Synthetic ammonia catalyst and preparation method thereof

Abstract

The invention discloses a synthetic ammonia catalyst and a preparation method thereof, and belongs to the technical field of catalyst material preparation. The composite material comprises the following components in parts by mass: 20-60 parts of Fe nanoclusters, 1-5 parts of LiH and 40-70 parts of amine salt of lanthanide compounds. The catalyst and the preparation method can efficiently catalyze synthesis of ammonia at normal pressure and low temperature, and the synthesis ammonia catalyst with high thermal stability and low cost and the preparation method thereof are used for solving the problems of harsh reaction conditions (requiring high temperature and high pressure), high energy consumption, high cost, poor catalytic performance and the like of the existing synthesis ammonia catalyst.

Description

Technical Field

[0001] This invention belongs to the field of catalyst material preparation technology, specifically relating to an ammonia synthesis catalyst and its preparation method. Background Technology

[0002] The ammonia synthesis industry is a core pillar of modern chemical industry, and the performance of ammonia synthesis catalysts is a crucial factor affecting the economic benefits of the ammonia synthesis industry. Traditional ammonia synthesis processes use iron-based catalysts, primarily molten iron catalysts, with alumina (Al₂O₃), calcium oxide (CaO), and potassium oxide (K₂O) serving as structural and electronic aids. The catalytic mechanism relies on active sites on the iron surface promoting the dissociation and adsorption of nitrogen molecules (N₂). The aids extend catalyst life by stabilizing the iron lattice structure, adjusting surface electron density, or inhibiting sintering. For example, Chinese invention patents with publication numbers CN1091997A and CN1293593A, while exhibiting advantages such as low cost and good stability, also suffer from high operating pressures (10–30 MPa) and operating temperatures (450–550 °C), low catalytic activity, and high energy consumption. Cobalt catalysts use cobalt (Co) as the active ingredient and alkaline earth metals and alkali metals as promoters (e.g., Chinese invention patents with publication numbers CN105597760A and CN1293593A, respectively), and are typically supported on alumina or silica. Their catalytic mechanism relies on the d-electron structure of cobalt to promote the adsorption and dissociation of N₂, while the promoters optimize activity by adjusting the oxidation state of cobalt or its surface acidity. Although they can supplement iron catalysts under high ammonia concentration conditions, their catalytic activity is lower than that of iron. Ruthenium catalysts, using the noble metal ruthenium (Ru) as the active component, activated carbon (AC), graphene, or metal oxides as supports, and metal salts such as barium (Ba), silver (Ag), and cesium (Cs) as promoters, can significantly reduce the temperature and pressure of the ammonia synthesis reaction (e.g., Chinese invention patents with publication numbers CN102950026A, CN101579627A, and CN1401426A). Their catalytic mechanism is based on ruthenium's strong electron-donating ability, which significantly lowers the N2 dissociation energy barrier. Simultaneously, the promoters stabilize the oxidation state of ruthenium (e.g., Ru). 0 The activity can be further optimized by adjusting the electronic structure of the support. Therefore, it has significant energy-saving and consumption-reducing effects; however, the high price of ruthenium hinders the industrial application of the catalyst.

[0003] In summary, existing ammonia synthesis catalysts suffer from problems such as harsh reaction conditions, high energy consumption, high cost, and unsatisfactory catalytic performance. There is a need to provide a low-cost, highly active, and low-energy-consumption ammonia synthesis catalyst. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide a synthetic ammonia catalyst and its preparation method. This catalyst and preparation method can efficiently catalyze the synthesis of ammonia at normal pressure and low temperature, and have high thermal stability and low cost. This synthetic ammonia catalyst and its preparation method are used to solve the problems of harsh reaction conditions (requiring high temperature and high pressure), high energy consumption, high cost and poor catalytic performance of existing synthetic ammonia catalysts.

[0005] To achieve the above objectives, the present invention employs the following technical solution: One aspect of this invention provides an ammonia synthesis catalyst, comprising, by mass parts, 20-60 parts of Fe nanoclusters, 1-5 parts of LiH, and 40-70 parts of amine salts of lanthanides.

[0006] The catalytic conditions for using the above-mentioned ammonia synthesis catalyst are a temperature of 200-300℃ and a pressure of 0.1-2 MPa.

[0007] In another aspect, the present invention provides a method for preparing an ammonia synthesis catalyst, comprising the following steps: Iron source, lithium source, lanthanum source and nitrogen-containing compound are used as raw materials, and ball milling activation treatment is carried out under a protective atmosphere to obtain the precursor; Under a mixed gas of H2 and N2, the precursor undergoes a high-temperature and high-pressure reaction to produce an ammonia synthesis catalyst.

[0008] In one embodiment, the iron source is FeCl3•6H2O, the lithium source is LiOH•H2O, the lanthanum source is any one of LaCl3•6H2O, LaCl3•7H2O, CeCl3•6H2O, and CeCl3•7H2O, and the nitrogen-containing compound is urea.

[0009] In one embodiment, the molar ratio of iron, lithium, lanthanum and nitrogen in the raw material is (2-4):(2-4):(1-2):(3-10).

[0010] In one embodiment, the protective atmosphere is an argon atmosphere.

[0011] In one embodiment, the ball-to-material ratio of the ball milling activation treatment is 10-20:1, the ball milling activation treatment time is 10-30 hours, and the ball milling activation treatment speed is 300-500 rpm.

[0012] In one embodiment, the ball-to-material ratio for the ball milling activation treatment is 15-20:1, and the ball milling activation treatment time is 10-15 hours.

[0013] In one embodiment, the molar ratio of H2 to N2 is 3:1.

[0014] In one embodiment, the high-temperature and high-pressure reaction is carried out in a high-pressure reactor, wherein the reaction pressure is 5-10 MPa, the reaction temperature is 300-500°C, and the reaction time is 5-10 hours.

[0015] In one embodiment, the high-temperature and high-pressure reaction has a reaction pressure of 4-8 MPa, a reaction temperature of 400-500°C, and a reaction time of 5-8 hours.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a catalyst for ammonia synthesis. The surface adsorption energy and transition state energy of this catalyst are lower than those of traditional ammonia synthesis catalysts, exhibiting excellent catalytic performance for ammonia synthesis at ambient pressure and low temperature. Specifically, this ammonia synthesis catalyst can efficiently catalyze ammonia synthesis with high thermal stability, mainly due to the following reasons: The synergistic effect of multiple components reduces the reaction activation energy. Fe nanoclusters, as the main active component, significantly increase the number of active sites due to their high specific surface area and nanoscale size effect, while shortening the reactant diffusion path and increasing the reaction rate. LiH, as an electronic promoter, enhances the surface electron density of Fe nanoclusters by providing electrons, thereby promoting the chemisorption and activation of nitrogen molecules (N2). The dissociation of N2 on the catalyst surface is the rate-determining step in ammonia synthesis, and the addition of the electronic promoter significantly reduces the activation energy of this step. Lanthanide amine salts play a structural stabilizing role. Lanthanide elements (such as La and Ce) amine salts, as structural promoters, inhibit the sintering and grain growth of Fe nanoclusters at high temperatures by forming solid solutions with Fe or surface modification, maintaining the high specific surface area and active site stability of the catalyst. Furthermore, the strong basicity of lanthanides may promote nitrogen adsorption and activation, further lowering the reaction energy barrier. This catalyst, through the electronic aid effect of LiH and surface modification with lanthanides, achieves efficient N2 dissociation at low temperatures. Urea, as a nitrogen-containing compound, decomposes to produce NH3 or NH4+ in high-temperature, high-pressure reactions. x The intermediate releases hydrogen gas (H2). The synergistic effect of LiH and Fe nanoclusters promotes the dissociation of H2, generating active hydrogen atoms. These hydrogen atoms rapidly combine with activated nitrogen species to form NH3, thus bypassing the energy barrier of H2 dissociation under traditional high temperature and high pressure. This results in a low-temperature, high-efficiency catalytic mechanism. Furthermore, lanthanide amine salts inhibit the migration and aggregation of Fe nanoclusters through steric hindrance. Fe nanoclusters may undergo redox cycles (such as Fe...) during the reaction. 0 / Fe 2+ / Fe 3+ LiH and lanthanide amine salts can inhibit the deep oxidation or reduction of Fe by providing electrons or stabilizing the oxidation state, thereby maintaining the active structure of the catalyst and giving the ammonia synthesis catalyst high thermal stability.

[0017] The ammonia synthesis catalyst provided by this invention can catalyze the ammonia synthesis reaction at 200-300℃ and 0.1-2MPa, exhibiting excellent catalytic performance. It reduces energy consumption, saves costs, and improves catalytic efficiency during the ammonia synthesis process, thus possessing broad application and promotion value. The catalyst provided by this invention is free of precious metal elements, has low cost, a simple preparation method, and is pollution-free throughout the entire process, demonstrating broad prospects and significant application value in the ammonia synthesis industry.

[0018] Furthermore, through mechanochemical processes, ball milling can refine the particle size of raw materials, increase the reaction interface area, and introduce defects and strain energy. Detailed Implementation

[0019] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0020] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0021] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0022] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0023] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0024] This invention provides a catalyst for ammonia synthesis and a method for preparing the same.

[0025] The present invention provides an ammonia synthesis catalyst, which is composed of Fe nanoclusters, LiH, and amine salts of lanthanides, comprising, by mass parts, 20-60 parts of Fe nanoclusters, 1-5 parts of LiH, and 40-70 parts of amine salts of lanthanides.

[0026] The catalytic conditions for using the above-mentioned ammonia synthesis catalyst are a temperature of 200-300℃ and a pressure of 0.1-2 MPa.

[0027] In another aspect, the present invention provides a method for preparing the above-mentioned ammonia synthesis catalyst, comprising the following steps: Using iron, lithium, lanthanum and nitrogen-containing compounds as raw materials, the materials are placed in a ball mill and activated under argon protection to obtain the precursor. The obtained precursor is then transferred to a high-pressure reactor and subjected to a high-temperature and high-pressure reaction with H2 and N2 to obtain an ammonia synthesis catalyst.

[0028] In one specific embodiment, the preparation method of the above-mentioned ammonia synthesis catalyst specifically includes the following steps: Iron, lithium, lanthanum, and nitrogen-containing compounds were selected as raw materials. The proportioned raw materials were placed in a high-energy ball mill and ball milled under argon protection to obtain a precursor. The precursor was transferred to a high-pressure reactor and a mixed gas with a molar ratio of H2 to N2 of 3:1 was introduced to carry out a high-temperature and high-pressure reaction to obtain an ammonia synthesis catalyst.

[0029] Preferably, the iron source is FeCl3•6H2O, the lithium source is LiOH•H2O, the lanthanum source is any one of LaCl3•6H2O, LaCl3•7H2O, CeCl3•6H2O, and CeCl3•7H2O, and the nitrogen-containing compound is urea.

[0030] Preferably, the raw materials are mixed in a molar ratio of iron, lithium, lanthanum and nitrogen of (2-4):(2-4):(1-2):(3-10).

[0031] Preferably, the ball-to-material ratio for the ball milling activation treatment is 10-20:1, the ball milling activation treatment time is 10-30 hours, and the ball milling activation treatment speed is 300-500 rpm.

[0032] More preferably, the ball-to-material ratio for the ball milling activation treatment is 15-20:1, and the ball milling activation treatment time is 10-15 hours.

[0033] Preferably, the high-temperature and high-pressure reaction is carried out in a high-pressure reactor, with a reaction pressure of 5-10 MPa, a reaction temperature of 300-500°C, and a reaction time of 5-10 hours.

[0034] More preferably, the high-temperature and high-pressure reaction has a reaction pressure of 4-8 MPa, a reaction temperature of 400-500°C, and a reaction time of 5-8 hours.

[0035] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0036] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0037] Example 1 This embodiment provides a method for preparing an ammonia synthesis catalyst, including the following steps: (1) Weigh out 55.29g FeCl3•6H2O, 8.58g LiOH•H2O, 36.13g LaCl3•6H2O and 30.63g urea.

[0038] (2) Add the above raw materials into the ball mill jar of the high-energy ball mill, and fill the ball mill jar with argon gas to remove air and ensure an inert environment. Set the ball-to-material ratio to 15:1, the ball milling time to 15 hours, and the ball milling speed to 400 rpm, and perform ball milling to obtain the precursor.

[0039] (3) The precursor was transferred to a high-pressure reactor, and a mixed gas with a H2:N2 molar ratio of 3:1 was introduced. The reaction pressure was controlled at 7 MPa, the reaction temperature at 400 °C, and the reaction time at 7 hours. After the reaction was completed, the mixture was cooled to room temperature and the ammonia synthesis catalyst was obtained.

[0040] Example 2 This embodiment provides a method for preparing an ammonia synthesis catalyst, including the following steps: (1) Weigh 67.48g FeCl3•6H2O, 10.48g LiOH•H2O, 22.05g LaCl3•6H2O and 18.71g urea.

[0041] (2) Add the above raw materials into the ball mill jar of the high-energy ball mill, and fill the ball mill jar with argon gas to remove air and ensure an inert environment. Set the ball-to-material ratio to 20:1, the ball milling time to 15 hours, and the ball milling speed to 500 rpm, and perform ball milling to obtain the precursor.

[0042] (3) The precursor was transferred to a high-pressure reactor, and a mixed gas with a H2:N2 molar ratio of 3:1 was introduced. The reaction pressure was controlled at 7 MPa, the reaction temperature at 500 °C, and the reaction time at 5 hours. After the reaction was completed, the mixture was cooled to room temperature and the ammonia synthesis catalyst was obtained.

[0043] Example 3 This embodiment provides a method for preparing an ammonia synthesis catalyst, including the following steps: (1) Weigh 54.23g FeCl3•6H2O, 12.26g LiOH•H2O, 37.34g CeCl3•7H2O and 30.08g urea.

[0044] (2) Add the above raw materials into the ball mill jar of the high-energy ball mill, and fill the ball mill jar with argon gas to remove air and ensure an inert environment. Set the ball-to-material ratio to 15:1, the ball milling time to 15 hours, and the ball milling speed to 500 rpm, and perform ball milling to obtain the precursor.

[0045] (3) The precursor was transferred to a high-pressure reactor, and a mixed gas with a H2:N2 molar ratio of 3:1 was introduced. The reaction pressure was controlled at 7 MPa, the reaction temperature at 400 °C, and the reaction time at 7 hours. After the reaction was completed, the mixture was cooled to room temperature and the ammonia synthesis catalyst was obtained.

[0046] Example 4 This embodiment provides a method for preparing an ammonia synthesis catalyst, including the following steps: (1) Weigh out 55.29g FeCl3•6H2O, 8.58g LiOH•H2O, 36.13g LaCl3•6H2O and 30.63g urea.

[0047] (2) Add the above raw materials into the ball mill jar of the high-energy ball mill, and fill the ball mill jar with argon gas to remove air and ensure an inert environment. Set the ball-to-material ratio to 10:1, the ball milling time to 10 hours, and the ball milling speed to 300 rpm, and perform ball milling to obtain the precursor.

[0048] (3) The precursor was transferred to a high-pressure reactor, and a mixed gas with a H2:N2 molar ratio of 3:1 was introduced. The reaction pressure was controlled at 5 MPa, the reaction temperature at 300 °C, and the reaction time at 5 hours. After the reaction was completed, the mixture was cooled to room temperature and the ammonia synthesis catalyst was obtained.

[0049] Example 5 This embodiment provides a method for preparing an ammonia synthesis catalyst, including the following steps: (1) Weigh 67.48g FeCl3•6H2O, 10.48g LiOH•H2O, 22.05g LaCl3•6H2O and 18.71g urea.

[0050] (2) Add the above raw materials into the ball mill jar of the high-energy ball mill, and fill the ball mill jar with argon gas to remove air and ensure an inert environment. Set the ball-to-material ratio to 20:1, the ball milling time to 30 hours, and the ball milling speed to 500 rpm, and perform ball milling to obtain the precursor.

[0051] (3) The precursor was transferred to a high-pressure reactor, and a mixed gas with a H2:N2 molar ratio of 3:1 was introduced. The reaction pressure was controlled at 10 MPa, the reaction temperature at 500 °C, and the reaction time at 10 hours. After the reaction was completed, the mixture was cooled to room temperature and the ammonia synthesis catalyst was obtained.

[0052] Example 6 This embodiment provides a method for preparing an ammonia synthesis catalyst, including the following steps: (1) Weigh 54.23g FeCl3•6H2O, 12.26g LiOH•H2O, 37.34g CeCl3•7H2O and 30.08g urea.

[0053] (2) Add the above raw materials into the ball mill jar of the high-energy ball mill, and fill the ball mill jar with argon gas to remove air and ensure an inert environment. Set the ball-to-material ratio to 15:1, the ball milling time to 15 hours, and the ball milling speed to 500 rpm, and perform ball milling to obtain the precursor.

[0054] (3) The precursor was transferred to a high-pressure reactor, and a mixed gas with a H2:N2 molar ratio of 3:1 was introduced. The reaction pressure was controlled at 4 MPa, the reaction temperature at 400 °C, and the reaction time at 8 hours. After the reaction was completed, the mixture was cooled to room temperature and the ammonia synthesis catalyst was obtained.

[0055] Comparative Example 1 This comparative example provides a method for preparing an ammonia synthesis catalyst, comprising the following steps: (1) Weigh out 55.29g FeCl3•6H2O, 8.58g LiOH•H2O, 36.13g MgCl2•6H2O and 30.63g urea.

[0056] (2) Add the above raw materials into the ball mill jar of the high-energy ball mill, and fill the ball mill jar with argon gas to remove air and ensure an inert environment. Set the ball-to-material ratio to 15:1, the ball milling time to 15 hours, and the ball milling speed to 400 rpm, and perform ball milling to obtain the precursor.

[0057] (3) The precursor was transferred to a high-pressure reactor, and a mixed gas with a H2:N2 molar ratio of 3:1 was introduced. The reaction pressure was controlled at 7 MPa, the reaction temperature at 400 °C, and the reaction time at 7 hours. After the reaction was completed, the mixture was cooled to room temperature and the ammonia synthesis catalyst was obtained.

[0058] Comparative Example 2 This comparative example provides a method for preparing an ammonia synthesis catalyst, comprising the following steps: (1) Weigh 67.48g FeCl3•6H2O, 10.48g LiOH•H2O, 22.05g LaCl3•6H2O and 18.71g urea.

[0059] (2) Add the above raw materials into the ball mill jar of the high-energy ball mill, and fill the ball mill jar with argon gas to remove air and ensure an inert environment. Set the ball-to-material ratio to 15:1, the ball milling time to 5 hours, and the ball milling speed to 400 rpm, and perform ball milling to obtain the precursor.

[0060] (3) The precursor was transferred to a high-pressure reactor, and a mixed gas with a H2:N2 molar ratio of 3:1 was introduced. The reaction pressure was controlled at 7 MPa, the reaction temperature at 500 °C, and the reaction time at 5 hours. After the reaction was completed, the mixture was cooled to room temperature and the ammonia synthesis catalyst was obtained.

[0061] Comparative Example 3 This comparative example provides a method for preparing an ammonia synthesis catalyst, comprising the following steps: (1) Weigh 54.23g FeCl3•6H2O, 12.26g LiOH•H2O, 37.34g CeCl3•7H2O and 30.08g urea.

[0062] (2) Add the above raw materials into the ball mill jar of the high-energy ball mill, and fill the ball mill jar with argon gas to remove air and ensure an inert environment. Set the ball-to-material ratio to 15:1, the ball milling time to 15 hours, and the ball milling speed to 500 rpm, and perform ball milling to obtain the precursor.

[0063] (3) The precursor was transferred to a high-pressure reactor, and a mixed gas with a H2:N2 molar ratio of 3:1 was introduced. The reaction pressure was controlled at 2 MPa, the reaction temperature at 400 °C, and the reaction time at 10 hours. After the reaction was completed, the mixture was cooled to room temperature and the ammonia synthesis catalyst was obtained.

[0064] The catalysts obtained in Examples 1-3 and Comparative Examples 1-3 were used as catalysts, and hydrogen and nitrogen were used as raw materials to react on the catalysts to synthesize ammonia. The catalyst prepared in this example was tested under normal pressure, at a temperature of 250°C, a hydrogen-to-nitrogen ratio of 3:1, and a space velocity of 3000 mL / g·h. The ammonia content in the reaction products was detected by gas chromatography, and the ammonia synthesis rate was calculated. Before the reaction test, the catalyst was pretreated at 150°C with reaction gas (flow rate of 30 mL / min) for 1 h, and then the temperature was increased for activity testing. The results are shown in Table 1.

[0065] Table 1 ammonia synthesis reaction rate of catalyst

[0066] As can be seen from Table 1, the ammonia synthesis reaction rate in the examples was higher than 2.5 mmol / g·h. In the comparative example, the ammonia synthesis reaction rate decreased significantly after changing the type of raw materials, ball milling conditions, and high-temperature synthesis conditions.

[0067] In summary, the ammonia synthesis catalyst provided by this invention comprises, by mass, 20-60 parts of Fe nanoclusters, 1-5 parts of LiH, and 40-70 parts of lanthanide amine salts. Its catalytic conditions are a temperature of 200-300℃ and a pressure of 0.1-2 MPa. The preparation method is as follows: using iron, lithium, lanthanum, and nitrogen-containing compounds as raw materials, ball milling and activation treatment is performed under a protective atmosphere to obtain a precursor; the precursor undergoes a high-temperature and high-pressure reaction under a mixed gas of H2 and N2 to obtain the ammonia synthesis catalyst. The ammonia synthesis catalyst prepared by the above method has lower surface reactant adsorption energy and transition state energy than traditional ammonia synthesis catalysts, exhibiting excellent low-temperature and atmospheric-pressure ammonia synthesis catalytic performance; it does not contain precious metal elements, is low in cost, has a simple preparation method, and is pollution-free throughout the process, showing broad prospects for industrial application in ammonia synthesis and significant application value.

[0068] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A catalyst for ammonia synthesis, characterized in that, By mass, it comprises 20-60 parts of Fe nanoclusters, 1-5 parts of LiH, and 40-70 parts of amine salts of lanthanides.

2. The ammonia synthesis catalyst according to claim 1, characterized in that, The ammonia synthesis catalyst is used under the following catalytic conditions: temperature 200-300℃ and pressure 0.1-2 MPa.

3. The method for preparing the ammonia synthesis catalyst according to claim 1, characterized in that, Includes the following steps: The precursor was prepared by ball milling activation treatment under a protective atmosphere of argon using iron source, lithium source, lanthanum source and nitrogen-containing compound as raw materials; Under a mixed gas of H2 and N2, the precursor undergoes a high-temperature and high-pressure reaction to produce an ammonia synthesis catalyst.

4. The method for preparing the ammonia synthesis catalyst according to claim 3, characterized in that, The iron source is FeCl3•6H2O, the lithium source is LiOH•H2O, the lanthanum source is any one of LaCl3•6H2O, LaCl3•7H2O, CeCl3•6H2O, and CeCl3•7H2O, and the nitrogen-containing compound is urea.

5. The method for preparing the ammonia synthesis catalyst according to claim 3, characterized in that, The molar ratio of iron, lithium, lanthanum and nitrogen in the raw material is (2-4):(2-4):(1-2):(3-10).

6. The method for preparing the ammonia synthesis catalyst according to claim 3, characterized in that, The ball-to-material ratio for the ball milling activation treatment is 10-20:1, the ball milling activation treatment time is 10-30 hours, and the ball milling activation treatment speed is 300-500 rpm.

7. The method for preparing the ammonia synthesis catalyst according to claim 3, characterized in that, The ball-to-material ratio for the ball milling activation treatment is 15-20:1, and the ball milling activation treatment time is 10-15 hours.

8. The method for preparing the ammonia synthesis catalyst according to claim 3, characterized in that, The molar ratio of H2 to N2 is 3:

1.

9. The method for preparing the ammonia synthesis catalyst according to claim 3, characterized in that, The high-temperature and high-pressure reaction is carried out in a high-pressure reactor. The reaction pressure is 5-10 MPa, the reaction temperature is 300-500℃, and the reaction time is 5-10 hours.

10. The method for preparing the ammonia synthesis catalyst according to claim 3, characterized in that, The high-temperature and high-pressure reaction has a reaction pressure of 4-8 MPa, a reaction temperature of 400-500℃, and a reaction time of 5-8 hours.

Images