A core-shell structure NiCu@C catalyst for preparing gamma-valerolactone by hydrolyzing levulinic acid and a preparation method and use thereof

Abstract

The application provides a core-shell structure NiCu@C catalyst for catalyzing acetylpic acid to be hydrogenated into gamma-valerolactone, a preparation method and use thereof. The catalyst takes a nano-sized NiCu alloy as a core, and an amorphous carbon layer as a shell on the surface of the core. In the nano-sized NiCu alloy, Ni is an active component, and Cu is an additive. The nano-sized NiCu alloy is prepared by a coprecipitation method, and the amorphous carbon layer is prepared by a hydrothermal synthesis method to wrap the core. In the reaction of catalyzing acetylpic acid to be hydrogenated into gamma-valerolactone, the catalyst has high catalytic activity and target product selectivity. Meanwhile, due to the existence of the carbon layer, the catalyst has acid resistance, can inhibit the leaching, agglomeration and deep oxidation of the active metal, and thus has good stability. Furthermore, the catalyst is a heterogeneous catalyst, has the advantages of easy separation, multiple recycling and the like, and has high industrial application value.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of heterogeneous catalysts, and particularly relates to a core-shell structure NiCu@C catalyst for catalyzing acetylpic acid to be hydrogenated into gamma-valerolactone, a preparation method and use thereof. BACKGROUND

[0002] Fossil fuels and the like as energy and fuel sources are increasingly depleted due to generation and living needs, and generate a large amount of harmful substances in the consumption process, causing environmental pollution. Replacing non-renewable energy sources such as fossil fuels with renewable energy sources has become a focus of researchers. Gamma-valerolactone in renewable energy biomass energy is a very promising biomass-based platform compound. Due to its unique physical and chemical properties, high boiling point (207-208℃), high flash point, high calorific value, not easy to volatilize, good stability, low temperature flow, low toxicity and biodegradability, and easy transportation, it can be used to generate various high-value fine chemicals, fuel additives or liquid fuels.

[0003] In the current study, the production process of gamma-valerolactone is mainly based on biomass platform molecule levulinic acid as raw material, which is prepared by microbial reduction method or catalytic hydrogenation method. In production, catalytic hydrogenation method is mostly used, which has short time and high yield compared with microbial reduction method. In the hydrogenation process of levulinic acid to prepare gamma-valerolactone, there are homogeneous or heterogeneous catalysts. Although the homogeneous catalyst has high activity and selectivity, it has problems such as not easy to recover, high cost and the like, which limits its large-scale use. In the heterogeneous catalyst, noble metal (Ru / C, Pt / C, Pd / C) supported catalyst, transition metal nickel-based catalyst, copper-based catalyst, nickel-based metal catalyst and the like are usually used. For noble metal catalyst, patent CN201810099027.9 discloses a kind of sulfur-doped carbon nanotubes (S@CNT) which is prepared by doping sulfur atom to carbon nanotubes (CNTs) with good electrical conductivity, thermal conductivity and high mechanical strength through chemical vapor deposition; then a high-dispersed and high-activity Ru / S@CNTs catalyst with ruthenium (Ru) nanoparticles as active component is prepared by homogeneous oxidation method with the above sulfur-doped carbon nanotubes as carrier; but the active component of the catalyst is noble metal Ru, which is expensive, limiting its industrial application. And because the catalytic environment of levulinic acid is acidic, the loss of non-noble metal catalyst is very serious during the reaction, so the catalyst has high requirements for acid resistance and high stability. Patent CN201911140274.X discloses that hydrogen gas is used as hydrogen source to prepare gamma-valerolactone by hydrogenation of levulinic acid under the action of nickel phosphide catalyst. The hydrogen gas pressure is not less than 0.5Mpa, and the reaction temperature is 80-250℃, but the reaction performance is not good, the selectivity of gamma-valerolactone decreases with the extension of reaction time, and the metal leaching is obvious. Patent CN201210053605.8 discloses a skeleton copper catalyst, which needs to add appropriate amount of skeleton copper catalyst, auxiliary agent and solvent in the liquid phase hydrogenation system of levulinic acid, but the catalyst has short service life.

[0004] In summary, the existing non-noble metal catalyst for preparing gamma-valerolactone by hydrogenation of levulinic acid has problems such as low catalytic activity, low product selectivity and poor catalyst stability, which limits the industrial application efficiency of the catalytic reaction.

[0005] The present application designs a new type of heterogeneous non-noble metal catalyst, which is applied to the preparation of gamma-valerolactone by hydrogenation of levulinic acid, and uses NiCu alloy as catalytic active component, and reduces the leaching, agglomeration and deep oxidation of metal by coating carbon layer to improve the stability. SUMMARY

[0006] In order to solve the above technical problems, the present application provides a core-shell structure NiCu@C catalyst for catalyzing acetylpic acid to hydrogenate γ-valerolactone, and a preparation method and use thereof. The catalyst has high catalytic activity and target product selectivity in the reaction of catalyzing acetylpic acid to hydrogenate γ-valerolactone. Meanwhile, due to the presence of the carbon layer, the catalyst has acid resistance, can inhibit leaching, agglomeration and deep oxidation of the active metal, and thus has good stability.

[0007] Specifically, the present application is realized by the following technical solutions:

[0008] In a first aspect, the present application provides a core-shell structure NiCu@C catalyst for catalyzing acetylpic acid to hydrogenate γ-valerolactone. The catalyst has a nanometer-sized NiCu alloy as a core and an amorphous carbon layer as a shell on the surface of the core. In the nanometer-sized NiCu alloy, Ni is an active component and Cu is an additive. The nanometer-sized NiCu alloy is prepared by a coprecipitation method, and the amorphous carbon layer is prepared by a hydrothermal synthesis method to wrap the core. The particle size of the core is 20-30 nm, and the thickness of the shell is 2-3 nm.

[0009] Preferably, in the above catalyst, the molar ratio of Ni to Cu in the NiCu alloy is 1-5:1.

[0010] In a second aspect, the present application provides a preparation method of the above core-shell structure NiCu@C catalyst, comprising the following steps:

[0011] (1) mixing water-soluble Cu salt, water-soluble Ni salt and ethylene glycol according to a certain amount, and stirring at a certain temperature, the stirring temperature being 150-200℃ and the stirring time being 0.5-1h;

[0012] (2) adding a certain concentration of sodium carbonate aqueous solution dropwise into the mixed solution in step (1) according to a certain amount, keeping stirring during the adding process, the stirring speed being 400-600r / min and the stirring temperature being 150-200℃; after the adding is completed, keeping the temperature and the speed, and aging for 1-5h to obtain a suspension, which is filtered and washed to obtain brown precipitate;

[0013] (3) adding the brown precipitate obtained in step (2) into a hydrothermal synthesis kettle, and adding carbon source precursor and deionized water according to a certain amount, stirring, ultrasonicating, and then performing hydrothermal treatment, the hydrothermal temperature being 170-200℃ and the hydrothermal time being 15-24h;

[0014] (4) filtering, washing, drying the hydrothermal product obtained in step (3) to obtain black precipitate, wherein the drying temperature is 110-130℃, and the drying time is 10-15h;

[0015] (5) carbonizing the black precipitate obtained in step (4) under argon atmosphere for several hours to obtain the core-shell structure NiCu@C catalyst.

[0016] In the above step (1), the water-soluble Cu salt is selected from one or more of copper nitrate, copper sulfate, and hydrated copper acetate, and preferably is hydrated copper acetate; and the water-soluble Ni salt is selected from one or more of nickel nitrate, nickel chloride, and tetrahydrate nickel acetate, and preferably is tetrahydrate nickel acetate.

[0017] In the above step (3), the carbon source precursor is selected from one or more of glucose, maltose, and fructose, and preferably is glucose.

[0018] In the above step (5), the carbonization temperature is 500-700℃, and the carbonization time is 3-8h.

[0019] In a third aspect, the present application provides the use of the above core-shell structure NiCu@C catalyst or the core-shell structure NiCu@C catalyst prepared by the above method, wherein the catalyst is used for catalyzing the hydrogenation of levulinic acid to prepare gamma-valerolactone.

[0020] In a fourth aspect, the present application provides a method for preparing gamma-valerolactone by hydrogenation of levulinic acid, wherein the hydrogenation reaction of levulinic acid uses the above core-shell structure NiCu@C catalyst or the core-shell structure NiCu@C catalyst prepared by the above method.

[0021] The reaction temperature of the above hydrogenation reaction of levulinic acid is 160-220℃, the reaction pressure is 0.5-2.0Mpa, and the reaction solvent is selected from one or more of toluene, ethylbenzene, tetrahydrofuran, and cyclohexane, and preferably is toluene.

[0022] The above hydrogenation reaction of levulinic acid can use a batch production of a reaction kettle.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] (1) The catalyst provided by the application is the first to report that a nano-sized NiCu alloy is used as a core, and an amorphous carbon layer is coated as a shell on the surface of the core, and the core-shell components synergistically act to catalyze the hydrogenation of levulinic acid to gamma-valerolactone. The introduction of the catalyst additive Cu is beneficial to the adjustment of the electronic properties of the active component Ni, and through the influence of the active component Ni on the intermediate product, high selectivity of the target product is achieved. Moreover, the introduction of the additive Cu can also promote the high dispersion of the active component Ni, which is beneficial to improving the adsorption capacity of the reaction raw gas and the anti-agglomeration sintering capacity, thereby improving the stability of the catalyst. In addition, the carbon layer coating designed in the application makes the catalyst resistant to acid, can inhibit the leaching, agglomeration and deep oxidation of the active metal, thereby improving the stability, repeated use performance and performance after regeneration of the catalyst.

[0025] (2) The preparation method of the catalyst provided by the application innovatively combines the coprecipitation method and the hydrothermal synthesis method to realize the combination of the active component Ni, the additive Cu and the carbon layer coating material, and realizes high catalytic activity, high stability and high selectivity of the product of the catalyst.

[0026] (3) The catalyst provided by the application has high economic advantages, and the preparation method is easy to control and can realize industrial production, thereby meeting the industrial application of the hydrogenation of levulinic acid to gamma-valerolactone. BRIEF DESCRIPTION OF DRAWINGS

[0027] The accompanying drawings are included to provide a further understanding of the application and constitute a part of the specification, illustrate the application together with the embodiments of the application, and do not constitute a limitation on the application. In the drawings:

[0028] Figure 1 The transmission electron microscopy diagram of the core-shell structure Ni1Cu1@C catalyst prepared for the embodiment 1 of the application.

[0029] Figure 2 The XRD spectrum of the core-shell structure Ni1Cu1@C catalyst prepared for the embodiment 1 of the application.

[0030] Figure 3 The transmission electron microscopy diagram of the core-shell structure Ni1Cu1@C catalyst prepared for the embodiment 1 of the application after being used to catalyze the reaction of the hydrogenation of levulinic acid to gamma-valerolactone.

[0031] Figure 4 The catalytic result schematic diagram of the core-shell structure Ni1Cu1@C catalyst prepared for the embodiment 1 of the application after being used to catalyze the reaction of the hydrogenation of levulinic acid to gamma-valerolactone for 5 cycles.

[0032] Figure 5 The transmission electron microscopy diagram of the Ni1Cu1 catalyst prepared for the comparative example 1 of the application.

[0033] Figure 6 TEM image of the Ni1Cu1 catalyst prepared for the Inventive Comparative Example 1 after being used to catalyze the reaction of levulinic acid hydrogenation to γ-valerolactone.

[0034] Figure 7 Catalytic results of the Ni1Cu1 catalyst prepared for the Inventive Comparative Example 1 after being used to catalyze the reaction of levulinic acid hydrogenation to γ-valerolactone for 5 cycles.

[0035] Figure 8 Catalytic metal leaching results of the catalysts prepared for the Inventive Example 1 and the Inventive Comparative Example 1 after being used to catalyze the reaction of levulinic acid hydrogenation to γ-valerolactone for 5 cycles. DETAILED DESCRIPTION

[0036] The embodiments of the present application are described in detail below, and the embodiments are provided to better illustrate the content of the present application and are only used to explain the present application and cannot be understood as a limitation of the present application.

[0037] The specific techniques or conditions not specified in the embodiments are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. The reagents or instruments not specified by the manufacturer are all conventional products that can be purchased through regular channels.

[0038] The product analysis method in the embodiments of the present application uses an Agilent chromatograph for analysis, and the specific detection method of the hydrogenation product of levulinic acid is as follows:

[0039] Injection amount: 0.5 μL; chromatographic column: Agilent HP-5 type (30 m*250 um*0.25 um); column temperature: 50°C for 5 min, increased to 150°C at a rate of 5°C / min, maintained for 5 min, increased to 200°C at a rate of 10°C / min, maintained for 5 min; injection port temperature: 270°C; detector temperature: 270°C.

[0040] Spacer purge gas flow rate: 3 ml / min; chromatographic column flow rate (N2): 1 ml / min; split injection, split ratio: 50:1; hydrogen flow rate: 40 ml / min; air flow rate: 350 ml / min; tail gas purge flow rate: 25 ml / min.

[0041] Example 1

[0042] The preparation method of the core-shell structure Ni1Cu1@C catalyst (the molar ratio of Ni element and Cu element is 1:1) includes the following steps:

[0043] (1) 3.5 g of nickel acetate tetrahydrate, 2.8 g of copper acetate hydrate and 100 ml of ethylene glycol are mixed and stirred at 160°C for 0.5 h;

[0044] (2) 6 g of sodium carbonate was dissolved in 160 ml of deionized water, and the mixed solution in step (1) was added dropwise, the stirring speed was 500 r / min, and the stirring temperature was kept at 160°C; after the dropwise addition was completed, the temperature and speed were kept, and aging was performed for 1 h, to obtain a suspension, which was filtered and washed to obtain a brown precipitate;

[0045] (3) The brown precipitate obtained in step (2) was added to a hydrothermal synthesis kettle, 1.06 g of glucose and 40 ml of deionized water were added, stirred, ultrasonicated, and then subjected to hydrothermal treatment, the hydrothermal temperature was 175°C, and the hydrothermal time was 18 h;

[0046] (4) The hydrothermal product obtained in step (3) was filtered, washed, and dried to obtain a black precipitate, the drying temperature was 120°C, and the drying time was 12 h;

[0047] (5) The black precipitate obtained in step (4) was carbonized at 600°C for 4 h under an argon atmosphere to obtain a core-shell structure Ni1Cu1@C catalyst, which is denoted as catalyst 1#. The transmission electron microscopy (TEM) image of the catalyst 1# is shown in FIG. 1, and the XRD pattern of the catalyst 1# is shown in FIG. 2. Figure 1 Figure 2

[0048] The acetic acid propionic acid hydrogenation reaction of the catalyst 1# prepared above to prepare γ-valerolactone: 1 mmol of the reaction substrate acetic acid propionic acid, 2 ml of the toluene reaction solvent, and 0.03 g of the catalyst 1# were sequentially placed in an autoclave; the autoclave was replaced with H2 multiple times, after the replacement was completed, hydrogen was filled to a total pressure of 1 MPa; the reaction was carried out at 200°C for 1 h, and the mixture was analyzed by chromatography after the reaction kettle was cooled to room temperature. The reaction results of the catalyst 1# prepared above in the acetic acid propionic acid hydrogenation reaction to prepare γ-valerolactone are shown in Table 1. The transmission electron microscopy (TEM) image of the catalyst 1# after the reaction is shown in FIG. 3. Figure 3

[0049] Example 2

[0050] A preparation method of a core-shell structure Ni2Cu1@C catalyst (the molar ratio of Ni element and Cu element is 2:1) includes the following steps:

[0051] (1) 4.6667 g of nickel acetate tetrahydrate, 1.8724 g of copper acetate hydrate, and 100 ml of ethylene glycol were mixed, and stirring was performed at 160°C for 0.5 h;

[0052] ​​​(2) 6 g of sodium carbonate was dissolved in 160 ml of deionized water, and the mixed solution in step (1) was added dropwise, stirring was maintained during the addition process, the stirring speed was 500 r / min, and the stirring temperature was maintained at 160°C; after the dropwise addition was completed, the temperature and speed were maintained, and aging was performed for 1 h, a suspension was obtained, which was filtered and washed to obtain a brown precipitate;

[0053] (3) The brown precipitate obtained in step (2) was added to a hydrothermal synthesis kettle, 1.06 g of glucose and 40 ml of deionized water were added, stirring, ultrasonic, and then hydrothermal treatment was performed, the hydrothermal temperature was 175°C, and the hydrothermal time was 18 h;

[0054] (4) The hydrothermal product obtained in step (3) was filtered, washed, and dried to obtain a black precipitate, the drying temperature was 120°C, and the drying time was 12 h;

[0055] (5) The black precipitate obtained in step (4) was carbonized at 600°C for 4 h under an argon atmosphere to obtain a core-shell structure Ni2Cu1@C catalyst, which is denoted as catalyst 2#.

[0056] The acetic acid propionic acid hydrogenation reaction of the catalyst 2# prepared above to prepare γ-valerolactone: 1 mmol of the reaction substrate acetic acid propionic acid, 2 ml of the toluene reaction solvent, and 0.03 g of the catalyst 2# were sequentially placed in a high-pressure kettle; the high-pressure kettle was replaced with H2 multiple times, after the replacement was completed, hydrogen was filled to a total pressure of 1 Mpa; the reaction was carried out at 200°C for 1 h, and the mixture was analyzed by chromatography after the reaction kettle was cooled to room temperature. The reaction results of the acetic acid propionic acid hydrogenation reaction catalyzed by the catalyst 2# prepared above to prepare γ-valerolactone are shown in Table 1.

[0057] Example 3

[0058] A preparation method of a core-shell structure Ni3Cu1@C catalyst (the molar ratio of Ni element and Cu element is 3:1) includes the following steps:

[0059] (1) 5.25 g of nickel acetate tetrahydrate, 1.4043 g of copper acetate hydrate, and 100 ml of ethylene glycol were mixed, and stirring was performed at 160°C for 0.5 h;

[0060] (2) 6 g of sodium carbonate was dissolved in 160 ml of deionized water, and the mixed solution in step (1) was added dropwise, stirring was maintained during the addition process, the stirring speed was 500 r / min, and the stirring temperature was maintained at 160°C; after the dropwise addition was completed, the temperature and speed were maintained, and aging was performed for 1 h, a suspension was obtained, which was filtered and washed to obtain a brown precipitate;

[0061] (3) Add the brown precipitate obtained in step (2) to a hydrothermal synthesis vessel, add 1.06g of glucose and 40ml of deionized water, stir, sonicate, and then perform hydrothermal treatment at a temperature of 175℃ for 18h.

[0062] (4) The hydrothermal product obtained in step (3) is filtered, washed and dried to obtain a black precipitate. The drying temperature is 120℃ and the drying time is 12h.

[0063] (5) The black precipitate obtained in step (4) is carbonized at 600°C for 4 hours under an argon atmosphere to obtain a core-shell structured Ni3Cu1@C catalyst, denoted as catalyst 3#.

[0064] The hydrogenation of levulinic acid to γ-valerol using catalyst 3# prepared above was carried out as follows: 1 mmol of levulinic acid, 2 ml of toluene reaction solvent, and 0.03 g of catalyst 3# were sequentially added to an autoclave; the air in the autoclave was replaced with H2 several times, and after replacement, hydrogen gas with a total pressure of 1 MPa was introduced; the reaction was carried out at 200℃ for 1 h, and after the autoclave cooled to room temperature, the mixture was subjected to chromatographic quantitative analysis. The results of the hydrogenation of levulinic acid to γ-valerol catalyzed by catalyst 3# prepared above are shown in Table 1.

[0065] Example 4

[0066] The hydrogenation of levulinic acid to γ-valerol was carried out using catalyst 1# prepared above, with the reaction temperature varied. In a high-pressure reactor, 1 mmol of the substrate levulinic acid, 2 ml of toluene reaction solvent, and 0.03 g of catalyst 1# were added sequentially. The air in the reactor was replaced several times with H2. After replacement, hydrogen gas with a total pressure of 1 MPa was introduced. The reaction was carried out at 170 °C for 1 h. After the reactor cooled to room temperature, the mixture was subjected to chromatographic quantitative analysis. The results of the hydrogenation of levulinic acid to γ-valerol catalyzed by catalyst 1# prepared above are shown in Table 1.

[0067] Example 5

[0068] After the catalyst 1# prepared above was subjected to the catalytic hydrogenation of levulinic acid to γ-valerol, it was separated by centrifugation, washed with toluene, and filtered. The obtained catalyst 1# was then used to catalyze the hydrogenation of levulinic acid to γ-valerol, and the catalyst was recycled 5 times. Other conditions were the same as in Example 1. The results of the catalyst recycling reaction are as follows. Figure 4 As shown. From Figure 4 It can be seen that the core-shell structured Ni1Cu1@C catalyst prepared in this invention can still maintain its high catalytic activity and high product selectivity after being recycled 5 times.

[0069] Comparative Example 1

[0070] The preparation method of the Ni1Cu1 catalyst (the molar ratio of Ni element and Cu element is 1:1) comprises the following steps:

[0071] The catalyst 1# prepared in Example 1 is calcined in an air atmosphere at 450°C for 2h, and then reduced in an H2 atmosphere at 600°C for 2h to obtain the Ni1Cu1 catalyst, which is denoted as the comparative catalyst 1#. The transmission electron microscope image of the comparative catalyst 1# is shown in FIG. 2. Figure 5

[0072] The reaction of acetylpropionic acid hydrogenation to γ-valerolactone using the comparative catalyst 1# prepared above is carried out as follows: 1mmol of the reaction substrate acetylpropionic acid, 2ml of the reaction solvent toluene and 0.03g of the comparative catalyst 1# are sequentially placed in an autoclave; the autoclave is replaced with H2 for several times, and then filled with hydrogen with a total pressure of 1Mpa; the reaction is carried out at 200°C for 1h, and then the mixture is analyzed by chromatography after the autoclave is cooled to room temperature. The reaction results of acetylpropionic acid hydrogenation to γ-valerolactone using the comparative catalyst 1# prepared above are shown in Table 1. The transmission electron microscope image of the comparative catalyst 1# after the reaction is shown in FIG. 3. Figure 6

[0073] Comparative Example 2

[0074] After the reaction of acetylpropionic acid hydrogenation to γ-valerolactone using the comparative catalyst 1# prepared above, the comparative catalyst 1# is separated by centrifugation, washed with toluene, filtered, and then used for the reaction of acetylpropionic acid hydrogenation to γ-valerolactone again. The catalyst is recycled for 5 times, and the other conditions are the same as those in Comparative Example 1. The results of the catalyst recycling reaction are shown in Table 2. It can be seen from Table 2 that the catalytic performance of the comparative catalyst 1# without carbon layer coating decreases obviously after the first reaction, and the comparative catalyst 1# cannot maintain its excellent catalytic performance after 5 times of recycling. Figure 7 Figure 7 As shown in Table 2, the leaching amount of active metal of the comparative catalyst 1# is more than 20 times of that of the catalyst 1#, which indicates that the catalyst 1# prepared in the present application can effectively inhibit the leaching of active metal, and the stability of the catalyst is good. Figure 8

[0075] The catalyst 1# and the comparative catalyst 1# prepared in the present application are respectively used for the reaction of acetylpropionic acid hydrogenation to γ-valerolactone, and the transmission electron microscope images of the catalysts before and after the reaction are shown in FIGS. 1 and 2. Figure 1 Figure 3 Figure 5 Figure 6 ​​​​​​​It can be seen that there is no obvious difference in the morphology and size of the active metal particles of the catalyst 1 prepared in the application before and after the reaction, but the active metal particles of the comparative catalyst 1# obviously agglomerate and the particle size obviously increases. Thus it is illustrated that the catalyst 1 coated by carbon layer prepared in the application can inhibit the structural reconstruction of the active metal and maintain the stability of the catalyst.

[0076] Table 1: Reaction results of the catalyst prepared in the application in catalyzing the reaction of levulinic acid hydrogenation to γ-valerolactone

[0077]

[0078]

[0079] It can be seen from Table 1 that the core-shell structure NiCu@C catalyst described in the application has high catalytic activity, high selectivity and good stability when used for catalyzing the reaction of levulinic acid hydrogenation to γ-valerolactone, and has high industrial application value.

[0080] Obviously, the above examples are only examples for clearly illustrating the present application, and are not intended to limit the embodiments of the present application. Those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application belong to the scope of the claims of the present application and the equivalent technologies thereof, the present application also intends to include these modifications and variations.

Claims

1. A method for preparing γ-valerol by hydrogenation of levulinic acid, characterized in that, The hydrogenation reaction of levulinic acid employs a core-shell structured NiCu@C catalyst. The catalyst uses a nano-sized NiCu alloy as the core, with an amorphous carbon layer coating its surface as the shell. In the nano-NiCu alloy, Ni is the active component and Cu is the auxiliary agent. The nano-NiCu alloy is prepared by co-precipitation, and the amorphous carbon layer is synthesized by hydrothermal method to encapsulate the core. The core has a particle size of 20-30 nm, and the shell has a thickness of 2-3 nm. In the NiCu alloy, the molar ratio of Ni to Cu is 1-5:

1.

2. The method according to claim 1, characterized in that, The preparation method of the core-shell structured NiCu@C catalyst includes the following steps: (1) Mix water-soluble Cu salt, water-soluble Ni salt, and ethylene glycol according to a certain amount, and stir at a certain temperature. The stirring temperature is 150~200℃ and the stirring time is 0.5~1h. (2) According to the measurement, a certain concentration of sodium carbonate aqueous solution is added drop by drop to the mixed solution in step (1). During the addition process, stirring is maintained at a speed of 400~600 r / min and the stirring temperature is maintained at 150~200℃. After the addition is completed, the temperature and speed are maintained and the mixture is aged for 1~5 hours to obtain a suspension. The suspension is then filtered and washed to obtain a brown precipitate. (3) Add the brown precipitate obtained in step (2) into a hydrothermal synthesis reactor, and add carbon source precursor and deionized water according to the metering. Stir, sonicate, and then perform hydrothermal treatment. The hydrothermal temperature is 170~200℃ and the hydrothermal time is 15~24h. (4) The hydrothermal product obtained in step (3) is filtered, washed and dried to obtain a black precipitate, wherein the drying temperature is 110~130℃ and the drying time is 10~15h; (5) The black precipitate obtained in step (4) is carbonized at high temperature for several hours in an argon atmosphere to obtain a core-shell structured NiCu@C catalyst.

3. The method according to claim 2, characterized in that, In step (1), the water-soluble Cu salt is selected from one or more of copper nitrate, copper sulfate, and hydrated copper acetate; the water-soluble Ni salt is selected from one or more of nickel nitrate, nickel chloride, and nickel acetate tetrahydrate. In step (3), the carbon source precursor is selected from one or more of glucose, maltose, and fructose; In step (5), the carbonization temperature is 500~700℃ and the carbonization time is 3~8h.

4. The method according to claim 3, characterized in that, In step (1), the water-soluble Cu salt is selected from hydrated copper acetate; the water-soluble Ni salt is selected from nickel acetate tetrahydrate. In step (3), the carbon source precursor is selected from glucose.

5. The method according to claim 1, characterized in that, The reaction temperature for the hydrogenation reaction of levulinic acid is 160~220℃, and the reaction pressure is 0.5~2.0 MPa; the reaction solvent is selected from one or more of toluene, ethylbenzene, tetrahydrofuran, and cyclohexane.

6. The method according to claim 5, characterized in that, The reaction solvent is toluene.

7. The method according to any one of claims 1-6, characterized in that, The hydrogenation reaction of levulinic acid is carried out in a batch reactor.

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