Ru / MgO-La2O3 composite catalyst applied to ammonia decomposition and preparation method of Ru / MgO-La2O3 composite catalyst

Abstract

The invention provides a Ru / MgO-La2O3 catalyst for efficiently catalyzing ammonia decomposition to produce hydrogen as well as a preparation method and application of the Ru / MgO-La2O3 catalyst, and belongs to the technical field of ammonia decomposition to produce hydrogen. The catalyst is prepared by taking noble metal Ru as an active component and MgO-La2O3 composite oxide as a carrier through a coprecipitation method and an impregnation method. The loading capacity of Ru in the catalyst is 1-20 wt%, and the dispersity and ammonia decomposition reaction activity of Ru are remarkably improved by optimizing the interaction between the carrier and the metal-carrier. The preparation method comprises the following steps: mixing a ruthenium precursor with the MgO-La2O3 carrier, and carrying out drying, calcining and reduction treatment to obtain the high-dispersion Ru / MgO-La2O3 catalyst. Compared with the existing noble metal-based catalyst, the composite carrier regulates and controls the electronic structure of Ru, so that the composite carrier shows excellent ammonia decomposition activity and stability at low temperature (350-550 DEG C), the ammonia conversion rate at 450 DEG C can reach 99.5%, and efficient total conversion is still kept under the conditions of high temperature and high space velocity. The Ru / MgO-La2O3 catalyst obtained by the method is superior to most reported catalysts under the same condition, the catalyst preparation process is simple, the cost is controllable, the method is suitable for large-scale production, and an efficient and economical technical scheme is provided for the field of hydrogen energy storage and transportation.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen energy storage and transportation and catalytic materials technology, specifically to a method for preparing a Ru / MgO-La2O3 composite catalyst and its application in hydrogen production from ammonia decomposition. By optimizing the interactions between support components and the dispersion of active metals, this catalyst significantly improves the efficiency of low-temperature ammonia decomposition while also ensuring the economical utilization of the precious metal Ru. Background Art

[0002] Hydrogen energy, due to its zero-carbon emissions, is considered a core component of the future energy system. However, its flammability and explosiveness, as well as material embrittlement during storage and transportation, severely restrict its large-scale application. Using ammonia as a hydrogen carrier for on-site hydrogen production effectively avoids the risks of direct storage and transportation of hydrogen. Furthermore, ammonia's high hydrogen storage density (17.6 wt%), established infrastructure, and carbon-free properties make it a key breakthrough in the hydrogen economy. However, the ammonia decomposition reaction requires a catalyst, and its high activation energy and poor low-temperature activity require urgent solutions.

[0003] Currently, precious metal ruthenium (Ru)-based catalysts have attracted much attention due to their excellent low-temperature ammonia decomposition activity. For example, patent CN113058595A uses a colloidal precipitation method to load Ru nanoparticles onto metal oxide supports, achieving high dispersion of Ru by enhancing the metal-support interaction, significantly improving low-temperature catalytic performance; patent CN112973679A uses a solid-phase ball milling method to prepare Ru-based catalysts at 350-500 °C. o C. However, the high cost of the precious metal Ru greatly limits its industrial application. Although the development of non-precious metal catalysts (such as Fe, Co, and Ni) has become a research hotspot, their low-temperature activity is insufficient and they are easily deactivated by nitride formation or particle sintering. For example, the Fe / SiC catalyst disclosed in patent CN115318317A is low-cost, but Fe easily forms passivating nitrides at low temperatures, and particle agglomeration causes a sharp drop in activity at high temperatures; the Ni / MgAl2O4 catalyst prepared by patent CN113332987A using the hydrothermal-impregnation method improves dispersibility by controlling the carrier morphology, but the preparation process is complex and the high-temperature stability is insufficient.

[0004] In the prior art, strategies for improving the performance of non-precious metal catalysts focus on support functionalization design, including: (1) introducing alkaline oxides (such as MgO and La2O3) to adjust the support's acid-base properties to optimize the electronic state of the active metal; (2) inhibiting metal particle sintering through the strong interaction of composite oxide supports (such as CeO2-La2O3 and MgO-Al2O3). However, improvements to Ru-based catalysts have mostly focused on a single support system (such as MgO and La2O3), failing to fully utilize the synergistic effect of composite supports. For example, although the Ru / MgO catalyst in patent CN112973679A has certain activity, the MgO support is prone to migration and agglomeration of Ru particles due to weak interactions at high temperatures; and although the strong alkalinity of La2O3 is conducive to ammonia adsorption and activation, its low specific surface area limits the metal dispersion. In addition, composite supports prepared by traditional impregnation methods often have uneven component distribution, making it difficult to achieve atomic-level interaction between MgO and La2O3, resulting in insufficient support structural stability.

[0005] Based on this, the present invention constructs a MgO-La2O3 composite carrier by co-precipitation, utilizes the strong interaction between the two phases to form a stable structure, and loads a low content of Ru (0.1~20 wt%) by incipient wetness impregnation. This design has the following advantages: (1) The coordinated regulation of MgO and La2O3 enhances the alkalinity of the carrier and promotes the adsorption and dissociation of NH3; (2) The composite carrier can effectively anchor Ru nanoparticles (1.5~5.0 nm) and inhibit high-temperature sintering; (3) The low Ru loading combined with high dispersion characteristics significantly reduces the catalyst cost. Experiments show that the catalyst is 450~550 o C, an ammonia conversion rate of ≥99% can be achieved, which combines high efficiency, stability and economy, and provides a new solution for the industrial promotion of ammonia decomposition hydrogen production technology. Summary of the Invention

[0006] The present invention provides a Ru / MgO-La2O3 catalyst for ammonia decomposition hydrogen production reaction and a preparation method thereof, characterized in that: the active component of the catalyst is metallic Ru, and the carrier is a MgO-La2O3 composite oxide; the Ru loading is 0.1-20 wt% by mass, and the molar ratio of MgO to La2O3 in the carrier is 0.1:1-20:1; the particle size of the Ru nanoparticles in the catalyst is 1.5-5.0 nm, and they are uniformly dispersed on the surface of the MgO-La2O3 carrier. The MgO and La2O3 in the carrier form a strong interaction through coprecipitation, significantly improving the dispersibility and anti-sintering performance of Ru. The present invention optimizes the synergistic effect between the carrier components and the efficient utilization of Ru active sites, so that the catalyst can be used at low temperatures (450-550 o C) can achieve a high ammonia conversion rate (≥99%), which is suitable for industrial ammonia decomposition and hydrogen production scenarios.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: A ruthenium-based catalyst, its preparation method, and its use in hydrogen production by decomposing ammonia. The catalyst composition is Ru / MgO-La2O3, wherein the Ru loading is 1-20 wt% and the molar ratio of MgO to La2O3 is 0.1:1-20:1.

[0008] Based on the above technical solution, the preparation method of the catalyst is a co-precipitation-incipient wetness impregnation method, which specifically includes the following steps.

[0009] Based on the above technical solution, preferably, the coprecipitation-incipient wetness impregnation method is selected. The catalyst preparation method includes the following steps: (1) A magnesium source and a lanthanum source are dissolved in deionized water to form a mixed solution, a precipitant is added to adjust the pH to 8-12, and after stirring and aging, the solution is washed, dried, and calcined to obtain a MgO-La2O3 composite support; (2) An equal volume of Ru precursor solution is impregnated on the support obtained in step (1), and a Ru / MgO-La2O3 catalyst is obtained after drying, calcining and reducing.

[0010] The magnesium source in step (1) is magnesium chloride, magnesium sulfate, magnesium acetate or magnesium nitrate, preferably magnesium nitrate; the lanthanum source is lanthanum nitrate, lanthanum oxide, lanthanum fluoride, lanthanum carbonate, lanthanum chloride or lanthanum acetate, preferably lanthanum nitrate; the precipitant is ammonia water, potassium hydroxide, hydrogen sulfide, sodium carbonate, ammonium carbonate or sodium hydroxide, preferably sodium carbonate, preferably sodium carbonate.

[0011] The Ru precursor in step (2) is RuCl3, Ru(NO3)3, K2RuO4 or ruthenium acetylacetonate, preferably RuCl3.

[0012] Based on the above technical solution, preferably, by adjusting the ruthenium loading to 0.1wt%~20wt%, the catalyst 1Ru / MgO-La2O3~20Ru / MgO-La2O3 is obtained, preferably 1Ru / MgO-La2O3.

[0013] Based on the above technical solution, preferably, the molar ratio of the magnesium source to the lanthanum source in step (1) is 0.1:1~20:1, preferably 1:0.5; the Ru loading amount is controlled by the concentration of the precursor solution to be 0.1~20 wt%, preferably 1~10 wt%.

[0014] Based on the above technical solution, preferably, the aging time in step (1) is 6 to 24 h, preferably 12 h; the drying temperature is 80 to 120 o C, preferably 100 o C; drying time is 12~24 h, preferably 12 h; solid powder is 100o C and dried for 12 h to remove excess water to obtain a powdered carrier precursor.

[0015] Based on the above technical solution, preferably, the calcination temperature of the dried precursor in the air atmosphere in step (1) is 300~800 o C, preferably 600 o C; calcination time is 3~8 h, preferably 5 h; heating rate is 5 o C / min. After cooling, a powdered carrier was obtained.

[0016] Based on the above technical solution, preferably, the drying temperature after dipping in step (2) is 60~100 o C, preferably 100 o C; drying time is 4 to 24 hours, preferably 12 hours.

[0017] Based on the above technical solution, preferably, the reducing gas in step (2) is a hydrogen-argon mixture, and the reducing temperature is 400-800 o C, preferably 550 o C; the reduction time is 1~6 h, preferably 1 h, and the heating rate is 10 o C / min.

[0018] The present invention provides a Ru / MgO-La2O3 catalyst prepared by the preparation method described in the above technical solution, characterized in that the Ru nanoparticles of the ruthenium-based catalyst are uniformly dispersed on the surface of the carrier and form a strong metal-support interaction (SMSI) with the MgO-La2O3 carrier, thereby inhibiting high-temperature sintering.

[0019] The present invention also provides the use of the catalyst described in the above technical solution in the ammonia decomposition hydrogen production reaction, characterized in that the reaction temperature is 350~700 o C, preferably 350~550 o C; space velocity range is 2000~100000 ml / g / h, preferably 6000~30000 ml / g / h; ammonia conversion rate is ≥99%.

[0020] Based on the above technical solution, preferably, the reaction temperature is 300~1000 o C, more preferably 350~550 o C; using hydrogen as reducing agent, the reduction temperature is 400~800 o C, preferably 550 o C, the hydrogen pressure is 0.1 MPa; the reaction time is 1 to 12 h, preferably 1 to 3 h.

[0021] Compared with the prior art, the present invention has the following beneficial effects: (1) High dispersibility and strong interaction: The MgO-La2O3 composite support was constructed by co-precipitation method, and a stable structure was formed between the two phases, providing abundant anchoring sites, so that the Ru nanoparticles were evenly dispersed (1.5~5.0 nm) and there was a strong electronic synergistic effect between them and the support, which significantly improved the low-temperature catalytic activity.

[0022] (2) Low temperature efficiency: 450~550 o C can achieve efficient decomposition of ammonia, which is 50~100 lower than the reaction temperature of traditional Ru-based catalysts (such as Ru / MgO, Ru / La2O3). o C, energy consumption reduced by more than 30%.

[0023] (3) Low cost and high stability: Through the low Ru loading (1~10 wt%) and the anti-sintering properties of the composite carrier, the amount of precious metals can be greatly reduced while ensuring activity, making it suitable for industrial continuous production.

[0024] (4) The process is simple and controllable: The co-precipitation-impregnation method has a simple preparation process, and parameters such as the ratio of carrier components and Ru loading can be precisely controlled, with good reproducibility and easy large-scale preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The XRD spectra of Ru / MgO-La2O3 prepared by co-precipitation method in Example 1 of the present invention are compared with those of Ru / MgO and Ru / La2O3 catalysts in comparative examples.

[0026] Figure 2 2-TPR diagrams of Ru / MgO-La2O3 prepared by co-precipitation method in Example 1 of the present invention and comparison examples of Ru / MgO and Ru / La2O3 catalysts are compared.

[0027] Figure 3 NH3-TPD diagram comparison of Ru / MgO-La2O3 prepared by co-precipitation method in Example 1 of the present invention and Ru / MgO and Ru / La2O3 catalysts in comparative examples.

[0028] Figure 4 2-TPD diagrams of Ru / MgO-La2O3 prepared by co-precipitation method in Example 1 of the present invention and comparison examples of Ru / MgO and Ru / La2O3 catalysts are compared.

[0029] Figure 5 TEM images of Ru / MgO-La2O3 prepared by co-precipitation method in Example 1 of the present invention are compared with those of Ru / MgO and Ru / La2O3 catalysts in comparative examples. DETAILED DESCRIPTION

[0030] In order to explain the present invention more clearly, the present invention is further described below in conjunction with preferred embodiments. Those skilled in the art should understand that the following specific description is illustrative rather than restrictive and should not be used to limit the scope of protection of the present invention.

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Example

[0032] Synthesis of MgO-La2O3-5.6 support using co-precipitation method: (1) Dissolve magnesium nitrate (Mg(NO3)2·6H2O, 9.83 g) and lanthanum nitrate (La(NO3)3·6H2O, 2.93 g) in 50 ml of deionized water at a Mg:La molar ratio of 5.6:1 and stir until completely dissolved.

[0033] (2) Slowly add anhydrous Na2CO3 (0.8 mol / L) dropwise to adjust the pH to 10, continue stirring and age for 12 h.

[0034] (3) The filter cake was collected by filtration, washed with deionized water until neutral, and heated at 100 o C for 12 h, and then at 600 o C in air atmosphere for 5 h (heating rate 5 o C / min), and a MgO-La2O3-5.6 composite oxide support was obtained.

[0035] Ru loading (incipient wetness impregnation method): (1) Take 0.1 g of 10% Ru solution and add it to 0.5 g of deionized water. Then add the above-mentioned MgO-La2O3-5.6 carrier (1.0 g) and impregnate with ultrasonic stirring for 20 min.

[0036] (2) at 100 o C for 12 h and then dried at 600 o C calcined in air atmosphere for 4 h (heating rate 5 o C / min), then at 550 o The samples were reduced in a CH2 / Ar (H2 volume ratio 50%) atmosphere for 1 h (heating rate 10 o C / min) to obtain 1wt%Ru / MgO-La2O3-5.6 catalyst. Example

[0037] Synthesis of MgO-La2O3-19 support using co-precipitation method: (1) Dissolve magnesium nitrate (Mg(NO3)2·6H2O, 10.98 g) and lanthanum nitrate (La(NO3)3·6H2O, 0.98 g) in 50 ml of deionized water at a Mg:La molar ratio of 19:1 and stir until completely dissolved.

[0038] (2) Slowly add anhydrous Na2CO3 (0.8 mol / L) dropwise to adjust the pH to 10, continue stirring and age for 12 h.

[0039] (3) The filter cake was collected by filtration, washed with deionized water until neutral, and heated at 100 o C for 12 h, and then at 600 o C in air atmosphere for 5 h (heating rate 5 o C / min), and MgO-La2O3-19 composite oxide support was obtained.

[0040] Ru loading (incipient wetness impregnation method): (1) Take 0.1 g of 10% Ru solution and add it to 0.5 g of deionized water. Then add the above-mentioned MgO-La2O3-19 carrier (1.0 g) and impregnate with ultrasonic stirring for 20 min.

[0041] (2) at 100 o C for 12 h and then dried at 600 o C in air atmosphere for 4 h (heating rate 5 o C / min), then at 550 o The samples were reduced in a CH2 / Ar (H2 volume ratio 50%) atmosphere for 1 h (heating rate 10 o C / min) to obtain 1wt%Ru / MgO-La2O3-19 catalyst. Example

[0042] Synthesis of MgO-La2O3-1 support using co-precipitation method: (1) Dissolve magnesium nitrate (Mg(NO3)2·6H2O, 5.78 g) and lanthanum nitrate (La(NO3)3·6H2O, 9.76 g) in 50 ml of deionized water at a Mg:La molar ratio of 1:1 and stir until completely dissolved.

[0043] (2) Slowly add anhydrous Na2CO3 (0.8 mol / L) dropwise to adjust the pH to 10, continue stirring and age for 12 h.

[0044] (3) The filter cake was collected by filtration, washed with deionized water until neutral, and heated at 100 o C for 12 h, and then at 600 o C in air atmosphere for 5 h (heating rate 5 oC / min), and obtain MgO-La2O3-1 composite oxide support.

[0045] Ru loading (incipient wetness impregnation method): (1) Take 0.1 g of 10% Ru solution and add it to 0.5 g of deionized water. Add the above-mentioned MgO-La2O3-1 carrier (1.0 g) and impregnate with ultrasonic stirring for 20 min.

[0046] (2) at 100 o C for 12 h and then dried at 600 o C in air atmosphere for 4 h (heating rate 5 o C / min), then at 550 o The reduction was carried out in a CH2 / Ar (H2 volume ratio 50%) atmosphere for 1 h (heating rate 10 o C / min) to obtain 1wt%Ru / MgO-La2O3-1 catalyst. Example

[0047] Synthesis of MgO-La2O3-0.17 support using co-precipitation method: (1) Dissolve magnesium nitrate (Mg(NO3)2·6H2O, 1.73 g) and lanthanum nitrate (La(NO3)3·6H2O, 16.59 g) in 50 ml of deionized water at a Mg:La molar ratio of 0.17:1 and stir until completely dissolved.

[0048] (2) Slowly add anhydrous Na2CO3 (0.8 mol / L) dropwise to adjust the pH to 10, continue stirring and age for 12 h.

[0049] (3) The filter cake was collected by filtration, washed with deionized water until neutral, and heated at 100 o C for 12 h, and then at 600 o C in air atmosphere for 5 h (heating rate 5 o C / min), and a MgO-La2O3-0.17 composite oxide support was obtained.

[0050] Ru loading (incipient wetness impregnation method): (1) Take 0.1 g of 10% Ru solution and add it to 0.5 g of deionized water. Then add the above-mentioned MgO-La2O3-0.17 carrier (1.0 g) and impregnate with ultrasonic stirring for 20 min.

[0051] (2) at 100 o C for 12 h and then dried at 600 o C calcined in air atmosphere for 4 h (heating rate 5 o C / min), then at 550 oThe reduction was carried out in a CH2 / Ar (H2 volume ratio 50%) atmosphere for 1 h (heating rate 10 o C / min) to obtain 1wt%Ru / MgO-La2O3-0.17 catalyst. Example

[0052] Synthesis of MgO support using co-precipitation method: (1) Dissolve magnesium nitrate (Mg(NO3)2·6H2O, 11.56 g) in 50 ml of deionized water and stir until completely dissolved.

[0053] (2) Slowly add anhydrous Na2CO3 (0.8 mol / L) dropwise to adjust the pH to 10, continue stirring and age for 12 h.

[0054] (3) The filter cake was collected by filtration, washed with deionized water until neutral, and heated at 100 o C for 12 h, and then at 600 o C in air atmosphere for 5 h (heating rate 5 o C / min), and MgO support was obtained.

[0055] Ru loading (incipient wetness impregnation method): (1) Take 0.1 g of 10% Ru solution and add it to 0.5 g of deionized water. Then add the above-mentioned MgO carrier (1.0 g) and impregnate with ultrasonic stirring for 20 min.

[0056] (2) at 100 o C for 12 h and then dried at 600 o C in air atmosphere for 4 h (heating rate 5 o C / min), then at 550 o The reduction was carried out in a CH2 / Ar (H2 volume ratio 50%) atmosphere for 1 h (heating rate 10 o C / min) to obtain a 1 wt% Ru / MgO catalyst. Example

[0057] Synthesis of La2O3 support using co-precipitation method: (1) Dissolve lanthanum nitrate (La(NO3)3·6H2O, 19.52 g) in 50 ml of deionized water and stir until completely dissolved.

[0058] (2) Slowly add anhydrous Na2CO3 (0.8 mol / L) dropwise to adjust the pH to 10, continue stirring and age for 12 h.

[0059] (3) The filter cake was collected by filtration, washed with deionized water until neutral, and heated at 100 o C for 12 h, and then at 600 oC in air atmosphere for 5 h (heating rate 5 o C / min), and obtain La2O3 support.

[0060] Ru loading (incipient wetness impregnation method): (1) Take 0.1 g of 10% Ru solution and add it to 0.5 g of deionized water. Then add the above-mentioned La2O3 carrier (1.0 g) and impregnate with ultrasonic stirring for 20 min.

[0061] (2) at 100 o C for 12 h and then dried at 600 o C in air atmosphere for 4 h (heating rate 5 o C / min), then at 550 o The samples were reduced in a CH2 / Ar (H2 volume ratio 50%) atmosphere for 1 h (heating rate 10 o C / min) to obtain 1wt%Ru / La2O3 catalyst. Example

[0062] (1) Dissolve magnesium nitrate (Mg(NO3)2·6H2O, 9.83 g) and lanthanum nitrate (La(NO3)3·6H2O, 2.93 g) in 50 ml of deionized water at a Mg:La molar ratio of 5.6:1 and stir until completely dissolved.

[0063] (2) Slowly add anhydrous Na2CO3 (0.8 mol / L) dropwise to adjust the pH to 10, continue stirring and age for 12 h.

[0064] (3) The filter cake was collected by filtration, washed with deionized water until neutral, and heated at 100 o C for 12 h, and then at 400 o C in air atmosphere for 5 h (heating rate 5 o C / min), and obtain MgO-La2O3-5.6 composite oxide support.

[0065] Ru loading (incipient wetness impregnation method): (1) Take 0.1 g of 10% Ru solution and add it to 0.5 g of deionized water. Then add the above-mentioned MgO-La2O3-5.6 carrier (1.0 g) and impregnate with ultrasonic stirring for 20 min.

[0066] (2) at 100 o C for 12 h and then dried at 600 o C in air atmosphere for 4 h (heating rate 5 o C / min), then at 550 o The reduction was carried out in a CH2 / Ar (H2 volume ratio 50%) atmosphere for 1 h (heating rate 10o C / min) to obtain 1wt%Ru / MgO-La2O3-5.6 catalyst. Example

[0067] (1) Dissolve magnesium nitrate (Mg(NO3)2·6H2O, 9.83 g) and lanthanum nitrate (La(NO3)3·6H2O, 2.93 g) in 50 ml of deionized water at a Mg:La molar ratio of 5.6:1 and stir until completely dissolved.

[0068] (2) Slowly add anhydrous Na2CO3 (0.8 mol / L) dropwise to adjust the pH to 10, continue stirring and age for 12 h.

[0069] (3) The filter cake was collected by filtration, washed with deionized water until neutral, and heated at 100 o C for 12 h, and then at 500 o C in air atmosphere for 5 h (heating rate 5 o C / min), and obtain MgO-La2O3-5.6 composite oxide support.

[0070] Ru loading (incipient wetness impregnation method): (1) Take 0.1 g of 10% Ru solution and add it to 0.5 g of deionized water. Then add the above-mentioned MgO-La2O3-5.6 carrier (1.0 g) and impregnate with ultrasonic stirring for 20 min.

[0071] (2) at 100 o C for 12 h and then dried at 600 o C in air atmosphere for 4 h (heating rate 5 o C / min), then at 550 o The reduction was carried out in a CH2 / Ar (H2 volume ratio 50%) atmosphere for 1 h (heating rate 10 o C / min) to obtain 1wt%Ru / MgO-La2O3-5.6 catalyst. Example

[0072] (1) Dissolve magnesium nitrate (La(NO3)3·6H2O, 9.83 g) and lanthanum nitrate (La(NO3)3·6H2O, 2.93 g) in 50 ml of deionized water at a Mg:La molar ratio of 5.6:1 and stir until completely dissolved.

[0073] (2) Slowly add anhydrous Na2CO3 (0.8 mol / L) dropwise to adjust the pH to 10, continue stirring and age for 12 h.

[0074] (3) The filter cake was collected by filtration, washed with deionized water until neutral, and heated at 100 oC for 12 h, and then at 700 o C in air atmosphere for 5 h (heating rate 5 o C / min), and obtain MgO-La2O3-5.6 composite oxide support.

[0075] Ru loading (incipient wetness impregnation method): (1) Take 0.1 g of 10% Ru solution and add it to 0.5 g of deionized water. Then add the above-mentioned MgO-La2O3-5.6 carrier (1.0 g) and impregnate with ultrasonic stirring for 20 min.

[0076] (2) at 100 o C for 12 h and then dried at 600 o C in air atmosphere for 4 h (heating rate 5 o C / min), then at 550 o The reduction was carried out in a CH2 / Ar (H2 volume ratio 50%) atmosphere for 1 h (heating rate 10 o C / min) to obtain 1wt%Ru / MgO-La2O3-5.6 catalyst. Example

[0077] (1) Dissolve magnesium nitrate (Mg(NO3)2·6H2O, 9.83 g) and lanthanum nitrate (La(NO3)3·6H2O, 2.93 g) in 50 ml of deionized water at a Mg:La molar ratio of 5.6:1 and stir until completely dissolved.

[0078] (2) Slowly add anhydrous Na2CO3 (0.8 mol / L) dropwise to adjust the pH to 10, continue stirring and age for 12 h.

[0079] (3) The filter cake was collected by filtration, washed with deionized water until neutral, and heated at 100 o C for 12 h, and then at 800 o C in air atmosphere for 5 h (heating rate 5 o C / min), and a MgO-La2O3-5.6 composite oxide support was obtained.

[0080] Ru loading (incipient wetness impregnation method): (1) Take 0.1 g of 10% Ru solution and add it to 0.5 g of deionized water. Then add the above-mentioned MgO-La2O3-5.6 carrier (1.0 g) and impregnate with ultrasonic stirring for 20 min.

[0081] (2) at 100 o C for 12 h and then dried at 600 o C in air atmosphere for 4 h (heating rate 5 oC / min), then at 550 o The reduction was carried out in a CH2 / Ar (H2 volume ratio 50%) atmosphere for 1 h (heating rate 10 o C / min) to obtain 1wt%Ru / MgO-La2O3-5.6 catalyst.

[0082] Comparative Example 1 Synthesis of MgO support using co-precipitation method: (1) Dissolve magnesium nitrate (Mg(NO3)2·6H2O, 11.56 g) in 50 ml of deionized water and stir until completely dissolved.

[0083] (2) Slowly add anhydrous Na2CO3 (0.8 mol / L) dropwise to adjust the pH to 10, continue stirring and age for 12 h.

[0084] (3) The filter cake was collected by filtration, washed with deionized water until neutral, and heated at 100 o C for 12 h, and then at 600 o C in air atmosphere for 5 h (heating rate 5 o C / min), and MgO support was obtained.

[0085] Comparative Example 2 Synthesis of La2O3 support using co-precipitation method: (1) Dissolve lanthanum nitrate (La(NO3)3·6H2O, 19.52 g) in 50 ml of deionized water and stir until completely dissolved.

[0086] (2) Slowly add anhydrous Na2CO3 (0.8 mol / L) dropwise to adjust the pH to 10, continue stirring and age for 12 h.

[0087] (3) The filter cake was collected by filtration, washed with deionized water until neutral, and heated at 100 o C for 12 h, and then at 600 o C in air atmosphere for 5 h (heating rate 5 o C / min), and La2O3 carrier was obtained.

[0088] Example 7 Catalyst Activity Evaluation Weigh 0.05 g of catalyst and place it in a straight quartz tube at 550 o C, H2 / Ar=1:1 (total flow rate: 40 ml / min) for 60 min, then turn off H2 and cool to 350 o C, purged for 10 min and then started to react. o C is the step length and the temperature is gradually increased, the highest temperature is 550 oC. Pure ammonia without dilution was introduced throughout the reaction at a space velocity of 6000 ml / g / h. Activity data are shown in Table 1.

[0089] Example 8 Catalyst Activity Evaluation Weigh 0.05 g of catalyst and place it in a straight quartz tube at 550 o C, H2 / Ar=1:1 (total flow rate: 40 ml / min) for 60 min, then turn off H2 and cool to 350 o C, purged for 10 min and then started to react. o C is the step length and the temperature is gradually increased, the highest temperature is 550 o C. Pure ammonia without dilution was introduced throughout the reaction at a space velocity of 6000 ml / g / h. Activity data are shown in Table 2.

[0090] Example 9 Catalyst Activity Evaluation Weigh 0.05 g of catalyst and place it in a straight quartz tube at 550 o C, H2 / Ar=1:1 (total flow rate: 40 ml / min) for 60 min, then turn off H2 and cool to 350 o C, purged for 10 min and then started to react. o C is the step length and the temperature is gradually increased, the highest temperature is 550 o C. Pure ammonia was introduced without dilution throughout the reaction at space velocities of 6000 ml / g / h, 18000 ml / g / h, and 30000 ml / g / h, respectively. Activity data are shown in Table 3.

[0091] Table 1

[0092] The results in Table 1 show that the Ru / MgO-La2O3 catalyst prepared in Example 1 exhibits good activity at different temperatures and o C, the conversion rate has reached 99.5%, and the presence of NH3 is almost undetectable on the chromatogram. By comparing the activity, the Ru / MgO-La2O3 prepared by the present invention has achieved a high conversion rate in the ammonia decomposition hydrogen production reaction. No obvious Ru characteristic peaks appear in the XRD spectrum of the catalyst of Example 1, indicating that the Ru nanoparticles are highly dispersed. Figure 5 TEM analysis showed that Ru nanoparticles were evenly dispersed on the surface of the carrier with an average particle size of 2.5 nm, which effectively improved the catalytic activity.

[0093] Figure 2The H2-TPR spectra of Example 1, Comparative Example 5 and Comparative Example 6 of the present invention are shown in Figure 2. The analysis results show that the reduction temperature characteristics clearly reflect the difference in the strength of the metal-support interaction. The reduction peak of Ru species in Comparative Example 5 is mainly at 144 o C and 207 o C, while the reduction peak of Comparative Example 6 is at 192 o C appears. In contrast, the catalyst of Example 1 o There is no obvious reduction peak near C, but at a higher temperature of 277 o C shows a reduction peak of RuOx species that strongly interacts with the support. This reduction characteristic indicates that the MgO-La2O3 composite support prepared by the co-precipitation method forms a stable anchoring effect with Ru, and the difference in reduction temperature also confirms that it is difficult to construct a strong metal-support interaction with a single support system. Combined with TEM characterization, it can be seen that the preparation of composite oxides as support components by co-precipitation not only optimizes the dispersion of Ru species, but also significantly enhances the interaction between the metal and the support of the catalyst through mutual synergy, which is consistent with its low-temperature activity (450 o C conversion rate ≥99%), highlighting the significant advantages of composite carrier design over traditional single carrier system.

[0094] Figure 3 The NH3-TPD test results reveal the difference in substrate adsorption capacity between Example 1 and Comparative Examples 5 and 6. The results show that although Comparative Example 5 has the highest NH3 adsorption, it is mainly weak adsorption. In contrast, Example 1 has a low adsorption capacity at 200-300 o The desorption peak intensity in the C range is significant, indicating that its adsorption capacity for NH3 is better than that of Comparative Example 5, and it exhibits stronger NH3 adsorption capacity in the high temperature region, which is also consistent with the catalytic activity. Figure 4 The H2-TPD analysis further showed that the desorption temperature in Example 1 was the highest, but the temperature for complete desorption was also at 400 o Before C, this would not happen at 450 o C decomposes and decomposes ammonia to produce an effect.

[0095] Table 2 examines the effects of different calcination temperatures on the reaction activity for Examples 5-8. The results are as follows: Table 2

[0096] Table 2 investigates the effects of different calcination temperatures on catalyst performance. The results show that the calcination temperature has a great influence on the activity of ammonia decomposition to hydrogen. o The activity of the catalyst calcined with C is much lower than 500 oC calcined catalyst. Meanwhile, the pure support has no activity for the reaction.

[0097] Table 3 investigates the effects of different reaction space velocities on the Ru / MgO-La2O3 catalyst in the ammonia decomposition hydrogen production reaction for Example 1. The space velocities are 6000 ml / g / h, 18000 ml / g / h, and 30000 ml / g / h, respectively. The specific results are as follows: Table 3

[0098] The results in Table 3 show that the ammonia decomposition hydrogen production reaction is greatly affected by the space velocity. The higher the space velocity, the lower the conversion rate. However, the Ru / MgO-La2O3 catalyst prepared in Example 1 has a high conversion rate at a space velocity of 30000 ml / g / h and a conversion rate of 500 o The Ru / MgO-La2O3 catalyst prepared in the embodiment of the present invention has a good industrial application prospect due to its excellent conversion rate.

[0099] The above description is merely a preferred embodiment of the present invention, and the embodiments of the present invention are not limited to the described embodiments. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. Preparation of a Ru / MgO-La2O3 catalyst and its application in ammonia decomposition hydrogen production reaction, characterized by: The active component of the catalyst is metallic Ru, and the carrier is a MgO-La2O3 composite oxide. In terms of mass percentage, the metallic Ru loading is 0.1-20 wt%, and the molar ratio of MgO to La2O3 in the carrier is 0.1:1-20:

1. The Ru nanoparticles in the catalyst have a particle size of 1.5-5.0 nm and are uniformly dispersed on the surface of the MgO-La2O3 carrier. MgO and La2O3 in the carrier form a strong interaction through coprecipitation, significantly improving the dispersibility and anti-sintering performance of Ru.

2. The catalyst according to claim 1, wherein the preparation method thereof is characterized in that the MgO-La2O3 composite carrier is prepared by a coprecipitation method, and the Ru active component is loaded by an incipient wetness impregnation method.

3. The method for preparing the catalyst according to claim 2, comprising the steps of: (1) A magnesium source and a lanthanum source are dissolved in deionized water to form a mixed solution, a precipitant is added to adjust the pH to 8-14, and the solution is stirred, aged, washed, dried, and calcined to obtain a MgO-La2O3 composite support; (2) An equal volume of Ru precursor solution is impregnated on the support obtained in step (1), and a Ru / MgO-La2O3 catalyst is obtained after drying, calcining and reducing.

4. The method for preparing the catalyst according to claim 3, wherein The magnesium source in step (1) is magnesium chloride, magnesium sulfate, magnesium acetate, or magnesium nitrate, preferably magnesium nitrate; the lanthanum source is lanthanum nitrate, lanthanum oxide, lanthanum fluoride, lanthanum carbonate, lanthanum chloride, or lanthanum acetate, preferably lanthanum nitrate; the precipitant is ammonia water, potassium hydroxide, hydrogen sulfide, sodium carbonate, ammonium carbonate, or sodium hydroxide, preferably sodium carbonate, preferably sodium carbonate. The Ru precursor in step (2) is RuCl3, Ru(NO3)3, K2RuO4, or ruthenium acetylacetonate, preferably RuCl3.

5. The method for preparing a ruthenium-based catalyst according to claim 3, wherein: By adjusting the Ru loading amount to 0.1wt%~20wt%.

6. The method for preparing a ruthenium-based catalyst according to claim 3, wherein: The molar ratio of the magnesium source to the lanthanum source in step (1) is regulated to 0.1:1~20:1 by coprecipitation ratio, preferably 1:0.2; the Ru loading in step (2) is controlled to 0.1wt%~20wt% by precursor solution concentration, preferably 1wt%.

7. The method for preparing a ruthenium-based catalyst according to claim 3, wherein: The pH range of the precipitation in step (1) is 8-14, preferably 8-10; the aging time in step (1) is 1-24 h, preferably 2-12 h; the drying temperature in step (1) is 80-120 o C, preferably 100 o C; drying time is 12~24 h, preferably 12 h; calcination temperature in step (1) is 300~1000 o C, preferably 400~800 o C; the calcination time in step (1) is 2 to 10 h, preferably 6 h; the heating rate during the calcination process in step (1) is 2 to 20 o C / min, preferably 10 o C / min after calcination to obtain a powdery support.

8. The method for preparing a ruthenium-based catalyst according to claim 3, wherein: The Ru loading in step (2) is controlled by the concentration of the precursor solution to be 0.1 wt% to 20 wt%, preferably 0.1 wt% to 10 wt%; the drying temperature in step (2) is 80 to 120 o C, preferably 100 o C; drying time is 12~24 h, preferably 12 h; calcination temperature in step (2) is 300~1000 o C, preferably 400~800 o C; the calcination time in step (2) is 2 to 10 h, preferably 6 h; the heating rate during the calcination process in step (2) is 2 to 20 o C / min, preferably 10 o C / min after calcination to obtain a powdery catalyst precursor.

9. The method for preparing a ruthenium-based catalyst according to claim 3, wherein: The reducing gas in step (2) is a mixture of hydrogen and argon, and the reducing temperature is 400~1000 o C, preferably 550 o C; the reduction time is 1~6 h, preferably 1 h, and the heating rate is 5-10 o C / min.

10. Use of the catalyst according to claim 1 in ammonia decomposition to produce hydrogen, characterized in that The reaction temperature is 300~1000 o C, preferably 600~700 o C; space velocity range 1200-600000 ml / g / h, preferably 6000-30000 ml / g / h.

11. The use according to claim 10, characterized in that Ammonia conversion rate ≥99%.

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