 94.0% (95.1%, 95.0%, 94.5%, 94.7%, 94.1%). This solid alkali has excellent stability and recyclability.

[0026] Instruction manual illustrations

[0027] Figure 1 Schematic diagram of C@Mg-NS structure Specific implementation methods

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention. The technical solutions of the present invention are described in detail below with reference to the embodiments, but the scope of protection is not limited thereto. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] The catalyst was prepared as a solid composite base, carbon-modified basic magnesium carbonate nanosheets (C@Mg-NS). It uses basic magnesium carbonate nanosheets as an inorganic alkaline substrate, with a carbonaceous modification layer in situ coated or grown on its surface. Its morphology consists of two-dimensional nanosheets with a lateral size distribution of 200–300 nm and a thickness of 15–25 nm. The surface is slightly rough, and the layers are randomly stacked, forming a loose three-dimensional porous structure. Figure 1 As shown.

[0030] The preparation method of the catalyst C@Mg-NS includes the following steps:

[0031] (1) Add deionized water and anhydrous ethanol to the container, wherein the volume ratio of deionized water to anhydrous ethanol is (1.5~2.5):1. Add magnesium nitrate hexahydrate under magnetic stirring, wherein the concentration of magnesium nitrate hexahydrate in the mixed solvent is 0.3~0.4 mol L. -1 After it is completely dissolved, add urea. The molar ratio of urea to magnesium nitrate hexahydrate is (4~6):1. Stir until fully dissolved.

[0032] (2) Slowly add glucose to the solution obtained in step (1), with the molar ratio of glucose to magnesium nitrate hexahydrate in step (1) being (0.20~0.30):1, and continue stirring for 30~60 min;

[0033] (3) Transfer the solution obtained in step (2) to a high-pressure reactor lined with polytetrafluoroethylene and react at 140~160℃ for 16~18 h. After the reaction is completed, the reactor is naturally cooled to room temperature, and vacuum filtration is performed using a sand core funnel to collect the gray-white precipitate. Wash it several times with deionized water and ethanol, and then dry it in a vacuum drying oven to obtain powder.

[0034] (5) Place the powder obtained from drying in step (4) in a tube furnace and heat it at 4.0~5.0 ℃ min under a nitrogen atmosphere. -1 The temperature was increased to 350-400℃ at a heating rate, held for 60-90 min, and then naturally cooled to room temperature to obtain the catalyst C@Mg-NS.

[0035] The method for selectively catalytically oxidizing 5-hydroxymethylfurfural to prepare 5-hydroxymethyl-2-furanic acid using the catalyst of the present invention is as follows: 5-hydroxymethylfurfural, N-hydroxyphthalimide, C@Mg-NS and reaction solvent are added to a reactor and reacted under an oxygen atmosphere; after the reaction is completed, the reaction solution is post-treated to separate and obtain 5-hydroxymethyl-2-furanic acid.

[0036] Furthermore, the solvent is acetonitrile.

[0037] Furthermore, the molar ratio of N-hydroxyphthalimide to 5-hydroxymethylfurfural is 0.05~0.15:1; the mass concentration of the catalyst C@Mg-NS in the reaction solvent is 1~1.5 g / L. -1 The initial concentration of 5-hydroxymethylfurfural in the reaction solvent was 0.2–0.5 mol / L. -1 .

[0038] Furthermore, the catalyst C@Mg-NS is pre-stirred with a solution of the substrate 5-hydroxymethylfurfural before the addition of N-hydroxyphthalimide.

[0039] Furthermore, the reaction is carried out under normal pressure and oxygen conditions, at a temperature of 40-50°C, for a time of 12-14 hours.

[0040] The post-processing steps include: after the reaction is completed, C@Mg-NS is recovered by filtration or centrifugation; the obtained filtrate is concentrated under reduced pressure to recover the solvent, and then separated by recrystallization or extraction to obtain purified 5-hydroxymethyl-2-furanic acid; the recovered catalyst can be recycled after washing and drying.

[0041] Example 1

[0042] Catalyst preparation:

[0043] Add 40.0 mL of deionized water and 20.0 mL of anhydrous ethanol to a 100 mL beaker. Add 5.13 g of magnesium nitrate hexahydrate under magnetic stirring, and after complete dissolution, add 6.01 g of urea. Continue stirring until fully dissolved. After cooling to room temperature, slowly add 0.80 g of glucose to the beaker and stir for another 30 min. Then transfer the solution to a 100 mL polytetrafluoroethylene-lined high-pressure reactor and react at 150 °C for 18 h. After the reactor cools naturally to room temperature, vacuum filter using a sintered funnel to collect the grayish-white precipitate. Wash three times with deionized water, then three times with ethanol, and dry in a vacuum drying oven at 70 °C for 12 h. Then, place the dried powder into a tube furnace and heat at 5.0 °C for 1 min under a N2 atmosphere. -1 The temperature was increased to 350℃ at a heating rate and held for 90 min, then naturally cooled to room temperature to obtain catalyst C@Mg-NS-1.

[0044] Oxidation reaction:

[0045] Add 10 mL of acetonitrile and 5-hydroxymethylfurfural to a 25 mL two-necked flask to make the initial concentration of 5-hydroxymethylfurfural 0.2 mol L. -1 Then add 1 g L -1The C@Mg-NS-1 solution was stirred thoroughly, and then N-hydroxyphthalimide at 5 mol% relative to 5-hydroxymethylfurfural was added. Oxygen was continuously purged under normal pressure, and the reaction was carried out at 40°C for 12 h. After the reaction was completed, the mixture was filtered, and HPLC analysis showed that the conversion rate of 5-hydroxymethylfurfural was 60.5%, and the selectivity of 5-hydroxymethyl-2-furanoic acid was 92.1%.

[0046] Example 2

[0047] The catalyst used was from Example 1.

[0048] Oxidation reaction:

[0049] Add 10 mL of acetonitrile and 5-hydroxymethylfurfural to a 25 mL two-necked flask to make the initial concentration of 5-hydroxymethylfurfural 0.2 mol L. -1 Then add 1 g L -1 The C@Mg-NS-1 solution was stirred thoroughly, and then N-hydroxyphthalimide at 10 mol% relative to 5-hydroxymethylfurfural was added. Oxygen was continuously bubbled through the solution at atmospheric pressure, and the reaction was carried out at 40°C for 12 h. After the reaction, the mixture was filtered, and the filtrate was acidified for separation. HPLC analysis showed that the conversion rate of 5-hydroxymethylfurfural was 90.1%, and the selectivity of 5-hydroxymethyl-2-furanic acid was 95.1%.

[0050] Example 3

[0051] The catalyst used was from Example 1.

[0052] Oxidation reaction:

[0053] Add 10 mL of acetonitrile and 5-hydroxymethylfurfural to a 25 mL two-necked flask to make the initial concentration of 5-hydroxymethylfurfural 0.2 mol L. -1 Then add 1 g L -1 The C@Mg-NS-1 solution was stirred thoroughly, and then N-hydroxyphthalimide at 15 mol% relative to 5-hydroxymethylfurfural was added. Oxygen was continuously bubbled through the mixture at atmospheric pressure, and the reaction was carried out at 40°C for 12 h. After the reaction was completed, the mixture was filtered, and HPLC analysis showed that the conversion rate of 5-hydroxymethylfurfural was 93.5%, and the selectivity of 5-hydroxymethyl-2-furanoic acid was 85.7%.

[0054] Example 4

[0055] Catalyst preparation:

[0056] Add 40.0 mL of deionized water and 20.0 mL of anhydrous ethanol to a 100 mL beaker. Add 6.15 g of magnesium nitrate hexahydrate under magnetic stirring, and after complete dissolution, add 8.65 g of urea. Continue stirring until fully dissolved. After cooling to room temperature, slowly add 1.30 g of glucose to the beaker and stir for another 60 min. Then transfer the solution to a 100 mL polytetrafluoroethylene-lined high-pressure reactor and react at 160 °C for 16 h. After the reactor cools naturally to room temperature, vacuum filter using a sintered funnel to collect the grayish-white precipitate. Wash three times with deionized water, then three times with ethanol, and dry in a vacuum drying oven at 70 °C for 12 h. Then, place the dried powder into a tube furnace and heat at 4.0 °C for 1 min under a N2 atmosphere. -1 The temperature was increased to 400℃ at a heating rate and held for 60 min, then naturally cooled to room temperature to obtain catalyst C@Mg-NS-2.

[0057] Oxidation reaction:

[0058] Add 10 mL of acetonitrile and 5-hydroxymethylfurfural to a 25 mL two-necked flask to make the initial concentration of 5-hydroxymethylfurfural 0.5 mol L. -1 Then add 1.5 g L -1 The C@Mg-NS-2 mixture was stirred thoroughly, and then N-hydroxyphthalimide at a concentration of 10 mol% relative to 5-hydroxymethylfurfural was added. Oxygen was continuously purged under normal pressure, and the reaction was carried out at 50°C for 14 h. After the reaction was completed, the mixture was filtered, and HPLC analysis showed that the conversion rate of 5-hydroxymethylfurfural was 97.8%, and the selectivity of 5-hydroxymethyl-2-furanoic acid was 89.7%.

[0059] Example 5

[0060] Catalyst preparation:

[0061] Add 40.0 mL of deionized water and 20.0 mL of anhydrous ethanol to a 100 mL beaker. Add 6.15 g of magnesium nitrate hexahydrate under magnetic stirring, and after complete dissolution, add 8.65 g of urea. Continue stirring until fully dissolved. After cooling to room temperature, slowly add 1.30 g of glucose to the beaker and stir for another 60 min. Then transfer the solution to a 100 mL polytetrafluoroethylene-lined high-pressure reactor and react at 150 °C for 17 h. After the reactor cools naturally to room temperature, vacuum filter using a sintered funnel to collect the grayish-white precipitate. Wash three times with deionized water, then three times with ethanol, and dry in a vacuum drying oven at 70 °C for 12 h. Then, place the dried powder into a tube furnace and heat at 4.5 °C for 1 min under a N2 atmosphere. -1The temperature was increased to 375℃ at a heating rate and held for 75 min, then naturally cooled to room temperature to obtain catalyst C@Mg-NS-3.

[0062] Oxidation reaction:

[0063] Add 10 mL of acetonitrile and 5-hydroxymethylfurfural to a 25 mL two-necked flask to make the initial concentration of 5-hydroxymethylfurfural 0.4 mol / L. -1 Then add 1.5 g L -1 The C@Mg-NS-3 solution was stirred thoroughly, and then N-hydroxyphthalimide at a concentration of 10 mol% relative to 5-hydroxymethylfurfural was added. Oxygen was continuously bubbled through the mixture at atmospheric pressure, and the reaction was carried out at 50°C for 14 h. After the reaction was completed, the mixture was filtered, and HPLC analysis showed that the conversion rate of 5-hydroxymethylfurfural was 98.5%, and the selectivity of 5-hydroxymethyl-2-furanoic acid was 90.3%.

[0064] Example 6

[0065] This example demonstrates a recycling test of C@Mg-NS. Using the reaction system of Example 2, the C@Mg-NS recovered after the reaction was reused for the oxidation reaction of 5-hydroxymethylfurfural. The reaction conditions were consistent with Example 2: first use: conversion 90.1%, selectivity 95.1%; second use: conversion 89.5%, selectivity 95.0%; third use: conversion 89.0%, selectivity 94.5%; fourth use: conversion 88.7%, selectivity 94.7%; fifth use: conversion 88.0%, selectivity 94.1%. After five cycles, the conversion rate decreased by no more than 3.0%, and the selectivity remained at a high level above 94.0%, indicating that C@Mg-NS has good recycling performance.

[0066] The above description is a further detailed explanation of the present invention in conjunction with specific preferred embodiments. However, the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A catalyst for the selective catalytic oxidation of 5-hydroxymethylfurfural to prepare 5-hydroxymethyl-2-furanic acid, characterized in that, The catalyst is carbon-modified basic magnesium carbonate nanosheets. The basic magnesium carbonate nanosheets are used as an inorganic alkaline substrate, and a carbon-modified layer is coated or grown on their surface in situ. The morphology is two-dimensional nanosheets with a lateral size distribution of 200~300 nm and a thickness of 15~25 nm. The layers are randomly stacked to form a loose three-dimensional porous structure.

2. The method for preparing the catalyst according to claim 1, characterized in that, Includes the following steps: (1) Add deionized water and anhydrous ethanol to the container, add magnesium nitrate hexahydrate under magnetic stirring, and add urea after it is completely dissolved. Stir to obtain a dissolved solution. (2) Add glucose to the solution obtained in step (1) and continue stirring for 30-60 min to obtain a solution; (3) Transfer the solution obtained in step (2) to a high-pressure reactor lined with polytetrafluoroethylene and react at 140~160℃ for 16~18 h; let the reactor cool naturally to room temperature, use a sand core funnel for vacuum filtration, and collect the grayish-white precipitate; wash it several times with deionized water and ethanol, and then dry it in a vacuum drying oven to obtain powder; (4) Place the powder obtained from drying in step (3) in a tube furnace, heat it to 350~400℃ under a nitrogen atmosphere, keep it at that temperature for 60~90 min, and cool it naturally to room temperature to obtain catalyst carbon modified basic magnesium carbonate nanosheets.

3. The preparation method according to claim 2, characterized in that, In step (1), the volume ratio of deionized water to anhydrous ethanol is (1.5~2.5):1; the concentration of magnesium nitrate hexahydrate in the mixed solvent is 0.3~0.4 mol L. -1 The molar ratio of urea to magnesium nitrate hexahydrate is (4~6):

1.

4. The preparation method according to claim 2, characterized in that, In step (2), the molar ratio of glucose to magnesium nitrate hexahydrate in step (1) is (0.20~0.30):

1. Continue stirring for 30~60 min.

5. The preparation method according to claim 2, characterized in that, Step (4) The nitrogen heating rate is 4.0~5.0 ℃ min. -1 .

6. The application of the catalyst of claim 1 for the selective catalytic oxidation of 5-hydroxymethylfurfural to prepare 5-hydroxymethyl-2-furanic acid, characterized in that, 5-Hydroxymethylfurfural, N-hydroxyphthalimide, catalyst, and acetonitrile were added to a reactor and reacted under an oxygen atmosphere. After the reaction was completed, the reaction solution was post-treated to separate 5-hydroxymethyl-2-furanic acid.

7. The application as described in claim 6, characterized in that, The molar ratio of N-hydroxyphthalimide to 5-hydroxymethylfurfural is 0.05–0.15:1; the mass concentration of the catalyst in the reaction solvent is 1–1.5 g / L. -1 The initial concentration of 5-hydroxymethylfurfural in the reaction solvent was 0.2–0.5 mol / L. -1 .

8. The application as described in claim 6, characterized in that the reaction The reaction is carried out under normal pressure and oxygen conditions, at a temperature of 40-50℃, for a time of 12-14 hours.

9. The application as described in claim 6, characterized in that post-processing... include: After the reaction is complete, the catalyst is recovered by filtration or centrifugation of the reaction solution; the obtained filtrate is concentrated under reduced pressure to recover the solvent, and then purified 5-hydroxymethyl-2-furanic acid is obtained by recrystallization or extraction.

10. The application as described in claim 6, characterized in that the catalyst is pre-stirred with the substrate 5-hydroxymethylfurfural solution before the addition of N-hydroxyphthalimide.

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