Ruthenium / nano ceria-based heterojunction catalyst, preparation method and application thereof
Ruthenium/nano-cerium dioxide-based heterojunction catalysts were prepared by co-precipitation and UV treatment, which solved the problems of high cost and instability of Ru-based catalysts in the ammonia decomposition hydrogen production process, and achieved efficient and environmentally friendly ammonia decomposition hydrogen production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHEJIANG UNIV OF TECH
- Filing Date
- 2025-01-03
- Publication Date
- 2026-04-28
AI Technical Summary
Existing Ru-based catalysts for hydrogen production from ammonia decomposition suffer from problems such as high cost, easy sintering and deactivation, and instability in acidic environments. Furthermore, traditional preparation methods may introduce impurities and structural damage.
Ruthenium/nano-cerium dioxide-based heterojunction catalysts were prepared by co-precipitation. Ruthenium was uniformly dispersed at a low temperature by UV light reduction treatment and combined with a metal oxide substrate to form a heterojunction, which promoted electron transport and active site distribution.
The catalyst achieves efficient ammonia decomposition for hydrogen production at lower temperatures, improving catalyst activity and stability, reducing energy consumption and chemical waste generation. The catalyst achieves an ammonia conversion rate of up to 99.7% at 500℃.
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Figure CN119733508B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of catalyst technology, specifically to a ruthenium / nano-cerium dioxide-based heterojunction catalyst, its preparation method, and its application. Background Technology
[0002] Ammonia-to-hydrogen energy can not only solve the challenges of hydrogen storage and transportation, improving the stability and security of energy supply, but also achieve zero carbon emissions in end-use energy, which is of great significance for promoting the green and low-carbon transformation of our energy structure.
[0003] The main catalysts for ammonia decomposition to hydrogen production are Ru-based, Ni-based, and Fe-based. Ni-based and Fe-based catalysts generally face the problems of high reaction temperatures and high energy consumption. Ru-based catalysts, due to their excellent activity, can reduce the reaction temperature of ammonia decomposition to hydrogen production to 500℃. However, Ru, as a precious metal, is expensive, and the Ru metal content in highly active catalysts needs to reach more than 2 wt%, leading to high costs. Furthermore, Ru-based catalysts are prone to sintering and deactivation, lacking regeneration capabilities, and can only be reconstituted by recovering the Ru precious metal. Therefore, designing highly stable and highly active precious metal-supported catalysts is particularly important. In the prior art, patent CN 118403640 A provides a method for preparing a ruthenium-based catalyst. This method involves mixing a ruthenium source with a support and calcining it to obtain a precursor; mixing the precursor (or a reduced precursor) with a sulfur source and modifying it through calcination or a multi-pulse atomic layer deposition strategy to obtain the ruthenium-based catalyst. The prepared ruthenium-based catalyst exhibits high CO2 catalytic hydrogenation activity.
[0004] However, the method described above requires mixing the precursor with the sulfur source and performing modification treatment, which may introduce additional impurities and potential pollution problems. In addition, the method involves multiple calcination steps involving ruthenium active components and the calcination temperature can reach up to 800°C, which may lead to the sintering of ruthenium active components. Summary of the Invention
[0005] This invention is made to solve the above-mentioned problems, and aims to provide a ruthenium / nano-cerium dioxide-based heterojunction catalyst, its preparation method and application.
[0006] A first aspect of the present invention provides a method for preparing a ruthenium / nano-cerium dioxide-based heterojunction catalyst, characterized by comprising the following steps:
[0007] (1) Cerium salt was precipitated on a metal oxide substrate by co-precipitation, and then aged and calcined to obtain a nano-cerium dioxide heterostructure carrier;
[0008] (2) The nano-cerium dioxide heterojunction support is mixed with a ruthenium source and then subjected to ultraviolet light reduction treatment to obtain the ruthenium / nano-cerium dioxide-based heterojunction catalyst.
[0009] This invention utilizes a co-precipitation method to uniformly precipitate cerium salts onto a metal oxide substrate, facilitating the formation of highly dispersed nano-cerium dioxide particles. The nano-sized cerium dioxide possesses a large specific surface area, providing more active sites for subsequent ruthenium attachment. Simultaneously, aging promotes the maturation and crystallization of the nano-cerium dioxide, enhancing its stability. Calcination removes moisture and organic matter from the nano-cerium dioxide particles, resulting in a stable nano-cerium dioxide structure.
[0010] Furthermore, due to the presence of Ce in cerium dioxide 3+ / Ce 4+ Cerium dioxide's variable valence properties allow it to store and release oxygen and donate electrons, enabling it to transfer electrons to Ru metal, thereby lowering the energy barrier for breaking the NH bond and promoting the ammonia decomposition reaction. However, cerium dioxide has poor stability and may undergo phase transitions or structural collapse at high temperatures. It is also not stable enough in acidic environments, which affects the catalyst's stability and lifetime, as well as its application under certain acidic reaction conditions. On the other hand, using cerium dioxide alone may make it difficult to achieve a uniform distribution of active sites, thus affecting the catalyst's efficiency and selectivity.
[0011] Therefore, this invention combines metal oxides and cerium dioxide, overcoming the limitations of a single cerium dioxide support and improving the overall performance of the catalyst. The heterojunction formed between the metal oxide substrate and nano-cerium dioxide promotes electron transfer and enhances catalyst performance. The introduction of metal oxides promotes the uniform distribution of active sites, improving catalyst activity and selectivity. Furthermore, combining with different metal oxides can enhance various catalyst properties. For example, combining with metal oxides with better thermal stability improves the overall thermal stability of the catalyst; combining with alumina, due to its excellent stability in acidic environments, protects cerium dioxide from acidic conditions; and combining with titanium dioxide enhances the overall mechanical strength of the catalyst structure.
[0012] Furthermore, this invention mixes a ruthenium source with a nano-cerium dioxide heterojunction support to ensure that the ruthenium precursor is uniformly distributed on the support surface. Ultraviolet light irradiation is used to induce a reduction reaction in the ruthenium precursor, converting it into catalytically active metallic ruthenium. This ensures that the metallic ruthenium is uniformly dispersed on the nano-cerium dioxide heterojunction support, avoiding the particle aggregation problems that may occur with simple mixing and calcination. This results in more uniform and smaller metallic ruthenium nanoparticles, increasing the number and diversity of active sites on the catalyst, thereby improving catalytic efficiency.
[0013] Meanwhile, ultraviolet irradiation can be carried out at a lower temperature, which is gentler than high-temperature roasting. This avoids the damage to the support structure that may be caused by high-temperature roasting, helps maintain the stability of the catalyst structure, reduces thermal damage, and eliminates the need for additional chemical reagents, such as sulfur sources. This reduces the generation of chemical waste and is more environmentally friendly.
[0014] This invention utilizes ultraviolet (UV) irradiation to increase the coupling between ruthenium (Ru) and cerium dioxide (CdO), allowing highly dispersed Ruthenium to be directionally loaded onto a CdO support and deposited on a metal oxide substrate. This also enhances the interaction between Ru and CdO, effectively suppressing Ruthenium agglomeration. This structural design not only strengthens the interaction between Ruthenium and CdO but also promotes electron transport from the metal oxide substrate to CdO and then to Ruthenium. This electron transport mechanism significantly lowers the dissociation barrier of the NH bond in the ammonia decomposition reaction, thereby accelerating the reaction rate and improving the catalyst's activity.
[0015] This invention achieves efficient ammonia decomposition for hydrogen production at a relatively low temperature (500℃) by optimizing the interaction between metallic ruthenium and nano-cerium dioxide. This is of great significance for reducing energy consumption and improving catalytic efficiency.
[0016] In some embodiments, in step (1), the ruthenium source is ruthenium chloride or carbonyl ruthenium, and the content of ruthenium in the ruthenium source is 0.5wt%-3wt% of the nano-cerium dioxide heterojunction carrier.
[0017] In some embodiments, in step (1), one of ammonia, sodium carbonate or potassium hydroxide is used as a precipitant to precipitate cerium salt onto the metal oxide substrate.
[0018] In some embodiments, in step (1), the metal oxide substrate is one of aluminum oxide, titanium oxide, magnesium oxide, cadmium oxide, or molybdenum oxide.
[0019] In some embodiments, in step (1), the cerium salt is one of cerium nitrate, cerium ammonium nitrate, cerium chloride, or cerium sulfate.
[0020] In some embodiments, in step (1), the nano-cerium dioxide heterojunction carrier has a nano-cerium dioxide particle size of 5-20 nm.
[0021] In this embodiment, cerium salt is uniformly precipitated on a metal oxide substrate via co-precipitation, which helps to form highly dispersed nano-cerium dioxide particles. The formed nano-cerium dioxide particles are 5-20 nm in size and have a higher specific surface area, meaning more active sites are available for catalytic reactions, thereby improving catalytic efficiency. Furthermore, when nano-cerium dioxide forms heterojunctions with other metal oxides, a synergistic effect can occur, which helps to improve the overall performance of the catalyst.
[0022] In some embodiments, in step (1), the precipitation pH is 8~12, the aging time is 4~24h, and the calcination temperature is 500~800℃.
[0023] In some embodiments, step (2) specifically includes: mixing the nano-cerium dioxide heterojunction support with a ruthenium source, irradiating it with a 200-400W UV lamp for 0.5-4h, centrifuging, washing, and drying at 100-120℃ to obtain the ruthenium / nano-cerium dioxide-based heterojunction catalyst.
[0024] In a second aspect, the present invention provides a ruthenium / nano-cerium dioxide-based heterojunction catalyst, characterized in that the ruthenium / nano-cerium dioxide-based heterojunction catalyst is prepared by the preparation method described in the first aspect.
[0025] A third aspect of the present invention provides an application of a ruthenium / nano-cerium dioxide-based heterojunction catalyst, characterized in that the reaction temperature is 400–700°C, the reaction pressure is 0–1 MPa, and the space velocity is 1000–50000 h⁻¹. -1 Under the conditions described in the first aspect, the ruthenium / nano-cerium dioxide-based heterojunction catalyst prepared by the preparation method described in the first aspect or the ruthenium / nano-cerium dioxide-based heterojunction catalyst described in the second aspect is used to catalyze the decomposition of ammonia to produce hydrogen.
[0026] By implementing the above technical solution, the present invention has the following beneficial effects:
[0027] This invention utilizes a co-precipitation method to uniformly precipitate cerium salts onto a metal oxide substrate, facilitating the formation of highly dispersed nano-cerium dioxide particles. The nano-sized cerium dioxide possesses a large specific surface area, providing more active sites for subsequent ruthenium attachment. This invention combines metal oxide and cerium dioxide, overcoming the limitations of a single cerium dioxide support and improving the overall performance of the catalyst. The heterojunction formed between the metal oxide substrate and the nano-cerium dioxide promotes electron transfer, enhancing catalyst performance.
[0028] This invention mixes a ruthenium source with a nano-cerium dioxide heterojunction support to ensure that the ruthenium precursor is uniformly distributed on the support surface. Ultraviolet light irradiation is used to induce a reduction reaction in the ruthenium precursor, converting it into catalytically active metallic ruthenium. This process ensures that the metallic ruthenium is uniformly dispersed on the nano-cerium dioxide heterojunction support, avoiding the particle aggregation problems that may occur with simple mixing and calcination. This results in more uniform and smaller metallic ruthenium nanoparticles, increasing the number and diversity of active sites on the catalyst, thereby improving catalytic efficiency.
[0029] Meanwhile, ultraviolet irradiation can be carried out at a lower temperature, which is gentler than high-temperature roasting. This avoids the damage to the support structure that may be caused by high-temperature roasting, helps maintain the stability of the catalyst structure, reduces thermal damage, and eliminates the need for additional chemical reagents, such as sulfur sources. This reduces the generation of chemical waste and is more environmentally friendly.
[0030] This invention involves directionally loading metallic ruthenium onto nano-cerium dioxide using the aforementioned method. The ruthenium / nano-cerium dioxide is deposited on a metal oxide substrate, which inhibits the aggregation of metallic ruthenium during the catalytic reaction. Simultaneously, the metal oxide substrate can transfer electrons to cerium dioxide, and cerium dioxide further transfers electrons to metallic ruthenium, promoting the dissociation of NH bonds in the ammonia decomposition reaction, accelerating the reaction rate, and improving the reaction activity. The ruthenium / nano-cerium dioxide-based heterojunction catalyst prepared by this invention can catalyze the decomposition of ammonia to hydrogen at 500°C, with an ammonia conversion rate reaching 99.7%. Attached Figure Description
[0031] Figure 1 XRD characterization of the catalysts prepared in Example 1, Comparative Example 8, and Comparative Example 9 of this invention;
[0032] Figure 2 TEM characterization of the catalyst prepared in Example 1 of this invention;
[0033] Figure 3 TEM characterization of the catalyst prepared in Comparative Example 9 of this invention;
[0034] Figure 4 Performance diagram of the ammonia decomposition hydrogen production reaction of the catalyst prepared in Example 1 of this invention. Detailed Implementation
[0035] To make the technical means, creative features, objectives and effects of this invention easy to understand, the invention will be specifically described below in conjunction with embodiments and accompanying drawings. Example 1
[0036] 10.0 g of titanium dioxide was dispersed in a beaker containing 100 mL of water and stirred at 300 r / min to form a suspension. 50 mL of cerium nitrate hexahydrate solution (containing 16.2 g of cerium nitrate hexahydrate) and 6 M ammonia solution were added dropwise to the beaker, with the pH controlled at a constant 9.5. After the addition was completed, the mixture was aged for 24 h, then washed and dried in an oven at 120 °C for 8 h, and then calcined in a muffle furnace at 500 °C for 6 h to obtain a CeO2-TiO2 heterojunction support with an average particle size of approximately 5.7 nm.
[0037] 5g of CeO2-TiO2 heterojunction support was dispersed in a beaker containing 100mL of water and stirred with a magnetic stirrer at 800r / min to form a suspension. A solution containing 0.102g of ruthenium chloride was added, wherein the mass of ruthenium was 1wt% of the CeO2-TiO2 heterojunction support. The mixture was irradiated with a 300W ultraviolet lamp for 1h. After centrifugation and washing, the mixture was dried in an oven at 120℃ to finally obtain a 1wt%Ru / nano CeO2-TiO2 heterojunction catalyst. Example 2
[0038] 10.0 g of titanium dioxide was dispersed in a beaker containing 100 mL of water and stirred at 300 r / min to form a suspension. 50 mL of cerium nitrate hexahydrate solution (containing 16.2 g of cerium nitrate hexahydrate) and 6 M ammonia solution were added dropwise to the beaker, with the pH controlled at a constant 9.5. After the addition was completed, the mixture was aged for 24 h, then washed and dried in an oven at 120 °C for 8 h, and then calcined in a muffle furnace at 500 °C for 6 h to obtain a CeO2-TiO2 heterojunction support with an average particle size of approximately 5.7 nm.
[0039] 5g of CeO2-TiO2 heterojunction support was dispersed in a beaker containing 100mL of water and stirred with a magnetic stirrer at 800r / min to form a suspension. A solution containing 0.051g of ruthenium chloride was added, wherein the mass of ruthenium was 0.5wt% of the CeO2-TiO2 heterojunction support. The mixture was irradiated with a 300W ultraviolet lamp for 1h. After centrifugation and washing, the mixture was dried in an oven at 120℃ to finally obtain a 0.5wt%Ru / nano CeO2-TiO2 heterojunction catalyst. Example 3
[0040] 10.0 g of titanium dioxide was dispersed in a beaker containing 100 mL of water and stirred at 300 r / min to form a suspension. 50 mL of cerium nitrate hexahydrate solution (containing 16.2 g of cerium nitrate hexahydrate) and 6 M ammonia solution were added dropwise to the beaker, with the pH controlled at a constant 9.5. After the addition was completed, the mixture was aged for 24 h, then washed and dried in an oven at 120 °C for 8 h, and then calcined in a muffle furnace at 600 °C for 6 h to obtain a CeO2-TiO2 heterojunction support with an average particle size of approximately 5.7 nm.
[0041] 5g of CeO2-TiO2 heterojunction support was dispersed in a beaker containing 100mL of water and stirred with a magnetic stirrer at 800r / min to form a suspension. A solution containing 0.153g of ruthenium chloride was added, wherein the mass of ruthenium was 1.5wt% of the CeO2-TiO2 heterojunction support. The mixture was irradiated with a 300W ultraviolet lamp for 1h. After centrifugation and washing, the mixture was dried in an oven at 120℃ to obtain a 1.5wt%Ru / nano CeO2-TiO2 heterojunction catalyst. Example 4
[0042] 10.0 g of titanium dioxide was dispersed in a beaker containing 100 mL of water and stirred at 300 r / min to form a suspension. 50 mL of cerium nitrate hexahydrate solution (containing 16.2 g of cerium nitrate hexahydrate) and 6 M potassium hydroxide were added dropwise to the beaker, keeping the pH constant at 9. After the addition was completed, the mixture was aged for 24 h, then washed and dried in an oven at 120 °C for 8 h, and then calcined in a muffle furnace at 600 °C for 6 h to obtain a CeO2-TiO2 heterojunction support with an average particle size of approximately 8.1 nm.
[0043] 5g of CeO2-TiO2 heterojunction support was dispersed in a beaker containing 100mL of water and stirred with a magnetic stirrer at 800r / min to form a suspension. A solution containing 0.105g of carbonyl ruthenium was added, wherein the mass of ruthenium was 1wt% of the CeO2-TiO2 heterojunction support. The mixture was irradiated with a 300W ultraviolet lamp for 1h. After centrifugation and washing, the mixture was dried in an oven at 120℃ to finally obtain a 1wt%Ru / nano CeO2-TiO2 heterojunction catalyst. Example 5
[0044] 10.0 g of zirconia was dispersed in a beaker containing 100 mL of water and stirred at 300 r / min to form a suspension. 50 mL of cerium nitrate hexahydrate solution (containing 16.2 g of cerium nitrate hexahydrate) and 6 M potassium hydroxide were added dropwise to the beaker, keeping the pH constant at 9. After the addition was completed, the mixture was aged for 24 h, then washed and dried in an oven at 120 °C for 8 h, and then calcined in a muffle furnace at 600 °C for 6 h to obtain a CeO2-ZrO2 heterojunction support with an average particle size of approximately 10.9 nm.
[0045] 5g of CeO2-ZrO2 heterojunction support was dispersed in a beaker containing 100mL of water and stirred with a magnetic stirrer at 800r / min to form a suspension. A solution containing 0.105g of carbonyl ruthenium was added, wherein the mass of ruthenium was 1wt% of the CeO2-TiO2 heterojunction support. The mixture was irradiated with a 300W ultraviolet lamp for 1h. After centrifugation and washing, the mixture was dried in an oven at 120℃ to finally obtain a 1wt%Ru / nano CeO2-ZrO2 heterojunction catalyst. Example 6
[0046] 10.0 g of magnesium oxide was dispersed in a beaker containing 100 mL of water and stirred at 300 r / min to form a suspension. 50 mL of cerium nitrate hexahydrate solution (containing 16.2 g of cerium nitrate hexahydrate) and 6 M potassium hydroxide were added dropwise to the beaker, keeping the pH constant at 9. After the addition was completed, the mixture was aged for 24 h, then washed and dried in an oven at 120 °C for 8 h, and then calcined in a muffle furnace at 700 °C for 6 h to obtain the CeO2-MgO heterojunction support. The average particle size of CeO2 was about 7.3 nm.
[0047] 5g of CeO2-MgO heterojunction support was dispersed in a beaker containing 100mL of water and stirred with a magnetic stirrer at 800r / min to form a suspension. A solution containing 0.105g of carbonyl ruthenium was added, wherein the mass of ruthenium was 1wt% of the CeO2-TiO2 heterojunction support. The mixture was irradiated with a 300W ultraviolet lamp for 1h. After centrifugation and washing, the mixture was dried in an oven at 120℃ to finally obtain a 1wt%Ru / nano CeO2-MgO heterojunction catalyst. Example 7
[0048] 10.0 g of titanium dioxide was dispersed in a beaker containing 100 mL of water and stirred at 300 r / min to form a suspension. 50 mL of cerium nitrate hexahydrate solution (containing 16.2 g of cerium nitrate hexahydrate) and 6 M ammonia solution were added dropwise to the beaker, keeping the pH constant at 9. After the addition was completed, the mixture was aged for 48 h, then washed and dried in an oven at 120 °C for 8 h, and then calcined in a muffle furnace at 800 °C for 6 h to obtain a CeO2-TiO2 heterojunction support with an average particle size of approximately 5.7 nm.
[0049] 5g of CeO2-TiO2 heterojunction support was dispersed in a beaker containing 100mL of water and stirred with a magnetic stirrer at 800r / min to form a suspension. A solution containing 0.105g of carbonyl ruthenium was added, wherein the mass of ruthenium was 1wt% of the CeO2-TiO2 heterojunction support. The mixture was irradiated with a 300W ultraviolet lamp for 2h. After centrifugation and washing, the mixture was dried in an oven at 120℃ to finally obtain a 1wt%Ru / nano CeO2-TiO2 heterojunction catalyst. Comparative Example 8
[0050] 50 mL of cerium nitrate hexahydrate solution (containing 16.2 g of cerium nitrate hexahydrate) and 6 M ammonia solution were added dropwise to a beaker, with the pH controlled at a constant 9.5. After the addition was completed, the mixture was aged for 24 h, then washed and dried in an oven at 120 °C for 8 h, and then calcined in a muffle furnace at 500 °C for 6 h to obtain the CeO2 support. The average particle size of CeO2 was approximately 59.0 nm.
[0051] 5g of CeO2 support was dispersed in a beaker containing 100mL of water and stirred with a magnetic stirrer at 800r / min to form a suspension. A solution containing 0.102g of ruthenium chloride was added, wherein the mass of ruthenium was 1wt% of the CeO2 support. The mixture was irradiated with a 300W ultraviolet lamp for 1h. After centrifugation and washing, the mixture was dried in an oven at 120℃ to finally obtain a 1wt% Ru / CeO2 catalyst. Comparative Example 9
[0052] 5g of TiO2 support was dispersed in a beaker containing 100mL of water and stirred with a magnetic stirrer at 800r / min to form a suspension. A solution containing 0.102g of ruthenium chloride was added, wherein the mass of ruthenium was 1wt% of the TiO2 support. The mixture was irradiated with a 300W ultraviolet lamp for 1h. After centrifugation and washing, the mixture was dried in an oven at 120℃ to finally obtain a 1wt% Ru / CeO2 catalyst. Comparative Example 10
[0053] 5g of CeO2 and TiO2 supports were mechanically mixed and dispersed in a beaker containing 100mL of water. The mixture was stirred with a magnetic stirrer at 800r / min to form a suspension. A solution containing 0.102g of ruthenium chloride was added, wherein the mass of ruthenium was 1wt% of the CeO2 and TiO2 mixed support. The mixture was irradiated with a 300W ultraviolet lamp for 1h. After centrifugation and washing, the mixture was dried in an oven at 120℃ to obtain a 1wt% Ru / CeO2 catalyst.
[0054] 5g of CeO2 and TiO2 supports were mechanically mixed and dispersed in a beaker containing 100mL of water. The mixture was stirred with a magnetic stirrer at 800r / min to form a suspension. A solution containing 0.102g of ruthenium chloride was added, wherein the mass of ruthenium was 1wt% of the CeO2 and TiO2 mixed support. The mixture was stirred for 1h, centrifuged, washed, and then dried in an oven at 120℃. The powder was calcined at 500℃ under a hydrogen atmosphere for 2h to finally obtain a 1wt% Ru / CeO2 catalyst.
[0055] The catalysts prepared in Example 1, Comparative Example 8, and Comparative Example 9 were characterized by XRD or TEM to obtain... Figures 1-3 . Figure 1 The XRD characterization of the catalysts of Example 1 and Comparative Examples 8 and 9 is shown. It can be seen that, compared with the catalysts prepared in Comparative Examples 8 and 9, the 1wt%Ru / CeO2-TiO2 catalyst of Example 1 contains the characteristic diffraction peaks of CeO2 and TiO2, while Ru is highly dispersed and does not show any peaks.
[0056] Figure 2The image shows a transmission electron microscope (TEM) image of the 1wt% Ru / CeO2-TiO2 catalyst in Example 1 of the present invention, wherein the TiO2 is in the form of square plates, the nano-CeO2 is loaded on it in the form of dots with an average particle size of about 5.7 nm, and the Ru clusters are loaded on the nano-CeO2.
[0057] Figure 3 Transmission electron microscopy (TEM) images of the 1 wt% Ru / TiO2 catalyst in Comparative Example 9 are shown, in which TiO2 is in the form of square plates, Ru is supported on TiO2, and the average particle size is about 1.7 nm.
[0058] Performance evaluation parameters for ammonia decomposition to hydrogen production reaction: 2 mL of catalyst was placed in a fixed-bed reactor. The catalyst was first reduced with H2 at 500 °C for 2 h, followed by the introduction of high-purity ammonia gas at a space velocity of 20000 h⁻¹. -1 The ammonia conversion rate of the catalyst at 500℃ was tested. Figure 4 The catalyst prepared in Example 1 of this invention was shown to perform at 500°C for 20,000 h. -1 The graph showing the change in ammonia conversion rate over reaction time demonstrates the high stability of the catalyst.
[0059] Table 1. Catalysts in the ammonia decomposition to hydrogen production reaction (500℃, 20000h) of the examples -1 Activity data record table in )
[0060] catalyst ammonia conversion rate Example 1 99.7% Example 2 95.1% Example 3 99.7% Example 4 99.6% Example 5 98.8% Example 6 99.2% Example 7 99.7% Comparative Example 8 94.1% Comparative Example 9 90.6% Comparative Example 10 95.5% Comparative Example 11 94.9%
[0061] In the examples, highly dispersed Ru was directionally loaded onto nano-cerium oxide, forming an electron transport pathway of oxide substrate-cerium dioxide-Ru, which promoted the ammonia decomposition reaction. Simultaneously, UV treatment enhanced the interaction between Ru and cerium dioxide, inhibiting Ru sintering. In Example 2, the catalytic activity decreased due to a halved content of the active component Ru; in Comparative Example 8, the single-component cerium dioxide support had a weak electron-donating ability for Ru; in Comparative Example 9, the Ru particle size on TiO2 was large, resulting in fewer surface active sites; and in Comparative Example 11, which was not treated with UV light, the interaction between Ru and cerium dioxide was relatively weak.
[0062] The above embodiments are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention.
Claims
1. The application of a ruthenium / nano-cerium dioxide-based heterojunction catalyst, characterized in that, The reaction temperature was 400–700℃, the reaction pressure was 0–1 MPa, and the space velocity was 1000–50000 h⁻¹. -1 Under the conditions described, the ruthenium / nano-cerium dioxide-based heterojunction catalyst is used to catalyze the decomposition of ammonia to produce hydrogen. The preparation method of the ruthenium / nano-cerium dioxide-based heterojunction catalyst includes the following steps: (1) using ammonia, sodium carbonate or potassium hydroxide as a precipitant, precipitating cerium salt on a metal oxide substrate by precipitation, and aging and calcining to obtain a nano-cerium dioxide heterojunction support; the metal oxide substrate is one of alumina, titanium oxide, magnesium oxide, zirconium oxide or molybdenum oxide. (2) The nano-cerium dioxide heterojunction support is mixed with a ruthenium source and then subjected to ultraviolet light reduction treatment to obtain the ruthenium / nano-cerium dioxide-based heterojunction catalyst.
2. The application according to claim 1, characterized in that, In step (1), the ruthenium source is ruthenium chloride or carbonyl ruthenium, and the content of ruthenium in the ruthenium source is 0.5wt%-3wt% of the nano-cerium dioxide heterojunction carrier.
3. The application according to claim 1, characterized in that, In step (1), the cerium salt is one of cerium nitrate, cerium ammonium nitrate, cerium chloride or cerium sulfate.
4. The application according to claim 3, characterized in that, In step (1), the nano-cerium dioxide heterojunction carrier has a nano-cerium dioxide particle size of 5-20 nm.
5. The application according to claim 4, characterized in that, In step (1), the pH of the precipitate is 8~12, the aging time is 4~24h, and the calcination temperature is 500~800℃.
6. The application according to claim 5, characterized in that, Step (2) specifically includes: mixing the nano-cerium dioxide heterojunction support with a ruthenium source, irradiating it with a 200-400W UV lamp for 0.5-4 hours, centrifuging, washing, and drying at 100-120℃ to obtain the ruthenium / nano-cerium dioxide-based heterojunction catalyst.