Ammonia decomposition catalyst with in-situ formed BaCeO3 as auxiliary agent and preparation method and application thereof

Abstract

The invention belongs to the technical field of ammonia decomposition catalyst preparation, and particularly relates to an ammonia decomposition catalyst with in-situ formed BaCeO3 as an auxiliary agent and a preparation method and application thereof. According to the prepared ammonia decomposition catalyst, the rare earth oxide serves as a carrier, a BaCeO3 perovskite structure is generated in situ in an ammonia decomposition catalytic reaction through the synergistic effect of a deposition-precipitation method and a Ba auxiliary agent, and the low-temperature activity is remarkably improved. Experiments show that the H2 yield of the catalyst at 500 DEG C can reach 28.8 mmol.gcal <-1 >. Min <-1 >, and the catalyst is excellent in stability and suitable for efficient ammonia decomposition hydrogen production.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of ammonia decomposition catalysts, and particularly relates to an ammonia decomposition catalyst with in-situ formed BaCeO3 as an assistant, and a preparation method and application thereof. Background Art

[0002] The information disclosed in the background art of the present invention is only intended to increase the understanding of the overall background of the present invention, and is not necessarily regarded as an admission or an indication in any form that this information constitutes the prior art already known to those of ordinary skill in the art.

[0003] Hydrogen energy is regarded as an ideal alternative to fossil energy due to its rich sources, green and low-carbon, renewable, high combustion calorific value and other clean and efficient characteristics. However, the safe storage and transportation of hydrogen is still a technical bottleneck. Ammonia, as a hydrogen-rich compound (hydrogen mass density 17.8 wt.%), has become a very promising hydrogen storage medium due to its easy liquefaction, safe storage and transportation, high purity of decomposition products, and no carbon emissions. However, the activation energy barrier of the ammonia decomposition reaction (2NH3(g)→N2(g)+3H2(g); ΔH=+92 kJ·mol −1 -1) is relatively high, and the preparation methods mainly focus on the regulation of the size of active metals, and the regulation of the active sites and electronic structures of the catalysts is limited, resulting in the difficulty of significantly improving the ammonia decomposition conversion rate, which is mainly limited by the high-temperature and strong reduction environment of the ammonia decomposition reaction. Therefore, the preparation of catalysts with low temperature and high activity is the trend.

[0004] In the prior art, noble metal catalysts, such as Ru-based catalysts, have excellent low-temperature activity, but are costly and difficult to be applied to actual industrial production; non-noble metal catalysts, such as Ni-based catalysts, have low costs, but have the problem that the ammonia decomposition activity at low temperatures is not as good as that of noble metal catalysts. Therefore, how to achieve efficient ammonia decomposition to produce hydrogen by transition metal Ni-based catalysts at low temperatures has become the current research focus.

[0005] Research shows that the optimization of the support and the assistant can improve the activity of Ni-based catalysts. For example, rare earth oxide supports have the characteristics of stable chemical properties due to their unique 4 f -electron layer structure, and their basic surfaces and other characteristics are helpful for catalytic reactions; perovskite-type oxide supports have strong basicity and excellent electron conductivity, which are beneficial to optimizing the electronic state of active metals, promoting the activation of NH3, and accelerating the desorption of N2 and H2; alkaline earth metal assistants can improve the electron-donating ability of the catalyst and enhance the electron cloud density around the active metal, that is, promote the associative desorption of N2 through electron regulation. However, in the prior art, the compatibility between the assistant and the support is insufficient, and the perovskite structure characteristics are not fully utilized, resulting in limited improvement in the activity of the catalyst. Summary of the Invention

[0006] In view of the needs of the prior art, the purpose of the present invention is to provide an ammonia decomposition catalyst with in-situ formed BaCeO3 as an additive, and its preparation method and application. By introducing an in-situ formed BaCeO3 perovskite additive and combining with a rare earth oxide support, the present invention prepares a nickel-based ammonia decomposition catalyst that is highly efficient, stable, and low-cost at low temperatures, and significantly improves the catalytic activity and hydrogen production rate of the catalyst.

[0007] Specifically, the present invention provides the following technical solutions: In the first aspect of the present invention, an ammonia decomposition catalyst with in-situ formed BaCeO3 as an additive is provided. The ammonia decomposition catalyst includes a rare earth oxide support CeO2 and an active component metal nickel compound and an alkaline earth metal additive barium compound supported on the support. Among them, the loading amount of nickel in the active component metal nickel compound is 15-25 wt.%, the loading amount of barium in the alkaline earth metal additive barium compound is 1-15 wt.%, and the alkaline earth metal additive barium compound reacts with the rare earth oxide support in-situ during the ammonia decomposition reaction to form a BaCeO3 perovskite structure.

[0008] Preferably, the active component metal nickel compound is NiO, and the alkaline earth metal additive barium compound is BaCO3.

[0009] Preferably, the ammonia decomposition catalyst is in the form of nanospheres with a size of 60-70 nm, a specific surface area of 130-135 m 2 / g, a pore volume of 0.3-0.35 cm 3 / g, and a pore size of 4.5-4.7 nm.

[0010] More preferably, the specific surface area of the ammonia decomposition catalyst is 133.2 m 2 / g, the pore volume is 0.31 cm 3 / g, and the pore size is 4.65 nm.

[0011] Preferably, the particle size of the ammonia decomposition catalyst is 20-40 mesh.

[0012] In the second aspect of the present invention, a preparation method of the above ammonia decomposition catalyst with in-situ formed BaCeO3 as an additive is provided, including the following steps: S1. Dissolve a cerium salt in a mixed solvent, carry out a solvothermal reaction, and calcine the precipitate obtained after centrifugal washing of the product to obtain a CeO2 nanosphere support; S2. Add a barium salt to a nickel salt solution, drop the resulting mixed solution into an aqueous solution of the CeO2 nanosphere support, and at the same time drop a sodium salt solution to adjust the pH to 8-10. Then, after aging, suction filtration, drying, and calcination, the ammonia decomposition catalyst is obtained.

[0013] Preferably, in step S1, the mixed solvent is a mixed solution of water, ethylene glycol and glacial acetic acid, and the volume ratio of water, ethylene glycol to glacial acetic acid is (1.5 - 2.5):(50 - 55):(1.5 - 2.5), and the concentration of glacial acetic acid ≥ 99.5%; the dosage ratio of the cerium salt to the mixed solvent is 1 g:(25 - 30) mL; the cerium salt includes cerium nitrate hexahydrate.

[0014] Preferably, in step S1, the temperature of the solvothermal reaction is 170 - 190 °C, and the reaction time is 180 - 240 min.

[0015] Preferably, in step S1, the calcination treatment is carried out by heating to 350 - 450 °C at a heating rate of 1 - 3 °C / min and calcining for 0.5 - 1.5 h.

[0016] Preferably, in step S2, the barium salt includes barium nitrate, the nickel salt includes nickel nitrate, and the sodium salt includes sodium carbonate; the concentration of the nickel salt solution is 0.08 - 0.12 M; the concentration of the sodium salt is 0.4 - 0.6 M; the dosage ratio of the barium salt, nickel salt solution to the sodium salt solution is (0.1 - 0.15) g:(25 - 26) mL:(20 - 30) mL.

[0017] Preferably, in step S2, the pH is 9; the aging time is 1 - 1.5 h; the drying temperature is 65 - 75 °C, and the time is 7 - 9 h; the calcination is carried out by heating to 350 - 450 °C at a heating rate of 1 - 3 °C / min, and the calcination time is 3 - 5 h.

[0018] In the third aspect of the present invention, there is provided an application of the ammonia decomposition catalyst with in-situ formed BaCeO3 as an auxiliary agent described in the first aspect in the ammonia decomposition to hydrogen reaction.

[0019] Preferably, the ammonia decomposition catalyst is activated in a pure ammonia atmosphere at 600 °C for 0.5 - 1.5 h to reduce NiO to metallic nickel, and at the same time, the Ba species forms BaCeO3 with the support CeO2.

[0020] The beneficial effects obtained by one or more of the above technical solutions of the present invention are as follows: (1) The present invention selects the rare earth oxide CeO2 with both surface weak basicity and good thermal stability as the support, uses the alkaline earth metal Ba with strong electron-donating ability as the auxiliary agent, and further combines the transition metal Ni with low price, good performance and great practical application potential to construct a Ni - Ba / CeO2 ternary catalyst, realizing the efficient ammonia decomposition to hydrogen of the Ni-based catalyst at low temperature.

[0021] (2) In the present invention, a new species of BaCeO3 is in-situ formed during the ammonia decomposition reaction process in the catalyst with CeO2 as the carrier after introducing Ba. This species has strong basicity and excellent electron conductivity, which is beneficial to the dissociation of NH3 and promotes the associative desorption of N2 and H2. The H2 yield at 500 °C can reach 28.8 mmol·g cat −1 ·min −1 , far exceeding other Ni-based catalysts reported in the prior art and even exceeding some Ru-based noble metal catalysts (GHSV = 30,000 mL·g cat -1 ·h -1 ). BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0023] Figure 1 TEM image of the 20Ni-7Ba / CeO2 catalyst prepared in Example 1 of the present invention; Figure 2 XRD patterns after the catalytic reaction of the ammonia decomposition catalysts prepared in Example 1 and Comparative Example 5 of the present invention, where a is the XRD pattern of 20Ni-7Ba / CeO2 and b is the XRD pattern of 20Co-7Ba / CeO2; Figure 3 H2 reaction order of the ammonia decomposition catalysts prepared in Example 1 and Comparative Example 7 of the present invention; Figure 4 Ni 2 of the ammonia decomposition catalysts prepared in Example 1 and Comparative Example 7 of the present invention p quasi in-situ XPS spectra; Figure 5 CO2 temperature-programmed desorption experiment CO2-TPD of the ammonia decomposition catalysts prepared in Example 1 and Comparative Example 7 of the present invention; Figure 6 Stability test diagram of the ammonia decomposition catalyst prepared in Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] It should be noted that the following detailed description is exemplary and is intended to provide further illustration of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0025] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0026] Example 1: This example provides an ammonia decomposition catalyst with in-situ formed BaCeO3 as an additive and its preparation method. (1) Preparation of CeO2 nanosphere support (solvothermal method): Weigh 2.0 g of cerium nitrate hexahydrate in a 100 mL polytetrafluoroethylene inner liner, then add 2 mL of high-purity water, 52 mL of ethylene glycol, and 2 mL of glacial acetic acid respectively, and then stir for 30 min. After stirring, place the inner liner in a stainless steel autoclave, set the temperature of the oven to 180 °C, and react for 200 min. After the solvothermal reaction, place the obtained product in a centrifuge tube for centrifugal washing, wash 4 times with high-purity water and 1 time with ethanol respectively. After washing, place the obtained precipitate in an oven at 70 °C and dry for 6 h. After drying, grind it into powder with an agate mortar, and then heat it to 400 °C in a tubular furnace at a heating rate of 2 °C / min, and calcine for 1 h to obtain the CeO2 nanosphere support.

[0027] (2) Preparation of 20Ni-7Ba / CeO2 catalyst (deposition precipitation method): Disperse 0.5 g of CeO2 nanosphere support in 25 mL of high-purity water, and ultrasonically stir it at room temperature to make it completely dispersed, denoted as solution A; then measure 25.6 mL of 0.1 M Ni(NO3)2 solution into a 50 mL beaker (preparation of 0.1 M Ni(NO3)2 solution: weigh 2.91 g of Ni(NO3)2·6H2O and dissolve it in 100 mL of high-purity water), then weigh 0.13 g of Ba(NO3)2 and add it to the above beaker containing Ni(NO3)2 solution, and ultrasonically stir and mix them at room temperature, denoted as solution B; then slowly add solution B dropwise to solution A, and at the same time add 20 mL of 0.5 M Na2CO3 solution throughout the process to maintain the pH of the whole system at 9. After dropping, stir the mixed solution at room temperature for 0.5 h and age for 1 h. Finally, filter it with 1 L of high-purity water by suction filtration, dry the filtered sample at 70 °C for 8 h, and after drying, heat it to 400 °C in a muffle furnace at a heating rate of 2 °C / min and calcine for 4 h. The final product obtained is denoted as 20Ni-7Ba / CeO2.

[0028] Example 2: This example provides an ammonia decomposition catalyst with in-situ formed BaCeO3 as an additive and its preparation method. The differences between this embodiment and Embodiment 1 are as follows: In step (2), the 20Ni-2Ba / CeO2 catalyst prepared in this embodiment, and the specific preparation method of step (2) is as follows: Disperse 0.5 g of CeO2 nanosphere support in 25 mL of high-purity water, and ultrasonically stir it at room temperature until it is completely dispersed, denoted as solution A; Subsequently, measure 25.6 mL of 0.1 M Ni(NO3)2 solution into a 50 mL beaker (the 0.1 M Ni(NO3)2 solution is prepared by weighing 2.91 g of Ni(NO3)2·6H2O and dissolving it in 100 mL of high-purity water), then weigh 0.024 g of Ba(NO3)2 and add it to the beaker containing the Ni(NO3)2 solution, and ultrasonically stir and mix them at room temperature, denoted as solution B; Then, slowly add solution B dropwise to solution A, and simultaneously add 20 mL of 0.5 M Na2CO3 solution throughout the process to maintain the pH of the whole system at 9. After the addition is completed, stir the mixed solution at room temperature for 0.5 h and age it for 1 h. Finally, filter it with 1 L of high-purity water by suction filtration, and the filtered sample is dried at 70 °C for 8 h. After drying, it is calcined in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h, and the final product obtained is denoted as 20Ni-2Ba / CeO2.

[0029] Example 3: This example provides an ammonia decomposition catalyst with in-situ formed BaCeO3 as an additive and its preparation method The difference between this embodiment and Embodiment 1 lies in that: in step (2), the 20Ni-5Ba / CeO2 catalyst prepared in this embodiment, and the specific preparation method of step (2) is as follows: Disperse 0.5 g of CeO2 nanosphere support in 25 mL of high-purity water, and ultrasonically stir it at room temperature to make it completely dispersed, denoted as solution A; Subsequently, measure 25.6 mL of 0.1 M Ni(NO3)2 solution into a 50 mL beaker (the preparation of 0.1 M Ni(NO3)2 solution: weigh 2.91 g of Ni(NO3)2·6H2O and dissolve it in 100 mL of high-purity water), then weigh 0.063 g of Ba(NO3)2 and add it to the beaker containing Ni(NO3)2 solution, and ultrasonically stir it at room temperature to make the two fully mixed, denoted as solution B; Then add solution B dropwise to solution A, and simultaneously add 20 mL of 0.5 M Na2CO3 solution throughout the process to keep the pH of the whole system controlled at 9. After the addition is completed, stir the mixed solution at room temperature for 0.5 h and age for 1 h. Finally, filter it with 1 L of high-purity water by suction filtration, and dry the filtered sample at 70 °C for 8 h. After drying, heat it to 400 °C in a muffle furnace at a heating rate of 2 °C / min and calcine for 4 h. The final product obtained is denoted as 20Ni-5Ba / CeO2.

[0030] Comparative Example 1: This comparative example provides an ammonia decomposition catalyst with in-situ formed BaCeO3 as an additive and its preparation method The difference between this comparative example and Example 1 lies in: in step (2), the 20Ni-1Ba / CeO2 catalyst prepared in this example, and the specific preparation method of step (2) is as follows: Disperse 0.5 g of CeO2 nanosphere support in 25 mL of high-purity water, and ultrasonically stir it at room temperature until it is completely dispersed, denoted as solution A; Subsequently, measure 25.6 mL of 0.1 M Ni(NO3)2 solution into a 50 mL beaker (the 0.1 M Ni(NO3)2 solution is prepared as follows: weigh 2.91 g of Ni(NO3)2·6H2O and dissolve it in 100 mL of high-purity water), then weigh 0.012 g of Ba(NO3)2 and add it to the beaker containing the Ni(NO3)2 solution, and ultrasonically stir it at room temperature to fully mix the two, denoted as solution B; Then, add solution B dropwise to solution A, and simultaneously add 20 mL of 0.5 M Na2CO3 solution throughout the process to maintain the pH of the entire system at 9. After the addition is completed, stir the mixed solution at room temperature for 0.5 h and age it for 1 h. Finally, perform suction filtration with 1 L of high-purity water, and dry the filtered sample at 70 °C for 8 h. After drying, calcine it in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h, and the final product obtained is denoted as 20Ni-1Ba / CeO2.

[0031] Comparative Example 2: This example provides an ammonia decomposition catalyst with in-situ formed BaCeO3 as an auxiliary agent and its preparation method The difference between this comparative example and Example 1 lies in: in step (2), the 20Ni-15Ba / CeO2 catalyst prepared in this example, and the specific preparation method of step (2) is as follows: Disperse 0.5 g of CeO2 nanosphere support in 25 mL of high-purity water, and ultrasonically stir it at room temperature to make it completely dispersed, denoted as solution A; Subsequently, measure 26.2 mL of 0.1 M Ni(NO3)2 solution into a 50 mL beaker (the preparation of 0.1 M Ni(NO3)2 solution: weigh 2.91 g of Ni(NO3)2·6H2O and dissolve it in 100 mL of high-purity water), then weigh 0.22 g of Ba(NO3)2 and add it to the beaker containing Ni(NO3)2 solution, and ultrasonically stir it at room temperature to make the two fully mixed, denoted as solution B; Then add solution B dropwise to solution A, and simultaneously add 20 mL of 0.5 M Na2CO3 solution throughout the process to maintain the pH of the whole system at 9. After the dropwise addition is completed, stir the mixed solution at room temperature for 0.5 h and age for 1 h. Finally, filter it with 1 L of high-purity water by suction filtration, and dry the filtered sample at 70 °C for 8 h. After drying, heat it to 400 °C at a heating rate of 2 °C / min in a muffle furnace and calcine for 4 h. The final product obtained is denoted as 20Ni-15Ba / CeO2.

[0032] Comparative Example 3: This comparative example provides an ammonia decomposition catalyst with in-situ formed BaCeO3 as an additive and its preparation method The difference between this comparative example and Example 1 lies in: in step (2), the 15Ni-7Ba / CeO2 catalyst prepared in this example, and the specific preparation method of step (2) is as follows: Disperse 0.5 g of CeO2 nanosphere support in 25 mL of high-purity water, and ultrasonically stir it at room temperature to make it completely dispersed, denoted as solution A; Subsequently, measure 16.4 mL of 0.1 M Ni(NO3)2 solution into a 50 mL beaker (the 0.1 M Ni(NO3)2 solution is prepared as follows: weigh 2.91 g of Ni(NO3)2·6H2O and dissolve it in 100 mL of high-purity water), then weigh 0.086 g of Ba(NO3)2 and add it to the beaker containing the Ni(NO3)2 solution, and ultrasonically stir and mix them at room temperature, denoted as solution B; Then, slowly add solution B dropwise to solution A, and simultaneously add 20 mL of 0.5 M Na2CO3 solution throughout the process to maintain the pH of the whole system at 9. After the addition is completed, stir the mixed solution at room temperature for 0.5 h and age it for 1 h. Finally, perform suction filtration with 1 L of high-purity water, and the filtered sample is dried at 70°C for 8 h. After drying, it is calcined in a muffle furnace at a heating rate of 2°C / min to 400°C for 4 h, and the final product obtained is denoted as 15Ni-7Ba / CeO2.

[0033] Comparative Example 4: This comparative example provides an ammonia decomposition catalyst with in-situ formed BaCeO3 as an additive and its preparation method The difference between this comparative example and Example 1 lies in: In step (2), the 25Ni-7Ba / CeO2 catalyst prepared in this example, and the specific preparation method of step (2) is as follows: Disperse 0.5 g of CeO2 nanosphere support in 25 mL of high-purity water, and ultrasonically stir it at room temperature to make it completely dispersed, denoted as solution A; Subsequently, measure 31.4 mL of 0.1 M Ni(NO3)2 solution into a 50 mL beaker (the preparation of 0.1 M Ni(NO3)2 solution: Weigh 2.91 g of Ni(NO3)2·6H2O and dissolve it in 100 mL of high-purity water), then weigh 0.098 g of Ba(NO3)2 and add it to the beaker containing Ni(NO3)2 solution, and ultrasonically stir and mix them at room temperature to make them fully mixed, denoted as solution B; Then, slowly add solution B dropwise to solution A, and simultaneously add 20 mL of 0.5 M Na2CO3 solution throughout the process to keep the pH of the whole system controlled at 9. After the addition is completed, stir the mixed solution at room temperature for 0.5 h and age for 1 h. Finally, perform suction filtration with 1 L of high-purity water, dry the filtered sample at 70 °C for 8 h, and after drying, heat it to 400 °C in a muffle furnace at a heating rate of 2 °C / min and calcine for 4 h. The final product obtained is denoted as 25Ni-7Ba / CeO2.

[0034] Comparative Example 5: This comparative example provides an ammonia decomposition catalyst and its preparation method The difference between this comparative example and Example 1 lies in: In step (2), the 20Co-7Ba / CeO2 catalyst prepared in this example, and the specific preparation method of step (2) is as follows: Disperse 0.5 g of CeO2 nanosphere support in 25 mL of high-purity water, and ultrasonically stir it at room temperature to make it completely dispersed, denoted as solution A; Subsequently, measure 25.6 mL of 0.1 M Co(NO3)2 solution into a 50 mL beaker (the preparation of 0.1 M Co(NO3)2 solution: Weigh 2.91 g of Co(NO3)2·6H2O and dissolve it in 100 mL of high-purity water), then weigh 0.13 g of Ba(NO3)2 and add it to the beaker containing Co(NO3)2 solution, and ultrasonically stir and mix them at room temperature to make them fully mixed, denoted as solution B; Then, slowly add solution B dropwise to solution A, and simultaneously add 20 mL of 0.5 M Na2CO3 solution throughout the process to keep the pH of the whole system controlled at 9. After the addition is completed, stir the mixed solution at room temperature for 0.5 h and age for 1 h. Finally, perform suction filtration with 1 L of high-purity water, dry the filtered sample at 70 °C for 8 h, and after drying, heat it to 400 °C in a muffle furnace at a heating rate of 2 °C / min and calcine for 4 h. The final product obtained is denoted as 20Co-7Ba / CeO2.

[0035] Comparative Example 6: This comparative example provides an ammonia decomposition catalyst and a preparation method thereof The difference between this comparative example and Example 1 is as follows: In step (2), the 20Fe-7Ba / CeO2 catalyst prepared in this example. The specific preparation method of step (2) is as follows: Disperse 0.5 g of CeO2 nanosphere support in 25 mL of high-purity water, and ultrasonically stir it at room temperature to make it completely dispersed, denoted as solution A; Subsequently, measure 24.5 mL of 0.1 M Fe(NO3)3 solution into a 50 mL beaker (the 0.1 M Fe(NO3)3 solution is prepared by weighing 4.04 g of Fe(NO3)3·9H2O and dissolving it in 100 mL of high-purity water). Then, weigh 0.091 g of Ba(NO3)2 and add it to the beaker containing the Fe(NO3)3 solution, and ultrasonically stir and mix them at room temperature, denoted as solution B; Then, slowly add solution B dropwise to solution A, and simultaneously add 20 mL of 0.5 M Na2CO3 solution throughout the process to maintain the pH of the entire system at 9. After the addition is completed, stir the mixed solution at room temperature for 0.5 h and age for 1 h. Finally, perform suction filtration with 1 L of high-purity water. The filtered sample is dried at 70°C for 8 h, and after drying, it is calcined in a muffle furnace at a heating rate of 2°C / min to 400°C for 4 h. The final product obtained is denoted as 20Fe-7Ba / CeO2.

[0036] Comparative Example 7: This comparative example provides an ammonia decomposition catalyst and a preparation method thereof The difference between this comparative example and Example 1 is as follows: In step (2), Ba(NO3)2 is not added. The specific preparation method of step (2) is as follows: Preparation of 20Ni / CeO2 catalyst (deposition precipitation method): Disperse 0.5 g of CeO2 nanosphere support in 25 mL of high-purity water, and ultrasonically stir it at room temperature to make it completely dispersed, denoted as solution A; Subsequently, measure 25.6 mL of 0.1 M Ni(NO3)2 solution into a 50 mL beaker, and denote it as solution B; Then, slowly add solution B dropwise to solution A, and simultaneously add 20 mL of 0.5 M Na2CO3 solution throughout the process to maintain the pH of the entire system at 9. After the addition is completed, stir the mixed solution at room temperature for 0.5 h and age for 1 h. Finally, perform suction filtration with 1 L of high-purity water. The filtered sample is dried at 70°C for 8 h, and after drying, it is calcined in a muffle furnace at a heating rate of 2°C / min to 400°C for 4 h. The final product obtained is denoted as 20Ni / CeO2.

[0037] Comparative Example 8: This comparative example provides an ammonia decomposition catalyst and a preparation method thereof The difference between this comparative example and Comparative Example 5 lies in that: in step (2), Ba(NO3)2 was not added. The specific preparation method of step (2) is as follows: Disperse 0.5 g of CeO2 nanosphere carrier in 25 mL of high-purity water, and ultrasonically stir it at room temperature to make it completely dispersed, denoted as solution A; Subsequently, measure 25.6 mL of 0.1 M Co(NO3)2 solution into a 50 mL beaker, and denote it as solution B; Then, add solution B dropwise to solution A, and simultaneously add 20 mL of 0.5 M Na2CO3 solution throughout the process to keep the pH of the whole system controlled at 9. After the addition is completed, stir the mixed solution at room temperature for 0.5 h and age it for 1 h. Finally, filter it with 1 L of high-purity water by suction filtration. The filtered sample is dried at 70 °C for 8 h, and after drying, it is calcined in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h. The final product obtained is denoted as 20Co / CeO2.

[0038] Comparative Example 9: This comparative example provides an ammonia decomposition catalyst and its preparation method The difference between this comparative example and Comparative Example 6 lies in that: in step (2), Ba(NO3)2 was not added. The specific preparation method of step (2) is as follows: Disperse 0.5 g of CeO2 nanosphere carrier in 25 mL of high-purity water, and ultrasonically stir it at room temperature to make it completely dispersed, denoted as solution A; Subsequently, measure 24.5 mL of 0.1 M Fe(NO3)3 solution into a 50 mL beaker, and denote it as solution B; Then, add solution B dropwise to solution A, and simultaneously add 20 mL of 0.5 M Na2CO3 solution throughout the process to keep the pH of the whole system controlled at 9. After the addition is completed, stir the mixed solution at room temperature for 0.5 h and age it for 1 h. Finally, filter it with 1 L of high-purity water by suction filtration. The filtered sample is dried at 70 °C for 8 h, and after drying, it is calcined in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h. The final product obtained is denoted as 20Fe / CeO2.

[0039] Comparative Example 10: This comparative example provides an ammonia decomposition catalyst and its preparation method The difference between this comparative example and Example 1 lies in that: in step (1), CeO2 nanorods were prepared, and the specific addition amount was the same as that of the CeO2 nanosphere support in Example 1. The contents of other components and the preparation method were the same as those in Example 1. The specific preparation method is as follows: Dissolve 14.4 g of NaOH in 40 mL of deionized water, then add an aqueous solution of 3 mmol of Ce(NO3)3·6H2O to the NaOH solution, and stir for 30 min to make the solution disperse evenly. Carry out hydrothermal reaction at 100 °C for 24 h, then transfer the obtained mixed solution to a polytetrafluoroethylene inner liner, and place the inner liner in a stainless steel reaction kettle. Set the temperature in the oven to 100 °C and react for 24 h. After the hydrothermal reaction, the obtained product was centrifuged and washed, washed 4 times with deionized water and 1 time with absolute ethanol respectively. After the washing was completed, the precipitate was placed in the oven and dried at 60 °C for 24 h to obtain CeO2 nanorods, denoted as CeO2-NR.

[0040] Disperse 0.5 g of the CeO2 nanorod support in 25 mL of high-purity water and ultrasonically stir it at room temperature to make it completely disperse, denoted as solution A; subsequently, measure 25.6 mL of 0.1 M Ni(NO3)2 solution into a 50 mL beaker (the 0.1 M Ni(NO3)2 solution was prepared by dissolving 2.91 g of Ni(NO3)2·6H2O in 100 mL of high-purity water), then weigh 0.13 g of Ba(NO3)2 and add it to the beaker containing the Ni(NO3)2 solution, and ultrasonically stir and mix them at room temperature, denoted as solution B; then add solution B dropwise to solution A, and simultaneously add 20 mL of 0.5 M Na2CO3 solution throughout the process to keep the pH of the whole system controlled at 9. After the addition was completed, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, filter it with 1 L of high-purity water by suction filtration, and the filtered sample was dried at 70 °C for 8 h. After drying, it was calcined in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h, and the final product obtained was denoted as 20Ni-7Ba / CeO2-NR.

[0041] Comparative Example 11: This comparative example provides an ammonia decomposition catalyst and its preparation method The difference between this comparative example and Example 1 is as follows: In step (1), CeO2 nanosheets were prepared. The specific addition amount was the same as that of the CeO2 nanosphere carrier in Example 1, and the contents of other components and the preparation method were the same as those in Example 1. The specific preparation method is as follows: The CeO2 nanosheet carrier was prepared by the co-precipitation method. 1.39 g of Ce(NO3)3·6H2O and 0.75 g of NH4HCO3 were respectively added to 200 mL of deionized water, and magnetic stirring was carried out at 0 °C until they were completely dissolved. The dissolved NH4HCO3 solution was quickly added to the Ce(NO3)3 solution, and stirring was carried out for 0.5 h. Subsequently, it was left standing at 0 °C for 15 h and then subjected to suction filtration and washing. The product after suction filtration was dried at 110 °C for 6 h. Finally, the dried solid was ground into powder and calcined at 450 °C for 4 h to obtain the required CeO2 nanosheet carrier, denoted as CeO2-NS.

[0042] 0.5 g of the CeO2 nanosheet carrier was dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature until it was completely dispersed, denoted as solution A; subsequently, 25.6 mL of 0.1 M Ni(NO3)2 solution was measured into a 50 mL beaker (the 0.1 M Ni(NO3)2 solution was prepared by dissolving 2.91 g of Ni(NO3)2·6H2O in 100 mL of high-purity water). Subsequently, 0.13 g of Ba(NO3)2 was weighed and added to the beaker containing the Ni(NO3)2 solution, and it was ultrasonically stirred and stirred at room temperature to make the two fully mixed, denoted as solution B; then solution B was added dropwise to solution A, and 20 mL of 0.5 M Na2CO3 solution was simultaneously added dropwise throughout the process to maintain the pH of the entire system at 9. After the addition was completed, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, suction filtration was carried out with 1 L of high-purity water, and the filtered sample was dried at 70 °C for 8 h. After drying, it was calcined in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h, and the final product obtained was denoted as 20Ni-7Ba / CeO2-NS.

[0043] Comparative Example 12: This comparative example provides an ammonia decomposition catalyst and a preparation method thereof The difference between this comparative example and Example 1 is that BaCeO3 was first prepared by the sol-gel method and then reacted with Ni(NO3)2 to prepare the catalyst. The specific preparation method is as follows: 0.784 g of Ba(NO3)2 and 1.302 g of Ce(NO3)3·6H2O were dissolved in 15 mL of high-purity water and stirred to form a mixed solution with a total cation concentration of 0.4 M, Ba 2+ and Ce 3+The molar ratio is 1:1. Then, 1.153 g of citric acid (Sigma-Aldrich, purity ≥99.5%) was added under continuous stirring to make the molar ratio of total cations to citric acid reach 1:1. The mixed solution was heated and stirred at 90 °C until a gel was formed, and then the gel was dried in an oven at 110 °C for 12 h. The dried expanded solid was ground into a powder and calcined in a muffle furnace at 1000 °C for 4 h to obtain the desired BaCeO3 support.

[0044] 0.5 g of the BaCeO3 support was dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature until completely dispersed, denoted as solution A; subsequently, 25.6 mL of 0.1 M Ni(NO3)2 solution was measured into a 50 mL beaker and denoted as solution B; then solution B was added dropwise to solution A, and 20 mL of 0.5 M Na2CO3 solution was added dropwise throughout the process to maintain the pH of the entire system at 9. After the addition was completed, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, suction filtration was carried out with 1 L of high-purity water, and the filtered sample was dried in an oven at 70 °C for 8 h. After drying, it was calcined in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h, and the final product obtained was denoted as 20Ni / BaCeO3-1.

[0045] Comparative Example 13: This comparative example provides an ammonia decomposition catalyst and its preparation method. The difference between this comparative example and Example 1 is that 20Ni-BaCeO3-2 was prepared in one step by the co-precipitation method. The specific preparation method is as follows: 0.52 g of Ba(NO3)2, 0.87 g of Ce(NO3)3·6H2O, and 0.81 g of Ni(NO3)2 were dissolved in 25 mL of high-purity water and stirred until completely dissolved, denoted as solution A. At the same time, 2.41 g of (NH4)2C2O4·H2O was dissolved in 54 mL of high-purity water and stirred until completely dissolved, denoted as solution B. Subsequently, under continuous stirring, solution A was slowly added to solution B and stirred for 4 h. After stirring, it was centrifuged and washed, and the centrifuged product was dried in an oven at 85 °C for 12 h. Then the dried solid was ground into a powder and calcined at 800 °C for 6 h to obtain the required 20Ni-BaCeO3-2.

[0046] Comparative Example 14: This comparative example provides an ammonia decomposition catalyst and its preparation method. The difference between this comparative example and Example 1 is that in step (2), BaCeO was prepared by the sol-gel method. 3，Then it is ball-milled and mixed with the CeO2 nanosphere support, and the mixed support is reacted with Ni(NO3)2 to prepare the 20Ni / BaCeO3-CeO2 catalyst. The specific preparation method is as follows: 0.784 g of Ba(NO3)2 and 1.302 g of Ce(NO3)3·6H2O are dissolved in 15 mL of high-purity water and stirred to form a mixed solution with a total cation concentration of 0.4 M. The molar ratio of Ba 2+ to Ce 3+ is 1:1. Then, 1.153 g of citric acid (Sigma-Aldrich, purity ≥99.5%) is added under continuous stirring to make the molar ratio of the total cations to citric acid reach 1:1. The mixed solution is heated and stirred at 90 °C until a gel is formed, and then the gel is dried in an oven at 110 °C for 12 h. The dried expanded solid is ground into a powder and calcined in a muffle furnace at 1000 °C for 4 h to obtain the required BaCeO3 support.

[0047] 0.0768 g of BaCeO3 and 0.5 g of CeO2 nanosphere support are mechanically ball-milled in a planetary ball mill at a rotation speed of 400 r for 2 h. The obtained mixed support is heated in a muffle furnace to 400 °C at a heating rate of 2 °C / min and calcined for 1 h. The obtained calcined support is named the BaCeO3-CeO2 support.

[0048] 0.5 g of the BaCeO3-CeO2 support is dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature to make it completely dispersed, denoted as solution A; subsequently, 25.6 mL of 0.1 M Ni(NO3)2 solution is measured into a 50 mL beaker and denoted as solution B; then solution B is added dropwise to solution A, and 20 mL of 0.5 M Na2CO3 solution is added dropwise throughout the process to keep the pH of the whole system controlled at 9. After the addition is completed, the mixed solution is stirred at room temperature for 0.5 h and aged for 1 h. Finally, it is filtered with 1 L of high-purity water, and the filtered sample is dried at 70 °C for 8 h. After drying, it is heated in a muffle furnace to 400 °C at a heating rate of 2 °C / min and calcined for 4 h. The obtained final product is denoted as 20Ni / BaCeO3-CeO2.

[0049] Comparative Example 15: This comparative example provides an ammonia decomposition catalyst and its preparation method. The difference between this comparative example and Comparative Example 7 is that different rare earth oxide supports (Y2O3 nanosheets) and corresponding catalysts are prepared. The specific preparation method is as follows: (1) Preparation of Y2O3 nanosheet support (hydrothermal method): Dissolve 1.15 g of Y(NO3)3·6H2O in 60 mL of deionized water, and then adjust the pH to 12 with NaOH solution. Continue to stir for 15 min to make the solution well mixed, and then carry out hydrothermal reaction at 120 °C for 12 h. The resulting precipitate is centrifuged and washed, and then dried at 60 °C for 12 h. The dried powder sample is ground and then calcined in a tubular furnace at 500 °C in air for 6 h to obtain a white Y2O3 nanosheet support.

[0050] (2) Preparation of 20Ni / Y2O3 catalyst: Disperse 0.5 g of Y2O3 support in 25 mL of high-purity water and ultrasonically stir it at room temperature to make it completely dispersed, denoted as solution A; subsequently, measure 25.6 mL of 0.1 M Ni(NO3)2 solution into a 50 mL beaker, denoted as solution B; then add solution B dropwise to solution A, and simultaneously add 20 mL of 0.5 M Na2CO3 solution throughout the process to maintain the pH of the whole system at 9. After the addition is completed, stir the mixed solution at room temperature for 0.5 h and age it for 1 h. Finally, filter it with 1 L of high-purity water by suction filtration, and the filtered sample is dried at 70 °C for 8 h. After drying, it is calcined in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h, and the final product obtained is denoted as 20Ni / Y2O3.

[0051] Comparative Example 16: This comparative example provides an ammonia decomposition catalyst and its preparation method. The difference between this comparative example and Comparative Example 7 is that different rare earth oxide supports (Sm2O3 nanorods) and corresponding catalysts are prepared. The specific preparation method is as follows: (1) Preparation of Sm2O3 nanorod support (hydrothermal method): Dissolve 14.4 g of NaOH in 40 mL of deionized water, and then add an aqueous solution of 3 mmol of Sm(NO3)3·6H2O to the previous NaOH solution, and stir for 30 min to make it well mixed. Subsequently, carry out hydrothermal reaction at 100 °C for 24 h. The resulting precipitate is centrifuged and washed, and then dried at 60 °C for 12 h. The dried powder sample is ground and then calcined in a tubular furnace at 450 °C in air for 4 h to obtain Sm2O3 nanorod support.

[0052] (2)Preparation of 20Ni / Sm2O3 catalyst: 0.5 g of Sm2O3 support was dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature until completely dispersed, denoted as solution A; subsequently, 25.6 mL of 0.1 M Ni(NO3)2 solution was measured into a 50 mL beaker and denoted as solution B; then solution B was added dropwise to solution A, and 20 mL of 0.5 M Na2CO3 solution was added dropwise throughout the process to maintain the pH of the whole system at 9. After the addition was completed, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, it was filtered by suction with 1 L of high-purity water, and the filtered sample was dried at 70 °C for 8 h. After drying, it was calcined in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h, and the final product obtained was denoted as 20Ni / Sm2O3.

[0053] Comparative Example 17: This comparative example provides an ammonia decomposition catalyst and its preparation method The difference between this comparative example and Comparative Example 7 is that different rare earth oxide supports (Gd2O3 nanorods) and corresponding catalysts were prepared. The specific preparation method is as follows: (1)Preparation of Gd2O3 nanosheet support (hydrothermal method): 0.02 mmol of Gd(NO3)3·6H2O was dissolved in 60 mL of deionized water, and then the pH value was adjusted to 12.8 using 2.5 M NaOH solution. Subsequently, a hydrothermal reaction was carried out at 180 °C for 24 h, and the resulting precipitate was centrifuged and washed and then dried at 80 °C for 12 h. The dried sample was ground and then calcined in a tubular furnace at 450 °C for 2 h to obtain a white Gd2O3 nanorod support.

[0054] (2)Preparation of 20Ni / Gd2O3 catalyst: 0.5 g of Gd2O3 support was dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature until completely dispersed, denoted as solution A; subsequently, 25.6 mL of 0.1 M Ni(NO3)2 solution was measured into a 50 mL beaker and denoted as solution B; then solution B was added dropwise to solution A, and 20 mL of 0.5 M Na2CO3 solution was added dropwise throughout the process to maintain the pH of the whole system at 9. After the addition was completed, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, it was filtered by suction with 1 L of high-purity water, and the filtered sample was dried at 70 °C for 8 h. After drying, it was calcined in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h, and the final product obtained was denoted as 20Ni / Gd2O3.

[0055] Comparative Example 18: This comparative example provides an ammonia decomposition catalyst and its preparation method The difference between this comparative example and Comparative Example 7 is that an inert oxide carrier (SiO2) is added for the preparation of the catalyst. The specific preparation method is as follows: Preparation of 20Ni / SiO2 catalyst: Disperse 0.5 g of SiO2 carrier in 25 mL of high-purity water, and ultrasonically stir it at room temperature until it is completely dispersed, denoted as Solution A; then measure 25.6 mL of 0.1 M Ni(NO3)2 solution into a 50 mL beaker, and denote it as Solution B; then gradually add Solution B dropwise to Solution A, and simultaneously add 20 mL of 0.5 M Na2CO3 solution throughout the process to maintain the pH of the whole system at 9. After the addition is completed, stir the mixed solution at room temperature for 0.5 h and age it for 1 h. Finally, filter it with 1 L of high-purity water by suction filtration. The filtered sample is dried at 70 °C for 8 h, and after drying, it is calcined in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h. The final product obtained is denoted as 20Ni / SiO2.

[0056] Comparative Example 19: This comparative example provides an ammonia decomposition catalyst and its preparation method The difference between this comparative example and Comparative Example 7 is that an inert oxide carrier (Al2O3) is added for the preparation of the catalyst. The specific preparation method is as follows: Preparation of 20Ni / Al2O3 catalyst: Disperse 0.5 g of Al2O3 carrier in 25 mL of high-purity water, and ultrasonically stir it at room temperature until it is completely dispersed, denoted as Solution A; then measure 25.6 mL of 0.1 M Ni(NO3)2 solution into a 50 mL beaker, and denote it as Solution B; then gradually add Solution B dropwise to Solution A, and simultaneously add 20 mL of 0.5 M Na2CO3 solution throughout the process to maintain the pH of the whole system at 9. After the addition is completed, stir the mixed solution at room temperature for 0.5 h and age it for 1 h. Finally, filter it with 1 L of high-purity water by suction filtration. The filtered sample is dried at 70 °C for 8 h, and after drying, it is calcined in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h. The final product obtained is denoted as 20Ni / Al2O3.

[0057] Comparative Example 20: This comparative example provides an ammonia decomposition catalyst and its preparation method The difference between this comparative example and Example 7 is that in step (2), Y2O3 nanosheet carrier (the carrier preparation method is as shown in Comparative Example 9) is added. The specific preparation method of the ammonia decomposition catalyst is as follows: Preparation of 20Ni-7Ba / Y2O3 catalyst (deposition precipitation method): 0.5 g of Y2O3 nanosheet support was dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature until it was completely dispersed, denoted as solution A; subsequently, 25.6 mL of 0.1 M Ni(NO3)2 solution was measured into a 50 mL beaker, and then 0.13 g of Ba(NO3)2 was weighed and added to the beaker containing Ni(NO3)2 solution, and it was ultrasonically stirred at room temperature to make the two fully mixed, denoted as solution B; then solution B was added dropwise to solution A, and 20 mL of 0.5 M Na2CO3 solution was added dropwise throughout the process to maintain the pH of the whole system at 9. After the addition was completed, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, it was filtered by suction with 1 L of high-purity water, and the filtered sample was dried at 70 °C for 8 h. After drying, it was calcined in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h, and the final product obtained was denoted as 20Ni-7Ba / Y2O3.

[0058] Comparative Example 21: This comparative example provides an ammonia decomposition catalyst and its preparation method The difference between this comparative example and Example 1 is that in step (2), Sm2O3 nanorod support was added (the preparation method of the support is as shown in Comparative Example 10), and the specific preparation method of the ammonia decomposition catalyst is as follows: Preparation of 20Ni-7Ba / Sm2O3 catalyst (deposition precipitation method): 0.5 g of Sm2O3 nanorod support was dispersed in 25 mL of high-purity water and ultrasonically stirred at room temperature until it was completely dispersed, denoted as solution A; subsequently, 25.6 mL of 0.1 M Ni(NO3)2 solution was measured into a 50 mL beaker, and then 0.13 g of Ba(NO3)2 was weighed and added to the beaker containing Ni(NO3)2 solution, and it was ultrasonically stirred at room temperature to make the two fully mixed, denoted as solution B; then solution B was added dropwise to solution A, and 20 mL of 0.5 M Na2CO3 solution was added dropwise throughout the process to maintain the pH of the whole system at 9. After the addition was completed, the mixed solution was stirred at room temperature for 0.5 h and aged for 1 h. Finally, it was filtered by suction with 1 L of high-purity water, and the filtered sample was dried at 70 °C for 8 h. After drying, it was calcined in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h, and the final product obtained was denoted as 20Ni-7Ba / Sm2O3.

[0059] Comparative Example 22: This comparative example provides an ammonia decomposition catalyst and its preparation method The difference between this comparative example and Example 1 lies in that: in step (2), the added carrier is Gd2O3 nanorods (the preparation method of the carrier is as shown in Comparative Example 11), and the specific preparation method of the ammonia decomposition catalyst is as follows: Preparation of 20Ni-7Ba / Gd2O3 catalyst (deposition-precipitation method): Disperse 0.5 g of Gd2O3 nanorod carrier in 25 mL of high-purity water, and ultrasonically stir it at room temperature to make it completely dispersed, denoted as solution A; then measure 25.6 mL of 0.1M Ni(NO3)2 solution into a 50 mL beaker, and then weigh 0.13 g of Ba(NO3)2 and add it to the beaker containing Ni(NO3)2 solution, and ultrasonically stir and mix them at room temperature, denoted as solution B; then add solution B dropwise to solution A, and simultaneously add 20 mL of 0.5 M Na2CO3 solution throughout the process to keep the pH of the whole system controlled at 9. After the addition is completed, stir the mixed solution at room temperature for 0.5 h and age it for 1 h. Finally, filter it with 1 L of high-purity water by suction filtration, dry the filtered sample at 70 °C for 8 h, and after drying, calcine it in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h, and the final product obtained is denoted as 20Ni-7Ba / Gd2O3.

[0060] Comparative Example 23: This comparative example provides an ammonia decomposition catalyst and its preparation method The difference between this comparative example and Example 1 lies in that: in step (2), the added carrier is SiO2, and the specific preparation method of the ammonia decomposition catalyst is as follows: Preparation of 20Ni-7Ba / SiO2 catalyst (deposition-precipitation method): Disperse 0.5 g of SiO2 carrier in 25 mL of high-purity water, and ultrasonically stir it at room temperature to make it completely dispersed, denoted as solution A; then measure 25.6 mL of 0.1 M Ni(NO3)2 solution into a 50 mL beaker, and then weigh 0.13 g of Ba(NO3)2 and add it to the beaker containing Ni(NO3)2 solution, and ultrasonically stir and mix them at room temperature, denoted as solution B; then add solution B dropwise to solution A, and simultaneously add 20 mL of 0.5 M Na2CO3 solution throughout the process to keep the pH of the whole system controlled at 9. After the addition is completed, stir the mixed solution at room temperature for 0.5 h and age it for 1 h. Finally, filter it with 1 L of high-purity water by suction filtration, dry the filtered sample at 70 °C for 8 h, and after drying, calcine it in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h, and the final product obtained is denoted as 20Ni-7Ba / SiO2.

[0061] Comparative Example 24: This comparative example provides an ammonia decomposition catalyst and a preparation method thereof. The difference between this comparative example and Example 1 lies in that: in step (2), the added carrier is Al2O3. The specific preparation method of the ammonia decomposition catalyst is as follows: Preparation of 20Ni-7Ba / Al2O3 catalyst (deposition-precipitation method): Disperse 0.5 g of Al2O3 carrier in 25 mL of high-purity water and ultrasonically stir it at room temperature to make it completely dispersed, denoted as solution A; then measure 25.6 mL of 0.1 M Ni(NO3)2 solution into a 50 mL beaker, then weigh 0.13 g of Ba(NO3)2 and add it to the beaker containing Ni(NO3)2 solution, and ultrasonically stir and mix them at room temperature, denoted as solution B; then slowly add solution B dropwise to solution A, and simultaneously add 20 mL of 0.5 M Na2CO3 solution throughout the process to maintain the pH of the whole system at 9. After the addition is completed, stir the mixed solution at room temperature for 0.5 h and age it for 1 h. Finally, perform suction filtration with 1 L of high-purity water, and dry the filtered sample at 70 °C for 8 h. After drying, calcine it in a muffle furnace at a heating rate of 2 °C / min to 400 °C for 4 h. The final product obtained is denoted as 20Ni-7Ba / Al2O3.

[0062] Experimental Example 1: In this experimental example, the structural characteristics of the ammonia decomposition catalysts prepared in Example 1, Comparative Example 5, Comparative Example 7, and Comparative Example 10 were tested. As Figure 1 shown, the TEM image of 20Ni-7Ba / CeO2 prepared in Example 1 shows that the catalyst presents a nanosphere structure with a size in the range of 60 - 70 nm.

[0063] The inventor further explored the difference between single carrier CeO2 nanorods and single carrier CeO2 nanospheres, and performed N2 adsorption-desorption tests on both of them. Table 1 summarizes their physical properties, including specific surface area ( S BET ), pore volume ( V total ), and BJH pore size.

[0064] Table 1

[0065] Judging from the specific surface areas of different carriers in Table 1, the specific surface area of the CeO2 nanosphere carrier is larger. A carrier with a large specific surface area can disperse the active metal more uniformly, reduce particle agglomeration, increase the exposure number of active sites, and thus is beneficial to the progress of the ammonia decomposition reaction.

[0066] As Figure 2 shown, the refined XRD images of the 20Ni-7Ba / CeO2 catalyst prepared in Example 1 and the 20Co-7Ba / CeO2 catalyst prepared in Comparative Example 5 show that in the refined XRD after the reaction of 20Ni-7Ba / CeO2, in addition to the weak diffraction peak of BaCO3, the presence of a new species of BaCeO3 was also observed. In the XRD after the reaction of 20Co-7Ba / CeO2, only the presence of the BaO species was observed, and the generation of this new species was not observed.

[0067] As Figure 3 shown, the H2 reaction order of 20Ni / CeO2 prepared in Comparative Example 7 and 20Ni-7Ba / CeO2 prepared in Example 1 shows that compared with the 20Ni / CeO2 catalyst, the absolute value of the H2 reaction order of the 20Ni-7Ba / CeO2 catalyst with in-situ generated BaCeO3 as an additive is smaller, indicating that it has more excellent anti-hydrogen poisoning ability.

[0068] As Figure 4 shown, the Ni2 p XPS spectra of 20Ni / CeO2 prepared in Comparative Example 7 and 20Ni-7Ba / CeO2 prepared in Example 1 show that from the Ni 2 p energy spectrum, it is found that the binding energy of metallic Ni in 20Ni-7Ba / CeO2 is lower. Combining the high basicity and excellent electron transport ability of the BaCeO3 surface, it shows that the formation of BaCeO3 leads to an increase in the electron cloud density of Ni on the surface of 20Ni-7Ba / CeO2, which is beneficial to the ammonia decomposition reaction.

[0069] As Figure 5 shown, the CO2 temperature-programmed desorption experiment CO2-TPD of 20Ni / CeO2 prepared in Comparative Example 7 and 20Ni-7Ba / CeO2 prepared in Example 1 shows that due to the generation of BaCeO3, there are more medium-strong basic sites on the surface of 20Ni-7Ba / CeO2, which is beneficial to promoting the transfer of electrons to the active metal, in line with the results of quasi-in-situ XPS, which is beneficial to promoting the associative desorption of the product N2 and promoting the ammonia decomposition reaction.

[0070] Test Example 1: In this test example, the catalytic performance (ammonia decomposition activity at low temperature) of the ammonia decomposition catalysts prepared in Examples 1 to 13 and Comparative Examples 1 to 18 was measured. Experimental procedure: In the performance test of the catalyst, 50 mg of the ammonia decomposition catalysts (20 - 40 mesh) prepared in the above-mentioned examples and comparative examples were respectively mixed with 500 mg of quartz sand (20 - 40 mesh), and then loaded into a quartz reaction tube with an inner diameter of 8 mm. Before the catalytic test, the catalyst was first activated at 600 °C for 1 h in a pure NH3 atmosphere, and then the ammonia decomposition conversion rate was tested between 450 - 600 °C. The conversion rate data at each 50 °C interval was collected (GHSV = 30,000mL·gcat- 1 ·h -1 , where GHSV is the abbreviation of Gas Hourly Space Velocity, which refers to the gas hourly space velocity). The outlet gas was analyzed by an on-line gas chromatograph (Fuli GC 9790) to obtain the real-time contents of N2 and NH3. The conversion rate of NH3 was calculated by the following formula:

[0071] where, is the concentration of N2 at the chromatographic outlet generated, is the concentration of unreacted NH3 at the chromatographic outlet.

[0072] The test results are shown in Tables 2 and 3 (numerical tests at 500 °C): Table 2

[0073] Table 3

[0074] As can be seen from the data in Table 2, when the Ni loading is 20% and the introduced Ba content is 7%, its ammonia decomposition activity is the best, and the conversion rate can reach 86.3% at 500 °C. Reducing the Ba content will lead to a decrease in activity, which may be due to the limited content of in-situ formed BaCeO3 when the Ba content is low, resulting in limited promotion of activity.

[0075] As can be seen from the data in Table 3, compared with Ni-based catalysts with other oxide supports, the activity of Ni-based catalysts doped with Ba is lower than that of the 20Ni-7Ba / CeO2 catalyst with in-situ formed BaCeO3; when the type of active metal is changed, the activity of the catalyst doped with Ba is also significantly lower than that of Ni-based catalysts; for the 20Ni-7Ba / CeO2 catalyst with the best activity, when the Ni content is further increased to 25%, its activity and hydrogen production rate per gram of catalyst not only do not increase compared with Example 1, but instead decrease, which may be due to the fact that too high Ni content leads to easy sintering of the active metal; its activity and hydrogen production rate per gram of catalyst are higher than those of Examples 2 and 3, which may be because the number of active sites increases after the Ni content is increased; for Comparative Example 3, the hydrogen production rate per gram of metal is higher than those of Comparative Examples 2 and 3 because the Ni content is reduced, but the ammonia conversion rate after catalysis is lower than that of the examples.

[0076] When the Ba content is further increased, it will also lead to a decrease in activity, which may be because the increase in its content may cover some active sites. In addition, the activity of the 20Ni-7Ba / CeO2 catalyst with in-situ formed BaCeO3 is higher than that of the related catalysts doped with BaCeO3 non-in-situ, which further illustrates the importance of in-situ formation of BaCeO3. In addition, compared with CeO2 nanosheets and CeO2 nanorods, the 20Ni-7Ba / CeO2 catalyst with CeO2 nanospheres as the support has more excellent ammonia decomposition conversion rate and hydrogen production rate, which may be due to the larger specific surface area of the CeO2 nanosphere support and the more dispersed active metal.

[0077] As can be seen from the comprehensive analysis of the data in Table 2 and Table 3, the 20Ni-7Ba / CeO2 catalyst with in-situ formed BaCeO3 has the best ammonia decomposition conversion rate, and its hydrogen production rate can reach 28.8 mmol·g cat −1 ·min −1 。

[0078] Test Example 2: In this test example, a long-term stability test was carried out on the 20Ni-7Ba / CeO2 catalyst prepared in Example 1. Experimental procedure: Long-term stability tests were carried out in a vertical fixed-bed reactor. 25 mg of the ammonia decomposition catalysts (20 - 40 mesh) prepared in the above-mentioned examples and comparative examples were respectively mixed with 500 mg of quartz sand (20 - 40 mesh), and then loaded into a quartz reaction tube with an inner diameter of 8 mm. Before the formal catalytic test, the catalyst was first activated at 600 °C for 1 h in a pure NH3 atmosphere (25 mL / min), and then cooled to 550 °C for a 100-h stability test, and then further cooled to 500 °C for a 100-h stability test (GHSV = 60,000 mL·g cat -1 ·h -1 , where GHSV is the abbreviation of Gas Hourly SpaceVelocity, referring to the gas hourly space velocity).

[0079] The test results are as Figure 6 shown. During the 100-h stability tests at 550 °C and 500 °C respectively, the activity of 20Ni-7Ba / CeO2 prepared in Example 1 of the present invention only decreased by about 3% (from 95.1% to 91.3% at 550 °C in 100 h of stability, and from 51.2% to 47.5% at 500 °C in 100 h of stability), showing excellent stability.

[0080] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An ammonia decomposition catalyst with in-situ formed BaCeO3 as an additive, characterized in that, The ammonia decomposition catalyst includes a rare earth oxide support CeO2, an active component nickel compound supported on the support, and an alkaline earth metal promoter barium compound; wherein, the loading amount of nickel in the active component nickel compound is 15-25 wt.%, the loading amount of barium in the alkaline earth metal promoter barium compound is 1-15 wt.%, and the alkaline earth metal promoter barium compound reacts with the rare earth oxide support in situ during the ammonia decomposition reaction to form a BaCeO3 perovskite structure.

2. The ammonia decomposition catalyst using in-situ formed BaCeO3 as an auxiliary agent according to claim 1, wherein The active component nickel compound is NiO, and the alkaline earth metal promoter barium compound is BaCO3.

3. The ammonia decomposition catalyst using in-situ formed BaCeO3 as an auxiliary agent as described in claim 1, characterized in that, The morphology of the ammonia decomposition catalyst is a nanosphere structure, with a size of 60-70 nm, a specific surface area of 130-135 m 2 / g, a pore volume of 0.3-0.35 cm 3 / g, and a pore size of 4.5-4.7 nm; The particle size of the ammonia decomposition catalyst is 20-40 mesh.

4. A method for preparing an ammonia decomposition catalyst using in-situ formed BaCeO3 as an auxiliary agent according to any one of claims 1 to 3, characterized in that, It includes the following steps: S1. Dissolve a cerium salt in a mixed solvent, conduct a solvothermal reaction, and calcine the precipitate obtained after centrifugal washing of the product to obtain a CeO2 nanosphere support; S2. Drop the mixed solution obtained by adding a barium salt to a nickel salt solution into an aqueous solution of the CeO2 nanosphere support, and at the same time drop a sodium salt solution, adjust the pH to 8-10, and then obtain the ammonia decomposition catalyst after aging, suction filtration, drying, and calcination in sequence.

5. The preparation method according to claim 4, wherein In step S1, the mixed solvent is a mixed solution of water, ethylene glycol, and glacial acetic acid, the volume ratio of water, ethylene glycol to glacial acetic acid is (1.5~2.5):(50~55):(1.5~2.5), and the concentration of glacial acetic acid ≥99.5%; the dosage ratio of the cerium salt to the mixed solvent is 1 g:(25~30) mL; the cerium salt includes cerium nitrate hexahydrate.

6. The preparation method according to claim 4, characterized in that, In step S1, the temperature of the solvothermal reaction is 170~190 °C, and the reaction time is 180~240 min; the calcination treatment is to heat up to 350~450 °C at a heating rate of 1~3 °C / min and calcine for 0.5~1.5 h.

7. The preparation method according to claim 4, characterized in that, In step S2, the barium salt includes barium nitrate, the nickel salt includes nickel nitrate, and the sodium salt includes sodium carbonate; the concentration of the nickel salt solution is 0.08~0.12 M; the concentration of the sodium salt is 0.4~0.6 M; the dosage ratio of the barium salt, nickel salt solution to the sodium salt solution is (0.1~0.15) g:(25~26) mL:(20~30) mL.

8. The preparation method according to claim 4, characterized in that, In step S2, the pH is 9; the aging time is 1~1.5 h; the drying temperature is 65~75 °C, and the time is 7~9 h; the calcination is to heat up to 350~450 °C at a heating rate of 1~3 °C / min, and the calcination time is 3~5 h.

9. Application of the ammonia decomposition catalyst with in-situ formed BaCeO3 as a promoter according to any one of claims 1~3 in the ammonia decomposition to hydrogen reaction.

10. The application according to claim 9, characterized in that, The ammonia decomposition catalyst is activated in a pure ammonia atmosphere at 600 °C for 0.5~1.5 h to reduce NiO to metallic nickel, and at the same time, Ba species react with the support CeO2 to form BaCeO3.

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