Method for generating dff based on catalytic oxidation of hmf by an acidic phosphovanadomolybdate mixed system coupled with hydrogen production by electrolysis

Abstract

The application discloses a method for generating DFF by catalytic oxidation of HMF based on an acid phosphorus vanadium polyacid mixed system and an electrolysis coupling hydrogen production process, and belongs to the technical field of biomass conversion. The method comprises the following steps: adding HMF into an acid phosphorus vanadium polyacid mixed solution, and generating DFF at normal temperature; wherein a preparation method of the acid phosphorus vanadium polyacid mixed solution comprises the following steps: forming a phosphorus vanadium polyacid by mixing a vanadium-based compound with phosphoric acid, and then adding a strong acid to obtain a red-brown acid phosphorus vanadium polyacid mixed solution. The acid phosphorus vanadium polyacid mixed solution is used as a catalytic oxidation system, HMF can be converted into DFF with high selectivity, the acid phosphorus vanadium polyacid mixed solution can be recycled for multiple times, and the hydrogen production efficiency is high when the acid phosphorus vanadium polyacid mixed solution is regenerated by coupling electrolysis hydrogen production technology, so that the acid phosphorus vanadium polyacid mixed solution has high industrial application value.

Description

Technical Field

[0001] The present invention belongs to the technical field of biomass conversion, and more specifically, relates to a hydrogen production process based on the catalytic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF) by an acidic vanadium-phosphoacid mixed system and coupled with electrolysis. Background Art

[0002] 5-Hydroxymethylfurfural (HMF) is a key biomass-derived platform molecule. Its structure contains abundant functional groups such as aldehyde, hydroxyl and furan ring. It can be converted into high-value-added chemicals such as 2,5-diformylfuran (DFF) and 2,5-furandicarboxylic acid (FDCA) through a variety of chemical reactions. Among them, DFF, as a renewable monomer, is considered to be a key precursor for the preparation of bio-based polymers and is widely used in medicine, antifungal agents, furanurea resins, green plastics and other fields. Vanadium-based catalysts have significant advantages in the catalytic oxidation reactions of organic compounds due to their diverse valence characteristics, especially in the selective oxidation of alcohols. Chinese patents CN119977921A and CN118894822A reported that vanadyl sulfate was used as a catalyst to convert HMF into DFF. 5+ As an active substance, it participates in the reaction. Although the oxidation of HMF by (VO2)2SO4 can obtain a higher HMF conversion rate and DFF yield, the stability of pentavalent vanadium solution is poor and it is easy to precipitate V2O5, which limits its industrial application. Chinese patent CN 119500202 A proposes a novel vanadium ionization process based on H5PMo 10 V2O 40 The polyacid catalytic system converts fructose into DFF, but requires high temperature (120-140 o C) and high-pressure oxygen (1 MPa) conditions require a long reaction time. Therefore, the existing technology for oxidizing HMF to prepare DFF needs to be improved. Summary of the Invention

[0003] This invention addresses the shortcomings of existing technologies for converting 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF), which suffer from unstable catalytic systems at room temperature and difficulty in recycling. Instead, it proposes a method for catalytically oxidizing HMF to produce DFF using an acidic phosphovanadic acid mixed solution. Using this acidic phosphovanadic acid mixed solution as both catalyst and oxidant, the method efficiently converts HMF to DFF, exhibits excellent catalyst stability, and is less susceptible to V2O5 precipitation. Coupled with an electrolytic hydrogen production process, the used acidic phosphovanadic acid mixed solution can be regenerated and recycled via electrolysis, eliminating the need for high-pressure oxygen. Simultaneously, hydrogen is evolved at the cathode to produce green hydrogen energy.

[0004] The technical solution of the present invention to solve the above technical problems is as follows:

[0005] Based on the method of catalytically oxidizing HMF to produce 2,5-diformylfuran using an acidic phosphovanadic polyacid mixed system, HMF is added to the acidic phosphovanadic polyacid mixed solution and reacted at room temperature to 60°C to produce DFF; wherein the preparation method of the acidic phosphovanadic polyacid mixed solution comprises the following steps:

[0006] The vanadium-based compound and phosphoric acid form phosphovanadium polyacid, and then a strong acid is added to obtain a reddish-brown acidic phosphovanadium polyacid mixed solution.

[0007] Preferably, the vanadium-based compound includes any one of vanadium pentoxide and vanadates, and the vanadates include any one or more of sodium metavanadate, sodium orthovanadate, sodium pyrovanadate, ammonium metavanadate, ammonium orthovanadate, ammonium pyrovanadate, potassium metavanadate, potassium orthovanadate or potassium pyrovanadate.

[0008] Preferably, the strong acid comprises sulfuric acid or nitric acid.

[0009] Preferably, the strong acid is sulfuric acid.

[0010] Preferably, the concentration of sulfuric acid in the acidic phosphovanadium polyacid solution is 0.9-4 mol / L.

[0011] Preferably, the concentration of the phosphoric acid is 0.3-0.6 mol / L.

[0012] Preferably, the molar ratio of the phosphoric acid to V in the vanadium-based compound is 1:2-4.

[0013] Preferably, the acidic vanadium-phosphoacid mixed solution contains V 5+ The concentration is 1-1.4 mol / L.

[0014] Preferably, the HMF and the acidic vanadium phosphoacid mixed solution are 5+ The molar ratio is 10:0.5-30.

[0015] Preferably, the reaction temperature is 25-60° C. and the reaction time is 0.5-4 h.

[0016] Among them, the key components of the acidic vanadium phosphoacid mixed solution are vanadium phosphoacid H9[PV 14 O 42 ] and the phosphovanadic acid H9[PV 14 O 42 ] structural degradation products and VO2 + Ions. The key components of the acidic vanadium-phosphoacid mixed solution play a vital role in maintaining the oxidation activity and stability of the catalytic system. A single acidic sodium metavanadate (sulfuric acid) solution does not have the same stability.

[0017] An electrolysis-coupled hydrogen production process, in which the acidic phosphovanadic polyacid mixed solution (blue) produced by catalytically oxidizing HMF to produce DFF is transferred to an electrolytic cell equipped with graphite electrodes for regeneration and coupled hydrogen production.

[0018] Preferably, the regeneration applied voltage is 0.8-1.2V.

[0019] The acidic vanadium-phosphoacid mixed solution of the present invention is subjected to catalytic oxidation reaction, wherein V 5+ ions (reddish brown) are reduced to V 4+ The ions (blue) are regenerated by electrolysis and converted back into a reddish-brown acidic phosphovanadic acid mixed solution, which is recycled for the conversion of 5-hydroxymethylfurfural into 2,5-diformylfuran.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The acidic vanadium phosphoacid mixed solution system of the present invention exhibits excellent strong oxidizing properties. Under room temperature conditions, the vanadium phosphoacid H9[PV 14 O 42 ] and the phosphovanadium polyacid H9[PV 14 O 42 ] structural degradation products and VO2 + The ions act as active sites for the reaction, significantly increasing the oxidation reaction rate and achieving a DFF yield exceeding 92%. This catalytic system exhibits excellent stability. Compared to a single acidic sodium metavanadate (sulfuric acid) solution, it does not precipitate V2O5 over long-term use. Furthermore, the catalytic system can be regenerated and recycled using electrolysis-coupled hydrogen production technology. The regenerated acidic vanadium-phosphoacid mixed solution system maintains essentially unchanged activity, producing high hydrogen production efficiency during regeneration, and possesses high industrial application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The acidic phosphate vanadium polyacid mixed solution system in the embodiment of the present invention is 51 V NMR spectrum.

[0023] Figure 2 This is the effect of different H2SO4 concentrations on DFF yield in Example 2 of the present invention.

[0024] Figure 3 This is the effect of different H3PO4 concentrations on DFF yield in Example 3 of the present invention.

[0025] Figure 4 This is the effect of different reaction temperatures on the DFF yield in Example 4 of the present invention.

[0026] Figure 5This is the regeneration electrolysis curve of the acidic phosphovanadium polyacid mixed solution in Example 5 of the present invention.

[0027] Figure 6 This is the cyclic catalytic performance result of the acidic phosphorus-vanadium polyacid mixed solution in Example 6 of the present invention.

[0028] Figure 7 This is the effect of different strong acids on the cyclic catalytic performance of the acidic phosphovanadium polyacid mixed solution in Example 7 of the present invention.

[0029] Figure 8 This is the effect on DFF yield when no phosphoric acid is added in Comparative Example 1 of the present invention.

[0030] Figure 9 This is the effect of the simple vanadyl sulfate catalyst on the DFF yield in Comparative Example 2 of the present invention.

[0031] Figure 10 This is the effect on DFF yield without adding sulfuric acid in Comparative Example 3 of the present invention. DETAILED DESCRIPTION

[0032] The following description sets forth numerous specific details to facilitate a thorough understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art may make similar modifications without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific implementations disclosed below.

[0033] Existing catalytic systems for converting 5-hydroxymethylfurfural to 2,5-diformylfuran generally suffer from poor stability at room temperature. Traditional vanadium-based catalysts are susceptible to hydrolysis or polymerization in acidic environments, resulting in the precipitation of active components. Catalytic efficiency decreases significantly with increasing reaction times. Some technical solutions utilize high temperature and high pressure to maintain catalytic activity, but these solutions are energy-intensive and pose safety risks, making industrial application difficult.

[0034] Therefore, this application proposes a method for catalytically oxidizing 5-hydroxymethylfurfural to produce 2,5-diformylfuran based on an acidic phosphovanadium polyacid mixed solution system. 5-Hydroxymethylfurfural is added to the acidic phosphovanadium polyacid mixed solution to achieve room-temperature catalytic oxidation. The mixed solution is prepared by reacting a vanadium-based compound with phosphoric acid to form a phosphovanadium polyacid, which is then acidified with a strong acid. Furthermore, the mixed solution can be prepared by dissolving the vanadium-based compound in hot water, adding phosphoric acid to form the phosphovanadium polyacid, and then adding the polyacid to adjust the acidity.

[0035] Among them, vanadium-based compounds refer to substances that can provide a pentavalent vanadium source, which can be specifically achieved by vanadium pentoxide or vanadates. The function of phosphoric acid is to form a phosphovanadium polyacid coordination structure with the vanadium-based compound to inhibit the hydrolysis and precipitation of the vanadium element. The strong acid environment can maintain the oxidation ability of the structure. Through the synergistic effect of phosphovanadium polyacid and strong acid, a catalytic system with both stability and oxidation activity is constructed. The reddish-brown acidic phosphovanadium polyacid mixed solution refers to a homogeneous solution in which the vanadium element exists in a pentavalent state. This feature indicates that a stable polyacid coordination structure has been formed.

[0036] Specifically, vanadium-based compounds undergo hydrolysis in a phosphoric acid solution, with phosphates and vanadium oxides forming phosphovanadium polyacid anions through coordination. The addition of a strong acid maintains the solution's strong acidity, allowing the protonated polyacid structure to be stably dispersed in the solution. When 5-hydroxymethylfurfural is added to the system, the pentavalent vanadium in the phosphovanadium polyacid acts as an electron acceptor, capturing the hydrogen atoms on the hydroxymethyl group and oxidizing it to an aldehyde group. Due to the steric hindrance of the polyacid structure, the reaction selectively targets the target product, 2,5-diformylfuran. Throughout the oxidation process, the vanadium element remains soluble in the solution, avoiding the deactivation problem associated with traditional vanadium salt catalysts.

[0037] Compared to existing technologies, traditional vanadyl sulfate systems tend to precipitate vanadium pentoxide after the reaction. This solution, however, stabilizes the vanadium element within the phosphovanadic acid structure, maintaining a homogeneous catalyst. Compared to heteropolyacid catalytic systems that require high temperatures and pressures, this solution achieves efficient oxidation at room temperature, eliminating the need for oxygen pressurization equipment.

[0038] Furthermore, vanadates include any one or more of sodium metavanadate, sodium orthovanadate, sodium pyrovanadate, ammonium metavanadate, ammonium orthovanadate, ammonium pyrovanadate, potassium metavanadate, potassium orthovanadate or potassium pyrovanadate. Vanadates have high solubility under acidic conditions, and different cations can be adapted to different reaction conditions, such as sodium salts are more stable in strongly acidic systems. Different anionic structures such as metavanadate, orthovanadate or pyrovanadate can be achieved by adjusting the coordination state of the phosphovanadic acid, thereby affecting catalytic activity and stability.

[0039] Specifically, vanadate releases V in acidic solution. 5+ ions, preventing V2O5 precipitation due to localized oversaturation. The sodium, ammonium, or potassium ions in vanadates maintain system stability by balancing the solution charge. The anionic structure of different vanadates influences the polymeric morphology of phosphovanadic polyacids. For example, metavanadate combines with phosphoric acid to form a heteropolyacid with a specific structure, enhancing its oxidizing ability. Ammonium salts may decompose and produce gas at high temperatures, while sodium or potassium salts remain stable under acidic conditions at room temperature. Therefore, the appropriate vanadate can be selected based on the reaction conditions.

[0040] Through the above technical solution, the present application solves the problem of insufficient stability of vanadium-based catalysts in acidic systems. By optimizing the type and coordination form of vanadium sources, the formation of V2O5 precipitation is suppressed and the dissolved state of catalytically active components is maintained. The high solubility of vanadates ensures that V 5+ It continuously participates in the oxidation reaction and improves the HMF conversion efficiency. At the same time, the flexible selection of different vanadates supports the stable operation of the catalytic system under various reaction conditions.

[0041] Furthermore, the strong acid includes sulfuric acid or trifluoromethanesulfonic acid. Sulfuric acid refers to an inorganic acid containing sulfate ions, and can be specifically implemented using a sulfuric acid solution with a concentration of 0.9-4 mol / L. It maintains the stability of the phosphovanadium polyacid structure by providing a moderate proton concentration, while avoiding excessive acidity that causes hydrolysis of pentavalent vanadium. Trifluoromethanesulfonic acid refers to an organic superacid containing trifluoromethanesulfonate ions, and can be specifically implemented using a pure liquid or diluted trifluoromethanesulfonic acid solution. It enhances the solution acidity through its strong dissociation characteristics, promoting the existence of vanadium species in dissolved form.

[0042] Specifically, sulfuric acid, as a strong proton acid, plays a dual role in the system: first, by completely ionizing and generating high concentrations of hydrogen ions, it inhibits the hydrolysis of pentavalent vanadium and prevents the formation of V2O5 precipitation; second, by coordinating sulfate anions with vanadium oxygen groups, it stabilizes the framework structure of the phosphovanadic acid. During the catalytic oxidation reaction, the acidic environment maintained by sulfuric acid keeps the vanadium species in the +5 valence state, ensuring a continuous supply of oxidizing power while preventing deactivation of the active components due to structural collapse. Trifluoromethanesulfonic acid, through its super-strong acidity, maintains a highly dispersed state of the vanadium species in the solution, maintaining catalytic activity even at room temperature. These two acids are chosen for different application scenarios: sulfuric acid is suitable for conventional industrial conditions, while trifluoromethanesulfonic acid is suitable for specific reaction systems that require extreme acidity without the risk of precipitation. The synergistic effect of these strong acids stabilizes the vanadium species at room temperature, eliminating the need for high temperatures or high-pressure oxygen, and avoiding the recyclability issues caused by catalyst precipitation.

[0043] Through the above technical solution, the present application solves the problem that pentavalent vanadium solution is easily deactivated in room temperature reactions, and constructs a catalytic system that can operate stably under normal pressure. The sulfuric acid system takes into account both economy and stability, and the trifluoromethanesulfonic acid system provides technical feasibility for special reaction requirements.

[0044] Furthermore, the phosphoric acid concentration is 0.3-0.6 mol / L. Within this concentration range, phosphoric acid can form a stable vanadium-phospho-polyacid coordination structure with the vanadium-based compound, preventing excess free phosphoric acid from causing an imbalance in the solution's acidity. When the phosphoric acid concentration is lower than 0.3 mol / L, it lacks sufficient phosphorus to form a stable polyacid complex with the vanadium-based compound. When the concentration is higher than 0.6 mol / L, the excess phosphoric acid disrupts the coordination equilibrium of the vanadium-phospho-polyacid, leading to the precipitation of the active group.

[0045] Specifically, when the phosphoric acid concentration is controlled at 0.3-0.6 mol / L, it can ensure that the phosphorus element forms a stable coordination structure with the vanadium ions in the vanadium-based compound. This concentration range not only meets the stoichiometric requirements for the formation of the phosphate-vanadium polyacid complex, but also avoids the problem of decreased proton transfer efficiency in the solution caused by excessive phosphoric acid. Under these conditions, the hydrolysis tendency of the vanadium species is suppressed, and the active components are stably present in the solution in a soluble state, thereby maintaining the continuous and efficient progress of the catalytic oxidation reaction. For example, when the phosphoric acid concentration is within this range, the coordination reaction between the vanadium-based compound and phosphoric acid tends to be complete, and the formed phosphate-vanadium polyacid complex can effectively catalyze the hydroxyl oxidation of HMF while avoiding the formation of vanadyl phosphate precipitation or V2O5 precipitation.

[0046] Through the above technical solution, the present application achieves improved stability of the phosphate-vanadium polyacid mixed solution system, avoiding the precipitation or inactivation of active components due to inappropriate phosphoric acid concentration. Furthermore, this concentration range ensures efficient catalytic oxidation reaction, enabling the continuous conversion of HMF to DFF, and maintaining long-term stability of the reaction system without the need for additional adjustment.

[0047] Furthermore, the molar ratio of phosphoric acid to vanadium in the vanadium-based compound is controlled within a range of 1:2 to 1:4. This ratio balances the coordination capacity of phosphoric acid with the concentration of vanadium, forming a stable phosphovanadium polyacid structure. This phosphovanadium polyacid structure stabilizes high-valent vanadium species, preventing them from hydrolyzing or aggregating to form precipitates.

[0048] Specifically, when the molar ratio of phosphoric acid to vanadium is less than 1:2, the vanadium element cannot be fully coordinated, and the uncoordinated pentavalent vanadium easily hydrolyzes to form V2O5 precipitates. When the ratio is higher than 1:4, the excess phosphoric acid competes for adsorption on the vanadium active sites, causing the polyacid structure to dissociate and form phosphovanadic acid precipitates. By limiting the ratio to 1:2-4, phosphoric acid can both act as a ligand with vanadium to form a stable [PVnOm]-type polyacid anion and maintain a suitable concentration of active vanadium species in solution. Within this range, the vanadium-oxygen skeleton in the phosphovanadic polyacid forms a three-dimensional network structure through phosphoric acid bridging, effectively inhibiting the irreversible aggregation of vanadium species while retaining sufficient catalytically active sites for oxidation reactions.

[0049] Through the above technical solution, this application solves the problem of catalyst deactivation caused by an imbalance in the ratio of vanadium-based compounds to phosphoric acid. By precisely controlling the molar ratio of phosphoric acid to vanadium, the hydrolysis and precipitation of uncoordinated vanadium is prevented, while the damage to the polyacid structure caused by excess phosphoric acid is avoided. This allows the catalytic system to maintain its structural integrity and chemical stability during the reaction, thereby achieving efficient and continuous HMF oxidation.

[0050] Furthermore, the concentration of pentavalent vanadium ions in the acidic phosphovanadium polyacid mixed solution is controlled at 1-1.4 mol / L.

[0051] The concentration of pentavalent vanadium ions refers to the concentration of V in the solution. 5+ The total amount of vanadium in the form of vanadium is controlled by balancing the solubility and oxidation activity of vanadium species to avoid oversaturation of the solution and precipitation of solids due to excessive concentration.

[0052] Specifically, pentavalent vanadium ions act as active centers for catalytic oxidation reactions, and their concentration directly affects the reaction rate and system stability. When the concentration is lower than 1 mol / L, insufficient active sites lead to slow reaction kinetics; when the concentration exceeds 1.4 mol / L, the solution becomes oversaturated, causing vanadium species to aggregate and form V2O5 precipitation, destroying the homogeneous catalytic system. By limiting the concentration to the range of 1-1.4 mol / L, sufficient V 5+ Participate in the oxidation reaction of HMF and maintain the stable solubility of vanadium species in acidic medium. The concentration range is selected based on the solubility balance of vanadium oxide ions in sulfuric acid solution.

[0053] Through the above technical solution, the present application achieves long-term stable operation of the catalytic oxidation system at room temperature, avoiding catalyst deactivation caused by vanadium species precipitation, while ensuring that the reaction rate meets the requirements of industrial production. This concentration control strategy enables the acidic phosphovanadic acid mixed solution to be used continuously for at least five reaction cycles without the addition of stabilizers, while maintaining a DFF yield above 90%.

[0054] Furthermore, the V 5+ The molar ratio is controlled at 10:0.5-30.

[0055] Specifically, when HMF and V 5+ When the molar ratio of V is 10:0.5-30, 5+ The concentration of V is controlled to be within the critical range that can provide sufficient oxidation capacity without inducing the precipitation of vanadium species. When the ratio is lower than 10:0.5, V 5+ Too low a concentration will lead to a decrease in the oxidation reaction rate; when the ratio is higher than 10:30, excess V 5+This will disrupt the solution equilibrium and form V2O5 precipitation. Within this ratio range, the vanadium-based catalyst can not only catalyze the efficient conversion of HMF into DFF at room temperature, but also maintain solution stability by inhibiting the spontaneous reduction of pentavalent vanadium, providing the necessary conditions for electrolytic regeneration.

[0056] Through the above technical solution, this application solves the problem of V 5+ The precipitation problem caused by the excess maintains the oxidation activity of the catalyst, ensuring the efficient conversion of HMF to DFF at room temperature, and at the same time provides a stable reaction system foundation for the electrolytic regeneration of vanadium-based catalysts.

[0057] Furthermore, the reaction temperature is 25-60° C., and the reaction time is 0.5-4 hours.

[0058] Through the above technical solution, the present invention realizes the rapid completion of the hydroxymethylfurfural oxidation reaction at room temperature while maintaining the chemical stability of the acidic vanadium-phosphoacid mixed solution. The precise control of the reaction time reduces the formation of by-products, making the V 5+ The concentration is kept above the minimum threshold required for the electrolytic regeneration process, providing basic conditions for the recycling of the catalyst.

[0059] The present invention also proposes a process for regeneration of an acidic phosphovanadic polyacid mixed solution and electrolytic coupled hydrogen production. The acidic phosphovanadic polyacid mixed solution (blue) that is produced by catalytic oxidation of 5-hydroxymethylfurfural to 2,5-diformylfuran is transferred into an electrolytic cell equipped with graphite electrodes for regeneration and coupled hydrogen production.

[0060] Furthermore, the regeneration applied current is 0.8-1.2V.

[0061] Through the above technical solution, this application achieves long-term stable operation of the catalyst in an acidic environment at room temperature. The post-reaction solution can be directly regenerated and recycled through electrolysis. This technology avoids the frequent replacement of catalysts due to deactivation in traditional processes, while simplifying the design of the reaction device. The coupled hydrogen production Faraday efficiency is over 96%, providing a feasible foundation for continuous production.

[0062] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The technical terms used herein are only for describing specific embodiments and are not intended to limit the present invention. It should be noted that the reagents used in the present embodiment are all common commercially available products.

[0063] Example 1 Typical Synthesis of Acidic Phosphovanadium Polyacid Mixed Solution System

[0064] 0.27 mol of sodium metavanadate (NaVO3) was dissolved in 75°C H2O. After it was completely dissolved, the temperature was lowered to room temperature and 2.5 mL of 5M H3PO4 was added to obtain reddish-brown PV14. Subsequently, 3.075 mL of this solution was added with 5M H2SO4 to make the H2SO4 concentration 3M. 5+ The concentration is 1.2 M. The resulting solution is used 51 V NMR analysis revealed that the phosphovanadium polyacid H9[PV 14 O 42 ] and its degradation products and VO2 + ions, the results are as follows Figure 1 shown.

[0065] Example 2 Effect of different H2SO4 concentrations on DFF yield

[0066] The sulfuric acid concentration of the acidic phosphovanadium polyacid mixed solution obtained in Example 1 was adjusted to 0.9, 1.2, 1.5, 3, and 4 mol / L, respectively. 2 mmol of 5-hydroxymethylfurfural (HMF) was added to 10 mL of each of these mixed solutions, and the mixture was stirred at 25°C for 4 hours. After the reaction, the reaction product was extracted and separated using dichloromethane (CHCl2). The resulting organic phase was dried, and 0.1 mL of the organic phase solution was placed in a volumetric flask and diluted to 5 mL with methanol. The solution was filtered again through a 0.22 μm polytetrafluoroethylene filter to obtain the test sample.

[0067] The product was quantitatively analyzed by high performance liquid chromatography (HPLC). The chromatographic conditions were as follows: a C18 column (200 mm × 4.6 mm), a mobile phase of methanol-water (volume ratio 30:70), a flow rate of 1.0 mL / min, a column temperature of 40°C, and a detection wavelength of 280 nm. Figure 2 The analysis results showed that the HMF conversion rates were 86%, 87%, 91%, 98%, and 99%, respectively, and the DFF yields were 30%, 63%, 66%, 97%, and 58%, respectively. These results indicate that higher system acidity can improve the selectivity of the DFF product, but excessively high sulfuric acid concentrations can cause side reactions and reduce yields.

[0068] Example 3 Effect of Different H3PO4 Concentrations on DFF Yield in Synthesizing Acidic Phosphovanadic Polyacid Solutions

[0069] 6 mmol sodium metavanadate (NaVO3) was dissolved in 5 mL of 1.2, 0.6, 0.4, 0.3 and 0.24 mol / L H3PO4 solutions respectively. The mixture was stirred under heating until NaVO3 was completely dissolved. H2SO4 was then added to 3 mol / L to obtain a reddish-brown acidic vanadium-phosphoacid mixed solution. 5+The concentration is 1.2 mol / L.

[0070] Add 2 mmol of 5-hydroxymethylfurfural (HMF) to 10 mL of the prepared solution and stir at 25°C for 4 hours. After the reaction, extract the product with dichloromethane (CHCl2). After drying the resulting organic phase, a 0.1 mL volumetric flask was added and diluted to 5 mL with methanol. Filter again through a 0.22 μm polytetrafluoroethylene filter to obtain the sample to be tested.

[0071] The product was quantitatively analyzed by high performance liquid chromatography (HPLC). The chromatographic conditions were as follows: a C18 column (200 mm × 4.6 mm), a mobile phase of methanol-water (volume ratio 30:70), a flow rate of 1.0 mL / min, a column temperature of 40°C, and a detection wavelength of 280 nm. Figure 3 Analysis results showed that HMF conversions were 75%, 80%, 82%, 98%, and 85%, respectively, and DFF yields were 49%, 80%, 85%, 97%, and 72%, respectively. The results indicate that in the presence of strong sulfuric acid, due to the strong binding ability of phosphoric acid with vanadium, excessive phosphoric acid concentrations actually reduced HMF conversion, thereby reducing DFF yield. A molar ratio of V to phosphoric acid of 2-4:1 resulted in higher HMF conversion and DFF yield.

[0072] Example 4 Effect of different reaction temperatures on DFF yield

[0073] Add 2 mmol of 5-hydroxymethylfurfural (HMF) to 10 mL of the solution prepared in Example 1. Stir and react at constant temperatures of 40°C, 60°C, and 80°C for a specified time. After the reaction, extract the reaction product with dichloromethane (CHCl₂). After drying the resulting organic phase, 0.1 mL of the organic phase solution was placed in a volumetric flask and diluted to 5 mL with methanol. Filter again through a 0.22 μm polytetrafluoroethylene filter to obtain the sample to be tested.

[0074] The product was quantitatively analyzed by high performance liquid chromatography (HPLC). The chromatographic conditions were as follows: a C18 column (200 mm × 4.6 mm), a mobile phase of methanol-water (volume ratio 30:70), a flow rate of 1.0 mL / min, a column temperature of 40°C, and a detection wavelength of 280 nm. Figure 4Analysis results show that after 4 hours at 25°C, the HMF conversion rate reached 98%, and the DFF yield was 97%. After 3 hours at 40°C, the HMF conversion rate reached 98%, and the DFF yield was 95%. After 30 minutes at 60°C, the HMF conversion rate reached 99%, and the DFF yield was 96%. Within the 25-60°C range, increasing the reaction temperature can reduce the reaction time.

[0075] Example 5 Regeneration of acidic phosphovanadic polyacid solution and preparation of green hydrogen

[0076] After the acidic vanadium-phosphoacid mixed solution reacts with HMF, V 5+ The ions are reduced and the solution turns blue. The obtained blue solution is pumped into an electrolytic cell equipped with graphite electrodes, and electrolyzed at a constant current of 0.8A. The applied voltage is between 0.8-1.2V. The Faraday efficiency of hydrogen produced by electrolysis is 96%. The electrolysis curve is shown in Figure 5 The color of the acidic phosphovanadic acid mixed solution returns to red and can be recycled to react with HMF again.

[0077] Example 6 Cyclic Catalytic Performance of Acidic Phosphovanadium Polyacid Mixed Solution

[0078] 2 mmol of 5-hydroxymethylfurfural (HMF) was added to 10 mL of the mixed solution prepared in Example 1 and stirred at 60°C for 30 minutes. During the reaction, the reaction solution was observed to turn blue. After the reaction, the reaction product was extracted with dichloromethane (CHCl₂). The resulting organic phase was dried, and 0.1 mL of the organic phase solution was placed in a volumetric flask and diluted to 5 mL with methanol. The solution was filtered again through a 0.22 μm polytetrafluoroethylene filter to obtain the sample to be tested.

[0079] The product was quantitatively analyzed using high-performance liquid chromatography (HPLC) under the following chromatographic conditions: a C18 column (200 mm × 4.6 mm), a mobile phase of methanol-water (volume ratio 30:70), a flow rate of 1.0 mL / min, a column temperature of 40°C, and a detection wavelength of 280 nm. The reaction solution was electrolytically regenerated (as described in Example 5), and 2 mmol of 5-hydroxymethylfurfural (HMF) substrate was added to the reaction. The above reaction process was repeated eight times. The results are shown in Table 5. Figure 6 The analysis results show that the conversion rate of HMF reaches 99% and the yield of DFF exceeds 90%. The results show that the acidic vanadium-phosphoacid mixed solution of the present invention has good cyclic catalytic performance. This is because the vanadium-phosphoacid H9[PV 14 O 42 ]It has high stability and temperature resistance, and no precipitation will occur during the reaction.

[0080] Example 7 Effect of using other strong acids instead of sulfuric acid on DFF yield

[0081] Dissolve 0.27 mol sodium metavanadate (NaVO3) in 75℃ H2O. After it is completely dissolved, cool it to room temperature and add 2.5mL 5M H3PO4 to obtain reddish brown PV14. Add hydrochloric acid, trifluoromethanesulfonic acid, and nitric acid to 3 mol / L to obtain a reddish brown acidic vanadium polyacid mixed solution. 5+ The concentration is 1.2 mol / L. Add 2 mmol of 5-hydroxymethylfurfural (HMF) to 10 mL of the prepared solution and stir at room temperature for a specified time. After the reaction, extract the product with dichloromethane (CHCl2). After drying the resulting organic phase, transfer 0.1 mL of the organic phase solution to a volumetric flask and dilute to 5 mL with methanol. Filter again through a 0.22 μm polytetrafluoroethylene filter to obtain the sample to be tested.

[0082] The product was quantitatively analyzed by high performance liquid chromatography (HPLC). The chromatographic conditions were as follows: a C18 column (200 mm × 4.6 mm), a mobile phase of methanol-water (volume ratio 30:70), a flow rate of 1.0 mL / min, a column temperature of 40°C, and a detection wavelength of 280 nm. Figure 7 The DFF yields were 55%, 88%, and 48%, respectively. The results showed that the strong acidity of the system promoted the formation of DFF. In addition to sulfuric acid, trifluoromethanesulfonic acid can also be used.

[0083] Comparative Example 1 Effect of not adding phosphoric acid on DFF yield

[0084] 0.27 mol of sodium metavanadate (NaVO3) was heated at 70°C and stirred until NaVO3 was completely dissolved. H2SO4 was added to 3 mol / L to obtain a phosphoric acid-free reaction solution. 5+ The concentration is 1.2 mol / L, at which point the solution is mainly VO2 + ions. 2 mmol of 5-hydroxymethylfurfural (HMF) was added to 10 mL of the prepared solution and stirred at room temperature for 4 hours. During the reaction, a white needle-shaped solid was observed to gradually precipitate. After the reaction, the reaction product was extracted and separated using dichloromethane (CHCl2). The resulting organic phase was dried, and 0.1 mL of the organic phase solution was placed in a volumetric flask and diluted to 5 mL with methanol. The solution was then filtered through a 0.22 μm polytetrafluoroethylene filter to obtain the sample to be tested.

[0085] The product was quantitatively analyzed using high-performance liquid chromatography (HPLC) under the following conditions: a C18 column (200 mm × 4.6 mm), a mobile phase of methanol-water (volume ratio 30:70), a flow rate of 1.0 mL / min, a column temperature of 40°C, and a detection wavelength of 280 nm. The DFF yield was 78%. The catalyst solution was reused for the second HMF oxidation, and the DFF yield decreased to 44%. After five cycles, the DFF yield decreased to 22%. Figure 8 The results show that if phosphoric acid is not added to the catalytic reaction solution, the phosphovanadate polyacid H9[PV 14 O 42 ] cannot be generated, the yield of DFF is reduced, and the catalyst solution is unstable, resulting in a significant decrease in the cycle yield.

[0086] Comparative Example 2 Effect of Simple Vanadyl Sulfate Catalyst on DFF Yield

[0087] 15.47 g of vanadium pentoxide (V2O5) was added to 38.5 g of 98% concentrated sulfuric acid (H2SO4) and heated under reflux at 140°C until the V2O5 was completely dissolved, yielding a reddish-brown vanadyl sulfate solution. After cooling to room temperature, the reaction system was filtered through a 0.45 μm polytetrafluoroethylene filter. Deionized water was then added to adjust the H2SO4 concentration to 3 mol / L, yielding a (VO2)2SO4 solution. 0.1 g of 5-hydroxymethylfurfural (HMF) was added to 10 mL of the (VO2)2SO4 solution, and the reaction was stirred at 25°C for 4 hours. White needle-like solids were observed to precipitate during the reaction. After completion of the reaction, the reaction product was extracted with dichloromethane (CHCl2), and the resulting organic phase was dried to yield the product.

[0088] The product was quantitatively analyzed using high-performance liquid chromatography (HPLC) under the following conditions: a C18 column (200 mm × 4.6 mm), a mobile phase of methanol-water (volume ratio 30:70), a flow rate of 1.0 mL / min, a column temperature of 40°C, and a detection wavelength of 280 nm. The DFF yield was 88%. The (VO2)2SO4 solution was regenerated and reused for the oxidation of HMF a second time, resulting in a DFF yield of 75%. After five cycles, the DFF yield decreased to 48%. Figure 9 The results show that although the simple (VO2)2SO4 solution generated by dissolving V2O5 in sulfuric acid can achieve a high DFF yield in the first reaction, the simple pentavalent vanadium ion catalyst solution is unstable at the reaction temperature, resulting in a significant reduction in the cycle yield.

[0089] Comparative Example 3 Effect of not adding sulfuric acid on DFF yield

[0090] 0.27 mol sodium metavanadate (NaVO3) was heated and stirred at 70℃ until NaVO3 was completely dissolved. After cooling to room temperature, H3PO4 was added to obtain a reddish-brown vanadium-phosphophosphate solution, so that the concentrations of phosphoric acid in the solution were 1.2, 1.5, and 3 mol / L, respectively. 5+ The concentration is 1.2 mol / L. 2 mmol 5-hydroxymethylfurfural (HMF) was added to 10 ml of the above solution and stirred at 60 o The reaction was stirred at 4°C for 40 minutes. After the reaction, the reaction product was extracted and separated using dichloromethane (CHCl2). The resulting organic phase was dried, and 0.1 mL of the organic phase solution was placed in a volumetric flask and diluted to 5 mL with methanol. The solution was filtered again through a 0.22 μm polytetrafluoroethylene filter to obtain the sample to be tested.

[0091] The products were quantitatively analyzed using high-performance liquid chromatography (HPLC) under the following conditions: a C18 column (200 mm × 4.6 mm), a mobile phase of methanol-water (volume ratio 30:70), a flow rate of 1.0 mL / min, a column temperature of 40°C, and a detection wavelength of 280 nm. The results showed that the DFF yields were 3%, 6%, and 40%, respectively. Figure 10 As shown in the experimental results, more phosphoric acid must be added to keep the system strong acidity in order to obtain a better DFF yield. Therefore, the addition of strong acid, such as sulfuric acid, plays an important role in improving the yield of DFF. The acidity of the system promotes the decomposition of vanadium phosphate into VO2 + ions to obtain a higher DFF yield.

[0092] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for producing DFF by catalytic oxidation of HMF using an acidic vanadium-phosphorus acid mixed system, characterized in that: HMF is added to an acidic phosphovanadic polyacid mixed solution to react at room temperature to generate DFF; wherein the preparation method of the acidic phosphovanadic polyacid mixed solution comprises the following steps: A vanadium-based compound and phosphoric acid form a phosphovanadium polyacid, and then a strong acid is added to obtain a reddish-brown acidic phosphovanadium polyacid mixed solution; the vanadium-based compound is any one of vanadium pentoxide and a vanadate, and the vanadate is any one or more of sodium metavanadate, sodium orthovanadate, sodium pyrovanadate, ammonium metavanadate, ammonium orthovanadate, ammonium pyrovanadate, potassium metavanadate, potassium orthovanadate, or potassium pyrovanadate; the strong acid is sulfuric acid or trifluoromethanesulfonic acid; the concentration of sulfuric acid in the acidic phosphovanadium polyacid solution is 0.9-4 mol / L; the concentration of phosphoric acid is 0.3-0.6 mol / L; and the molar ratio of phosphoric acid to V in the vanadium-based compound is 1:2-4.

2. The method according to claim 1, characterized in that The strong acid is sulfuric acid.

3. The method according to claim 1, wherein The acidic vanadium-phosphoacid mixed solution contains V 5+ The concentration is 1-1.4 mol / L.

4. The method according to claim 1, wherein The HMF and the acidic vanadium phosphoacid mixed solution V 5 + The molar ratio is 10:0.5-30.

5. The method according to claim 1, wherein The reaction temperature is 25-60° C., and the reaction time is 0.5-4 h.

6. An electrolysis coupled hydrogen production process, characterized in that: First, the method for catalytic oxidation of HMF to produce DFF based on the acidic phosphovanadic polyacid mixed system according to any one of claims 1 to 5 is used to catalytically oxidize HMF to produce DFF, and the acidic phosphovanadic polyacid mixed solution obtained after catalytic oxidation of HMF to produce DFF is transferred to an electrolytic cell equipped with graphite electrodes for regeneration and coupled hydrogen production.

7. The electrolysis coupled hydrogen production process according to claim 6, characterized in that: The regeneration applied voltage was 0.8-1.2V.

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