A Ru / CeO2-SiO2 catalyst for hydrogen production from ammonia decomposition and its preparation method

Abstract

The application discloses a Ru / CeO2-SiO2 catalyst for hydrogen production by ammonia decomposition and a preparation method thereof, and belongs to the technical field of catalyst preparation. The catalyst comprises an active component Ru and a carrier CeO2 / SiO2. The CeO2 nanoparticles are uniformly dispersed on the surface of SiO2 by using an electrostatic adsorption method, and the active component Ru nanoparticles are selectively loaded on the surface of CeO2. The CeO2 has a unique Ce 3+ -Ce 4+ The variable valence capacity can form rich oxygen vacancies. The generation of the oxygen vacancies is favorable to enhancing the interaction intensity between Ru and CeO2, improving the electronic structure of the Ru surface, activating reactants, optimizing reaction kinetics, and promoting the ammonia decomposition reaction. In addition, the Ru particles are only distributed on the surface of CeO2, and even if the CeO2 moves on the surface of SiO2 at high temperature, the active component Ru will not be agglomerated, so that the Ru / CeO2-SiO2 catalyst exhibits excellent ammonia decomposition reaction catalytic performance and good stability.

Description

Technical Field

[0001] This invention belongs to the field of ammonia decomposition technology, specifically relating to a Ru / CeO2-SiO2 catalyst for hydrogen production from ammonia decomposition and its preparation method. Background Technology

[0002] Hydrogen energy is an ideal clean energy source due to its high energy conversion efficiency, wide availability, and environmental friendliness. However, hydrogen has an extremely low bulk density, making it prone to leakage, combustion, and explosion, and it suffers from hydrogen embrittlement. These factors limit the storage, transportation, and large-scale application of hydrogen. To solve these storage and transportation challenges, researchers have conducted in-depth research on hydrogen storage systems and developed various in-situ hydrogen production technologies, mainly including water electrolysis, reforming, and ammonia decomposition. Although water electrolysis produces no pollution, it faces problems of high energy consumption and high cost; reforming alcohol fuels such as methanol and ethanol produces CO2. x Byproducts such as ammonia decomposition can contaminate fuel cells and reduce their lifespan. In contrast, hydrogen production from ammonia decomposition... Ammonia produces only two harmless byproducts, hydrogen and nitrogen, with no other pollutant emissions. Therefore, using ammonia as a hydrogen storage medium is more environmentally friendly, safer, and more economical. Overall, ammonia hydrogen storage technology can effectively solve the hydrogen storage and transportation problems in hydrogen-powered vehicles and is currently a research hotspot in the field of hydrogen energy.

[0003] Currently, the active centers in ammonia decomposition hydrogen production catalysts are mainly iron, cobalt, nickel, ruthenium, and metal nitrides, with common supports including magnesium oxide, silicon oxide, alumina, zirconium oxide, activated carbon, and carbon nanotubes. Catalysts using the noble metal ruthenium as the active center exhibit high catalytic activity, while non-noble metal catalysts show relatively poor activity. CN1456491A discloses a ruthenium-supported ammonia decomposition hydrogen production catalyst on carbon nanotubes, which exhibits good catalytic activity in the 450-550℃ range; however, this catalyst has a high loading (up to 4.9%), which increases the catalyst cost; while the catalyst with a lower loading (1.5% Ru) only achieves a conversion rate of 75.5% at 550℃, indicating low ammonia decomposition efficiency. CN115920942A discloses a magnesium oxide-coated ruthenium-based catalyst, using MOF-74-coated ZIF-8 or ZIF-67 as a support, and one or more of barium, lanthanum, and cesium as modifying agents; the ruthenium content accounts for 0.2-2% of the catalyst mass, and the content of the modifying components accounts for 5-20% of the catalyst mass; although the preparation method of this catalyst is relatively simple (impregnation method), its ammonia decomposition activity is still poor even at low space velocities (6000 mL·g). -1 h -1 (Conversion rate 31.05% at 500℃). Summary of the Invention

[0004] To address the problems of high Ru loading, insufficient low-temperature activity, and low ammonia treatment efficiency in existing ammonia decomposition hydrogen production catalysts, the present invention aims to provide a highly efficient ammonia decomposition catalyst with low Ru loading and its preparation method. Using CeO2 / SiO2 as a composite support, Ru is directionally adsorbed onto the CeO2 surface to improve the ammonia decomposition catalytic efficiency and catalyst stability of the Ru-based catalyst, thereby developing a low-temperature, highly efficient, and stable ammonia decomposition catalyst.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A ruthenium-based catalyst, characterized in that it comprises an active component and a support, wherein the active component is ruthenium and the support is CeO2 / SiO2; wherein the active component Ru accounts for 0.5-1.5 wt.% of the catalyst and the CeO2 accounts for 12-35 wt.%.

[0007] The preparation method of the Ru-based catalyst includes the following steps:

[0008] (1) Disperse the silicon precursor in an alcohol-water solvent, add the precipitant solution and surfactant CTAB while stirring, and continue stirring for 4-12 hours;

[0009] (2) After centrifuging and drying the precipitate obtained in step (1), high specific surface area spherical SiO2 is obtained by calcining in air atmosphere;

[0010] (3) CeO2 was loaded by electrostatic adsorption. The SiO2 obtained in step (2) was ultrasonically dispersed in cerium nitrate solution. Then NaOH solution was added to the solution. After reacting for 5 to 10 minutes, the precipitate obtained by the reaction was filtered, dried and calcined in air atmosphere to obtain the composite carrier CeO2 / SiO2.

[0011] (4) The composite carrier CeO2 / SiO2 obtained in step (3) is ultrasonically dispersed in a beaker to obtain suspension A. The ruthenium precursor is dissolved in a beaker to obtain solution B. HCl solution is added to suspension A and solution B respectively to adjust their pH to 3-4.

[0012] (5) The solution B in step (4) is slowly added to the suspension A by a pump, and the reaction is carried out for 1-12 hours. After filtration and drying, the precipitated sample is obtained and calcined under a certain atmosphere to obtain the ruthenium-based catalyst.

[0013] Further, the volume ratio of silicon precursor to precipitant used in step (1) is 5 to 25:1; the mass ratio of silicon precursor to activator CTAB is 5 to 9:1.

[0014] Further, the silicon precursor mentioned in step (1) is at least one of silica sol, tetramethoxysilane, sodium metasilicate, and tetraethyl orthosilicate;

[0015] Further, the precipitant mentioned in step (1) is at least one of ammonia, ammonium carbonate, potassium carbonate, sodium hydroxide, and potassium hydroxide.

[0016] Further, in step (1), the volume ratio of alcohol to water in the alcohol-water solvent is 1:5, and the alcohol is at least one of pentanol, ethanol, and ethylene glycol.

[0017] Furthermore, the roasting temperature in step (2) is 500-900℃ and the time is 1-6h.

[0018] Furthermore, the concentration of the NaOH solution in step (3) is 2-4 mol / L.

[0019] Furthermore, the roasting temperature in step (3) is 350-750℃ and the time is 9-15h.

[0020] Further, the Ru precursor in step (4) is at least one of potassium hexachlororuthenate, potassium pentachlororuthenate hydrate, and ammonium pentachlororuthenate hydrate.

[0021] Further, the concentration of the HCl solution in step (4) is 1 to 5 mol / L.

[0022] Further, the calcination in step (5) is carried out in a 50 vol.% H2 / Ar mixed gas at 300-600°C for 2-6 hours.

[0023] The ruthenium-based catalyst prepared above can be used for hydrogen production from ammonia decomposition.

[0024] The beneficial effects of this invention are as follows:

[0025] This invention provides a Ru-based ammonia decomposition catalyst, the support CeO2 / SiO2 of which is prepared by electrostatic adsorption. Under alkaline conditions, SiO2 has a negative potential. By controlling the concentration of OH- in the solution and the adsorption time, [Ce(OH)2] can be decomposed. x ] y+ The substance is adsorbed onto the surface of SiO2, and then calcined to form uniformly dispersed isolated CeO2 nanoparticles. The CeO2 prepared using this method is not only small in size but also highly uniformly dispersed on the SiO2 surface; furthermore, CeO2 possesses unique Ce... 3+ -Ce 4+ The variable valence capability can provide a large number of oxygen vacancies. These oxygen vacancies can promote the forward reaction of ammonia decomposition in a variety of ways, such as providing active sites, improving electron and matter migration, promoting the activation of reactants, and optimizing reaction kinetics, thus exhibiting good activity.

[0026] The surface of CeO2 (zero charge point approximately 8.1) material carries a positive charge under acidic conditions of pH 3-5. Using strong electrostatic adsorption, Ru can be selectively and directionally adsorbed onto the CeO2 surface, rather than onto SiO2 (which carries a negative charge). The Ru / CeO2-SiO2 catalyst prepared using this method exhibits uniform Ru particle size and dispersion, which is beneficial for promoting the ammonia decomposition reaction. Because the Ru particles are distributed on the CeO2 surface, even at high temperatures, when CeO2 moves on the SiO2 surface, the active component Ru does not agglomerate due to the barrier effect of CeO2, resulting in excellent catalyst stability. Specifically, the catalyst prepared in this invention, with a Ru loading of 1 wt.%, can achieve near-equilibrium conversion of ammonia at 550℃, making it a low-loading, low-cost, highly efficient, and stable ammonia decomposition catalyst. Attached Figure Description

[0027] Figure 1 This is a transmission electron microscope (TEM) image of the catalyst sample obtained in Example 1.

[0028] Figure 2 The Arrhenius curves are for the ammonia decomposition reaction of the catalysts obtained in Example 1 and Comparative Examples 1 and 2.

[0029] Figure 3 The results are the stability test results of the catalyst sample obtained in Example 1. Detailed Implementation

[0030] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto.

[0031] Example 1

[0032] Measure 20 mL of deionized water, 5 mL of ethanol, and 0.35 g of CTAB and add them to a beaker. After stirring, add 0.1 mL of NH3·H2O solution (25-28 wt.%) and 0.5 mL of pentanol and stir until well mixed. Then add 2.2 mL of LTEOS and stir for 6 h. After multiple filtrations and washings, transfer the sample to an 80 °C oven and dry for 10 h. Place the dried sample in a muffle furnace and calcine at 600 °C for 2 h to obtain SiO2.

[0033] 0.36 g of SiO2 powder was weighed and dispersed in 300 mL of deionized water. Then, 0.521 g of cerium nitrate hexahydrate was added and stirred to dissolve. 2.4 mL of NaOH (2 mol / L) was added dropwise to the solution. After reacting for 3 min, the sample was filtered and washed several times and then dried in an oven at 80 °C for 10 h. The dried sample was then calcined in a muffle furnace at 600 °C for 12 h to obtain a CeO2 / SiO2 support with a CeO2 mass fraction of 29 wt.%.

[0034] 0.0562 g of potassium pentachlororuthenate hydrate was dissolved in 50 mL of deionized water and placed in a beaker to obtain solution A. 0.3 g of CeO2 / SiO2 support was dispersed in 70 mL of deionized water and placed in a beaker to obtain suspension B. HCl solution was then added to solution A and suspension B to adjust the pH of both solutions A and suspension B to 3-4. After 5 h, solution A was slowly added to suspension B via a pump, and the mixture was stirred for another 5 h. After filtration and washing, the mixture was dried in an 80 °C oven for 10 h. After drying, the sample was placed in a tube furnace at 500 °C and calcined for 3 h under a 50 vol.% H2 / Ar atmosphere to obtain a Ru / CeO2 / SiO2 catalyst sample with a CeO2 mass fraction of 29 wt.% and a Ru loading of 1 wt.%.

[0035] Figure 1 The image shows a transmission electron microscope (TEM) image of the catalyst sample obtained in Example 1. As can be seen from the image, the catalyst is porous and spherical, with CeO2 nanoparticles uniformly dispersed on the SiO2 surface; Ru is distributed on the CeO2 surface, and no obvious large-sized Ru particles were observed.

[0036] Figure 2 The figures show the Arrhenius curves for the ammonia decomposition reaction of the catalysts obtained in Example 1 and Comparative Examples 1 and 2. It is clearly shown in the figures that the apparent activation energy of Example 1 is much lower than that of Comparative Examples 1 and 2, indicating that the ammonia decomposition reaction proceeds more readily in the forward direction.

[0037] Figure 3 The figure shows the stability test results of the catalyst sample obtained in Example 1. As can be seen from the figure, the catalyst obtained in Example 1 showed no significant decrease in activity after 150 hours of activity testing, demonstrating very good stability.

[0038] Example 2

[0039] Measure 20 mL of deionized water, 5 mL of ethanol, and 0.35 g of CTAB and add them to a beaker. After stirring, add 0.1 mL of NH3·H2O solution (25-28 wt.%) and 0.5 mL of pentanol and stir until well mixed. Then add 2.2 mL of LTEOS and stir for 6 h. After multiple filtrations and washings, transfer the sample to an 80 °C oven and dry for 10 h. Place the dried sample in a muffle furnace and calcine at 600 °C for 2 h to obtain SiO2.

[0040] 1.08 g of SiO2 powder was weighed and dispersed in 300 mL of deionized water. Then, 0.521 g of cerium nitrate hexahydrate was added and stirred to dissolve. 2.4 mL of NaOH (2 mol / L) was added dropwise to the solution. After reacting for 3 min, the sample was filtered and washed several times and then dried in an oven at 80 °C for 10 h. The dried sample was then calcined in a muffle furnace at 600 °C for 12 h to obtain a CeO2 / SiO2 support with a CeO2 mass fraction of 12 wt.%.

[0041] 0.0562 g of potassium pentachlororuthenate hydrate was dissolved in 50 mL of deionized water and placed in a beaker to obtain solution A. 0.3 g of CeO2 / SiO2 support was dispersed in 70 mL of deionized water and placed in a beaker to obtain suspension B. HCl solution was then added to solution A and suspension B to adjust the pH of both solutions A and suspension B to 3-4. After 5 h, solution A was slowly added to suspension B via a pump, and the mixture was stirred for another 5 h. After filtration and washing, the mixture was dried in an 80 °C oven for 10 h. After drying, the sample was placed in a tube furnace at 500 °C and calcined for 3 h under a 50 vol.% H2 / Ar atmosphere to obtain a Ru / CeO2 / SiO2 catalyst sample with a CeO2 mass fraction of 12 wt.% and a Ru loading of 1 wt.%.

[0042] Example 3

[0043] Measure 20 mL of deionized water, 5 mL of ethanol, and 0.35 g of CTAB and add them to a beaker. After stirring, add 0.1 mL of NH3·H2O solution (25-28 wt.%) and 0.5 mL of pentanol and stir until well mixed. Then add 2.2 mL of LTEOS and stir for 6 h. After multiple filtrations and washings, transfer the sample to an 80 °C oven and dry for 10 h. Place the dried sample in a muffle furnace and calcine at 600 °C for 2 h to obtain SiO2.

[0044] 0.36 g of SiO2 powder was weighed and dispersed in 400 mL of deionized water. Then, 0.695 g of cerium nitrate hexahydrate was added and stirred to dissolve. 3.2 mL of NaOH (2 mol / L) was added dropwise to the solution. After reacting for 3 min, the sample was filtered and washed several times and then dried in an oven at 80 °C for 10 h. The dried sample was then calcined in a muffle furnace at 600 °C for 12 h to obtain a CeO2 / SiO2 support with a CeO2 mass fraction of 35 wt.%.

[0045] 0.0562 g of potassium pentachlororuthenate hydrate was dissolved in 50 mL of deionized water and placed in a beaker to obtain solution A. 0.3 g of CeO2 / SiO2 support was dispersed in 70 mL of deionized water and placed in a beaker to obtain suspension B. HCl solution was then added to solution A and suspension B to adjust the pH of both solutions A and suspension B to 3-4. After 5 h, solution A was slowly added to suspension B via a pump, and the mixture was stirred for another 5 h. After filtration and washing, the mixture was dried in an 80 °C oven for 10 h. After drying, the sample was placed in a tube furnace at 500 °C and calcined for 3 h under a 50 vol.% H2 / Ar atmosphere to obtain a Ru / CeO2 / SiO2 catalyst with a CeO2 mass fraction of 35 wt.% and a Ru loading of 1 wt.%.

[0046] Example 4

[0047] Measure 20 mL of deionized water, 5 mL of ethanol, and 0.35 g of CTAB and add them to a beaker. After stirring, add 0.1 mL of NH3·H2O solution (25-28 wt.%) and 0.5 mL of pentanol and stir until well mixed. Then add 2.2 mL of LTEOS and stir for 6 h. After multiple filtrations and washings, transfer the sample to an 80 °C oven and dry for 10 h. Place the dried sample in a muffle furnace and calcine at 600 °C for 2 h to obtain SiO2.

[0048] 1.009 g of cerium nitrate hexahydrate was weighed and dissolved in 8 mL of deionized water. 1 g of SiO2 was added for impregnation with an equal volume. The product was dried at 80 °C for 8 h. The dried sample was then placed in a muffle furnace at 600 °C and calcined in air for 4 h to obtain a CeO2 / SiO2 support with a CeO2 mass fraction of 29 wt.%.

[0049] 0.0562 g of potassium pentachlororuthenate hydrate was dissolved in 50 mL of deionized water and placed in a beaker to obtain solution A. 0.3 g of CeO2 / SiO2 support was dispersed in 70 mL of deionized water and placed in a beaker to obtain suspension B. HCl solution was then added to solution A and suspension B to adjust the pH of both solutions A and suspension B to 3-4. After 5 h, solution A was slowly added to suspension B via a pump, and the mixture was stirred for another 5 h. After filtration and washing, the mixture was dried in an 80 °C oven for 10 h. After drying, the sample was placed in a tube furnace at 500 °C and calcined for 3 h under a 50 vol.% H2 / Ar atmosphere to obtain a Ru / CeO2 / SiO2 catalyst with a CeO2 mass fraction of 29 wt.% and a Ru loading of 1 wt.%.

[0050] Example 5

[0051] Measure 20 mL of deionized water, 5 mL of ethanol, and 0.35 g of CTAB and add them to a beaker. After stirring, add 0.1 mL of NH3·H2O solution (25-28 wt.%) and 0.5 mL of pentanol and stir until well mixed. Then add 2.2 mL of LTEOS and stir for 6 h. After multiple filtrations and washings, transfer the sample to an 80 °C oven and dry for 10 h. Place the dried sample in a muffle furnace and calcine at 600 °C for 2 h to obtain SiO2.

[0052] 0.36 g of SiO2 powder was weighed and dispersed in 300 mL of deionized water. Then, 0.521 g of cerium nitrate hexahydrate was added and stirred to dissolve. 2.4 mL of NaOH (2 mol / L) was added dropwise to the solution. After reacting for 3 min, the sample was filtered and washed several times and then dried in an oven at 80 °C for 10 h. The dried sample was then calcined in a muffle furnace at 600 °C for 12 h to obtain a CeO2 / SiO2 support with a CeO2 mass fraction of 29 wt.%.

[0053] 0.0281 g of potassium pentachlororuthenate hydrate was dissolved in 50 mL of deionized water and placed in a beaker to obtain solution A. 0.3 g of CeO2 / SiO2 support was dispersed in 70 mL of deionized water and placed in a beaker to obtain suspension B. HCl solution was then added to solution A and suspension B to adjust the pH of both solutions A and suspension B to 3-4. After 5 h, solution A was slowly added to suspension B via a pump, and the mixture was stirred for another 5 h. After filtration and washing, the mixture was dried in an 80 °C oven for 10 h. After drying, the sample was placed in a tube furnace at 500 °C and calcined for 3 h under a 50 vol.% H2 / Ar atmosphere to obtain a Ru / CeO2 / SiO2 catalyst with a CeO2 mass fraction of 29 wt.% and a Ru loading of 0.5 wt.%.

[0054] Example 6

[0055] Measure 20 mL of deionized water, 5 mL of ethanol, and 0.35 g of CTAB and add them to a beaker. After stirring, add 0.1 mL of NH3·H2O solution (25-28 wt.%) and 0.5 mL of pentanol and stir until well mixed. Then add 2.2 mL of LTEOS and stir for 6 h. After multiple filtrations and washings, transfer the sample to an 80 °C oven and dry for 10 h. Place the dried sample in a muffle furnace and calcine at 600 °C for 2 h to obtain SiO2.

[0056] 0.36 g of SiO2 powder was weighed and dispersed in 300 mL of deionized water. Then, 0.521 g of cerium nitrate hexahydrate was added and stirred to dissolve. 2.4 mL of NaOH (2 mol / L) was added dropwise to the solution. After reacting for 3 min, the sample was filtered and washed several times and then dried in an oven at 80 °C for 10 h. The dried sample was then calcined in a muffle furnace at 600 °C for 12 h to obtain a CeO2 / SiO2 support with a CeO2 mass fraction of 29 wt.%.

[0057] 0.0843 g of potassium pentachlororuthenate hydrate was dissolved in 50 mL of deionized water and placed in a beaker to obtain solution A. 0.3 g of CeO2 / SiO2 support was dispersed in 70 mL of deionized water and placed in a beaker to obtain suspension B. HCl solution was then added to solution A and suspension B to adjust the pH of both solutions A and suspension B to 3-4. After 5 h, solution A was slowly added to suspension B via a pump, and the mixture was stirred for another 5 h. After filtration and washing, the mixture was dried in an 80 °C oven for 10 h. After drying, the sample was placed in a tube furnace at 500 °C and calcined for 3 h under a 50 vol.% H2 / Ar atmosphere to obtain a Ru / CeO2 / SiO2 catalyst with a CeO2 mass fraction of 29 wt.% and a Ru loading of 1.5 wt.%.

[0058] Comparative Example 1

[0059] Measure 10 mL of deionized water, 70 mL of ethanol, and 3 mL of NH3·H2O solution (25-28 wt.%) and add them to a beaker. After stirring, add 2.7 mL of TEOS and stir to mix. After multiple centrifugation and washing, transfer the mixture to an 80℃ oven to dry for 10 h. Calcine the dried sample at 600℃ in air atmosphere for 2 h to obtain the SiO2 support.

[0060] Weigh and measure 0.534 mL of ruthenium nitrite nitrate solution (Ru 1.5% w / v) and add it to 5 mL of deionized water. Impregnate 0.8 g of SiO2 support multiple times evenly. The resulting sample is then dried at 80 °C and transferred to a tube furnace. After calcination at 500 °C for 3 h under a 50 vol.% H2 / Ar atmosphere, it is pressed into tablets to obtain a Ru / SiO2 catalyst sample with a Ru loading of 1 wt.%.

[0061] Comparative Example 2

[0062] Weigh 5g of cerium nitrate hexahydrate and place it in a muffle furnace at 600℃. Calcine it in air for 4 hours to obtain the CeO2 support.

[0063] Weigh and measure 0.534 mL of ruthenium nitrite nitrate solution (Ru 1.5% w / v) and add it to 5 mL of deionized water. Impregnate 0.8 g of CeO2 support multiple times evenly. The resulting sample is then dried at 80 °C and transferred to a tube furnace. After calcination at 500 °C for 3 h under a 50 vol.% H2 / Ar atmosphere, it is pressed into tablets to obtain a Ru / CeO2 catalyst sample with a Ru loading of 1 wt.%.

[0064] Comparative Example 3

[0065] Weigh 5g of cerium nitrate hexahydrate and place it in a muffle furnace at 600℃. Calcine it in air for 4 hours to obtain the CeO2 support.

[0066] 0.0562 g of potassium pentachlororuthenate hydrate was dissolved in 50 mL of deionized water and placed in a beaker to obtain solution A. 0.3 g of CeO2 support was dispersed in 70 mL of deionized water and placed in a beaker to obtain suspension B. HCl solution was then added to solution A and suspension B to adjust the pH of both solutions A and suspension B to 3-4. After 5 h, solution A was slowly added to suspension B via a pump, and the mixture was stirred for another 5 h. After filtration and washing, the mixture was dried in an 80 °C oven for 10 h. After drying, the sample was placed in a tube furnace at 500 °C and calcined for 3 h under a 50 vol.% H2 / Ar atmosphere to obtain a Ru / CeO2 catalyst with a Ru loading of 1 wt.%.

[0067] Table 1 Sample preparation parameters for the examples and comparative examples

[0068]

[0069]

[0070] Table 2 Structural parameters of the embodiments and comparative examples

[0071] sample <![CDATA[Specific surface area (m 2 ·g -1 )]]> <![CDATA[Pore volume (cm 3 ·g -1 )]]> Aperture (nm) Example 1 543 0.82 6.2 Comparative Example 1 26.5 0.24 40.8 Comparative Example 2 80.2 0.16 7.5 Comparative Example 3 82.4 0.17 6.9

[0072] Activity testing conditions: The feed gas was pure ammonia, and the catalyst was pre-reduced at 500℃ for 3 hours. The test space velocity was 30000 mL·g. -1 h -1 The test temperature range was 400–600℃. The catalyst activity was expressed as NH3 conversion rate, calculated as: Ammonia conversion rate = (Initial ammonia content - Ammonia content after treatment) / Initial ammonia content × 100%. The activity evaluation results of the examples and comparative examples are shown in the table below:

[0073] Table 3. Activity evaluation results of the examples and comparative examples.

[0074]

[0075] As shown in Table 3, the catalysts prepared in Examples 1-6 exhibit good performance at high space velocities (30000 mL·g⁻¹). -1 h -1 The CeO2 / SiO2 support exhibits high ammonia decomposition performance, with Example 1 showing an ammonia conversion rate as high as 99.9% at 550℃. The CeO2 / SiO2 support prepared by electrostatic adsorption in this invention possesses a large specific surface area and a porous structure. Its surface CeO2 is uniformly distributed and highly stable, exhibiting excellent affinity for metals. Furthermore, the surface CeO2 provides abundant oxygen vacancies for Ru, promoting electron transfer between the support and the active component, placing Ru in an electron-rich state, which is beneficial for the forward reaction.

[0076] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A method for preparing a Ru / CeO2-SiO2 catalyst, characterized in that: Includes the following steps: (1) Disperse the silicon precursor in an alcohol-water solvent, add a precipitant and a surfactant, cetyltrimethylammonium bromide, while stirring, and continue stirring for 4-12 hours; (2) After centrifuging and drying the precipitate obtained in step (1), it is calcined in an air atmosphere to obtain spherical SiO2; (3) The spherical SiO2 obtained in step (2) is ultrasonically dispersed in cerium nitrate solution, NaOH solution is added, and after reacting for 5 to 10 minutes, the precipitate obtained is filtered, dried, and calcined in air atmosphere to obtain the composite carrier CeO2 / SiO2. (4) Disperse the composite carrier CeO2 / SiO2 obtained in step (3) by ultrasonication to obtain suspension A. Prepare ruthenium precursor into solution B. Add HCl solution to suspension A and solution B respectively to adjust their pH to 3~4. (5) Slowly add solution B to suspension A, react for 1-12 h, filter, dry and calcine to obtain the Ru / CeO2-SiO2 catalyst.

2. The method according to claim 1, characterized in that: In step (1), the volume ratio of silicon precursor to precipitant is 5~25:1; the mass ratio of silicon precursor to surfactant CTAB is 5~9:

1. The silicon precursor is at least one of silica sol, tetramethoxysilane, sodium metasilicate, and tetraethyl orthosilicate. The precipitant is at least one of ammonia, ammonium carbonate, potassium carbonate, sodium hydroxide, and potassium hydroxide. The volume ratio of alcohol to water in the alcohol-water solvent is 1:5, and the alcohol is at least one of pentanol, ethanol, and ethylene glycol.

3. The method according to claim 1, characterized in that: The roasting temperature in step (2) is 500-900 ℃ and the time is 1-6 h.

4. The method according to claim 1, characterized in that: The concentration of the NaOH solution in step (3) is 2-4 mol / L; the calcination temperature is 350-750 ℃ ​​and the time is 9-15 h.

5. The method according to claim 1, characterized in that: The ruthenium precursor in step (4) is at least one of potassium hexachlororuthenate, potassium pentachlororuthenate hydrate, and ammonium pentachlororuthenate hydrate; the concentration of the HCl solution is 1~5 mol / L.

6. The method according to claim 1, characterized in that: The calcination in step (5) is carried out in a 50 vol.% H2 / Ar mixed gas at 300-600 °C for 2-6 h.

7. A Ru / CeO2-SiO2 catalyst prepared by the method according to any one of claims 1-6, characterized in that: The catalyst includes an active component and a support, wherein the active component is ruthenium and the support is CeO2 / SiO2; in the catalyst, the mass percentage of the active component Ru is 0.5-1.5% and the mass percentage of CeO2 is 12-35%.

8. The application of a Ru / CeO2-SiO2 catalyst prepared by the method according to any one of claims 1-6 or the Ru / CeO2-SiO2 catalyst according to claim 7 in ammonia decomposition for hydrogen production.

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