A supported metal catalyst coupled with porous materials, its preparation method, and its application in low-temperature plasma ammonia synthesis.

Abstract

This invention relates to a supported metal catalyst coupled with a porous material, its preparation method, and its application in low-temperature plasma ammonia synthesis, belonging to the field of catalyst technology. The method involves first preparing a cerium oxide nanoisland support, then preparing a copper-iron alloy-cerium oxide nanoisland catalyst, which is then mixed with a mesoporous material and calcined to prepare a metal catalyst coupled with a porous material. The porous material prepared by this invention can significantly improve the efficiency of low-temperature plasma ammonia synthesis, especially Cu4Fe1-CeO. x The porous material synthesized using the SiO2 catalyst exhibits extremely high catalytic activity in plasma ammonia synthesis systems and can be used stably at high power. When operating at 65W, it achieved the highest ammonia outlet concentration of 44386 ppm in the field of plasma ammonia synthesis. Furthermore, this invention does not use precious metals, significantly reducing the production cost of the catalyst and further promoting the practical application of low-temperature plasma ammonia synthesis reactions.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a supported metal catalyst coupled with porous materials, its preparation method, and its application in low-temperature plasma ammonia synthesis reaction. Background Technology

[0002] Ammonia is a crucial raw material for fertilizer production and also a renewable energy storage and transportation medium with immense development potential. Ammonia (NH3) possesses numerous advantages, including high hydrogen content (approximately 17.7%), zero carbon emissions, and convenient storage and transportation, making it widely considered one of the most ideal hydrogen fuel media. Industrial ammonia synthesis primarily utilizes the Haber-Bosch process, which employs an iron-based catalyst to react N2 and H2 molecules to produce NH3 under high temperature (approximately 400–600°C) and high pressure (approximately 20–40 MPa) conditions. Global annual ammonia production exceeds 150 million tons, while simultaneously emitting approximately 1.2% of global greenhouse gas emissions and consuming about 2% of global energy supply. Therefore, developing alternatives to the traditional Haber-Bosch ammonia synthesis process is an urgent and challenging task.

[0003] Plasma-catalyzed synthesis is an emerging hybrid technology that can effectively overcome the thermodynamic and kinetic limitations encountered in thermochemical reactions. The high-energy electrons and particles in plasma can induce molecular vibrations or electronic excitations, as well as electron impact dissociation, which is beneficial for the activation of inert N≡N bonds and for lowering the dissociation barrier. After N₂ is activated by plasma, it can form various reactive nitrogen species (Nr), such as N atoms, vibrationally or electronically excited N₂ molecules, or ions.

[0004] Studies have shown that combining low-temperature plasma technology with catalysts enables ammonia synthesis at low temperatures (400–500 K) and atmospheric pressure. The plasma-catalyzed ammonia synthesis process utilizing renewable electricity allows for ammonia production in non-localized locations and on a small scale, representing a potential alternative to thermocatalytic ammonia synthesis.

[0005] The introduction of plasma offers greater flexibility in materials and process development. Some materials not commonly used in traditional thermocatalysis, such as metal oxides, metal halides, transition metals, and metal-organic frameworks, can be used as catalysts for plasma ammonia synthesis. However, plasma-induced ammonia decomposition, the reverse reaction of ammonia synthesis, is considered a major obstacle to achieving efficient ammonia synthesis. This significantly limits the final yield and energy efficiency of the plasma ammonia synthesis process. Therefore, effectively circumventing this phenomenon and finding inexpensive and efficient catalysts have become primary issues in the field of plasma ammonia synthesis. Summary of the Invention

[0006] To achieve a highly efficient, green, and energy-efficient plasma ammonia synthesis process, this invention provides a supported metal catalyst coupled with porous materials, a preparation method, and its application in low-temperature plasma ammonia synthesis.

[0007] The preparation method of the supported metal catalyst coupled with porous material according to the present invention includes the following steps:

[0008] (1) Preparation of cerium oxide nanoisland carrier: Take 3-4 g of silicon dioxide and place it in 0.1-1 L of deionized water. Sonicate for 10-30 min to produce a homogeneous mixture solution. Dissolve 3-5 mmol of cerium salt in the mixture solution and quickly inject alkaline solution to adjust the pH value of the solution to 8-9. After vacuum filtration, dry at 50-70℃ for 10-15 h. Grind the obtained dry powder thoroughly and calcine at 400-800℃ for 5-12 h (heating rate maintained at 1-5℃ / min) to obtain cerium oxide nanoisland carrier, denoted as CeO. x / SiO2 support; wherein cerium oxide nano islands are clusters with a particle size of 2-3 nm, uniformly loaded on silicon dioxide;

[0009] In step (1), the silica is one or more of silica microspheres (particle size 20-200 nm) or amorphous silica; the cerium salt is one or more of cerium nitrate, cerium sulfate, cerium chloride, cerium oxalate, cerium carbonate, and cerium acetate; and the alkaline solution is one or more of sodium hydroxide solution, ammonia water, potassium hydroxide solution, and sodium carbonate solution.

[0010] (2) Preparation of copper-iron alloy-cerium oxide nanoisland catalyst: Weigh 1g of the cerium oxide nanoisland support dry powder obtained in step (1) and dissolve it in 20-100mL of deionized water. Sonicate the solution for 5-30min to produce a homogeneous mixture. Dissolve the iron salt and copper salt in 10-20mL of deionized water according to the stoichiometric ratio. Add the resulting solution containing copper and iron salts to the mixture and stir vigorously. Add alkali solution dropwise to adjust the pH of the mixture to 7.5-8.5, and then heat for 60-100min. The mixture was stirred at a constant temperature of 00℃ for 20–30 h. The resulting product was washed with deionized water and centrifuged 3–6 times at 6000–10000 r / min. Finally, it was dried at 110–130℃ for 10–15 h. The resulting dry powder was thoroughly ground and calcined at 400–800℃ for 2–6 h (heating rate maintained at 5℃ / min). The resulting dry powder was then calcined at 400–800℃ for 2–6 h in an atmosphere of 95% argon and 5% hydrogen to obtain Cu. y Fe 5-y -CeO x / SiO2 copper-iron alloy-cerium oxide nanoisland catalyst; y<5, x<2, CeO x Cu on SiO2 support yFe 5-y The loading rate is 3-8 wt%;

[0011] In step (2), the iron salt is one or more of ferric nitrate, ferric sulfate, ferric chloride, ferric phosphate, and ferric citrate; the copper salt is one or more of copper nitrate, copper chloride, and copper sulfate; and the alkaline solution is one or more of sodium hydroxide solution, ammonia water, potassium hydroxide solution, and sodium carbonate solution.

[0012] (3) Preparation of metal catalyst coupled with porous materials and ammonia synthesis reaction under plasma conditions: Strategy 1 (M1), 0.5g Cu y Fe 5-y -CeO x / SiO2 is mixed with 5g of mesoporous material (one of SBA-15, MCM-48, MCM-41, or KIT-6) to obtain a metal catalyst coupled porous material; Strategy 2 (M2) involves mixing 0.5g of Cu y Fe 5-y -CeO x / SiO2 catalyst and 5g mesoporous material are ground for 15-30 minutes to achieve micron-level uniform mixing. The resulting dry powder is pressed into tablets and sieved to 80-100 mesh to obtain a metal catalyst coupled with porous material, which is then filled into a dielectric barrier discharge quartz reactor; Strategy 3 (M3) involves adding 0.5g Cu y Fe 5-y -CeO x The SiO2 catalyst and 5g of mesoporous material were added to 180-220mL of aqueous solution and heated and stirred at 85-95℃ until the solution was completely dry. The resulting dry powder was dried overnight at 85-95℃ and then calcined at 500-600℃ for 2-5h (heating rate maintained at 5℃ / min) to achieve nanoscale uniform mixing. Finally, the calcined product was pressed into tablets and sieved to 80-100 mesh to obtain the metal catalyst coupled with porous material, which was then filled into a dielectric barrier discharge quartz reactor; then, ammonia synthesis reaction was carried out under plasma.

[0013] The supported metal catalyst Cu used in this invention y Fe 5-y The preparation method of SiO2 is as follows:

[0014] (1) Weigh 1g of silica (one or more of silica microspheres or amorphous silica with a particle size of 20-200nm) and dissolve it in 20-100mL of deionized water. Sonicate the solution for 5-30min to produce a homogeneous mixture. Dissolve iron and copper salts in 10-20mL of deionized water according to stoichiometric ratio. Add the resulting solution containing copper and iron salts to the mixture and stir vigorously. Adjust the pH of the mixture to 7.5-8.5 by adding alkali solution dropwise. Then, the mixture is stirred at a constant temperature of 60–100℃ for 20–30 h. The resulting product is washed with deionized water and centrifuged 3–6 times at 6000–10000 r / min. Finally, it is dried at 110–130℃ for 10–15 h. The resulting dry powder is then thoroughly ground and calcined at 400–800℃ for 2–6 h. The resulting dry powder is then calcined again at 400–800℃ for 2–6 h in an atmosphere of 95% argon and 5% hydrogen to obtain Cu. y Fe 5-y -SiO2 catalyst; y<5, Cu on SiO2 support y Fe 5-y The loading rate is 3-8 wt%;

[0015] (2) Preparation of metal catalyst coupled with porous materials and ammonia synthesis reaction under plasma conditions: Strategy 1 (M1), 0.5g Cu y Fe 5-y - SiO2 is mixed with 5g of mesoporous materials (SBA-15, MCM-48, MCM-41, KIT-6, etc.) to obtain a metal catalyst coupled with porous materials for low-temperature plasma ammonia synthesis; Strategy 2 (M2) involves mixing 0.5g of Cu y Fe 5-y - SiO2 catalyst and 5g mesoporous material are ground for 15-30 minutes to achieve micron-level uniform mixing. The resulting dry powder is pressed into tablets and sieved to 80-100 mesh to obtain a metal catalyst coupled with porous material. This material is then filled into a dielectric barrier discharge quartz reactor for low-temperature plasma ammonia synthesis. Strategy 3 (M3) involves adding 0.5g Cu y Fe 5-y - SiO2 catalyst and 5g of mesoporous material were added to 180-220mL of aqueous solution and heated and stirred at 85-95℃ until the solution was completely dry. The resulting dry powder was dried overnight at 85-95℃ and then calcined at 500-600℃ for 2-5h to achieve uniform mixing at the nanoscale. Finally, the calcined product was pressed into tablets and sieved to 80-100 mesh to obtain metal catalyst coupled porous material, which was filled into a dielectric barrier discharge quartz reactor for low-temperature plasma ammonia synthesis reaction.

[0016] The iron salt mentioned in the above steps is one or more of ferric nitrate, ferric sulfate, ferric chloride, ferric phosphate, and ferric citrate; the copper salt is one or more of copper nitrate, copper chloride, and copper sulfate; and the alkaline solution is one or more of sodium hydroxide solution, ammonia water, potassium hydroxide solution, and sodium carbonate solution.

[0017] The reaction conditions for low-temperature plasma ammonia synthesis were as follows: plasma discharge power of 35–65 W, plasma source frequency of 8–15 kHz, peak-to-peak voltage of 10–20 kV, nitrogen gas flow rate of 5–15 mL / min, and hydrogen gas flow rate of 15–45 mL / min. The amount of ammonia produced was determined by colorimetric titration, among which strategy 3 (M3) showed the highest catalytic activity.

[0018] The supported metal catalyst coupled with porous materials prepared in this invention can significantly improve the efficiency of low-temperature plasma ammonia synthesis reaction, especially Cu4Fe1-CeO. x The supported metal catalyst coupled with porous materials synthesized using SiO2 catalysts exhibits extremely high catalytic activity in plasma ammonia synthesis systems and can be used stably at high power (it operated stably for 120 hours at 35W without a significant decrease in performance). The supported metal catalyst coupled with porous materials in the ammonia synthesis reaction shows a distance-dependent effect; the closer the supported metal catalyst is to the porous material, the higher the conversion rate. Experimental results show that this strategy brings significant performance improvements at different power levels, especially at high power (65W), achieving the highest ammonia outlet concentration of 44386 ppm in the field of plasma ammonia synthesis. Furthermore, the catalyst preparation does not use precious metals, greatly reducing production costs and further promoting the practical application of low-temperature plasma ammonia synthesis. Attached Figure Description

[0019] Figure 1 Cu4Fe1-SiO2 and Cu4Fe1-CeO x X-ray diffraction (XRD) pattern of SiO2; in Cu4Fe1-CeO x In SiO2, the X-ray diffraction (XRD) peaks of calcined silica-supported cerium oxide nanoislands showed a cubic fluorite structure, consistent with the diffraction peaks of the standard card CeO2 (PDF#43-1022), but with poorer crystallinity and lower peak intensity. The Cu4Fe1-SiO2 sample exhibited distinct characteristic diffraction peaks at 43.28° and 50.40°, consistent with the standard card Cu... 0.8 Fe 0.2 The diffraction peaks corresponding to (PDF#97-010-2894) are consistent, indicating that it has formed a well-crystallized Cu. 0.8 Fe 0.2Phase; in Cu4Fe1-CeO x In the SiO2 sample, there was no obvious Cu. 0.8 Fe 0.2 Characteristic diffraction peaks indicate its presence in CeO₂. x It exists in a highly dispersed form within the SiO2 support.

[0020] Figure 2 (a) Freshly prepared Cu4Fe1-CeO x HAADF-STEM image of / SiO2 catalyst; Figure 2 (b) is Cu4Fe1-CeO x HAADF-STEM image of the SiO2 catalyst after 120 h of reaction in a plasma ammonia synthesis system; specific experimental details are shown in Example 6. A comparison reveals no significant difference in catalyst size before and after the reaction; Figure 2 (c) is a graph showing the particle size variation, where Fresh refers to newly prepared Cu4Fe1-CeO x / SiO2 catalyst, Used refers to Cu4Fe1-CeO after the reaction. x The graph shows the SiO2 catalyst, with the horizontal axis representing the particle size of the metal nanoparticles and the vertical axis representing the particle size distribution ratio. The graph reveals that the catalyst is Cu4Fe1-CeO2. x / The particle size remains stable before and after SiO2 participates in the reaction; Figure 2 (d) is the HAADF-STEM image of the newly prepared Cu4Fe1-SiO2 catalyst according to step (5). This sample was used as a control sample for cycle stability testing, as shown in Example 6. Figure 2 (e) is the HAADF-STEM image of Cu4Fe1-SiO2 catalyst after 48 h of reaction in plasma ammonia synthesis system. Comparison of the two images shows that obvious agglomeration occurs after the catalyst participates in the reaction, and the metal particles become larger. Figure 2 (f) is a particle size change graph, where Fresh refers to the newly prepared Cu4Fe1-SiO2 catalyst and Used refers to the Cu4Fe1-SiO2 catalyst after the reaction. The horizontal axis of the graph is the particle size of the metal nanoparticles, and the vertical axis is the particle size distribution ratio. After the reaction, the particle size of Cu4Fe1-SiO2 increased significantly, resulting in a decrease in catalyst yield.

[0021] Figure 3 The catalysts are Cu4Fe1-CeO. x Cyclic stability test graphs of / SiO2 and Cu4Fe1-SiO2; the vertical axis of the graph represents the ammonia production rate, and the product NH is quantitatively detected by UV-Vis spectroscopy. 4+The absorbance curve of the solution was measured, with the horizontal axis representing the reaction duration. Specific experimental details are shown in Example 6. It can be seen that after 120 hours of reaction, the catalyst Cu4Fe1-CeO... x The SiO2 effect remained stable; however, the yield of the Cu4Fe1-SiO2 catalyst decreased significantly during the reaction, and its cycle stability was poor.

[0022] Figure 4 To quantitatively detect NH3 using ultraviolet-visible spectroscopy 4+ Absorbance curves of standard solutions: The standard curves were determined by colorimetric titration using five sets of ammonium chloride standard solutions of different concentrations (0.02mM, 0.04mM, 0.08mM, 0.12mM, and 0.16mM). Specifically, 80 μL of tetrasodium ethylenediaminetetraacetate aqueous solution (1.3M), 160 μL of a mixed solution of sodium salicylate and pyrazole (sodium salicylate concentration 1.46M, pyrazole concentration 0.24M), and 520 μL of a mixed solution of sodium hydroxide and sodium hypochlorite (sodium hydroxide concentration 96M, sodium hypochlorite concentration 0.25M) were added to each ammonium chloride solution to induce color development. The UV-Vis absorbance of these standard solutions at 650 nm was measured, and the absorbance values ​​of these five concentrations were plotted to obtain the standard curves.

[0023] Figure 5 This diagram illustrates the application of supported metal catalysts coupled with porous materials in plasma ammonia synthesis. Three different coupling packing methods were constructed. In Strategy 1 (M1), a dual-bed structure was used, with different substances packed on each side of the reactor. 0.5g of Cu4Fe1-CeO was packed at the reactor inlet. x / SiO2 catalyst, with 5g of MCM-41 added to the other side. Strategy 2 (M2) involves adding 0.5g of Cu4Fe1-CeO x The SiO2 catalyst was ground with 5g of MCM-41 in a mortar for 20 minutes to achieve a uniform mixture at the micron level. The mixture was then pressed into tablets and sieved to 80-100 mesh. The resulting particles were then packed into the reactor. Strategy 3 (M3) involved adding 0.5g of Cu4Fe1-CeO2 catalyst. x The SiO2 catalyst and 5g of MCM-41 were placed in 200mL of aqueous solution and heated and stirred at 90℃ until the solution was completely dry. The resulting dry powder was dried overnight in a 90℃ oven, followed by calcination in a muffle furnace at 550℃ for 3 hours. This process ensured that the two were uniformly mixed at the nanoscale. The resulting sample was pressed into tablets, sieved to 80-100 mesh, and packed into a reactor.

[0024] Figure 6 Ammonia synthesis rates of metal catalysts coupled with porous materials prepared by different strategies are plotted. The vertical axis represents the ammonia production rate, and the product NH4+ is quantitatively detected by UV-Vis spectroscopy.4+ The absorbance curves of the solution were measured, with the horizontal axis M1, M2, and M3 corresponding to strategies one, two, and three, respectively. Plasma ammonia synthesis was carried out using three different coupling packing strategies under conditions of 35 W discharge power, 10 mL / min nitrogen gas flow rate, and 30 mL / min hydrogen gas flow rate, as detailed in Example 5. The vertical axis of the graph represents the ammonia production rate, and the product NH4+ was quantitatively detected by UV-Vis spectroscopy. 4+ The absorbance curves of the solution were determined. As shown in the figure, the plasma ammonia synthesis reaction implemented using strategy three (M3) yielded the best results, with an ammonia synthesis rate reaching 7721 μmol g / L. -1 h -1 .

[0025] Figure 7 The graph shows the relationship between the energy yield and the ammonia outlet concentration in plasma ammonia synthesis using metal catalysts coupled with porous materials prepared by different strategies. The vertical axis represents the energy yield, which is calculated as the energy consumed per kilowatt-hour to produce one gram of ammonia per unit time. Taking Example 5 as an example, 0.058 g of ammonia was produced in 1 hour at 65 W, and the energy consumed was 1 h × 0.065 kW = 0.065 kWh. The ratio of 0.89 is the energy yield. The mass of ammonia produced per hour was quantitatively detected by UV-Vis spectroscopy using the product NH4+. 4+ The ammonia production rate calculated by the solution method is (ammonia production rate × 1h × 0.5g). 催化剂 ×17×10 -6 The vertical axis represents the ammonia outlet concentration, determined by mass spectrometry. Compared with data in existing literature, the supported metal catalyst coupled with porous materials strategy proposed in this invention has a significant advantage in catalytic efficiency in plasma ammonia synthesis, as shown in the figure. The "starred" position represents the ammonia outlet concentration and energy efficiency obtained at a discharge power of 65W in Example 5 of this invention, where the ammonia outlet concentration reaches the highest value of 44386ppm in the current field of plasma ammonia synthesis. In the figure, square symbols represent electrode materials (lead zirconium titanate) catalysts, hexagons represent various oxide catalysts (magnesium oxide, aluminum oxide, silicon oxide, cerium oxide, etc.), rhombuses represent ruthenium-based catalysts (Ru-Al2O3, Ru-C3N4, Ru-SiO2, Ru-MgO, etc.), solid circles represent other metal catalysts (iron, nickel, silver, copper, gold, etc.), and hollow circles represent molecular sieve-type filling materials (ZSM-5, MCM-41, SBA-15, zeolite-5A, etc.). Detailed Implementation

[0026] Example 1: Application of supported metal catalysts coupled with porous materials in low-temperature plasma ammonia synthesis reaction with different proportions.

[0027] (1) Preparation of cerium oxide nanoisland carrier: 3.6 g of amorphous silica was placed in 1 L of deionized water and sonicated for 30 min to produce a homogeneous mixture solution; 4 mmol of cerium nitrate was dissolved in the mixture solution, and ammonia water (2 M) was rapidly injected to adjust the pH of the solution to 8.7. After vacuum filtration, the solution was dried at 70 °C for 12 h. The resulting dry powder was thoroughly ground and calcined at 600 °C for 12 h (heating rate maintained at 5 °C / min) to obtain approximately 3.8 g of cerium oxide nanoisland carrier dry powder, denoted as CeO. x / SiO2 support;

[0028] (2) Preparation of copper-iron alloy-cerium oxide nanoisland catalyst: Weigh 1g of the cerium oxide nanoisland support dry powder obtained in step (1) and dissolve it in 40mL of deionized water. Sonicate for 5min to produce a homogeneous mixture. Dissolve ferric nitrate and copper nitrate in 10mL of deionized water at a molar ratio of 1:1. Add the resulting solution containing copper and iron salts to the prepared mixture and stir vigorously. Add ammonia solution (2M) dropwise to adjust the pH of the mixture to 8. Then stir at 80℃ for 24h. Wash the obtained product with deionized water and centrifuge 5 times at 8000r / min. Finally, dry it in an oven at 120℃ for 12h. Grind the obtained dry powder thoroughly and calcine it in a muffle furnace at 600℃ for 4h. Then calcine the obtained dry powder in an atmosphere of 95% volume argon and 5% volume hydrogen at 600℃ for 4h to obtain Cu 2.5 Fe 2.5 -CeO x Approximately 1.05 g of a copper-iron alloy / cerium oxide nanoisland catalyst containing SiO2, and CeO x Cu on SiO2 support 2.5 Fe 2.5 The loading rate is 5 wt%.

[0029] (3) Preparation of metal catalyst coupled with porous materials and ammonia synthesis reaction under plasma conditions: Strategy 1 (M1), we used a dual-bed structure, filling 0.5g Cu at the gas inlet of the dielectric barrier discharge quartz reactor. 2.5 Fe 2.5 -CeO x / SiO2, and fill the other side with 5g of MCM-41 to obtain a metal catalyst coupled porous material; Strategy 2 (M2), add 0.5g Cu 2.5 Fe 2.5 -CeO x / SiO2 and 5g of MCM-41 were ground in a mortar for 20 minutes to achieve micron-level uniform mixing. The resulting dry powder was pressed into tablets and sieved to 80-100 mesh to obtain a metal catalyst coupled porous material, which was then filled into a dielectric barrier discharge quartz reactor; Strategy 3 (M3) was to add 0.5g of Cu 2.5Fe 2.5 -CeO x SiO2 and 5g of MCM-41 were placed in 200mL of aqueous solution and heated and stirred at 90℃ until the solution was completely dried. The resulting dry powder was dried overnight in a 90℃ oven, and then calcined in a muffle furnace at 550℃ for 3h to achieve nanoscale uniform mixing. Finally, the calcined product was pressed into tablets and sieved to 80-100 mesh to obtain a metal catalyst coupled with porous material, which was then filled into a dielectric barrier discharge quartz reactor. The ammonia synthesis reaction conditions were a plasma discharge power of 35W, with the plasma source frequency set to 10kHz, peak-to-peak voltage set to 14kV, nitrogen gas flow rate of 10mL / min, and hydrogen gas flow rate of 30mL / min. The ammonia production was determined by colorimetric titration. Strategy 3 (M3) showed the highest catalytic activity, with an ammonia production rate of 4764μmol / g. -1 h -1 .

[0030] Example 2: Application of supported metal catalysts coupled with porous materials in low-temperature plasma ammonia synthesis reaction with different proportions

[0031] (1) Preparation of cerium oxide nanoisland carrier: 3.6 g of amorphous silica was placed in 1 L of deionized water and sonicated for 30 min to produce a homogeneous mixture solution; 4 mmol of cerium nitrate was dissolved in the mixture solution, and ammonia water (2 M) was rapidly injected to adjust the pH of the solution to 8.7. After vacuum filtration, the solution was dried at 70 °C for 12 h. The resulting dry powder was thoroughly ground and calcined at 600 °C for 12 h (heating rate maintained at 5 °C / min) to obtain approximately 3.8 g of cerium oxide nanoisland carrier dry powder, denoted as CeO. x / SiO2 support;

[0032] (2) Preparation of copper-iron alloy-cerium oxide nanoisland catalyst: Weigh 1g of the cerium oxide nanoisland support dry powder obtained in step (1) and dissolve it in 40mL of deionized water. Sonicate for 5min to produce a homogeneous mixture. Dissolve ferric nitrate and copper nitrate in 10mL of deionized water at a molar ratio of 2:3. Add the solution containing copper salt and iron salt to the prepared mixture and stir vigorously. Add sodium carbonate solution (2M) dropwise to adjust the pH of the mixture to 8. Stir at 80℃ for 24h. Wash the obtained product with deionized water and centrifuge 5 times at 8000r / min. Then dry in an oven at 120℃ for 12h. Grind the obtained dry powder thoroughly and calcine it in a muffle furnace at 600℃ for 4h. Then calcine the obtained dry powder in an atmosphere of 95% volume argon and 5% volume hydrogen at 600℃ for 4h to obtain Cu3Fe2-CeO x / Approximately 1.05g of SiO2 catalyst, CeO x The loading of Cu3Fe2 on the SiO2 support was 5 wt%.

[0033] (3) Preparation of metal catalyst coupled with porous materials and ammonia synthesis reaction under plasma conditions: Strategy 1 (M1) We used a dual-bed structure, and filled 0.5g Cu3Fe2-CeO at the gas inlet of the dielectric barrier discharge quartz reactor. x / SiO2, and fill the other side with 5g of MCM-41 to obtain a metal catalyst coupled porous material; Strategy 2 (M2), 0.5g of Cu3Fe2-CeO x / SiO2 and 5g of MCM-41 are ground in a mortar for 20 minutes to achieve micron-level uniform mixing. The resulting dry powder is pressed into tablets and sieved to 80-100 mesh to obtain a metal catalyst coupled porous material, which is then filled into a dielectric barrier discharge quartz reactor; Strategy 3 (M3) involves adding 0.5g of Cu3Fe2-CeO x SiO2 and 5g of MCM-41 were placed in 200mL of aqueous solution and heated and stirred at 90℃ until the solution was completely dried. The resulting dry powder was dried overnight in a 90℃ oven, and then calcined in a muffle furnace at 550℃ for 3h to achieve nanoscale uniform mixing. Finally, the calcined product was pressed into tablets and sieved to 80-100 mesh to obtain a metal catalyst coupled with porous material, which was then filled into a dielectric barrier discharge quartz reactor. The ammonia synthesis reaction conditions were a plasma discharge power of 35W, with the plasma source frequency set to 10kHz, peak-to-peak voltage set to 14kV, nitrogen gas flow rate of 10mL / min, and hydrogen gas flow rate of 30mL / min. The ammonia production was determined by colorimetric titration. Strategy 3 (M3) showed the highest catalytic activity, with an ammonia production rate of 5071μmol / g. -1 h -1 .

[0034] Example 3: Application of supported metal catalysts coupled with porous materials in low-temperature plasma ammonia synthesis reaction with different proportions

[0035] (1) Preparation of cerium oxide nanoisland carrier: 3.6 g of amorphous silica was placed in 1 L of deionized water and sonicated for 30 min to produce a homogeneous mixture solution; 4 mmol of cerium nitrate was dissolved in the mixture solution, and ammonia water (2 M) was rapidly injected to adjust the pH of the solution to 8.7. After vacuum filtration, the solution was dried at 70 °C for 12 h. The resulting dry powder was thoroughly ground and calcined at 600 °C for 12 h (heating rate maintained at 5 °C / min) to obtain approximately 3.8 g of cerium oxide nanoisland carrier dry powder, denoted as CeO. x / SiO2 support;

[0036] (2) Preparation of copper-iron alloy-cerium oxide nanoisland catalyst: Weigh 1g of the cerium oxide nanoisland support dry powder obtained in step (1) and dissolve it in 40mL of deionized water. Sonicate for 5min to produce a homogeneous mixture. Dissolve ferric nitrate and copper nitrate in 10mL of deionized water at a molar ratio of 4:1. Add the solution containing copper salt and iron salt to the prepared mixture and stir vigorously. Add sodium carbonate solution (2M) dropwise to adjust the pH of the mixture to 8. Stir at 80℃ for 24h. Wash the obtained product with deionized water and centrifuge 5 times at 8000r / min. Then dry it in an oven at 120℃ for 12h. Grind the obtained dry powder thoroughly and calcine it in a muffle furnace at 600℃ for 4h. Then calcine the obtained dry powder in an atmosphere of 95% volume argon and 5% volume hydrogen at 600℃ for 4h to obtain Cu1Fe4-CeO x / Approximately 1.05g of SiO2 catalyst, CeO x The loading of Cu1Fe4 on the SiO2 support was 5 wt%.

[0037] (3) Preparation of metal catalyst coupled with porous materials and ammonia synthesis reaction under plasma conditions: Strategy 1 (M1) We used a dual-bed structure, and filled 0.5g Cu1Fe4-CeO at the gas inlet of the dielectric barrier discharge quartz reactor. x / SiO2, and fill the other side with 5g of MCM-41 to obtain a metal catalyst coupled porous material; Strategy 2 (M2), 0.5Cu1Fe4-CeO x / SiO2 and 5g of MCM-41 are ground in a mortar for 20 minutes to achieve micron-level uniform mixing. The resulting dry powder is pressed into tablets and sieved to 80-100 mesh to obtain a metal catalyst coupled porous material, which is then filled into a dielectric barrier discharge quartz reactor; Strategy 3 (M3) involves adding 0.5g of Cu1Fe4-CeO x SiO2 and 5g of MCM-41 were placed in 200mL of aqueous solution and heated and stirred at 90℃ until the solution was completely dried. The resulting dry powder was dried overnight in a 90℃ oven, and then calcined in a muffle furnace at 550℃ for 3h to achieve nanoscale uniform mixing. Finally, the calcined product was pressed into tablets and sieved to 80-100 mesh to obtain a metal catalyst coupled with porous material, which was then filled into a dielectric barrier discharge quartz reactor. The ammonia synthesis reaction conditions were a plasma discharge power of 35W, with the plasma source frequency set to 10kHz, peak-to-peak voltage set to 14kV, nitrogen gas flow rate of 10mL / min, and hydrogen gas flow rate of 30mL / min. The ammonia production was determined by colorimetric titration. Strategy 3 (M3) showed the highest catalytic activity, with an ammonia production rate of 4672μmol / g. -1 h -1 .

[0038] Example 4: Application of supported metal catalysts coupled with porous materials in low-temperature plasma ammonia synthesis reaction with different proportions

[0039] (1) Preparation of cerium oxide nanoisland carrier: 3.6 g of amorphous silica was placed in 1 L of deionized water and sonicated for 30 min to produce a homogeneous mixture solution; 4 mmol of cerium nitrate was dissolved in the mixture solution, and ammonia water (2 M) was rapidly injected to adjust the pH of the solution to 8.7. After vacuum filtration, the solution was dried at 70 °C for 12 h. The resulting dry powder was thoroughly ground and calcined at 600 °C for 12 h (heating rate maintained at 5 °C / min) to obtain approximately 3.8 g of cerium oxide nanoisland carrier dry powder, denoted as CeO. x / SiO2 support;

[0040] (2) Preparation of copper-iron alloy-cerium oxide nanoisland catalyst: Weigh 1g of the cerium oxide nanoisland support dry powder obtained in step (1) and dissolve it in 40mL of deionized water. Sonicate for 5min to produce a homogeneous mixture. Dissolve ferric nitrate and copper nitrate in 10mL of deionized water at a molar ratio of 3:2. Add the solution containing copper salt and iron salt to the prepared mixture and stir vigorously. Add sodium carbonate solution (2M) dropwise to adjust the pH of the mixture to 8. Stir at 80℃ for 24h. Wash the obtained product with deionized water and centrifuge 5 times at 8000r / min. Then dry in an oven at 120℃ for 12h. Grind the obtained dry powder thoroughly and calcine it in a muffle furnace at 600℃ for 4h. Then calcine the obtained dry powder in an atmosphere of 95% volume argon and 5% volume hydrogen at 600℃ for 4h to obtain Cu2Fe3-CeO x / Approximately 1.05g of SiO2 catalyst, CeO x The loading of Cu2Fe3 on the SiO2 support was 5 wt%.

[0041] (3) Preparation of metal catalyst coupled with porous materials and ammonia synthesis reaction under plasma conditions: Strategy 1 (M1) We used a dual-bed structure, and filled 0.5g Cu2Fe3-CeO at the gas inlet of the dielectric barrier discharge quartz reactor. x / SiO2, and fill the other side with 5g of MCM-41 to obtain a metal catalyst coupled porous material; Strategy 2 (M2), 0.5Cu2Fe3-CeO x / SiO2 and 5g of MCM-41 are ground in a mortar for 20 minutes to achieve micron-level uniform mixing. The resulting dry powder is pressed into tablets and sieved to 80-100 mesh to obtain a metal catalyst coupled porous material, which is then filled into a dielectric barrier discharge quartz reactor; Strategy 3 (M3) involves adding 0.5g of Cu2Fe3-CeO xSiO2 and 5g of MCM-41 were placed in 200mL of aqueous solution and heated and stirred at 90℃ until the solution was completely dried. The resulting dry powder was dried overnight in a 90℃ oven, and then calcined in a muffle furnace at 550℃ for 3h to achieve nanoscale uniform mixing. Finally, the calcined product was pressed into tablets and sieved to 80-100 mesh to obtain a metal catalyst coupled with porous material, which was then filled into a dielectric barrier discharge quartz reactor. The ammonia synthesis reaction conditions were a plasma discharge power of 35W, with the plasma source frequency set to 10kHz, peak-to-peak voltage set to 14kV, nitrogen gas flow rate of 10mL / min, and hydrogen gas flow rate of 30mL / min. The ammonia production was determined by colorimetric titration. Strategy 3 (M3) showed the highest catalytic activity, with an ammonia production rate of 5789μmol / g. -1 h -1 .

[0042] Example 5: Application of supported metal catalysts coupled with porous materials in low-temperature plasma ammonia synthesis reaction with different proportions

[0043] (1) Preparation of cerium oxide nanoisland carrier: 3.6 g of amorphous silica was placed in 1 L of deionized water and sonicated for 30 min to produce a homogeneous mixture solution; 4 mmol of cerium nitrate was dissolved in the mixture solution, and ammonia water (2 M) was rapidly injected to adjust the pH of the solution to 8.7. After vacuum filtration, the solution was dried at 70 °C for 12 h. The resulting dry powder was thoroughly ground and calcined at 600 °C for 12 h (heating rate maintained at 5 °C / min) to obtain approximately 3.8 g of cerium oxide nanoisland carrier dry powder, denoted as CeO. x / SiO2 support;

[0044] (2) Preparation of copper-iron alloy-cerium oxide nanoisland catalyst: Weigh 1g of the cerium oxide nanoisland support dry powder obtained in step (1) and dissolve it in 40mL of deionized water. Sonicate for 5min to produce a homogeneous mixture. Dissolve ferric nitrate and copper nitrate in 10mL of deionized water at a molar ratio of 1:4. Add the solution containing copper and iron salts to the prepared mixture and stir vigorously. Add sodium carbonate solution (2M) dropwise to adjust the pH of the mixture to 8. Stir at 80℃ for 24h. Wash the obtained product with deionized water and centrifuge 5 times at 8000r / min. Dry in an oven at 120℃ for 12h. Grind the obtained dry powder thoroughly and calcine it in a muffle furnace at 600℃ for 4h. Then calcine the obtained dry powder in an atmosphere of 95% volume argon and 5% volume hydrogen at 600℃ for 4h to obtain Cu4Fe1-CeO x / SiO2 catalyst 1.05g, CeO x The loading of Cu4Fe1 on the SiO2 support was 5 wt%.

[0045] (3) Preparation of metal catalyst coupled with porous materials and ammonia synthesis reaction under plasma conditions: Strategy 1 (M1) We used a dual-bed structure, and filled 0.5g Cu4Fe1-CeO at the gas inlet of the dielectric barrier discharge quartz reactor. x / SiO2, and fill the other side with 5g of MCM-41 to obtain a metal catalyst coupled porous material; Strategy 2 (M2), 0.5Cu4Fe1-CeO x / SiO2 and 5g of MCM-41 are ground in a mortar for 20 minutes to achieve micron-level uniform mixing. The resulting dry powder is pressed into tablets and sieved to 80-100 mesh to obtain a metal catalyst coupled porous material, which is then filled into a dielectric barrier discharge quartz reactor; Strategy 3 (M3) involves adding 0.5g of Cu4Fe1-CeO x SiO2 and 5g of MCM-41 were placed in 200mL of aqueous solution and heated and stirred at 90℃ until the solution was completely dried. The resulting dry powder was dried overnight in a 90℃ oven, and then calcined in a muffle furnace at 550℃ for 3h to achieve nanoscale uniform mixing. Finally, the calcined product was pressed into tablets and sieved to 80-100 mesh to obtain a metal catalyst coupled with porous material, which was then filled into a dielectric barrier discharge quartz reactor. The ammonia synthesis reaction conditions were a plasma discharge power of 35W, with the plasma source frequency set to 10kHz, peak-to-peak voltage set to 14kV, nitrogen gas flow rate of 10mL / min, and hydrogen gas flow rate of 30mL / min. The ammonia production was determined by colorimetric titration. Strategy 3 (M3) showed the highest catalytic activity, with an ammonia production rate of 9121μmol / g. -1 h -1 .

[0046] Example 6: Catalysts Cu4Fe1-SiO2 and Cu4Fe1-CeO x Application of SiO2 in Low-Temperature Plasma Ammonia Synthesis

[0047] (1) Copper-iron alloy-cerium oxide nanoisland catalyst Cu4Fe1-CeO x The preparation of / SiO2 is the same as in Example 5;

[0048] (2) Preparation of Cu4Fe1-SiO2 catalyst (copper-iron alloy-silica): 1 g of amorphous silica was dissolved in 40 mL of deionized water and sonicated for 5 min to produce a homogeneous mixture. Ferric nitrate and copper nitrate were dissolved in 10 mL of deionized water at a molar ratio of 1:4. The solution containing copper and iron salts was added to the mixture and stirred vigorously. Sodium carbonate solution (2 M) was added dropwise to adjust the pH of the mixture to 8. The mixture was stirred at 80 °C for 24 h. The product was washed with deionized water and centrifuged 5 times at 8000 r / min. The product was then dried in an oven at 120 °C for 12 h. The resulting dry powder was thoroughly ground and calcined in a muffle furnace at 600 °C for 4 h. The resulting dry powder was then calcined in an atmosphere of 95% volume argon and 5% volume hydrogen at 600 °C for 4 h to obtain 1.05 g of Cu4Fe1-SiO2 catalyst with a Cu4Fe1 loading of 5 wt% on the SiO2 support.

[0049] (3) Plasma ammonia synthesis reaction process used to test the cyclic stability of the catalyst: Reaction 1: 0.5g Cu4Fe1-SiO2 and 5g quartz sand (80-100 mesh, without MCM-41 to eliminate the influence of mesoporous materials on the reaction, only observing the stability of the catalyst itself) were ground for 15min and mixed evenly. The mixture was placed in a dielectric barrier discharge quartz reactor. The reaction conditions were a plasma discharge power of 35W, with the plasma source frequency set to 10kHz, peak-to-peak voltage set to 14kV, nitrogen gas flow rate of 10mL / min, and hydrogen gas flow rate of 30mL / min. The reaction lasted for 48h, and measurements were taken every two hours. The amount of ammonia generated was determined by colorimetric titration. Reaction 2: 0.5g Cu4Fe1-CeO2 was ground for 15min. x The SiO2 catalyst was ground and uniformly mixed with 5g of quartz sand (80-100 mesh) for 15 min, and placed in a dielectric barrier discharge quartz reactor. The reaction conditions were: plasma discharge power of 35W, plasma source frequency of 10kHz, peak-to-peak voltage of 14kV, nitrogen gas flow rate of 10mL / min, and hydrogen gas flow rate of 30mL / min. The reaction lasted for 120h, and the ammonia production was determined by colorimetric titration every two hours. Comparison of experimental data showed that the activity of the Cu4Fe1-SiO2 catalyst gradually decreased during the reaction, while that of the Cu4Fe1-CeO2 catalyst decreased. x The reaction activity of the / SiO2 catalyst remains stable, such as Figure 3 As shown.

[0050] The above examples are further detailed descriptions of the present invention and should not be construed as limiting the specific embodiments of the present invention to these examples. The above examples illustrate that the supported metal catalyst coupled with porous material strategy we provide has good catalytic activity and good cycle stability in plasma ammonia synthesis reaction, and is an efficient and practical plasma catalytic ammonia synthesis strategy.

Claims

1. A method for preparing a supported metal catalyst coupled with a porous material, comprising the following steps: (1) Preparation of cerium oxide nanoisland carrier: Take 3-4 g of silicon dioxide and place it in 0.1-1 L of deionized water. Sonicate for 10-30 min to produce a homogeneous mixture solution. Dissolve 3-5 mmol of cerium salt in the mixture solution. Quickly inject alkaline solution to adjust the pH of the solution to 8-9. After vacuum filtration, dry at 50-70 °C for 10-15 h. Grind the obtained dry powder thoroughly and calcine at 400-800 °C for 5-12 h to obtain cerium oxide nanoisland carrier, denoted as CeO. x / SiO2 support; wherein cerium oxide nano islands are clusters with a particle size of 2~3 nm, uniformly loaded on silicon dioxide; (2) Preparation of copper-iron alloy-cerium oxide nanoisland catalyst: Weigh 1 g of the cerium oxide nanoisland support dry powder obtained in step (1) and dissolve it in 20-100 mL of deionized water. Sonicate for 5-30 min to produce a homogeneous mixture. Dissolve iron salt and copper salt in 10-20 mL of deionized water according to stoichiometric ratio. Add the solution containing copper salt and iron salt to the mixture and stir vigorously. Add alkali solution to adjust the pH of the mixture to 7.5-8.

5. Then stir at a constant temperature of 60-100 °C for 20-30 h. Wash the obtained product with deionized water and centrifuge at 6000-10000 r / min 3-6 times. Finally, dry at 110-130 °C for 10-15 h. Grind the obtained dry powder thoroughly and calcine at 400-800 °C for 2-6 h. Then calcine the obtained dry powder at 400-800 °C for 2-6 h in an atmosphere of 95% volume argon and 5% volume hydrogen for 400-800 °C. h, yielding the chemical formula Cu y Fe 5-y -CeO x / SiO2 copper-iron alloy-cerium oxide nanoisland catalyst; y<5, x<2, CeO x Cu on SiO2 support y Fe 5-y The load is 3~8 wt%; (3) Preparation of metal catalyst coupled porous material: 0.5 g of Cu obtained in step (2) was used. y Fe 5-y -CeO x The SiO2 catalyst and 5 g of mesoporous material were added to 180-220 mL of aqueous solution and heated and stirred at 85-95 °C until the solution was completely dry. The resulting dry powder was dried overnight at 85-95 °C and then calcined at 500-600 °C for 2-5 h to achieve uniform mixing at the nanoscale. Finally, the calcined product was pressed into tablets and sieved to 80-100 mesh to obtain the metal catalyst coupled porous material.

2. The method for preparing a supported metal catalyst coupled with a porous material as described in claim 1, characterized in that: The heating rate during calcination in step (1) is 1~5 ℃ / min, and the heating rate during calcination in steps (2) and (3) is 5 ℃ / min.

3. The method for preparing a supported metal catalyst coupled with a porous material as described in claim 1, characterized in that: In step (1), the silica is one or two of silica microspheres with a particle size of 20~200 nm or amorphous silica; the cerium salt is one or more of cerium nitrate, cerium sulfate, cerium chloride, cerium oxalate, cerium carbonate, and cerium acetate; and the alkaline solution is one or more of sodium hydroxide solution, ammonia water, potassium hydroxide solution, and sodium carbonate solution.

4. The method for preparing a supported metal catalyst coupled with a porous material as described in claim 1, characterized in that: In step (2), the iron salt is one or more of ferric nitrate, ferric sulfate, ferric chloride, ferric phosphate, and ferric citrate; the copper salt is one or more of copper nitrate, copper chloride, and copper sulfate; and the alkaline solution is one or more of sodium hydroxide solution, ammonia water, potassium hydroxide solution, and sodium carbonate solution.

5. The method for preparing a supported metal catalyst coupled with a porous material as described in claim 1, characterized in that: The mesoporous material in step (3) is one or more of SBA-15, MCM-48, MCM-41, and KIT-6.

6. A supported metal catalyst coupled porous material, characterized in that: It is prepared by the method described in any one of claims 1 to 5.

7. The application of the supported metal catalyst coupled with porous material as described in claim 6 in the low-temperature plasma ammonia synthesis reaction.

8. The application of a supported metal catalyst coupled with a porous material as described in claim 7 in a low-temperature plasma ammonia synthesis reaction, characterized in that: The reaction conditions for low-temperature plasma ammonia synthesis are as follows: plasma discharge power of 30~70 W, plasma source frequency of 8~15 kHz, peak voltage of 10~20 kV, nitrogen gas flow rate of 5~15 mL / min, and hydrogen gas flow rate of 15~45 mL / min.

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