A method for preparing and using a ruthenium-loaded copper-cobalt metal oxide composite magnesium oxide catalyst

Abstract

The application relates to a method for synthesizing 2,5-furan dicarboxylic acid from 5-hydroxymethylfurfural by using a ruthenium-loaded copper-cobalt metal oxide composite magnesium oxide catalyst. The method comprises the following steps: mixing and grinding a copper-cobalt hydroxide precursor prepared by a hydrothermal-calcination method with anhydrous magnesium acetate and then calcining to obtain a catalyst carrier; and using an impregnation-reduction method to load ruthenium nanoparticles on the carrier as an active component. The synergistic effect of the active component and the carrier enables 5-hydroxymethylfurfural to be catalytically converted into 2,5-furan dicarboxylic acid in a high-efficiency and selective manner. The catalyst preparation process is simple and easy to scale up. In the absence of alkali, the conversion rate of 5-hydroxymethylfurfural can reach 100%, and the yield of 2,5-furan dicarboxylic acid is 86.1%. The semi-preparative liquid chromatography is used for green separation and purification of the product, and 2,5-furan dicarboxylic acid with a purity of more than 99% is obtained. The method has potential application value for large-scale production of 2,5-furan dicarboxylic acid.

Description

Preparation method and application of a ruthenium-supported copper-cobalt metal oxide composite magnesium oxide catalyst Technical Field

[0001] This invention belongs to the field of catalyst preparation and application technology, and particularly relates to a method for preparing and applying a ruthenium-supported copper-cobalt metal oxide composite magnesium oxide catalyst. Background Technology

[0002] With the increasing scarcity of fossil resources, the conversion of biomass into effective chemicals has become a current research focus. For example, 5-hydroxymethylfurfural (5-HMF), a biomass platform compound, is a hexose dehydration product and has attracted widespread attention due to its ability to synthesize various key compound precursors. Among these, 2,5-furandicarboxylic acid (2,5-Furfural), formed by the oxidation of 5-HMF, has been identified by the United States as one of the twelve most promising glycosyl chemicals. 2,5-Furfuraldicarboxylic acid can be used as a monomer for synthesizing bio-based polymers such as polyamides, polyesters, and polyurethanes. 2,5-Furfuraldicarboxylic acid has a structure very similar to the petroleum-based monomer 1,4-phthalic acid (PTA). Polyethylene furanate (PEF), synthesized using 2,5-Furfuraldicarboxylic acid as a polymer monomer, is more environmentally friendly than petroleum-based polyester (PET), and is biodegradable, non-toxic, and harmless. Therefore, 2,5-Furfuraldicarboxylic acid plays a crucial role in green chemistry.

[0003] For the synthesis of 2,5-furandicarboxylic acid from 5-hydroxymethylfurfural, economical and environmentally friendly supported noble metal catalysts have become a focus of attention. Generally, metal oxides or activated carbon are chosen as supports to support active components such as Pt, Au, Pd, and Ru. Among these, Ru is relatively inexpensive compared to other noble metals and has broad prospects for industrial applications.

[0004] Numerous studies have reported on the oxidation of 5-hydroxymethylfurfural in systems with added liquid alkali, which, while yielding high production rates of 2,5-furandicarboxylic acid, is detrimental to the separation and industrial production of this product. Catalysis of this reaction in a alkali-free system is a future research direction. The following reactions were all carried out under alkali-free conditions. Gao et al. prepared a novel catalyst, Ru₄CoO₂. y (OH)₂, using water as a solvent, reacted at 140°C for 18 hours under 1 MPa oxygen pressure, resulting in the complete conversion of 5-hydroxymethylfurfural and a 99.9% yield of 2,5-furandicarboxylic acid. 0 The species possesses the ability to adsorb and activate the OH groups of 5-hydroxymethylfurfural, thereby oxidizing 5-hydroxymethylfurfural. This is achieved through Co... 2+ / Co 3+ The synergistic effect of redox reactions can effectively convert O2 into active O2. latt This may be the key to the catalyst's high catalytic activity. Gorbanev et al. prepared Ru(OH)₂.x A Ru / MgO catalyst, using water as a solvent, reacted at 140°C for 6 hours under 2.5 bar oxygen pressure, achieving 100% conversion of 5-hydroxymethylfurfural and a 2,5-furandicarboxylic acid yield greater than 90%. Antonyraj et al. prepared a Ru / MgO catalyst, using water as a solvent, reacting at 160°C for 4 hours under 90 psi oxygen pressure, ultimately achieving 100% conversion of 5-hydroxymethylfurfural and a 2,5-furandicarboxylic acid yield greater than 90%. Antonyraj et al. prepared a Ru / MgAlO catalyst, using water as a solvent, reacting at 140°C for 4 hours under 90 psi oxygen pressure, achieving 100% conversion of 5-hydroxymethylfurfural and a 2,5-furandicarboxylic acid yield of 99%, but this catalyst dissolved during the reaction. Yi et al. developed a Ru / C catalyst that can oxidize 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid under alkali-free conditions. 5-hydroxymethylfurfural is completely converted, and the yield of 2,5-furandicarboxylic acid is as high as 88%. However, the catalyst needs to be activated before it can be reused.

[0005] Reported methods for the oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid using Ru supported on metal oxides or activated carbon suffer from drawbacks, including the need for improved catalyst stability, easy catalyst deactivation, the need for adding liquid alkali to the reaction system, and difficulty in separating the 2,5-furandicarboxylic acid product. Therefore, developing highly stable catalysts for the efficient synthesis of 2,5-furandicarboxylic acid from 5-hydroxymethylfurfural in an alkali-free system, along with the separation of 2,5-furandicarboxylic acid, is of great significance. To date, no reports have been published on the use of ruthenium-supported copper-cobalt metal oxide composite magnesium oxide catalysts for the synthesis of 2,5-furandicarboxylic acid from 5-hydroxymethylfurfural. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a ruthenium-supported copper-cobalt metal oxide composite magnesium oxide catalyst and its application in the catalytic synthesis of 2,5-furandicarboxylic acid from 5-hydroxymethylfurfural, in order to solve the technical problems of the current metal oxide or activated carbon supported Ru catalysts, such as the need to improve the stability of the catalysts, easy deactivation of the catalysts, the need to add liquid alkali in the reaction system, and the difficulty in separating the 2,5-furandicarboxylic acid product.

[0007] To achieve the above objectives, the specific technical solution for the preparation method and application of a ruthenium-supported copper-cobalt metal oxide composite magnesium oxide catalyst of the present invention is as follows:

[0008] The preparation method of ruthenium-supported copper-cobalt metal oxide composite magnesium oxide catalyst involves preparing copper-cobalt metal oxide composite magnesium oxide as a catalyst support via a hydrothermal-calcination method, and loading a small amount of ruthenium nanoparticles onto the support as the active component via an impregnation-reduction method. The following steps are performed sequentially:

[0009] Step A1: Prepare a mixture of copper-cobalt hydroxide precursors;

[0010] Step A2: The copper-cobalt hydroxide mixture obtained in step A1 is subjected to hydrothermal calcination to obtain copper-cobalt precursor powder, which is then mixed and ground with anhydrous magnesium acetate and calcined to prepare a catalyst support.

[0011] Step A3: Load a small amount of ruthenium nanoparticles as an active component onto the support obtained in step A2 using the impregnation-reduction method.

[0012] The specific preparation steps are as follows:

[0013] Preparation of precursor mixture: Under vigorous stirring, a certain concentration of sodium hydroxide aqueous solution was added dropwise to a mixed solution of Cu(NO3)2·3H2O and Co(NO3)2·6H2O until the pH ≈ 10, thus obtaining a copper-cobalt hydroxide mixed solution precursor.

[0014] Preparation of the support: A copper-cobalt hydroxide mixture precursor was subjected to a hydrothermal reaction. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed until neutral, and dried to obtain the precursor powder. The precursor powder was thoroughly mixed and ground with anhydrous magnesium acetate, then calcined in air and cooled to room temperature to obtain a copper-cobalt metal oxide composite magnesium oxide support.

[0015] Loading of the active component: A copper-cobalt metal oxide composite magnesium oxide support was impregnated and dispersed in an aqueous solution of RuCl3·3H2O. The mixture was placed in an ice-water bath with stirring. An aqueous solution of NaBH4 containing NaOH was added dropwise to the dispersion, and stirring continued for reduction. The mixture was filtered and washed until neutral, and then vacuum dried to obtain the ruthenium-supported copper-cobalt metal oxide composite magnesium oxide catalyst.

[0016] Preferably, in order to compare the catalytic effect with catalysts prepared by the same method using different proportions of copper-cobalt metal oxide composite magnesium oxide supported ruthenium, the molar ratios of Cu(NO3)2·3H2O and Co(NO3)2·6H2O were selected as 1:0, 1:1, 1:2, 2:1, and 0:1 during the preparation of the precursor mixture. After the hydrothermal reaction was completed, a certain proportion of anhydrous magnesium acetate was mixed and ground with the hydroxide precursor to prepare the catalyst support, which was named Cu x O y ·MgO, Cu1-Co1-O·MgO, Cu1-Co2-O·MgO, Cu2-Co1-O·MgO and Co x O y ·MgO, the corresponding catalyst is named Ru z / Cu x O y ·MgO, Ru z / Cu1-Co1-O·MgO、Ru z / Cu1-Co2-O·MgO、Ru z / Cu2-Co1-O·MgO and Ru z / Co x O y ·MgO (based on the mass ratio of Ru loading to carrier, z = 1, 2, 3, 4, 5).

[0017] Preferably, in the preparation of the precursor mixture, a total of 6 mmol of Cu(NO3)2·3H2O and Co(NO3)2·6H2O are dissolved in 60 mL of deionized water in a certain proportion, and the concentration of the NaOH aqueous solution is 1-2 mol / L.

[0018] Preferably, during the preparation of the carrier, 0.2g of copper cobalt hydroxide precursor powder is mixed with 2-8mmol of anhydrous magnesium acetate, the hydrothermal temperature is 150-200℃, the hydrothermal time is 3-6h, the calcination temperature is 300-500℃, and the calcination time is 3-6h.

[0019] Preferably, during the loading of the active component, 0.5 g of the carrier is weighed and dispersed in 12.5 mL of deionized water, with ruthenium loading accounting for 1–5 wt% of the carrier, and the impregnation and dispersion time is 10–24 h. RuCl3·3H2O contains Ru 3+ The molar ratio of NaBH4ˉ to BH4ˉ in NaBH4 is 1:15 to 1:25. The concentration of NaBH4 is 1 to 2 mol / L, the concentration of NaOH aqueous solution is 0.3 to 0.7 wt%, and the reduction time is 10 to 24 h.

[0020] This invention also provides the application of a ruthenium-supported copper-cobalt metal oxide composite magnesium oxide catalyst in the selective oxidation of 5-hydroxymethylfurfural to synthesize 2,5-furandicarboxylic acid.

[0021] 5-Hydroxymethylfurfural was dissolved in deionized water, and oxygen was used as the oxygen source. A ruthenium-supported copper-cobalt metal oxide composite magnesium oxide catalyst was used to catalyze the selective oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid. The following steps were performed sequentially:

[0022] Oxidation of 5-hydroxymethylfurfural: 5-hydroxymethylfurfural, deionized water, and a ruthenium-supported copper-cobalt metal oxide composite magnesium oxide catalyst were added to a reaction vessel. Oxygen was then introduced, and the reaction was carried out under heating and stirring. After the reaction, the mixture was cooled to room temperature, the vent valve was opened to release the gas, and the catalyst was filtered out. The obtained reaction solution was diluted with purified water, and the diluted reaction solution was analyzed by high-performance liquid chromatography (HPLC) to calculate the conversion rate of the raw material 5-hydroxymethylfurfural and the yield of the target product 2,5-furandicarboxylic acid.

[0023] Separation and purification of 2,5-furandicarboxylic acid: The filtrate obtained after the reaction was collected, and 2,5-furandicarboxylic acid was separated using semi-preparative liquid chromatography with a UV detector. A C18 column was used, and the mobile phase was 0.1 wt% formic acid aqueous solution and methanol at a volume ratio of 7:3, with a flow rate of 3.5 mL / min. A solution containing 2,5-furandicarboxylic acid was obtained, with methanol as the solvent. Methanol and formic acid were removed by rotary evaporation, and the obtained 2,5-furandicarboxylic acid was dried. The purity of the product 2,5-furandicarboxylic acid was analyzed using high-performance liquid chromatography.

[0024] The preparation method and application of the ruthenium-supported copper-cobalt metal oxide composite magnesium oxide catalyst of the present invention have the following advantages:

[0025] (1) This invention utilizes a hydrothermal method to prepare copper-cobalt metal oxide precursors. These precursors are then mixed with magnesium oxide, ground, and calcined to prepare a copper-cobalt metal oxide composite magnesium oxide catalyst support. A small amount of ruthenium nanoparticles are loaded onto the support as the active component using an impregnation-reduction method, thus preparing a ruthenium-supported copper-cobalt metal oxide composite magnesium oxide catalyst. This catalyst was applied to the oxidation of 5-hydroxymethylfurfural under conditions without added alkali. The reactor was charged with 1.0 MPa O2, and the reaction was carried out at 120°C for 12 h. The conversion rate of 5-hydroxymethylfurfural was 100%, and the yield of 2,5-furandicarboxylic acid reached 86.1%. 2,5-furandicarboxylic acid was separated using semi-preparative liquid chromatography, avoiding the need for adding concentrated hydrochloric acid for crystallization separation, resulting in a 2,5-furandicarboxylic acid purity greater than 99%.

[0026] (2) In the catalyst of this invention, the Cu-Co-O composite magnesium oxide has strong alkaline sites, which can avoid the addition of liquid alkali to the system. The Ru metal in the catalyst is low in cost compared with other noble metals. By loading a small amount of Ru, the catalytic activity can be significantly improved, giving it enough active sites for oxidation reactions. Therefore, the catalyst has strong catalytic ability. Moreover, the catalyst preparation process is simple and has good application prospects. Attached Figure Description

[0027] Figure 1 shows a series of supports prepared in Examples 1-5 of this invention: Cu1-Co1-O, Cu1-Co2-O, Cu2-Co1-O, Cu1-Co1-O·MgO, Cu1-Co2-O·MgO, Cu2-Co1-O·MgO, Cu x O y ·MgO, Co x O y ·MgO, Cu x O y Co x O y X-ray diffraction patterns of MgO and MgO.

[0028] Figure 2 is the EDS energy spectrum of the Ru4 / Cu1-Co1-O·MgO catalyst prepared in Example 1 of the present invention.

[0029] Figure 3 is a SEM image of the Ru4 / Cu1-Co1-O·MgO catalyst prepared in Example 1 of this invention. Detailed Implementation

[0030] To better understand the purpose, structure, and application of this invention, the following detailed description, in conjunction with the accompanying drawings, provides a method for preparing and applying a ruthenium-supported copper-cobalt metal oxide composite magnesium oxide catalyst.

[0031] Example 1:

[0032] Example 1 of this invention discloses a method for preparing a ruthenium-supported copper-cobalt metal oxide composite magnesium oxide catalyst, the specific steps of which are as follows:

[0033] Preparation of the precursor mixture: A total of 6 mmol of Cu(NO3)2·3H2O and Co(NO3)2·6H2O were dissolved in 60 mL of deionized water at a molar ratio of 1:1. Under vigorous stirring, a 1.5 mol / L sodium hydroxide aqueous solution was added dropwise to the above solution until the pH ≈ 10, at which point the addition was stopped, yielding the copper-cobalt hydroxide mixture precursor.

[0034] Preparation of the support: A copper-cobalt hydroxide mixture precursor was placed in a hydrothermal reactor and hydrothermally heated at 180°C for 4 hours. After the hydrothermal reaction was completed, the mixture was cooled to room temperature, filtered to obtain a solid powder, and washed until the filtrate was neutral. The powder was then dried at 60°C for 12 hours to obtain copper-cobalt hydroxide powder. 0.2 g of copper-cobalt hydroxide powder was weighed and thoroughly ground with 6 mmol of anhydrous magnesium acetate to obtain catalyst precursor powder. The precursor powder was calcined at 400°C for 4 hours in air and then cooled to room temperature to obtain a copper-cobalt metal oxide composite magnesium oxide support, named Cu1-Co1-O·MgO.

[0035] Loading of the active component: Weigh a certain amount of RuCl3·3H2O according to the ruthenium loading of 4wt% of the support, add it to 12.5mL of deionized water, and dissolve it completely. Disperse 0.5g of catalyst support in it and impregnate and disperse for 12h under stirring. The reaction is based on the relationship between BH4ˉ in NaBH4 and Ru in RuCl3·3H2O. 3+NaBH4 was weighed and dissolved in a 0.5 wt% NaOH aqueous solution at a molar ratio of 20:1 to achieve a NaBH4 concentration of 1.5 mol / L. Then, the NaBH4 aqueous solution containing NaOH was added dropwise to the dispersion under ice-water bath stirring conditions, and stirring and reduction were continued for 12 h. The solid powder was obtained by filtration and washed until the filtrate was neutral. It was then vacuum dried at 60 °C for 12 h to obtain a ruthenium-supported copper-cobalt metal oxide composite magnesium oxide catalyst, named Ru4 / Cu1-Co1-O·MgO.

[0036] The X-ray diffraction patterns of the catalyst supports Cu1-Co1-O, Cu1-Co1-O·MgO, and MgO in this embodiment are shown in Figure 1. As can be seen from Figure 1, the characteristic peak of MgO was detected in Cu1-Co1-O·MgO, indicating the successful composite of magnesium oxide.

[0037] The EDS spectrum of the catalyst Ru4 / Cu1-Co1-O·MgO in this embodiment is shown in Figure 2. As can be seen from Figure 2, Ru was successfully loaded onto the support.

[0038] The SEM image of the catalyst Ru4 / Cu1-Co1-O·MgO in this embodiment is shown in Figure 3.

[0039] Example 2:

[0040] Example 2 of this invention discloses a method for preparing a ruthenium-supported copper-cobalt metal oxide composite magnesium oxide catalyst, the specific steps of which are as follows:

[0041] Preparation of the precursor mixture: A total of 6 mmol of Cu(NO3)2·3H2O and Co(NO3)2·6H2O were dissolved in 60 mL of deionized water at a molar ratio of 1:2. Under vigorous stirring, a 1.5 mol / L sodium hydroxide aqueous solution was added dropwise to the above solution until the pH ≈ 10, at which point the addition was stopped, yielding the copper-cobalt hydroxide mixture precursor.

[0042] Preparation of the support: A copper-cobalt hydroxide mixture precursor was placed in a hydrothermal reactor and hydrothermally heated at 180°C for 4 hours. After the hydrothermal reaction was completed, the mixture was cooled to room temperature, filtered to obtain a solid powder, and washed until the filtrate was neutral. The powder was then dried at 60°C for 12 hours to obtain copper-cobalt hydroxide powder. 0.2 g of copper-cobalt hydroxide powder was weighed and thoroughly ground with 6 mmol of anhydrous magnesium acetate to obtain catalyst precursor powder. The precursor powder was calcined at 400°C for 4 hours in air and then cooled to room temperature to obtain a copper-cobalt metal oxide composite magnesium oxide support, named Cu1-Co2-O·MgO.

[0043] Loading of the active component: Weigh a certain amount of RuCl3·3H2O according to the ruthenium loading of 4wt% of the support, add it to 12.5mL of deionized water, and dissolve it completely. Disperse 0.5g of catalyst support in it and impregnate and disperse for 12h under stirring. The reaction is based on the relationship between BH4ˉ in NaBH4 and Ru in RuCl3·3H2O. 3+ NaBH4 was weighed and dissolved in a 0.5 wt% NaOH aqueous solution at a molar ratio of 20:1 to achieve a NaBH4 concentration of 1.5 mol / L. Then, the NaBH4 aqueous solution containing NaOH was added dropwise to the dispersion under ice-water bath stirring conditions, and stirring and reduction were continued for 12 h. The solid powder was obtained by filtration and washed until the filtrate was neutral. It was then vacuum dried at 60 °C for 12 h to obtain a ruthenium-supported copper-cobalt metal oxide composite magnesium oxide catalyst, named Ru4 / Cu1-Co2-O·MgO.

[0044] The X-ray diffraction patterns of the catalyst supports Cu1-Co2-O, Cu1-Co2-O·MgO, and MgO in this embodiment are shown in Figure 1. As can be seen from Figure 1, the characteristic peak of MgO was detected in Cu1-Co2-O·MgO, indicating the successful composite of magnesium oxide.

[0045] Example 3:

[0046] Example 3 of this invention discloses a method for preparing a ruthenium-supported copper-cobalt metal oxide composite magnesium oxide catalyst, the specific steps of which are as follows:

[0047] Preparation of the precursor mixture: A total of 6 mmol of Cu(NO3)2·3H2O and Co(NO3)2·6H2O were dissolved in 60 mL of deionized water at a molar ratio of 2:1. Under vigorous stirring, a 1.5 mol / L sodium hydroxide aqueous solution was added dropwise to the above solution until the pH ≈ 10, at which point the addition was stopped, yielding the copper-cobalt hydroxide mixture precursor.

[0048] Preparation of the support: A copper-cobalt hydroxide mixture precursor was placed in a hydrothermal reactor and hydrothermally heated at 180°C for 4 hours. After the hydrothermal reaction was completed, the mixture was cooled to room temperature, filtered to obtain a solid powder, and washed until the filtrate was neutral. The powder was then dried at 60°C for 12 hours to obtain copper-cobalt hydroxide powder. 0.2 g of copper-cobalt hydroxide powder was weighed and thoroughly ground with 6 mmol of anhydrous magnesium acetate to obtain catalyst precursor powder. The precursor powder was calcined at 400°C for 4 hours in air and then cooled to room temperature to obtain a copper-cobalt metal oxide composite magnesium oxide support, named Cu2-Co1-O·MgO.

[0049] Loading of the active component: Weigh a certain amount of RuCl3·3H2O according to the ruthenium loading of 4wt% of the support, add it to 12.5mL of deionized water, and dissolve it completely. Disperse 0.5g of catalyst support in it and impregnate and disperse for 12h under stirring. The reaction is based on the relationship between BH4ˉ in NaBH4 and Ru in RuCl3·3H2O. 3+ NaBH4 was weighed and dissolved in a 0.5 wt% NaOH aqueous solution at a molar ratio of 20:1 to achieve a NaBH4 concentration of 1.5 mol / L. Then, the NaBH4 aqueous solution containing NaOH was added dropwise to the dispersion under ice-water bath stirring conditions, and stirring and reduction were continued for 12 h. The solid powder was obtained by filtration and washed until the filtrate was neutral. It was then vacuum dried at 60 °C for 12 h to obtain a ruthenium-supported copper-cobalt metal oxide composite magnesium oxide catalyst, named Ru4 / Cu2-Co1-O·MgO.

[0050] The X-ray diffraction patterns of the catalyst supports Cu2-Co1-O, Cu2-Co1-O·MgO, and MgO in this embodiment are shown in Figure 1. As can be seen from Figure 1, the characteristic peaks of MgO were detected in Cu2-Co1-O·MgO, indicating the successful composite formation of magnesium oxide.

[0051] Example 4:

[0052] Example 4 of this invention discloses a method for preparing a ruthenium-supported copper oxide composite magnesium oxide catalyst, the specific steps of which are as follows:

[0053] Preparation of the precursor mixture: Dissolve 6 mmol of Cu(NO3)2·3H2O in 60 mL of deionized water. Under vigorous stirring, add 1.5 mol / L sodium hydroxide aqueous solution dropwise to the above solution until pH≈10, then stop adding to obtain the copper hydroxide mixture precursor.

[0054] Preparation of the support: The copper hydroxide mixed solution precursor was placed in a hydrothermal reactor and hydrothermally heated at 180℃ for 4 hours. After the hydrothermal reaction was completed, the mixture was cooled to room temperature, filtered to obtain a solid powder, and washed until the filtrate was neutral. The powder was then dried at 60℃ for 12 hours to obtain copper hydroxide powder. 0.2 g of copper hydroxide powder was weighed and thoroughly ground with 6 mmol of anhydrous magnesium acetate to obtain the catalyst precursor powder. The precursor powder was calcined at 400℃ for 4 hours in air and then cooled to room temperature to obtain a copper oxide composite magnesium oxide support, named Cu. x O y ·MgO.

[0055] Loading of the active component: Weigh a certain amount of RuCl3·3H2O according to the ruthenium loading of 4wt% of the support, add it to 12.5mL of deionized water, and dissolve it completely. Disperse 0.5g of catalyst support in it and impregnate and disperse for 12h under stirring. The reaction is based on the relationship between BH4ˉ in NaBH4 and Ru in RuCl3·3H2O. 3+ NaBH4 was weighed and dissolved in a 0.5 wt% NaOH aqueous solution at a molar ratio of 20:1 to achieve a NaBH4 concentration of 1.5 mol / L. Then, the NaBH4 aqueous solution containing NaOH was added dropwise to the dispersion under ice-water bath stirring conditions, and stirring and reduction were continued for 12 h. The solid powder was obtained by filtration and washed until the filtrate was neutral. It was then vacuum dried at 60 °C for 12 h to obtain a ruthenium-supported copper oxide composite magnesium oxide catalyst, named Ru4 / Cu. x O y ·MgO.

[0056] In this embodiment, the catalyst support Cu x O y Cu x O y The X-ray diffraction patterns of MgO and MgO are shown in Figure 1. From Figure 1, it can be seen that Cu... x O y The detection of characteristic peaks of MgO in MgO indicates successful recombination of magnesium oxide. Cu x O y The X-ray diffraction peaks of the sample are consistent with those of CuO (JCPDS 45-0937).

[0057] Example 5:

[0058] Example 5 of this invention discloses a method for preparing a ruthenium-supported cobalt tetroxide composite magnesium oxide catalyst, the specific steps of which are as follows:

[0059] Preparation of the precursor mixture: Dissolve 6 mmol of Co(NO3)2·6H2O in 60 mL of deionized water. Under vigorous stirring, add 1.5 mol / L sodium hydroxide aqueous solution dropwise to the above solution until pH≈10, then stop adding to obtain the cobalt hydroxide mixture precursor.

[0060] Preparation of the support: The cobalt hydroxide mixed solution precursor was placed in a hydrothermal reactor and hydrothermally heated at 180℃ for 4 hours. After the hydrothermal reaction was completed, the mixture was cooled to room temperature, filtered to obtain a solid powder, and washed until the filtrate was neutral. The resulting cobalt hydroxide powder was dried at 60℃ for 12 hours. 0.2 g of the cobalt hydroxide powder was weighed and thoroughly ground with 6 mmol of anhydrous magnesium acetate to obtain the catalyst precursor powder. The precursor powder was calcined at 400℃ for 4 hours in air and then cooled to room temperature to obtain a cobalt tetroxide composite magnesium oxide support, named Co. x Oy ·MgO.

[0061] Loading of the active component: Weigh a certain amount of RuCl3·3H2O according to the ruthenium loading of 4wt% of the support, add it to 12.5mL of deionized water, and dissolve it completely. Disperse 0.5g of catalyst support in it and impregnate and disperse for 12h under stirring. The reaction is based on the relationship between BH4ˉ in NaBH4 and Ru in RuCl3·3H2O. 3+ NaBH4 was weighed and dissolved in a 0.5 wt% NaOH aqueous solution at a molar ratio of 20:1 to achieve a NaBH4 concentration of 1.5 mol / L. Then, the NaBH4 aqueous solution containing NaOH was added dropwise to the dispersion under ice-water bath stirring conditions, and stirring was continued for 12 h for reduction. The solid powder was obtained by filtration and washed until the filtrate was neutral. It was then vacuum dried at 60 °C for 12 h to obtain a ruthenium-supported cobalt tetroxide composite magnesium oxide catalyst, named Ru4 / Co. x O y ·MgO.

[0062] In this embodiment, the catalyst support Co x O y Co x O y The X-ray diffraction patterns of MgO and MgO are shown in Figure 1. From Figure 1, it can be seen that Co... x O y The detection of characteristic peaks of MgO in MgO indicates successful recombination of magnesium oxide. Co x O y The X-ray diffraction peaks of the sample are consistent with those of Co3O4 (JCPDS 42-1467).

[0063] Example 6:

[0064] The catalysts were used in the reaction to synthesize 2,5-furandicarboxylic acid by the oxidation of 5-hydroxymethylfurfural, and the specific steps are as follows:

[0065] Oxidation of 5-hydroxymethylfurfural: 0.2 mmol of 5-hydroxymethylfurfural, 5 mL of deionized water, and 0.08 g of catalyst were added to a reaction vessel, followed by the introduction of 1.0 MPa of oxygen. The reaction was carried out at 110 °C with stirring for 12 h. After the reaction, the mixture was cooled to room temperature, the vent valve was opened to release the gas, and the catalyst was filtered out. The obtained reaction solution was diluted with purified water, and the diluted reaction solution was analyzed by high-performance liquid chromatography (HPLC) to calculate the conversion rate of the raw material 5-hydroxymethylfurfural and the yield of the target product 2,5-furandicarboxylic acid.

[0066] Separation and purification of 2,5-furandicarboxylic acid: The filtrate obtained after the reaction was collected, and 2,5-furandicarboxylic acid was separated using semi-preparative liquid chromatography with a UV detector. A C18 column was used, and the mobile phase was 0.1 wt% formic acid aqueous solution and methanol at a volume ratio of 7:3, with a flow rate of 3.5 mL / min. A solution containing 2,5-furandicarboxylic acid was obtained, with methanol as the solvent. Methanol and formic acid were removed by rotary evaporation, and the obtained 2,5-furandicarboxylic acid was dried. The purity of the product 2,5-furandicarboxylic acid was analyzed using high-performance liquid chromatography.

[0067] Liquid chromatography testing conditions: UV detector, C18 column (250 mm × 4.6 mm, 5 μm), 0.1 wt% formic acid aqueous solution: methanol = 7:3 as mobile phase, column temperature 30 ℃, injection volume 5 μL, record peak position and peak area, and perform quantitative analysis using external standard method.

[0068] Examples 7, 8, 9, 10, and 11:

[0069] Under the same reaction conditions as in Example 6, different copper-cobalt molar ratios were varied to carry out catalytic reactions under the condition of 6 mmol of magnesium oxide. The reaction results are shown in Table 1.

[0070] Table 1 Catalytic results for different copper-cobalt molar ratios

[0071]

[0072] Note: 5-Hydroxymethylfurfural (HMF), 2,5-furandicarboxylic acid (FDCA), 5-hydroxymethyl-2-furancarboxylic acid (HFCA), 5-formyl-2-furancarboxylic acid (FFCA). The molar ratio of copper to cobalt in Ru4 / Cu1-Co1-O·MgO is 1:1, the molar ratio of copper to cobalt in Ru4 / Cu1-Co2-O·MgO is 1:2, the molar ratio of copper to cobalt in Ru4 / Cu2-Co1-O·MgO is 2:1, and the molar ratio of copper to cobalt in Ru4 / Cu... x O y The molar ratio of MgO to copper and cobalt is 1:0, and the ratio of Ru4 / Co is... x O y The molar ratio of copper to cobalt in MgO is 0:1.

[0073] Table 1 shows the catalytic results for different copper-cobalt molar ratios. It can be seen that Cu1-Co1-O·MgO with a copper-cobalt molar ratio of 1:1 has the best catalytic effect as a support, with HMF conversion of 100% and FDCA yield of 78.6%.

[0074] Examples 7, 12, 13, 14, and 15:

[0075] Under the same reaction conditions as in Example 6, with a copper-cobalt molar ratio of 1:1, the effect of varying amounts of magnesium oxide on the catalytic reaction was investigated, with the amount of magnesium oxide varying from 0 to 8 mmol. The reaction results are shown in Table 2.

[0076] Table 2 Catalytic results of magnesium oxide with different amounts of the same compound.

[0077]

[0078] Note: The composite amount of magnesium oxide Ru4 / Cu1-Co1-O·MgO (0 mmol) is 0 mmol, the composite amount of magnesium oxide Ru4 / Cu1-Co1-O·MgO (2 mmol) is 2 mmol, the composite amount of magnesium oxide Ru4 / Cu1-Co1-O·MgO (4 mmol) is 4 mmol, the composite amount of magnesium oxide Ru4 / Cu1-Co1-O·MgO (6 mmol) is 6 mmol, and the composite amount of magnesium oxide Ru4 / Cu1-Co1-O·MgO (8 mmol) is 8 mmol.

[0079] Table 2 shows the catalytic results of magnesium oxide (MgO) with different amounts of MgO. As can be seen from the table, the yield of FDCA increases with the gradual increase of MgO concentration from 0 mmol. The catalytic effect is best when the MgO concentration reaches 6 mmol, with a 100% conversion of the HMF feedstock and a 78.6% yield of the target product, FDCA. With further increases in MgO concentration, the FDCA yield decreases to 38.9%. Therefore, the optimal MgO concentration is 6 mmol.

[0080] Examples 7, 16, 17, 18, 19, and 20:

[0081] Under the same reaction conditions as in Example 6, ruthenium with different loadings was loaded onto a Cu1-Co1-O·MgO support under the condition of 6 mmol of magnesium oxide. The reaction results are shown in Table 3.

[0082] Table 3 Effect of Ruthenium loading on catalytic performance

[0083]

[0084] Note: The loading of Cu1-Co1-O·MgO ruthenium is 0 wt%, the loading of Ru1 / Cu1-Co1-O·MgO ruthenium is 1 wt%, the loading of Ru2 / Cu1-Co1-O·MgO ruthenium is 2 wt%, the loading of Ru3 / Cu1-Co1-O·MgO ruthenium is 3 wt%, the loading of Ru4 / Cu1-Co1-O·MgO ruthenium is 4 wt%, and the loading of Ru5 / Cu1-Co1-O·MgO ruthenium is 5 wt%.

[0085] Table 3 shows that the catalytic activity increases with increasing ruthenium loading. At a loading of 2 wt%, HMF is completely converted, with an FDCA yield of 35.4%. When the loading increases to 3 wt%, the FDCA yield increases to 71.0%, and the optimal catalytic effect is achieved at 4 wt%, with an FDCA yield of 78.6%. Further increasing the Ru loading to 5 wt% decreases the FDCA yield to 63.7%. Therefore, the optimal Ru loading is set at 4 wt%.

[0086] Examples 7, 21, 22, and 23:

[0087] The reaction was carried out under the same conditions as in Example 6, using Ru4 / Cu1-Co1-O·MgO catalyst with 6 mmol of magnesium oxide. The reaction results are shown in Table 4 when the calcination temperature of the support is different.

[0088] Table 4 Effect of calcination temperature of support on catalytic performance

[0089]

[0090] Table 4 shows the effect of support calcination temperature on catalytic performance. At a support calcination temperature of 400℃, HMF is completely converted, and the FDCA yield is the highest at 78.6%. As the support calcination temperature continues to increase, the FDCA yield decreases. At a support calcination temperature of 450℃, the catalyst activity decreases, and the FDCA yield drops to 71.1%. When the support calcination temperature reaches 500℃, the FDCA yield further decreases to 64.2%. Therefore, the optimal support calcination temperature is set at 400℃.

[0091] Examples 7, 24, 25, 26, and 27:

[0092] The reaction was carried out under the same conditions as in Example 6, using Ru4 / Cu1-Co1-O·MgO catalyst at different reaction temperatures with 6 mmol of magnesium oxide. The results are shown in Table 5.

[0093] Table 5 Effect of reaction temperature on catalytic performance

[0094]

[0095] Table 5 shows that HMF can be basically converted at a reaction temperature of 90℃, with a conversion rate of 98.4%. HMF can be completely converted between 100 and 130℃. With increasing temperature, the yield of FDCA shows a trend of first increasing and then decreasing, reaching its highest at 120℃ (86.1%). However, when the reaction temperature is further increased to 130℃, the yield of FDCA decreases to 70.4%, while the yields of HFCA and FFCA increase to 5.8% and 10.1%, respectively. Therefore, the optimal reaction temperature is set at 120℃.

[0096] Examples 26, 28, 29, 30, and 31:

[0097] The reaction was carried out under the same conditions as in Example 26, using Ru4 / Cu1-Co1-O·MgO catalyst with 6 mmol of magnesium oxide, at different reaction times. The results are shown in Table 6.

[0098] Table 6 Effect of reaction time on catalytic performance

[0099]

[0100] Table 6 shows that when the reaction time is 8 h, HMF is completely converted, the yield of FDCA is 62.1%, and the yields of byproducts HFCA and FFCA are 5.8% and 11.4%, respectively. Extending the reaction time to 12 h, the yield of FDCA reaches 86.1%. Further increasing the reaction time leads to a decrease in the yield of FDCA; at 14 h, the yield is 79.2%, and at 16 h, it is 65.6%. Therefore, the optimal reaction time is set at 12 h.

[0101] Examples 26, 32, and 33:

[0102] The reaction was carried out under the same conditions as in Example 26, using Ru4 / Cu1-Co1-O·MgO catalyst with 6 mmol of magnesium oxide, at different oxygen pressures. The results are shown in Table 7.

[0103] Table 7 Effect of oxygen pressure on catalytic performance

[0104]

[0105] Table 7 shows that when the oxygen pressure is 0 MPa, the HMF conversion rate is 99.1%, the FDCA yield is only 9.6%, and the HFCA and FFCA yields are 31.5% and 12.8%, respectively. As the oxygen pressure increases to 0.5 MPa, HMF achieves complete conversion, the FDCA yield increases to 41.2%, and the HFCA and FFCA yields decrease to 0.7% and 5.4%, respectively. At an oxygen pressure of 1.0 MPa, 100% HMF conversion and 86.1% FDCA yield can be obtained. Therefore, the optimal oxygen pressure is set to 1.0 MPa.

[0106] Examples 26, 34, 35, 36, and 37:

[0107] The reaction conditions were the same as in Example 26, using Ru4 / Cu1-Co1-O·MgO catalyst with 6 mmol of magnesium oxide. The reaction results are shown in Table 8 when the amount of catalyst was different.

[0108] Table 8 Effect of catalyst dosage on catalytic performance

[0109]

[0110] Table 8 shows that when 0.02 g of catalyst was added to the reaction system, HMF was almost completely converted, with a conversion rate of 91.9%, and the yield of FDCA was 33.5%. The yield of FDCA increased with increasing catalyst dosage, reaching 86.1% when 0.08 g of catalyst was added. Further increasing the catalyst dosage to 0.1 g resulted in a decrease in the FDCA yield to 62.5%, while the yields of HFCA and FFCA were 3.4% and 9.8%, respectively. Therefore, the optimal catalyst dosage was set at 0.08 g.

[0111] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. The application of a ruthenium-supported copper-cobalt metal oxide composite magnesium oxide catalyst in the selective oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid, characterized in that: The selective oxidation reaction is carried out under alkali-free conditions; the catalyst preparation method includes the following steps: The following steps are performed sequentially: Step A1: Preparation of a copper-cobalt hydroxide precursor mixture; Preparation of the precursor mixture: Under vigorous stirring, a certain concentration of sodium hydroxide aqueous solution is added dropwise to a mixed solution of Cu(NO3)2•3H2O and Co(NO3)2•6H2O until the pH reaches 10, thus obtaining a copper-cobalt hydroxide precursor mixture; Step A2: The copper-cobalt hydroxide mixture obtained in Step A1 is subjected to hydrothermal calcination to obtain copper-cobalt precursor powder, and then mixed with anhydrous magnesium acetate. After grinding and calcination, a catalyst support was prepared. The support was prepared by: a copper-cobalt hydroxide mixture precursor undergoing a hydrothermal reaction, cooling to room temperature after the reaction, filtering and washing until neutral, and drying to obtain precursor powder; the precursor powder was thoroughly mixed and ground with anhydrous magnesium acetate, then calcined in air and cooled to room temperature to obtain a copper-cobalt metal oxide composite magnesium oxide support; Step A3: Ruthenium nanoparticles were loaded onto the support prepared in step A2 using an impregnation-reduction method, with the ruthenium loading accounting for 1-5 wt% of the support; loading of the active component: the copper-cobalt metal oxide composite magnesium oxide support was impregnated and dispersed in a RuCl3•3H2O aqueous solution, placed in an ice-water bath under stirring, and a NaBH4 aqueous solution containing NaOH was added dropwise while stirring and reducing; the mixture was filtered and washed until neutral, and then vacuum dried to obtain the ruthenium-loaded copper-cobalt metal oxide composite magnesium oxide catalyst.

2. The application according to claim 1, characterized in that: In step A1, the molar ratio of Cu(NO3)2•3H2O and Co(NO3)2•6H2O is 1:1, 1:2, or 2:

1.

3. The application according to claim 2, characterized in that: In step A1, a total of 6 mmol of Cu(NO3)2•3H2O and Co(NO3)2•6H2O are dissolved in 60 mL of deionized water in a certain ratio, and the concentration of the sodium hydroxide aqueous solution is 1~2 mol / L.

4. The application according to claim 1, characterized in that: In step A2, copper cobalt hydroxide precursor powder is weighed and mixed with anhydrous magnesium acetate. The hydrothermal temperature is 150~200 ℃, the hydrothermal time is 3~6 h, the calcination temperature is 300~500 ℃, and the calcination time is 3~6 h.

5. The application according to claim 1, characterized in that: In step A3, the carrier is weighed and dispersed in deionized water for 10-24 hours; RuCl3•3H2O contains Ru 3+ The molar ratio of NaBH4ˉ to NaBH4 is 1:15 to 1:25; the concentration of NaBH4 in the NaBH4 aqueous solution containing NaOH is 1 to 2 mol / L, the concentration of NaOH is 0.3 to 0.7 wt%, and the reduction time is 10 to 24 h.

6. The application according to claim 1, characterized in that: The raw material 5-hydroxymethylfurfural was dissolved in deionized water, and oxygen was introduced as the oxygen source. The raw material 5-hydroxymethylfurfural was selectively oxidized to synthesize the target product 2,5-furandicarboxylic acid by using a ruthenium-supported copper-cobalt metal oxide composite magnesium oxide catalyst.

7. The application according to claim 6, characterized in that, The application includes the following steps, performed sequentially: Step B1: Oxidation of 5-hydroxymethylfurfural. 5-hydroxymethylfurfural, deionized water, and a ruthenium-supported copper-cobalt metal oxide composite magnesium oxide catalyst are added to a reaction vessel. Oxygen is then introduced, and the reaction is carried out under heating and stirring conditions. After the reaction, the mixture is cooled to room temperature, the vent valve is opened to release the gas, and the catalyst is filtered out. The obtained reaction solution is diluted with pure water, and the diluted reaction solution is analyzed by high-performance liquid chromatography (HPLC) to calculate the conversion rate of the raw material 5-hydroxymethylfurfural and the yield of the target product 2,5-furandicarboxylic acid. Step B2: Separation and purification of 2,5-furandicarboxylic acid. The filtrate obtained after the reaction is collected, and 2,5-furandicarboxylic acid is separated using semi-preparative liquid chromatography with an ultraviolet detector. A C18 column is used, and the mobile phase is 0.1 wt% formic acid aqueous solution and methanol, with a volume ratio of 7:3 and a flow rate of 3.5%. The concentration of the solvent was increased to mL / min to obtain a solution containing 2,5-furandicarboxylic acid. Methanol and formic acid were removed by rotary evaporation to obtain 2,5-furandicarboxylic acid, which was then dried. The purity of the product 2,5-furandicarboxylic acid was analyzed by high performance liquid chromatography.

8. The application according to claim 6, characterized in that: 5-Hydroxymethylfurfural was dissolved in deionized water, the reaction temperature was 90~130 ℃, the reaction time was 8~16 h, the oxygen pressure was 0~1 MPa, and the amount of ruthenium-supported copper-cobalt metal oxide composite magnesium oxide catalyst was 0.02~0.1 g.

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