CN103819432A - Catalyzed Preparation of 2,5-Diformylfuran by Molecular Oxygen Assisted Active MnO2 - Google Patents

Abstract

The invention discloses a method for preparing 2,5-diformyl furan through catalysis of molecular oxygen auxiliary activity MnO2, and relates to 2,5-diformyl furan. An important platform compound 5-hydroxymethyl furfural derived from a biomass carbohydrate is used as an oligomer, molecular oxygen as a clean oxidizing agent and an organic solvent as a solvent system, and under the action of the MnO2, HMF (Hydroxymethyl Furfural) is subjected to oxidation reaction so as to generate 2,5-diformyl furan. The used catalyst is simple in synthesis route, the used raw materials are cheap and easy to obtain, the reaction condition is gentle, the oxidation process is easy to control, the efficiency is high, a small amount of byproducts are generated after the reaction, the DFF (Dispersion Flattened Fiber) selectivity of a product is good, and the oxygen is used as a clean oxygen source, so that properties of both economy and environment-friendliness are achieved; the catalyst and a reaction liquid are easily separated; the catalyst is good in reuse property and economic and environment-friendly; certain guidance significance is achieved for industrial application of 2,5-diformyl furan produced by using a clean catalytic oxidation method.

Description

Catalyzed Preparation of 2,5-Diformylfuran by Molecular Oxygen Assisted Active MnO2

technical field

The invention relates to 2,5-diformyl furan, in particular to a method for catalytically preparing 2,5-diformyl furan with molecular oxygen assisted active _MnO2 .

Background technique

With the depletion of fossil resources and the continuous deterioration of the human living environment, it is imminent to seek fuels and basic chemicals that can replace fossil energy. Biomass is the only renewable energy source that can replace fossil energy sources to produce chemicals. The production of chemicals, fuels and their derivatives from resource-rich and renewable biomass can provide a feasible route to alleviate the world's strong dependence on fossil energy that is gradually depleting ^[1-3] . 5-hydroxymethylfurfural (5-hydroxymethylfurfural, HMF) prepared from biomass carbohydrates is known as a bridge connecting petrochemical and biomass chemical industries because it can further form many basic chemicals and energy molecules through different catalytic reactions ^{[ 3-11]} . As one of the important derivative products of HMF, 2,5-diformylfuran (2,5-diformylfuran, DFF) is a high value-added biomass-based chemical with broad application prospects in the future. DFF exists in the form of solid powder at room temperature, with a crystal appearance, and its molecular formula is C ₆ H ₄ O ₃ . DFF has a variety of uses ^[12-16] , such as the synthesis of polymeric Schiff bases, high-end drugs, macrocyclic ligands and antifungal agents, etc. In addition, it can also be used as a monomer for various new polymer materials such as Synthesis of 2,5-diformylfuran-urea resin, etc. However, at present, the price of DFF products in the industry is high and the quantity is low, and its preparation technology is immature, and it is still in the process of continuous exploration and improvement.

Since the HMF molecule contains furan ring, hydroxymethyl group and formyl group, the oxidation reaction of HMF is often accompanied by many side reactions. The reaction of generating DFF from HMF is mainly to selectively oxidize the hydroxymethyl group in the HMF molecule without attacking the more active unsaturated formyl group, otherwise other oxidation products will be formed ^[17,18] , such as 5-hydroxymethyl Base-2-furoic acid (5-hydroxymethyl-2-furancarboxylic acid, HMFCA), 5-formyl-2-furoic acid (5-formyl-2-furancarboxylic acid, FFCA), 2,5-furandicarboxylic acid (2, 5-furandicarboxylic acid, FDCA), etc. Therefore, the study of obtaining DFF with high yield and high selectivity is still challenging. For this reason, various catalytic methods using homogeneous and heterogeneous catalysts and supplemented with greener molecular oxygen for oxidation have been extensively studied ^[19-26] .

Traditionally, DFF is prepared by oxidizing HMF with stoichiometric reagents such as NaClO and BaMnO ₄ , which causes serious pollution. Yadav et al mentioned a manganese oxide supported Ag catalyst in patent WO2012/073251A1. Molecular oxygen is the oxygen source and isopropanol is the solvent. Under certain conditions, a higher yield of DFF has been obtained, but the method needs to be designed higher. Precious metal Ag loading, up to 50% (based on mass), high cost. As far as vanadium-based catalysts are concerned, Carlini et al. used vanadyl-phosphate as the catalyst. At 150 °C, the HMF conversion rate was 84%, and the DFF selectivity was 97%. Corma et al. used immobilized vanadyl-pyrimidine complexes as catalysts. At 130 °C, the HMF conversion rate was 82%, and the DFF selectivity was 99%. Jiping Ma et al. adopted a homogeneous Cu(NO ₃ ) ₂ /VOSO ₄ catalytic system with molecular oxygen as the oxygen source. At 80°C, the HMF conversion rate and DFF selectivity both reached 99%. When Cu(NO ₃ ) ₂ /VOCl ₃ is used as the catalytic system, the HMF conversion rate and DFF selectivity can reach 85% and 97% respectively under certain conditions. The reaction conditions are mild and the yield of DFF is high, but the catalyst is not easy to recover and reuse. Moreau et al. used V ₂ O ₅ /TiO ₂ as a catalyst, toluene as a solvent, a temperature of 90°C, and an air pressure of 1.6 MPa, and the DFF yield was as high as ₉₀ %. O ₅ is also an extremely toxic reagent. Navarro et al. used vanadium oxy-acetylacetonate/PVP as a catalyst, benzotrifluoride as a solvent, and under the conditions of temperature 130 °C and pressure 1 MPa, molecular oxygen was the oxygen source, and the DFF yield was 77%. The preparation of the catalyst was cumbersome and the yield was low. high. It can be seen from the above that molecular oxygen assisted catalytic conversion of HMF to DFF has become a mainstream method, and has advantages in some aspects. For this series of reactions, there are more studies on vanadium-based catalysts and supported noble metal catalysts. Studies have shown that the former has better catalyst activity, but these catalysts are mostly extremely toxic reagents, which do not conform to the concept of green chemistry development. In addition, there are often issues such as low conversion numbers. The high cost of noble metal catalysts does not meet the requirements of large-scale industrial production of DFF in the future. Therefore, it is still of great significance to continue to search for and develop more efficient and economical catalytic systems, especially catalysts that can be applied under mild reaction conditions.

Active MnO ₂ is mostly made from high-grade natural MnO ₂ through reduction, disproportionation, heavy-duty and other processes. It is actually a combination of activated MnO ₂ and chemical MnO ₂ . It has the advantages of γ-type crystal structure, large specific surface area, and good liquid absorption performance. This product has good electrochemical activity and is originally a material widely used in battery manufacturing. It can partially or completely replace traditional electrolytic MnO ₂ , and has a good cost performance. In addition to the application of active MnO ₂ in battery manufacturing, it is also widely used in the oxidation of alcohols with α, β-unsaturated groups for selective oxidation ^[27] . Among the MnO ₂ prepared by different methods, the brown MnO ₂ is very lively and has good reactivity. When it is used to oxidize unsaturated alcohols, the oxidation conditions are mild, and it has no effect on the unsaturated bonds in the reactants, and will not cause isomerization of unsaturated groups ^[28] . For example, active MnO ₂ can selectively oxidize perillyl alcohol to synthesize perillaldehyde with a conversion rate as high as 99% ^[29] ; it can also convert other unsaturated alcohols, including dilute phenyl alcohol, alkyne phenyl alcohol, benzyl alcohol, Alcohol, etc. ^[30] , if benzyl alcohol can be converted well, the conversion rate can reach 93%, and the selectivity of the product benzaldehyde is almost 100%. In addition, active MnO ₂ can also oxidize phenol and its derivatives, aniline and its aromatic amines ^[31-40] , etc. However, the most widely used active MnO ₂ is the selective oxidation of unsaturated alcohols to generate corresponding unsaturated aldehydes or ketones ^[30] , and it is difficult to undergo further oxidation reactions, showing excellent selectivity. The reason for this is that manganese is a multivalent metal with a valence distribution of +2 to +7. Manganese in nature mainly exists in the form of +2, +3 or +4 valence. The active MnO ₂ prepared by different methods is different in its structure (its chemical formula can be written as MnO _2-x ·nH ₂ O, where x is between 0 and 0.5, and n can be greater than 0), and its oxidation activity will also exist difference. Because the manganese in the active MnO ₂ is in the intermediate valence state, it has dual properties of oxidation and reduction, and its oxidation is mild, showing excellent selectivity in many organic reactions. Inspired by this, the present invention will learn from the existing method for preparing MnO ₂ ^[41] , synthesize active MnO ₂ and apply it in the selective oxidation reaction of HMF to DFF.

references

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Contents of the invention

The object of the present invention is to provide a method for the catalytic preparation of 2,5-diformyl furan by molecular oxygen assisting active _MnO2 .

Concrete steps of the present invention are as follows:

Using 5-hydroxymethylfurfural (HMF), an important platform compound derived from biomass carbohydrates, as the reaction substrate, molecular oxygen as a clean oxidant, and an organic solvent as a solvent system, the oxidation reaction of HMF occurs under the catalysis of active _MnO2 This produces 2,5-diformylfuran.

The mass percentage of the HMF and the organic solvent may be 1%-5%; the amount of the active MnO ₂ may be 10%-200% of the HMF in mass percentage, preferably 40%-100%.

The organic solvent can be selected from aromatic reagents such as toluene and tetrahydrofuran, acetone, acetonitrile, carbon tetrachloride, dichloromethane, cyclohexane, N,N-dimethylformamide, N,N-dimethylethane One of amides, dimethyl sulfoxide, methyl isobutyl ketone, N-methylpyrrolidone, esters, etc., preferably N,N-dimethylformamide.

The molecular oxygen can be air or oxygen, preferably oxygen.

The oxygen pressure in the oxidation reaction process can be 1-16bar, preferably the oxygen pressure is 5-10bar; the temperature of the oxidation reaction can be 50-130°C, preferably 100-120°C, and the best is 110°C; the oxidation reaction The time can be 0.5 ~ 48h, preferably 2 ~ 20h.

Described active _MnO Non-industrial electrolytic _MnO Or common commercially available chemical MnO _Reagent ; Described active _MnO The preparation method is as follows:

(1) Add distilled water into KMnO ₄ , stir and dissolve to make KMnO ₄ solution;

(2) Add Mn ²⁺ salt to distilled water to make solution A;

(3) Transfer the KMnO ₄ solution into a Hastelloy reactor (GCF-0.4L), then add solution A, then add distilled water to constant volume, seal the reactor, heat up and react, cool to room temperature, and perform suction filtration after sampling , The filtered material is washed, and the filtered sample is dried and ground to obtain active MnO ₂ black powder below 6mm.

In step (2), the Mn ²⁺ salt can be manganese sulfate; the amount of the Mn ²⁺ salt can be 1.5 times that of KMnO ₄ by mass ratio;

In step (3), the amount of distilled water can be added according to the filling rate of 80% of the Hastelloy reactor volume; the temperature of the heating reaction can be 150°C, and the time of the heating reaction can be 8h; the washing can be done with distilled water 5-10 times; the drying condition may be to place the filtered sample in a blast drying oven at 110°C±5°C for 3-4h.

In the present invention, the active _MnO2 catalyst is used in the reaction of molecular oxygen-assisted selective catalytic oxidation of HMF to generate DFF, and the specific steps are as follows: the catalyst, HMF and an organic solvent are weighed and quantitatively added to a beaker and other containers to mix evenly, and then added to In the high-pressure reaction kettle, the reaction kettle is closed, and a certain pressure of oxygen is introduced. When the oxygen is passed, the gas can be used to exhaust the reaction kettle for about 5 times, and then the gas cylinder is closed after being filled with a certain pressure of oxygen. The reaction system is heated up to a predetermined temperature under stirring, and after a certain period of reaction, the reaction kettle is quickly cooled to room temperature, and samples are taken and centrifuged to separate the catalyst for sample detection. The separated catalyst was washed with acetone and dried in an oven at 65 °C for subsequent reuse.

The invention provides a preparation method for selectively catalytically oxidizing 5-hydroxymethylfurfural (HMF) to generate 2,5-diformylfuran based on molecular oxygen assisted active _MnO2 . This method can oxidize HMF to generate 2,5-diformylfuran (DFF) under relatively mild reaction conditions, using molecular oxygen as an oxidant, under the action of an active MnO ₂ catalyst. The synthesis route of the catalyst used in the present invention is simple; the raw materials used are cheap and easy to obtain; the reaction conditions are mild, the oxidation process is easy to control, and the efficiency is high; The catalyst and the reaction solution are easy to separate, the catalyst has good reusability, and it is economical and environmentally friendly. The invention has very important guiding significance for the industrial application of producing 2,5-diformyl furan by a clean catalytic oxidation method.

Description of drawings

Figure 1 is a gas chromatogram of the substrate HMF before the DFF experiment based on the selective catalytic oxidation of HMF by molecular oxygen assisted active MnO ₂ in the present invention (17.332min corresponds to the peak of HMF).

Figure 2 is a gas chromatogram of the product after a selective catalytic oxidation of HMF based on molecular oxygen assisted active MnO ₂ to generate DFF in the present invention (17.182min corresponds to the HMF peak; 12.692min corresponds to the DFF peak).

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and examples, but it should be noted that the examples do not constitute a limitation to the protection scope of the present invention.

Example 1

Add 0.5103g of HMF, 0.2569g of active MnO ₂ and 27mL of N,N-dimethylformamide (DMF) into a 100ml autoclave, seal it and inject oxygen at 9bar to start the reaction. The stirring speed is 600rpm. Start timing when the temperature rises to 110°C, keep the temperature for 6 hours, and immediately immerse the reaction vessel in cold water to cool down to room temperature after the reaction is completed. The reaction liquid was centrifugally filtered, and the conversion rate of HMF was 85.7% according to gas chromatography; the yield of DFF was 55.7%; the selectivity of DFF was 65%. The gas phase result spectrum of the reaction liquid is shown in Figures 1 and 2, and the specific peak intensity of Example 1 is slightly different.

Example 2

Add 0.5075g of HMF, 0.2577g of active MnO ₂ and 27mL of N,N-dimethylacetamide (DMA) into a 100ml autoclave, seal it and inject oxygen at 7bar to start the reaction. The stirring speed is 550rpm. Start timing when the temperature rises to 115°C, keep the temperature for 20 hours, and immediately immerse the reaction vessel in cold water to cool down to room temperature after the reaction is completed. The reaction solution was centrifuged and filtered, and the conversion rate of HMF was 85.8% according to gas chromatography; the yield of DFF was 68.3%; the selectivity of DFF was 79.7%. The gas phase result spectrum of the reaction liquid is shown in Figures 1 and 2, and the specific peak intensity of Example 2 is slightly different.

Example 3

Add 0.5061g of HMF, 0.2559g of active MnO ₂ and 27mL of N,N-dimethylformamide (DMF) into a 100ml autoclave, seal it and inject oxygen at 9bar to start the reaction. The stirring speed is 800rpm. Start timing when the temperature rises to 100°C, keep the temperature for 8 hours, and immediately immerse the reaction vessel in cold water to cool down to room temperature after the reaction is completed. The reaction solution was centrifugally filtered, and the conversion rate of HMF was 83.3% according to gas chromatography; the yield of DFF was 74.9%; the selectivity of DFF was 89.9%. The gas phase result spectrum of the reaction liquid is shown in Figures 1 and 2, and the specific peak intensity of Example 3 is slightly different.

Example 4

Add 0.5036g of HMF, 0.2522g of active MnO ₂ and 29mL of toluene into a 100ml autoclave, seal it and feed it with oxygen at 8.5bar to start the reaction. React at this temperature for 2 hours. After the reaction is over, immediately immerse the reactor in cold water to cool down to room temperature. The reaction liquid was centrifugally filtered, and the conversion rate of HMF was 71.8% according to gas chromatography; the yield of DFF was 56.9%; the selectivity of DFF was 79.2%. The gas phase result spectrum of the reaction liquid is shown in Figures 1 and 2, and the specific peak intensity of Example 4 is slightly different.

Example 5

Add 0.5092g of HMF, 0.2558g of active MnO ₂ and 24mL of N-methylpyrrolidone (NMP) into a 100ml autoclave, seal it and feed oxygen at 10bar to start the reaction. The stirring speed is 600rpm, and the temperature rises to 90 Start timing at ℃, and keep the temperature for 3.5 hours. After the reaction, immediately immerse the reaction kettle in cold water to cool down to room temperature. The reaction liquid was centrifugally filtered, and the conversion rate of HMF was 74.1% according to gas chromatography; the yield of DFF was 58.9%; the selectivity of DFF was 79.4%. The gas phase result spectrum of the reaction liquid is shown in Figures 1 and 2, and the specific peak intensity of Example 5 is slightly different.

Example 6

Add 0.5106g of HMF, 0.2548g of active MnO ₂ and 32mL of acetonitrile into a 100ml autoclave, seal it and feed it with 8bar of oxygen to start the reaction. The reaction temperature was 4.5h. After the reaction was completed, the reaction kettle was immediately immersed in cold water to cool down to room temperature. The reaction solution was centrifugally filtered, and the conversion rate of HMF was 85.9% according to gas chromatography; the yield of DFF was 49.99%; the selectivity of DFF was 58.2%. The gas phase result spectrum of the reaction liquid is shown in Figures 1 and 2, and the specific peak intensity of Example 6 is slightly different.

Example 7

Add 0.5215g of HMF, 0.2612g of active MnO ₂ and 23mL of dimethyl sulfoxide (DMSO) into a 100ml autoclave, seal it and feed oxygen at 10bar to start the reaction. The stirring speed is 800rpm, and the temperature rises to 110 Start timing at ℃, and keep the temperature for 12 hours. After the reaction is completed, immediately immerse the reaction kettle in cold water to cool down to room temperature. The reaction solution was centrifugally filtered, and the conversion rate of HMF was 91.0% according to gas chromatography; the yield of DFF was 68.5%; the selectivity of DFF was 75.2%. The gas phase result spectrum of the reaction liquid is shown in Figures 1 and 2, and the specific peak intensity of Example 7 is slightly different.

Claims (10)

1. Molecular oxygen assists active MnO Catalytic preparation ₂ , the method for 5-diformyl furan, it is characterized in that its concrete steps are as follows: Using 5-hydroxymethylfurfural (HMF), an important platform compound derived from biomass carbohydrates, as the reaction substrate, molecular oxygen as a clean oxidant, and an organic solvent as a solvent system, the oxidation reaction of HMF occurs under the catalysis of active _MnO2 This produces 2,5-diformylfuran. 2. as claimed in claim 1, molecular oxygen assisted active MnO catalyzes the method for preparing 2,5-diformyl furan, it is characterized in that the mass percent of described HMF and organic _solvent is 1%～5%; The active MnO The amount of ₂ is 10% to 200% of HMF by mass percentage, preferably 40% to 100%. 3. as claimed in claim 1, molecular oxygen assists active MnO Catalytic preparation of 2,5-diformyl furan, it is characterized in that said organic solvent is selected from aromatic reagents such _as toluene, tetrahydrofuran, acetone, acetonitrile, tetrachloromethane Carbon dioxide, methylene chloride, cyclohexane, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, methyl isobutyl ketone, N-methylpyrrolidone, One of the esters, preferably N,N-dimethylformamide. 4. The method for preparing 2,5-diformylfuran by molecular oxygen assisted by active MnO ₂ as claimed in claim 1, wherein said molecular oxygen adopts air or oxygen, preferably oxygen. 5. as claimed in claim 1, molecular oxygen assists active MnO Catalytic preparation of 2,5-diformyl furan, it is characterized in that the oxygen _pressure in the oxidation reaction process is 1～16bar, and the temperature of oxidation reaction is 50 ~130°C, the oxidation reaction time is 0.5~48h. 6. as claimed in claim 5, molecular oxygen assists active MnO _Catalytic preparation of 2,5-diformyl furan, it is characterized in that the oxygen pressure in the oxidation reaction process is 5～10bar; the temperature of oxidation reaction is 100 ~120°C, the best is 110°C; the oxidation reaction time is 2~20h. 7. as claimed in claim 1, molecular oxygen assists active _MnO catalyzes the method for preparing 2,5-diformyl furan, is characterized in that described active MnO _The preparation method is as follows: (1) Add distilled water into KMnO ₄ , stir and dissolve to make KMnO ₄ solution; (2) Add Mn ²⁺ salt to distilled water to make solution A; (3) Transfer the KMnO ₄ solution into a Hastelloy reactor, then add solution A, then add distilled water to constant volume, seal the reactor, heat up and react, cool to room temperature, take a sample and perform suction filtration, and filter out the substance for washing. The filtered sample is dried and then ground to obtain active MnO ₂ black powder with a thickness of less than 6mm. 8. The method for preparing 2,5- _{diformylfuran} catalyzed by molecular oxygen as claimed in claim 7, characterized in that in step (2), the Mn ²⁺ salt is manganese sulfate; the Mn The consumption of ²⁺ salt can be 1.5 times of KMnO ₄ by mass ratio. 9. The method for preparing 2,5- _{diformylfuran} by catalyzing molecular oxygen as claimed in claim 7, characterized in that in step (3), the amount of distilled water added is based on the volume of the Hastelloy reactor The filling rate is 80%; the temperature of the heating reaction can be 150°C, and the time of the heating reaction can be 8h; the washing can be washed 5 to 10 times with distilled water. 10. The method for preparing 2,5- _{diformylfuran} catalyzed by molecular oxygen as claimed in claim 7, characterized in that in step (3), the drying condition is to place the filtered sample Dry in a blast drying oven at 110°C±5°C for 3-4 hours.

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