Application of high-activity Zn-based catalyst Zn (at) Nx / NC in catalytic transfer hydrogenation of 5-hydroxymethylfurfural

Abstract

The invention discloses application of a high-activity Zn-based catalyst Zn (at) Nx / NC in catalytic transfer hydrogenation of 5-hydroxymethylfurfural, and belongs to the technical field of catalyst preparation. The preparation method of the catalyst comprises the following steps: dissolving zinc nitrate hexahydrate and an auxiliary agent in a solvent to obtain a solution A, dissolving a template agent in the solvent to obtain a solution B, adding the solution B into the solution A under violent stirring, and continuously stirring to completely react to obtain a solid precipitate; and roasting the solid precipitate to obtain the Zn-based catalyst Zn (at) Nx / NC. The catalyst can be used for carrying out catalytic transfer hydrogenation on HMF to generate 2, 5-bis (hydroxymethyl) furan and 2, 5-dimethylfuran, C-O bonds and C = O bonds can be efficiently catalyzed, transferred and hydrocracked under mild conditions, the conversion rate of reactants is greater than 98%, and the yield of products is high. The catalyst is simple to prepare, the active metal zinc is non-noble metal, the cost is low, and the reaction activity is high.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalyst preparation, and particularly relates to the application of a highly active Zn-based catalyst Zn@Nx / NC in the catalytic transfer hydrogenation of 5-hydroxymethylfurfural. Background Art

[0002] In recent years, the rapid growth of carbon dioxide emissions caused by the combustion of fossil fuels has attracted increasing attention to the resulting global warming problem. As a renewable resource with abundant reserves and broad prospects, inedible biomass can be converted into useful chemical raw materials, which has become a potential way to replace petroleum-based synthesis and achieve carbon neutrality. Generally, biomass is first converted into highly oxygenated platform compounds, which can then be transformed into high-value-added chemicals and biofuels through selective hydrogenation and hydrodeoxygenation reactions. From a chemical perspective, to achieve the upgrading of biomass, the key steps are the catalytic hydrogenation of the carbonyl double bond (C=O) and the cleavage of the carbon-oxygen single bond (C–O). Biomass-derived 5-hydroxymethylfurfural (HMF) contains C–O bonds, C=O bonds, and a furan ring, and has attracted much attention due to its ideal functional components. It not only provides a flexible route for the production of biopolymers and biofuels, but also can be used as an example to illustrate the hydrogenation reaction mechanism. Among the hydrogenation products of HMF, 2,5-dimethylfuran (DMF) is regarded as a promising biofuel due to its high energy density, high research octane number, and low water solubility.

[0003] Zinc, a metal with abundant reserves, safety, and low cost, has been widely used in the development of Lewis acid catalysts to activate electron-rich groups such as alkynes and nitroarenes (Camacho-Bunquin, J. et al. Single-site zinc on silica catalysts for propylene hydrogenation and propane dehydrogenation: synthesis and reactivity evaluation using an integrated atomic layer deposition-catalysis instrument. J. Catal. 345, 170–182 (2017)). In addition, zinc-based catalysts with single zinc sites have also been reported, which can be used for the reductive N-formylation of nitroarenes and the oxidative cleavage of C(CO)-C bonds (Xie, C. et al. Zn-Nx sites on N-doped carbon for aerobic oxidative cleavage and esterification of C(CO)-C bonds. Nat. Commun. 12, 4823 (2021)), and a single zinc acts as the active site for these processes. However, although zinc-based catalysts have been applied to various catalytic processes, their performance as catalytic transfer hydrogenation (CTH) catalysts has not been explored. Summary of the Invention

[0004] An object of the present invention is to provide an application of a highly active Zn-based catalyst Zn@Nx / NC in the catalytic transfer hydrogenation of 5-hydroxymethylfurfural in view of the deficiencies of the prior art. The preparation steps of this catalyst are simple, the reaction conditions are mild, and it has excellent catalytic transfer hydrogenation performance for HMF.

[0005] To achieve the above object, the present invention adopts the following technical solutions: In the first aspect, the present invention provides a preparation method of a highly active Zn-based catalyst Zn@Nx / NC, including the following steps: Dissolve zinc nitrate hexahydrate and an auxiliary agent in a solvent to obtain solution A, dissolve a template agent in the solvent to obtain solution B, and add solution B to solution A under vigorous stirring, and continue to stir at room temperature until the reaction is complete; centrifuge, wash, and vacuum dry the obtained mixture to obtain an intermediate; subsequently, put the prepared intermediate into a tube furnace for calcination to obtain the Zn-based catalyst Zn@Nx / NC.

[0006] Optionally, the promoter is selected from one or more of gallium nitrate (Ga(NO3)3·9H2O), zirconium nitrate (Zr(NO3)4·5H2O), lanthanum nitrate (La(NO3)3·6H2O), and nickel nitrate (Ni(NO3)2·6H2O).

[0007] Optionally, the mass ratio of zinc nitrate hexahydrate, the promoter, and the template agent is controlled between 1:1:1 and 1:1.5:2.

[0008] Optionally, the template agent is selected from one or more of 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-isopropylimidazole, and 2-propylimidazole.

[0009] Optionally, the solvent is selected from one or more of methanol, ethanol, isopropanol, and cyclohexane.

[0010] Furthermore, the stirring time is 12 - 24 h.

[0011] Furthermore, in the centrifugation step, the centrifuge speed is 3000 - 6000 rpm.

[0012] Furthermore, in the vacuum drying step, the drying temperature is 60 - 100 °C and the time is 6 h - 12 h.

[0013] Furthermore, the calcination temperature is 600 - 900 °C and the calcination time is 2 - 5 h.

[0014] Furthermore, the calcination atmosphere is one or more of air, nitrogen, helium, and argon.

[0015] In a second aspect, the present invention provides the application of the Zn-based catalyst Zn@Nx / NC prepared by the preparation method of any item in the first aspect in the catalytic transfer hydrogenation of 5-hydroxymethylfurfural.

[0016] Furthermore, the application includes the following steps: (1) Put 5-hydroxymethylfurfural, the catalyst Zn@Nx / NC, and the reaction solvent into a high-pressure stirred autoclave reactor, seal it, and introduce nitrogen to remove the residual air in the autoclave; (2) Continuously introduce nitrogen at room temperature to pressurize the reactor to the set pressure, then raise the temperature to the required reaction temperature, and stir for catalytic transfer hydrogenation reaction.

[0017] In step (1), the reaction solvent is selected from one or more of methanol, ethanol, ethylene glycol, and isopropanol.

[0018] In step (1), the molar ratio of 5-hydroxymethylfurfural, the catalyst Zn@Nx / NC, and the reaction solvent is controlled between 1:1.5:5 and 1:2:8.

[0019] In step (2), the reaction temperature is 150~230 °C, the reaction pressure is 1~3 Mpa, and the reaction time is 2-6 h.

[0020] Compared with the prior art, the present invention has the following beneficial effects: The Zn@Nx / NC catalyst prepared by the present invention has high activity and good stability. When one or more combinations of methanol, ethanol, ethylene glycol, and isopropanol are used as solvents, it can efficiently catalyze the hydrogenolysis of C-O bonds and C=O bonds of HMF under mild conditions to produce 2,5-bis(hydroxymethyl)furan (BHMF) and 2,5-dimethylfuran (DMF). The conversion rate of the reactants is greater than 98%, and the yield of the products is high. The preparation of the catalyst of the present invention is simple, the active metal zinc is a non-noble metal, the cost is low, the reaction activity is high, and it has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 XRD pattern of the Zn-based catalyst Zn@Nx / NC prepared in Examples 1-4 of the present invention; Figure 2 SEM image of the Zn-based catalyst Zn@Nx / NC prepared in Example 1 of the present invention; Figure 3 TEM image (left) and elemental mapping image (right) of the Zn-based catalyst Zn@Nx / NC prepared in Example 1 of the present invention; Figure 4 Catalytic activity test diagram of the Zn-based catalyst Zn@Nx / NC prepared in Examples 1-4 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] The present invention will be further described below in conjunction with specific embodiments. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention, and cannot be used to limit the protection scope of the present invention.

[0023] It should be noted that unless otherwise specified, the technical terms or scientific terms used in this application should have the ordinary meaning understood by those skilled in the art to which the present invention belongs.

[0024] Example 1

[0025] 1. Preparation of Zn@Nx / NC1 catalyst Dissolve 3.0 g of zinc nitrate hexahydrate (Zn(NO3)3·6H2O) and 3.4 g of gallium nitrate (Ga(NO3)3·9H2O) in 120 ml of methanol to obtain solution A. Dissolve 3.7 g of 2-methylimidazole in 120 ml of methanol to obtain solution B, and add solution B to the above precursor solution A under vigorous stirring.

[0026] The mixed solution was stirred at room temperature for 12 h, centrifuged at 4000 rpm, and the obtained product was washed with methanol until the solution was colorless to obtain a solid product. The solid product was dried in vacuo at 60 °C for 6 h to obtain an intermediate.

[0027] Subsequently, the prepared intermediate was placed in a tubular furnace and maintained at 600 °C for 5 h in a nitrogen atmosphere. Then, the tubular furnace was naturally cooled to room temperature, and the obtained powder was labeled Zn@Nx / NC1 and directly used as a catalyst without further treatment.

[0028] 2. Catalytic transfer hydrogenation reaction (1) HMF, the catalyst Zn@Nx / NC1 prepared in Example 1, and the reaction solvent were put into a high-pressure stirred autoclave reactor together at a molar ratio of 1:1.5:5. The reaction solvent was isopropanol. After sealing, nitrogen was introduced to remove the residual air in the autoclave. (2) The reactor was pressurized to 2 Mpa by continuously introducing nitrogen at room temperature, then the temperature was raised to 200 °C, and the reaction was stirred for 4 h. (3) After the reaction, the reaction system was naturally cooled to room temperature and the pressure was released. The catalyst was removed by filtration, and the obtained organic phase was analyzed by GC-MS.

[0029] Example 2

[0030] 1. Preparation of Zn@Nx / NC2 catalyst A mixture of 3.0 g of zinc nitrate hexahydrate (Zn(NO3)3·6H2O) and 3.4 g of zirconium nitrate (Zr(NO3)4·5H2O) was dissolved in 150 ml of ethanol to obtain solution A. 3.8 g of 2-ethyl-4-methylimidazole was dissolved in 150 ml of ethanol to obtain solution B, and solution B was added to the above precursor solution A under vigorous stirring.

[0031] The mixed solution was stirred at room temperature for 16 h, centrifuged at 3000 rpm, and the obtained product was washed with ethanol until the solution was colorless to obtain a solid product. The solid product was dried in vacuo at 80 °C for 8 h and labeled as an intermediate.

[0032] Subsequently, the prepared intermediate was placed in a tubular furnace and maintained at 700 °C for 4 h in an air atmosphere. Then, the tubular furnace was naturally cooled to room temperature, and the obtained powder was labeled Zn@Nx / NC2 and directly used as a catalyst without further treatment.

[0033] 2. Catalytic transfer hydrogenation reaction (1) Put HMF, the catalyst Zn@Nx / NC2 prepared in Example 2, and the reaction solvent into a high-pressure stirred autoclave reactor in a molar ratio of 1:1.8:6. The reaction solvent is methanol. After sealing, introduce nitrogen to remove the residual air in the autoclave. (2) Continuously introduce nitrogen at room temperature to pressurize the reactor to 1.8 Mpa, then raise the temperature to 190 °C, and stir the reaction for 3 h. (3) After the reaction is completed, naturally cool the reaction system to room temperature and release the pressure. Filter out the catalyst, and analyze the obtained organic phase by GC-MS.

[0034] Example 3

[0035] 1. Preparation of Zn@Nx / NC3 catalyst Dissolve a mixture of 2.8 g of zinc nitrate hexahydrate (Zn(NO3)3·6H20) and 3.2 g of lanthanum nitrate (La(NO3)3·6H2O) in 150 ml of isopropanol to obtain solution A. Dissolve 4.3 g of 2-isopropylimidazole in 150 ml of isopropanol to obtain solution B, and add solution B to the above precursor solution A under vigorous stirring.

[0036] Stir the mixed solution at room temperature for 18 h, centrifuge at a speed of 5000 rpm, wash the obtained product with isopropanol until the solution is colorless to obtain a solid product. Dry the solid product under vacuum at 90 °C for 10 h and label it as the intermediate.

[0037] Subsequently, put the prepared intermediate into a tubular furnace, keep it at 800 °C for 3 h in an argon atmosphere, and then naturally cool the tubular furnace to room temperature. The obtained powder is labeled as Zn@Nx / NC3 and directly used as a catalyst without further treatment.

[0038] 2. Catalytic transfer hydrogenation reaction (1) Put HMF, the catalyst Zn@Nx / NC3, and the reaction solvent into a high-pressure stirred autoclave reactor in a molar ratio of 1:1.7:7. The reaction solvent is ethanol. After sealing, introduce nitrogen to remove the residual air in the autoclave. (2) Continuously introduce nitrogen at room temperature to pressurize the reactor to 2.2 Mpa, then raise the temperature to 210 °C, and stir the reaction for 5 h. (3) After the reaction is completed, naturally cool the reaction system to room temperature and release the pressure. Filter out the catalyst, and analyze the obtained organic phase by GC-MS.

[0039] Example 4

[0040] 1. Preparation of Zn@Nx / NC4 catalyst Dissolve a mixture of 3.8 g of zinc nitrate hexahydrate (Zn(NO3)3·6H20) and 4.0 g of nickel nitrate (Ni(NO3)2·6H2O) in 180 ml of cyclohexane to obtain solution A. Dissolve 3.2 g of 2-propylimidazole in 180 ml of cyclohexane to obtain solution B, and add solution B to the above-mentioned precursor solution A under vigorous stirring.

[0041] Stir the mixed solution at room temperature for 24 h, centrifuge at a speed of 6000 rpm, wash the obtained product with cyclohexane until the solution is colorless to obtain a solid product. The solid product is dried under vacuum at 100 °C for 12 h and labeled as the intermediate.

[0042] Subsequently, put the prepared intermediate into a tubular furnace, keep it at 900 °C for 2 h in a helium atmosphere, then naturally cool the tubular furnace to room temperature. The obtained powder is labeled as Zn@Nx / NC4 and directly used as a catalyst without further treatment.

[0043] 2. Catalytic transfer hydrogenation reaction (1) Put HMF, the catalyst Zn@Nx / NC3, and the reaction solvent into a high-pressure stirred autoclave reactor in a molar ratio of 1:1.6:8. The reaction solvent is ethylene glycol. After sealing, introduce nitrogen to remove the residual air in the autoclave. (2) Continuously introduce nitrogen at room temperature to pressurize the reactor to 2.3 Mpa, then raise the temperature to 220 °C and stir the reaction for 6 h. (3) After the reaction is completed, naturally cool the reaction system to room temperature and release the pressure. Filter to remove the catalyst, and analyze the obtained organic phase by GC-MS.

[0044] Figure 1 This is the XRD pattern of the zinc-based catalyst Zn@Nx / NC prepared in Examples 1-4 of the present invention. The structure of the catalyst was analyzed using a powder X-ray diffraction (XRD) pattern. The Zn@Nx / NC catalyst shows two broad peaks at approximately 24° and 43°, corresponding to the (002) and (101) crystal planes of graphite carbon, respectively. This indicates that when the calcination temperature rises above 600 °C, the crystal structure of the intermediate is destroyed. Characteristic peaks of metallic zinc or zinc oxide are detected in the XRD pattern, and the content of zinc decreases as the calcination temperature increases.

[0045] Figure 2 This is the SEM image of the Zn-based catalyst Zn@Nx / NC prepared in Example 1 of the present invention. It can be seen that the catalyst exhibits an obvious blocky structure.

[0046] Figure 3TEM images and elemental mapping diagrams of the Zn-based catalyst Zn@Nx / NC prepared in Example 1 of the present invention show that the catalyst exhibits an obvious regular hexagonal structure.

[0047] Figure 4 Catalytic activity test diagrams of the Zn-based catalyst Zn@Nx / NC prepared in Examples 1-4 of the present invention show that the Zn@Nx / NC catalyst prepared in the present invention has good catalytic activity for HMF, the conversion rate of the reactant is greater than 98%, and the conversion rates of the catalysts in Examples 1, 3, and 4 reach 100%. Moreover, the yields of the products BHMF and DMF are relatively high. The BHMF yield of the catalysts in Examples 1 and 2 is high, and the DMF yield of the catalysts in Examples 3 and 4 is high. The yield of BHMF decreases with the increase of the calcination temperature, and the catalytic activity of DMF increases with the increase of the calcination temperature.

[0048] The present invention has been disclosed in the above preferred embodiments, but it is not intended to limit the present invention. Any technical solutions obtained by adopting equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. Application of high-activity Zn-based catalyst Zn@Nx / NC in catalytic transfer hydrogenation of 5-hydroxymethylfurfural, characterized in that: include: 5-Hydroxymethylfurfural, catalyst Zn@Nx / NC and reaction solvent are subjected to catalytic transfer hydrogenation reaction at set temperature and pressure; The catalyst Zn@Nx / NC is prepared according to the following method: Dissolve zinc nitrate hexahydrate and an auxiliary agent in a solvent to obtain a solution A, dissolve a template in a solvent to obtain a solution B, and add the solution B to the solution A under vigorous stirring, continue stirring to complete the reaction, and obtain a solid precipitate; The solid precipitate was calcined to obtain the Zn-based catalyst Zn@Nx / NC.

2. The use according to claim 1, characterized in that: The auxiliary agent is selected from one or more of gallium nitrate, zirconium nitrate, lanthanum nitrate and nickel nitrate.

3. The use according to claim 1, characterized in that: The template agent is selected from one or more of 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-isopropylimidazole and 2-propylimidazole.

4. The use according to claim 1, characterized in that: The solvents used in solution A and solution B are selected from one or more of methanol, ethanol, isopropanol and cyclohexane.

5. The use according to claim 1, characterized in that: The mass ratio of zinc nitrate hexahydrate, auxiliary agent and template agent is 1:1:1~1:1.5:

2.

6. The use according to claim 1, characterized in that: The solid precipitation calcination temperature is 600~900℃, and the calcination time is 2-5h.

7. The use according to claim 1, characterized in that: The molar ratio of 5-hydroxymethylfurfural, catalyst Zn@Nx / NC and reaction solvent is 1:1.5:5~1:2:

8.

8. The use according to claim 1, characterized in that: The reaction solvent in the catalytic transfer hydrogenation reaction is selected from one or more of methanol, ethanol, ethylene glycol and isopropanol.

9. The use according to claim 1, characterized in that: The reaction temperature of the catalytic transfer hydrogenation reaction is 150-230°C, the reaction pressure is 1-3Mpa, and the reaction time is 2-6h.

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