Preparation method of Ru metal alkene catalyst with controllable layer thickness and application of Ru metal alkene catalyst in distributed ammonia synthesis

Abstract

The invention provides a layer-thickness-controllable Ru metal alkene catalyst, a preparation method thereof and application of the layer-thickness-controllable Ru metal alkene catalyst in distributed ammonia synthesis. The preparation method specifically comprises the following steps: (1) preparing an oxide carrier; (2) carrying out high-temperature reaction on the Ru precursor solution to obtain Ru metal alkene; and (3) loading the Ru metal alkene obtained in the step (2) on the carrier in the step (1), dipping in an auxiliary agent, and reducing to obtain the Ru metal alkene catalyst. The layer-thickness-controllable Ru metal alkene catalyst provided by the invention has excellent ammonia synthesis catalytic performance and stability under mild conditions. The catalyst provided by the invention is simple in preparation method and convenient to operate, so that the catalyst shows a good application prospect in synthesis ammonia reaction.

Description

Technical Field

[0001] The present invention relates to the field of catalyst material preparation, and specifically relates to a preparation method of a high-performance Ru metalene catalyst and its application in distributed ammonia synthesis. Background Art

[0002] Ammonia (NH 3 ) is one of the important raw materials for the production of fertilizers and other nitrogen-containing chemicals. Although nitrogen gas (N 2 ) in the atmosphere accounts for up to 78.1%, due to its extremely high bond energy (941 kJ mol -1 ), directly using N 2 to produce NH 3 is a major challenge. Industrial ammonia synthesis mainly uses the traditional Haber-Bosch process, which uses N 2 and H 2 as raw materials and proceeds under high temperature and high pressure (400~600 °C, 20~40 MPa) with the help of an iron-based catalyst. Due to the wide application of NH 3 in various fields, the global demand for NH 3 continues to increase. Currently, the annual global production of NH 3 is approximately 162 million tons, and the energy consumption of the ammonia synthesis industry each year accounts for about 1~2% of the global total energy consumption. Moreover, for every 1 ton of NH 3 produced, approximately 1.5 tons of carbon dioxide (CO 2 ) will be generated. If the high energy consumption in the ammonia synthesis process can be reduced, the production efficiency can be improved, and the carbon emissions in the ammonia synthesis industry can be reduced or even eliminated, it is of great significance for solving the current global energy crisis and global greenhouse effect. The key lies in the design and preparation of mild ammonia synthesis catalysts. Summary of the Invention

[0003] Ammonia synthesis is a structure-sensitive reaction, and subtle changes in structure, morphology, and electronic properties will have a greater impact on catalytic activity. For Ru-based catalysts, the B 5 site is the main active site for the ammonia synthesis reaction, which is affected by the morphology, structure, and size of Ru nanoparticles. Compared with traditional Ru nanoparticles, Ru metalene (a two-dimensional metal material with a single atomic layer or a few atomic layers thick) can expose more B 5On the one hand, the active sites improve the utilization efficiency of atoms; on the other hand, due to the special two-dimensional confinement effect of the metalene structure, it can regulate the electronic structure of the catalyst and improve the adsorption and activation ability of reactant molecules. The present invention proposes a simple and efficient method for preparing Ru metalene, and by changing the synthesis conditions, the regulation of the layer thickness of Ru metalene can be achieved. The results show that the ammonia synthesis performance of the Ru metalene catalyst is significantly superior to that of the traditional Ru nanoparticle catalyst and remains stable in the long-term activity test. The present invention has very important guiding significance for the development of more efficient Ru-based catalysts under mild conditions.

[0004] The purpose of the present invention is to provide a method for preparing a Ru metalene catalyst with controllable layer thickness for mild ammonia synthesis.

[0005] To achieve the above object, the present invention adopts the following technical solutions: A method for preparing a Ru metalene catalyst with controllable layer thickness for mild ammonia synthesis, comprising the following steps: (1) Dissolve the metal salt, precipitate it with an alkali solution, filter it, and calcine it to obtain an oxide support; (2) React the Ru precursor solution at high temperature to obtain Ru metalene; (3) Load the Ru metalene obtained in step (2) on the support of step (1), and then obtain the Ru metalene catalyst after impregnating with an auxiliary agent and reduction treatment.

[0006] According to the embodiment of the present invention, in step (1), the metal salt is selected from at least one of soluble magnesium salts, cerium salts, and praseodymium salts, and preferably magnesium salts.

[0007] According to the embodiment of the present invention, in step (1), the magnesium salt is selected from at least one of magnesium nitrate, magnesium chloride, and magnesium carbonate.

[0008] According to the embodiment of the present invention, in step (1), the magnesium precipitate is prepared by adding an alkali solution to a solution containing a magnesium salt. Preferably, before calcination, the magnesium precipitate can also be dried. Further, the conditions of the drying treatment include: the drying temperature is 60-120 °C, preferably 80 °C; the drying time is 8-24 hours, preferably 12 hours.

[0009] According to the embodiment of the present invention, the precipitating agent is one or more of potassium hydroxide, sodium hydroxide, and ammonia water, and preferably sodium hydroxide.

[0010] According to the embodiment of the present invention, the solution containing the magnesium salt further includes a solvent, and the solvent is selected from at least one of ethanol, water, and tetrahydrofuran, and preferably water.

[0011] According to an embodiment of the present invention, in step (1), the calcination treatment conditions are calcination in an oxygen-containing atmosphere. Further, the oxygen-containing atmosphere can be selected from the atmospheres known in the art, such as air. Further, the calcination conditions are: the calcination temperature is 400 - 600 °C, preferably 500 °C; the calcination time is 2 - 10 hours, preferably 6 hours.

[0012] According to an embodiment of the present invention, in step (2), the ruthenium precursor is one of ruthenium anhydrous chloride, ruthenium nitrate, ruthenium acetylacetonate, and dodecacarbonyltriruthenium.

[0013] According to an embodiment of the present invention, in step (2), the high-temperature treatment process is to perform a hydrothermal reaction on the ruthenium precursor solution. The hydrothermal reaction temperature is: 160 - 200 °C; the reaction time is 4 - 8 hours.

[0014] According to an embodiment of the present invention, in step (3), the loading method is an oil bath. The reaction conditions are: the temperature is 80 - 120 °C, preferably 80 °C; the reaction time is 6 - 10 hours, preferably 8 hours.

[0015] According to an embodiment of the present invention, in step (3), the impregnation method is stirring impregnation, and the impregnation solution is one or more of potassium nitrate, barium nitrate, and cesium nitrate, preferably potassium nitrate. The impregnation reaction conditions are: the temperature is 10 - 30 °C, preferably 25 °C; the reaction time is 12 - 24 hours, preferably 12 hours.

[0016] According to an embodiment of the present invention, in step (3), the reducing atmosphere includes a mixture of hydrogen and argon, wherein the volume content of hydrogen is 1 - 10 vol%. Preferably, the volume content of hydrogen is 10 vol%.

[0017] According to an embodiment of the present invention, the reduction treatment conditions include: the reduction temperature is 400 - 600 °C, and the reduction time is 2 - 10 hours.

[0018] According to an embodiment of the present invention, during the reduction treatment, the heating rate is 2 - 10 °C min -1 , preferably 2 °Cmin -1 .

[0019] According to a preferred embodiment of the present invention, the method for preparing the layer-thickness controllable Ru metalene catalyst comprises the following steps: (A1) Disperse a metal salt and a precipitating agent uniformly in a solvent respectively, mix them, and allow to stand for aging to obtain a metal precipitate; (A2) The metal precipitate obtained in step (A1) is subjected to a calcination treatment to obtain a metal oxide support; (A3) React the ruthenium precursor solution at a high temperature to obtain ruthenium metallene, and the reaction temperature is 160 °C; (A4) Load the ruthenium metallene obtained in step (A3) onto the metal oxide support of (A2), and then load the promoter onto the ruthenium metallene catalyst by an impregnation method to obtain the Ru-based catalyst.

[0020] Preferably, the standing and aging time is 6-24 hours, preferably 12 hours.

[0021] Preferably, the preparation method further includes: (A4) pre-reducing the Ru-based catalyst.

[0022] According to a preferred embodiment of the present invention, the preparation method of the Ru-based catalyst includes the following steps: (B1) Disperse the metal salt and the precipitant evenly in a solvent respectively, mix them, and stand and age to obtain a metal precipitate; (B2) Calcinate the metal precipitate obtained in step (B1) to obtain a metal oxide support; (B3) React the ruthenium precursor solution at a high temperature to obtain ruthenium metallene, and the reaction temperature is 180 °C; (B4) Load the ruthenium metallene obtained in step (B3) onto the metal oxide support of (B2), and then load the promoter onto the ruthenium metallene catalyst by an impregnation method to obtain the Ru-based catalyst.

[0023] Preferably, the standing and aging time is 6-24 hours, preferably 12 hours.

[0024] Preferably, the preparation method further includes: (B4) pre-reducing the Ru-based catalyst.

[0025] According to an exemplary embodiment of the present invention, the preparation method of the Ru-based catalyst specifically includes: (C1) Disperse the metal salt and the precipitant evenly in a solvent respectively, mix them, and stand and age to obtain a metal precipitate; (C2) Calcinate the metal precipitate obtained in step (C1) to obtain a metal oxide support; (C3) React the ruthenium precursor solution at a high temperature to obtain ruthenium metallene, and the reaction temperature is 200 °C; (C4) Load the ruthenium metallene obtained in step (C3) onto the metal oxide support of (C2), and then load the promoter onto the ruthenium metallene catalyst by an impregnation method to obtain the Ru-based catalyst.

[0026] Preferably, the standing and aging time is 6-24 hours, preferably 12 hours.

[0027] Preferably, the preparation method further includes: (C4) pre-reducing the Ru-based catalyst.

[0028] The present invention also provides the application of the above Ru-based catalyst, preferably in the synthesis of ammonia, more preferably for distributed ammonia synthesis.

[0029] Beneficial effects 1. The present invention provides a Ru metalene catalyst with controllable layer thickness and a method for coupling renewable energy electricity for distributed ammonia synthesis. The Ru metalene catalyst has excellent catalytic reaction performance in the ammonia synthesis process, providing a new method for green ammonia synthesis.

[0030] 2. In the synthesis method of the Ru metalene catalyst with controllable layer thickness provided by the present invention, by adjusting the conditions in the high-temperature treatment (such as reaction temperature, reaction time, etc.), the layer thickness of the Ru metalene can be effectively regulated.

[0031] 3. The Ru metalene catalyst with controllable layer thickness prepared by the present invention can be used for catalytic ammonia synthesis at a lower pressure (0.1 - 1 MPa) and a lower temperature (300 - 400 °C), having good ammonia synthesis catalytic performance and better stability.

[0032] 4. The Ru metalene catalyst with controllable layer thickness of the present invention provides new ideas for mild ammonia synthesis, and has a simple preparation process, convenient operation, high yield, good activity under low-pressure conditions, and obvious prospects for industrial application. Description of the drawings

[0033] Figure 1 TEM and AFM images of the Ru metalene catalyst with controllable layer thickness prepared in Example 1.

[0034] Figure 2 TEM and AFM images of the Ru metalene catalyst with controllable layer thickness prepared in Example 2.

[0035] Figure 3 TEM and AFM images of the Ru metalene catalyst with controllable layer thickness prepared in Example 3.

[0036] Figure 4 Ammonia synthesis reaction rates of the Ru metalene catalysts with controllable layer thickness prepared in Examples 1 - 3 and the Ru-based catalyst prepared in Comparative Example 1 at 400 °C and 1 MPa.

[0037] Figure 5 For the Ru metalene catalyst with controllable layer thickness prepared in Example 1 under the conditions of 400 °C and 1 MPa, different N 2 / H 2Effect of volume ratio on ammonia synthesis reaction rate.

[0038] Figure 6 Stability of the Ru metallene catalyst with controllable layer thickness prepared in Example 1 under the conditions of 400 °C and 1 MPa. Detailed implementation manners

[0039] A preparation method of a Ru metallene catalyst, comprising the following steps: (1) Dissolve the metal salt and then perform precipitation treatment, and obtain an oxide after calcination; (2) Perform a high-temperature reaction through a Ru precursor solution to obtain Ru metallene; (3) Load the Ru metallene obtained in step (2) on the oxide support obtained in step (1), and obtain the Ru metallene catalyst through impregnation with an auxiliary agent and reduction treatment.

[0040] Preferably, in step (1), the metal salt is selected from at least one of soluble magnesium salts, cerium salts, and praseodymium salts; the precipitating agent used in the precipitation treatment is sodium hydroxide.

[0041] Preferably, in step (1), the calcination temperature is 400 - 600 °C, and the calcination time is 2 - 10 hours.

[0042] Preferably, in step (2), the ruthenium precursor is one of ruthenium anhydrous chloride, ruthenium nitrate, ruthenium acetylacetonate, and dodecacarbonyltriruthenium.

[0043] Preferably, in step (2), the high-temperature reaction temperature is 160 °C - 200 °C, and the reaction time is 4 - 8 hours.

[0044] Preferably, in step (3), the reaction temperature for loading the Ru metallene on the oxide support is 80 - 120 °C, and the reaction time is 6 - 10 hours.

[0045] Preferably, in step (3), the impregnation method is stirring impregnation, and the impregnation solution is one or more of potassium nitrate, barium nitrate, and cesium nitrate; the impregnation temperature is 10 - 30 °C, and the impregnation time is 12 - 24 hours.

[0046] Preferably, in step (3), the reduction treatment refers to heat treatment in a reducing atmosphere. Among them, the reducing atmosphere is a mixture of hydrogen and argon, and the volume content of hydrogen is 1 - 10 vol%; the temperature of the heat treatment is 300 - 500 °C, and the time of the heat treatment is 1 - 4 hours.

[0047] A Ru metallene catalyst with controllable layer thickness. Preferably, after the Ru precursor in step (2) is treated at different temperatures, metallene with different layer thicknesses will be formed, and the treatment temperature is 160 - 200 °C.

[0048] Application of the described Ru metalene catalyst in ammonia synthesis: The conditions for ammonia synthesis are as follows: the pressure is 0.1 - 5 MPa, the temperature is 300 - 400 °C, and the volume ratio of H 2 and N 2 is 1:3 - 3:1.

[0049] The technical solution of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only illustrative explanations of the present invention and should not be construed as limiting the protection scope of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0050] Unless otherwise specified, the raw materials and reagents used in the following embodiments are commercially available products or can be prepared by known methods.

[0051] Example 1 Step A: Dissolve MgCl 2 ·6H 2 O (2 g) and benzoic acid (0.12 g) in 60 mL of deionized water at room temperature. Stir the mixture for 10 minutes. Then, gradually add 2M NaOH (20 mL) dropwise to the solution to form a white precipitate. Subsequently, transfer the slurry to a 100 mL high-pressure hydrothermal autoclave, gradually heat it to 180 °C, and maintain it at this temperature for 24 hours. After filtration, obtain the Mg(OH) 2 precursor, then wash it with water and vacuum dry it overnight at 80 °C. Finally, calcine it in air at 500 °C for 6 hours to obtain the MgO support.

[0052] Step B: Dissolve 0.06 mmol of RuCl 3 and 100 mg of polyvinylpyrrolidone PVP in 10 mL of deionized water. Then, add 0.4 mL of 40 wt.% formaldehyde solution, and adjust the total volume of the solution to 15 mL with deionized water. Transfer the solution to a 25 mL hydrothermal autoclave and seal it. Heat the autoclave at 160 °C for 8 hours, then cool it to room temperature to form a Ru metalene suspension.

[0053] Step C: Weigh 300 mg of the MgO obtained in Step A into a single-neck flask. Then, take 25 mL of the ruthenium metalene suspension obtained in Step B (prepared twice) into the single-neck flask, and heat it at a constant temperature of 80 °C for 8 hours. After the reaction, obtain Ru / MgO by suction filtration and drying. Then, dissolve 38.8 mg of potassium nitrate in 1.5 mL of deionized water, and then gradually add the potassium nitrate solution dropwise to Ru / MgO. After the addition, continue to stir for 12 hours. The obtained sample is in 10% by volume H 2Under an Ar atmosphere, heat it up to 400 °C at a rate of 2 °C / min -1 and reduce for 2 hours. Finally, the ruthenium metalene catalyst, namely K-Ru-160 (160 refers to the heat treatment temperature of the Ru precursor), is obtained.

[0054] Example 2 Step A: Dissolve MgCl 2 ·6H 2 O (2 g) and benzoic acid (0.12 g) in 60 mL of deionized water at room temperature. Stir the mixture for 10 minutes. Then, gradually add 2M NaOH (20 mL) dropwise to the solution to form a white precipitate. Subsequently, transfer the slurry to a 100 mL high-pressure hydrothermal autoclave, gradually heat it to 180 °C, and maintain it at this temperature for 24 hours. After filtration, the Mg(OH) 2 precursor is obtained, then washed with water and vacuum dried at 80 °C overnight. Finally, calcine it in air at 500 °C for 6 hours to obtain the MgO support.

[0055] Step B: Dissolve 0.06 mmol of RuCl 3 and 100 mg of polyvinylpyrrolidone PVP in 10 mL of deionized water. Then, add 0.4 mL of 40 wt.% formaldehyde solution, and adjust the total volume of the solution to 15 mL with deionized water. Transfer the solution to a 25 mL hydrothermal autoclave and seal it. Heat the autoclave at 180 °C for 8 hours, then cool it to room temperature to form a ruthenium metalene suspension.

[0056] Step C: Weigh 300 mg of the MgO obtained in Step A into a single-neck flask. Then, take 25 mL of the ruthenium metalene suspension obtained in Step B (prepared twice) into the single-neck flask, heat it at a constant temperature of 80 °C for 8 hours. After the reaction, filter it and dry it to obtain Ru / MgO. Then dissolve 38.8 mg of potassium nitrate in 1.5 mL of deionized water, and then gradually add the potassium nitrate solution dropwise to Ru / MgO. After the addition is completed, continue to stir for 12 hours. The obtained sample is heated up to 400 °C at a rate of 2 °C / min 2 under a volume concentration of 10% H -1 / Ar atmosphere and reduced for 2 hours. Finally, the ruthenium metalene catalyst, namely K-Ru-180, is obtained.

[0057] Example 3 Step A: Dissolve MgCl 2 ·6H 2O (2 g) and benzoic acid (0.12 g) were dissolved in 60 mL of deionized water at room temperature. The mixture was stirred for 10 minutes. Then 2M NaOH (20 mL) was added dropwise to the solution to form a white precipitate. Subsequently, the slurry was transferred to a 100 mL high-pressure hydrothermal autoclave, gradually heated to 180 °C, and maintained at this temperature for 24 hours. After filtration, the Mg(OH) 2 precursor was obtained, then washed with water and dried under vacuum at 80 °C overnight. Finally, the MgO support was obtained by calcination in air at 500 °C for 6 hours.

[0058] Step B: 0.06 mmol of RuCl 3 and 100 mg of polyvinylpyrrolidone PVP were dissolved in 10 mL of deionized water. Then, 0.4 mL of 40 wt.% formaldehyde solution was added, and the total volume of the solution was adjusted to 15 mL with deionized water. The solution was transferred to a 25 mL hydrothermal autoclave and sealed. The autoclave was heated at 200 °C for 8 hours, then cooled to room temperature to form a Ru metalene suspension.

[0059] Step C: Weigh 300 mg of the MgO obtained in Step A into a single-necked flask. Then, take 25 mL of the ruthenium metalene suspension obtained in Step B (prepared twice) into the single-necked flask, and heat it at a constant temperature of 80 °C for 8 hours. After the reaction, Ru / MgO was obtained by suction filtration and drying. Then, 38.8 mg of potassium nitrate was dissolved in 1.5 mL of deionized water, and the potassium nitrate solution was added dropwise to Ru / MgO. After the addition, stirring was continued for 12 hours. The obtained sample was heated from room temperature to 400 °C at a rate of 2 °C min 2 in a 10% H -1 / Ar atmosphere and reduced for 2 hours. Finally, the ruthenium metalene catalyst, namely K-Ru-200, was obtained.

[0060] Comparative Example 1 Step A: MgCl 2 ·6H 2 O (2 g) and benzoic acid (0.12 g) were dissolved in 60 mL of deionized water at room temperature. The mixture was stirred for 10 minutes. Then 2M NaOH (20 mL) was added dropwise to the solution to form a white precipitate. Subsequently, the slurry was transferred to a 100 mL high-pressure hydrothermal autoclave, gradually heated to 180 °C, and maintained at this temperature for 24 hours. After filtration, the Mg(OH) 2 precursor was obtained, then washed with water and dried under vacuum at 80 °C overnight. The MgO support was obtained after calcination in air at 500 °C for 6 hours.

[0061] Step B: Dissolve 33.8 mg of potassium nitrate and 24.62 mg of anhydrous ruthenium trichloride in 1.5 mL of ethanol. Immerse the mixed solution on 300 mg of MgO support, and then dry the obtained sample overnight at 60 °C. Heat it up to 400 °C in an atmosphere of 10% H 2 / Ar for 2 hours to obtain Ru nanoparticle catalyst, namely K-Ru NP.

[0062] Test Example 1 Take the Ru metalenes prepared in Examples 1-3 and characterize their morphology and layer thickness by field emission transmission electron microscopy (TEM) and atomic force microscopy (AFM). The results are as Figure 1-3 shown. It can be seen from Figure 1-3 that the Ru metalene prepared in Example 1 presents a more regular triangular morphology structure compared with those prepared in Examples 2 and 3. The AFM results show that the layer thickness of the metalene of K-Ru-160 is 0.92 nm, which is thinner than that of K-Ru-180 (2.2 nm) and K-Ru-200 (3.0 nm). The results show that changing the hydrothermal temperature can affect the layer thickness of Ru metalene, thus realizing the controllable preparation of Ru metalenes with different layer thicknesses.

[0063] Application Example 1 The distributed ammonia synthesis performance test method is as follows: Respectively take 0.20 g of the catalysts prepared in Examples 1-3 and Comparative Example 1 for ammonia synthesis performance test. Measure the ammonia synthesis rate on a continuous flow micro fixed-bed reactor. Pass in a mixed gas of 25% N 2 -75% H 2 with a total mass space velocity of 60,000 mL g -1 h -1 . Measure the concentration change of NH 3 in the tail gas by ion chromatography (Thermo Scientific, DIONEX, ICS-600); under the conditions of 400 °C and 1 MPa, measure the ammonia synthesis reaction rate of the catalyst. Among them, the test results of Examples 1-3 and Comparative Example 1 are shown in Figure 4 .

[0064] It can be seen from Figure 4 that the Ru-based catalysts of Examples 1-3 and Comparative Example 1 show different ammonia synthesis activities. Under the conditions of 400 °C and 1 MPa, their activity order is K-Ru-160>K-Ru-180>K-Ru-200>K-Ru NP. It can be seen that the activities of Ru metalene catalysts are significantly better than those of the Ru nanoparticle catalyst in Comparative Example 1 for ammonia synthesis activity (6.0 mmol g -1h -1 )。Among them, the reaction rate of ammonia synthesis by the K-Ru-160 catalyst can reach 20.3 mmol g -1 h -1 。

[0065] Application Example 2 The performance test method for distributed ammonia synthesis is as follows: Take 0.20 g of the K-Ru-160 catalyst prepared in Example 1 for the ammonia synthesis performance test. The ammonia synthesis rate is measured on a continuous flow micro fixed bed reactor. The reaction gas is introduced, and its total mass space velocity is 60,000 mL g -1 h -1 , and the concentration change of NH 3 in the tail gas is measured by ion chromatography (Thermo Scientific, DIONEX, ICS-600); among them, the composition of the reaction gas is respectively: 75% H 2 -25 vl% N 2 , 60% H 2 -40% N 2 , 50% H 2 -50% N 2 , 40% H 2 -60% N 2 , 25% H 2 -75% N 2 。Under the conditions of 400 °C and 1 MPa, the ammonia synthesis reaction rate of the prepared K-Ru-160 catalyst is measured, and the test results are shown in Figure 5 。

[0066] From Figure 5 it can be seen that the K-Ru-160 catalyst in Example 1 shows different ammonia synthesis activities. The ammonia synthesis activity in the 40% H 2 -60% N 2 mixed gas is better than other atmospheres. Under 400 °C and 1 MPa, the reaction rate of ammonia synthesis by the K-Ru-160 catalyst can reach 46.2 mmol g -1 h -1 。

[0067] Application Example 3 The performance test method for distributed ammonia synthesis is as follows: Take 0.20 g of the K-Ru-160 catalyst prepared in Example 1 for the ammonia synthesis performance test. The ammonia synthesis rate is measured on a continuous flow micro fixed bed reactor. Introduce 40% H 2 -60% N 2 mixed gas, and its total mass space velocity is 60,000 mL g -1 h-1 The concentration change of NH in the tail gas was measured by ion chromatography (Thermo Scientific, DIONEX, ICS-600); under the conditions of 400 °C and 1 MPa, the ammonia synthesis reaction rate of the catalyst was measured for 500 hours, and the test results are shown in 3 . Figure 6 .

[0068] From Figure 6 it can be seen that the ammonia synthesis reaction rate of the K-Ru-160 catalyst basically remained stable without an obvious decreasing trend. This result shows that the K-Ru-160 catalyst not only has high reaction activity but also has excellent catalytic stability.

[0069] The above describes the exemplary embodiments of the present invention. However, the protection scope of this application is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made by those skilled in the art within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a Ru metalloene catalyst, characterized in that: The following steps are involved: (1) Dissolving the metal salt, subjecting it to precipitation treatment, and calcining it to obtain the oxide; (2) obtaining Ru metalloene by high temperature reaction of Ru precursor solution; (3) The Ru metal olefin obtained in step (2) is loaded on the oxide support in step (1), and then impregnated with an auxiliary agent and subjected to reduction treatment to obtain the Ru metal olefin catalyst.

2. The preparation method according to claim 1, characterized in that: In step (1), the metal salt is selected from at least one of a soluble magnesium salt, a cerium salt and a praseodymium salt; and the precipitant used in the precipitation treatment process is sodium hydroxide.

3. The preparation method according to claim 1, characterized in that: In step (1), the calcination temperature is 400-600°C and the calcination time is 2-10 hours.

4. The preparation method according to claim 1, characterized in that: In step (2), the ruthenium precursor is one of anhydrous ruthenium chloride, ruthenium nitrate, ruthenium acetylacetonate and triruthenium dodecacarbonyl.

5. The preparation method according to claim 1, characterized in that: In step (2), the high temperature reaction temperature is 160°C-200°C, and the reaction time is 4-8 hours.

6. The preparation method according to claim 1, characterized in that: In step (3), the reaction temperature for loading Ru metal olefin on the oxide support is 80-120° C., and the reaction time is 6-10 hours.

7. The preparation method according to claim 1, characterized in that: In step (3), the impregnation method is stirring impregnation, the impregnation solution is one or more of potassium nitrate, barium nitrate and cesium nitrate; the impregnation temperature is 10-30°C, and the impregnation time is 12-24 hours.

8. The preparation method according to claim 1, characterized in that: In step (3), the reduction treatment refers to heat treatment in a reducing atmosphere, wherein the reducing atmosphere is a mixture of hydrogen and argon, the volume content of hydrogen is 1-10 vol%; the heat treatment temperature is 300-500 ° C, and the heat treatment time is 1-4 hours.

9. A Ru metalloene catalyst with controllable layer thickness obtained by the preparation method according to any one of claims 1 to 8, characterized in that: In step (2), the Ru precursor is treated at different temperatures to form metalloene with different layer thicknesses, and the treatment temperature is 160-200 °C.

10. Use of the Ru metalloene catalyst in ammonia synthesis according to claim 9, characterized in that: The conditions for ammonia synthesis are: pressure of 0.1-5 MPa, temperature of 300-400 °C, and volume ratio of H2 to N2 of 1:3-3:1.

Images