阅读说明：本技术 一种催化加氢5-羟甲基糠醛制备2,5-二甲基呋喃的方法 (Method for preparing 2,5-dimethylfuran by catalytic hydrogenation of 5-hydroxymethylfurfural ) 是由 周锦霞 吕洋 毛璟博 李慎敏 尹静梅 于 2021-01-05 设计创作，主要内容包括：本发明涉及一种催化加氢5-羟甲基糠醛制备2,5-二甲基呋喃的方法,即5-羟甲基糠醛在NiFe与还原氧化石墨烯复合材料催化剂的作用下选择性加氢反应,生成2,5-二甲基呋喃。NiFe/rGO催化剂使用前无需经过高温预还原处理,在200℃和2MPa氢气压力的条件下反应3h,5-羟甲基糠醛的转化率可达100％,2,5-二甲基呋喃的收率和选择性可达97％。无需还原预处理的NiFe/rGO催化剂比Ni/rGO、Fe/rGO催化剂以及NiFe/Al-2O-3、NiFe/HY、NiFe/SiO-2催化剂具有更高的催化活性和选择性,比Pt、Pd等贵金属类催化剂廉价,具有工业应用价值。(The invention relates to a method for preparing 2,5-dimethylfuran by catalytic hydrogenation of 5-hydroxymethylfurfural, namely, the 5-hydroxymethylfurfural is subjected to selective hydrogenation reaction under the action of a NiFe and reduced graphene oxide composite catalyst to generate the 2, 5-dimethylfuran. The NiFe/rGO catalyst does not need high-temperature pre-reduction treatment before use and has hydrogen pressure of 2MPa at 200 DEG CThe conversion rate of the reaction for 3h and 5-hydroxymethylfurfural can reach 100 percent under the condition, and the yield and the selectivity of the 2,5-dimethylfuran can reach 97 percent. NiFe/rGO catalyst ratios Ni/rGO, Fe/rGO and NiFe/Al without reduction pretreatment 2 O 3 、NiFe/HY、NiFe/SiO 2 The catalyst has higher catalytic activity and selectivity, is cheaper than noble metal catalysts such as Pt, Pd and the like, and has industrial application value.)

1. A method for preparing 2,5-dimethylfuran by catalytic hydrogenation of 5-hydroxymethylfurfural is characterized by comprising the following steps: taking ethanol as a solvent, reacting 5-hydroxymethylfurfural with H under the action of a NiFe/rGO catalyst₂And (3) carrying out reaction, wherein the amount of the catalyst accounts for 5-15% of the mass of the 5-hydroxymethylfurfural raw material, the reaction temperature is 180-220 ℃, the hydrogen pressure is 1-4 MPa, and the reaction time is 1-3 h, so that 2,5-dimethylfuran is obtained.

2. The method for preparing 2,5-dimethylfuran by catalytic hydrogenation of 5-hydroxymethylfurfural according to claim 1, wherein the reaction temperature is 200 ℃ and the hydrogen pressure is 2 MPa.

3. A catalyst used in the method for preparing 2,5-dimethylfuran by catalytic hydrogenation of 5-hydroxymethylfurfural according to claim 1, wherein the NiFe/rGO catalyst is prepared by a dip-roasting method, comprising the following steps:

(1) preparing a graphene carrier: 230mL of concentrated sulfuric acid and 5.0g of NaNO are taken₃Adding 10g of natural flake graphite powder with stirring, adding 30g of KMnO after stirring for 2.5h₄Transferring the mixture into a 35 ℃ constant temperature water bath for reaction for 2H, adding 460mL of deionized water, stirring the mixture in an oil bath at 98 ℃ for 15min, finally adding 1.4L of deionized water to stop the reaction, and simultaneously adding 25mL of 30% H₂O₂Cooling to room temperature, adding deionized water, centrifugally washing to be neutral to obtain paste graphene oxide GO, and measuring the dry basis content to be 1 wt%; dispersing 100g of GO paste prepared by the method in 1000mL of deionized water, carrying out ultrasonic treatment for 30min, standing, aging, adding 25mL of 30% ammonia water and 6mL of 80% hydrazine hydrate, refluxing in an oil bath at 95 ℃ for 3h, adding 4mL of 80% hydrazine hydrate, reacting for 30min, adding a 4% hydrochloric acid solution, carrying out suction filtration while hot, and carrying out freeze drying to obtain an rGO carrier for later use;

(2) preparation of salt solution: taking Ni (NO) respectively₃)₂·6H₂O andFe(NO₃)₃·9H₂dissolving O in 0.85mL of deionized water to prepare a salt solution;

(3) dipping: placing the prepared salt solution in the step (2) into a beaker, adding 0.2mL of absolute ethyl alcohol, then adding 100mg of the rGO carrier in the step (1), continuously stirring by using a glass rod, and placing the sample at room temperature for standing for 3 hours;

(4) and (3) drying: placing the sample after standing in the step (3) in a vacuum drying oven for drying at 50 ℃ for 12h, and grinding the sample into a powdery sample by using an agate mortar;

(5) roasting: and (3) putting the powdery sample prepared in the step (4) into a quartz tube, putting the quartz tube into a tube furnace, raising the temperature from room temperature to 500 ℃ by a program of 10 ℃/min in the nitrogen atmosphere, roasting at the constant temperature of 500 ℃ for 2h, taking out the sample when the temperature is reduced to room temperature, and sealing and storing.

4. The catalyst used in the method for preparing 2,5-dimethylfuran by catalytic hydrogenation of 5-hydroxymethylfurfural according to claim 3, wherein Ni (NO) is added in the step (2)₃)₂·6H₂O and Fe (NO)₃)₃·9H₂And in the case of O salt solution, the molar ratio of Ni to Fe is 1: 0.1-1: 1, and the total mole of Ni and Fe supported by each gram of rGO carrier is 1-2 mmol/g.

5. The catalyst used in the method for preparing 2,5-dimethylfuran by catalytic hydrogenation of 5-hydroxymethylfurfural according to claim 3, wherein Ni (NO) is added in the step (2)₃)₂·6H₂O and Fe (NO)₃)₃·9H₂And when the O salt solution is used, the molar ratio of Ni to Fe is 1:0.2, and each gram of rGO carrier carries 1mmol of Ni and 0.2mmol of Fe.

Technical Field

The invention relates to the field of preparation of 2,5-dimethylfuran, and in particular relates to a method for preparing 2,5-dimethylfuran by catalytic hydrogenation of 5-hydroxymethylfurfural.

Background

At present, the problems of greenhouse effect, air pollution and the like caused by the increasingly exhausted fossil resources and large-scale use of the fossil resources become the focus of world attention. Therefore, the development of green and efficient renewable energy sources has become a hot spot of future scientific research. The biomass energy is different from novel energy sources such as wind energy, water energy, tide, nuclear energy and the like, is the only renewable energy source which can continuously supply the petroleum to human hydrocarbon compounds, has wide sources and accords with the concept of green chemical development in the using process. The biomass resources are effectively integrated and utilized to meet the energy demand of the future society, and the biomass energy resource integration method is an important link for promoting the green and sustainable development of energy in China.

5-hydroxymethylfurfural (5-hydroxymethylfurfurral, 5-HMF) is an important platform compound generated by further dehydration of sugars from hydrolysis of cellulose, which is a main component of biomass. The compound has active chemical properties, can prepare a series of downstream derivatives with high added values through various reactions, and is an important fine chemical raw material. Under the action of a catalyst, the 5-HMF can obtain 2,5-dimethylfuran (2,5-dimethylfuran, 2,5-DMF) through hydrodeoxygenation reaction. 2,5-DMF is a novel liquid biofuel, has higher energy density, higher octane number and nonvolatile property compared with bioethanol, and is convenient to store and transport because of being insoluble with water. The above characteristics make 2,5-DMF an excellent choice for liquid fuels. Meanwhile, 2,5-DMF can also be used as a chemical solvent or a reaction raw material.

Currently, the catalysts used in the art include primarily noble metal catalysts (Ru/C, Pd/C, Pt/rGO) and non-noble metal catalysts, such as cobalt-based catalysts (Co/rGO, Co/CoO)_x) Nickel-based catalyst (Ni/Al)₂O₃、Ni/Co₃O₄B), copper-based catalyst (Cu/ZrO)₂Cu-PMO), and the like. Albeit with the purpose of eyeSome precious metal catalysts can achieve better catalytic effect, but some researchers focus on non-precious metal catalysts due to the defects of high price, limited large-scale use and the like. Hansen T S, Barta K, Anastas P T, et al, one-pot reduction of 5-hydroxymethylfurral via hydrogen transfer from supercritical methanol [ J]Green Chemistry,2012,14(9):2457-2461 reaction with methanol as hydrogen source and reaction medium and Cu-PMO (porous metal oxide) as catalyst at 260 ℃ for 3h with HMF conversion of 84%. The reaction conditions are harsh, the reaction temperature is too high, side reactions are easy to be promoted to occur, and the DMF selectivity is not high. Kong x., Zheng r., Zhu y., Ding g., Zhu Y.&Li Y.W.Rational design of Ni-based catalysts derived from hydrotalcite for selective hydrogenation of 5-hydroxymethylfurfural[J]Green Chemistry,2015,17(4),2504-2514 Ni/Al was prepared by coprecipitation₂O₃Catalyst, dioxane as reaction solvent, 1.2MPa H at 180 deg.c₂The conversion rate of HMF can reach 100 percent and the selectivity of DMF reaches 91.5 percent after 4 hours under the pressure. The reaction conditions are mild, but Ni is gradually oxidized and aggregated in the process of repeated use, so that the activity of the catalyst is suddenly reduced. Li D, Liu Q, Zhu C, et al.Selective hydrogenesis of 5-hydroxymethylenefurfuel to 2,5-dimethylfuran over Co₃O₄,catalyst by controlled reduction[J]Journal of Energy Chemistry,2019,30,34-41 Co treatment by pre-reduction at 400 ℃₃O₄To obtain partially reduced Co/CoO_xCatalyst, H at 170 ℃, 12H and 1MPa₂The yield of DMF was 83.3% under pressure, but during recycling the metal accumulated and the catalyst lost its original structure, resulting in catalyst deactivation. In addition, the non-noble metal catalysts reported in the literature usually need reduction pretreatment before being put into a reaction system, the pretreatment of reduction not only complicates the catalyst preparation and maintenance process and increases energy consumption, but also some reduced catalysts may lose activity due to oxidation.

Disclosure of Invention

In order to overcome the defects and shortcomings of the prior art, the invention provides a method for preparing 2,5-dimethylfuran by catalytic hydrogenation of 5-hydroxymethylfurfural.

The graphene is a polycyclic large aromatic molecule, the planar structure contains rich pi-electrons, and the graphene has a good conductive characteristic, so that the graphene serving as a carrier not only can provide a large specific surface area, but also can form a strong electron synergistic effect with active components such as loaded metal, metal oxide and the like. The graphene is introduced into the catalyst, and not only plays a role of a carrier, but also can modulate the electronic characteristics of the metal active component, so that the excellent catalytic performance is generated. Graphene and Co₃The strong electron synergy between Fe can protect Co₃Fe is not oxidized and corroded. As a non-noble metal catalyst, Co₃Fe-RGO has strong tolerance to alkali liquor when used in Oxygen Reduction Reaction (ORR). The electron transfer between RuO and rGO leads the RuO nano particles to be in an electron-rich state, so that the catalyst has strong catalytic capability.

The invention has the following inventive concept: the prepared catalyst does not need high-temperature pre-reduction treatment and can be used for the reaction of preparing 2,5-dimethylfuran by catalyzing and hydrogenating 5-hydroxymethylfurfural by taking cheap transition metal Ni as a hydrogenation active component, taking metal Fe as an auxiliary agent and reducing graphene oxide (rGO) as a carrier. The catalyst reacts in ethanol solution under the conditions of 2MPa of hydrogen pressure and 200 ℃ for 3 hours, HMF can be completely converted, and the yield of DMF is 97%. The introduction of Fe into Ni can significantly improve the reaction activity and the selectivity of the product, and simultaneously, the graphene with a two-dimensional plane structure not only plays a role in dispersing and loading NiFe active components, but also further enhances the catalytic function through the electronic synergistic effect of NiFe and graphene. The synthesized catalyst does not need reduction pretreatment, generates higher catalytic activity and product selectivity under mild conditions, and provides a high-efficiency catalyst for preparing 2,5-dimethylfuran by selective hydrogenation of 5-hydroxymethylfurfural.

The purpose of the invention is realized by the following technical scheme:

a method for preparing 2,5-dimethylfuran by catalytic hydrogenation of 5-hydroxymethylfurfural comprises the following steps: taking ethanol as a solvent, reacting 5-hydroxymethylfurfural with H under the action of a NiFe/rGO catalyst₂And (3) carrying out reaction, wherein the amount of the catalyst accounts for 5-15% of the mass of the 5-hydroxymethylfurfural raw material, the reaction temperature is 180-220 ℃, the hydrogen pressure is 1-4 MPa, and the reaction time is 1-3 h, so that 2,5-dimethylfuran is obtained.

Further, the preferable hydrogenation reaction temperature of 5-hydroxymethylfurfural is 200 ℃ and the hydrogen pressure is 2 MPa.

A catalyst used in a method for preparing 2,5-dimethylfuran by catalytic hydrogenation of 5-hydroxymethylfurfural, wherein the NiFe/rGO catalyst is prepared by adopting a dipping-roasting method and comprises the following steps:

(1) preparing a graphene carrier: 230mL of concentrated sulfuric acid and 5.0g of NaNO are taken₃Adding 10g of natural flake graphite powder with stirring, adding 30g of KMnO after stirring for 2.5h₄Transferring the mixture into a 35 ℃ constant temperature water bath for reaction for 2H, adding 460mL of deionized water, stirring the mixture in an oil bath at 98 ℃ for 15min, finally adding 1.4L of deionized water to stop the reaction, and simultaneously adding 25mL of 30% H₂O₂Cooling to room temperature, adding deionized water, centrifuging and washing to neutrality to obtain paste Graphene Oxide (GO), and measuring the dry basis content of the paste Graphene Oxide (GO) to be 1 wt%; and (2) dispersing 100g of GO paste prepared by the method in 1000mL of deionized water, carrying out ultrasonic treatment for 30min, standing, aging, adding 25mL of 30% ammonia water and 6mL of 80% hydrazine hydrate, refluxing in an oil bath at 95 ℃ for 3h, adding 4mL of 80% hydrazine hydrate, reacting for 30min, adding a 4% hydrochloric acid solution, carrying out suction filtration while hot, and carrying out freeze drying to obtain a rGO carrier for later use.

(2) Preparation of salt solution: taking Ni (NO) respectively₃)₂·6H₂O and Fe (NO)₃)₃·9H₂Dissolving O in 0.85mL of deionized water to prepare a salt solution;

(3) dipping: placing the prepared salt solution in the step (2) into a beaker, adding 0.2mL of absolute ethyl alcohol, then adding 100mg of the rGO carrier in the step (1), continuously stirring by using a glass rod, and placing the sample at room temperature for standing for 3 hours;

(4) and (3) drying: placing the sample after standing in the step (3) in a vacuum drying oven for drying at 50 ℃ for 12h, and grinding the sample into a powdery sample by using an agate mortar;

(5) roasting: putting the powdery sample prepared in the step (4) into a quartz tube, putting the quartz tube into a tube furnace, raising the temperature from room temperature to 500 ℃ by a program of 10 ℃/min in the nitrogen atmosphere, roasting the quartz tube at the constant temperature of 500 ℃ for 2 hours, taking out the sample when the temperature is reduced to the room temperature, and sealing and storing the sample;

further, configuring Ni (NO) in the step (2)₃)₂·6H₂O and Fe (NO)₃)₃·9H₂When in O salt solution, the molar ratio of Ni to Fe is 1: 0.1-1: 1, and the total molar ratio of Ni and Fe supported by each gram of rGO carrier is as follows: 1-2 mmol/g, preferably 1:0.2, and each gram of rGO carrier carries 1mmol of Ni and 0.2mmol of Fe.

Compared with the prior art, the invention has the beneficial effects that:

(1) ni and Fe are non-noble metals, the cost is low, and in addition, the NiFe/rGO catalyst does not need high-temperature pre-reduction treatment and is not inactivated due to oxidation. The active metal component of the NiFe/rGO catalyst does not precipitate in the reaction.

(2) The NiFe/rGO catalyst is prepared by adopting an impregnation-roasting method, and the preparation method is simple and suitable for large-scale industrial preparation. The NiFe/rGO catalyst only directionally hydrogenolysis carbonyl and hydroxyl carbon-oxygen bonds without damaging furan rings or carbon-carbon bonds, so that DMF can not be decomposed, and the catalyst can be used for preparing a catalyst for the catalytic hydrogenation of a metal oxide fuel at 200 ℃ and 2MPa H₂And under the condition of 3h, the yield of the DMF can reach 97 percent, and the high selectivity to the DMF is reflected.

In conclusion, the NiFe/rGO catalyst has the characteristics of high reaction activity, high selectivity and the like when catalyzing the hydrogenation reaction of 5-hydroxymethylfurfural, the conversion rate of the 5-hydroxymethylfurfural in the reaction can reach 100%, the selectivity of 2,5-dimethylfuran can reach 97%, metal components are not separated out, the catalyst does not need to be subjected to high-temperature pre-reduction in the reaction process, the preparation method is suitable for industrial mass preparation, ethanol is used as a solvent, and the catalyst is green and environment-friendly and has obvious advantages and industrial application value.

Detailed Description

The present invention will be described in further detail with reference to examples, but the embodiments of the present invention are not limited thereto. Unless otherwise specified, the experimental methods adopted by the invention are all conventional methods, and experimental equipment, materials, reagents and the like used in the experimental method can be purchased from chemical companies.

Examples 1-3 batch reactions at different reaction temperatures

1. Preparing a catalyst: the preparation method of the NiFe/rGO catalyst by adopting a dipping-roasting method comprises the following specific steps:

(1) preparing a graphene carrier: 230mL of concentrated sulfuric acid and 5.0g of NaNO are taken₃Adding 10g of natural flake graphite powder with stirring, adding 30g of KMnO after stirring for 2.5h₄Transferring the mixture into a 35 ℃ constant temperature water bath for reaction for 2H, adding 460mL of deionized water, stirring the mixture in an oil bath at 98 ℃ for 15min, finally adding 1.4L of deionized water to stop the reaction, and simultaneously adding 25mL of 30% H₂O₂Cooling to room temperature, centrifugally washing with deionized water to neutrality to obtain paste Graphene Oxide (GO), and measuring the dry content to be 1 wt%; and (2) dispersing 100g of GO paste prepared by the method in 1000mL of deionized water, carrying out ultrasonic treatment for 30min, standing, aging, adding 25mL of 30% ammonia water and 6mL of 80% hydrazine hydrate, refluxing in an oil bath at 95 ℃ for 3h, adding 4mL of 80% hydrazine hydrate, reacting for 30min, adding a 4% hydrochloric acid solution, carrying out suction filtration while hot, and carrying out freeze drying to obtain a rGO carrier for later use.

(2) Preparation of salt solution: respectively taking 29.1mg of Ni (NO)₃)₂·6H₂O and 8.1mg Fe (NO)₃)₃·9H₂Dissolving O in 0.85mL of deionized water to prepare a salt solution;

(3) dipping: putting the salt solution prepared in the step (2) into a beaker, adding 0.2mL of absolute ethyl alcohol, adding 100mg of rGO in the step (2), continuously stirring by using a glass rod, and standing the sample at room temperature for 3 hours;

(4) and (3) drying: placing the sample after standing in the step (3) in a vacuum drying oven for drying for 12h at 50 ℃, and grinding the sample by using an agate mortar until the sample becomes a powdery sample;

(5) roasting: and (3) putting the powdery sample prepared in the step (4) into a quartz tube, putting the quartz tube into a tube furnace, raising the temperature from room temperature to 500 ℃ through a program of 10 ℃/min in the nitrogen atmosphere, roasting at the constant temperature of 500 ℃ for 2h, taking out the sample when the temperature is reduced to room temperature, and sealing and storing the sample.

2. Reaction test: the method adopts an intermittent reaction to test the performance of the NiFe/rGO catalyst in catalyzing the hydrogenation reaction of 5-hydroxymethylfurfural, and comprises the following specific steps:

(1) get mechanical stirringStirring a high-pressure reaction kettle, adding 300.0mg of 5-hydroxymethylfurfural, 12mL of ethanol, 120mg of tetradecane serving as an internal standard substance and 30mg of NiFe/rGO catalyst into the high-pressure reaction kettle, screwing the reaction kettle, checking the air tightness of the device, and introducing 2MPa of H after ensuring that the device is airtight₂The stirring rate at 500rpm was set to the specified temperature for 3 hours.

(2) After the reaction was completed, the liquid phase product was collected and analyzed by gas chromatography. The catalyst was recovered by centrifugation.

Wherein: conversion ratio of 5-hydroxymethylfurfural (amount of 5-hydroxymethylfurfural substance at the start of reaction-amount of 5-hydroxymethylfurfural substance at the end of reaction)/amount of 5-hydroxymethylfurfural substance at the start of reaction × 100%

The yield of 2,5-dimethylfuran was 100% based on the amount of 2,5-dimethylfuran substance at the end of the reaction/the amount of 5-hydroxymethylfurfural substance at the start of the reaction

Selectivity of 2,5-dimethylfuran ═ yield of 2, 5-dimethylfuran/conversion of 5-hydroxymethylfurfural × 100%

The chromatographic analysis conditions were: a hydrogen flame detector (FID) is adopted, hydrogen is used as carrier gas, an internal standard method is adopted, and tetradecane is used as an internal standard substance.

3. The reaction results are shown in Table 1

TABLE 1 results for different reaction temperatures

As can be seen from examples 1-3, HMF is also converted at 180 ℃ with only a low reaction rate, and when the reaction temperature reaches 200 ℃, HMF achieves 100% conversion and 97% DMF yield. When the temperature is higher than 220 ℃, the DMF selectivity is not reduced, which indicates that the catalyst can not decompose the product at high temperature.

Examples 2, 4-6 batch reactions at different reaction pressures

1. Preparing a catalyst: the same procedure was used to prepare the catalysts of examples 1-3.

2. Reaction test: the procedure was the same as that of the reaction test in examples 1 to 3, and the reaction conditions were specified: after ensuring the device is airtight, a specified pressure H is introduced₂The reaction was carried out at a stirring speed of 500rpm and a set temperature of 200 ℃ for 3 hours.

3. The reaction results are shown in Table 2.

TABLE 2 results of different reaction pressures

As can be seen from examples 2, 4-6, the conversion rate of HMF can reach 100% after reaction for 3 hours under the conditions of 1MPa-4 MPa and 200 ℃. When H is present₂The catalyst has better catalytic activity even under the pressure of 1.0MPa, and the yield of DMF can reach 78%; when H is present₂When the pressure is increased to 2.0MPa, the yield of the DMF reaches 97 percent. H of 2.0MPa in the reaction system₂Large amounts of activated hydrogen can be produced by NiFe/rGO catalysts, thereby promoting the forward reaction of HMF to DMF. Furthermore, H₂The result that DMF did not fall under the pressure of 3.0MPa or more indicates that excess H was present in the NiFe/rGO catalytic system₂The pressure does not decompose the DMF.

Examples 2, 7-13 batch reactions with different reaction times

2. Preparing a catalyst: the same procedure was used to prepare the catalysts of examples 1-3.

2. Reaction test: the operation procedure was the same as that of the reaction test procedure in examples 1 to 3, and the specific reaction conditions were as follows: 2MPaH is introduced after ensuring the device is airtight₂The reaction was run at a stirring rate of 500rpm, set at a temperature of 200 ℃ for the indicated time.

3. The reaction results are shown in Table 3.

TABLE 3 results for different reaction times

As can be seen from examples 2, 7-13, when the reaction is carried out at 200 ℃ and 2MPa H2, the HMF can be converted 100% when the reaction time is 1.5H, the yield of DMF is 77%, the yield of DMF reaches 97% after the reaction time reaches 3H, and the reaction time is continued to be prolonged, the yield of DMF is not reduced, which indicates that the catalyst is catalytically inert to DMF, and excessive hydrogenation products and ring-opening products for breaking furan rings are not generated. Comparative example 1 batch reaction of Ni/rGO catalyst

1. Preparing a catalyst: the Ni/rGO catalyst is prepared by adopting a dipping-roasting method, and the method comprises the following specific steps:

preparing a salt solution except the salt solution in the step (2): 29.1mg of Ni (NO) were weighed out₃)₂·6H₂Dissolving O in 0.85mL of deionized water to prepare a salt solution; the remaining preparation steps were as in examples 1-3.

2. Reaction test: the performance of the Ni/rGO catalyst in catalyzing the hydrogenation reaction of 5-hydroxymethylfurfural is tested by adopting an intermittent reaction, and the specific steps are the same as those in examples 1-3.

The reaction result shows that the conversion rate of HMF is 100% and the selectivity of DMF is 48% under the action of the catalyst. Under the condition of the same proportion, the NiFe/rGO catalyst can completely convert HMF, and the yield of DMF reaches 97%.

Comparative example 2 batch reaction of Fe/rGO catalyst

1. Preparing a catalyst: the preparation method of the Fe/rGO catalyst by adopting a dipping-roasting method comprises the following specific steps:

preparing a salt solution except the salt solution in the step (2): 8.1mg of Fe (NO) are weighed out₃)₃·9H₂Dissolving O in 0.85mL of deionized water to prepare a salt solution; the remaining preparation steps were as in examples 1-3.

2. Reaction test: the performance of the Fe/rGO catalyst in catalyzing the hydrogenation reaction of 5-hydroxymethylfurfural is tested by adopting an intermittent reaction, and the specific steps are the same as those in examples 1-3.

The reaction result shows that the conversion rate of HMF is 53% and the selectivity of DMF is 3% under the action of the catalyst. Under the condition of the same proportion, the NiFe/rGO catalyst can completely convert HMF, and the yield of DMF reaches 97%.

In addition, the sum of the DMF yields from the reaction of Ni/rGO catalyst and Fe/rGO catalyst was 51%. The yield of the DMF is far lower than that of the DMF obtained by the reaction of the NiFe/rGO catalyst, which shows that the NiFe loaded on the surface of the rGO is not simply physical superposition but forms a synergistic effect to generate an excellent catalytic effect.

Comparative examples 3-5 batch reaction of different supported catalysts

1. Preparing a catalyst: NiFe/Al is prepared by adopting a dipping-roasting method₂O₃、NiFe/HY、NiFe/SiO₂The catalyst comprises the following specific steps:

removing the impregnation in the step (3): placing the prepared salt solution in a beaker, and respectively adding 100mg of Al₂O₃、HY、SiO₂Continuously stirring by using a glass rod, and respectively standing the samples at room temperature for 3 hours; the remaining preparation steps were as in examples 1-3.

2. Reaction test: NiFe/Al testing Using batch reaction₂O₃、NiFe/HY、NiFe/SiO₂The performance of the catalyst for catalyzing the hydrogenation reaction of 5-hydroxymethylfurfural is the same as that in the embodiment 1-3.

3. The reaction results are shown in Table 4.

TABLE 4 results for different supported catalysts

As can be seen from comparative examples 3 to 5, the Al load is₂O₃、HY、SiO₂The good catalytic activity of the NiFe on the carrier can not be obtained without reduction pretreatment, which also verifies the aim that the reduction pretreatment is usually needed in the transition metal catalysis in the literature. The pretreatment process not only complicates the catalyst preparation and maintenance process and increases energy consumption, but also some reduced catalysts may lose activity due to oxidation. The NiFe/rGO catalyst of the invention is used in N₂The catalyst can be directly used after roasting without hydrogen reduction pretreatment, and the weighing process can be directly operated in the air atmosphere without being operated in a glove box. Therefore, the catalyst disclosed by the invention is energy-saving and efficient and has the characteristic of oxidation resistance and inactivation.

The above description is only for the purpose of creating a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can substitute or change the technical solution and the inventive concept of the present invention within the technical scope of the present invention.