RuCu-loaded diatomic catalyst as well as preparation method and application thereof

Abstract

The invention discloses a RuCu-loaded dual-atom catalyst and a preparation method and application thereof, and belongs to the technical field of catalysts and organic synthesis.The RuCu-loaded dual-atom catalyst is obtained by mixing a nitrogen-doped porous carbon material prepared from a nitrogen-containing porous organic polymer and nano calcium carbonate with an active component RuCu dual-precursor and carrying out ball milling, calcination and reduction. The supported RuCu diatom catalyst prepared by the method is high in activity and relatively long in service life and stability, efficient preparation of an FDCA product from a 5-hydroxymethylfurfural crude product is realized by flexibly regulating and controlling the ratio of RuCu diatoms and under the synergistic effect of the RuCu diatoms, and meanwhile, three wastes and energy consumption are reduced; the recovered catalyst can be repeatedly used after being simply washed with ethanol and dried, and the performance is not obviously reduced during recycling.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysts and organic synthesis, and specifically relates to a loaded RuCu diatomic catalyst and a preparation method and application thereof. Background Art

[0002] As people pay more and more attention to sustainable development, researchers have conducted extensive explorations on renewable resources. Among them, 2,5-furandicarboxylic acid (FDCA) is a high-value-added biological and chemical substance, which is considered by experts to be an important candidate for sustainable chemicals to replace existing petrochemicals. It has broad application prospects in polyester plastics, coatings, fiber fabrics and other fields. Compared with traditional petrochemicals, FDCA has lower carbon emissions, better degradability and a wider range of resource sources. Seeking a green, efficient and low-cost method to prepare FDCA has gradually become a hot issue.

[0003] At present, the catalytic oxidation of 5-hydroxymethylfurfural to prepare 2,5-furandicarboxylic acid is an efficient and environmentally friendly biomass raw material route. The catalysts used for catalytic oxidation can be divided into precious metal catalysts and non-precious metal catalysts. Precious metal catalysts include gold, platinum, ruthenium, etc. Traditional precious metal catalysts usually show high HMF conversion rate and target product selectivity, but the use of large doses undoubtedly increases the catalyst cost, and the metal is easy to leach and deactivate during use, which increases the difficulty of operation and is not conducive to large-scale application in industrial production; non-precious metal catalysts such as manganese, iron, vanadium, copper, etc., due to their low price and abundant reserves, they have received a lot of attention in the catalytic oxidation of HMF, but these non-precious metal-based catalysts have problems such as long reaction time, harsh conditions, large catalyst dosage, high separation difficulty, and poor recyclability.

[0004] Single atom catalysts (SACs) not only have the advantages of atomic dispersion and high atomic utilization of homogeneous catalysts, but also have the advantages of stability and easy separation of heterogeneous catalysts. They are the bridge connecting homogeneous catalysis and heterogeneous catalysis. Single atom catalysts have attracted extensive attention in the fields of electrocatalysis, photocatalysis, fine chemical synthesis and fuel cells due to their high catalytic activity, high selectivity and high stability. Therefore, in order to maximize the catalytic efficiency of precious metals and reduce manufacturing costs, the preparation of single atom metal catalysts has become the first choice for researchers. Patent CN108435230B discloses a heteroatom-doped ordered mesoporous carbon supported by Ru as an active component, SBA-15 and a phenolic resin-ethanol solution with a mass fraction of 20% and triphenyl phosphate to prepare a heteroatom-doped ordered mesoporous carbon as a carrier, and the catalyst is impregnated and loaded to form a heteroatom-doped ordered mesoporous carbon supported ruthenium catalyst, which is used to efficiently catalyze 5-hydroxymethylfurfural to 2,5-furandicarboxaldehyde. Patent CN113117706B discloses a metal-modified ruthenium-based catalyst and a method for preparing 2,5-furandicarboxylic acid by catalysis thereof, using hydroxyapatite as a carrier and Ru 3+ As the active component, metal oxides of zirconium, iron and / or zinc are used as the modified component to catalyze the oxidation of 5-methoxymethylfurfural to 2,5-furandicarboxylic acid. As the modified component, the metal oxide well regulates the electron cloud around the ruthenium atom, and synergizes with the hydroxyl group on the carrier apatite to promote the activation of the aldehyde group CH of the furan ring side chain, thereby increasing the Ru 3+ The oxidation capacity of NiFe LDH is good, but the reaction time is 12h to 24h, and the reaction cycle is too long, which is not conducive to rapid industrial production. Patent application CN117535714A discloses a preparation method and application of NiFe LDH loaded single-atom Ru catalyst, the preparation method is to mix Ni(NO3)2·6H2O, Fe(NO3)3·6H2O and nickel foam, use nickel foam as working electrode, Ag / AgCl electrode as reference electrode, and graphite rod as counter electrode to form a three-electrode system for electrodeposition, and wash and dry to obtain NiFe LDH loaded single-atom Ru catalyst, which promotes HMF conversion rate close to 100% and FDCA productivity of 96.2%, but the electrocatalytic oxidation process usually consumes a lot of electricity to maintain the electrode reaction. During long-term use, the electrode may cause performance degradation due to surface contamination, corrosion, passivation and other reasons, shortening the service life of the electrode and affecting the catalytic activity and stability of the electrode. Summary of the invention

[0005] The invention provides a supported RuCu diatomic catalyst and a preparation method and application thereof. The prepared supported RuCu diatomic catalyst has high activity, a long service life and good stability, no obvious decrease in catalyst performance during cyclic use, and low total preparation cost.

[0006] To achieve the above objectives, the present invention adopts the following technical solutions: A method for preparing a supported RuCu diatomic catalyst comprises the following steps: S1. Preparation of nitrogen-containing porous organic polymer: 2,5-furandicarboxaldehyde, melamine and N,N-dimethylacetamide solvent are added to a reaction kettle, stirred to dissolve, then heated to 160°C, reacted for 3 hours, naturally cooled to room temperature, and then the obtained mixed solution was added to water, stirred to precipitate solid, washed with ethanol 3 times, and vacuum dried to remove the remaining solvent to obtain a nitrogen-containing porous organic polymer; S2. Preparation of nitrogen-doped porous carbon materials: The prepared nitrogen-containing porous organic polymer and nano-calcium carbonate are mixed and transferred to a tubular furnace quartz ark, and the mixture is heated to 800°C at a rate of 5°C / min in an inert gas atmosphere for 2 hours to cause the calcium carbonate to decompose under heat to generate calcium oxide and carbon dioxide. Calcium oxide can play a similar role as a hard template. The generated carbon dioxide reacts with the nitrogen-containing porous organic polymer through an oxidation-reduction process under the appropriate conditions of nitrogen and catalyst in the system at high temperature to generate nitrogen oxides. Some electron-rich nitrogen-containing sites are attacked by nitrogen oxides, causing the structure and properties of the polymer to change, thereby further promoting the formation of a porous structure; the template is then removed by etching with a 10% hydrochloric acid solution, and the solution is washed with deionized water until the pH of the clear solution is close to neutral, and then dried in an oven at 110°C to obtain a nitrogen-doped porous carbon material; S3. Loading RuCu diatomic catalyst: adding precious metal Ru salt, non-precious metal Cu salt and alcohol amine to nitrogen-doped porous carbon material, crushing it by ball milling, and then heating to 200-400°C at a rate of 5°C / min in a mixed gas of hydrogen and nitrogen and calcining for 2h to obtain RuCu diatomic catalyst.

[0007] In the above steps, the molar ratio of 2,5-furandicarboxaldehyde, melamine and N,N-dimethylacetamide in S1 is (1-3):1:5; The mass ratio of the nitrogen-containing porous organic polymer to the nano-calcium carbonate in S2 is 1:1, wherein the particle size of the nano-calcium carbonate is preferably 50-100 nm; The inert gas atmosphere is one of nitrogen, argon and nitrogen; The Ru salt in S3 is ruthenium chloride trihydrate, and the Cu salt is one or more of copper nitrate trihydrate, copper chloride, copper acetate, and copper sulfate; The total amount of Ru and Cu loaded is 5% to 10% by mass, wherein the amount of Ru loaded is 0.5% to 5%, and the amount of Cu loaded is 0.5% to 5%; The amount of the alcoholamine is 0.01% to 0.04% of the mass of the nitrogen-doped porous carbon material, preferably 0.03%; the alcoholamine is at least one of triethanolamine, triisopropanolamine, and diethanol monoisopropanolamine, preferably triisopropanolamine; because the particles of the noble metal Ru salt, the non-noble metal Cu salt, and the nitrogen-doped porous carbon material are gradually refined and the specific surface area increases during the ball milling process, the surface is charged due to bond breaking, the particles adsorb each other and agglomerate, and the crushing efficiency decreases. Adding a small amount of triisopropanolamine, which is preferably used, can prevent particle agglomeration and improve material fluidity, thereby improving ball milling efficiency, shortening grinding time, and more effectively promoting the uniform distribution of Ru and Cu; The ball mill speed is 360r / min, the crushing time is 3-5min, and the mass ratio of grinding balls to samples is 8:1; The volume ratio of hydrogen to nitrogen in the hydrogen and nitrogen mixed gas is (1-3):1, preferably 1:1.

[0008] The prepared RuCu diatomic catalyst has a carrier of nitrogen-doped porous carbon, and Ru and Cu are uniformly distributed on the surface of the carrier in a single-atom manner.

[0009] The method for preparing 2,5-furandicarboxylic acid by oxidation of crude 5-hydroxymethylfurfural using the supported RuCu diatomic catalyst specifically comprises the following steps: The crude 5-hydroxymethylfurfural, the loaded RuCu diatomic catalyst, the alkali solution and the oxygen source are contacted, the reaction temperature is 100°C to 150°C, the reaction pressure is 0.3 to 3.0 MPa, the reaction time is 0.5 to 8 hours, and 2,5-furandicarboxylic acid is efficiently catalytically oxidized and synthesized.

[0010] The reaction temperature is preferably 100-120°C, and the reaction pressure is preferably 0.5-2.5MPa; The alkaline aqueous solution is one or more of potassium hydroxide aqueous solution, sodium hydroxide aqueous solution, potassium carbonate aqueous solution, and sodium carbonate aqueous solution; preferably sodium carbonate aqueous solution, with a volume concentration of 10% to 20%; it can promote the dissolution of 2,5-furandicarboxylic acid prepared by catalytic oxidation in the aqueous solution to prevent precipitation, so as to separate and recover the product from the catalyst in the later stage; The oxygen source is one or more of oxygen, air, hydrogen peroxide, and sodium hypochlorite; The mass proportion of the crude 5-hydroxymethylfurfural raw material in the reaction system is 5% to 20%, and the molar ratio of 5-hydroxymethylfurfural to alkali is 1:(1-2), preferably 1:1.3; wherein the main content of 5-hydroxymethylfurfural in the crude product is ≥65%; The amount of the supported RuCu diatomic catalyst is 0.3%-1.0% of the total mass of the crude 5-hydroxymethylfurfural and the alkali solution, preferably 0.5%.

[0011] Beneficial effects: The present invention provides a RuCu-loaded diatomic catalyst and a preparation method and application thereof, which have the following advantages over the prior art: 1. The present invention provides a catalyst for preparing 2,5-furandicarboxylic acid by oxidizing crude 5-hydroxymethylfurfural, which is obtained by mixing a nitrogen-doped porous carbon material as a carrier with an active component RuCu dual precursor, ball milling, calcination and reduction. The active component RuCu is highly dispersed and evenly distributed on the carrier surface in a single-atom manner by first preparing a nitrogen-containing porous organic polymer and then obtaining a nitrogen-doped porous carbon material, and can effectively prevent RuCu from agglomerating or losing, thereby further improving its catalytic performance; 2. In the process of ball milling of the noble metal Ru salt, the non-noble metal Cu salt and the nitrogen-doped porous carbon material, the present invention introduces a very small amount of alcohol amine as a grinding aid, which effectively prevents the particles from being gradually refined and charged due to the increase in specific surface area, thereby avoiding the mutual adsorption and agglomeration of particles, which not only improves the material fluidity, but also improves the ball milling efficiency, shortens the grinding time, and more effectively promotes the uniform distribution of Ru and Cu; 3. The raw materials used to prepare the catalyst in the present invention are generally inexpensive, and the ratio of the bimetallic Ru and Cu can be flexibly adjusted. Under the synergistic effect of the Ru and Cu diatoms, 5-hydroxymethylfurfural crude products can be efficiently used to prepare 2,5-furandicarboxylic acid, while reducing three wastes and energy consumption; 4. The catalyst prepared by the present invention is not easy to deactivate. The catalyst after centrifugal separation can be reused many times after simple washing with ethanol and drying. There is no obvious decline in performance during the cyclic use. The obtained catalyst has a long service life and good stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a SEM image of the nitrogen-doped porous carbon material in an embodiment of the present invention; Figure 2 is a nitrogen isothermal adsorption-desorption curve diagram of the nitrogen-doped porous carbon material in an embodiment of the present invention; Figure 3 It is a performance curve diagram of catalyst recycling in an embodiment of the present invention. DETAILED DESCRIPTION

[0013] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments: Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0014] The following Agilent 1260 high performance liquid chromatograph was used to analyze the products in the oxidation of 5-hydroxymethylfurfural to prepare 2,5-furandicarboxylic acid, and the external standard method was used for quantification; the SEM image of the nitrogen-doped porous carbon material was measured by a Hitachi S-4800 scanning electron microscope (SEM) instrument, and the nitrogen isotherm adsorption-desorption curve was measured by a NOVA2000e fully automatic specific surface and pore analyzer produced by Quantachrome Inc., USA.

[0015] The crude 5-hydroxymethylfurfural used below is the reaction product of hexabasic sugar under a strong acid catalyst. The crude product is obtained by simple separation to remove water-soluble impurities and then removing the organic solvent. The main content of the crude product in the reaction solution is ≥65% as determined by liquid chromatography.

[0016] The conversion rate and yield calculation in the reaction of 5-hydroxymethylfurfural oxidation to prepare 2,5-furandicarboxylic acid is obtained by converting the effective content of crude 5-hydroxymethylfurfural; the conversion rate, yield and product purity in the reaction of 5-hydroxymethylfurfural oxidation to prepare 2,5-furandicarboxylic acid are calculated as follows: , , . Example 1

[0017] Preparation of supported bimetallic single atom catalysts (1) Preparation of nitrogen-containing porous organic polymer: 49.6 g (0.4 mol) of 2,5-furandicarboxaldehyde, 25.2 (0.2 mol) of melamine and 87 g (1 mol) of N,N-dimethylacetamide solvent were added to a stainless steel autoclave, stirred to dissolve, then heated to 160 °C and reacted for 3 h. After naturally cooling to room temperature, the resulting mixture was added to water and stirred to precipitate solids, which were washed with ethanol three times and vacuum dried to remove the remaining solvent to obtain 74 g of nitrogen-containing porous organic polymer. (2) Preparation of nitrogen-doped porous carbon material: 74 g of the prepared nitrogen-containing porous organic polymer and 74 g of nano-calcium carbonate were mixed and transferred to a tubular furnace quartz ark, and the mixture was heated to 800 °C at a rate of 5 °C / min in an inert atmosphere for 2 h. The template was then etched away with a 10% hydrochloric acid solution, and the mixture was washed with deionized water until the pH of the clear solution was close to neutral. The mixture was then dried in an oven at 110 °C to obtain 123 g of nitrogen-doped porous carbon material. (3) Loading bimetallic single atoms: 2.46 g (2 wt%) of ruthenium chloride trihydrate, 4.92 (4 wt%) of copper nitrate trihydrate and 0.037 g (0.03 wt%) of triisopropanolamine were added to the nitrogen-doped porous carbon material, crushed by ball milling, and then calcined at 200-400 °C at a rate of 5 °C / min in a tubular furnace under a mixture of hydrogen and nitrogen for 2 h to obtain a RuCu biatomic catalyst (NCP-24).

[0018] The SEM image of the nitrogen-doped porous carbon material prepared above is as follows: Figure 1 As shown in Figure 2, it can be seen that the porous structure of nitrogen-doped porous carbon materials can make the active component RuCu highly dispersed and evenly distributed on the carrier surface in a single-atom manner, and can effectively prevent the agglomeration or loss of RuCu; the nitrogen isothermal adsorption-desorption curve of nitrogen-doped porous carbon materials is shown in Figure 2. Figure 2 As shown in Table 1, the pore structure parameters of nitrogen-doped porous carbon materials were calculated based on the nitrogen isothermal adsorption-desorption curve.

[0019] Table 1 Pore structure parameters of nitrogen-doped porous carbon materials Example 2

[0020] According to the preparation method of Example 1, ruthenium chloride trihydrate is 3wt% and copper nitrate trihydrate is 2wt%, recorded as NCP-32. Example 3

[0021] According to the preparation method of Example 1, ruthenium chloride trihydrate is 1wt%, and copper nitrate trihydrate is 5wt%, and it is recorded as NCP-15. Example 4

[0022] According to the preparation method of Example 1, ruthenium chloride trihydrate is 0.5wt% and copper nitrate trihydrate is 6wt%, recorded as NCP-056.

[0023] Comparative Example 1 The preparation method of Example 1 was followed, except that copper nitrate trihydrate was not added in step (3), and ruthenium chloride trihydrate was 2 wt %, denoted as NCP-20.

[0024] Comparative Example 2 According to the preparation method of Example (1), no ruthenium chloride trihydrate is added in step 3, and the copper nitrate trihydrate is 5 wt %, which is recorded as NCP-05. Example 5

[0025] Application of catalyst in oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid 97.01g (0.5mol) of crude 5-hydroxymethylfurfural (the content of 5-hydroxymethylfurfural in the crude product was 65% as determined by liquid chromatography), 3.93g of NCP-24 catalyst (Ru 2wt%, Cu 4wt%) prepared in Example 1, and 688.94g of 10% sodium carbonate aqueous solution were added to a stainless steel high-pressure reactor, the reactor was sealed, oxygen was replaced three times, stirring was turned on and the temperature was started, and the oxygen was kept at a constant pressure of 2MPa and 110°C for 4h. After the reaction was completed, it was naturally cooled to room temperature, the pressure in the reactor was vented, and the residual oxygen in the reactor was replaced with nitrogen. The reaction solution was acidified with concentrated hydrochloric acid and washed with water to obtain a white solid of 2,5-furandicarboxylic acid. HPLC detection and analysis showed that the conversion rate of 5-hydroxymethylfurfural was 100%, the yield was 84%, and the purity was 99%. Example 6

[0026] Application of catalyst in oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid 84.07g (0.5mol) of crude 5-hydroxymethylfurfural (the content of 5-hydroxymethylfurfural in the crude product was 75% as determined by liquid chromatography), 3.87g of NCP-32 catalyst (Ru 3wt%, Cu 2wt%) prepared in Example 2, and 688.94g of 10% sodium carbonate aqueous solution were added to a stainless steel high-pressure reactor, the reactor was sealed, oxygen was replaced three times, stirring was turned on and the temperature was started, and the oxygen was kept at a constant pressure of 2MPa and 110°C for 4h. After the reaction was completed, it was naturally cooled to room temperature, the pressure in the reactor was vented, and the residual oxygen in the reactor was replaced with nitrogen. The reaction solution was acidified with concentrated hydrochloric acid and washed with water to obtain a white solid of 2,5-furandicarboxylic acid. HPLC detection and analysis showed that the conversion rate of 5-hydroxymethylfurfural was 100%, the yield was 96%, and the purity was 98%. Example 7

[0027] Application of catalyst in oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid 90.08 g (0.5 mol) of crude 5-hydroxymethylfurfural (the content of 5-hydroxymethylfurfural in the crude product was 70% by liquid chromatography), 3.90 g of the NCP-15 catalyst (Ru 1 wt%, Cu 5 wt%) prepared in Example 3, and 688.94 g of 10% sodium carbonate aqueous solution were added to a stainless steel high-pressure reactor, the reactor was sealed, oxygen was replaced three times, stirring was turned on and the temperature was started to rise, and the oxygen was kept at a constant pressure of 2.5 MPa and 120° C. for 4 h. After the reaction was completed, it was naturally cooled to room temperature, the pressure in the reactor was vented, and the residual oxygen in the reactor was replaced with nitrogen. The reaction liquid was subjected to HPLC detection and analysis, and the conversion rate of 5-hydroxymethylfurfural was 98%, the yield was 94%, and the purity was 97%. Example 8

[0028] Application of catalyst in oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid 84.07g (0.5mol) of crude 5-hydroxymethylfurfural (the content of 5-hydroxymethylfurfural in the crude product was 75% as determined by liquid chromatography), 3.87g of NCP-056 catalyst (Ru 0.5wt%, Cu 6wt%) prepared in Example 4, and 688.94g of 10% sodium carbonate aqueous solution were added to a stainless steel high-pressure reactor, the reactor was sealed, oxygen was replaced three times, stirring was turned on and the temperature was started, and the oxygen was kept at a constant pressure of 2.0MPa and 110°C for 6h. After the reaction was completed, it was naturally cooled to room temperature, the pressure in the reactor was vented, and the residual oxygen in the reactor was replaced with nitrogen. The reaction solution was acidified with concentrated hydrochloric acid and washed with water to obtain a white solid of 2,5-furandicarboxylic acid. HPLC detection and analysis showed that the conversion rate of 5-hydroxymethylfurfural was 95%, the yield was 92%, and the purity was 94%.

[0029] Comparative Example 3 Application of catalyst in oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid 90.08g (0.5mol) of crude 5-hydroxymethylfurfural (the content of 5-hydroxymethylfurfural in the crude product was 70% as determined by liquid chromatography), 3.9g of NCP-20 catalyst (Ru 2wt%) prepared in Comparative Example 1, and 688.94g of 10% sodium carbonate aqueous solution were added to a stainless steel high-pressure reactor, the reactor was sealed, oxygen was replaced three times, stirring was turned on and the temperature was started, and the oxygen was kept at a constant pressure of 2.0MPa and 120°C for 6h. After the reaction was completed, it was naturally cooled to room temperature, the pressure in the reactor was vented, and the residual oxygen in the reactor was replaced with nitrogen. The reaction solution was acidified with concentrated hydrochloric acid and washed with water to obtain a white solid of 2,5-furandicarboxylic acid. HPLC analysis showed that the conversion rate of 5-hydroxymethylfurfural was 81%, the yield was 68%, and the purity was 95%.

[0030] Comparative Example 4 Application of catalyst in oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid 84.07g (0.5mol) of crude 5-hydroxymethylfurfural (the content of 5-hydroxymethylfurfural in the crude product was 75% as determined by liquid chromatography), 3.87g of NCP-05 catalyst (Cu 5wt%) prepared in Comparative Example 2, and 688.94g of 10% sodium carbonate aqueous solution were added to a stainless steel high-pressure reactor, the reactor was sealed, oxygen was replaced three times, stirring was turned on and the temperature was started, and the oxygen was kept at a constant pressure of 2.0MPa and reacted at 120°C for 6h. After the reaction was completed, it was naturally cooled to room temperature, the pressure in the reactor was vented, and the residual oxygen in the reactor was replaced with nitrogen. The reaction solution was acidified with concentrated hydrochloric acid and washed with water to obtain a white solid of 2,5-furandicarboxylic acid. HPLC detection and analysis showed that the conversion rate of 5-hydroxymethylfurfural was 83%, the yield was 53%, and the purity was 91%. Example 9

[0031] Application of recovered catalyst in the oxidation of 5-hydroxymethylfurfural to produce 2,5-furandicarboxylic acid The reaction solution obtained above was centrifuged and the catalyst was recovered. The catalyst was washed with deionized water until the pH was close to 7, and then fully washed with ethanol and dried at 110°C. The obtained solid catalyst can be reused many times. For example, the NCP-32 in Example 6 was recovered. The recovered catalyst was repeatedly washed with water and ethanol for 3 times, and then dried at 110°C to obtain 1.83g of recovered catalyst, with a recovery rate of 96.3%. The experimental results are shown in Table 2 and Figure 3 As shown, the recovered catalyst was used for the sixth verification test. The test conditions were the same as those in Example 6. The reaction solution was acidified with concentrated hydrochloric acid and washed with water to obtain 2,5-furandicarboxylic acid as a white solid. HPLC analysis showed that the conversion rate of 5-hydroxymethylfurfural was 95.02%, the yield was 92.66%, the purity was 98.15%, and the product performance was similar without significant decrease.

[0032] Table 2 Catalyst reuse performance

[0033] The above are only preferred embodiments of the present invention, which will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be pointed out that for those skilled in the art, without departing from the concept of the present invention, several modifications and improvements made are all protected by the present invention.

Claims

1. A method for preparing a supported RuCu diatomic catalyst, characterized in that: The following steps are involved: S1. Preparation of nitrogen-containing porous organic polymer: according to the molar ratio of 2,5-furandicarboxaldehyde, melamine and solvent being (1-3):1:5, 2,5-furandicarboxaldehyde and melamine are added to the solvent and mixed evenly, heated for reaction, and after the reaction is completed, naturally cooled to room temperature and then treated to obtain the nitrogen-containing porous organic polymer; S2. Preparation of nitrogen-doped porous carbon material: a nitrogen-containing porous organic polymer and nano-calcium carbonate are mixed in a mass ratio of 1:1 and then pyrolyzed in an inert gas atmosphere. The calcium carbonate is decomposed by heat to generate calcium oxide and carbon dioxide. The calcium oxide acts as a hard template. The generated carbon dioxide reacts with the nitrogen-containing porous organic polymer through an oxidation-reduction process in the presence of nitrogen and a catalyst in the system at high temperature to generate nitrogen oxides. The calcium carbonate after the reaction is removed and treated to obtain a nitrogen-doped porous carbon material; S3. Loading RuCu diatomic catalyst: adding precious metal Ru salt, non-precious metal Cu salt and alcohol amine to nitrogen-doped porous carbon material, wherein the amount of alcohol amine is 0.01% to 0.04% of the mass of the nitrogen-doped porous carbon material, crushing by ball milling, and then calcining in a mixed gas of hydrogen and nitrogen with a volume ratio of (1-3):1 to obtain RuCu diatomic catalyst.

2. The method for preparing the supported RuCu diatomic catalyst according to claim 1, characterized in that: The heating temperature in S1 is 160°C and the heating time is 3h.

3. The method for preparing the supported RuCu diatomic catalyst according to claim 1, characterized in that: The pyrolysis conditions in S2 were to heat the mixture to 800 °C at a rate of 5 °C / min for 2 h in an inert gas atmosphere.

4. The method for preparing the supported RuCu diatomic catalyst according to claim 1, characterized in that: The total loading amount of Ru and Cu in S3 is 5% to 10%, wherein the loading amount of Ru is 0.5% to 5%, and the loading amount of Cu is 0.5% to 5%.

5. The method for preparing a supported RuCu diatomic catalyst according to claim 1 or 4, characterized in that: The Ru salt is ruthenium chloride trihydrate, and the Cu salt is one or more of copper nitrate trihydrate, copper chloride, copper acetate, and copper sulfate.

6. The method for preparing a supported RuCu diatomic catalyst according to claim 1, characterized in that: The alcohol amine is at least one of triethanolamine, triisopropanolamine and diethanol monoisopropanolamine.

7. The method for preparing a supported RuCu diatomic catalyst according to claim 1, characterized in that: The ball mill speed in S3 is 360r / min, and the crushing time is 3-5min; the calcination conditions are: heating to 200-400°C at a rate of 5°C / min and calcining for 2h.

8. The supported RuCu diatomic catalyst prepared by the method according to any one of claims 1 to 7, characterized in that: The carrier of the catalyst is nitrogen-doped porous carbon, and Ru and Cu are uniformly distributed on the surface of the carrier in a single-atom manner.

9. Use of the supported RuCu diatomic catalyst according to claim 8 in the catalytic oxidation of crude 5-hydroxymethylfurfural to prepare 2,5-furandicarboxylic acid, characterized in that: The specific application includes the following steps: The crude 5-hydroxymethylfurfural, a loaded RuCu diatomic catalyst, an alkali solution and an oxygen source are contacted, the molar ratio of the 5-hydroxymethylfurfural to the alkali is 1:3.5, the reaction temperature is 100° C. to 150° C., the reaction pressure is 0.3 to 3.0 MPa, and the reaction time is 0.5 to 8 h, to catalytically oxidize and synthesize 2,5-furandicarboxylic acid.

10. Use of the supported RuCu diatomic catalyst according to claim 9 in the catalytic oxidation of crude 5-hydroxymethylfurfural to prepare 2,5-furandicarboxylic acid, characterized in that: The mass proportion of crude 5-hydroxymethylfurfural in the reaction system is 5% to 20%.

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