Composite high-entropy alloy catalyst as well as preparation method and application thereof

Abstract

The invention discloses a composite high-entropy alloy catalyst and a preparation method and application thereof.The catalyst comprises a carrier and metal components loaded on the carrier, the carrier is aluminum oxide, the metal components comprise composite precious metal and non-precious metal, the precious metal is one or more than two of platinum, gold, palladium, ruthenium and rhodium, and the non-precious metal is one or more than two of platinum, gold, palladium, ruthenium and rhodium. The non-noble metal is a combination of molybdenum, nickel, copper and manganese; the precious metal part is precious metal nanoparticles, and the rest part exists in the structure of the high-entropy alloy compound. The catalyst provided by the invention has high activity of a traditional supported catalyst and high stability and structural strength of HEA.

Description

Technical Field

[0001] The present invention relates to a composite high-entropy alloy catalyst, a preparation method thereof and an application thereof, and belongs to the field of catalyst synthesis and application. Background Art

[0002] Heterogeneous catalysts play an important role in the catalytic hydrogenation industrial system due to their convenient separation and excellent catalytic performance. Usually, in the process of heterogeneous catalytic reaction, there are various reaction interfaces such as liquid-solid, gas-solid, and gas-liquid-solid. This requires the catalyst to have stronger stability while maintaining high activity, so as to reduce the cost of the catalyst in the industrial application process. In the hydrogenation reaction, the commonly used supported catalysts at present include noble metal catalysts with Pt, Pd, Ru as active components and non-noble metal catalysts with Ni, Co, etc. as active components. Most of these catalysts will show phenomena such as loss of active components, aggregation of active sites, and fragmentation of carriers during the application process, which will lead to too low catalyst life and thus increase production costs. Therefore, developing a new type of catalyst with high generality, firmness and unchanged active components is a problem that the scientific research community and the industrial community continue to solve.

[0003] High-entropy Alloys (HEA) catalysts are an emerging material platform and have received extensive attention due to their unique structural characteristics such as high-entropy effect, lattice distortion, slow diffusion, high strength (wear resistance, high-temperature strength and thermal stability, high elongation, fatigue and fracture properties).

[0004] The mutual synergistic effect between multiple elements in HEA induces specific properties that cannot be achieved by single metal elements or intermetallic compounds. These properties endow HEA with outstanding structural stability and adjustable active sites at the same time. Through reasonable combination design, the multiple elements in the catalyst can synergistically promote each reaction step in the catalytic reaction, and at the same time, the high-entropy characteristics can greatly improve the catalyst stability. However, high-entropy alloys cannot show the same high activity as supported catalysts in the hydrogenation catalytic reaction. Therefore, developing a catalyst with strong structural stability of high-entropy metals, adjustable active sites and high activity of supported catalysts is of great significance for the industrial application of heterogeneous catalysts. Combining the high activity of traditional supported catalysts and the special properties of HEA can prepare a catalyst with high activity, high stability and high structural strength. At present, using the method of high-temperature smelting to alloy metals to prepare high-entropy alloy catalysts is a commonly used implementation scheme. However, if the temperature control is out of balance during the preparation process, one or several metals will undergo phase separation, resulting in the inability to form an alloy. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a composite high-entropy alloy catalyst, a preparation method thereof and an application thereof. The catalyst has high strength and good stability, the preparation method is simple, and the obtained catalyst has high activity in the hydrogenation reaction.

[0006] To solve the above technical problems, the present invention first discloses a composite high-entropy alloy catalyst, which includes a carrier and metal components supported on the carrier. The carrier is alumina, and the metal components include a composite of noble metals and non-noble metals. The noble metals are one or more of platinum, gold, palladium, ruthenium, and rhodium, and the non-noble metals are a combination of molybdenum, nickel, copper, and manganese; part of the noble metals are noble metal nanoparticles, and the rest exist in the structure of the high-entropy alloy compound; the noble metal nanoparticles have excellent catalytic activity.

[0007] Further, the total atomic mass of the non-noble metals does not exceed 15% of the mass of the alumina carrier; the atomic mass of the noble metals does not exceed 2% of the mass of the alumina carrier and does not exceed 20% of the total atomic mass of the non-noble metals; the molar amount of the noble metal nanoparticles does not exceed 60% of the molar amount of the noble metals used, and the proportion of the noble metals reduced to noble metal nanoparticles is controlled by controlling the reduction time and temperature during the catalyst preparation process.

[0008] Further, the molar ratio of molybdenum, nickel, copper, and manganese in the non-noble metals is 1:1:1:1.

[0009] The present invention also discloses a preparation method of the composite high-entropy alloy catalyst as described above, and the preparation method includes the following steps:

[0010] (1) Add precursors of a quantitative noble metal and non-noble metals to a mixed solution for dissolution, and after the dissolution is completed, perform ultrasonic treatment for 2 h to 5 h. The mixed solution contains water, ethanol, and organic substance B, and the organic substance B is one of DMF (N,N-dimethylformamide), DMA (N,N-dimethylacetamide), or cyclohexane;

[0011] (2) Transfer the solution after ultrasonic treatment in step (1) to a solvothermal reaction kettle, perform hydrothermal treatment at 50 °C to 70 °C for 12 h to 24 h, take it out after cooling to room temperature, and obtain an AMoNiCuMn catalyst sol, where A is a noble metal;

[0012] (3) Pour a quantitative alumina carrier into the AMoNiCuMn catalyst sol obtained in step (2), shake it in a sealed shaker for 12 h to 24 h to adsorb the catalyst sol in the pores of the alumina carrier, and then age the obtained substance at room temperature for 8 h to 24 h;

[0013] (4) Transfer the substance obtained in step (3) into a hydrothermal reaction kettle, add a certain amount of methanol and a certain amount of hydrogen peroxide, and perform hydrothermal treatment at 140 °C to 180 °C for 12 h to 24 h. After cooling to room temperature, take out the catalyst and wash it several times with water and ethanol respectively to obtain AMoNiCuMn / Al 2 O 3 catalyst. The hydrogen peroxide used in this step (3) can directly use the commercially available hydrogen peroxide solution with a mass concentration of 30%;

[0014] (5) Place the AMoNiCuMn / Al 2 O 3 catalyst obtained in step (4) into a reduction furnace, and under the condition of hydrogen, heat it up to 130 °C to 160 °C and reduce it for 1 h to 4 h. The heating rate is: 2 °C / min to 4 °C / min, and the gas flow rate is controlled at 10 mL / min to 100 mL / min to obtain A / AMoNiCuMn / Al 2 O 3 catalyst.

[0015] Further, among the noble metals, the precursor of platinum is one of chloroplatinic acid, platinum nitrate, dichlorotetraammineplatinum, and tetraammineplatinum nitrate; the precursor of gold is chloroauric acid; the precursor of palladium is one of palladium nitrate, palladium chloride, palladium acetate, sodium palladium chloride, and potassium palladium chloride; the precursor of ruthenium is one of ruthenium trichloride, ruthenium acetylacetonate, and ruthenium nitrate; the precursor of rhodium is one of rhodium trichloride and rhodium acetylacetonate.

[0016] Further, among the non-noble metals, the precursor of molybdenum is ammonium molybdate; the precursor of nickel is nickel nitrate or nickel acetate; the precursor of copper is copper nitrate; the precursor of manganese is manganese nitrate.

[0017] Further, in the mixed solution used in step (1), the mass ratio of water is 5% to 20%, the mass ratio of ethanol is 10% to 30%, and the rest is organic matter B. The total mass of this mixed solution is 150% to 180% of the mass of the alumina support used in step (3). The actual ratio and type selection of water, ethanol, and organic matter B in the mixed solution are determined by the solubility of the metal precursors. For example: when using nitrate precursors, the amount of water used is about 10% of the total mass of the mixed solution, and the amount of ethanol used is about 15% of the total mass of the mixed solution; the organic solvent B can be selected as one or several of DMF, DMA, and cyclohexane according to the different noble metal precursors. For example: for the two precursors of ruthenium acetylacetonate and rhodium acetylacetonate, cyclohexane is preferably selected as the solvent.

[0018] Further, in step (4), the mass ratio of the methanol to the hydrogen peroxide is 10:0.1 to 1, and the total mass of the methanol and the hydrogen peroxide is 130% to 180% of the mass of the alumina support used in step (3).

[0019] The present invention also discloses the application of the composite high-entropy alloy catalyst as described above or the composite high-entropy alloy catalyst obtained by the preparation method as described above in a hydrogenation reaction.

[0020] Furthermore, the hydrogenation reaction is applicable to one of a fixed bed, a packed bed, and a trickle bed.

[0021] After preparing the metal precursor into a gel solution AMoNiCuMn, the present invention uses an impregnation method to load the AMoNiCuMn gel on an Al 2 O 3 support. After aging, it is heated using a solvent thermal reactor, and the AMoNiCuMn / Al 2 O 3 catalyst is prepared by a hydrothermal method. Then, the prepared catalyst is reduced under H 2 conditions. During this reduction process, a part of the noble metal A grows in-situ into A nanoparticles, thereby obtaining the composite high-entropy alloy catalyst A / AMoNiCuMn / Al 2 O 3 . The composite high-entropy alloy catalyst A / AMoNiCuMn / Al 2 O 3 has the characteristics of high activity of a supported catalyst and high stability of a high-entropy catalyst. The preparation process is simple, with less three wastes and low cost. The catalyst has a wide application range and can exhibit excellent catalytic performance in reactions such as nitro, ester group, carbonyl, carbon-carbon double bond, nitrile group, amide hydrogenation, hydrogenation debenzylation, reductive amination, and hydrogenation dehalogenation prevention.

[0022] Specifically, the present invention has the following advantages:

[0023] 1. Based on the commonly used particulate alumina support platform, the present invention loads the A / AMoNiCuMn composite high-entropy metal catalyst on the alumina support. The metals in the catalyst can be adjusted according to the reaction requirements, thereby adapting to the preparation of different types of catalysts and being flexibly applied to different reactions, which can significantly expand the use range of the composite high-entropy alloy catalyst.

[0024] 2. The composite catalyst of the present invention combines the high activity of traditional supported catalysts, the high stability and structural strength of HEA. Through reasonable combination design, the multi-element synergy can make the electronic state on the catalyst surface show specificity, so that in certain specific reactions, the reaction process can be controlled by adjusting the adsorption and desorption rates of the catalyst for reactants, intermediates and products, thereby greatly improving the catalytic hydrogenation selectivity and flexibly controlling the product distribution. By means of low-temperature reduction, a small amount of precious metal grows in-situ from the high-entropy alloy catalyst into metal nanoparticles, making the catalyst exhibit the same or even higher catalytic activity as the same kind of supported catalysts. The mutual induction of multiple metal elements in the high-entropy alloy limits the number of precious metals reduced to metal nanoparticles and restricts the movement of metal nanoparticles, so that the metal nanoparticles have extremely high stability and are not prone to agglomeration and loss phenomena. Description of the Drawings

[0025] Figure 1 Figure for comparing the catalyst stability and product selectivity of the two catalysts in Example 1 and Comparative Example 1 in the reaction of hydrogenating m-dinitrobenzene to prepare m-phenylenediamine;

[0026] Figure 2 TEM transmission electron micrograph of the Pt / PtMoNiCuMn catalyst without alumina support obtained in Example 1;

[0027] Figure 3 For the Pt / PtMoNiCuMn / Al obtained in step (5) of Example 1 2 O 3 TEM transmission electron micrograph of the catalyst;

[0028] Figure 4 For the Pt / PtMoNiCuMn / Al obtained in step (5) of Example 1 2 O 3 X-ray photoelectron spectroscopy (XPS) of the Pt element of the catalyst. Detailed Embodiments

[0029] The present invention will be further explained below in conjunction with the embodiments. The following embodiments are only used to illustrate the present invention, but do not limit the scope of implementation of the present invention.

[0030] Example 1

[0031] (1) At room temperature, 0.172 g of platinum diamine tetrachloride, 0.392 g of ammonium molybdate, 0.582 g of nickel nitrate hexahydrate, 0.3751 g of copper nitrate and 0.358 g of manganese nitrate were added to a mixed solution composed of 3 g of water, 4 g of ethanol and 8 g of DMA. After dissolution, ultrasonic treatment was carried out at room temperature for 2 h.

[0032] (2) Transfer the ultrasonically treated solution to a solvothermal reactor, perform hydrothermal treatment at 50 °C for 24 h, take it out after cooling to room temperature to obtain the PtMoNiCuMn catalyst sol, and this PtMoNiCuMn catalyst sol is the high-entropy substance PtMoNiCuMn.

[0033] (3) Pour 10 g of alumina support into the PtMoNiCuMn catalyst sol, seal it and place it in a shaker for 12 h to allow the catalyst sol to adsorb in the pores of the alumina support, and then age it at room temperature for 12 h.

[0034] (4) Transfer the aged catalyst to a solvothermal reactor, add 15 g of methanol and 1 g of hydrogen peroxide solution with a mass concentration of 30%, and perform hydrothermal treatment at 150 °C for 24 h. Take out the catalyst after cooling to room temperature and wash it 3 times with water and ethanol respectively to obtain the PtMoNiCuMn / Al 2 O 3 catalyst.

[0035] (5) Place the PtMoNiCuMn / Al 2 O 3 catalyst in a tube furnace, under hydrogen conditions, heat it up to 150 °C and reduce it for 2 h, with a heating rate of 2 °C / min and the gas flow rate controlled at 30 mL / min to obtain the Pt / PtMoNiCuMn / Al 2 O 3 catalyst, and its TEM transmission electron micrograph is as shown in Figure 3 The high-entropy substance is successfully attached to the surface of the alumina. The mass of platinum loading is 1% of the mass of the support. The X-ray photoelectron spectroscopy (XPS) of the Pt element of this Pt / PtMoNiCuMn / Al 2 O 3 catalyst is as shown in Figure 4 Among them, the valence states of Pt are Pt 0 , Pt 2+ , and Pt 4+ in a coexisting state, and among them, Pt 0 (catalytically active Pt nanoparticles) accounts for about 40% of the Pt usage in this catalyst in terms of molar ratio.

[0036] Test the nitrohydrogenation activity of the catalyst. Weigh 2.5 g of the above-mentioned Pt / PtMoNiCuMn / Al 2 O 3 catalyst and load it into a micro-packed bed reactor. Raise the pressure in the reactor to 1.0 MPa and wait for the system to stabilize. Pump the 10% m-dinitrobenzene methanol solution into the reactor through a high-pressure pump, adjust the liquid flow rate to 1 mL / min, take a sample for detection 1 hour after starting the reaction, and the measured conversion rate is 100% and the selectivity is 98.7%.

[0037] In Example 1, in order to test the morphological characteristics of the high-entropy material prepared by this method, the same steps (1) and (2) were operated. The obtained high-entropy material PtMoNiCuMn was placed in a tubular furnace for reduction. Under hydrogen conditions, the temperature was raised from room temperature to 150 °C and reduced for 2 h, and the heating rate was 2 °C / min. The gas flow rate was controlled at 30 mL / min. The Pt / PtMoNiCuMn catalyst without an alumina support could be obtained. The TEM image of this catalyst is as Figure 2 shown.

[0038] Example 2

[0039] (1) At room temperature, 0.344 g of platinum diamine dichloride, 0.392 g of ammonium molybdate, 0.582 g of nickel nitrate hexahydrate, 0.3751 g of copper nitrate and 0.358 g of manganese nitrate were added to a mixed solution composed of 3 g of water, 4 g of ethanol and 8 g of DMA. After complete dissolution, ultrasonic treatment was carried out at room temperature for 2 h.

[0040] (2) The ultrasonically treated solution was transferred to a hydrothermal reaction kettle, and hydrothermally treated at 50 °C for 24 h. After cooling to room temperature, it was taken out to obtain a PtMoNiCuMn catalyst sol.

[0041] (3) 10 g of an alumina support was poured into the PtMoNiCuMn catalyst sol, sealed and shaken in a shaker for 12 h to allow the catalyst sol to adsorb in the pores of the alumina support, and then aged at room temperature for 12 h.

[0042] (4) The aged catalyst was transferred to a hydrothermal reaction kettle, 15 g of methanol and 1 g of a 30% hydrogen peroxide aqueous solution by mass were added, and hydrothermally treated at 150 °C for 24 h. After cooling to room temperature, the catalyst was taken out and washed 3 times with water and ethanol respectively to obtain PtMoNiCuMn / Al 2 O 3 catalyst.

[0043] (5) The PtMoNiCuMn / Al 2 O 3 catalyst was placed in a tubular furnace. Under hydrogen conditions, it was heated to 150 °C and reduced for 2 h, and the heating rate was 2 °C / min. The gas flow rate was controlled at 30 mL / min to obtain Pt / PtMoNiCuMn / Al 2 O 3 catalyst. The mass of platinum loaded was 2% of the mass of the support.

[0044] To test the nitro-hydrogenation activity of the catalyst, weigh the above-mentioned Pt / PtMoNiCuMn / Al 2 O 32.5 g of the catalyst was loaded into a micro-packed bed reactor. The pressure in the reactor was raised to 1.0 MPa and the system was waited to be stable. A solution of m-dinitrobenzyl alcohol with a mass concentration of 10% was pumped into the reactor by a high-pressure pump, the liquid flow rate was adjusted to 1 mL / min, and samples were taken for detection 1 hour after the start of the reaction. The conversion rate was 100% and the selectivity was 98.2%.

[0045] Example 3

[0046] (1) At room temperature, 0.248 g of palladium nitrate, 0.392 g of ammonium molybdate, 0.582 g of nickel nitrate hexahydrate, 0.3751 g of copper nitrate and 0.358 g of manganese nitrate were added to a mixed solution composed of 3 g of water, 4.5 g of ethanol and 8.5 g of DMA. After complete dissolution, ultrasonic treatment was carried out at room temperature for 2 h.

[0047] (2) The ultrasonic-treated solution was transferred to a solvothermal reaction kettle, and hydrothermal treatment was carried out at 50 °C for 24 h. After cooling to room temperature, it was taken out to obtain a PdMoNiCuMn catalyst sol.

[0048] (3) 10 g of an alumina support was poured into the PdMoNiCuMn catalyst sol, and after sealing, it was placed in a shaker and shaken for 12 h to adsorb the catalyst sol in the pores of the alumina support, and then aged at room temperature for 12 h.

[0049] (4) The aged catalyst was transferred to a solvothermal reaction kettle, 15 g of methanol and 1.5 g of a hydrogen peroxide solution with a mass concentration of 30% were added, and hydrothermal treatment was carried out at 150 °C for 24 h. After cooling to room temperature, the catalyst was taken out and washed 3 times with water and ethanol respectively to obtain a PdMoNiCuMn / Al 2 O 3 catalyst.

[0050] (5) The PdMoNiCuMn / Al 2 O 3 catalyst was placed in a tubular furnace and reduced at 150 °C for 2 h under hydrogen conditions. The heating rate was: 2 °C / min, and the gas flow rate was controlled at 30 mL / min to obtain a Pd / PdMoNiCuMn / Al 2 O 3 catalyst. The mass of palladium loaded was 1% of the mass of the support.

[0051] The nitro-hydrogenation activity of the catalyst was tested. Weighed the above Pd / PdMoNiCuMn / Al 2 O 32.5 g of the catalyst was loaded into a micro-packed bed reactor. The pressure inside the reactor was raised to 1.0 MPa and the system was waited to be stable. A meta-dinitrobenzyl alcohol solution with a mass concentration of 10% was pumped into the reactor by a high-pressure pump. The liquid flow rate was adjusted to 1 mL / min. Samples were taken for detection 1 hour after the start of the reaction. The conversion rate was 100% and the selectivity was 96.7%.

[0052] The olefin hydrogenation activity of the catalyst was tested. Weighed the above Pd / PdMoNiCuMn / Al 2 O 3 2.5 g of the catalyst was loaded into a micro-packed bed reactor. The pressure inside the reactor was raised to 1.0 MPa and the system was waited to be stable. A 2,3-dimethyl-1,3-butadiene methanol solution with a mass concentration of 10% was pumped into the reactor by a high-pressure pump. The liquid flow rate was adjusted to 1 mL / min. Samples were taken for detection 1 hour after the start of the reaction. The conversion rate was 88.6% and the selectivity was 94.7%.

[0053] Example 4

[0054] (1) At room temperature, 0.27 g of ruthenium chloride, 0.392 g of ammonium molybdate, 0.582 g of nickel nitrate hexahydrate, 0.3751 g of copper nitrate and 0.358 g of manganese nitrate were added to a mixed solution composed of 2 g of water, 4.5 g of ethanol and 9 g of DMA. After dissolution, ultrasonic treatment was carried out for 2 h at room temperature.

[0055] (2) The ultrasonic-treated solution was transferred to a solvothermal reaction kettle and hydrothermally treated at 50 °C for 24 h. After cooling to room temperature, it was taken out to obtain a RuMoNiCuMn catalyst sol.

[0056] (3) 10 g of alumina support was poured into the RuMoNiCuMn catalyst sol. After sealing, it was placed in a shaker and shaken for 12 h to make the catalyst sol adsorbed in the pores of the alumina support. Then it was aged for 12 h at room temperature.

[0057] (4) The aged catalyst was transferred to a solvothermal reaction kettle, 15 g of methanol and 1 g of hydrogen peroxide solution with a mass concentration of 30% were added, and it was hydrothermally treated at 150 °C for 24 h. After cooling to room temperature, the catalyst was taken out and washed 3 times with water and ethanol respectively to obtain RuMoNiCuMn / Al 2 O 3 catalyst.

[0058] (5) The RuMoNiCuMn / Al 2 O 3 catalyst was placed in a tube furnace and reduced at 150 °C for 2 h under hydrogen. The heating rate was: 2 °C / min, and the gas flow rate was controlled at 30 mL / min to obtain Ru / RuMoNiCuMn / Al 2O 3 Catalyst. The mass of ruthenium loading is 1% of the mass of the support.

[0059] Testing the nitro-hydrogenation activity of the catalyst: Weigh 2.5 g of the above-mentioned Ru / RuMoNiCuMn / Al 2 O 3 catalyst and load it into a micro-packed bed reactor. Raise the pressure in the reactor to 1.0 MPa and wait for the system to stabilize. Then pump a 10% m-dinitrobenzene methanol solution into the reactor through a high-pressure pump, adjust the liquid flow rate to 1 mL / min, take samples for detection 1 hour after the start of the reaction, with a conversion rate of 100% and a selectivity of 97.6%.

[0060] Testing the toluene-hydrogenation activity of the catalyst: Weigh 2.5 g of the above-mentioned Ru / RuMoNiCuMn / Al 2 O 3 catalyst and load it into a micro-packed bed reactor. Raise the pressure in the reactor to 1.0 MPa and wait for the system to stabilize. Then pump a 10% toluene methanol solution into the reactor through a high-pressure pump, adjust the liquid flow rate to 1 mL / min, take samples for detection 1 hour after the start of the reaction, with a conversion rate of 100% and a selectivity of 99.4%.

[0061] Example 5

[0062] (1) At room temperature, add 0.389 g of rhodium acetylacetonate, 0.392 g of ammonium molybdate, 0.582 g of nickel nitrate hexahydrate, 0.3751 g of copper nitrate, and 0.358 g of manganese nitrate to a mixed solution composed of 3 g of water, 4.5 g of ethanol, and 7.5 g of cyclohexane. After complete dissolution, ultrasonicate for 2 h at room temperature.

[0063] (2) Transfer the ultrasonically treated solution to a solvothermal reaction kettle and perform hydrothermal treatment at 50 °C for 24 h. After cooling to room temperature, take it out to obtain a RhMoNiCuMn catalyst sol.

[0064] (3) Pour 10 g of alumina support into the RhMoNiCuMn catalyst sol, seal it, and place it in a shaker for shaking for 12 h to allow the catalyst sol to adsorb in the pores of the alumina support, and then age it for 12 h at room temperature.

[0065] (4) Transfer the aged catalyst to a solvothermal reaction kettle, add 15 g of methanol and 1.5 g of a 30% hydrogen peroxide solution by mass, and perform hydrothermal treatment at 150 °C for 24 h. After cooling to room temperature, take out the catalyst and wash it 3 times with water and ethanol respectively to obtain RhMoNiCuMn / Al 2 O 3 catalyst.

[0066] (5) Transfer the RhMoNiCuMn / Al2 O 3 The catalyst was placed in a tubular furnace and reduced at 150 °C for 2 h under hydrogen atmosphere. The heating rate was 2 °C / min and the gas flow rate was controlled at 30 mL / min to obtain Rh / RhMoNiCuMn / Al 2 O 3 catalyst. The mass of rhodium loaded was 1% of the mass of the support.

[0067] The hydrogenation activity of the catalyst was tested. 2.5 g of the above-mentioned Rh / RhMoNiCuMn / Al 2 O 3 catalyst was weighed and loaded into a micro-packed bed reactor. The pressure in the reactor was raised to 1.0 MPa and waited for the system to stabilize. A mixed solution of 10% benzonitrile, 1.5% ammonia methanol and 88.5% methanol was pumped into the reactor through a high-pressure pump. The liquid flow rate was adjusted to 1 mL / min. Samples were taken for detection 1 hour after the start of the reaction, with a conversion rate of 94.8% and a selectivity of 97.3%.

[0068] Example 6

[0069] (1) At room temperature, 0.496 g of palladium nitrate, 0.392 g of ammonium molybdate, 0.582 g of nickel nitrate hexahydrate, 0.3751 g of copper nitrate and 0.358 g of manganese nitrate were added to a mixed solution composed of 2.5 g of water, 4 g of ethanol and 8.5 g of DMA. After dissolution, ultrasonic treatment was carried out at room temperature for 2 h.

[0070] (2) The ultrasonic-treated solution was transferred to a solvothermal reaction kettle and hydrothermally treated at 50 °C for 24 h. After cooling to room temperature, it was taken out to obtain a PdMoNiCuMn catalyst sol.

[0071] (3) 10 g of alumina support was poured into the PdMoNiCuMn catalyst sol. After sealing, it was placed in a shaker and shaken for 12 h to adsorb the catalyst sol in the pores of the alumina support. Then it was aged at room temperature for 12 h.

[0072] (4) The aged catalyst was transferred to a solvothermal reaction kettle, 15 g of methanol and 1.5 g of 30% hydrogen peroxide solution by mass were added, and it was hydrothermally treated at 150 °C for 24 h. After cooling to room temperature, the catalyst was taken out and washed 3 times with water and ethanol respectively to obtain PdMoNiCuMn / Al 2 O 3 catalyst.

[0073] (5) PdMoNiCuMn / Al 2 O 3The catalyst was placed in a tubular furnace and reduced at 150 °C for 2 h under hydrogen conditions. The heating rate was 2 °C / min, and the gas flow rate was controlled at 30 mL / min to obtain Pd / PdMoNiCuMn / Al 2 O 3 catalyst. The mass of palladium loaded was 2% of the mass of the support.

[0074] The hydrogenation debenzylation activity of the catalyst was tested. 2.5 g of the above Pd / PdMoNiCuMn / Al 2 O 3 catalyst was weighed and loaded into a micro-packed bed reactor. The pressure in the reactor was raised to 1.0 MPa and waited for the system to stabilize. A 10% methylbenzylamine methanol solution was pumped into the reactor through a high-pressure pump, and the liquid flow rate was adjusted to 1 mL / min. Samples were taken for detection 1 hour after the start of the reaction, with a conversion rate of 86.2% and a selectivity of 98.1%.

[0075] Comparative Example 1

[0076] At room temperature, 0.172 g of platinum tetramine dichloride was dissolved in 16 g of water, and then the metal precursor was loaded onto 10 g of alumina support by equal-volume impregnation. After standing for 12 h, the catalyst was dried in an oven at 80 °C for 12 h. The catalyst was placed in a tubular furnace and reduced at 150 °C for 2 h under hydrogen conditions. The heating rate was 2 °C / min, and the gas flow rate was controlled at 30 mL / min to obtain 1% Pt / Al 2 O 3 catalyst. The mass of platinum loaded was 1% of the mass of the support.

[0077] The nitrohydrogenation activity of the catalyst was tested. 2.5 g of the above 1% Pt / Al 2 O 3 catalyst was weighed and loaded into a micro-packed bed reactor. The pressure in the reactor was raised to 1.0 MPa and waited for the system to stabilize. A 10% m-dinitrobenzene methanol solution was pumped into the reactor through a high-pressure pump, and the liquid flow rate was adjusted to 1 mL / min. Samples were taken for detection 1 hour after the start of the reaction, with a conversion rate of 84.5% and a selectivity of 77.1%.

[0078] The stability and product selectivity of the catalyst obtained in Example 1 and the catalyst obtained in Comparative Example 1 (prepared by the traditional impregnation method) in the reaction of preparing m-phenylenediamine from m-dinitrobenzene were as Figure 1 shown. The catalyst of the present invention has higher activity and higher stability than the catalyst prepared by the traditional impregnation method.

[0079] Comparative Example 2

[0080] At room temperature, 0.248 g of palladium nitrate was dissolved in 16 g of water. Then, the metal precursor was loaded onto 10 g of alumina support by equal-volume impregnation. After standing for 12 h, the catalyst was dried in an oven at 80 °C for 12 h. The catalyst was placed in a tubular furnace and reduced at 150 °C for 2 h under hydrogen atmosphere. The heating rate was 2 °C / min, and the gas flow rate was controlled at 30 mL / min to obtain 1% Pd / Al 2 O 3 catalyst, and the mass of palladium loaded was 1% of the mass of the support.

[0081] The nitro-hydrogenation activity of the catalyst was tested. 2.5 g of the above-mentioned 1% Pd / Al 2 O 3 catalyst was weighed and loaded into a micro-packed bed reactor. The pressure in the reactor was raised to 1.0 MPa and waited for the system to stabilize. A 10% m-dinitrobenzene methanol solution was pumped into the reactor through a high-pressure pump, and the liquid flow rate was adjusted to 1 mL / min. Samples were taken for detection 1 hour after the start of the reaction, with a conversion rate of 75.4% and a selectivity of 81.3%.

[0082] The olefin-hydrogenation activity of the catalyst was tested. 2.5 g of the above-mentioned 1% Pd / Al 2 O 3 catalyst was weighed and loaded into a micro-packed bed reactor. The pressure in the reactor was raised to 1.0 MPa and waited for the system to stabilize. A 10% 2,3-dimethyl-1,3-butadiene methanol solution was pumped into the reactor through a high-pressure pump, and the liquid flow rate was adjusted to 1 mL / min. The conversion rate was 56.4% and the selectivity was 79.3%.

[0083] Comparative Example 3

[0084] At room temperature, 0.389 g of rhodium acetylacetonate was dissolved in 14 g of water and 2 g of cyclohexane. Then, the metal precursor was loaded onto 10 g of alumina support by equal-volume impregnation. After standing for 12 h, the catalyst was dried in an oven at 80 °C for 12 h. The catalyst was placed in a tubular furnace and reduced at 150 °C for 2 h under hydrogen atmosphere. The heating rate was 2 °C / min, and the gas flow rate was controlled at 30 mL / min to obtain 1% Rh / Al 2 O 3 catalyst, and the mass of rhodium loaded was 1% of the mass of the support.

[0085] The benzonitrile-hydrogenation activity of the catalyst was tested. 2.5 g of the above-mentioned 1% Rh / Al 2 O 32.5 g of the catalyst was loaded into a micro-packed bed reactor. The pressure in the reactor was increased to 1.0 MPa. After waiting for the system to stabilize, a mixed solution with a mass concentration of 10% benzonitrile, 1.5% ammonia methanol, and 88.5% methanol was pumped into the reactor through a high-pressure pump. The liquid flow rate was adjusted to 1 mL / min. Samples were taken for detection 1 hour after the start of the reaction, with a conversion rate of 74.6% and a selectivity of 84.1%.

[0086] Comparative Example 4

[0087] At room temperature, 0.27 g of ruthenium chloride was dissolved in 16 g of water. Then, the metal precursor was loaded onto 10 g of an alumina support by equal-volume impregnation. After standing for 12 h, the catalyst was dried in an 80 °C oven for 12 h. The catalyst was placed in a tube furnace and reduced at 150 °C for 2 h under hydrogen conditions. The heating rate was 2 °C / min, and the gas flow rate was controlled at 30 mL / min to obtain 1% Ru / Al 2 O 3 catalyst, and the mass of ruthenium loaded was 1% of the mass of the support.

[0088] The toluene hydrogenation activity of the catalyst was tested: Weighed 2.5 g of the above-mentioned 1% Ru / Al 2 O 3 catalyst and loaded it into a micro-packed bed reactor. The pressure in the reactor was increased to 1.0 MPa. After waiting for the system to stabilize, a toluene methanol solution with a mass concentration of 10% was pumped into the reactor through a high-pressure pump. The liquid flow rate was adjusted to 1 mL / min. Samples were taken for detection 1 hour after the start of the reaction, with a conversion rate of 81.7% and a selectivity of 95.3%.

[0089] Comparative Example 5

[0090] At room temperature, 0.496 g of palladium nitrate was dissolved in 16 g of water. Then, the metal precursor was loaded onto 10 g of an alumina support by equal-volume impregnation. After standing for 12 h, the catalyst was dried in an 80 °C oven for 12 h. The catalyst was placed in a tube furnace and reduced at 150 °C for 2 h under hydrogen conditions. The heating rate was 2 °C / min, and the gas flow rate was controlled at 30 mL / min to obtain 2% Pd / Al 2 O 3 catalyst, and the mass of palladium loaded was 2% of the mass of the support.

[0091] The hydrogenation debenzylation activity of the catalyst was tested. Weighed 2% Pd / Al 2 O 32.5 g of the catalyst was loaded into a micro-packed bed reactor. The pressure inside the reactor was raised to 1.0 MPa. After waiting for the system to stabilize, a methanol solution of methylbenzylamine with a mass concentration of 10% was pumped into the reactor through a high-pressure pump. The liquid flow rate was adjusted to 1 mL / min. Samples were taken for detection 1 hour after the start of the reaction, with a conversion rate of 55.7% and a selectivity of 94.4%.

[0092] For the comparison of the activities of the catalysts obtained in Examples 1-6 and Comparative Examples 1-5 in each hydrogenation reaction, see Tables 1-5.

[0093] Table 1. Comparison of the hydrogenation activities of m-dinitrobenzene between examples and comparative examples

[0094]

[0095] Table 2. Comparison of the hydrogenation activities of benzonitrile between examples and comparative examples

[0096]

[0097]

[0098] Table 3. Comparison of the hydrogenation activities of 2,3-dimethyl-1,3-butadiene between examples and comparative examples

[0099]

[0100] Table 4. Comparison of the hydrogenation activities of toluene between examples and comparative examples

[0101]

[0102] Table 5. Comparison of the hydrogenation debenzylation activities of methylbenzylamine between examples and comparative examples

[0103]

Claims

1. A composite high entropy alloy catalyst, characterized in that: The catalyst comprises a carrier and a metal component loaded on the carrier, wherein the carrier is aluminum oxide, the metal component comprises a composite precious metal and non-precious metal, the precious metal is one or more of platinum, gold, palladium, ruthenium and rhodium, and the non-precious metal is a combination of molybdenum, nickel, copper and manganese; the precious metal part is precious metal nanoparticles, and the rest exists in the structure of a high entropy alloy compound.

2. The composite high entropy alloy catalyst according to claim 1, characterized in that: The total atomic mass of the non-precious metals does not exceed 15% of the mass of the alumina carrier; the atomic mass of the precious metals does not exceed 2% of the mass of the alumina carrier, and does not exceed 20% of the total atomic mass of the non-precious metals; the molar amount of the precious metal nanoparticles does not exceed 60% of the molar amount of the precious metal.

3. The composite high entropy alloy catalyst according to claim 2, characterized in that: The molar ratio of molybdenum, nickel, copper and manganese in the non-precious metals is 1:1:1:

1.

4. A method for preparing a composite high entropy alloy catalyst according to any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps: (1) adding a certain amount of precious metal and non-precious metal precursors to a mixed solution for dissolution, and performing ultrasonic treatment for 2 h to 5 h after the dissolution is completed, wherein the mixed solution contains water, ethanol and an organic substance B, wherein the organic substance B is one of DMF, DMA or cyclohexane; (2) transferring the solution after ultrasonic treatment in step (1) to a solvent thermal reactor, hydrothermally treating it at 50° C. to 70° C. for 12 h to 24 h, cooling it to room temperature and then taking it out to obtain an AMoNiCuMn catalyst sol, wherein A is a precious metal; (3) pouring a certain amount of alumina carrier into the AMoNiCuMn catalyst sol obtained in step (2), shaking in a sealed shaker for 12 h to 24 h, and then aging the obtained material at room temperature for 8 h to 24 h; (4) transferring the substance obtained in step (3) to a solvent thermal reactor, adding a certain amount of methanol and a certain amount of hydrogen peroxide, and subjecting the reaction mixture to a hydrothermal treatment at 140° C. to 180° C. for 12 h to 24 h. After cooling to room temperature, taking out the catalyst and washing it several times with water and ethanol, respectively, to obtain an AMoNiCuMn / Al2O3 catalyst; (5) placing the AMoNiCuMn / Al2O3 catalyst obtained in step (4) in a reduction furnace, heating to 130°C to 160°C for reduction under hydrogen conditions for 1h to 4h, with a heating rate of 2°C / min to 4°C / min and a gas flow rate controlled at 10mL / min to 100mL / min to obtain an A / AMoNiCuMn / Al2O3 catalyst.

5. The method for preparing a composite high entropy alloy catalyst according to claim 4, characterized in that: Among the precious metals, the precursor of platinum is one of chloroplatinic acid, platinum nitrate, tetraamineplatinum dichloride, and tetraamineplatinum nitrate; the precursor of gold is chloroauric acid; the precursor of palladium is one of palladium nitrate, chloropalladic acid, palladium acetate, sodium chloropalladate, and potassium chloropalladate; the precursor of ruthenium is one of ruthenium trichloride, ruthenium acetylacetonate, and ruthenium nitrate; the precursor of rhodium is one of rhodium trichloride and rhodium acetylacetonate.

6. The method for preparing a composite high entropy alloy catalyst according to claim 4, characterized in that: Among non-precious metals, the precursor of molybdenum is ammonium molybdate; the precursor of nickel is nickel nitrate or nickel acetate; the precursor of copper is copper nitrate; and the precursor of manganese is manganese nitrate.

7. The method for preparing a composite high entropy alloy catalyst according to claim 4, characterized in that: The mass proportion of water in the mixed solution used in step (1) is 5% to 20%, the mass proportion of ethanol is 10% to 30%, and the rest is organic matter B. The total mass of the mixed solution is 150% to 180% of the mass of the alumina carrier used in step (3).

8. The method for preparing a composite high entropy alloy catalyst according to claim 4, characterized in that: In step (4), the mass ratio of methanol to hydrogen peroxide is 10:0.1-1, and the total mass of methanol and hydrogen peroxide is 130%-180% of the mass of the alumina carrier used in step (3).

9. Use of the composite high entropy alloy catalyst according to any one of claims 1 to 3 or the composite high entropy alloy catalyst obtained by the preparation method according to any one of claims 4 to 8 in a hydrogenation reaction.

10. The use according to claim 9, characterized in that: The hydrogenation reaction is applicable to one of a fixed bed, a packed bed and a trickle bed.

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