Electrooxidation system and method for promoting conversion of 5-hydroxymethylfurfural into 2, 5-diformyl furan

Abstract

The invention discloses a method for promoting efficient conversion of 5-hydroxymethylfurfural into 2, 5-diformyl furan by utilizing in-situ extraction of an organic solvent, and belongs to the technical field of electrochemical synthesis and catalysis. According to the method, an organic solvent and a conventional electrolyte are mixed to form an electrolyte of an anode reaction chamber, and an electrooxidation reaction of 5-hydroxymethylfurfural is realized at normal temperature and normal pressure. 2, 5-diformyl furan generated in the reaction process is extracted in situ and enters the organic solvent, so that further oxidation of 2, 5-diformyl furan is effectively reduced, and the product yield is improved. By optimizing electrolyte composition and reaction conditions, the invention provides an electrochemical oxidation process which is simple and convenient in product separation and purification, low in cost and mild in reaction condition, can be used for industrial production of 2, 5-diformyl furan, and has potential application value.

Description

Technical Field

[0001] The invention relates to the technical field of electrochemical synthesis and catalysis, and in particular to an electro-oxidation 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 used to synthesize Schiff bases with different diamines and to synthesize new biomass-based resins with urea, 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 the traditional electro-oxidation process of 5-hydroxymethylfurfural, 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 electro-oxidation reaction of 5-hydroxymethylfurfural is to prevent it from further oxidation.

[0004] Here, we proposed a new blocking mechanism. By adding an organic solvent with better solubility for 2,5-diformylfuran into 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 into 2,5-diformylfuran. In the electro-oxidation process of 5-hydroxymethylfurfural, an organic solvent with better solubility for the target product is added to extract the 2,5-diformylfuran produced in the reaction process in situ, thereby preventing the target product from being further oxidized during the reaction, thereby increasing the yield of 2,5-diformylfuran. The system is heated to 1.55 V. RHE -1.75V RHE The yield of the target product 2,5-diformylfuran was 74.6%-81.9%.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] An electro-oxidation system for promoting the efficient conversion of 5-hydroxymethylfurfural into 2,5-diformylfuran uses a mixed solution consisting of an organic solvent with higher solubility for the product and a conventional electrolyte as an electrolyte, and extracts 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 electro-oxidation 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, and the preferred concentration is 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 800r / min-2000r / min, preferably 1000-1500r / 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) is used as a working electrode and is placed in an electrolyte in the anode chamber; the counter electrode is one or two of a carbon rod or a platinum sheet and is placed in an electrolyte in the cathode chamber, and the composition of the electrolyte in the cathode chamber is a conventional electrolyte, which is one or two of a PBS buffer solution and a NaHCO3 solution, and the preferred concentration is 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 reacted with water, the yield of 2,5-diformylfuran can be obtained in the range of 74.6% to 81.9%.

[0017] The principle of the present invention is as follows:

[0018] During the reaction of the 5-hydroxymethylfurfural system, the generated 2,5-diformylfuran is quickly extracted in situ by an organic solvent with better solubility. Due to the reaction inertness of the organic solvent, the target product can be prevented from being further oxidized, thereby increasing the product yield. The timely extraction of the target product and prevention of further oxidation are the key to improving the yield.

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

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

[0021] 1. The electro-oxidation system for promoting the efficient conversion of 5-hydroxymethylfurfural into 2,5-diformylfuran of the present invention can significantly improve the yield of 2,5-diformylfuran by optimizing the electrolyte environment of the anode chamber and rapidly extracting the target product during the reaction process. The efficient conversion of 5-hydroxymethylfurfural into 2,5-diformylfuran in a neutral environment is achieved, which is conducive to the large-scale production of 2,5-diformylfuran.

[0022] 2. The electro-oxidation system for promoting the efficient conversion of 5-hydroxymethylfurfural into 2,5-diformylfuran of the present invention 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 separation and purification of the product.

[0023] 3. The electro-oxidation system for promoting the efficient conversion of 5-hydroxymethylfurfural into 2,5-diformylfuran of the present invention has the advantages of simple operation method, simple 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 The DFF yield change diagram at different potentials when the 5-hydroxymethylfurfural electro-oxidation 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 electro-oxidation system contains different proportions of organic solvents;

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

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

[0028] NiO / CF catalyst was prepared by simple electrodeposition-calcination method. First, carbon felt (CF) with a length × width of 1 cm × 3 cm and a thickness of 1 mm was immersed in 50 ml of an aqueous solution containing 100 mM NiSO4·6H2O. Electrodeposition was performed in 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 to -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 an 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 (size of 1cm×3cm) was immersed in the impregnation solution for 10 minutes, taken out and dried at 60°C. Finally, it was calcined at 350°C for 2 hours in an air atmosphere to obtain Ru-NiO / CF (the loading amounts of Ru and NiO, respectively, were 0.15mg / cm 2 , 4.16mg / cm 2 )catalyst.

[0029] Embodiment 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, with the Ru-NiO loaded on the carbon felt prepared as above as the working electrode (placed in the electrolyte in the anode chamber), the platinum sheet as the counter electrode (placed in the electrolyte in the cathode chamber), and the silver / silver chloride as the reference electrode (placed in the electrolyte in the anode chamber).

[0031] The electrolyte in the anode chamber is composed of a 1 mol / L phosphate buffer solution (PBS, pH=7.4) solution (aqueous phase) containing an organic solvent dichloromethane (organic phase), the volume ratio of the organic phase to the aqueous phase is 1:2, and the total volume is 15 ml. The concentration of the reactant 5-hydroxymethylfurfural is 0.01 mol / L.

[0032] The cathode chamber electrolyte is a 1 mol / L phosphate buffer solution (PBS, pH=7.4) solution 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, the reaction was continued until the substrate was completely converted (about 170 minutes, 60 minutes, and 45 minutes, respectively), and 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, with the Ru-NiO loaded on the carbon felt prepared as above as the working electrode (placed in the electrolyte in the anode chamber), the platinum sheet as the counter electrode (placed in the electrolyte in the cathode chamber), and the silver / silver chloride as the reference electrode (placed in the electrolyte in the anode chamber).

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

[0037] The electrolyte in the cathode chamber is a 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, the reaction lasted until the substrate was completely converted (about 1700 minutes, 600 minutes, and 450 minutes, respectively), and the yields of the product 2,5-diformylfuran were 30.8%, 25.3%, and 18.2%, respectively (such as Figure 1 shown).

[0039] Embodiment 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, with the Ru-NiO loaded on the carbon felt prepared as above as the working electrode (placed in the electrolyte in the anode chamber), the platinum sheet as the counter electrode (placed in the electrolyte in the cathode chamber), and the silver / silver chloride as the reference electrode (placed in the electrolyte in the anode chamber).

[0041] The electrolyte in the anode chamber is composed of 1 mol / L phosphate buffer solution (PBS, pH=7.4) (aqueous phase) and dichloromethane solution (organic phase), and the volume ratio of the organic phase to the aqueous phase in the electrolyte system of the anode chamber is 1:2, 1:3, 1:4, and the total volume is 15 ml. The concentration of the reactant 5-hydroxymethylfurfural is 0.01 mol / L.

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

[0043] At the 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 chamber electrolyte of 1:2, 1:3, and 1:4, respectively) (such as Figure 2 shown).

Claims

1. An electro-oxidation system for promoting the conversion of 5-hydroxymethylfurfural into 2,5-diformylfuran, characterized in that: In the 5-hydroxymethylfurfural electro-oxidation reaction system, an organic solvent with higher solubility for the target product 2,5-diformylfuran is added to extract 2,5-diformylfuran in situ, thereby improving the yield of the target product.

2. The electro-oxidation system for promoting the conversion of 5-hydroxymethylfurfural into 2,5-diformylfuran according to claim 1, characterized in that: The pH of the 5-hydroxymethylfurfural electro-oxidation system is ≤11, preferably 5.8-9.

4.

3. The electro-oxidation system for promoting the conversion of 5-hydroxymethylfurfural into 2,5-diformylfuran according to claim 1, characterized in that: The organic solvent includes one or both of dichloromethane and ethyl acetate.

4. The electro-oxidation system for promoting the conversion of 5-hydroxymethylfurfural into 2,5-diformylfuran according to claim 1, characterized in that: The 5-hydroxymethylfurfural electro-oxidation reaction system is composed of an organic solvent with a higher solubility for the target product 2,5-diformylfuran and a conventional electrolyte (aqueous phase). The conventional electrolyte is one or both of a PBS buffer solution and a NaHCO3 solution. The concentrations of the PBS buffer solution and the NaHCO3 solution are 0.2-2 mol / L, respectively, and preferably 0.5-1 mol / L.

5. The electro-oxidation system for promoting the conversion of 5-hydroxymethylfurfural into 2,5-diformylfuran according to claim 1, 3 or 4, characterized in that: The volume ratio of the organic solvent to the conventional electrolyte (aqueous phase) in the electro-oxidation reaction system is 1:1-1:5, preferably 1:2-1:

4.

6. The electro-oxidation system for promoting the conversion of 5-hydroxymethylfurfural into 2,5-diformylfuran according to any one of claims 1 to 5, characterized in that: The concentration of the reaction substrate 5-hydroxymethylfurfural is 0.01-0.2 mol / L, preferably 0.01-0.05 mol / L.

7. A method for carrying out a reaction using the electro-oxidation system for promoting the conversion of 5-hydroxymethylfurfural into 2,5-diformylfuran according to any one of claims 1 to 6, characterized in that: The method is carried out in an H-type electrolytic cell separated by a proton exchange membrane (such as 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) is used as a working electrode and is placed in an anode chamber electrolyte, and the composition of the anode chamber electrolyte is the electro-oxidation system for promoting the conversion of 5-hydroxymethylfurfural into 2,5-diformylfuran described in any one of claims 1-6; the counter electrode is one or two of a carbon rod or a platinum sheet, and is placed in a cathode chamber electrolyte, and the composition of the cathode chamber electrolyte is a conventional electrolyte, which is one or two of a PBS buffer solution and a NaHCO3 solution, and the concentrations of the PBS buffer solution and the NaHCO3 solution are 0.2-2 mol / L, respectively, and the preferred concentration is 0.5-1 mol / L.

8. The method according to claim 7, characterized in that: The reaction potential of the 5-hydroxymethylfurfural electrooxidation system is 1.55-1.75V RHE .

9. The method according to claim 7, characterized in that: The reaction is carried out under stirring, and the stirring speed of the 5-hydroxymethylfurfural electro-oxidation system is 800-2000 r / min, preferably 1000-1500 r / min.

10. The method according to claim 7, 8 or 9, characterized in that: The 5-hydroxymethylfurfural electro-oxidation system is at a potential of 1.55-1.75V RHE When the reaction mixture is reacted with water, the yield of 2,5-diformylfuran can be obtained in the range of 74.6% to 81.9%.

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