Method for generating 2, 5-diformylfuran through catalytic oxidation of 5-hydroxymethylfurfural based on acidic vanadyl sulfate solution system

Abstract

The invention discloses a method for generating 2, 5-diformyl furan through catalytic oxidation of 5-hydroxymethylfurfural based on an acidic vanadyl sulfate solution system, and belongs to the technical field of biomass conversion. The method comprises the following steps: by taking an acidic vanadyl sulfate solution as a catalyst and / or an oxidizing agent and HMF as a raw material, reacting to generate DFF; wherein the concentration of H2SO4 in the acidic vanadyl sulfate solution is 2.5 mol / L to 4.5 mol / L. According to the method disclosed by the invention, the oxidation process of 5-hydroxymethylfurfural (HMF) is innovatively and successfully expanded to an acid environment. HMF can be converted into DFF with high selectivity, the conversion rate reaches 100%, and the yield of DFF exceeds 80%.

Description

Technical Field

[0001] The invention belongs to the technical field of biomass conversion, and more specifically, relates to a method for generating 2,5-diformylfuran by catalytic oxidation of 5-hydroxymethylfurfural based on an acidic vanadyl sulfate solution system. Background Art

[0002] 5-Hydroxymethylfurfural (HMF), as a key biomass-derived platform molecule, contains abundant functional groups such as aldehyde, hydroxyl and furan ring in its structure, which can be converted into high value-added chemicals such as 2,5-diformylfuran (DFF) and 2,5-furandicarboxylic acid (FDCA) through various 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. However, the highly selective preparation of DFF from HMF still faces major challenges, because the reaction requires selective oxidation of methyl hydroxyl groups while keeping the aldehyde group intact. Therefore, the research on obtaining DFF with high yield and high selectivity remains challenging. To this end, various catalytic methods using homogeneous and heterogeneous catalysts and assisted by greener molecular oxygen for oxidation have been widely studied.

[0003] Due to their diverse valence characteristics, vanadium compounds have shown significant advantages in the catalytic oxidation reaction of organic compounds, especially in the selective oxidation of alcohols. Based on this characteristic, Chinese patent CN103739573A discloses a V2O5 / H-beta catalyst loaded on a zeolite molecular sieve. In a dimethyl sulfoxide (DMSO) solution, HMF125°C and 10 bar O2 react for 3 hours, and the DFF selectivity is as high as 99%. However, the shedding of vanadium species in this catalytic system leads to a decrease in catalyst activity, thereby limiting its cyclic stability. To solve this problem, researchers proposed a homogeneous catalytic system that avoids the defect of active material shedding. The system uses Cu(NO3)2 / VOSO4 as a catalyst, reacts for 1.5 hours at 353K, 0.1 MPa O2 and acetonitrile (CH3CN) solution, and achieves excellent performance of 99% HMF conversion and DFF selectivity. However, it is still necessary to control the pressure and use organic solvents, which has high requirements for equipment and is not conducive to industrialization. Chinese patent CN101987839A discloses a composite catalytic system using vanadyl sulfate (VOSO4) and an auxiliary agent to convert HMF into DFF, but the system requires control of pressure and oxygen content, making it difficult to industrialize. CN118894822A reports a method for converting HMF into DFF using vanadyl sulfate (VOSO4) as an oxidant and sulfuric acid as an auxiliary agent, but the method has a low conversion rate for high-concentration HMF, and the amount of vanadyl sulfate used is high, the reaction temperature is 40-80°C, and the cost is high.

[0004] The research on the oxidation of HMF to DFF by vanadyl sulfate under acidic conditions is relatively limited, which limits the application potential of vanadium-based catalysts under a wider range of reaction conditions. At present, there is no report on the use of (VO2)2SO4 as a catalyst and oxidant to promote the formation of DFF from HMF. Summary of the invention

[0005] The present invention aims at the defects of low conversion rate, low selectivity and difficult industrialization of reaction conditions in the process of converting 5-hydroxymethylfurfural (HMF) into 2,5-diformylfuran (DFF) in the prior art, and proposes a method for catalytic oxidation of 5-hydroxymethylfurfural to generate 2,5-diformylfuran based on an acidic vanadyl sulfate ((VO2)2SO4) solution system. Using an acidic vanadyl sulfate solution as a catalyst, HMF can be completely converted, and DFF has high selectivity and high yield.

[0006] The technical solution of the present invention to solve the above technical problems is as follows: A method for catalytically oxidizing 5-hydroxymethylfurfural to produce 2,5-diformylfuran based on an acidic vanadyl sulfate ((VO2)2SO4) solution system, comprising: using an acidic vanadyl sulfate (V) (VO2)2SO4 solution as a catalyst and / or an oxidant, and HMF as a raw material, to react and produce DFF; wherein the concentration of H2SO4 in the acidic vanadyl sulfate solution is 2.5-4.5 mol / L.

[0007] Preferably, the acidic vanadyl sulfate solution contains V 5+ The concentration is 0.4-1 mol / L.

[0008] Preferably, the reaction time is 1 to 12 h.

[0009] Preferably, the reaction temperature is -5°C to 60°C.

[0010] Preferably, the reaction temperature is 25-40°C.

[0011] Preferably, the volume ratio of dichloromethane to the reaction product is 1:1.

[0012] Preferably, the preparation method of the acidic vanadium oxysulfate solution is: adding vanadium pentoxide (V2O5) to concentrated sulfuric acid with a mass fraction of 98%, heating and reflux at 130-150°C until V2O5 is completely dissolved to obtain a reddish-brown vanadium oxysulfate solution, cooling to room temperature, filtering to remove impurities, adding deionized water to adjust the H2SO4 concentration to 2.5-4.5 mol / L, and obtaining an acidic vanadium oxysulfate solution.

[0013] Preferably, the method further comprises: extracting and separating the reaction product using dichloromethane (CHCl2), and drying the obtained organic phase to obtain DFF.

[0014] The solubility of HMF and DFF in dichloromethane is higher than that in water, and dichloromethane can separate DFF and HMF from other substances in the product.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The acidic vanadyl sulfate solution used in the present invention exhibits excellent strong oxidation properties. Under acidic conditions, the VO2 + The cations become highly active catalytic sites, significantly increasing the oxidation reaction rate. Compared with traditional technologies, the present invention innovatively successfully extends the oxidation process of 5-hydroxymethylfurfural (HMF) to an acidic environment. This breakthrough overturns the traditional alkaline reaction system, solves the technical bottleneck of poor selective oxidation of HMF under acidic conditions, and provides a more efficient and economical process route for HMF oxidation.

[0016] The method provided by the invention has low requirements on equipment, mild reaction conditions and is easy to industrialize. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 In the present invention, different V 5+ The effect of the concentration of (VO2)2SO4 solution on the DFF yield; Among them, (a) represents different V 5+ HMF conversion rate and DFF yield at different concentrations, (b) represents different V 5+ HPLC chromatogram of the product at concentrations.

[0018] Figure 2 Effect of (VO2)2SO4 solution with different H2SO4 concentrations on DFF yield in Example 2 of the present invention; Among them, (a) represents the HMF conversion rate and DFF yield under different H2SO4 concentrations, and (b) represents the HPLC spectrum of the products under different H2SO4 concentrations.

[0019] Figure 3 Effect of (VO2)2SO4 solution with different reaction times on DFF yield in Example 3 of the present invention; Wherein, (a) represents the HMF conversion rate and DFF yield at different reaction times, and (b) represents the HPLC spectra of the products at different reaction times.

[0020] Figure 4 Effect of (VO2)2SO4 solution at different reaction temperatures on DFF yield in Example 4 of the present invention; Wherein, (a) represents the HMF conversion rate and DFF yield at different reaction temperatures, and (b) represents the HPLC spectra of the products at different reaction temperatures.

[0021] Figure 5 Photos of the (VO2)2SO4 solution prepared in the present invention (right) and a commercial vanadyl sulfate (left, VOSO4) aqueous solution. DETAILED DESCRIPTION

[0022] Many specific details are set forth in the following description to facilitate a full 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 can make similar improvements without violating the connotation of the present invention, so the present invention is not limited to the specific implementation disclosed below.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of 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 commercial products.

[0024] Example 1 Different V 5+ Effect of concentration on DFF yield Add 15.47 g of vanadium pentoxide (V2O5) to 38.5 g of 98% concentrated sulfuric acid (H2SO4) and heat under reflux at 140°C until V2O5 is completely dissolved to obtain a reddish brown vanadium sulfate solution. Figure 5 As shown, the vanadyl sulfate solution in this application is reddish brown, V 5+ The concentration is yellow in acidic aqueous solution and reddish brown in concentrated acidic aqueous solution, while commercial vanadyl sulfate (VOSO4) is blue, showing V 4+ . This indicates that (VO2)2SO4 was successfully synthesized in this application.

[0025] After the reaction system was cooled to room temperature, it was filtered through a 0.45 μm polytetrafluoroethylene filter membrane, and then deionized water was added to adjust the H2SO4 concentration to 3 mol / L to obtain a (VO2)2SO4 solution. The prepared (VO2)2SO4 solution was diluted with 3 mol / L H2SO4 to obtain V 5+ The concentrations of (VO2)2SO4 solutions are 0.2, 0.4, 0.6, 0.8, and 1.0 mol / L respectively.

[0026] 0.1 g 5-hydroxymethylfurfural (HMF) was added into 5 mL of different V 5+ The reaction was stirred at a constant temperature of 25°C for 4 hours in a (VO2)2SO4 solution with a concentration of 1.5 wt %. During the reaction, a white needle-like solid was observed to gradually precipitate. After the reaction, the reaction product (volume ratio of 1:1) was extracted and separated using dichloromethane (CHCl2) (twice, the organic phases were combined), and the obtained organic phase was dried to obtain the product.

[0027] 5 mg of the product was dissolved in 5 mL of methanol and filtered through a 0.45 μm polytetrafluoroethylene filter membrane to obtain the sample to be tested. The sample to be tested was analyzed by high performance liquid chromatography (HPLC). The chromatographic conditions were as follows: the chromatographic column was a C18 column (200 mm×4.6 mm), the mobile phase was methanol-water (volume ratio 30:70), the flow rate was 1.0 mL / min, the column temperature was 40°C, and the detection wavelength was 265 nm. The analysis results showed that different V 5+Concentration of (VO2)2SO4 solution as catalyst, such as Figure 1 As shown in (b), there is no HMF peak in the HPLC spectrum, only DFF peak, indicating that the conversion rate of HMF can reach 100%. Figure 1 As shown in (a), the calculated DFF yields (yield = molar mass of product / molar mass of theoretical product*100%, the same below) are 55%, 75%, 82%, 83%, and 79%, respectively. It can be seen that the acidic (VO2)2SO4 solution is used as a catalyst, among which V 5+ The optimal concentration range is 0.4-1.0 mol / L, which may be due to different V 5+ The concentration changes the selectivity of the catalyst for DFF. Too low or too high a concentration will lead to side reactions, and the products of the side reactions cannot be extracted by dichloromethane.

[0028] Example 2 Effect of different H2SO4 concentrations on DFF yield First, 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 V2O5 was completely dissolved to obtain a reddish-brown vanadium sulfate solution. After the reaction system was cooled to room temperature, it was filtered through a 0.45 μm polytetrafluoroethylene filter membrane, and then deionized water was added to adjust the H2SO4 concentration to 2.2 mol / L, 2.5 mol / L, 4.5 mol / L, and 5 mol / L, respectively, to obtain V 5+ (VO2)2SO4 solution with a concentration of 0.8 mol / L.

[0029] 0.25 g of 5-hydroxymethylfurfural (HMF) was added to 5 mL of the above (VO2)2SO4 solution with different H2SO4 concentrations, and stirred at 25°C for 4 hours. During the reaction, a white needle-like solid was observed to gradually precipitate. After the reaction, the reaction products were extracted and separated using dichloromethane (CHCl2), and the obtained organic phase was dried to obtain the product.

[0030] Take 5 mg of the product and dissolve it in 5 mL of methanol, and filter it again through a 0.45 μm polytetrafluoroethylene filter membrane to obtain the sample to be tested. The sample to be tested was analyzed by high performance liquid chromatography (HPLC). The chromatographic conditions were as follows: the chromatographic column was a C18 column (200 mm × 4.6 mm), the mobile phase was methanol-water (volume ratio 30:70), the flow rate was 1.0 mL / min, the column temperature was 40 ° C, and the detection wavelength was 265 nm. Figure 2 As shown in (b), there is no HMF peak in the HPLC spectrum, and the conversion rate of HMF reaches 100%. Figure 2As shown in (a), the yields of DFF are 58%, 78%, 83%, 75% and 67%, respectively, and the optimal H2SO4 concentration is 2.5-4.5 mol / L. This may be because low concentration of H2SO4 will reduce the oxidizability of (VO2)2SO4 solution, which will increase the occurrence of side reactions and lead to a lower DFF yield; while too high H2SO4 concentration affects the stability of DFF, thereby reducing the yield. Example 3 Effect of different reaction times on DFF yield

[0031] First, 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 V2O5 was completely dissolved to obtain a reddish-brown vanadium sulfate solution. After the reaction system was cooled to room temperature, it was filtered through a 0.45 μm polytetrafluoroethylene filter membrane, and then deionized water was added to adjust the H2SO4 concentration to 3 mol / L to obtain a (VO2)2SO4 solution. Finally, the prepared (VO2)2SO4 solution was diluted with 3 mol / L H2SO4 to obtain V 5+ (VO2)2SO4 solution with a concentration of 0.8 mol / L.

[0032] 0.25 g of 5-hydroxymethylfurfural (HMF) was added to 5 mL of the above (VO2)2SO4 solution, and the mixture was stirred at a constant temperature of 25°C for 1 h, 2 h, 4 h, 6 h, and 12 h. During the reaction, a white needle-like solid was observed to gradually precipitate. After the reaction, the reaction product was extracted and separated using dichloromethane (CHCl2), and the obtained organic phase was dried to obtain the product.

[0033] Take 5 mg of the product and dissolve it in 5 mL of methanol, and filter it again through a 0.45 μm polytetrafluoroethylene filter membrane to obtain the sample to be tested. High performance liquid chromatography (HPLC) was used for quantitative analysis of the sample to be tested. The chromatographic conditions were as follows: the chromatographic column was a C18 column (200 mm × 4.6 mm), the mobile phase was methanol-water (volume ratio 30:70), the flow rate was 1.0 mL / min, the column temperature was 40 ° C, and the detection wavelength was 265 nm. Figure 3 As shown in (b), there is only DFF peak in the product, indicating that the conversion rate of HMF reaches 100%. Figure 3 As shown in (a), the yields of DFF are 73%, 79%, 85%, 83%, and 74%, respectively. It can be seen that the reaction time has little effect on the yield of DFF, and too long a reaction time may cause the decomposition of DFF, thus affecting the yield. Example 4 Effect of different reaction temperatures on DFF yield

[0034] First, 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 V2O5 was completely dissolved to obtain a reddish-brown vanadium sulfate solution. After the reaction system was cooled to room temperature, it was filtered through a 0.45 μm polytetrafluoroethylene filter membrane, and then deionized water was added to adjust the H2SO4 concentration to 3 mol / L to obtain a (VO2)2SO4 solution. Finally, the prepared (VO2)2SO4 solution was diluted with 3 mol / L H2SO4 to obtain V 5+ (VO2)2SO4 solution with a concentration of 0.8 mol / L.

[0035] 0.25 g of 5-hydroxymethylfurfural (HMF) was added to 5 mL of the above (VO2)2SO4 solution, and the mixture was stirred for 4 hours in an ice-water bath (~0°C), 25°C, 40°C, and 60°C. During the reaction, a white needle-like solid was observed to gradually precipitate. After the reaction, the reaction product was extracted and separated using dichloromethane (CHCl2), and the obtained organic phase was dried to obtain the product.

[0036] Take 5 mg of the product and dissolve it in 5 mL of methanol, and filter it again through a 0.45 μm polytetrafluoroethylene filter membrane to obtain the sample to be tested. The sample to be tested was analyzed by high performance liquid chromatography (HPLC). The chromatographic conditions were as follows: the chromatographic column was a C18 column (200 mm × 4.6 mm), the mobile phase was methanol-water (volume ratio 30:70), the flow rate was 1.0 mL / min, the column temperature was 40 ° C, and the detection wavelength was 265 nm. Figure 4 As shown in (b), there is only the DFF peak, indicating that the conversion rate of HMF reaches 100%. Figure 4 As shown in (a), the calculated yields of DFF are 78%, 85%, 84% and 82% respectively, indicating that the reaction temperature has little effect on the yield and selectivity of HMF converted to DFF catalyzed by (VO2)2SO4 solution, that is, the method of the present application is applicable in a wide temperature range.

[0037] 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 principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for catalytically oxidizing 5-hydroxymethylfurfural to produce 2,5-diformylfuran based on an acidic vanadyl sulfate solution system, characterized in that: The method comprises: using an acidic vanadium sulfate (VO2)2SO4 solution as a catalyst and / or an oxidant and HMF as a raw material to react and generate DFF; wherein the concentration of H2SO4 in the acidic vanadium sulfate solution is 2.5-4.5 mol / L; and the concentration of V in the acidic vanadium sulfate solution is 1.5-2.0 mol / L. 5+ The concentration is 0.4-1 mol / L.

2. The method according to claim 1, characterized in that The reaction time is 1 to 12 h.

3. The method according to claim 1, characterized in that The reaction temperature is -5°C to 60°C.

4. The method according to claim 3, characterized in that The reaction temperature is 25-40°C.

5. The method according to claim 1, characterized in that The preparation method of the acidic vanadyl sulfate solution is as follows: adding V2O5 to concentrated sulfuric acid with a mass fraction of 98%, heating and reflux at 130-150° C. until the V2O5 is completely dissolved to obtain a reddish-brown vanadyl sulfate solution, cooling to room temperature, filtering to remove impurities, adding deionized water to adjust the H2SO4 concentration to 2.5-4.5 mol / L, and obtaining the acidic vanadyl sulfate solution.

6. The method according to claim 1, characterized in that The method further comprises: extracting and separating the reaction product using dichloromethane, and drying the obtained organic phase to obtain DFF.

7. The method according to claim 6, characterized in that The volume ratio of the dichloromethane to the reaction product is 1:1.

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