Preparation method of 2, 5-dicyanofuran

Abstract

The invention belongs to the technical field of biomass catalytic conversion, and particularly relates to a preparation method of 2, 5-dicyanofuran, which comprises the following steps: in the presence of a main catalyst and a cocatalyst, carrying out ammoxidation reaction on 5-hydroxymethylfurfural, an ammonia source and oxygen-containing gas in a reaction medium in a reaction kettle to obtain a reaction liquid containing 2, 5-dicyanofuran; wherein the main catalyst comprises a carrier and an active component loaded on the carrier, the carrier is a nitrogen-doped carbon material, and the active component is an oxide of a non-noble metal; and the cocatalyst is selected from inorganic peroxide compounds and the like. According to the invention, 5-hydroxymethylfurfural is taken as a substrate, and 2, 5-dicyanofuran can be efficiently obtained under mild reaction conditions.

Description

Technical Field

[0001] This invention belongs to the field of biomass catalytic conversion technology, specifically relating to a method for preparing 2,5-dicyanofuran. Background Technology

[0002] The contradiction between the non-renewable nature of fossil fuels and ever-increasing demand is driving a global shift towards renewable energy. Among various renewable energy sources, biomass energy, with its abundant reserves and high renewability, has become an important pathway to replace fossil resources and produce high-value-added chemicals. 5-Hydroxymethylfurfural (HMF), as a core representative of biomass-derived platform molecules, is crucial for the high-value utilization of biomass resources through efficient conversion. A series of highly valuable compounds can be derived from HMF, such as 2,5-furandicarboxylic acid (FDCA), 2,5-dicarboxyfuran (DFF), and 5-hydroxymethyl-2-furancarboxylic acid (HMFCA), which have enormous potential applications in the fine chemical industry.

[0003] Among the many derivatives of HMF, 2,5-dicyanofuran (DCF) has attracted much attention due to the presence of two highly reactive cyano functional groups in its molecule. This unique structural feature makes it an ideal precursor for the synthesis of important chemical intermediates such as hexamethylenediamine. Hexamethylenediamine, in turn, can be reacted with adipic acid to prepare the important engineering plastic Nylon-66. Therefore, DCF shows broad application prospects in materials science, biomedicine, optoelectronics, and environmental science. However, the enormous application potential of this compound contrasts sharply with the bottleneck of its efficient, green, and economical large-scale preparation technology. The traditional synthesis method of DCF is mainly the dehydration method, which uses 2,5-furandicarboxamide as a raw material. Under the action of strong dehydrating agents (such as PCl5, POCl3, P2O5, or SOCl2), the amide is dehydrated to generate nitrile groups (-CN). This method is highly dependent on chlorides or sulfides. These reagents are not only highly hazardous to operate but also generate a large amount of chlorine / sulfur-containing hazardous waste, causing serious environmental pollution and subsequent treatment problems, which contradicts the concept of green chemistry. Another approach is to directly synthesize DCF from HMF in one step via an ammonia oxidation reaction. For example, a method for preparing DCF from HMF has been reported. This method uses metal oxides as catalysts and directly generates DCF through a catalytic oxidation-ammoniation reaction in the presence of an ammonia source and an oxidant. This process involves the oxidation of aldehyde groups in HMF, the formation of imine intermediates, and the final dehydration to form nitrile groups. However, the catalysts used in this reaction, such as NiO, CuO, and CeO2, generally have low catalytic activity, resulting in low DCF yields and limiting its industrial synthesis and application. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention aims to provide a method for preparing 2,5-dicyanofuran. This invention uses 5-hydroxymethylfurfural as a substrate and can efficiently obtain 2,5-dicyanofuran under mild reaction conditions.

[0005] To achieve the above objectives, the method for preparing 2,5-dicyanofuran of the present invention comprises: in the presence of a main catalyst and a co-catalyst, carrying out an ammonia oxidation reaction of 5-hydroxymethylfurfural, an ammonia source, and an oxygen-containing gas in a reaction medium in a reaction vessel to obtain a reaction solution containing 2,5-dicyanofuran; wherein, the main catalyst comprises a support and an active component supported thereon, and the support is a nitrogen-doped carbon material, and the active component is a non-noble metal oxide; the co-catalyst is selected from at least one of inorganic peroxide compounds, halogen oxyacid salts, and nitrogen oxide free radical compounds.

[0006] The method of this invention, under the synergistic effect of the main catalyst and co-catalyst, efficiently synthesizes 2,5-dicyanofuran (DCF):5-hydroxymethylfurfural (HMF) via a multi-stage reaction pathway. The aldehyde group of DCF undergoes amination with an ammonia source to generate an imine intermediate, which is then oxidized to a nitrile group. Meanwhile, the hydroxyl group in the molecule is oxidized to an aldehyde intermediate under the action of oxygen-containing gas, and subsequently oxidized to a nitrile group to form the target cyano group. This method effectively avoids the polymerization problem usually associated with the hydroxyl oxidation of HMF under NH3 conditions, achieving a high yield of the target product. The nitrogen-doped carbon support not only enhances electron conduction and promotes the generation of reactive oxygen species but also stabilizes the metal active center, preventing its deactivation. The non-noble metal oxide selectively activates oxygen molecules, avoiding excessive oxidation side reactions. Simultaneously, the co-catalyst further promotes the directional oxidation of the hydroxymethyl group and the efficient introduction of the cyano group by providing reactive oxygen or regulating electron transfer, thereby improving the conversion rate of HMF and the selectivity of the target product DCF at lower reaction temperatures and pressures.

[0007] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0008] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, wherein:

[0009] Figure 1 The scanning electron microscope (SEM) image of the main catalyst for Preparation Example 1 is shown.

[0010] Figure 2 Transmission electron microscopy-energy dispersive spectroscopy (TEM-EDS) image of the main catalyst for Preparation Example 1;

[0011] Figure 3The gas chromatogram of the reaction solution prepared in Example 1;

[0012] Figure 4 for Figure 3 The mass spectrum of 2,5-dicyanofuran extracted from it. Detailed Implementation

[0013] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0014] The "scope" disclosed in this invention is defined in the form of a lower limit and / or an upper limit, whereby a given scope is defined by selecting a lower limit and / or an upper limit. This scope may or may not include endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form an undefined scope, and any lower limit can be combined with other lower limits to form an undefined scope, similarly, any upper limit can be combined with any other upper limit to form an undefined scope. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and can be combined with any other point or single value, or with other lower or upper limits, to form an undefined scope.

[0015] Unless otherwise specified, all embodiments and optional embodiments of the present invention may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present invention.

[0016] In this invention, the term "metal salt" should be interpreted broadly, encompassing both its anhydrous salts and its hydrates.

[0017] This invention provides a method for preparing 2,5-dicyanofuran, the method comprising: in the presence of a main catalyst and a co-catalyst, carrying out an ammonia oxidation reaction of 5-hydroxymethylfurfural, an ammonia source and an oxygen-containing gas in a reaction medium in a reaction vessel to obtain a reaction solution containing 2,5-dicyanofuran.

[0018] In this invention, the main catalyst comprises a support and an active component loaded thereon, wherein the support is a nitrogen-doped carbon material and the active component is a non-noble metal oxide.

[0019] In this invention, the oxide of the non-noble metal can be represented as MO. xIn this context, M represents a non-noble metal. According to some embodiments, M is selected from at least one of Ni, Cu, Fe, Mn, V, Mo, Ce, and Co. Preferably, the oxide of the non-noble metal is a bimetallic oxide (i.e., composed of oxides of two metals), wherein the non-noble metal M is composed of M1 and M2, where M1 is Ni, Fe, Cu, or Mn, and M2 is V, Mo, Ce, or Co. M1 tends to activate the hydroxymethyl group of HMF, promoting its oxidation to an aldehyde intermediate through coordination, while M2 accelerates the redox cycle, driving the efficient conversion of the aldehyde intermediate to a cyano group. The molar ratio of M1 to M2 can be 1:(1-2), for example, 1:1, 1:1.5, 1:2, etc.

[0020] In this invention, the nitrogen-doped carbon material in the main catalyst can be represented as "CN", and the support can be obtained by pyrolysis of nitrogen-containing organic matter.

[0021] As some specific examples, the main catalyst may be selected from one or more of the following catalysts: NiO x @CN、CuO x @CN、FeO x @CN、MnO x @CN、VO x @CN、MoO x @CN、CeO x @CN、CoO x @CN、Fe-VO x @CN、Ni-VO x @CN、Cu-MoO x @CN、Cu-VO x @CN、Fe-MoO x @CN、Mn-VO x @CN、Mo-CeO x @CN、Cu-CoO x @CN. This can be understood as follows: in the expression "××@CN", CN after "@" represents the support, and "××" before "@" represents the active component loaded on the support. Additionally, when two metal elements are present before "@", it indicates that the active component includes oxides of both metals. For example, "Fe-MoO..." x "Indicates that the active component is FeO" x and MoO x composition.

[0022] In some embodiments, the main catalyst is prepared according to the following method:

[0023] (1) Mix the non-precious metal salt, nitrogen-containing organic matter and organic solvent evenly to obtain a mixture;

[0024] (2) Evaporate the organic solvent in the mixture to obtain a gel-state solid precursor;

[0025] (3) The gel-state solid precursor is dried and ground, and then the ground product is pyrolyzed under an inert atmosphere to obtain the main catalyst.

[0026] In step (1), the non-precious metal salt can be selected from nitrates, vanadates, etc. Specific examples of the nitrates include, but are not limited to, Fe(NO3)2, Ce(NO3)4, Cu(NO3)2, Ni(NO3)2, Mn(NO3)2 and their respective hydrates, and the vanadate can be NaVO3.

[0027] In step (1), the nitrogen-containing organic compound is preferably urea and / or melamine.

[0028] In step (1), the organic solvent is preferably N,N-dimethylformamide (DMF).

[0029] In some embodiments, the mass ratio of the non-precious metal salt to the nitrogen-containing organic compound is (3 to 10):1, for example, 3:1, 4:1, 5:1, 5.5:1, 6:1, 7:1, 8:1, etc.

[0030] In some embodiments, the concentration of the non-precious metal salt in the mixture can be 0.5 to 3 mol / L, for example, 0.5 mol / L, 1 mol / L, 1.2 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, etc.

[0031] In step (2), the evaporation temperature can be selected based on the organic solvent used. According to some embodiments, the evaporation temperature is 100–150°C, for example, 100°C, 110°C, 120°C, 125°C, 140°C, 150°C, etc. Typically, the evaporation time can be 2–15 hours, for example, 2 hours, 5 hours, 7 hours, etc.

[0032] In step (3), the inert gas can be, for example, nitrogen or argon. The conditions of the pyrolysis treatment can be selected according to the nitrogen-containing organic matter, with the aim of decomposing the nitrogen-containing organic matter to obtain nitrogen-doped carbon materials. According to some embodiments, the temperature of the pyrolysis treatment is 500-700°C, 500°C, 550°C, 600°C, 700°C, etc., and the pyrolysis time is 3-5 hours, for example, 3 hours, 4 hours, 5 hours, etc.

[0033] In this invention, the amount of the main catalyst can be selected based on the amount of the reactant 5-hydroxymethylfurfural. According to some embodiments, the mass ratio of the main catalyst to 5-hydroxymethylfurfural is (0.01–60):100, for example, 0.05:100, 1:100, 5:100, 8:100, 12:100, 15:100, 20:100, 25:100, 30:100, 38:100, 45:100, 50:100, 60:100, etc. Generally, too little of the main catalyst may affect the reaction rate and conversion efficiency, while too much of the main catalyst may lead to side reactions (such as over-oxidation). Preferably, the mass ratio of the main catalyst to 5-hydroxymethylfurfural is (5–50):100.

[0034] In this invention, the co-catalyst is designed to synergistically enhance the efficiency of the HMF ammonia oxidation reaction and the selectivity of 2,5-dicyanofuran (DCF) with the main catalyst, and is specifically selected from at least one of inorganic peroxide compounds, halogenated oxyacid salts, and nitric oxide radical compounds.

[0035] In this invention, the inorganic peroxide compound can promote the oxidation of hydroxyl groups to aldehyde groups in HMF, and also promote the oxidative dehydrogenation of the imine intermediate generated by aldehyde amination to form a cyano group (-CN), while inhibiting the deactivation of the main catalyst and maintaining the oxidative environment of the reaction system. According to some embodiments, the inorganic peroxide compound is selected from hydrogen peroxide and / or persulfate.

[0036] In this invention, the halogen oxyacid salt can selectively oxidize the hydroxymethyl group of HMF, avoiding excessive oxidation that could lead to ring-opening of the furan ring or the formation of carboxylic acid byproducts. According to some embodiments, the halogen oxyacid salt is a hypochlorite, preferably sodium hypochlorite.

[0037] As some preferred examples, the co-catalyst is selected from at least one of hydrogen peroxide, potassium persulfate, potassium peroxymonosulfate, sodium peroxymonosulfate, 2,2,6,6-tetramethylpiperidine oxide (TEMPO), and sodium hypochlorite, more preferably 2,2,6,6-tetramethylpiperidine oxide.

[0038] In this invention, the mass ratio of the co-catalyst to the reactant 5-hydroxymethylfurfural can be (0.1–200):100, for example, 1:100, 5:100, 10:100, 15:100, 30:100, 50:100, 100:100, 120:100, 150:100, 200:100, etc. Generally, too low a amount of co-catalyst may affect the reaction efficiency, while too high a amount of co-catalyst cannot significantly improve the product yield. Preferably, the mass ratio of the co-catalyst to the reactant 5-hydroxymethylfurfural is (10–80):100.

[0039] In this invention, the oxygen-containing gas acts as an oxidant, reacting with HMF to form an aldehyde intermediate. The oxygen-containing gas can be air or oxygen. Based on the oxygen content in the oxygen-containing gas, the molar ratio of the oxygen-containing gas to 5-hydroxymethylfurfural can be (5–22):1, for example, 5:1, 9:1, 10:1, 11:1, 15:1, 20:1, 22:1, etc.

[0040] In this invention, the ammonia source reacts with the aldehyde group in the substrate to form the target product. The ammonia source can be ammonia gas or a compound that releases ammonia gas at the reaction temperature. Specifically, the ammonia source can be one or more of a gaseous ammonia source (i.e., ammonia gas), a liquid ammonia source, and a solid ammonia source. The gaseous ammonia source is ammonia gas, the liquid ammonia source can be an ammonia-methanol solution and / or ammonia water, preferably an ammonia-methanol solution; and the solid ammonia source is preferably ammonium carbonate and / or ammonium bicarbonate.

[0041] In this invention, the molar ratio of the ammonia source to 5-hydroxymethylfurfural is preferably (1-20):1, for example, 1.5:1, 2:1, 5:1, 6:1, 7:1, 8:1, 9:1, 11:1, 15:1, 20:1, etc. It should be understood that when the ammonia source is an ammonia-methanol solution, the molar ratio of the ammonia source to 5-hydroxymethylfurfural is based on the NH3 content in the ammonia-methanol solution. The ammonia-methanol solution can be, for example, a 7N ammonia-methanol solution. As some preferred embodiments, the ammonia source is ammonia gas, and the molar ratio of the ammonia gas to 5-hydroxymethylfurfural is (4-7):1.

[0042] The present invention does not particularly limit the reaction medium, as long as it can dissolve the substrate. As some examples, the reaction medium is selected from at least one of methanol, ethanol, n-propanol, isopropanol, n-butanol, tetrahydrofuran, acetonitrile, benzonitrile, N,N-dimethylformamide, dimethyl sulfoxide, and water. Furthermore, the concentration of 5-hydroxymethylfurfural in the reaction medium can be 0.002–0.5 g / mL, for example, 0.004 g / mL, 0.008 g / mL, 0.01 g / mL, 0.02 g / mL, 0.03 g / mL, 0.05 g / mL, 0.1 g / mL, 0.2 g / mL, 0.3 g / mL, 0.35 g / mL, 0.5 g / mL, etc.

[0043] In this invention, the conditions for the ammonia oxidation reaction may include: a temperature of 20–200°C, such as 20°C, 50°C, 60°C, 75°C, 90°C, 100°C, 110°C, 130°C, 155°C, 170°C, etc.; and a time of 1–48 h, such as 1 h, 2 h, 3 h, 5 h, 7 h, 8 h, 12 h, 15 h, 20 h, 22 h, 30 h, etc. Specifically, in the presence of the main catalyst and the co-catalyst, this invention not only efficiently obtains the target product but also allows the reaction to proceed under relatively mild conditions. Therefore, the preferred reaction temperature is 40–80°C, and the reaction time is 3–8 h. As some specific examples, the ammonia oxidation reaction can be carried out in a high-pressure reactor with a volume of 20–30 mL (e.g., 20 mL, 25 mL, 30 mL, etc.), wherein the amount of substrate can be 1–10 mmol, such as 3 mmol, 5 mmol, 8 mmol, etc.

[0044] In some embodiments, the preparation method of the present invention further includes: performing solid-liquid separation on the obtained reaction system (e.g., by vacuum filtration) to recover the main catalyst and the reaction solution containing 2,5-dicyanofuran, respectively.

[0045] The method for preparing 2,5-dicyanofuran of the present invention has the advantages of mild reaction conditions and high selectivity of ammonia oxidation reaction. The catalytic system used reduces side reactions in the synthesis process, improves the utilization rate of raw materials and the yield of target product, and reduces the difficulty of product purification.

[0046] The following describes embodiments of the present invention. These embodiments are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0047] The following preparation examples illustrate the main catalysts used in the embodiments and comparative examples and their preparation methods.

[0048] Preparation Example 1

[0049] 10 mmol NaVO3 and 5 mmol Cu(NO3)2·3H2O were added to 15 mL of N,N-dimethylformamide (DMF) and stirred until homogeneous. Then, 0.8 g of urea was added, and stirring continued for 30 min to form a mixture. The mixture was transferred to a round-bottom flask and placed in an oil bath at 150 °C. The solvent was slowly evaporated with stirring until a viscous gel-like solid was formed. The gel-like solid was dried until the solvent was completely evaporated. The resulting solid was then ground into a fine powder and placed in a tube furnace. The temperature was increased to 600 °C at a rate of 5 °C / min under a nitrogen atmosphere and pyrolyzed at this temperature for 4 h. After pyrolysis, the mixture was allowed to cool naturally to room temperature to obtain a black powdered catalyst, Cu-VO3. x @CN, denoted as Cat-1. Figure 1The SEM image shows the microstructure of the catalyst, revealing a porous and rough surface morphology with a well-developed interconnected pore network. Figure 2 The TEM-EDS image of the catalyst shows that V and Cu species are uniformly distributed on the surface of the support CN.

[0050] Preparation Examples 2-7

[0051] The two-component catalysts Cat-2 to Cat-7 were prepared according to the method of Example 1, except that the type and amount of metal salt were adjusted. The prepared catalysts are shown in Table 1.

[0052] Comparative Preparation Example 1

[0053] 10 mmol Cu(NO3)2·3H2O was dissolved in 15 mL DMF and magnetically stirred for 30 minutes until completely dissolved, forming a transparent solution. The mixture was transferred to a round-bottom flask and stirred in an oil bath at 150 °C to slowly evaporate the solvent until a gel-like solid precursor was formed. The gel-like solid precursor was dried until the solvent was completely evaporated, and the resulting solid was ground into a fine powder. The powder was then placed in a tube furnace and pyrolyzed at 600 °C at a heating rate of 5 °C / min under an oxygen atmosphere for 4 hours to obtain the catalyst CuO, denoted as Cat-D1.

[0054] Table 1

[0055]

[0056]

[0057] The following examples illustrate the preparation method of 2,5-dicyanofuran according to the present invention.

[0058] Qualitative analysis of the products: Gas chromatography-mass spectrometry (GC-MS, Thermo Fisher Trace 1300 & ISQ-LT) was used with a TR-5MS capillary column (15.0 m × 250 μm × 0.25 μm) and helium as the carrier gas. The temperature was programmed (50 °C for 2 min, then increased to 260 °C at 10 °C / min and held for 5 min). The retention times of the NIST 17 standard library and standards were compared.

[0059] Product quantification: Gas chromatography (GC, Agilent 7890B) equipped with a flame ionization detector (FID), DB-INNOWAXETR capillary column (30m × 0.25mm × 0.25μm), using nitrogen as carrier gas and o-dichlorobenzene as internal standard, was employed. A standard curve was established based on the external standard method for quantification. Samples were filtered through a 0.22μm filter before injection. HMF conversion and product yield were calculated using the following formulas.

[0060]

[0061] Example 1

[0062] At room temperature, 63 mg HMF, 13 mg Catalyst Cat-1, 13 mg 2,2,6,6-Tetramethylpiperidine oxide (TEMPO), and 5 mL acetonitrile were added sequentially to a 25 mL high-pressure reactor. The reactor was sealed, and the gas inside was replaced with air three times. Then, 0.25 MPa of ammonia (NH3) and 1 MPa of oxygen (O2) were injected into the reactor. The reactor was placed in an oil bath, rapidly stirred (600 rpm), and heated to 80 °C for 4 hours. After the reaction was completed, the reactor was cooled to room temperature, and the pressure was slowly reduced to atmospheric pressure. The mixture was then filtered to recover the catalyst and obtain the reaction solution. GC-MS analysis of the reaction solution yielded the following results: Figure 3 and Figure 4 As shown, where, Figure 3 This is the GC graph from GC-MS detection. Figure 4 yes Figure 3 Mass spectrum of the intermediate product 2,5-dicyanofuran. Figure 3 The results show that the characteristic peak of the target product DCF is at 7.09 min, the characteristic peak of TEMPO is at 8.67 min, and the characteristic peak of the reaction intermediate 5-hydroxymethylfuran-2-carboxynitrile (HMFA) is at 10.68 min. Figure 3 The peak that appears at 7.09 min is Figure 4 The mass spectrometry analysis identified it as DCF. This demonstrates that Example 1 exhibits high reaction selectivity. Furthermore, GC quantitative analysis showed a DCF yield of 95.2%.

[0063] Example 2

[0064] At room temperature, 63 mg HMF, 15 mg Cat-2 catalyst, 12 mg TEMPO, and 5 mL acetonitrile were added sequentially to a 25 mL high-pressure reactor. The reactor was sealed, and the gas inside was replaced with air three times. Then, 0.3 MPa of ammonia and 1 MPa of oxygen were injected into the reactor. The reactor was placed in an oil bath, rapidly stirred (600 rpm), and heated to 70 °C for 6 hours. After the reaction was completed, the reactor was cooled to room temperature, and the gas was slowly vented to atmospheric pressure. The mixture was then filtered to recover the catalyst and obtain the reaction solution. The reaction solution was analyzed, and the degree of reaction was calculated. The test results are shown in Table 2.

[0065] Example 3

[0066] 60 mg HMF, 12 mg Cat-3 catalyst, 14 mg TEMPO, and 5 mL acetonitrile were added sequentially to a 25 mL high-pressure reactor. The reactor was sealed, and the gas inside was replaced with air three times. Then, 0.3 MPa of ammonia and 1 MPa of oxygen were injected into the reactor. The reactor was placed in an oil bath, rapidly stirred (600 rpm), and heated to 60 °C for 5 hours. After the reaction was completed, the reactor was cooled to room temperature, and the gas was slowly vented to atmospheric pressure. The mixture was then filtered to recover the catalyst and obtain the reaction solution. The reaction solution was analyzed, and the degree of reaction was calculated. The test results are shown in Table 2.

[0067] Example 4

[0068] 70 mg HMF, 12 mg Cat-4 catalyst, 20 mg TEMPO, and 8 mL acetonitrile were added sequentially to a 25 mL high-pressure reactor. The reactor was sealed, and the gas inside was replaced with air three times. Then, 0.5 MPa of ammonia and 1 MPa of oxygen were injected into the reactor. The reactor was placed in an oil bath, rapidly stirred (600 rpm), and heated to 80 °C for 3 hours. After the reaction was completed, the reactor was cooled to room temperature, and the gas was slowly vented to atmospheric pressure. The mixture was then filtered to recover the catalyst and obtain the reaction solution. The reaction solution was analyzed, and the degree of reaction was calculated. The test results are shown in Table 2.

[0069] Example 5

[0070] 70 mg HMF, 9 mg Cat-5 catalyst, 15 mg TEMPO, and 8 mL acetonitrile were added sequentially to a 25 mL high-pressure reactor. The reactor was sealed, and the gas inside was replaced with air three times. Then, 0.5 MPa of ammonia and 1 MPa of oxygen were injected into the reactor. The reactor was placed in an oil bath, rapidly stirred (600 rpm), and heated to 70 °C for 3 hours. After the reaction was completed, it was cooled to room temperature, and the gas was slowly vented to atmospheric pressure. The mixture was then filtered to recover the catalyst and obtain the reaction solution. The reaction solution was analyzed, and the degree of reaction was calculated. The test results are shown in Table 2.

[0071] Examples 6-7

[0072] 2,5-Dicyanofuran was prepared according to the method in Example 1, except that the catalyst Cat-1 was replaced with Cat-6 and Cat-7, respectively. The obtained reaction solution was analyzed and the degree of reaction was calculated. The test results are shown in Table 2.

[0073] Comparative Example 1

[0074] 2,5-Dicyanofuran was prepared according to the method in Example 1, except that TEMPO was not used and the catalyst was replaced with Cat-D1. The obtained reaction solution was analyzed and the degree of reaction was calculated. The test results are shown in Table 2.

[0075] Comparative Example 2

[0076] 2,5-Dicyanofuran was prepared according to the method in Example 1, except that TEMPO was not added and the catalyst was replaced with Cat-6. The obtained reaction solution was analyzed and the degree of reaction was calculated. The test results are shown in Table 2.

[0077] Table 2

[0078] Serial Number Catalyst number main catalyst co-catalyst HMF conversion rate DCF yield Example 1 Cat-1 <![CDATA[Cu-VO x @CN]]> TEMPO 99.9％ 95.2％ Example 2 Cat-2 <![CDATA[Cu-VO x @CN]]> TEMPO 99.9％ 88.5％ Example 3 Cat-3 <![CDATA[Cu-VO x @CN]]> TEMPO 99.9％ 92.1％ Example 4 Cat-4 <![CDATA[Cu-MnO x @CN]]> TEMPO 99.9％ 86.3％ Example 5 Cat-5 <![CDATA[Fe-VO x @CN]]> TEMPO 99.9％ 80.4％ Example 6 Cat-6 <![CDATA[CuO x @CN]]> TEMPO 99.9％ 73.2％ Example 7 Cat-7 <![CDATA[NiO x @CN]]> TEMPO 99.9％ 79.8％ Comparative Example 1 Cat-D1 CuO / 99.9％ 52.7％ Comparative Example 2 Cat-6 <![CDATA[CuO x @CN]]> / 99.9％ 61.8％

[0079] Note: 99.9% means that the characteristic peaks of HMF cannot be observed from the GC plot, which is considered as complete HMF transformation.

[0080] Examples 8-11

[0081] 2,5-Dicyanofuran was prepared according to the method in Example 1, except that the amount of Cat-1 or TEMPO was adjusted. The obtained reaction solution was analyzed and the degree of reaction was calculated. The test results are shown in Table 3.

[0082] Table 3

[0083]

[0084]

[0085] Example 12

[0086] At room temperature, 63 mg HMF, 5 mg Cat-7 catalyst, 33.5 mg hydrogen peroxide (H2O2 concentration 30 wt%), 10 mL acetonitrile, and 0.75 mL ammonia-methanol solution (7N) were added sequentially to a 25 mL high-pressure reactor. The reactor was sealed, and the gas inside was replaced with air three times. Then, air was introduced into the reactor at 3 MPa. The reactor was placed in an oil bath, rapidly stirred (600 rpm), and heated to 100 °C for 6 hours. After the reaction was completed, it was cooled to room temperature, and the gas was slowly vented to atmospheric pressure. The mixture was then filtered to recover the catalyst and obtain the reaction solution. The reaction solution was analyzed, and the degree of reaction was calculated. The test results are shown in Table 4.

[0087] Example 13

[0088] At room temperature, 63 mg HMF, 15 mg Cat-5 catalyst, 50 mg potassium persulfate, and 10 mL acetonitrile were added sequentially to a 25 mL high-pressure reactor. The reactor was sealed, and the gas inside was replaced with air three times. Then, 0.25 MPa ammonia and 0.5 MPa oxygen were introduced into the reactor. The reactor was placed in an oil bath, rapidly stirred (600 rpm), and heated to 80 °C for 4 hours. After the reaction was completed, the reactor was cooled to room temperature, and the gas was slowly vented to atmospheric pressure. The mixture was then filtered to recover the catalyst and obtain the reaction solution. The reaction solution was analyzed, and the degree of reaction was calculated. The test results are shown in Table 4.

[0089] Examples 14-15

[0090] 2,5-Dicyanofuran was prepared according to the method in Example 13, except that the co-catalyst and its amount, reaction temperature, and reaction time were adjusted. The obtained reaction solution was analyzed and the degree of reaction was calculated. The test results are shown in Table 4.

[0091] Table 4

[0092]

[0093]

[0094] Example 16

[0095] At room temperature, 63 mg HMF, 10 mg Catalyst Cat-1, 20 mg TEMPO, 15 mL DMF, and 80 mg ammonium carbonate were added sequentially to a 25 mL high-pressure reactor. The reactor was sealed, and the gas inside was replaced with air three times. Then, 2 MPa of air was injected into the reactor. The reactor was placed in an oil bath, rapidly stirred (600 rpm), and heated to 50 °C for 8 hours. After the reaction was completed, it was cooled to room temperature, and the gas was slowly vented to atmospheric pressure. The mixture was then filtered to recover the catalyst and obtain the reaction solution. The reaction solution was analyzed, and the degree of reaction was calculated. The test results are shown in Table 5.

[0096] Example 17

[0097] 2,5-Dicyanofuran was prepared according to the method in Example 16, except that the ammonia source and its amount, reaction temperature, and reaction time were adjusted. The obtained reaction solution was analyzed and the degree of reaction was calculated. The test results are shown in Table 5.

[0098] Table 5

[0099]

[0100] In summary, by comparing Examples 1 to 17 with Comparative Examples 1 and 2, and referring to Tables 1 to 5, it can be seen that the methods of Examples 1 to 17 can not only achieve a higher conversion rate of HMF, but also obtain a higher DCF yield.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for preparing 2,5-dicyanofuran, characterized in that, include: In the presence of a main catalyst and a co-catalyst, 5-hydroxymethylfurfural, an ammonia source, and an oxygen-containing gas undergo an ammonia oxidation reaction in a reaction medium within a reactor to obtain a reaction solution containing 2,5-dicyanofuran; wherein... The main catalyst comprises a support and an active component loaded thereon, wherein the support is a nitrogen-doped carbon material and the active component is a non-noble metal oxide. The cocatalyst is selected from at least one of inorganic peroxide compounds, halogenated oxyacid salts, and nitroxide free radical compounds.

2. The preparation method according to claim 1, characterized in that, In the oxide of the non-noble metal, the non-noble metal is selected from at least one of Ni, Cu, Fe, Mn, V, Mo, Ce and Co; Preferably, the non-precious metal is composed of M1 and M2, wherein M1 is Ni, Fe, Cu or Mn, M2 is V, Mo, Ce or Co, and the molar ratio of M1 to M2 is 1:(1~2). Preferably, the mass ratio of the main catalyst to 5-hydroxymethylfurfural is (0.01-60):

100.

3. The preparation method according to claim 1 or 2, characterized in that, The main catalyst was prepared according to the following method: (1) Mix the non-precious metal salt, nitrogen-containing organic matter and organic solvent evenly to obtain a mixture; (2) Evaporate the organic solvent in the mixture to obtain a gel-state solid precursor; (3) The gel-state solid precursor is dried and ground, and then the ground product is pyrolyzed under an inert atmosphere to obtain the main catalyst; wherein, The mass ratio of the non-precious metal salt to the nitrogen-containing organic matter is (3-10):1, and the concentration of the non-precious metal salt in the mixture is 0.5-3 mol / L; Preferably, the nitrogen-containing organic compound is urea and / or melamine; Preferably, the organic solvent is N,N-dimethylformamide.

4. The preparation method according to claim 3, characterized in that, The pyrolysis conditions include a temperature of 500–700°C and a pyrolysis time of 3–5 hours.

5. The preparation method according to any one of claims 1-4, characterized in that, The co-catalyst is selected from at least one of 2,2,6,6-tetramethylpiperidine oxide, hydrogen peroxide, potassium persulfate, potassium peroxymonosulfate, sodium peroxymonosulfate, and sodium hypochlorite, preferably 2,2,6,6-tetramethylpiperidine oxide; Preferably, the mass ratio of the co-catalyst to the reactant 5-hydroxymethylfurfural is (0.1-200):

100.

6. The preparation method according to any one of claims 1-5, characterized in that, The oxygen-containing gas is oxygen or air, and the molar ratio of the oxygen-containing gas to 5-hydroxymethylfurfural is (5-22):1, based on the oxygen content in the oxygen-containing gas.

7. The preparation method according to any one of claims 1-6, characterized in that, The ammonia source is selected from at least one of ammonia gas, ammonia methanol solution, ammonium carbonate, and ammonium bicarbonate; Preferably, the molar ratio of the ammonia source to 5-hydroxymethylfurfural is (1-20):1; Preferably, the ammonia source is ammonia gas, and the molar ratio of ammonia gas to 5-hydroxymethylfurfural is (4-7):

1.

8. The preparation method according to any one of claims 1-7, characterized in that, The reaction medium is selected from at least one of methanol, ethanol, n-propanol, isopropanol, n-butanol, tetrahydrofuran, acetonitrile, benzonitrile, N,N-dimethylformamide, dimethyl sulfoxide, and water; Preferably, the concentration of 5-hydroxymethylfurfural in the reaction medium is 0.002–0.5 g / mL.

9. The preparation method according to any one of claims 1-8, characterized in that, The conditions for the ammonia oxidation reaction include: a temperature of 20–200°C, preferably 40–80°C; and a reaction time of 1–48 h, preferably 3–8 h.

10. The preparation method according to any one of claims 1-9, characterized in that, Also includes: The resulting reaction system was subjected to solid-liquid separation to recover the main catalyst and the reaction solution containing 2,5-dicyanofuran, respectively.

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