Iron / carbon composite materials, their preparation methods, and their application in the hydrogenolysis of 5-HMF.

Abstract

This invention discloses an iron / carbon composite material, its preparation method, and its application in the hydrogenolysis reaction of 5-HMF. The iron / carbon composite material includes a carbon matrix and iron(III) oxide dispersed on the carbon matrix. The particle size of the iron(III) oxide is 10-50 nm, and the mass fraction of iron(III) oxide in the iron / carbon composite material is 8 wt%-20 wt%. The application in the hydrogenolysis reaction includes the following steps: (1) Pre-reduction process: The iron / carbon composite material is used as a catalyst, placed in a quartz tube, and a mixture of hydrogen and nitrogen is introduced. The mixture is then calcined at 400-600 °C; (2) A 5-HMF solution is pumped in using a syringe, hydrogen is introduced, and a hydrogenation reaction is carried out under normal pressure. The product is then collected. The iron / carbon composite material of this invention is used as a catalyst. The hydrogenolysis reaction is carried out under normal pressure. The 5-MF selectivity is high, the catalyst stability is good, and the catalyst is magnetic, making it easy to separate and recover.

Description

Technical Field

[0001] This invention relates to the field of fine chemical production technology, mainly to the field of hydrogenolysis reaction technology of 5-HMF, specifically to an iron / carbon composite material and its preparation method and its application in the hydrogenolysis reaction of 5-HMF. Background Technology

[0002] Currently, the extraction of fossil resources is constantly increasing, while the recoverable reserves are gradually decreasing. Therefore, finding sustainable energy sources to replace fossil resources is urgent. Biomass is widely considered to be the only renewable organic carbon resource on Earth, and its converted value-added chemicals and fuels have the potential to replace traditional petrochemical products. Converting readily available plant-derived raw materials such as glucose, fructose, and cellulose into the platform compound 5-hydroxymethylfurfural (5-HMF) is one of the important pathways for biomass catalytic conversion. 5-HMF can be hydrogenated, hydrogenolyzed, or oxidized into a variety of high-quality derivatives, such as 2,5-furandiethanol (DHMF), 2,5-dimethylfurfural (DMF), and 5-methylfurfural (5-MF). Among them, 5-methylfurfural (5-MF) is an important fine chemical that can be used to prepare flavorings in the food industry, potential antitumor agents, common organic synthesis intermediates, and perfumes. 5-MF possesses multiple functional groups, such as furan rings, carbonyl groups, and double bonds, and can be used to synthesize more than 70 compounds. HMF has three different functional groups that can undergo hydrogenation: C=O, C=C, and CO. The hydrogenation reaction of C=O is faster than the other two functional groups. Avoiding the hydrogenation of the aldehyde functional group while reducing the hydroxyl group of the alcohol is a challenge. Currently, most catalysts for the catalytic hydrogenolysis of 5-HMF to 5-MF are noble metals, with a few using non-noble metal catalysts, and the reaction must be carried out under high pressure. Patent CN107353268A discloses a method for selectively hydrogenating 5-hydroxymethylfurfural to 5-methylfurfural. 5-hydroxymethylfurfural, solvent, catalyst, and hydrogen donor are added to a high-pressure reactor, and the hydrogenation reaction is carried out at 20-300℃. The catalyst used is a supported catalyst, and the supported metal is one or two of Pd, Pt, Ru, Rh, Ir, Au, Ag, Co, Ni, and Cu. This reaction is carried out under high pressure, and the catalysts used, except for Co, Ni, and Cu, are all noble metals.

[0003] Non-precious metals offer advantages such as low cost and controllable performance. Currently, non-precious metal catalysts used for HMF oxidation and hydrogenolysis are mainly bimetallic or polymetallic catalysts. For example, invention patent CN118292000A discloses a sulfur-doped nickel-cobalt-based electrocatalytic oxidation catalyst for 5-hydroxymethylfurfural, which can promote the electrocatalytic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid. However, existing non-precious metal catalysts used in 5-HMF hydrogenolysis are mainly bimetallic or polymetallic catalysts, which have complex preparation processes and high costs, hindering industrial application. The catalytic effect and stability of single non-precious metal catalysts need further improvement. Existing catalysts require separation and recovery after hydrogenolysis, increasing costs and hindering industrial promotion. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, this invention provides an iron / carbon composite material, its preparation method, and its application in the hydrogenolysis reaction of 5-HMF. It involves preparing an iron-based MOF-derived carbon material as a catalyst for the catalytic hydrogenation reaction of 5-HMF, completing the hydrogenation reaction under normal pressure to synthesize 5-MF. The selectivity of 5-MF can be adjusted by controlling the side chain groups of the catalyst. This catalyst exhibits high stability and magnetic properties, facilitating the separation of the catalyst and product and making it easy to recover.

[0005] To achieve the purpose of the invention, the present invention adopts the following technical solution:

[0006] An iron / carbon composite material, characterized in that it comprises a carbon matrix and iron(III) oxide dispersed on the carbon matrix, wherein the particle size of the iron(III) oxide is 10-50 nm, and the mass fraction of iron(III) oxide in the iron / carbon composite material is 8 wt%-20 wt%, preferably 10 wt%-20 wt%, and more preferably 15 wt%-17 wt%.

[0007] Preferably, the intensity ratio of the D band to the G band of the Raman spectrum of the above-mentioned iron / carbon composite material, ID / IG, is 1.5-3.0, and more preferably 1.5-2.0.

[0008] This invention also provides a method for preparing an iron / carbon composite material, characterized by comprising the following steps:

[0009] (1) Add ferric salt and organic ligand to N,N-dimethylformamide and form an iron-based metal-organic framework material after solvothermal reaction;

[0010] (2) The iron-based metal-organic framework material was calcined under an inert atmosphere to obtain an iron / carbon composite material.

[0011] Preferably, in the above preparation method, the organic ligand is selected from terephthalic acid, 2-hydroxyterephthalic acid, or 2,5-dihydroxyterephthalic acid.

[0012] Preferably, in the above preparation method, the trivalent iron salt is selected from ferric chloride or ferric nitrate.

[0013] Preferably, in the above preparation method, the molar ratio of the iron salt to the organic ligand is (1-1.2):1, and the mass-volume ratio of the iron salt to N,N-dimethylformamide is (2.0-3.0) g:30 mL.

[0014] Preferably, in the above preparation method, the temperature of the solvothermal reaction is 140-160℃, and the reaction time is 10-15 hours.

[0015] Preferably, in the above preparation method, the calcination temperature is 250-850℃, more preferably 400-650℃. The calcination time is 4-6 hours. The heating rate is 3-5℃ / min.

[0016] Preferably, in the above preparation method, the inert atmosphere is selected from nitrogen or argon.

[0017] The present invention also provides a catalyst for the hydrogenolysis reaction of 5-HMF, characterized in that the catalyst comprises the above-mentioned iron / carbon composite material.

[0018] Preferably, the particle size of the composite material is 60 mesh to 80 mesh.

[0019] This invention also provides an application of an iron / carbon composite material in the hydrogenolysis reaction of 5-HMF, characterized by comprising the following steps:

[0020] (1) Pre-reduction process: The iron / carbon composite material described in claim 1 is placed in a quartz tube, and a mixture of hydrogen and nitrogen is introduced and calcined at 400-600℃;

[0021] (2) Pump 5-HMF solution into the syringe, introduce hydrogen gas, carry out hydrogenation reaction under normal pressure, and collect the product.

[0022] Preferably, in the above application, in step (1), the volume ratio of hydrogen to nitrogen in the mixed gas is (1-2):1. The calcination time is 2-5 hours. The flow rate of the mixed gas is 40-60 mL / min.

[0023] Preferably, in the above application, in step (2), the solvent used in the 5-HMF solution is a mixture of organic solvent and water, and the volume ratio of the organic solvent to water is (1.5-4):1, preferably (2-4):1.

[0024] Preferably, in the above applications, the organic solvent is selected from isopropanol, isobutanol, acetonitrile, dimethyl sulfoxide, or 1,4-dioxane, and is more preferably isopropanol or isobutanol.

[0025] Preferably, in the above applications, the concentration of the 5-HMF solution is 10-15 mg / mL. The mass-to-volume ratio of the catalyst to the 5-HMF solution is (0.1-0.3) g: 1 mL / h. The hydrogen flow rate is 15-25 mL / min.

[0026] Preferably, in the above applications, the temperature of the hydrogenation reaction is 240-320℃, more preferably 260-320℃, and even more preferably 260-300℃.

[0027] Preferably, in the above applications, the hydrogenation reaction time is 1-8 hours.

[0028] Preferably, in the above applications, the 5-HMF conversion rate is 60%-100%, more preferably 90-100%, and even more preferably 95-100%.

[0029] Preferably, in the above applications, the 5-MF selectivity is 60%-80%, more preferably 70-80%, and even more preferably 75-80%.

[0030] The periodic network structure formed by metal ions and organic ligands in metal-organic framework (MOF) materials helps prevent the aggregation of metal or metal oxide nanoparticles during pyrolysis and facilitates the orderly dispersion of metals. Iron, as the most abundant transition element in the Earth's crust, is inexpensive and readily available, making it the most promising non-precious metal element for the hydrogenolysis of 5-HMF. Compared with existing technologies, the beneficial effects of this invention are as follows: (1) This invention uses iron-based MOF as a precursor to prepare an iron / carbon composite material, which, as a catalyst for the hydrogenolysis of 5-HMF, exhibits significant catalytic effects, with a 5-HMF conversion rate of up to 100% and a 5-MF selectivity of up to 80%; (2) The catalyst of this invention has good stability, and the hydrogenolysis reaction is carried out under normal pressure, making it safer; (3) The catalyst of this invention is magnetic and easy to separate and recover; (4) This invention reveals the influence of hydroxyl functional groups on the surface of the iron / carbon composite material on the hydrogenolysis of 5-HMF, providing insights for future optimization of catalyst structures. Attached Figure Description

[0031] Figure 1 The XRD patterns of the iron-based MOFs obtained in Examples 1, 2, and 3 are shown.

[0032] Figure 2 The XRD patterns are of the iron / carbon composite materials obtained in Examples 1, 2, and 3.

[0033] Figure 3 (a) is a transmission electron microscope image of the iron / carbon composite material obtained in Example 1, with a scale bar of 100 nm.

[0034] Figure 3(b) is a transmission electron microscope image of the iron / carbon composite material obtained in Example 2, with a scale bar of 100 nm.

[0035] Figure 3 (c) is a transmission electron microscope image of the iron / carbon composite material obtained in Example 3, with a scale bar of 50 nm.

[0036] Figure 4 The graphs show the conversion rate of 5-HMF over time during the hydrogenation reaction in Examples 1, 2, and 3.

[0037] Figure 5 The graphs show the change in selectivity of product 5-MF over time during the hydrogenation reaction in Examples 1, 2, and 3.

[0038] Figure 6 The graphs show the change in selectivity of the product 2,5-DMF over time during the hydrogenation reaction in Examples 1, 2, and 3. Detailed Implementation

[0039] Given that the catalytic effect and stability of existing single non-precious metal catalysts still need to be improved, this invention uses iron-based MOF as a precursor to prepare a catalyst suitable for the hydrogenolysis reaction of 5-HMF, and the obtained 5-MF has high selectivity.

[0040] In a preferred embodiment, the preparation method of the iron / carbon composite material of the present invention includes the following steps: 1,4-BDC (1.32 g) and FeCl3·6H2O (2.16 g) are added to 30 mL of DMF, and the resulting solution is stirred into a homogeneous solution at room temperature. Subsequently, it is transferred to a stainless steel hydrothermal synthesis reactor (100 mL) and stored at 150 °C for 12 hours. After the liquid product has cooled naturally, it is centrifuged, and then the resulting product powder is soaked in deionized water (250 mL) overnight, centrifuged again, and finally the sample is placed in a vacuum drying oven and dried at 80 °C for 24 hours. The prepared precursor is then subjected to a nitrogen atmosphere in a tube furnace at 5 °C·min. -1 The heating rate was 450℃ for 4 hours, and then cooled to room temperature to obtain an iron / carbon composite material.

[0041] In another preferred embodiment, the application of the iron / carbon composite material of the present invention in the 5-HMF hydrogenolysis reaction includes the following steps: the catalyst is first ground in a mortar for ten minutes, then loaded into a tableting mold and tableted in a tableting machine. Subsequently, 0.2g of the catalyst falling through the 60-80 mesh sieve is granulated using 60-mesh and 80-mesh sieves for the reaction. The catalyst is then loaded into a quartz tube with an inner diameter of 0.7cm to prepare a concentration of 12.6mg·ml. -1 The 5-HMF solution was injected into the reactor using a syringe (1 ml / h). -1Before the reaction, the catalyst was pre-reduced at 500°C for 2 hours with H2 / N2 flow, and then the reaction was carried out under H2.

[0042] This invention investigates the effect of side chain groups on the use of MOF-derived Fe / C composite materials for catalytic hydrogenolysis of 5-HMF. The organic ligands of the synthesized catalyst are terephthalic acid, 2-hydroxyterephthalic acid, and 2,5-dihydroxyterephthalic acid. The three ligands have different numbers of hydroxyl groups in their side chain groups, resulting in different numbers of hydroxyl groups on the carbon material surface. This leads to an increase in the adsorption energy for HMF and 5-MF with increasing number of hydroxyl groups, making it difficult for 5-MF to desorb and undergo further hydrogenolysis, thus resulting in differences in the selectivity for the product 5-MF.

[0043] In this invention, MIL-53(Fe) refers to a specific metal-organic framework (MOF) material belonging to the MIL-53 series. It is a crystal framework composed of a metal center and an organic ligand, where the metal center is iron and the organic ligand is terephthalic acid. MIL-53(Fe)-OH refers to functionalized MIL-53(Fe), where the metal center is iron and the organic ligand is 2-hydroxyterephthalic acid. MIL-53(Fe)-2OH refers to functionalized MIL-53(Fe), where the metal center is iron and the organic ligand is 2,5-dihydroxyterephthalic acid.

[0044] The following specific examples further illustrate the iron / carbon composite material of the present invention, its preparation method, and its application in the 5-HMF hydrogenolysis reaction.

[0045] In the following examples, all reagents used were purchased from Sinopharm Reagents.

[0046] The information of the instruments used in the embodiments is shown in the table below:

[0047] Table 1 Instrument Information Sheet

[0048]

[0049] Example 1

[0050] (1) Preparation of iron-based catalysts

[0051] 1.32 g of terephthalic acid (1,4-BDC) and 2.16 g of FeCl3·6H2O were added to 30 mL of DMF and stirred at room temperature to form a homogeneous solution. The solution was then transferred to a 100 mL stainless steel hydrothermal synthesis reactor and reacted at 150 °C for 12 hours. After cooling, the product was centrifuged, washed with deionized water, and then dried in a vacuum drying oven at 80 °C for 24 hours to obtain the iron-based MOF material: MIL-53(Fe), as a carbonization precursor.

[0052] The obtained precursor was placed in a tube furnace and heated at 5 °C / min under a N2 atmosphere. -1 The temperature was increased to 450℃ and calcined for 4 hours to obtain the iron-based catalyst Fe-C-1.

[0053] (2) Hydrogenation reaction

[0054] After grinding the catalyst, it was compressed into tablets using a tablet press, and then sieved. 0.2 g of catalyst (60-80 mesh) was placed in a quartz tube with an inner diameter of 0.7 cm. An H2 / N2 flow was first introduced, with both H2 and N2 flow rates at 20 mL / min. The catalyst was pre-reduced at 500 °C for 2 hours. A concentration of 12.6 mg / mL was prepared. -1 The 5-HMF solution, with isopropanol and water in a ratio of 4:1 (volume ratio), was pumped into the reactor using a syringe at a rate of 1 mL / h. -1 H2 was introduced at a flow rate of 20 mL / min, and the hydrogenation reaction was carried out at 280 °C and atmospheric pressure (0.1 MPa). The liquid product was collected every hour for analysis, and the reaction was carried out for a total of 8 hours.

[0055] After collection, the liquid products were analyzed offline by gas chromatography using an Agilent 7820A instrument equipped with an HP-5 (30m × 320μm × 0.25μm) capillary column and a flame ionization detector (FID). The contents of 5-HMF, 2,5-DMF, and 5-MF in the sample were calculated using an external standard calibration curve constructed based on pure compounds. 5-MF was the target product. The formulas for calculating the conversion of 5-HMF, the selectivity of 5-MF, and the selectivity of 2,5-DMF are as follows:

[0056] 5-HMF conversion rate = Molar amount of HMF consumed in the reaction / Molar amount of HMF in the feedstock

[0057] 5-MF selectivity = Molar amount of 5-MF in the product / Molar amount of HMF consumed in the reaction

[0058] 2,5-DMF selectivity = Molar amount of 2,5-DMF in the product / Molar amount of HMF consumed in the reaction

[0059] The iron-based MOF material obtained in step (1) was subjected to XRD analysis to determine its crystal structure. The detection conditions were: Cu target, Kα = 1 / 1.54056, and scan rate of 10°·min. -1 The scanning range is 5°-90°. The detection results are as follows: Figure 1 As shown, a comparison with the standard spectrum of MIL-53(Fe)-simulate reveals that the iron-based MOF material obtained in this embodiment is MIL-53(Fe).

[0060] The iron-based catalyst obtained in step (1) was subjected to XRD analysis, and the results are as follows: Figure 2 As shown, the standard card is JCPDS file 19-0629, i.e. Fe3O4. Comparing with the standard card, it can be seen that the iron-based catalyst obtained in this embodiment has diffraction peaks at 18.3°, 30.1°, 35.1°, 37.1°, 43.1°, 53.4°, 56.9° and 62.5°, corresponding to (111), (220), (311), (222), (400), (422), (511) and (440), indicating that the iron-based catalyst contains Fe3O4. The size of the catalyst is estimated to be 33 nm using the Scherrer formula.

[0061] The TEM image of the iron-based catalyst obtained in this embodiment is as follows: Figure 3 As shown in (a), the Fe3O4 nanoparticles are uniformly dispersed in the carbon layer, with a size of 10 nm-50 nm. This indicates that the MOF structure collapses during pyrolysis, with the iron clusters and organic ligands transforming into nanoparticles and the carbon matrix, respectively.

[0062] The energy dispersive X-ray (EDS) elemental spectrum of the catalyst was measured, which showed that Fe, C and O elements were uniformly distributed inside the catalyst without obvious aggregation. The content of iron(III) oxide in the catalyst was 15.17%, and the carbon content was 84.83%.

[0063] XPS measurements showed that C, O, and Fe were the main elements in the catalyst.

[0064] Based on the detection results of the liquid phase product, the conversion rate of 5-HMF as a function of time was obtained as follows: Figure 4 As shown in the figure, the selectivity of product 5-MF changes over time. Figure 5 As shown in the figure, the selectivity of product 2,5-DMF changes over time. Figure 6 As shown, the results indicate that in this embodiment, the 5-HMF conversion rate remained at 100% for 1-8 hours, the 5-MF selectivity increased continuously with reaction time and remained stable after 6 hours, the 2,5-DMF selectivity remained at 0%, and after 8 hours of reaction, the HMF conversion rate was 100%, the 5-MF selectivity was 80%, and the selectivity of the byproduct 2,5-DMF was 0.

[0065] Example 2

[0066] (1) Preparation of iron-based catalysts

[0067] 1.446 g of 2-hydroxyterephthalic acid and 2.16 g of FeCl3·6H2O were added to 30 mL of DMF and stirred at room temperature to form a homogeneous solution. The solution was then transferred to a 100 mL stainless steel hydrothermal synthesis reactor and reacted at 150 °C for 12 hours. After cooling, the product was centrifuged, washed with deionized water, and then dried in a vacuum drying oven at 80 °C for 24 hours to obtain the iron-based MOF material: MIL-53(Fe)-OH, as a carbonization precursor.

[0068] The obtained precursor was placed in a tube furnace and heated at 5 °C / min under a N2 atmosphere. -1 The temperature was increased to 450℃ and calcined for 4 hours to obtain the iron-based catalyst Fe-C-2.

[0069] The hydrogenation reaction was carried out according to the steps of Example 1.

[0070] The XRD pattern of the iron-based MOF material obtained in this embodiment is as follows: Figure 1 As shown, a comparison with the standard spectrum of MIL-53(Fe) reveals that the crystal structure of the iron-based MOF material MIL-53(Fe)-OH obtained in this embodiment is consistent with that of MIL-53(Fe).

[0071] The XRD pattern of the obtained iron-based catalyst is as follows: Figure 2 As shown in the figure, the iron-based catalyst obtained in this embodiment contains Fe3O4, and the size of the catalyst is estimated to be 38 nm using the Scherrer formula.

[0072] The TEM image of the iron-based catalyst obtained in this embodiment is as follows: Figure 3 As shown in (b), the Fe3O4 nanoparticles are uniformly dispersed in the carbon layer, and the nanoparticle size is 10nm-50nm.

[0073] EDS analysis results showed that Fe, C and O elements were uniformly distributed inside the catalyst without obvious aggregation. The content of iron oxide was 16.55%, and the carbon content was 83.45%.

[0074] XPS analysis results showed that C, O, and Fe were the main elements in the catalyst.

[0075] In this embodiment, the 5-HMF conversion rate versus time curve is as follows: Figure 4 As shown in the figure, the selectivity of product 5-MF changes over time. Figure 5 As shown in the figure, the selectivity of product 2,5-DMF changes over time. Figure 6As shown, the results indicate that the conversion rate of 5-HMF remained at 95% within 1-8 hours, the selectivity of 5-MF increased continuously with reaction time and remained stable after 6 hours, the selectivity of 2,5-DMF remained stable, and after 8 hours of reaction, the conversion rate of HMF was 95%, the selectivity of 5-MF was 52%, and the selectivity of the byproduct 2,5-DMF was 11%.

[0076] Example 3

[0077] (1) Preparation of iron-based catalysts

[0078] 1.572 g of 2,5-dihydroxyterephthalic acid and 2.16 g of FeCl3·6H2O were added to 30 mL of DMF and stirred at room temperature to form a homogeneous solution. The solution was then transferred to a 100 mL stainless steel hydrothermal synthesis reactor and reacted at 150 °C for 12 hours. After cooling, the product was centrifuged, washed with deionized water, and then dried in a vacuum drying oven at 80 °C for 24 hours to obtain the iron-based MOF material: MIL-53(Fe)-2OH, as a carbonization precursor.

[0079] The obtained precursor was placed in a tube furnace and heated at 5 °C / min under a N2 atmosphere. -1 The temperature was increased to 450℃ and calcined for 4 hours to obtain the iron-based catalyst Fe-C-3.

[0080] The hydrogenation reaction was carried out according to the steps of Example 1.

[0081] The XRD pattern of the iron-based MOF material obtained in this embodiment is as follows: Figure 1 As shown, a comparison with the standard spectrum of MIL-53(Fe) reveals that the crystal structure of the iron-based MOF material MIL-53(Fe)-2OH obtained in this embodiment is consistent with that of MIL-53(Fe).

[0082] The XRD pattern of the obtained iron-based catalyst is as follows: Figure 2 As shown in the figure, the iron-based catalyst obtained in this embodiment contains Fe3O4, and the size of the catalyst is estimated to be 26 nm using the Scherrer equation.

[0083] The TEM image of the iron-based catalyst obtained in this embodiment is as follows: Figure 3 As shown in (c), the Fe3O4 nanoparticles are uniformly dispersed in the carbon layer, and the nanoparticle size is 10nm-50nm.

[0084] EDX analysis results showed that Fe, C and O elements were uniformly distributed inside the catalyst without obvious aggregation. The content of iron oxide was 9.7% and the carbon content was 90.3%.

[0085] XPS analysis results showed that C, O, and Fe were the main elements in the catalyst.

[0086] In this embodiment, the 5-HMF conversion rate versus time curve is as follows: Figure 4 As shown in the figure, the selectivity of product 5-MF changes over time. Figure 5 As shown in the figure, the selectivity of product 2,5-DMF changes over time. Figure 6 As shown, the results indicate that the conversion rate of 5-HMF remained above 85% for 1-4 hours, and then gradually decreased. The selectivity of 5-MF increased continuously with reaction time and remained stable after 6 hours. The selectivity of 2,5-DMF decreased slowly with time and remained stable after 6 hours. After 8 hours of reaction, the conversion rate of HMF was 65%, the selectivity of 5-MF was 63%, and the selectivity of the byproduct 2,5-DMF was 21%.

[0087] Infrared detection showed that the catalysts obtained in Examples 2 and 3 contained more hydroxyl groups compared to Example 1.

[0088] Raman spectroscopy analysis revealed that the iron / carbon composite catalysts obtained in Examples 1-3 exhibited high performance at 1340 cm⁻¹. -1 (D belt) and 1600cm -1 The (G band) exhibits a waveband, the D band is related to the presence of defects, while the G band corresponds to the presence of graphite structure. The intensity ratio of the two bands, ID / IG, represents the degree of disorder in the carbon structure. The ID / IG ratios of the catalysts in Examples 1, 2, and 3 are 1.8, 2.9, and 2.83, respectively, indicating that the catalyst obtained in Example 1 has a higher degree of graphitization, fewer defects, and is more stable.

[0089] Example 4

[0090] (1) Preparation of iron-based catalysts

[0091] 1.32 g of terephthalic acid (1,4-BDC) and 2.58 g of FeCl3·6H2O were added to 30 mL of DMF and stirred at room temperature to form a homogeneous solution. The solution was then transferred to a 100 mL stainless steel hydrothermal synthesis reactor and reacted at 160 °C for 10 hours. After cooling, the product was centrifuged, washed with deionized water, and then dried in a vacuum drying oven at 80 °C for 24 hours to obtain the iron-based MOF material: MIL-53(Fe), as a carbonization precursor.

[0092] The obtained precursor was placed in a tube furnace and heated at 3°C / min under a N2 atmosphere. -1 The temperature was increased to 250℃ and calcined for 6 hours to obtain the iron-based catalyst Fe-C-4.

[0093] The hydrogenation reaction was carried out according to the steps of Example 1.

[0094] After hydrogenation, the contents of 5-HMF, 5-MF, and 2,5-DMF were measured. The results showed that in this example, the conversion rate of 5-HMF was 67%, the selectivity of 5-MF was 69%, and the selectivity of 2,5-DMF was 0.

[0095] Example 5

[0096] Example 5 is similar to Example 1, except that in step (1), the calcination temperature of the precursor is 650°C.

[0097] After hydrogenation, the contents of 5-HMF, 5-MF, and 2,5-DMF were detected. The results showed that in this example, the conversion rate of 5-HMF was 100%, the selectivity of 5-MF was 72%, and the selectivity of 2,5-DMF was 0.

[0098] Example 6

[0099] Example 6 is similar to Example 1, except that in step (1), the calcination temperature of the precursor is 850°C.

[0100] After hydrogenation, the contents of 5-HMF, 5-MF, and 2,5-DMF were detected. The results showed that in this example, the conversion rate of 5-HMF was 100%, the selectivity of 5-MF was 65%, and the selectivity of 2,5-DMF was 0.

[0101] As shown in Examples 4-6, the conversion rate increases with increasing calcination temperature, while the selectivity first increases and then decreases. This is presumably because the increased calcination temperature leads to an increase in the pore size and specific surface area of ​​the catalyst, thus increasing the HMF conversion rate and MF selectivity. However, if the calcination temperature is too high, the formation of iron(III) oxide clusters results in a decrease in both the HMF conversion rate and MF selectivity.

[0102] Example 7

[0103] Example 7 is similar to Example 1, except that the solvent for the 5-HMF solution during the hydrogenation reaction is isobutanol:water = 4:1 (volume ratio).

[0104] The results showed that the conversion rate of 5-HMF was 80%, the selectivity of 5-MF was 70%, and the selectivity of 2,5-DMF was 0.

[0105] Example 8

[0106] Example 8 is similar to Example 1, except that the solvent for the 5-HMF solution during the hydrogenation reaction is acetonitrile:water = 4:1 (volume ratio).

[0107] The results showed that the conversion rate of 5-HMF was 70%, the selectivity of 5-MF was 80%, and the selectivity of 2,5-DMF was 0.

[0108] Example 9

[0109] Example 9 is similar to Example 1, except that the solvent for the 5-HMF solution during the hydrogenation reaction is dimethyl sulfoxide:water = 4:1 (volume ratio).

[0110] The results showed that the conversion rate of 5-HMF was 80%, the selectivity of 5-MF was 40%, and the selectivity of 2,5-DMF was 0.

[0111] Example 10

[0112] Example 10 is similar to Example 1, except that during the hydrogenation reaction, the solvent of the 5-HMF solution is 1,4-dioxane:water = 4:1 (volume ratio).

[0113] The results showed that the conversion rate of 5-HMF was 60%, the selectivity of 5-MF was 70%, and the selectivity of 2,5-DMF was 0.

[0114] Example 11

[0115] (1) An iron-based catalyst was prepared according to the method in Example 1.

[0116] (2) Hydrogenation reaction

[0117] After grinding the catalyst, it was compressed into tablets using a tablet press, and then sieved. 0.2 g of catalyst (60-80 mesh) was placed in a quartz tube with an inner diameter of 0.7 cm. An H2 / N2 flow was first introduced, with H2 and N2 flow rates of 40 mL / min and 20 mL / min respectively. The catalyst was pre-reduced at 400 °C for 5 hours. A concentration of 10 mg / mL was prepared. -1 The 5-HMF solution, with isopropanol:water = 1.5:1 (volume ratio), was pumped into the reactor using a syringe at a rate of 1 mL / h. -1 H2 was introduced at a flow rate of 15.8 mL / min, and the hydrogenation reaction was carried out at 240 °C and atmospheric pressure (0.1 MPa). The liquid product was collected every hour for analysis, and the reaction was carried out for a total of 8 hours.

[0118] The results showed that the conversion rate of 5-HMF was 18% and the selectivity of 5-MF was 50%.

[0119] Example 12

[0120] (1) An iron-based catalyst was prepared according to the method in Example 1.

[0121] (2) Hydrogenation reaction

[0122] After grinding the catalyst, it was compressed into tablets using a tablet press, and then sieved. 0.2 g of catalyst (60-80 mesh) was placed in a quartz tube with an inner diameter of 0.7 cm. An H2 / N2 flow was first introduced, with both H2 and N2 flow rates at 20 mL / min. The catalyst was pre-reduced at 600 °C for 2 hours. A concentration of 15 mg / mL was prepared. -1 The 5-HMF solution, with isopropanol and water in a ratio of 2:1 (volume ratio), was pumped into the reactor using a syringe at a rate of 1 mL / h. -1 H2 was introduced at a flow rate of 24 mL / min, and the hydrogenation reaction was carried out at 320 °C and atmospheric pressure (0.1 MPa). The liquid phase product was collected every hour for analysis, and the reaction was carried out for a total of 8 hours.

[0123] The results showed that the conversion rate of 5-HMF was 90%, the selectivity of 5-MF was 70%, and the selectivity of 2,5-DMF was 0.

[0124] Example 13

[0125] Example 13 is similar to Example 1, except that the pre-reduction temperature of the catalyst during the hydrogenation reaction is 400°C.

[0126] The results showed that the conversion rate of 5-HMF was 90%, the selectivity of 5-MF was 75%, and the selectivity of 2,5-DMF was 0.

[0127] Example 14

[0128] Example 14 is similar to Example 1, except that the pre-reduction temperature of the catalyst during the hydrogenation reaction is 600°C.

[0129] The results showed that the conversion rate of 5-HMF was 80%, the selectivity of 5-MF was 62%, and the selectivity of 2,5-DMF was 0.

[0130] In summary, this invention uses iron-based MOFs as precursors, and after carbonization, yields an iron / carbon composite material. Different numbers of hydroxyl groups in the organic ligands of the raw materials result in different numbers of hydroxyl groups on the surface of the iron / carbon composite material, thus affecting the catalytic effect on the 5-HMF hydrogenolysis reaction. The catalyst obtained by this invention exhibits high stability, maintaining a high catalytic effect even within 6-8 hours of the hydrogenation reaction. When the organic ligand is terephthalic acid, the resulting iron / carbon composite material, as a catalyst, demonstrates high selectivity for the 5-MF product in the 5-HMF hydrogenolysis reaction. The catalyst obtained by this invention contains iron(III) oxide (Fe3O4), possesses magnetic properties, and is easily separated and recovered.

Claims

1. Use of an iron / carbon composite material in the hydrogenolysis reaction of 5-HMF, characterized in that, The method comprises the following steps: (1) adding a ferric salt and terephthalic acid in N,N-dimethylformamide, and forming a ferrous metal-organic framework material through a solvothermal reaction at 140-160 DEG C for 10-15 h; wherein the molar ratio of the ferric salt to terephthalic acid is (1-1.2):1, and the mass-volume ratio of the ferric salt to N,N-dimethylformamide is (2.0-3.0) g:30 mL; (2) calcining the ferrous metal-organic framework material at 400-650 DEG C for 4-6 h under an inert atmosphere to obtain a ferrous / carbon composite material; (3) a pre-reduction process: placing the ferrous / carbon composite material in a quartz tube, introducing a mixed gas of hydrogen and nitrogen, and calcining at 500 DEG C for 2 h; (4) pumping a 5-HMF solution through a syringe pump, introducing hydrogen, and performing a hydrogenation reaction at 240-320 DEG C under normal pressure to collect a product; wherein the solvent for the 5-HMF solution is a mixed solution of an organic solvent and water, the organic solvent is isopropyl alcohol, and the volume ratio of the organic solvent to water is 4:1; wherein the ferrous / carbon composite material comprises a carbon matrix and ferroferric oxide dispersed on the carbon matrix, the particle size of the ferroferric oxide is 10-50 nm, and the mass fraction of the ferroferric oxide in the ferrous / carbon composite material is 8wt%-20wt%.

2. Use according to claim 1, characterized in that, In step (1), the volume ratio of hydrogen to nitrogen in the mixed gas is (1-2):1.

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