An electrooxidation system and method for promoting the conversion of 5-hydroxymethylfurfural into 2,5-diformylfuran

Abstract

The present invention discloses a method for promoting the efficient conversion of 5-hydroxymethylfurfural into 2,5-diformylfuran by in-situ extraction using an organic solvent, and belongs to the field of electrochemical synthesis and catalysis technology. The method is to achieve an electro-oxidation reaction of 5-hydroxymethylfurfural at room temperature and pressure by mixing an organic solvent with a conventional electrolyte to form an electrolyte in an anode reaction chamber. The 2,5-diformylfuran generated during the reaction is extracted in situ into an organic solvent, thereby effectively reducing its further oxidation and improving the product yield. By optimizing the electrolyte composition and reaction conditions, the present invention provides an electrochemical oxidation process with simple product separation and purification, low cost, and mild reaction conditions, which can be used for the industrial production of 2,5-diformylfuran and has potential application value.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical synthesis and catalysis, and in particular to an electrooxidation system for promoting the efficient conversion of 5-hydroxymethylfurfural into 2,5-diformylfuran. Background Art

[0002] Replacing fossil resources with renewable carbon sources is crucial for the sustainable production of chemicals. The electrocatalytic oxidation of 5-hydroxymethylfurfural provides an economical, efficient, environmentally friendly and mild way to utilize biomass resources. 2,5-Diformylfuran, as one of the oxidation products of 5-hydroxymethylfurfural, has two aldehyde functional groups and has typical chemical properties of aldehydes. It can be synthesized with different diamines to form Schiff bases, and with urea to synthesize new biomass-based resins, etc. It is an important precursor of furan-based polymers. It can also be used as a starting material for fine chemicals such as drugs, macrocyclic ligands, pesticides, organic ligands, and a cross-linking agent for polyvinyl alcohol in battery separators, and has high commercial value.

[0003] However, in conventional electrooxidation of 5-HMF, 2,5-diformylfuran is easily further oxidized to 5-formyl-2-furancarboxylic acid, resulting in reduced selectivity and yield of the target product. This is also a major challenge in the electrocatalytic selective oxidation of synthetic compounds. Therefore, the key to improving the yield of 2,5-diformylfuran in the electrooxidation of 5-HMF lies in preventing its further oxidation.

[0004] Here, we proposed a novel blocking mechanism. By adding an organic solvent with better solubility for 2,5-diformylfuran to the 5-hydroxymethylfurfural reaction system, the 2,5-diformylfuran organic solvent produced during the reaction was extracted in situ to prevent its further oxidation, thereby achieving rapid and high yield of 2,5-diformylfuran. Summary of the Invention

[0005] In view of the defects of the prior art, the present invention aims to provide a novel electro-oxidation system that utilizes in-situ extraction of an organic phase to promote the efficient conversion of 5-hydroxymethylfurfural to 2,5-diformylfuran. During the electro-oxidation of 5-hydroxymethylfurfural, an organic solvent with better solubility for the target product is added to extract the 2,5-diformylfuran produced during the reaction in situ, thereby preventing further oxidation of the target product during the reaction and improving the yield of 2,5-diformylfuran. The system is heated to 1.55V. RHE -1.75V RHE The yield of the target product 2,5-diformylfuran was 74.6%-81.9%.

[0006] To achieve the above object, the technical solutions adopted by the present invention are as follows:

[0007] An electrooxidation system that promotes the efficient conversion of 5-hydroxymethylfurfural to 2,5-diformylfuran uses a mixed solution consisting of an organic solvent with higher solubility for the product and a conventional electrolyte as the electrolyte, thereby extracting the target product in real time during the reaction, thereby increasing the yield of high-value-added products.

[0008] The pH of the 5-hydroxymethylfurfural electrooxidation system is ≤11, preferably 5.8-9.4.

[0009] The organic solvent includes dichloromethane, ethyl acetate and other organic solvents.

[0010] The mixed electrolyte is composed of an organic solvent and a conventional electrolyte such as PBS, NaHCO3 solution, with a preferred concentration of 0.2-2 mol / L.

[0011] The ratio of the organic phase to the aqueous phase in the mixed electrolyte is 1:1-1:5, preferably 1:2-1:4.

[0012] The rotation speed of the 5-hydroxymethylfurfural electro-oxidation system is 800-2000 r / min, preferably 1000-1500 r / min.

[0013] The concentration of the reaction substrate 5-hydroxymethylfurfural is 0.01 mol-0.2 mol / L, preferably 0.01-0.05 mol / L.

[0014] The method is carried out in an H-type electrolytic cell separated by a proton exchange membrane (Nafion 117); one or more of nickel oxide attached to a conductive substrate (such as carbon felt) or ruthenium-loaded nickel oxide attached to a conductive substrate (such as carbon felt) serves as a working electrode and is placed in an electrolyte in the anode chamber; the counter electrode is one or both of a carbon rod and a platinum sheet and is placed in an electrolyte in the cathode chamber. The cathode chamber electrolyte is composed of conventional electrolytes such as one or both of a PBS buffer solution and a NaHCO3 solution, preferably with a concentration of 0.5-1 mol / L.

[0015] The reaction potential of the 5-hydroxymethylfurfural electrooxidation system is 1.55V RHE -1.75V RHE .

[0016] The 5-hydroxymethylfurfural electrooxidation system is at a potential of 1.55V RHE -1.75V RHE When the reaction mixture is stirred for 2 h, the yield of 2,5-diformylfuran can be obtained in the range of 74.6% to 81.9%.

[0017] The principles of the present invention are as follows:

[0018] During the 5-hydroxymethylfurfural reaction, the 2,5-diformylfuran produced is rapidly extracted in situ by a more soluble organic solvent. The inertness of the organic solvent prevents further oxidation of the target product, thereby increasing product yield. This timely extraction of the target product and prevention of further oxidation are key to improving yield.

[0019] The method involves mixing an organic solvent with a conventional electrolyte to form the electrolyte in the anode reaction chamber, achieving an electro-oxidation reaction of 5-hydroxymethylfurfural at room temperature and pressure. The 2,5-diformylfuran generated during the reaction is extracted in situ into the organic solvent, effectively reducing its further oxidation and improving product yield.

[0020] The advantages of the present invention are as follows:

[0021] 1. The electrooxidation system of the present invention, which promotes the efficient conversion of 5-hydroxymethylfurfural to 2,5-diformylfuran, significantly improves the yield of 2,5-diformylfuran by optimizing the electrolyte environment in the anode chamber and rapidly extracting the target product during the reaction. This system achieves efficient conversion of 5-hydroxymethylfurfural to 2,5-diformylfuran in a neutral environment, facilitating the large-scale production of 2,5-diformylfuran.

[0022] 2. The electrooxidation system of the present invention for promoting the efficient conversion of 5-hydroxymethylfurfural to 2,5-diformylfuran utilizes the higher solubility of 2,5-diformylfuran in organic solvents to achieve spontaneous purification of the product during the reaction, thereby reducing the subsequent steps of product separation and purification.

[0023] 3. The electrooxidation system for promoting the efficient conversion of 5-hydroxymethylfurfural to 2,5-diformylfuran described in the present invention has the advantages of simple operation, easy product separation and purification, low cost, mild reaction conditions, and is conducive to large-scale production. It can be used for the industrial production of 2,5-diformylfuran and has potential application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a graph showing the change in DFF yield at different potentials when the 5-hydroxymethylfurfural electrooxidation system contains or does not contain an organic solvent;

[0025] Figure 2 This is a graph showing the change in DFF yield when the 5-hydroxymethylfurfural electrooxidation system contains different proportions of organic solvents;

[0026] Note: FFCA in the figure is 5-formyl-2-furoic acid, and DFF is 2,5-diformylfuran. DETAILED DESCRIPTION

[0027] Preparation of Ru-NiO / CF catalyst:

[0028] NiO / CF catalysts were prepared using a simplified electrodeposition-calcination method. First, a carbon felt (CF) sheet measuring 1 cm x 3 cm in length and width and 1 mm thick was immersed in 50 ml of a 100 mM NiSO₄·6H₂O aqueous solution. Electrodeposition was performed using a standard three-electrode system (CF as the working electrode, Pt wire as the counter electrode, and Hg / HgO as the reference electrode). The deposition potential was set at -0.8 V. RHE , the duration is 10 minutes. After electrodeposition, it is thoroughly washed with deionized water and ethanol in sequence, and dried at 60°C. Then, it is calcined at 350°C for 2 hours in an air atmosphere to obtain NiO / CF. Subsequently, Ru-NiO / CF is prepared by impregnation method, and 0.01gRuCl3·xH2O (the hydrate of ruthenium trichloride is usually a trihydrate) is dissolved in 10mL of ethanol to prepare an impregnation solution. The NiO / CF obtained above (with a size of 1cm×3cm) is immersed in the impregnation solution for 10 minutes, taken out and dried at 60°C. Finally, it is calcined at 350°C for 2 hours in an air atmosphere to obtain Ru-NiO / CF (the loading amount of Ru and NiO is 0.15mg / cm 2 , 4.16mg / cm 2 )catalyst.

[0029] Example 1:

[0030] The reaction was carried out in an H-type electrolytic cell separated by a proton exchange membrane (Nafion 117) using a three-electrode system. The Ru-NiO loaded on the carbon felt prepared above was used as the working electrode (placed in the electrolyte in the anode chamber), the platinum sheet was used as the counter electrode (placed in the electrolyte in the cathode chamber), and the silver / silver chloride was used as the reference electrode (placed in the electrolyte in the anode chamber).

[0031] The anode compartment electrolyte consisted of a 1 mol / L phosphate buffer solution (PBS, pH 7.4) (aqueous phase) containing the organic solvent dichloromethane (organic phase), with a volume ratio of 1:2 for a total volume of 15 ml. The concentration of the reactant 5-hydroxymethylfurfural was 0.01 mol / L.

[0032] The electrolyte in the cathode chamber is 1 mol / L phosphate buffer solution (PBS, pH=7.4) with a total volume of 15 ml.

[0033] At the reaction potential of 1.55 V RHE , 1.65V RHE , 1.75V RHE, the speed was 1500r / min, and the reaction was continued until the substrate was completely converted (about 170 minutes, 60 minutes, and 45 minutes, respectively). The yields of the product 2,5-diformylfuran were 81.3%, 81.9%, and 74.6%, respectively (such as Figure 1 shown).

[0034] Comparative Example 1:

[0035] The reaction was carried out in an H-type electrolytic cell separated by a proton exchange membrane (Nafion 117) using a three-electrode system. The Ru-NiO loaded on the carbon felt prepared above was used as the working electrode (placed in the electrolyte in the anode chamber), the platinum sheet was used as the counter electrode (placed in the electrolyte in the cathode chamber), and the silver / silver chloride was used as the reference electrode (placed in the electrolyte in the anode chamber).

[0036] The electrolyte in the anode chamber was composed of 1 mol / L phosphate buffer solution (PBS, pH=7.4), the concentration of the reactant 5-hydroxymethylfurfural was 0.01 mol / L, and the total volume was 15 ml.

[0037] The electrolyte in the cathode chamber is 1 mol / L phosphate buffer solution (PBS, pH=7.4) with a total volume of 15 ml.

[0038] At the reaction potential of 1.55 V RHE , 1.65V RHE , 1.75V RHE , the speed was 1500r / min, and the reaction was continued until the substrate was completely converted (about 1700 minutes, 600 minutes, and 450 minutes, respectively). The yields of the product 2,5-diformylfuran were 30.8%, 25.3%, and 18.2%, respectively (such as Figure 1 shown).

[0039] Example 2:

[0040] The reaction was carried out in an H-type electrolytic cell separated by a proton exchange membrane (Nafion 117) using a three-electrode system. The Ru-NiO loaded on the carbon felt prepared above was used as the working electrode (placed in the electrolyte in the anode chamber), the platinum sheet was used as the counter electrode (placed in the electrolyte in the cathode chamber), and the silver / silver chloride was used as the reference electrode (placed in the electrolyte in the anode chamber).

[0041] The anodic electrolyte consisted of 1 mol / L phosphate buffer solution (PBS, pH 7.4) (aqueous phase) and dichloromethane (organic phase). The organic phase to aqueous phase ratios were 1:2, 1:3, and 1:4, respectively, for a total volume of 15 mL. The concentration of the reactant, 5-hydroxymethylfurfural, was 0.01 mol / L.

[0042] The electrolyte in the cathode chamber is 1 mol / L phosphate buffer solution (PBS, pH=7.4) with a total volume of 15 ml.

[0043] At a reaction potential of 1.75 V RHE , the reaction was carried out at a speed of 1500 r / min until the substrate was completely converted (approximately 50 minutes, 45 minutes, and 80 minutes, respectively), and the yields of the product 2,5-diformylfuran were 74.6%, 68.9%, and 57.6%, respectively (corresponding to the volume ratio of dichloromethane to water phase in the anode compartment electrolyte of 1:2, 1:3, and 1:4, respectively) (such as Figure 2 shown).

Claims

1. A method for promoting the electrooxidation reaction of 5-hydroxymethylfurfural into 2,5-diformylfuran, characterized in that: The method is carried out in an H-type electrolytic cell separated by a proton exchange membrane; one or more of nickel oxide attached to a conductive substrate or ruthenium-loaded nickel oxide attached to a conductive substrate is used as a working electrode and is placed in an anode chamber electrolyte, wherein the components of the anode chamber electrolyte are composed of 5-hydroxymethylfurfural, an organic solvent and a conventional electrolyte; the counter electrode is one or more of a carbon rod or a platinum sheet and is placed in a cathode chamber electrolyte, wherein the components of the cathode chamber electrolyte are a conventional electrolyte; The conventional electrolyte is one or both of PBS buffer solution and NaHCO3 solution; The organic solvent includes one or both of dichloromethane and ethyl acetate.

2. The electrooxidation method for promoting the conversion of 5-hydroxymethylfurfural into 2,5-diformylfuran according to claim 1, characterized in that: The concentrations of the PBS buffer solution and the NaHCO3 solution are 0.2-2 mol / L respectively.

3. The electrooxidation method for promoting the conversion of 5-hydroxymethylfurfural into 2,5-diformylfuran according to claim 1, characterized in that: The concentrations of the PBS buffer solution and the NaHCO3 solution are 0.5-1 mol / L respectively.

4. The electrooxidation method for promoting the conversion of 5-hydroxymethylfurfural into 2,5-diformylfuran according to claim 1, characterized in that: The pH of the 5-hydroxymethylfurfural electrooxidation reaction in the anode chamber electrolyte is ≤11.

5. The electrooxidation method for promoting the conversion of 5-hydroxymethylfurfural into 2,5-diformylfuran according to claim 1, characterized in that: The pH of the 5-hydroxymethylfurfural electrooxidation reaction in the anode chamber electrolyte is 5.8-9.

4.

6. The electrooxidation method for promoting the conversion of 5-hydroxymethylfurfural into 2,5-diformylfuran according to claim 1, characterized in that: The volume ratio of the organic solvent to the conventional electrolyte in the anode chamber electrolyte is 1:1-1:

5.

7. The electrooxidation method for promoting the conversion of 5-hydroxymethylfurfural into 2,5-diformylfuran according to claim 1, characterized in that: The volume ratio of the organic solvent to the conventional electrolyte in the anode chamber electrolyte is 1:2-1:

4.

8. The electrooxidation method for promoting the conversion of 5-hydroxymethylfurfural into 2,5-diformylfuran according to claim 1, characterized in that: The concentration of the reaction substrate 5-hydroxymethylfurfural in the anode chamber electrolyte is 0.01-0.2 mol / L.

9. The electrooxidation method for promoting the conversion of 5-hydroxymethylfurfural into 2,5-diformylfuran according to claim 1, characterized in that: The concentration of the reaction substrate 5-hydroxymethylfurfural in the anode chamber electrolyte is 0.01-0.05 mol / L.

10. The electrooxidation method for promoting the conversion of 5-hydroxymethylfurfural into 2,5-diformylfuran according to claim 1, characterized in that: The electrooxidation reaction potential of the method for promoting the conversion of 5-hydroxymethylfurfural into 2,5-diformylfuran is 1.55-1.75 V. RHE .

11. The electrooxidation method for promoting the conversion of 5-hydroxymethylfurfural into 2,5-diformylfuran according to claim 10, characterized in that: The electro-oxidation reaction is carried out under stirring, and the stirring speed of the electro-oxidation reaction for promoting the conversion of 5-hydroxymethylfurfural into 2,5-diformylfuran is 800-2000 r / min.

12. The electrooxidation method for promoting the conversion of 5-hydroxymethylfurfural into 2,5-diformylfuran according to claim 11, characterized in that: The stirring speed for promoting the electrooxidation reaction of 5-hydroxymethylfurfural to be converted into 2,5-diformylfuran is 1000-1500 r / min.

13. The electrooxidation method for promoting the conversion of 5-hydroxymethylfurfural into 2,5-diformylfuran according to any one of claims 10 to 12, characterized in that: The electrooxidation reaction of promoting 5-hydroxymethylfurfural to 2,5-diformylfuran at a potential of 1.55-1.75 V RHE When the reaction mixture was stirred for 2 h, the yield of 2,5-diformylfuran was 74.6%-81.9%.

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