An ultra-low load ruthenium-based ammonia synthesis catalyst and a method for preparing the same
By combining the synergistic effect of modified mesoporous oxide supports and additives with quantitative process parameter control, the problems of high loading, high cost, and difficulty in balancing activity and stability of ruthenium-based catalysts have been solved, achieving efficient and economical ammonia synthesis.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JINCHUAN GROUP CO LTD
- Filing Date
- 2026-05-14
- Publication Date
- 2026-07-14
AI Technical Summary
Existing ruthenium-based ammonia synthesis catalysts suffer from problems such as high precious metal loading, high cost, insufficient support performance, easy agglomeration of active components, poor reproducibility of preparation processes, weak synergistic effect of additives, and insufficient stability.
A modified mesoporous oxide support is used, doped with element M (such as Mg, Ca, Ba, La, Ce), and promoters Li, Na, K, Rb, and Cs. The loading of ruthenium active component is controlled by formula to be 0.01%-0.5%, the particle size is ≤10nm, and the promoter dispersion is 0.6-0.95. Combined with the quantitative control of drying and reduction process parameters, the high activity and stability of the catalyst are ensured.
It significantly reduces ruthenium loading, enhances catalytic activity and stability, lowers production costs, is compatible with existing ammonia synthesis units, aligns with green and low-carbon trends, and enables efficient ammonia synthesis production.
Abstract
Description
Technical Field
[0001] This invention relates to the technical field of catalysts and their preparation methods, and particularly to an ultra-low supported ruthenium-based ammonia synthesis catalyst and its preparation method. Background Technology
[0002] The ammonia synthesis industry is a core foundational industry supporting modern agriculture and the chemical industry. Its products are not only key raw materials for nitrogen fertilizer production, but also widely used in pharmaceuticals, chemical fibers, fine chemicals, and other fields, playing a vital strategic role in national economic development. Catalysis technology is the core of the ammonia synthesis reaction. Traditional iron-based catalysts require high temperature and high pressure (30-50 MPa, 450-550℃) to operate, resulting in high energy consumption and low conversion rates. In contrast, ruthenium-based catalysts, due to their excellent low-temperature and low-pressure activity, have become a research hotspot in the field of ammonia synthesis catalysis in recent years.
[0003] However, existing ruthenium-based ammonia synthesis catalysts still face many technical bottlenecks that restrict their large-scale industrial application: High loading of precious metals, high cost: Ruthenium is a rare precious metal with a high market price. In existing technologies, the loading of ruthenium active components is generally 1%-5%. In order to ensure catalytic activity, a large amount of ruthenium needs to be consumed, resulting in high catalyst preparation costs, which makes it difficult to meet the economic requirements of industrial production. Insufficient support performance and easy aggregation of active components: Existing supports mostly use unmodified mesoporous oxides or carbon materials with low specific surface area (usually <300m² / g) and lack targeted electronic structure regulation, which makes ruthenium active components easy to aggregate, forming large particles with a particle size >10nm, resulting in insufficient exposure of active sites and a significant reduction in catalytic activity. The preparation process relies on experience and has poor repeatability: In the existing preparation methods, key process parameters such as drying temperature, reduction temperature, and dropping rate are mostly set by the operator's experience without quantitative control standards. This results in significant differences in particle size distribution and number of active sites between different batches of catalysts, and the performance fluctuation often exceeds 20%, which cannot guarantee the stability of industrial production. The synergistic effect of the additives is weak and the stability is insufficient: Although the addition of additives (such as alkali metals) can improve the activity of ruthenium, the low dispersion of additives in the existing technology (usually <0.5) makes them prone to agglomeration on the surface of the support to form ineffective sites. This not only fails to effectively enhance the catalytic performance of ruthenium, but also causes the catalyst to become deactivated due to the loss of additives during long-term reactions, resulting in a shortened service life.
[0004] In summary, how to ensure high activity, high stability and reproducibility of the catalyst while reducing the ruthenium loading is a core technical problem that urgently needs to be solved in the current industrialization process of ruthenium-based ammonia synthesis catalysts. Summary of the Invention
[0005] To address the aforementioned technical problems, this invention provides an ultra-low supported ruthenium-based ammonia synthesis catalyst and its preparation method.
[0006] To achieve the above objectives, the technical solution of the present invention is as follows: An ultra-low supported ruthenium-based ammonia synthesis catalyst, comprising: The carrier, the ruthenium active component loaded on the surface of the carrier, and the additives, wherein the loading amount ω of the ruthenium active component satisfies formula (1): ω = (m_Ru / (m_Ru + m_carrier + m_auxiliary agent)) × 100%; And 0.01%≤ω≤0.5%; The molar ratio n of the additive to the ruthenium active component satisfies n = n_additive / n_Ru, and 0.1 ≤ n ≤ 5.0; The carrier is a modified mesoporous oxide with a specific surface area S_BET≥500m² / g and a pore size D satisfying 2nm≤D≤50nm.
[0007] The modification treatment of the carrier includes the introduction of a dopant element M, and the doping amount x satisfies formula (2): x = (m_M / m_carrier) × 100%, and 0.5% ≤ x ≤ 10%; The doping element M is selected from at least one of Mg, Ca, Ba, La, and Ce.
[0008] The additive is selected from at least one of Li, Na, K, Rb, and Cs, and the dispersion θ of the additive on the catalyst surface satisfies θ = S_active / S_total, where S_active is the area of the active sites of the additive, S_total is the total coverage area of the additive, and 0.6 ≤ θ ≤ 0.95.
[0009] When this catalyst is used in the ammonia synthesis reaction, under the conditions of reaction temperature 300-500℃, pressure 0.1-10MPa, and space velocity 1000-10000h⁻¹, the ammonia formation rate r satisfies formula (3): r=10×(ω / 0.01%)×(S_BET / 500), and r≥10mmol・g_cat⁻¹・h⁻¹.
[0010] The ruthenium active component on the support surface has a particle size d that satisfies d≤10nm, and a particle size distribution span σ that satisfies σ=(d_max-d_min) / d_avg, where d_max is the maximum particle size, d_min is the minimum particle size, d_avg is the average particle size, and σ≤0.3.
[0011] This invention also provides a method for preparing an ultra-low supported ruthenium-based ammonia synthesis catalyst, comprising the following steps: S1. Prepare the carrier dispersion, and disperse it ultrasonically for 10-60 min according to the solid-liquid ratio R=m_carrier / V_solvent, controlling 1g:10mL≤R≤1g:50mL; S2. Prepare a mixed solution of ruthenium source and additive. Calculate the amount of ruthenium source and additive according to the loading formula ω=(m_Ru / (m_Ru+m_carrier+m_additive))×100%. Slowly add the ruthenium source and additive to the carrier dispersion and stir and soak for 2-24 hours. S3. Dry the impregnation solution at a temperature T1, where T1 satisfies the algorithm T1=25+5×t, and 60℃≤T1≤150℃, with a drying time of 4-12h. S4. The dried product is calcined and reduced in a reducing atmosphere. The reduction temperature T2 satisfies T2=300+30×k and 300℃≤T2≤600℃. The reduction time is 2-8h to obtain the target catalyst.
[0012] In step S2, the ruthenium source is selected from at least one of ruthenium chloride, ruthenium nitrate, and ruthenium acetylacetonate. The ruthenium ion concentration c in the mixed solution satisfies 0.001 mol / L ≤ c ≤ 0.05 mol / L, and the relationship between concentration c and loading ω conforms to c = 0.01 × ω.
[0013] In step S4, the reducing atmosphere is a mixture of hydrogen and an inert gas, the hydrogen gas fraction φ satisfies φ=20%+5×(ω / 0.01%), and 20%≤φ≤80%; the inert gas is selected from at least one of nitrogen, argon, and helium.
[0014] In step S3, the drying process adopts a gradient heating mode, and the heating rate v satisfies v=2+0.5×(T1 / 10), and 2℃ / min≤v≤10℃ / min, until the set temperature T1 is reached and then the drying is carried out at a constant temperature.
[0015] In step S2, the dropping rate v_drop satisfies v_drop=0.5+0.1×(V_mixture / 10mL), and 0.5mL / min≤v_drop≤5mL / min; during the dropping process, the pH value of the system is controlled between 3 and 8, and the pH value is adjusted by acid or alkali solution, with the adjustment rate matching the dropping rate to ensure that the pH fluctuation range is ≤±0.5.
[0016] The beneficial effects of this invention are: 1. Significantly reduces the amount of precious metals used, greatly improving economic efficiency: This invention strictly limits the loading of ruthenium active component to 0.01%-0.5% using formula (1). Compared with the loading of 1%-5% in the prior art, the ruthenium consumption is reduced by more than 80%. For example, compared with Comparative Example 1 (ruthenium loading 1.0%), Example 3 (ruthenium loading 0.5%) reduces the amount of ruthenium used by 50% under the premise of similar ammonia generation rate, directly reducing the cost of catalyst raw materials and laying an economic foundation for industrial application.
[0017] 2. Synergistic effect of support, additive, and active component significantly enhances catalytic activity: This invention uses a modified mesoporous oxide support and introduces doping elements such as Mg and La (doping amount 0.5%-10%), which can inhibit ruthenium particle agglomeration through electronic regulation and spatial confinement; at the same time, the additive dispersion θ=0.6-0.95 is controlled to ensure efficient synergy between the additive and the ruthenium active component. The ammonia generation rate of Example 2 reached 45.8 mmol・g_cat⁻¹・h⁻¹, which is 150% higher than that of Comparative Example 2 without support modification, and the ruthenium particle size is controlled within 10 nm, with a particle size distribution span σ≤0.3, and the active sites are fully exposed.
[0018] 3. Quantitative control of process parameters enhances repeatability and stability: This invention clarifies key process parameters through formulaic design, such as drying temperature T1 = 25 + 5 × t (t is the impregnation time), reduction temperature T2 = 300 + 30 × k (k is the molar ratio coefficient of the additives), and heating rate v = 2 + 0.5 × (T1 / 10). This achieves full quantitative control from raw material ratio to process flow, completely overcoming the limitations of traditional experience-based operations. Experimental verification shows that the catalyst prepared using the method of this invention exhibits ammonia generation rate fluctuation of ≤5% between different batches, far lower than the 15%-20% fluctuation range of existing technologies, ensuring the stability of industrial production.
[0019] 4. Adaptable to existing equipment, lowering the application threshold: The catalyst of this invention can work stably within a wide range of reaction conditions, including 300-500℃, 0.1-10MPa, and space velocity of 1000-10000h⁻¹. It is fully compatible with the process parameters of existing ammonia synthesis units, eliminating the need for large-scale modifications to production equipment. Only the catalyst needs to be replaced to achieve a technological upgrade, significantly reducing the application costs and modification risks for industrial enterprises.
[0020] 5. In line with the green and low-carbon trend, and with both environmental and social benefits: The high activity of the catalyst of this invention can achieve efficient ammonia synthesis at lower temperature and pressure, reducing energy consumption by 15%-20% compared with traditional iron-based catalysts; at the same time, the ultra-low ruthenium loading reduces the mining and consumption of rare and precious metals, which is in line with the development trend of efficient resource utilization and green chemical industry under the dual carbon background, and has significant environmental and social benefits. Detailed Implementation
[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of the invention.
[0022] This invention provides an ultra-low-loaded ruthenium-based ammonia synthesis catalyst and its preparation method, aiming to solve the technical problems of existing ruthenium-based catalysts having high ruthenium loading, high cost, and difficulty in balancing activity and stability.
[0023] Catalyst composition: The catalyst consists of a support, a ruthenium active component, and additives. The loading ω of the ruthenium active component is calculated using formula (1): ω = (m_Ru / (m_Ru+m_carrier+m_auxiliary))×100%, with a limit of 0.01%≤ω≤0.5%. This range can maximize the reduction of the amount of precious metal ruthenium while ensuring catalytic activity.
[0024] Carrier modification: The carrier is a modified mesoporous oxide (such as mesoporous SiO2, Al2O3 or TiO2) with a specific surface area S_BET≥500m² / g and a pore size D controlled within 2nm≤D≤50nm to ensure uniform dispersion of the ruthenium active component. The modification process introduces a doping element M (at least one of Mg, Ca, Ba, La, Ce), and the doping amount x is calculated according to formula (2): x = (m_M / m_carrier) × 100%, and 0.5% ≤ x ≤ 10%, which can improve the electronic conductivity and the number of active sites on the carrier surface.
[0025] Optimized formulation of additives: The additives are selected from at least one of Li, Na, K, Rb, and Cs, and the molar ratio with the ruthenium active component is: n = n_auxiliary agent / n_Ru, satisfying 0.1 ≤ n ≤ 5.0.
[0026] The dispersion of the additive on the catalyst surface, θ = S_active / S_total (where S_active is the area of the active sites of the additive and S_total is the total coverage area of the additive), needs to reach 0.6≤θ≤0.95 to enhance the catalytic performance of the ruthenium active component.
[0027] Preparation method steps: Preparation of carrier dispersion: According to the solid-liquid ratio R=m_carrier / V_solvent (1g:10mL≤R≤1g:50mL), add the modified mesoporous oxide to the solvent (deionized water or ethanol) and ultrasonically disperse for 10-60min to ensure that the carrier is uniformly dispersed without agglomeration.
[0028] Preparation and Impregnation of the Mixed Solution: Ruthenium chloride, ruthenium nitrate, or ruthenium acetylacetonate was selected as the ruthenium source. The amounts of the ruthenium source and auxiliary agent were calculated according to the loading formula ω. A mixed solution was prepared, wherein the ruthenium ion concentration c satisfied 0.001 mol / L ≤ c ≤ 0.05 mol / L, and c = 0.01 × ω (ω is expressed as a percentage). The mixed solution was slowly added dropwise to the carrier dispersion at a dropping rate v_drop = 0.5 + 0.1 × (V_mixed solution / 10 mL) (0.5 mL / min ≤ v_drop ≤ 5 mL / min). The mixture was stirred and impregnated for 2-24 hours. During the addition process, the pH of the system was controlled between 3 and 8, with pH fluctuations ≤ ±0.5.
[0029] Drying treatment: The impregnation solution is dried using a gradient temperature increase mode, with the temperature increase rate being: v=2+0.5×(T1 / 10) (2℃ / min≤v≤10℃ / min); The drying temperature T1 = 25 + 5 × t (t is the soaking time in hours), and 60℃ ≤ T1 ≤ 150℃, and the drying is carried out at a constant temperature for 4-12 hours.
[0030] Calcination and reduction: The dried product is placed in a reducing atmosphere (a mixture of hydrogen and inert gas, with the hydrogen gas integral φ = 20% + 5 × (ω / 0.01%) and 20% ≤ φ ≤ 80%) for calcination and reduction. The reduction temperature is T2 = 300 + 30 × k (k is the molar ratio coefficient of the additive, k = n / 0.1), and 300℃ ≤ T2 ≤ 600℃. The reduction time is 2-8 h to obtain the target catalyst.
[0031] Catalyst performance indicators: The particle size d of the ruthenium active component on the support surface is ≤10 nm, and the particle size distribution range is: σ = (d_max - d_min) / d_avg (d_max is the maximum particle size, d_min is the minimum particle size, and d_avg is the average particle size). And σ≤0.3.
[0032] When this catalyst is used in the ammonia synthesis reaction, under the conditions of reaction temperature 300-500℃, pressure 0.1-10MPa, and space velocity 1000-10000h⁻¹, the ammonia formation rate r satisfies formula (3): r=10×(ω / 0.01%)×(S_BET / 500), and r≥10mmol・g_cat⁻¹・h⁻¹.
[0033] Examples and Comparative Examples: Preparation of experimental materials: Ruthenium source: Ruthenium chloride (RuCl3・3H2O, purity 99.9%) Support: Mesoporous SiO2 (specific surface area 550 m² / g, pore size 10 nm), modified and doped with La (doping amount x=5%). Additive: Cesium carbonate (Cs2CO3, purity 99.9%) Solvent: Deionized water; pH adjuster: Dilute hydrochloric acid and sodium hydroxide solution Example 1: Loading amount ω=0.05% (calculated according to formula (1), m_Ru=0.005g, m_carrier=9.945g, m_auxiliary agent=0.05g) The molar ratio of the adjuvants is n=1.0 (n_Cs / n_Ru=1.0). Preparation parameters: Solid-liquid ratio R = 1g:20mL, ultrasonically dispersed for 30min; Ruthenium ion concentration c = 0.0005 mol / L; Dropping rate v_drop=1mL / min; immersion time t=8h; drying temperature T1=25+5×8=65℃; heating rate v=3℃ / min. The reduction temperature T2 = 300 + 30 × (1.0 / 0.1) = 600℃, the hydrogen gas integral φ = 45%, and the reduction time is 4h.
[0034] Example 2: Loading amount ω=0.2% (m_Ru=0.02g, m_carrier=9.78g, m_auxiliary agent=0.2g) The molar ratio of the adjuvants is n=2.0 (n_Cs / n_Ru=2.0). Preparation parameters: Solid-liquid ratio R = 1g:30mL, ultrasonic dispersion for 40min; Ruthenium ion concentration c = 0.002 mol / L; Drop rate v_drop = 2 mL / min; The soaking time t = 12h, the drying temperature T1 = 25 + 5 × 12 = 85℃, and the heating rate v = 4℃ / min; The reduction temperature T2 = 300 + 30 × (2.0 / 0.1) = 900℃ (adjusted to 600℃ to meet the essential requirements), the hydrogen gas integral φ = 60%, and the reduction time is 6h.
[0035] Example 3: Loading amount ω=0.5% (m_Ru=0.05g, m_carrier=9.45g, m_auxiliary agent=0.5g) The molar ratio of the adjuvants is n=5.0 (n_Cs / n_Ru=5.0). Preparation parameters: Solid-liquid ratio R = 1g:50mL, ultrasonic dispersion for 60min; Ruthenium ion concentration c = 0.005 mol / L; Drop rate v_drop = 5 mL / min; The soaking time t = 24h, the drying temperature T1 = 25 + 5 × 24 = 145℃, and the heating rate v = 8℃ / min; The reduction temperature T2 = 300 + 30 × (5.0 / 0.1) = 1800℃ (adjusted to 600℃), the hydrogen gas integral φ = 80%, and the reduction time is 8h.
[0036] Comparative Example 1 (Overload): The load ω = 1.0% (outside the range of 0.01%-0.5%), and the other parameters are the same as in Example 2.
[0037] Comparative Example 2 (without carrier modification): The carrier was not doped with La (no modification treatment was performed), and the other parameters were the same as in Example 2.
[0038] Comparative Example 3 (Deviation from Reduction Temperature): The reduction temperature T2 = 250℃ (below the lower limit of 300℃), and the other parameters are the same as in Example 2.
[0039] Performance test results: , Test conditions: reaction temperature 400℃, pressure 5MPa, space velocity 5000h⁻¹. The data show that Examples 1-3 all met the ammonia generation rate r ≥ 10mmol・g_cat⁻¹・h⁻¹, and had uniform particle size distribution; Comparative Example 1, although slightly more active, had doubled ruthenium loading and severe particle agglomeration, significantly increasing cost; Comparative Example 2, due to lack of carrier modification, experienced an activity decrease of over 60%; Comparative Example 3, due to insufficient reduction temperature, did not meet the minimum required standard.
[0040] In summary, this invention has successfully developed an ultra-low-loaded ruthenium-based ammonia synthesis catalyst and its preparation method through systematic component design and quantitative process control. It effectively solves the core pain points of the industry, such as high loading, high cost, and difficulty in balancing activity and stability of traditional ruthenium-based catalysts, and has significant technological innovation value and broad industrial application prospects.
[0041] At the catalyst component design level, the core breakthrough lies in precisely limiting the loading of the ruthenium active component to an ultra-low range of 0.01%-0.5% using formula (1). Compared with the conventional loading of 1%-5% for traditional ruthenium-based catalysts, the consumption of the precious metal ruthenium is reduced by more than 80%, significantly compressing production costs. To balance the contradiction between low loading and high activity, this invention constructs a synergistic system of modified support-active component-auxiliary agent: The modified mesoporous support provides ample dispersion space for ruthenium active components with its high specific surface area of ≥500m² / g and suitable pore size of 2-50nm. The introduction of doping elements such as Mg and La (doping amount 0.5%-10%) further improves the electronic conductivity of the carrier and the number of active sites; Li, Cs and other promoters significantly enhance the intrinsic catalytic activity of the ruthenium active component through an optimized molar ratio of 0.1-5.0 and a high dispersion of ≥0.6. The synergistic effect of the three ensures that the catalyst maintains excellent performance even under ultra-low loading.
[0042] In terms of the preparation process, this invention innovatively adopts a multi-parameter formulaic control strategy. Through quantitative algorithms such as drying temperature T1=25+5×t, reduction temperature T2=300+30×k, and heating rate v=2+0.5×(T1 / 10), key variables such as impregnation time and additive ratio are precisely correlated with process parameters. This completely eliminates the batch performance fluctuation problem caused by reliance on experience in traditional preparation processes, achieving controllability and repeatability in catalyst preparation. The data from the examples fully verify the scientific validity of this process. In Example 1, with a loading of only 0.05%, the ammonia generation rate reached 11.2 mmol·g_cat⁻¹·h⁻¹, far exceeding the minimum standard; Example 3 showed an activity of up to 102.3 mmol・g_cat⁻¹・h⁻¹ at a loading of 0.5%, which was close to that of Comparative Example 1 with double the loading, but with a 50% reduction in ruthenium usage, resulting in a significant cost advantage.
[0043] From an application perspective, the catalyst of this invention is adaptable to a wide range of reaction conditions (300-500℃, 0.1-10MPa), and is directly compatible with existing ammonia synthesis plants. It allows for technological upgrades without large-scale equipment modifications, significantly lowering the industrial conversion threshold. Furthermore, the catalyst exhibits excellent adaptability, allowing for flexible adjustments to loading and process parameters to meet diverse production needs, from small-scale fine chemical plants to large-scale nitrogen fertilizer enterprises. Comparative data further demonstrate the necessity of the key parameter design in this invention: Comparative Example 2, without carrier modification, showed an activity decrease of over 60%, and Comparative Example 3, with insufficient reduction temperature, failed to meet the activity standard, fully showcasing the synergistic importance of component design and process control.
[0044] Example 4 A method for preparing an ultra-low supported ruthenium-based ammonia synthesis catalyst includes the following steps: S1. Prepare the carrier dispersion by ultrasonic dispersion for 10 min, with a solid-liquid ratio R = m_carrier / V_solvent and R controlled at 1 g: 10 mL. S2. Prepare a mixed solution of ruthenium source and additive. Calculate the amount of ruthenium source and additive according to the loading formula ω=(m_Ru / (m_Ru+m_carrier+m_additive))×100%. Slowly add the ruthenium source and additive to the carrier dispersion and stir and soak for 2 hours. S3. Dry the impregnation solution at a temperature T1, where T1 satisfies the algorithm T1=25+5×t, and T1 is 60℃, with a drying time of 4h. S4. The dried product is calcined and reduced in a reducing atmosphere. The reduction temperature T2 satisfies T2=300+30×k and T2 is 300℃. The reduction time is 2h to obtain the target catalyst.
[0045] In step S2, the ruthenium source is ruthenium chloride, the ruthenium ion concentration c in the mixed solution satisfies c = 0.001 mol / L, and the relationship between concentration c and loading ω conforms to c = 0.01 × ω.
[0046] In step S4, the reducing atmosphere is a mixture of hydrogen and an inert gas, the hydrogen gas integral φ satisfies φ=20%+5×(ω / 0.01%), and φ is 20%; the inert gas is argon.
[0047] In step S3, the drying process adopts a gradient heating mode, with the heating rate v satisfying v=2+0.5×(T1 / 10) and v being 2℃ / min, until the set temperature T1 is reached and then the drying is carried out at a constant temperature.
[0048] In step S2, the dropping rate v_drop satisfies v_drop=0.5+0.1×(V_mixture / 10mL) and v_drop is 0.5mL / min; the pH of the system during the dropping process is 3, and the pH is adjusted using an acid solution or an alkaline solution, with the adjustment rate matching the dropping rate to ensure that the pH fluctuation range is ≤±0.5.
[0049] Example 5 A method for preparing an ultra-low supported ruthenium-based ammonia synthesis catalyst includes the following steps: S1. Prepare the carrier dispersion by ultrasonic dispersion for 60 min, according to the solid-liquid ratio R = m_carrier / V_solvent, controlling R to be 1g:50mL. S2. Prepare a mixed solution of ruthenium source and additive. Calculate the amount of ruthenium source and additive according to the loading formula ω=(m_Ru / (m_Ru+m_carrier+m_additive))×100%. Slowly add the ruthenium source and additive to the carrier dispersion and stir and soak for 24 hours. S3. Dry the impregnation solution at a temperature T1, where T1 satisfies the algorithm T1=25+5×t, and T1 is 150℃, with a drying time of 12h. S4. The dried product is calcined and reduced in a reducing atmosphere. The reduction temperature T2 satisfies T2=300+30×k and T2 is 600℃. The reduction time is 8h to obtain the target catalyst.
[0050] In step S2, the ruthenium source is ruthenium acetylacetonate, the ruthenium ion concentration c in the mixed solution satisfies c = 0.05 mol / L, and the relationship between concentration c and loading ω conforms to c = 0.01 × ω.
[0051] In step S4, the reducing atmosphere is a mixture of hydrogen and an inert gas, the hydrogen integral φ satisfies φ=20%+5×(ω / 0.01%), and φ is 80%; the inert gas is helium.
[0052] In step S3, the drying process adopts a gradient heating mode, with the heating rate v satisfying v=2+0.5×(T1 / 10) and v being 10℃ / min, until the set temperature T1 is reached and then the drying is carried out at a constant temperature.
[0053] In step S2, the dropping rate v_drop satisfies v_drop=0.5+0.1×(V_mixture / 10mL) and v_drop is 5mL / min; the pH of the system during the dropping process is 8, and the pH is adjusted using an acid solution or an alkaline solution, with the adjustment rate matching the dropping rate to ensure that the pH fluctuation range is ≤±0.5.
[0054] In summary, this invention achieves an optimal balance between catalyst cost, activity, and stability through dual innovations of ultra-low loading precision design and quantitative process control. It not only provides an efficient and economical catalytic solution for the ammonia synthesis industry, but also aligns with the current development trend of cost reduction, efficiency improvement, and green and low-carbon development in the chemical industry. It has extremely high academic research value and industrial application prospects, and is expected to promote the large-scale industrial application of ruthenium-based ammonia synthesis catalysts.
[0055] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.
Claims
1. A low-supported ruthenium-based ammonia synthesis catalyst, characterized in that, include: The carrier, the ruthenium active component loaded on the surface of the carrier, and the additives, wherein the loading amount ω of the ruthenium active component satisfies formula (1): ω = (m_Ru / (m_Ru + m_carrier + m_auxiliary agent)) × 100%; And 0.01%≤ω≤0.5%; The molar ratio n of the additive to the ruthenium active component satisfies n = n_additive / n_Ru, and 0.1 ≤ n ≤ 5.0; The carrier is a modified mesoporous oxide with a specific surface area S_BET≥500m² / g and a pore size D satisfying 2nm≤D≤50nm.
2. The ultra-low supported ruthenium-based ammonia synthesis catalyst according to claim 1, characterized in that, The modification treatment of the carrier includes the introduction of a dopant element M, and the doping amount x satisfies formula (2): x = (m_M / m_carrier) × 100%, and 0.5% ≤ x ≤ 10%; The doping element M is selected from at least one of Mg, Ca, Ba, La, and Ce.
3. The ultra-low supported ruthenium-based ammonia synthesis catalyst according to claim 1, characterized in that, The additive is selected from at least one of Li, Na, K, Rb, and Cs, and the dispersion θ of the additive on the catalyst surface satisfies θ = S_active / S_total, where S_active is the area of the active sites of the additive, S_total is the total coverage area of the additive, and 0.6 ≤ θ ≤ 0.
95.
4. The ultra-low supported ruthenium-based ammonia synthesis catalyst according to claim 1, characterized in that, When this catalyst is used in the ammonia synthesis reaction, under the conditions of reaction temperature 300-500℃, pressure 0.1-10MPa, and space velocity 1000-10000h⁻¹, the ammonia formation rate r satisfies formula (3): r=10×(ω / 0.01%)×(S_BET / 500), and r≥10mmol・g_cat⁻¹・h⁻¹.
5. The ultra-low supported ruthenium-based ammonia synthesis catalyst according to claim 1, characterized in that, The ruthenium active component on the support surface has a particle size d that satisfies d≤10nm, and a particle size distribution span σ that satisfies σ=(d_max-d_min) / d_avg, where d_max is the maximum particle size, d_min is the minimum particle size, d_avg is the average particle size, and σ≤0.
3.
6. A method for preparing an ultra-low supported ruthenium-based ammonia synthesis catalyst as described in any one of claims 1-3, characterized in that, Includes the following steps: S1. Prepare the carrier dispersion, and disperse it ultrasonically for 10-60 min according to the solid-liquid ratio R=m_carrier / V_solvent, controlling 1g:10mL≤R≤1g:50mL; S2. Prepare a mixed solution of ruthenium source and additive. Calculate the amount of ruthenium source and additive according to the loading formula ω=(m_Ru / (m_Ru+m_carrier+m_additive))×100%. Slowly add the ruthenium source and additive to the carrier dispersion and stir and soak for 2-24 hours. S3. Dry the impregnation solution at a temperature T1, where T1 satisfies the algorithm T1=25+5×t, and 60℃≤T1≤150℃, with a drying time of 4-12h. S4. The dried product is calcined and reduced in a reducing atmosphere. The reduction temperature T2 satisfies T2=300+30×k and 300℃≤T2≤600℃. The reduction time is 2-8h to obtain the target catalyst.
7. The method for preparing an ultra-low supported ruthenium-based ammonia synthesis catalyst according to claim 6, characterized in that, In step S2, the ruthenium source is selected from at least one of ruthenium chloride, ruthenium nitrate, and ruthenium acetylacetonate. The ruthenium ion concentration c in the mixed solution satisfies 0.001 mol / L ≤ c ≤ 0.05 mol / L, and the relationship between concentration c and loading ω conforms to c = 0.01 × ω.
8. The method for preparing an ultra-low supported ruthenium-based ammonia synthesis catalyst according to claim 6, characterized in that, In step S4, the reducing atmosphere is a mixture of hydrogen and an inert gas, the hydrogen gas integral φ satisfies φ=20%+5×(ω / 0.01%), and 20%≤φ≤80%; the inert gas is selected from at least one of nitrogen, argon, and helium.
9. The method for preparing an ultra-low supported ruthenium-based ammonia synthesis catalyst according to claim 6, characterized in that, In step S3, the drying process adopts a gradient heating mode, and the heating rate v satisfies v=2+0.5×(T1 / 10), and 2℃ / min≤v≤10℃ / min, until the set temperature T1 is reached and then constant temperature drying is performed.
10. The method for preparing an ultra-low supported ruthenium-based ammonia synthesis catalyst according to claim 6, characterized in that, In step S2, the dropping rate v_drop satisfies v_drop=0.5+0.1×(V_mixture / 10mL), and 0.5mL / min≤v_drop≤5mL / min; during the dropping process, the pH value of the system is controlled between 3 and 8, and the pH value is adjusted by acid or alkaline solution, with the adjustment rate matching the dropping rate to ensure that the pH fluctuation range is ≤±0.5.