Cr composite amorphous mnO2 catalyst for synthesizing fdca and preparation method and application thereof
By preparing a Cr-composite amorphous MnO2 catalyst, the problems of high cost and low efficiency in the HMF oxidation method for FDCA preparation were solved, achieving low-cost and high-efficiency FDCA production. The catalyst preparation is simple and environmentally friendly.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SOUTH CHINA UNIV OF TECH
- Filing Date
- 2023-11-22
- Publication Date
- 2026-05-19
AI Technical Summary
Existing catalysts for the HMF oxidation method to prepare FDCA are expensive and the process is complicated. Traditional precious metal catalysts are prone to environmental pollution, while non-precious metal catalysts such as MnO2 have a catalytic efficiency of less than 74%.
A Cr-composite amorphous MnO2 catalyst was prepared by reacting KMnO4 and Na2S2O3 solution to generate amorphous MnO2, which was then mixed with Cr(NO3)3 solution, ultrasonically dispersed, and calcined to form a Cr-composite amorphous MnO2 catalyst for the oxidation reaction of HMF.
The low-cost and high-efficiency conversion of HMF to FDCA was achieved. The catalyst preparation is simple, the reaction is carried out in an air atmosphere, avoiding equipment corrosion and environmental pollution, and the FDCA yield can reach 84.1%.
Smart Images
Figure CN117797808B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of FDCA synthesis, specifically relating to a Cr composite amorphous MnO2 catalyst for FDCA synthesis, its preparation method, and its application. Background Technology
[0002] 2,5-Furfurandicarboxylic acid (FDCA) can be used to obtain a wide range of unique biopolyesters. For example, the polycondensation reaction between FDCA and ethylene glycol forms polyfuran carboxylate (PEF), which is not only a green alternative to petroleum-based polyethylene terephthalate (PET), but also a multi-purpose polyester with excellent thermal stability and excellent gas barrier properties. Therefore, FDCA has become one of the key areas of focus for countries around the world.
[0003] Currently, the main routes for FDCA preparation include furoic acid disproportionation, furanylation, hexodiolic acid dehydration cyclization, diethylene glycol cyclization, and 5-hydroxymethylfurfural (HMF) oxidation. Because HMF can be prepared through the dehydration reaction of biomass-based carbohydrates, it is renewable, and the HMF oxidation reaction has high selectivity. Therefore, the HMF oxidation method has been favored by researchers and has become the preferred method for FDCA preparation, achieving a series of advancements.
[0004] Catalysts for the catalytic oxidation of hydrogen fumed hydrocarbons (HMF) can be divided into noble metal catalysts and non-noble metal catalysts. Noble metal catalysts include gold, platinum, and ruthenium. Traditional noble metal catalysts typically exhibit high HMF conversion rates and target product selectivity, but their catalytic processes often require high temperatures, high pressures, or chemical reagents as oxidants. Furthermore, metal leaching during use increases operational difficulty and exacerbates environmental pollution. Non-noble metal catalysts, such as manganese, iron, and chromium, have great application prospects in the field of selective catalytic oxidation of HMF due to their low cost, abundant reserves, and environmental friendliness. Among these, manganese oxide-based materials have attracted widespread attention in catalysis, magnetism, chemical sensing, and electrochemistry (lithium-ion batteries, supercapacitors, etc.) due to their unique physicochemical properties, including high natural abundance, low cost, environmental friendliness, diverse crystal structures, and diverse oxidation states. Manganese dioxide (MnO2) has been extensively studied as a heterogeneous catalyst for the liquid-phase selective oxidation and gas-phase total oxidation of hydrocarbons, alcohols, NO, and CO.
[0005] Reference: Hayashi E, Yamaguchi Y, Kamata K, et al. Effect of MnO2 Crystal Structure on Aerobic Oxidation of 5-Hydroxymethylfurfural to 2,5-Furandicarboxylic Acid (vol 141, pg 890, 2019) [J]. Journal of the American Chemical Society, 2019(46): 141. Different crystal forms of MnO2 were used to catalyze the synthesis of FDCA from HMF. Among them, active MnO2 had the highest catalytic efficiency, reaching 74%, which was lower than the yield of this invention. Summary of the Invention
[0006] The purpose of this invention is to address the problems existing in the prior art. This invention provides a method for synthesizing FDCA from HMF via Cr-composite amorphous MnO2 catalysis, thus solving the problems of cumbersome processes and high costs associated with traditional HMF catalyst synthesis. To achieve the above objective, the technical solution adopted by this invention is as follows.
[0007] A method for preparing a Cr-composite amorphous MnO2 catalyst for the synthesis of FDCA, comprising the following steps:
[0008] (1) KMnO4 solution and Na2S2O3 solution were mixed and stirred, and then dried to obtain amorphous MnO2;
[0009] (2) Amorphous MnO2 was added to Cr(NO3)3 solution and ultrasonically dispersed, washed and dried, and then calcined at a higher temperature to obtain Cr composite amorphous MnO2 catalyst.
[0010] Preferably, in step (1), the molar ratio of KMnO4 to Na2S2O3 is 1:1.
[0011] Preferably, in step (1), the stirring time is 12 hours.
[0012] Preferably, in step (1), the drying temperature is 60-80℃ and the drying time is 12h.
[0013] Preferably, in step (2), the mass ratio of Cr(NO3)3 to amorphous MnO2 is (0.3-0.7):1.
[0014] Preferably, in step (2), the ultrasonic dispersion time is 30 min.
[0015] Preferably, in step (2), the heating rate is 5°C / min.
[0016] Preferably, in step (2), the calcination temperature is 300°C and the calcination time is 2 hours.
[0017] This invention provides a Cr composite amorphous MnO2 catalyst for the synthesis of FDCA prepared by any of the above preparation methods.
[0018] The present invention also provides the application of the above-mentioned Cr composite amorphous MnO2 catalyst for the synthesis of FDCA in the preparation of FDCA.
[0019] Preferably, the application involves mixing an aqueous HMF solution with a NaHCO3 solution, adding the aforementioned Cr composite amorphous MnO2 catalyst, and reacting under an O2 atmosphere to obtain the compound FDCA.
[0020] More preferably, the mass ratio of HMF to NaHCO3 is (1-4):1; the mass ratio of HMF to Cr composite amorphous MnO2 catalyst is (1-4):1.
[0021] More preferably, the reaction temperature is 80-120°C, the reaction time is 4-24 hours, and the reaction pressure is 10 bar.
[0022] The beneficial effects of this invention:
[0023] Compared with traditional precious metal-based catalysts, the Cr composite amorphous MnO2 catalyst of this invention has lower cost and abundant reserves, and the reaction process does not require the addition of strong bases, thus solving the problems of equipment corrosion and environmental pollution caused by the need for strong bases in traditional catalysts.
[0024] The preparation method of the Cr composite amorphous MnO2 catalyst of the present invention is simple, can be prepared in an air atmosphere, does not require any treatment before use, is easy to use, and has a wide range of applications. Attached Figure Description
[0025] Figure 1 The image shows the electron microscope structure of the amorphous MnO2 catalyst in step 1 of Example 1.
[0026] Figure 2 The image shows the electron microscope structure of the Cr composite amorphous MnO2 catalyst in Example 1.
[0027] Figure 3 The HMF conversion rate and FDCA yield are given in Example 1.
[0028] Figure 4 The HMF conversion rate and FDCA yield are given in Example 2.
[0029] Figure 5The HMF conversion rate and FDCA yield are given in Example 3.
[0030] Figure 6 The HMF conversion rate and FDCA yield are given in Example 4.
[0031] Figure 7 The conversion rate of HMF and the yield of FDCA in Example 5 are given.
[0032] Figure 8 The HMF conversion rate and FDCA yield are given in Example 6. Detailed Implementation
[0033] The embodiments of the present invention employ the following scheme to prepare Cr composite amorphous MnO2 catalyst and apply it to the preparation of FDCA.
[0034] 1. Preparation of amorphous MnO2
[0035] A 0.1 mol / L KMnO4 solution and a 0.1 mol / L Na2S2O3 solution were mixed in a 250 mL volumetric flask and stirred continuously with a magnetic stirrer for 12 h. The mixture was then filtered and washed until neutral to obtain a black precipitate. The black precipitate was dried in an oven at 60-80 °C and then pulverized to obtain amorphous MnO2. In some embodiments, the drying temperature of the black precipitate was 80 °C and the drying time was 12 h.
[0036] 2. Preparation of Cr-composite amorphous MnO2 catalyst
[0037] The raw materials were prepared by dissolving Cr(NO3)3 in an appropriate amount of water and adding the amorphous MnO2. The mixture was ultrasonically dispersed for 30 min, then filtered and washed three times. The precipitate was dried in an oven at 60-80℃ and then calcined in a muffle furnace in air at a heating rate of 5℃ / min from room temperature to 300℃, held at this temperature for 2 h, and then cooled to room temperature to obtain the Cr composite amorphous MnO2 catalyst. In some embodiments, the mass ratio of Cr(NO3)3 to amorphous MnO2 was (0.4-0.6):1; the precipitate drying temperature was 80℃ and the drying time was 12 h.
[0038] 3. Catalytic oxidation of HMF to prepare FDCA using Cr-composite amorphous MnO2 catalyst
[0039] HMF and NaHCO3 were dissolved in deionized water and transferred to a reaction vessel. A Cr-based amorphous MnO2 catalyst was added, and the mixture was reacted at 80–110°C for 4–24 h under an O2 atmosphere to obtain the compound FDCA. In some embodiments, the mass ratio of HMF, NaHCO3, and Cr-based amorphous MnO2 catalyst was 1:2–3:2–4; 10–20 ml of deionized water was used; the O2 pressure was 10 bar; the reaction temperature was 110°C; and the reaction time was 12 h.
[0040] Example 1
[0041] Step 1: Dissolve 1.58 g of KMnO4 and 1.58 g of Na2S2O3 in 100 ml of deionized water, and transfer the solutions to 100 ml volumetric flasks to obtain 0.1 mol / L KMnO4 and 0.1 mol / L Na2S2O3 solutions, respectively. Mix the two solutions thoroughly in a 250 ml volumetric flask and stir continuously with a magnetic stirrer for 12 h. Filter the amorphous MnO2 suspension prepared by the oxidation reaction of KMnO4 and Na2S2O3, wash the resulting precipitate until neutral, and then dry it in an oven at 80 °C for 12 h. After drying, grind the solid into powder to obtain amorphous MnO2 powder. The electron microscopy structure of the amorphous MnO2 powder is shown below. Figure 1 As shown. From Figure 1 It can be seen that amorphous MnO2 presents as aggregates of MnO2 particles. The specific surface area of amorphous MnO2 is shown in Table 1.
[0042] Step 2: Dissolve 0.3-0.7 g of Cr(NO3)3 in 10 ml of deionized water. Add 1 g of amorphous MnO2 powder to the Cr(NO3)3 solution and ultrasonically disperse for 30 min. Then filter and wash three times. Dry the precipitate in an 80℃ oven for 12 h. After drying, place the powder in a muffle furnace and calcine it in air at a heating rate of 5℃ / min from room temperature to 300℃, maintain this temperature for 2 h, and cool to room temperature. This yields the Cr composite amorphous MnO2 catalyst with a Cr(NO3)3 to amorphous MnO2 mass ratio of (0.3-0.7):1. The electron microscopy structure of the Cr composite amorphous MnO2 catalyst with a Cr(NO3)3 to amorphous MnO2 mass ratio of 0.5:1 is shown in the figure. Figure 2 As shown. From Figure 2It can be seen that after Cr is doped into amorphous MnO2, the aggregates become more dispersed and their size tends to be uniform. This unique structure endows the particles with high specific surface area and good catalytic performance. Table 1 shows the specific surface area of the Cr-coated amorphous MnO2 catalyst with a mass ratio of 0.5:1 (Cr(NO3)3:Amorphous MnO2). The specific surface area of the Cr-coated amorphous MnO2 catalyst is significantly larger than that of amorphous MnO2, proving that Cr loading effectively increases the specific surface area of the catalyst, which is beneficial to improving catalytic efficiency. Simultaneously, because Cr is loaded on the surface of amorphous MnO2, it reduces the pore volume and pore size to some extent.
[0043] Step 3: Dissolve 25 mg HMF and 50 mg NaHCO3 in 20 ml of deionized water, transfer to a reaction vessel, add 100 mg Cr composite amorphous MnO2 catalyst, introduce 10 bar O2, and react at 110 °C for 12 h. Test the HMF conversion and FDCA yield under different mass ratios of Cr(NO3)3 and amorphous MnO2.
[0044] After the reaction was complete, all products were identified by liquid chromatography, and the results are listed below. Figure 3 .from Figure 3 As can be seen, when the mass ratio of Cr(NO3)3 to amorphous MnO2 increases from 0.3:1 to 0.5:1, the FDCA yield increases from 69.7% to 84.1%. When the mass ratio of Cr(NO3)3 to amorphous MnO2 is greater than 0.5:1, the FDCA yield begins to decrease. Therefore, the catalyst efficiency is optimal when the mass ratio of Cr(NO3)3 to amorphous MnO2 is 0.5:1.
[0045] Comparative Example 1
[0046] The amorphous MnO2 obtained in Example 1 was directly used to catalyze HMF, and the results are listed below. Figure 3 .from Figure 3 As can be seen, when the catalyst is only amorphous MnO2, the FDCA yield is only 46.8%, which is much lower than that of the Cr composite amorphous MnO2 catalyst.
[0047] Table 1
[0048]
[0049] Example 2:
[0050] Step 1: Dissolve 1.58 g of KMnO4 and 1.58 g of Na2S2O3 in 100 ml of deionized water, respectively, and transfer the solutions to 100 ml volumetric flasks to obtain 0.1 mol / L KMnO4 and 0.1 mol / L Na2S2O3 solutions. Mix the two solutions thoroughly in a 250 ml volumetric flask and stir continuously with a magnetic stirrer for 12 h. Filter the amorphous MnO2 suspension prepared by the oxidation reaction of KMnO4 and Na2S2O3, wash the resulting precipitate until neutral, and then dry it in an oven at 80 °C for 12 h. After drying, grind the solid into powder to obtain amorphous MnO2 powder.
[0051] Step 2: Dissolve 0.5g of Cr(NO3)3 in 10ml of deionized water. Add 1g of amorphous MnO2 powder to the Cr(NO3)3 solution and ultrasonically disperse for 30min. Then filter and wash three times. Dry the precipitate in an 80℃ oven for 12h. After drying, place the powder in a muffle furnace and calcine it in air at a heating rate of 5℃ / min from room temperature to 300℃, and maintain this temperature for 2h. After cooling to room temperature, remove the powder to obtain the Cr composite amorphous manganese dioxide catalyst. The mass ratio of Cr(NO3)3 to amorphous MnO2 in this catalyst is 0.5:1.
[0052] Step 3: Dissolve 25 mg HMF and 50 mg NaHCO3 in 20 ml of deionized water, transfer to a reaction vessel, add 100 mg Cr composite amorphous MnO2 catalyst, introduce 10 bar O2, and react at 110 °C for 4-24 h.
[0053] After the reaction was complete, all products were identified by liquid chromatography, and the results are listed below. Figure 4 .from Figure 4 As can be seen, the FDCA yield increased rapidly from 61.1% to 84.1% when the reaction time increased from 4 h to 12 h. After the reaction time reached 12 h, the increase in FDCA yield slowed down, reaching a peak of 87.9% at 20 h. When the reaction time was further extended to 24 h, the FDCA yield decreased.
[0054] Example 3:
[0055] Step 1: Dissolve 1.58 g of KMnO4 and 1.58 g of Na2S2O3 in 100 ml of deionized water, respectively, and transfer the solutions to 100 ml volumetric flasks to obtain 0.1 mol / L KMnO4 and 0.1 mol / L Na2S2O3 solutions. Mix the two solutions thoroughly in a 250 ml volumetric flask and stir continuously with a magnetic stirrer for 12 h. Filter the amorphous MnO2 suspension prepared by the oxidation reaction of KMnO4 and Na2S2O3, wash the resulting precipitate until neutral, and then dry it in an oven at 80 °C for 12 h. After drying, grind the solid into powder to obtain amorphous MnO2 powder.
[0056] Step 2: Dissolve 0.6g of Cr(NO3)3 in 10ml of deionized water. Add 1g of amorphous MnO2 powder to the Cr(NO3)3 solution and ultrasonically disperse for 30min. Then filter and wash three times. Dry the precipitate in an 80℃ oven for 12h. After drying, place the powder in a muffle furnace and calcine it in air at a heating rate of 5℃ / min from room temperature to 300℃, and maintain this temperature for 2h. After cooling to room temperature, remove the powder to obtain the Cr composite amorphous MnO2 catalyst. The mass ratio of Cr(NO3)3 to amorphous MnO2 in this catalyst is 0.6:1.
[0057] Step 3: Dissolve 25 mg HMF and 50 mg NaHCO3 in 20 ml of deionized water, transfer to a reaction vessel, add 100 mg Cr composite amorphous MnO2 catalyst, introduce 10 bar O2, and react at 80-120℃ for 12 h.
[0058] After the reaction was complete, all products were identified by liquid chromatography, and the results are listed below. Figure 5 As can be seen from the figure, the HMF conversion rate reaches 98% at 80℃. With the increase of reaction temperature, the HMF conversion rate only increases slightly. The FDCA yield increases significantly with the increase of temperature, reaching a maximum of 84.1% at 110℃, and then begins to decline.
[0059] Example 4:
[0060] Step 1: Dissolve 1.58 g of KMnO4 and 1.58 g of Na2S2O3 in 100 ml of deionized water, respectively, and transfer the solutions to 100 ml volumetric flasks to obtain 0.1 mol / L KMnO4 and 0.1 mol / L Na2S2O3 solutions. Mix the two solutions thoroughly in a 250 ml volumetric flask and stir continuously with a magnetic stirrer for 12 h. Filter the amorphous MnO2 suspension prepared by the oxidation reaction of KMnO4 and Na2S2O3, wash the resulting precipitate until neutral, and then dry it in an oven at 80 °C for 12 h. After drying, grind the solid into powder to obtain amorphous MnO2 powder.
[0061] Step 2: Dissolve 0.5g of Cr(NO3)3 in 10ml of deionized water. Add 1g of amorphous MnO2 powder to the Cr(NO3)3 solution and ultrasonically disperse for 30min. Then filter and wash three times. Dry the precipitate in an 80℃ oven for 12h. After drying, place the powder in a muffle furnace and calcine it in air at a heating rate of 5℃ / min from room temperature to 300℃, and maintain this temperature for 2h. After cooling to room temperature, remove the powder to obtain the Cr composite amorphous MnO2 catalyst. The mass ratio of Cr(NO3)3 to amorphous MnO2 in this catalyst is 0.5:1.
[0062] Step 3: Dissolve 25 mg HMF and NaHCO3 (mass ratio of HMF 1:1 to 4) in 20 ml of deionized water, transfer to a reaction vessel, add 100 mg Cr composite amorphous MnO2 catalyst, introduce 10 bar O2, and react at 110 °C for 12 h.
[0063] After the reaction was complete, all products were identified by liquid chromatography, and the results are listed below. Figure 6 As shown in the figure, the FDCA yield increased to 84.1% when the mass ratio of HMF to NaHCO3 increased from 1:1 to 1:2. Higher alkaline conditions accelerated the degradation of HMF and hindered FDCA formation; therefore, the FDCA yield decreased from a high of 84.1% to 55% when the mass ratio of HMF to NaHCO3 increased from 1:2 to 1:4.
[0064] Example 5:
[0065] Step 1: Dissolve 1.58 g of KMnO4 and 1.58 g of Na2S2O3 in 100 ml of deionized water, respectively, and transfer the solutions to 100 ml volumetric flasks to obtain 0.1 mol / L KMnO4 and 0.1 mol / L Na2S2O3 solutions. Mix the two solutions thoroughly in a 250 ml volumetric flask and stir continuously with a magnetic stirrer for 12 h. Filter the amorphous MnO2 suspension prepared by the oxidation reaction of KMnO4 and Na2S2O3, wash the resulting precipitate until neutral, and then dry it in an oven at 80 °C for 12 h. After drying, grind the solid into powder to obtain amorphous MnO2 powder.
[0066] Step 2: Dissolve 0.5g of Cr(NO3)3 in 10ml of deionized water. Add 1g of amorphous MnO2 powder to the Cr(NO3)3 solution and ultrasonically disperse for 30min. Then filter and wash three times. Dry the precipitate in an 80℃ oven for 12h. After drying, place the powder in a muffle furnace and calcine it in air at a heating rate of 5℃ / min from room temperature to 300℃, and maintain this temperature for 2h. After cooling to room temperature, remove the powder to obtain the Cr composite amorphous MnO2 catalyst. The mass ratio of Cr(NO3)3 to amorphous MnO2 in this catalyst is 0.5:1.
[0067] Step 3: Dissolve 25 mg HMF and 50 mg NaHCO3 in 20 ml of deionized water, transfer to a reaction vessel, add a Cr composite amorphous MnO2 catalyst with a mass ratio of 1:1 to 4 HMF, introduce 10 bar O2, and react at 110 °C for 12 h.
[0068] After the reaction was complete, all products were identified by liquid chromatography, and the results are listed below. Figure 7 As shown in the figure, when the mass ratio of HMF to catalyst is 1:1, HMF is almost completely converted, but the yield of FDCA is only 40.2%. When the mass ratio of HMF to catalyst increases from 1:1 to 1:4, the yield of FDCA increases significantly to 84.1%, indicating that when the mass ratio of HMF to catalyst is 1:4, the active sites provided by the catalyst are sufficient to convert all HMF into FDCA.
[0069] Example 6:
[0070] Step 1: Dissolve 1.58 g of KMnO4 and 1.58 g of Na2S2O3 in 100 ml of deionized water, respectively, and transfer the solutions to 100 ml volumetric flasks to obtain 0.1 mol / L KMnO4 and 0.1 mol / L Na2S2O3 solutions. Mix the two solutions thoroughly in a 250 ml volumetric flask and stir continuously with a magnetic stirrer for 12 h. Filter the amorphous MnO2 suspension prepared by the oxidation reaction of KMnO4 and Na2S2O3, wash the resulting precipitate until neutral, and then dry it in an oven at 80 °C for 12 h. After drying, grind the solid into powder to obtain amorphous MnO2 powder.
[0071] Step 2: Dissolve 0.5g of Cr(NO3)3 in 10ml of deionized water. Add 1g of amorphous MnO2 powder to the Cr(NO3)3 solution and ultrasonically disperse for 30min. Then filter and wash three times. Dry the precipitate in an 80℃ oven for 12h. After drying, place the powder in a muffle furnace and calcine it in air at a heating rate of 5℃ / min from room temperature to 300℃, and maintain this temperature for 2h. After cooling to room temperature, remove the powder to obtain the Cr composite amorphous MnO2 catalyst. The mass ratio of Cr(NO3)3 to amorphous MnO2 in this catalyst is 0.5:1.
[0072] Step 3: Dissolve 25 mg HMF and 50 mg NaHCO3 in 20 ml of deionized water, transfer to a reaction vessel, add 100 mg Cr composite amorphous MnO2 catalyst, introduce 10 bar O2, and react at 110 °C for 12 h.
[0073] The catalyst was recovered by filtration after 12 hours of reaction, washed several times with deionized water, and then reused three more times following step 3 above. After the reaction was completed, all products were identified by liquid chromatography, and the results are listed below. Figure 8 As can be seen from the figure, the FDCA yield decreased by only 7.9% during the four cycles, indicating that the catalyst has good stability.
[0074] The formulas for calculating HMF conversion rate and FDCA yield in this invention are as follows:
[0075]
[0076]
[0077] Where, n HMF反应前 n is the amount of HMF in the reaction system before the reaction begins. HMF反应后 n represents the amount of HMF in the reaction system after the reaction is complete. FDCA反应前 n is the amount of HMF in the reaction system before the reaction begins. FDCA反应后This represents the amount of HMF in the reaction system after the reaction is complete.
[0078] The above embodiments are merely preferred embodiments of the present invention and are only used to explain the present invention, not to limit the present invention. Any changes, substitutions, modifications, etc., made by those skilled in the art without departing from the spirit and essence of the present invention should be within the protection scope of the present invention.
Claims
1. The application of a Cr-composite amorphous MnO2 catalyst for the synthesis of FDCA in the preparation of FDCA; characterized in that, The application involves mixing an aqueous HMF solution with a NaHCO3 solution, adding a Cr-based composite amorphous MnO2 catalyst, and reacting under an O2 atmosphere to obtain the compound FDCA. The preparation steps of the Cr-based composite amorphous MnO2 catalyst used for the synthesis of FDCA are as follows: (1) KMnO4 solution and Na2S2O3 solution are mixed and stirred, and dried to obtain amorphous MnO2; the molar ratio of KMnO4 to Na2S2O3 is 1:1, the stirring time is 12h, the drying temperature is 60-80℃, and the drying time is 12h. (2) Amorphous MnO2 was added to a Cr(NO3)3 solution and ultrasonically dispersed, washed and dried, and then calcined at a higher temperature to obtain a Cr composite amorphous MnO2 catalyst; the mass ratio of Cr(NO3)3 to amorphous MnO2 was (0.3-0.7):1; the calcination temperature was 300℃; and the calcination time was 2h.
2. The application according to claim 1, characterized in that, In step (2), the ultrasonic dispersion time is 30 min.
3. The application according to claim 1, characterized in that, In step (2), the heating rate is 5°C / min.
4. The application according to claim 1, characterized in that, The mass ratio of HMF to NaHCO3 is (1-4):1; the mass ratio of HMF to Cr composite amorphous MnO2 catalyst is (1-4):
1.
5. The application according to claim 1, characterized in that, The reaction temperature is 80-120℃, the reaction time is 4-24h, and the reaction pressure is 10 bar.