Iron / carbon composite material, preparation method thereof and application of iron / carbon composite material in 5-HMF hydrogenolysis reaction

Abstract

The invention discloses an iron / carbon composite material and a preparation method and application in 5-HMF hydrogenolysis reaction, the iron / 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, the ferroferric oxide accounts for 8-20 wt% of the iron / carbon composite material by mass, and the particle size of the ferroferric oxide is 10-50 nm. The application in the hydrogenolysis reaction comprises the following steps: (1) a pre-reduction process: putting the iron / carbon composite material serving as a catalyst into a quartz tube, introducing a mixed gas of hydrogen and nitrogen, and calcining at 400-600 DEG C; and (2) pumping a 5-HMF solution by using an injector, introducing hydrogen, carrying out hydrogenation reaction at normal pressure, and collecting a product. The iron / carbon composite material 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 has magnetism and is easy to separate and recover.

Description

Technical Field

[0001] The invention relates to the technical field of fine chemical production, mainly to the technical field of 5-HMF hydrogenolysis reaction, and specifically to an iron / carbon composite material and a preparation method thereof and application in 5-HMF hydrogenolysis reaction. Background Art

[0002] Nowadays, the amount of fossil resources mined is increasing, and the reserves available for mining are gradually decreasing. Therefore, it is urgent to find sustainable energy to replace fossil resources. Biomass is widely regarded as the only renewable organic carbon resource on the earth, and the value-added chemicals and fuels converted from it have the potential to replace traditional petrochemical products. Converting raw materials that are easy to obtain from plants, such as glucose, fructose, and cellulose, into the platform compound 5-hydroxymethylfurfural (5-HMF) is one of the important ways for biomass catalytic conversion. 5-HMF can be converted into a variety of high-quality derivatives such as 2,5-furan dimethanol (DHMF), 2,5-dimethylfurfural (DMF), 5-methylfurfural (5-MF), etc. through hydrogenation, hydrogenolysis, or oxidation. Among them, 5-methylfurfural (5-MF) is an important fine chemical that can be used to prepare flavoring agents, potential anti-tumor agents, common organic synthesis intermediates, and perfumes in the food industry. 5-MF has multiple functional groups, such as furan rings, carbonyl groups, and double bonds, and more than 70 compounds can be synthesized. HMF has three different functional groups that can be hydrogenated, including C=O, C=C and CO, among which the hydrogenation reaction rate of C=O is faster than the other two functional groups. How to avoid the hydrogenation of the aldehyde functional group and reduce the alcohol hydroxyl group is a difficult problem. At present, most of the catalysts for catalytic hydrogenolysis of 5-HMF to 5-MF are precious metals, and a few use non-precious metal catalysts, and the reaction needs to be carried out under high pressure. The invention patent with publication number CN107353268A discloses a method for preparing 5-methylfurfural by selective hydrogenation of 5-hydroxymethylfurfural, 5-hydroxymethylfurfural, solvent, catalyst, hydrogen supply reagent are added to a high-pressure reactor, and the hydrogenation reaction is carried out at 20-300°C. 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 catalyst used is a precious metal except Co, Ni, and Cu.

[0003] Non-precious metals have the advantages of low cost and controllable performance. At present, non-precious metal catalysts used for HMF oxidation and hydrogenolysis reactions are mainly bimetallic or multimetallic catalysts. For example, the invention patent with publication number CN118292000A discloses a sulfur-doped nickel-cobalt-based electrocatalytic oxidation catalyst for 5-hydroxymethylfurfural, which can promote the electrocatalytic oxidation of 5-hydroxymethylfurfural to prepare 2,5-furandicarboxylic acid. However, the existing non-precious metal catalysts used in the hydrogenolysis reaction of 5-HMF are mainly bimetallic or multimetallic catalysts, with complex preparation processes and high costs, which are not conducive to industrial application. The catalytic effect and stability of single non-precious metal catalysts need to be strengthened. After the hydrogenolysis reaction, the existing catalysts need to be separated and recovered, which increases the cost and is not conducive to industrial promotion. Summary of the invention

[0004] The present invention is to avoid the deficiencies of the above-mentioned prior art, and provides an iron / carbon composite material and a preparation method thereof and an application thereof in a 5-HMF hydrogenolysis reaction, wherein an iron-based MOF-derived carbon material is prepared as a catalyst for a catalytic hydrogenation reaction of 5-HMF, the hydrogenation reaction is completed under normal pressure, 5-MF is synthesized, and the selectivity of 5-MF is adjusted by regulating the side chain groups of the catalyst. The catalyst has high stability and is magnetic, which is conducive to separating the catalyst and the product and is easy to recover.

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

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

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

[0008] The present invention also provides a method for preparing an iron / carbon composite material, characterized in that it comprises the following steps:

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

[0010] (2) calcining the iron-based metal organic framework material 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 solvent thermal reaction is 140-160° C. The time of the solvent thermal reaction is 10-15 hours.

[0015] Preferably, in the above preparation method, the calcination temperature is 250-850°C, preferably 400-650°C, the calcination time is 4-6h, and the heating rate is 3-5°C / 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 5-HMF hydrogenolysis reaction, characterized in that the catalyst comprises the above-mentioned iron / carbon composite material.

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

[0019] The present invention also provides an application of an iron / carbon composite material in a 5-HMF hydrogenolysis reaction, characterized in that it comprises the following steps:

[0020] (1) Pre-reduction process: placing the iron / carbon composite material according to claim 1 into a quartz tube, introducing a mixture of hydrogen and nitrogen, and calcining at 400-600° C.;

[0021] (2) Pump 5-HMF solution into the solution using a syringe, introduce hydrogen, 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 for the 5-HMF solution is a mixture of an 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 application, the organic solvent is selected from isopropanol, isobutanol, acetonitrile, dimethyl sulfoxide or 1,4-dioxane, preferably isopropanol or isobutanol.

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

[0026] Preferably, in the above application, the temperature of the hydrogenation reaction is 240-320°C, preferably 260-320°C, more preferably 260-300°C.

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

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

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

[0030] The periodic network structure formed by metal ions and organic ligands in the metal organic framework (MOF) structure is conducive to preventing the aggregation of metal or metal oxide nanoparticles during pyrolysis, and is conducive to the orderly dispersion of metals. Iron, as the most abundant transition element in the earth's crust, is cheap and easy to obtain, and is the most potential non-precious metal element for 5-HMF hydrogenolysis reaction. Compared with the existing technology, the beneficial effects of the present invention are embodied in the following aspects: (1) The present invention uses iron-based MOF as a precursor to prepare an iron / carbon composite material, which is used as a catalyst for the hydrogenolysis reaction of 5-HMF, and has a significant catalytic effect. The conversion rate of 5-HMF can reach up to 100%, and the selectivity of 5-MF can reach up to 80%; (2) The catalyst of the present invention has good stability, and the hydrogenolysis reaction is carried out under normal pressure, which is safer; (3) The catalyst of the present invention has magnetic properties and is easy to separate and recover; (4) The present invention reveals the influence of the hydroxyl functional group on the surface of the iron / carbon composite material on the hydrogenolysis reaction of 5-HMF, which provides ideas for optimizing the catalyst structure in the future. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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

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

[0036] Figure 4 The graph is a graph showing the change in 5-HMF conversion over time during the hydrogenation reaction of Example 1, Example 2, and Example 3.

[0037] Figure 5 The selectivity of the product 5-MF during the hydrogenation reaction of Example 1, Example 2, and Example 3 varies with time.

[0038] Figure 6 This is a curve chart showing the change in selectivity of the product 2,5-DMF over time during the hydrogenation reaction of Example 1, Example 2, and Example 3. DETAILED DESCRIPTION

[0039] In view of the fact that the catalytic effect and stability of existing single non-precious metal catalysts need to be improved, the present invention uses iron-based MOF as a precursor to prepare a catalyst suitable for 5-HMF hydrogenolysis reaction, 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 comprises the following steps: adding 1,4-BDC (1.32 g) and FeCl3·6H2O (2.16 g) to 30 mL of DMF, and stirring the obtained solution at room temperature to form a uniform solution. 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 is naturally cooled, it is centrifuged, and then the obtained product powder is soaked in deionized water (250 mL) overnight, centrifuged again, and finally the sample is placed in a vacuum drying oven at 80°C for 24 hours. The prepared precursor is precipitated in a tubular furnace under a N2 atmosphere at 5°C·min -1 The mixture was calcined at 450 °C for 4 h at a heating rate of 100 °C 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 hydrogenolysis reaction of 5-HMF comprises the following steps: the catalyst is first ground in a mortar for ten minutes, then loaded into a tableting mold and tableted on a tablet press, and then granulated with 60-mesh and 80-mesh screens. 0.2 g of the catalyst falling on the 60-80 mesh screen is used for the reaction, and the catalyst is loaded into a quartz tube with an inner diameter of 0.7 cm, and the concentration is prepared to be 12.6 mg ml -1 The 5-HMF solution was injected into the reactor by syringe (1 ml·h -1), before the reaction, the catalyst was pre-reduced with H2 / N2 flow at 500°C for 2 hours, and then reacted under H2.

[0042] The present invention investigates the influence of side chain groups on the use of MOF-derived Fe / C composite materials to catalyze the hydrogenolysis reaction of 5-HMF. The organic ligands of the synthesized catalysts are terephthalic acid, 2-hydroxyterephthalic acid and 2,5-dihydroxyterephthalic acid, respectively. The number of hydroxyl groups in the side chain groups of the three ligands is different, which results in different numbers of hydroxyl groups on the surface of the carbon material, resulting in the adsorption energy of HMF and 5-MF increasing with the increase of the number of hydroxyl groups, 5-MF is not easy to desorb and further hydrogenolyze, thereby producing differences in the selectivity of the product 5-MF.

[0043] Wherein, the MIL-53(Fe) described in the present invention refers to: a specific Metal-Organic Framework (MOF) material, belonging to the MIL-53 series. A crystal framework composed of a metal center and an organic ligand, the metal center is iron, and the organic ligand is terephthalic acid. MIL-53(Fe)-OH refers to functionalized MIL-53(Fe), the metal center is iron, and the organic ligand is 2-hydroxyterephthalic acid. MIL-53(Fe)-2OH refers to functionalized MIL-53(Fe), the metal center is iron, and the organic ligand is 2,5-dihydroxyterephthalic acid.

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

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

[0046] The information of the instruments used in the examples is shown in the following table:

[0047] Table 1 Instrument information

[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 uniform solution. Subsequently, it was transferred to a 100 mL stainless steel hydrothermal synthesis reactor and reacted at 150 ° C for 12 hours. The product was cooled and centrifuged. After washing with deionized water, it was placed in a vacuum drying oven at 80 ° C for 24 hours to obtain an 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 -1 The temperature was raised to 450°C at a rate of 1.5 °C and calcined for 4 h to obtain the iron-based catalyst Fe-C-1.

[0053] (2) Hydrogenation reaction

[0054] After the catalyst was ground, it was pressed into tablets using a tablet press and then screened using a sieve. 0.2 g of the catalyst with a mesh size of 60-80 was taken and loaded into a quartz tube with an inner diameter of 0.7 cm. H2 / N2 flow was first introduced, and the flow rates of H2 and N2 were both 20 mL / min. The catalyst was pre-reduced at 500°C for 2 hours. The prepared concentration was 12.6 mg·mL -1 The 5-HMF solution was prepared by injecting isopropanol into the reactor at a speed of 1 mL·h. -1 , introduce H2 at a flow rate of 20 mL / min, and carry out hydrogenation reaction at 280°C and normal pressure conditions (0.1 MPa). The liquid products are collected every hour for detection, and the reaction lasts for 8 hours in total.

[0055] After the liquid products were collected, they were analyzed by offline 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. Among them, 5-MF is the target product, and the calculation formulas for 5-HMF conversion, 5-MF selectivity, and 2,5-DMF selectivity are:

[0056] 5-HMF conversion rate = molar amount of HMF consumed in the reaction / molar amount of HMF in the raw material

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

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

[0059] The iron-based MOF material obtained in step (1) was subjected to XRD detection to analyze the crystal structure of the sample. The detection conditions were: Cu target, Kα=1 / 1.54056, scanning speed of 10°·min -1 , the scanning range is 5°-90°. The test results are as follows Figure 1 As shown, compared with the MIL-53(Fe)-simulate standard spectrum, it can be seen that the iron-based MOF material obtained in this example is MIL-53(Fe).

[0060] The iron-based catalyst obtained in step (1) was subjected to XRD detection, and the results were as follows: Figure 2 As shown, the standard card is JCPDS file 19-0629, i.e., Fe3O4. Compared with the standard card, 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 example is as follows: Figure 3 As shown in (a), the Fe3O4 nanoparticles are evenly dispersed in the carbon layer, and the size of the nanoparticles is 10nm-50nm. This indicates that the structure of MOF collapses during pyrolysis, as the iron clusters and organic ligands are converted into nanoparticles and carbon matrices, respectively.

[0062] The energy dispersive X-ray (EDS) elemental spectrum of the catalyst shows that Fe, C and O elements are evenly distributed inside the catalyst without obvious aggregation. The content of ferrosoferric oxide in the catalyst is 15.17%, and the content of carbon is 84.83%.

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

[0064] According to the detection results of the liquid phase product, the 5-HMF conversion rate change curve over time is obtained as follows: Figure 4 As shown, the selectivity curve of the product 5-MF changes with time is as follows Figure 5 As shown, the selectivity curve of the product 2,5-DMF changes with time is as follows Figure 6 As shown, the results show that in this embodiment, the 5-HMF conversion rate is maintained at 100% within 1-8 hours, the 5-MF selectivity increases continuously with the reaction time, remains stable after 6 hours, and the 2,5-DMF selectivity is always 0%. After 8 hours of reaction, the HMF conversion rate is 100%, the 5-MF selectivity is 80%, and the selectivity of the by-product 2,5-DMF is 0.

[0065] Example 2

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

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

[0068] The obtained precursor was placed in a tube furnace and heated at 5 °C min -1 The temperature was raised to 450°C at a rate of 1.5°C and calcined for 4 hours to obtain the iron-based catalyst Fe-C-2.

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

[0070] The XRD spectrum of the iron-based MOF material obtained in this example is as follows Figure 1 As shown, compared with the standard spectrum of MIL-53(Fe), it can be seen that the crystal structure of the iron-based MOF material MIL-53(Fe)-OH obtained in this example is consistent with MIL-53(Fe).

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

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

[0073] The EDS test results show that in the catalyst, Fe, C and O elements are evenly distributed inside the catalyst without obvious aggregation. The content of ferrosoferric oxide in the catalyst is 16.55%, and the content of carbon is 83.45%.

[0074] XPS test results show that C, O and Fe are the main elements in the catalyst.

[0075] In this embodiment, the 5-HMF conversion rate changes with time as shown in the following figure: Figure 4 As shown, the selectivity curve of the product 5-MF changes with time is as follows Figure 5 As shown, the selectivity curve of the product 2,5-DMF changes with time is as follows Figure 6As shown, the results show that the 5-HMF conversion rate is maintained at 95% within 1-8 hours, the 5-MF selectivity increases continuously with the reaction time and remains stable after 6 hours, and the 2,5-DMF selectivity remains stable. After 8 hours of reaction, the HMF conversion rate is 95%, the 5-MF selectivity is 52%, and the selectivity of the by-product 2,5-DMF is 11%.

[0076] Example 3

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

[0078] 1.572 g 2,5-dihydroxyterephthalic acid and 2.16 g FeCl3·6H2O were added to 30 mL DMF and stirred at room temperature to form a uniform solution. Subsequently, it was transferred to a 100 mL stainless steel hydrothermal synthesis reactor and reacted at 150 ° C for 12 hours. The product was cooled and centrifuged. The obtained product was washed with deionized water and placed in a vacuum drying oven at 80 ° C for 24 hours to obtain an 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 -1 The temperature was raised to 450°C at a rate of 1.5 °C and calcined for 4 h to obtain the iron-based catalyst Fe-C-3.

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

[0081] The XRD spectrum of the iron-based MOF material obtained in this example is as follows Figure 1 As shown, compared with the standard spectrum of MIL-53(Fe), it can be seen that the crystal structure of the iron-based MOF material MIL-53(Fe)-2OH obtained in this example is consistent with MIL-53(Fe).

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

[0083] The TEM image of the iron-based catalyst obtained in this example is as follows: Figure 3 As shown in (c), it can be seen from the figure that Fe3O4 nanoparticles are evenly dispersed in the carbon layer, and the size of the nanoparticles is 10nm-50nm.

[0084] The EDX test results show that in the catalyst, Fe, C and O elements are evenly distributed inside the catalyst without obvious aggregation. The content of ferrosoferric oxide in the catalyst is 9.7%, and the content of carbon is 90.3%.

[0085] XPS test results show that C, O and Fe are the main elements in the catalyst.

[0086] In this embodiment, the 5-HMF conversion rate changes with time as shown in the following figure: Figure 4 As shown, the selectivity curve of the product 5-MF changes with time is as follows Figure 5 As shown, the selectivity curve of the product 2,5-DMF changes with time is as follows Figure 6 As shown, the results show that the 5-HMF conversion rate is maintained at more than 85% within 1-4 hours, and then gradually decreases. The 5-MF selectivity increases continuously with the reaction time and remains stable after 6 hours. The 2,5-DMF selectivity decreases slowly with time and remains stable after 6 hours. After 8 hours of reaction, the HMF conversion rate is 65%, the 5-MF selectivity is 63%, and the selectivity of the by-product 2,5-DMF is 21%.

[0087] Infrared detection shows that, compared with Example 1, the catalysts obtained in Example 2 and Example 3 contain more hydroxyl groups.

[0088] Raman spectroscopy showed that the iron / carbon composite catalysts obtained in Examples 1 to 3 had a Raman spectroscopy of 1340 cm -1 (D band) and 1600cm -1 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 of the carbon structure. The ID / IG of the catalysts of Example 1, Example 2, and Example 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 a more stable material.

[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 uniform solution. Subsequently, it was transferred to a 100 mL stainless steel hydrothermal synthesis reactor and reacted at 160 ° C for 10 hours. The product was cooled and centrifuged. After washing with deionized water, it was placed in a vacuum drying oven at 80 ° C for 24 hours to obtain an 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 -1 The temperature was raised to 250°C at a rate of 1.5°C and calcined for 6 hours to obtain the iron-based catalyst Fe-C-4.

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

[0094] After the hydrogenation reaction, the contents of 5-HMF, 5-MF and 2,5-DMF were detected. The results showed that in this embodiment, 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 the hydrogenation reaction, the contents of 5-HMF, 5-MF and 2,5-DMF were detected. The results showed that in this embodiment, 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 the hydrogenation reaction, the contents of 5-HMF, 5-MF and 2,5-DMF were detected. The results showed that in this embodiment, 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] It can be seen from Examples 4 to 6 that as the calcination temperature increases, the conversion rate increases, and the selectivity first increases and then decreases. It is speculated that as the calcination temperature increases, the pore size and specific surface area of ​​the catalyst increase, which increases the HMF conversion rate and MF selectivity. If the calcination temperature is too high, the ferroferric oxide clusters, resulting in a decrease in the HMF conversion rate and MF selectivity.

[0102] Example 7

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

[0104] The results showed that the conversion 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 during the hydrogenation reaction, the solvent of the 5-HMF solution is acetonitrile: water = 4:1 (volume ratio).

[0107] The results showed that the conversion 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 during the hydrogenation reaction, the solvent of the 5-HMF solution is dimethyl sulfoxide: water = 4:1 (volume ratio).

[0110] The results showed that the conversion 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 of 5-HMF was 60%, the selectivity of 5-MF was 70%, and the selectivity of 2,5-DMF was 0.

[0114] Embodiment 11

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

[0116] (2) Hydrogenation reaction

[0117] After the catalyst was ground, it was pressed into tablets using a tablet press and then screened using a sieve. 0.2 g of the catalyst with a mesh size of 60-80 was taken and loaded into a quartz tube with an inner diameter of 0.7 cm. H2 / N2 flow was first introduced, with the flow rates of H2 and N2 being 40 mL / min and 20 mL / min respectively. The catalyst was pre-reduced at 400°C for 5 hours. The prepared concentration was 10 mg·mL -1 The 5-HMF solution was prepared by injecting isopropanol into the reactor at a speed of 1 mL·h. -1 , introduce H2 at a flow rate of 15.8 mL / min, and carry out hydrogenation reaction at 240°C and normal pressure (0.1 MPa). The liquid products are collected every hour for detection, and the reaction lasts for 8 hours in total.

[0118] The results showed that the conversion 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 of Example 1.

[0121] (2) Hydrogenation reaction

[0122] After the catalyst is ground, it is pressed into tablets using a tablet press, and then screened using a sieve. 0.2 g of the catalyst with a mesh size of 60-80 is taken and loaded into a quartz tube with an inner diameter of 0.7 cm. H2 / N2 flow is first introduced, and the flow rates of H2 and N2 are both 20 mL / min. The catalyst is pre-reduced at 600°C for 2 hours. The prepared concentration is 15 mg·mL -1 The 5-HMF solution was prepared by injecting isopropanol into the reactor at a speed of 1 mL·h. -1 , introduce H2 at a flow rate of 24 mL / min, and carry out hydrogenation reaction at 320°C and normal pressure (0.1 MPa). The liquid products are collected every hour for detection, and the reaction lasts for 8 hours in total.

[0123] The results showed that the conversion 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 during the hydrogenation reaction, the pre-reduction temperature of the catalyst is 400°C.

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

[0127] Embodiment 14

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

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

[0130] In summary, the present invention uses iron-based MOF as a precursor, and obtains an iron / carbon composite material after carbonization. The number of hydroxyl groups of the raw material organic ligands is different, resulting in different numbers of hydroxyl groups on the surface of the iron / carbon composite material, thereby producing differences in the catalytic effect of the 5-HMF hydrogenolysis reaction. The catalyst obtained by the present invention has high stability and can still maintain a high catalytic effect within 6-8 hours of the hydrogenation reaction. When the organic ligand is terephthalic acid, the obtained iron / carbon composite material is used as a catalyst, and the 5-MF product selectivity of the 5-HMF hydrogenolysis reaction is high. The catalyst obtained by the present invention contains ferrosoferric oxide, has magnetic properties, and is easy to separate and recycle.

Claims

1. An iron / carbon composite material, characterized in that The invention comprises a carbon matrix and ferroferric oxide dispersed on the carbon matrix. The particle size of the ferroferric oxide is 10-50nm, and the mass fraction of the ferroferric oxide in the iron / carbon composite material is 8wt%-20wt%.

2. A method for preparing the iron / carbon composite material according to claim 1, characterized in that: The steps include: (1) adding trivalent iron salt and organic ligand to N,N-dimethylformamide to form an iron-based metal organic framework material after solvothermal reaction; (2) calcining the iron-based metal organic framework material under an inert atmosphere to obtain an iron / carbon composite material.

3. The preparation method according to claim 2, characterized in that: The organic ligand is selected from terephthalic acid, 2-hydroxyterephthalic acid or 2,5-dihydroxyterephthalic acid.

4. The preparation method according to claim 2, characterized in that: The molar ratio of the iron salt to the organic ligand is (1-1.2):

1.

5. The preparation method according to claim 2, characterized in that: The temperature of the dissolution heat reaction is 140-160°C.

6. The preparation method according to claim 2, characterized in that: The calcination temperature is 250-850°C.

7. Application of an iron / carbon composite material in 5-HMF hydrogenolysis reaction, characterized in that: The steps include: (1) Pre-reduction process: placing the iron / carbon composite material according to claim 1 into a quartz tube, introducing a mixture of hydrogen and nitrogen, and calcining at 400-600° C.; (2) Pump 5-HMF solution into the solution using a syringe, introduce hydrogen, carry out hydrogenation reaction under normal pressure, and collect the product.

8. The use according to claim 7, characterized in that: In step (1), the volume ratio of hydrogen to nitrogen in the mixed gas is (1-2):

1.

9. The use according to claim 7, characterized in that: In step (2), the solvent used for the 5-HMF solution is a mixture of an organic solvent and water, the volume ratio of the organic solvent to water is (1.5-4):1, and the organic solvent is selected from isopropanol, isobutanol, acetonitrile, dimethyl sulfoxide or 1,4-dioxane.

10. The use according to claim 7, characterized in that: The temperature of the hydrogenation reaction is 240-320°C.

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