A high-activity potassium-ruthenium catalyst, a preparation method and application thereof

Abstract

This invention discloses a highly active potassium ruthenium catalyst, its preparation method, and its applications. Using ruthenium chloride as the ruthenium precursor, magnesium hydroxide as the supported precursor, and potassium hydroxide as the auxiliary precursor, a magnesium hydroxide-supported potassium ruthenium precursor is synthesized via ion deposition and impregnation methods. The catalyst is then obtained through calcination and reduction treatment. The catalyst of this invention exhibits excellent metal-auxiliary interaction and demonstrates superior low-temperature activity and long-term stability in the ammonia decomposition reaction, even with pure ammonia at 30,000 mL / (g) cat The ammonia decomposition conversion rate can reach 97.1% at 450℃ and is within the range of 60000 mL / (g) cat The reaction remains stable at 475℃ for 100 h. The preparation method of this invention has advantages such as inexpensive raw materials, simple process, convenient operation, mild and easily controllable conditions, good repeatability, and low chlorine residue, making it suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology for hydrogen production from ammonia decomposition, specifically to a highly active potassium ruthenium catalyst, its preparation method, and its application. Background Technology

[0002] Ammonia, as an ideal hydrogen carrier, holds promise for solving the challenges of hydrogen storage and transportation due to its high hydrogen storage density, safety, and mature industrial foundation. The key to its core application—ammonia decomposition for hydrogen production—lies in the development of highly efficient catalysts, with ruthenium catalysts showing the greatest potential. Improving catalyst activity while reducing costs remains the main focus of current ammonia decomposition catalyst research and development. To enhance the activity of ruthenium-based ammonia decomposition catalysts and meet the requirements for large-scale production, current technologies tend to use inexpensive and readily available ruthenium chloride as a precursor. However, this introduces chloride ions that are difficult to completely remove, not only poisoning the catalyst but also severely hindering the effectiveness of performance improvements through the addition of alkali metal promoters. Traditional ruthenium-based catalysts are often prepared using impregnation or co-precipitation methods. In the impregnation method, ruthenium particles tend to agglomerate, and the large particle size of ruthenium metal affects the interaction between the metal and the support, resulting in low catalytic activity. It also introduces chloride ions, which are detrimental to subsequent alkali metal modification. In the co-precipitation method, loading ruthenium metal nanoparticles onto the support requires a precipitant for control, and the precipitation conditions are strictly controlled. Furthermore, the segmented process of adding alkali metal promoters via post-impregnation in existing technologies results in weak interaction between ruthenium metal and alkali metal promoters because ruthenium catalyst preparation and alkali metal modification are carried out independently, leading to a limited effect on catalyst activity promotion.

[0003] Chinese patent CN119819302A discloses a catalyst for hydrogen production from ammonia decomposition under mild conditions, its preparation, and its application. Using octahedral magnesium oxide as a support, the preparation process involves first preparing solutions containing ruthenium salt, transition metal precursors, rare earth metal precursors, and alkali metal precursors. These solutions are then mixed with a portion of the octahedral magnesium oxide support, a binder, and a pore-forming agent. Finally, the remaining octahedral magnesium oxide support is added. The mixture is then filtered, kneaded, aged, dried, and calcined to obtain the ammonia decomposition catalyst. However, this process suffers from several drawbacks: firstly, it requires binders and other materials to assist in loading the active metal, resulting in complex operation; secondly, the interaction between the active metal, additives, and support is poor, leading to limited catalyst activity promotion and affecting the catalyst's activity and long-term stability at low temperatures. Summary of the Invention

[0004] To address the shortcomings of existing low-temperature ammonia decomposition catalysts, such as complex preparation processes and weak interactions between ruthenium metal and alkali metals, as well as between the catalyst and the support, resulting in poor catalyst activity promotion, this paper proposes a highly active potassium ruthenium catalyst with strong interactions between ruthenium metal, alkali metal, and the support; high ruthenium metal dispersion; and excellent promotion of ammonia decomposition activity by alkali metal promoters. This catalyst exhibits good low-temperature activity and long-term stability, along with its preparation method and applications.

[0005] The technical solution adopted by this invention to solve its technical problem is: a method for preparing a highly active potassium ruthenium catalyst, characterized by including the following steps: Step 1: In step one, sodium hydroxide solution is added dropwise to magnesium nitrate solution under stirring. After the addition is complete, the precipitate is filtered. The precipitate is washed, dried, and ground into powder to obtain a magnesium hydroxide precursor. In step two, the magnesium hydroxide precursor is dispersed in deionized water under stirring at room temperature. Ruthenium chloride is then added dropwise to the magnesium hydroxide suspension. After the addition is complete, the suspension is filtered and the filtered product is washed to remove chloride-containing compounds generated during the addition process. After drying, a magnesium hydroxide-supported ruthenium precursor is obtained. In step three, the obtained magnesium hydroxide-supported ruthenium precursor is dispersed in deionized water. A potassium hydroxide solution is added dropwise under stirring. The magnesium hydroxide-supported ruthenium precursor dispersion containing potassium hydroxide is dried by rotary evaporation to obtain a magnesium hydroxide-supported potassium ruthenium precursor. In step four, the obtained magnesium hydroxide-supported potassium ruthenium precursor is calcined. After calcination, the magnesium hydroxide-supported potassium ruthenium precursor is reduced under a hydrogen atmosphere to obtain a highly active potassium ruthenium catalyst.

[0006] Furthermore, in step one, the concentration of the magnesium nitrate solution is 1–5 mol / L; the concentration of the sodium hydroxide solution is 1–5 mol / L; the precipitate is washed with 1500 ml of deionized water and dried at 60°C.

[0007] Furthermore, in step two, the concentration of the magnesium nitrate solution is 1–5 mol / L; the concentration of the sodium hydroxide solution is 1–5 mol / L; the precipitate is washed with 1500 ml of deionized water and dried at 60°C.

[0008] Furthermore, in step three, the magnesium hydroxide-supported ruthenium precursor dispersion containing potassium hydroxide is subjected to rotary evaporation drying at 60–80°C and a rotation speed of 60–80 r / min.

[0009] Furthermore, in step four, the obtained magnesium hydroxide-supported ruthenium hydroxide precursor is calcined in an argon or air atmosphere at a temperature of 500–600°C for 30 minutes. After calcination, the magnesium hydroxide-supported ruthenium hydroxide precursor is reduced in a hydrogen atmosphere at a temperature of 500–600°C for 30 minutes.

[0010] A highly active potassium-ruthenium catalyst is prepared by a method thereof; the mass content of ruthenium metal is 1-3%; the molar ratio of potassium to ruthenium is 0.5-2.

[0011] Application of a highly active potassium ruthenium catalyst for hydrogen production from ammonia decomposition.

[0012] The highly active potassium ruthenium catalyst, its preparation method, and its application described in this invention have the following characteristics and advantages: This invention employs ion deposition to synthesize a Ru / Mg(OH)₂ precursor, achieving quantitative loading and uniform dispersion of ruthenium species by anchoring ruthenium metal ions through the hydroxyl groups on the Mg(OH)₂ surface. Compared with traditional co-precipitation and deposition-precipitation methods, the ion deposition method of this invention does not require a precipitant and has advantages such as simple process, convenient operation, mild and easily controllable conditions, and good repeatability.

[0013] This invention prepares a K-Ru / MgO catalyst by calcining and reducing the K-Ru / Mg(OH)2 precursor, successfully constructing a good metal-promoter interaction, which greatly enhances the promoting effect of K promoter on the ammonia decomposition activity of Ru / MgO catalyst.

[0014] The ruthenium catalyst of the present invention has high dispersibility, with an average particle size of 2.5 nm for the ruthenium metal nanoparticles, exhibiting strong metal-support interaction and good anti-sintering properties.

[0015] The K-Ru / MgO catalyst of this invention exhibits excellent low-temperature activity and long-term stability for ammonia decomposition, even with pure ammonia at 30,000 mL / (g) cat The ammonia decomposition conversion rate can reach 97.1% at 450 °C (·h); at pure ammonia and a space velocity of 60000 mL / (g·h), the conversion rate can reach 97.1%. cat Under the conditions of ∙h), the ammonia decomposition conversion rate at 475 ℃ can reach 96%, and the reactivity remains stable after 100 h. Attached Figure Description

[0016] To more clearly illustrate the specific embodiments of the present invention, the accompanying drawings used in the specific embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 The X-ray powder diffraction pattern of the catalyst in Example 1 of this invention is shown below. Figure 2 The X-ray powder diffraction pattern of the catalyst in Example 2 of this invention is shown below. Figure 3 This is a high-angle annular dark-field scanning transmission electron microscope image of the catalyst in Example 2 of the present invention; Figure 4 The Cl 2p X-ray photoelectron spectrum of the precursor in Example 2 of this invention; Figure 5 The Cl 2p X-ray photoelectron spectrum of the catalyst in Example 2 of this invention; Figure 6 The X-ray powder diffraction pattern of the catalyst in Example 3 of this invention is shown below. Figure 7 The X-ray powder diffraction pattern of the catalyst in Example 4 of this invention is shown below. Figure 8 The X-ray powder diffraction pattern of the catalyst in Example 5 of this invention is shown below. Figure 9 The X-ray powder diffraction pattern of the catalyst in Example 6 of this invention is shown below. Figure 10 The X-ray powder diffraction pattern of the catalyst in Comparative Example 1 is shown. Figure 11 The X-ray powder diffraction pattern of the catalyst in Comparative Example 2 is shown below. Figure 12 The X-ray powder diffraction pattern of the catalyst in Comparative Example 3 is shown below. Figure 13 The results of the ammonia decomposition activity test of the catalyst in Example 2 of this invention; Figure 14 The results show the long-term stability test results of the catalyst in Example 2 of this invention for ammonia decomposition. Detailed Implementation

[0018] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] like Figures 1-9 as well as Figures 13-14 As shown, the preparation method of a highly active potassium ruthenium catalyst according to the present invention includes the following steps: Step 1: Add sodium hydroxide solution dropwise to magnesium nitrate solution while stirring; after the addition is complete, filter the resulting precipitate; wash, dry, and grind the obtained precipitate into powder to obtain magnesium hydroxide precursor; Step 2: Disperse the magnesium hydroxide precursor in deionized water by stirring at room temperature; then add ruthenium chloride dropwise to the magnesium hydroxide suspension; after the addition is complete, filter and wash the filtered product to remove compounds containing chloride ions generated during the addition process; after drying, obtain the magnesium hydroxide-supported ruthenium precursor. Step 3: Disperse the obtained magnesium hydroxide-supported ruthenium precursor in deionized water; add potassium hydroxide solution dropwise while stirring; dry the magnesium hydroxide-supported ruthenium precursor dispersion containing potassium hydroxide by rotary evaporation to obtain magnesium hydroxide-supported potassium ruthenium precursor. Step 4: Calcining the obtained magnesium hydroxide-supported potassium ruthenium precursor; after calcination, reducing the magnesium hydroxide-supported potassium ruthenium precursor under a hydrogen atmosphere to obtain a highly active potassium ruthenium catalyst.

[0020] In step one, a precipitation method is used, where sodium hydroxide is added dropwise to a magnesium nitrate solution under stirring; the concentration of the magnesium nitrate solution is 1–5 mol / L, and the concentration of the sodium hydroxide solution is 1–5 mol / L. The obtained precipitate is washed with 1500 ml of deionized water and then dried at 80°C. In step two, the powdered magnesium hydroxide precursor obtained in step one is dispersed in deionized water, and a ruthenium chloride solution is added dropwise to the magnesium hydroxide suspension under stirring, where the concentration of ruthenium chloride is 1 g–5 g / L. After the addition is complete, the suspension is washed with 2000 ml of deionized water and dried at 60°C to obtain magnesium hydroxide. Magnesium-supported ruthenium precursor; in step three, the dried magnesium hydroxide-supported ruthenium precursor is dispersed in deionized water, and potassium hydroxide solution is added dropwise under stirring; potassium additive is introduced; after the dropwise addition is completed, rotary evaporation drying is performed, wherein the rotary evaporation drying temperature is 60-80℃ and the rotation speed is 60-80 r / min, to obtain magnesium hydroxide-supported potassium ruthenium precursor; in step four, the obtained magnesium hydroxide-supported potassium ruthenium precursor is calcined in an argon or air environment, the calcination temperature is 500-600℃ and the calcination time is 30 minutes; after calcination, the magnesium hydroxide-supported ruthenium precursor is reduced in a hydrogen atmosphere; the reduction temperature is 500-600℃ and the reduction time is 30 minutes.

[0021] The present invention will be further described below with reference to specific embodiments and accompanying drawings. Unless otherwise specified, all figures appearing in the specification and claims of this invention, such as active components, temperature and time, gas conversion rates, etc., should not be construed as absolutely precise values. Due to the standard deviation of measurement techniques, the measured values ​​inevitably contain a certain degree of experimental error. The above content will be further described below with reference to embodiments. It should be noted that these specific embodiments listed in this invention are only illustrative of the invention and are not intended to limit the above content of the invention in any way.

[0022] Example 1: Step 1: Dissolve 51.2820 g of Mg(NO3)2·6H2O in 200 mL of deionized water to prepare a 1 mol / L magnesium nitrate solution. Dissolve 16 g of NaOH in 400 mL of deionized water to prepare a 1 mol / L sodium hydroxide solution. Add the sodium hydroxide solution dropwise to the magnesium nitrate solution under magnetic stirring. After the addition is complete, filter the resulting precipitate. Wash the obtained precipitate with 1500 mL of deionized water and dry it at 80 °C. After drying, grind it into powder to obtain the magnesium hydroxide precursor. Step 2: Dissolve 0.5544 g RuCl3·H2O in 210 mL of deionized water to prepare a 1 g / L ruthenium chloride solution; disperse 9.8247 g of magnesium hydroxide precursor in deionized water with stirring at room temperature; add 210 mL of ruthenium chloride solution dropwise to the magnesium hydroxide suspension under magnetic stirring; after the addition is complete, filter and wash the filtered product with 2000 mL of deionized water to remove chloride-containing compounds generated during the addition process; dry at 60 °C after washing to obtain magnesium hydroxide-supported ruthenium precursor; Step 3: Dissolve 0.0042 g KOH in 10 mL of deionized water to prepare a 0.42 g / L (0.0075 mol / L) potassium hydroxide solution; disperse 0.7216 g of magnesium hydroxide-supported ruthenium precursor in deionized water; add 10 mL of potassium hydroxide solution dropwise under magnetic stirring; and rotary evaporate the magnesium hydroxide-supported ruthenium precursor dispersion containing potassium hydroxide at 60 r / min and 60 °C to obtain magnesium hydroxide-supported potassium ruthenium precursor. Step 4: The obtained magnesium hydroxide-supported potassium ruthenium precursor was calcined in an argon atmosphere at a temperature of 500°C for 30 minutes. After calcination, the magnesium hydroxide-supported potassium ruthenium precursor was reduced in a hydrogen atmosphere at a temperature of 500°C for 30 minutes to obtain a highly active potassium ruthenium catalyst (labeled as 0.5K-3%Ru / MgO).

[0023] Figure 1This is the X-ray powder diffraction pattern of the catalyst, located at 2. θ The diffraction peaks at 43.2°, 50.3°, 73.8°, 89.6°, and 94.7° correspond to the (111), (200), (220), (311), and (222) crystal planes of MgO, respectively. In 2... θ The absence of obvious ruthenium diffraction peaks around 44.9° and 51.6° indicates that the ruthenium metal is in a highly dispersed state.

[0024] Example 2: Step 1: Dissolve 51.2820 g of Mg(NO3)2·6H2O in 200 mL of deionized water to prepare a 1 mol / L magnesium nitrate solution. Dissolve 16 g of NaOH in 400 mL of deionized water to prepare a 1 mol / L sodium hydroxide solution. Add the sodium hydroxide solution dropwise to the magnesium nitrate solution under magnetic stirring. After the addition is complete, filter the resulting precipitate. Wash the obtained precipitate with 1500 mL of deionized water and dry it at 80 °C. After drying, grind it into powder to obtain the magnesium hydroxide precursor. Step 2: Dissolve 0.5544 g RuCl3·H2O in 210 mL of deionized water to prepare a 1 g / L ruthenium chloride solution; disperse 9.8247 g of magnesium hydroxide precursor in deionized water with stirring at room temperature; add 210 mL of ruthenium chloride solution dropwise to the magnesium hydroxide suspension under magnetic stirring; after the addition is complete, filter and wash the filtered product with 2000 mL of deionized water to remove chloride-containing compounds generated during the addition process; dry at 60 °C after washing to obtain magnesium hydroxide-supported ruthenium precursor; Step 3: Dissolve 0.0083 g KOH in 10 mL of deionized water to prepare a 0.83 g / L (0.0148 mol / L) potassium hydroxide solution; disperse 0.7216 g of magnesium hydroxide-supported ruthenium precursor in deionized water; add 10 mL of potassium hydroxide solution dropwise under magnetic stirring; and rotary evaporate the magnesium hydroxide-supported ruthenium precursor dispersion containing potassium hydroxide at 60 r / min and 60 °C to obtain magnesium hydroxide-supported potassium ruthenium precursor. Step 4: The obtained magnesium hydroxide-supported potassium ruthenium precursor was calcined in an argon atmosphere at a temperature of 500°C for 30 minutes. After calcination, the magnesium hydroxide-supported potassium ruthenium precursor was reduced in a hydrogen atmosphere at a temperature of 500°C for 30 minutes to obtain a highly active potassium ruthenium catalyst (labeled as 1K-3%Ru / MgO).

[0025] Figure 2 This is the X-ray powder diffraction pattern of the catalyst, located at 2. θThe diffraction peaks at 43.2°, 50.3°, 73.8°, 89.6°, and 94.7° correspond to the (111), (200), (220), (311), and (222) crystal planes of MgO, respectively. In 2... θ The absence of obvious ruthenium diffraction peaks around 44.9° and 51.6° indicates that the ruthenium metal is in a highly dispersed state. Figure 3 This is a high-angle annular dark-field scanning transmission electron microscope image of the catalyst, which shows that ruthenium metal nanoparticles are uniformly dispersed on the surface of the support, with an average particle size of 2.5 nm. Figure 4 and Figure 5 The images show the Cl 2p X-ray photoelectron spectra of the precursor and catalyst, respectively. No obvious Cl peak was observed, indicating that the chlorine content is very low or non-existent.

[0026] Figure 13 This is a graph showing the ammonia conversion rate of the catalyst in Example 2 as a function of reaction temperature. The ammonia conversion rate increases with increasing reaction temperature, reaching 97.1% at 450 °C. At 400 °C, the ammonia conversion rate is 64.4%, and the hydrogen production rate is 21.6 mmol-H₂ g. cat -1 min -1 It is higher than that of most catalysts reported in the literature. Figure 14 The results show the long-term stability test of the catalyst in Example 2 during the ammonia decomposition reaction at 475 °C. During the 100 h reaction period, the ammonia conversion rate remained constant at 96%, demonstrating excellent long-term stability.

[0027] Example 3: Step 1: Dissolve 51.2820 g of Mg(NO3)2·6H2O in 200 mL of deionized water to prepare a 1 mol / L magnesium nitrate solution. Dissolve 16 g of NaOH in 400 mL of deionized water to prepare a 1 mol / L sodium hydroxide solution. Add the sodium hydroxide solution dropwise to the magnesium nitrate solution under magnetic stirring. After the addition is complete, filter the resulting precipitate. Wash the obtained precipitate with 1500 mL of deionized water and dry it at 80 °C. After drying, grind it into powder to obtain the magnesium hydroxide precursor. Step 2: Dissolve 0.5544 g RuCl3·H2O in 210 mL of deionized water to prepare a 1 g / L ruthenium chloride solution; disperse 9.8247 g of magnesium hydroxide precursor in deionized water with stirring at room temperature; add 210 mL of ruthenium chloride solution dropwise to the magnesium hydroxide suspension under magnetic stirring; after the addition is complete, filter and wash the filtered product with 2000 mL of deionized water to remove chloride-containing compounds generated during the addition process; dry at 60 °C after washing to obtain magnesium hydroxide-supported ruthenium precursor; Step 3: Dissolve 0.0167 g KOH in 10 mL of deionized water to prepare a 1.67 g / L (0.0298 mol / L) potassium hydroxide solution; disperse 0.7216 g of magnesium hydroxide-supported ruthenium precursor in deionized water; add 10 mL of potassium hydroxide solution dropwise under magnetic stirring; and dry the magnesium hydroxide-supported ruthenium precursor dispersion containing potassium hydroxide by rotary evaporation at 60 r / min and 60 °C to obtain magnesium hydroxide-supported potassium ruthenium precursor. Step 4: The obtained magnesium hydroxide-supported potassium ruthenium precursor was calcined in an argon atmosphere at a temperature of 500°C for 30 minutes. After calcination, the magnesium hydroxide-supported potassium ruthenium precursor was reduced in a hydrogen atmosphere at a temperature of 500°C for 30 minutes to obtain a highly active potassium ruthenium catalyst (labeled as 2K-3%Ru / MgO).

[0028] Figure 6 This is the X-ray powder diffraction pattern of the catalyst, located at 2. θ The diffraction peaks at 43.2°, 50.3°, 73.8°, 89.6°, and 94.7° correspond to the (111), (200), (220), (311), and (222) crystal planes of MgO, respectively. In 2... θ The absence of obvious ruthenium diffraction peaks around 44.9° and 51.6° indicates that the ruthenium metal is in a highly dispersed state.

[0029] Example 4: Step 1: Dissolve 51.2820 g of Mg(NO3)2·6H2O in 200 mL of deionized water to prepare a 1 mol / L magnesium nitrate solution. Dissolve 16 g of NaOH in 400 mL of deionized water to prepare a 1 mol / L sodium hydroxide solution. Add the sodium hydroxide solution dropwise to the magnesium nitrate solution under magnetic stirring. After the addition is complete, filter the resulting precipitate. Wash the obtained precipitate with 1500 mL of deionized water and dry it at 80 °C. After drying, grind it into powder to obtain the magnesium hydroxide precursor. Step 2: Dissolve 0.1848 g RuCl3·H2O in 70 mL of deionized water to prepare a 1 g / L ruthenium chloride solution; disperse 10.0273 g of magnesium hydroxide precursor in deionized water with stirring at room temperature; add 70 mL of ruthenium chloride solution dropwise to the magnesium hydroxide suspension under magnetic stirring; after the addition is complete, filter and wash the filtered product with 2000 mL of deionized water to remove chloride-containing compounds generated during the addition process; dry at 60 °C after washing to obtain magnesium hydroxide-supported ruthenium precursor; Step 3: Dissolve 0.0028 g KOH in 10 mL of deionized water to prepare a 0.28 g / L (0.0050 mol / L) potassium hydroxide solution; disperse 0.7360 g of magnesium hydroxide-supported ruthenium precursor in deionized water; add 10 mL of potassium hydroxide solution dropwise under magnetic stirring; dry the magnesium hydroxide-supported ruthenium precursor dispersion containing potassium hydroxide by rotary evaporation at 60 r / min and 60 °C to obtain magnesium hydroxide-supported potassium ruthenium precursor. Step 4: The obtained magnesium hydroxide-supported potassium ruthenium precursor was calcined in an argon atmosphere at a temperature of 500°C for 30 minutes. After calcination, the magnesium hydroxide-supported potassium ruthenium precursor was reduced in a hydrogen atmosphere at a temperature of 500°C for 30 minutes to obtain a highly active potassium ruthenium catalyst (labeled as 1K-1%Ru / MgO).

[0030] Figure 7 This is the X-ray powder diffraction pattern of the catalyst, located at 2. θ The diffraction peaks at 43.2°, 50.3°, 73.8°, 89.6°, and 94.7° correspond to the (111), (200), (220), (311), and (222) crystal planes of MgO, respectively. In 2... θ The absence of obvious ruthenium diffraction peaks around 44.9° and 51.6° indicates that the ruthenium metal is in a highly dispersed state.

[0031] Example 5: Step 1: Dissolve 51.2820 g of Mg(NO3)2·6H2O in 200 mL of deionized water to prepare a 1 mol / L magnesium nitrate solution. Dissolve 16 g of NaOH in 400 mL of deionized water to prepare a 1 mol / L sodium hydroxide solution. Add the sodium hydroxide solution dropwise to the magnesium nitrate solution under magnetic stirring. After the addition is complete, filter the resulting precipitate. Wash the obtained precipitate with 1500 mL of deionized water and dry it at 80 °C. After drying, grind it into powder to obtain the magnesium hydroxide precursor. Step 2: Dissolve 0.3696 g RuCl3·H2O in 140 mL of deionized water to prepare a 1 g / L ruthenium chloride solution; disperse 9.9260 g of magnesium hydroxide precursor in deionized water with stirring at room temperature; add 140 mL of ruthenium chloride solution dropwise to the magnesium hydroxide suspension under magnetic stirring; after the addition is complete, filter and wash the filtered product with 2000 mL of deionized water to remove chloride-containing compounds generated during the addition process; dry at 60 °C after washing to obtain magnesium hydroxide-supported ruthenium precursor; Step 3: Dissolve 0.0056 g KOH in 10 mL of deionized water to prepare a 0.56 g / L (0.0100 mol / L) potassium hydroxide solution; disperse 0.7288 g of magnesium hydroxide-supported ruthenium precursor in deionized water; add 10 mL of potassium hydroxide solution dropwise under magnetic stirring; and rotary evaporate the magnesium hydroxide-supported ruthenium precursor dispersion containing potassium hydroxide at 60 r / min and 60 °C to obtain magnesium hydroxide-supported potassium ruthenium precursor. Step 4: The obtained magnesium hydroxide-supported potassium ruthenium precursor was calcined in an argon atmosphere at a temperature of 500°C for 30 minutes. After calcination, the magnesium hydroxide-supported potassium ruthenium precursor was reduced in a hydrogen atmosphere at a temperature of 500°C for 30 minutes to obtain a highly active potassium ruthenium catalyst (labeled as 1K-2%Ru / MgO).

[0032] Figure 8 This is the X-ray powder diffraction pattern of the catalyst, located at 2. θ The diffraction peaks at 43.2°, 50.3°, 73.8°, 89.6°, and 94.7° correspond to the (111), (200), (220), (311), and (222) crystal planes of MgO, respectively. In 2... θ The absence of obvious ruthenium diffraction peaks around 44.9° and 51.6° indicates that the ruthenium metal is in a highly dispersed state.

[0033] Example 6: Step 1: Dissolve 51.2820 g of Mg(NO3)2·6H2O in 200 mL of deionized water to prepare a 1 mol / L magnesium nitrate solution. Dissolve 16 g of NaOH in 400 mL of deionized water to prepare a 1 mol / L sodium hydroxide solution. Add the sodium hydroxide solution dropwise to the magnesium nitrate solution under magnetic stirring. After the addition is complete, filter the resulting precipitate. Wash the obtained precipitate with 1500 mL of deionized water and dry it at 80 °C. After drying, grind it into powder to obtain the magnesium hydroxide precursor. Step 2: Dissolve 0.5544 g RuCl3·H2O in 210 mL of deionized water to prepare a 1 g / L ruthenium chloride solution; disperse 9.8247 g of magnesium hydroxide precursor in deionized water with stirring at room temperature; add 210 mL of ruthenium chloride solution dropwise to the magnesium hydroxide suspension under magnetic stirring; after the addition is complete, filter and wash the filtered product with 2000 mL of deionized water to remove chloride-containing compounds generated during the addition process; dry at 60 °C after washing to obtain magnesium hydroxide-supported ruthenium precursor; Step 3: Dissolve 0.0083 g KOH in 10 mL of deionized water to prepare a 0.83 g / L (0.0148 mol / L) potassium hydroxide solution; disperse 0.7216 g of magnesium hydroxide-supported ruthenium precursor in deionized water; add 10 mL of potassium hydroxide solution dropwise under magnetic stirring; and rotary evaporate the magnesium hydroxide-supported ruthenium precursor dispersion containing potassium hydroxide at 60 r / min and 60 °C to obtain magnesium hydroxide-supported potassium ruthenium precursor. Step 4: The obtained magnesium hydroxide-supported potassium ruthenium precursor is calcined in air at a temperature of 500°C for 30 minutes. After calcination, the magnesium hydroxide-supported potassium ruthenium precursor is reduced in a hydrogen atmosphere at a temperature of 500°C for 30 minutes to obtain a highly active potassium ruthenium catalyst (labeled as 1K-3%Ru / MgO-air).

[0034] Figure 9 This is the X-ray powder diffraction pattern of the catalyst, located at 2. θ The diffraction peaks at 43.2°, 50.3°, 73.8°, 89.6°, and 94.7° correspond to the (111), (200), (220), (311), and (222) crystal planes of MgO, respectively. In 2... θ The absence of obvious ruthenium diffraction peaks around 44.9° and 51.6° indicates that the ruthenium metal is in a highly dispersed state.

[0035] Comparative Example 1 Step 1: Dissolve 51.2820 g of Mg(NO3)2·6H2O in 200 mL of deionized water to prepare a 1 mol / L magnesium nitrate solution. Dissolve 16 g of NaOH in 400 mL of deionized water to prepare a 1 mol / L sodium hydroxide solution. Add the sodium hydroxide solution dropwise to the magnesium nitrate solution under magnetic stirring. After the addition is complete, filter the resulting precipitate. Wash the obtained precipitate with 1500 mL of deionized water and dry it at 80 °C. After drying, grind it into powder to obtain the magnesium hydroxide precursor. Step 2: Dissolve 0.5544 g RuCl3·H2O in 210 mL of deionized water to prepare a 1 g / L ruthenium chloride solution; disperse 9.8247 g of magnesium hydroxide precursor in deionized water with stirring at room temperature; add 210 mL of ruthenium chloride solution dropwise to the magnesium hydroxide suspension under magnetic stirring; after the addition is complete, filter and wash the filtered product with 2000 mL of deionized water to remove chloride-containing compounds generated during the addition process; dry at 60 °C after washing to obtain magnesium hydroxide-supported ruthenium precursor; Step 3: The obtained magnesium hydroxide-supported potassium ruthenium precursor was calcined in air at a temperature of 500°C for 30 minutes. After calcination, the magnesium hydroxide-supported potassium ruthenium precursor was reduced in a hydrogen atmosphere at a temperature of 500°C for 30 minutes to obtain a ruthenium catalyst (labeled as 3%Ru / MgO).

[0036] Figure 10 This is the X-ray powder diffraction pattern of the catalyst, located at 2. θ The diffraction peaks at 43.2°, 50.3°, 73.8°, 89.6°, and 94.7° correspond to the (111), (200), (220), (311), and (222) crystal planes of MgO, respectively. In 2... θ The absence of obvious ruthenium diffraction peaks around 44.9° and 51.6° indicates that the ruthenium metal is in a highly dispersed state.

[0037] Comparative Example 2 Step 1: Dissolve 51.2820 g of Mg(NO3)2·6H2O in 200 mL of deionized water to prepare a 1 mol / L magnesium nitrate solution. Dissolve 16 g of NaOH in 400 mL of deionized water to prepare a 1 mol / L sodium hydroxide solution. Add the sodium hydroxide solution dropwise to the magnesium nitrate solution under magnetic stirring. After the addition is complete, filter the resulting precipitate. Wash the obtained precipitate with 1500 mL of deionized water and dry it at 80 °C. After drying, grind it into powder to obtain the magnesium hydroxide precursor. Step 2: Dissolve 0.5544 g RuCl3·H2O in 210 mL of deionized water to prepare a 1 g / L ruthenium chloride solution; disperse 9.8247 g of magnesium hydroxide precursor in deionized water with stirring at room temperature; add 210 mL of ruthenium chloride solution dropwise to the magnesium hydroxide suspension under magnetic stirring; after the addition is complete, filter and wash the filtered product with 2000 mL of deionized water to remove chloride-containing compounds generated during the addition process; dry at 60 °C after washing to obtain magnesium hydroxide-supported ruthenium precursor; Step 3: The obtained magnesium hydroxide-supported potassium ruthenium precursor was calcined in air at a temperature of 500°C for 30 minutes. After calcination, the magnesium hydroxide-supported potassium ruthenium precursor was reduced in a hydrogen atmosphere at a temperature of 500°C for 30 minutes to obtain the ruthenium catalyst (labeled as 3%Ru / MgO-air).

[0038] Figure 11 This is the X-ray powder diffraction pattern of the catalyst, located at 2. θThe diffraction peaks at 43.2°, 50.3°, 73.8°, 89.6°, and 94.7° correspond to the (111), (200), (220), (311), and (222) crystal planes of MgO, respectively. In 2... θ The absence of obvious ruthenium diffraction peaks around 44.9° and 51.6° indicates that the ruthenium metal is in a highly dispersed state.

[0039] Comparative Example 3 Step 1: Dissolve 51.2820 g of Mg(NO3)2·6H2O in 200 mL of deionized water to prepare a 1 mol / L magnesium nitrate solution. Dissolve 16 g of NaOH in 400 mL of deionized water to prepare a 1 mol / L sodium hydroxide solution. Add the sodium hydroxide solution dropwise to the magnesium nitrate solution under magnetic stirring. After the addition is complete, filter the resulting precipitate. Wash the obtained precipitate with 1500 mL of deionized water and dry it at 80 °C. After drying, grind it into powder to obtain the magnesium hydroxide precursor. Step 2: Dissolve 0.5544 g RuCl3·H2O in 210 mL of deionized water to prepare a 1 g / L ruthenium chloride solution; disperse 9.8247 g of magnesium hydroxide precursor in deionized water with stirring at room temperature; add 210 mL of ruthenium chloride solution dropwise to the magnesium hydroxide suspension under magnetic stirring; after the addition is complete, filter and wash the filtered product with 2000 mL of deionized water to remove chloride-containing compounds generated during the addition process; dry at 60 °C after washing to obtain magnesium hydroxide-supported ruthenium precursor; Step 3: Dissolve 0.0083 g KOH in 10 mL ethanol to prepare a 0.83 g / L (0.0148 mol / L) potassium hydroxide solution; disperse 0.7216 g of magnesium hydroxide-supported ruthenium precursor in deionized water; calcine the obtained magnesium hydroxide-supported ruthenium precursor under argon atmosphere at 500℃ for 30 minutes; after calcine, reduce the magnesium hydroxide-supported ruthenium precursor under hydrogen atmosphere at 500℃ for 30 minutes to obtain magnesium oxide-supported ruthenium catalyst. Step 4: Disperse the magnesium oxide-supported ruthenium catalyst in an ethanol solution. Add 10 ml of potassium hydroxide dropwise while stirring. Dry the magnesium hydroxide-supported ruthenium precursor dispersion by rotary evaporation at 60 r / min and 60 °C to remove the solution. Then, calcine at 500 °C under an argon atmosphere for 30 minutes, and then reduce with hydrogen at 500 °C for 30 minutes to obtain the magnesium oxide-supported potassium ruthenium catalyst (labeled as 1K / 3%Ru / MgO).

[0040] Figure 12 This is the X-ray powder diffraction pattern of the catalyst, located at 2. θ The diffraction peaks at 43.2°, 50.3°, 73.8°, 89.6°, and 94.7° correspond to the (111), (200), (220), (311), and (222) crystal planes of MgO, respectively. In 2... θ The presence of relatively obvious ruthenium metal diffraction peaks at around 44.9° and 51.6° indicates that ruthenium metal agglomeration occurred during the introduction of potassium additive using the post-impregnation method, resulting in an increase in the particle size of Ru metal.

[0041] The activity evaluation of the catalyst for ammonia decomposition was carried out in a fixed-bed reactor at atmospheric pressure. The reaction conditions were: 50 mg catalyst, pure ammonia as feed gas, flow rate of 25 mL / min, and space velocity of 30,000 mL / (g). cat The reaction conditions were: reaction pressure at atmospheric pressure and reaction temperature at 250–550 °C; stability test conditions: catalyst 50 mg, feed gas was pure ammonia, flow rate 50 mL / min, space velocity 60,000 mL / (g) cat •h), the reaction pressure was atmospheric pressure, and the reaction temperature was 475 °C. Table 1 shows the ammonia decomposition activity test results of the catalysts in Examples 1-6 and Comparative Examples 1-3 under the above reaction conditions: Table 1. Ammonia decomposition activity of ruthenium catalysts Comparing the catalysts of Examples 1-3 and Comparative Example 1, it can be seen that the addition of K promoter significantly improved the activity of the 3%Ru / MgO catalyst, with the best activity observed when the K / Ru molar ratio was 1-2. The ammonia conversion rates of the 1K-3%Ru / MgO and 2K-3%Ru / MgO catalysts at 400 °C were 2.1 and 2.2 times that of the 3%Ru / MgO catalyst, respectively, demonstrating excellent promoting effects. Examples 2, 4, and 5 show that the ammonia conversion rate increases with increasing Ru content, with the 3% Ru content exhibiting the best activity. Comparing Examples 2 and 6, it can be seen that the activity of the 1K-3%Ru / MgO catalyst is comparable regardless of whether it is calcined in an Ar atmosphere or in air. Comparing Example 6 and Comparative Example 2, it can be seen that the activity of the 1K-3%Ru / MgO obtained by air calcination is significantly higher than that of the 3%Ru / MgO obtained by air calcination. Comparing Example 2 and Comparative Example 3, it can be seen that, with the same ruthenium and potassium content, the 1K-3%Ru / MgO catalyst prepared by the method of the present invention has higher activity than the 1K / 3%Ru / MgO catalyst prepared by the post-impregnation method, indicating that it has better metal-catalyst interaction.

[0042] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a highly active potassium ruthenium catalyst, characterized in that: Includes the following steps: Step 1: Add sodium hydroxide solution dropwise to magnesium nitrate solution while stirring; After the addition is complete, the resulting precipitate is filtered; the obtained precipitate is washed, dried and ground into powder. Magnesium hydroxide precursor was obtained; Step 2: Disperse the magnesium hydroxide precursor in deionized water by stirring at room temperature; Then add ruthenium chloride dropwise to the magnesium hydroxide suspension; After the addition was completed, the mixture was filtered and the filtered product was washed to remove compounds containing chloride ions generated during the addition process; after drying, magnesium hydroxide-supported ruthenium precursor was obtained. Step 3: Disperse the obtained magnesium hydroxide-supported ruthenium precursor in deionized water; The potassium hydroxide solution was added dropwise under stirring; the magnesium hydroxide-supported ruthenium precursor dispersion containing potassium hydroxide was dried by rotary evaporation to obtain the magnesium hydroxide-supported potassium ruthenium precursor. Step 4: Calcining the obtained magnesium hydroxide-supported potassium ruthenium precursor; After calcination, the magnesium hydroxide-supported potassium ruthenium precursor was reduced under a hydrogen atmosphere to obtain a highly active potassium ruthenium catalyst.

2. The method for preparing a highly active potassium ruthenium catalyst according to claim 1, characterized in that: In step one, the concentration of the magnesium nitrate solution is 1-5 mol / L; the concentration of the sodium hydroxide solution is 1-5 mol / L; the precipitate is washed with 1500 ml of deionized water and dried at 60°C.

3. The method for preparing a highly active potassium ruthenium catalyst according to claim 1, characterized in that: In step two, the concentration of the magnesium nitrate solution is 1-5 mol / L; the concentration of the sodium hydroxide solution is 1-5 mol / L; the precipitate is washed with 1500 ml of deionized water and dried at 60°C.

4. The method for preparing a highly active potassium ruthenium catalyst according to claim 1, characterized in that: In step three, the magnesium hydroxide-supported ruthenium precursor dispersion containing potassium hydroxide is subjected to rotary evaporation drying at 60–80 °C and 60–80 r / min.

5. The method for preparing a highly active potassium ruthenium catalyst according to claim 1, characterized in that: In step four, the obtained magnesium hydroxide-supported ruthenium hydroxide precursor is calcined in an argon or air atmosphere at a temperature of 500–600°C for 30 minutes. After calcination, the magnesium hydroxide-supported ruthenium hydroxide precursor is reduced in a hydrogen atmosphere at a temperature of 500–600°C for 30 minutes.

6. A highly active potassium ruthenium catalyst, characterized in that: It is prepared by the preparation method of a highly active potassium-ruthenium catalyst according to any one of claims 1 to 5; the mass content of ruthenium metal is 1 to 3%; the molar ratio of potassium to ruthenium is 0.5 to 2.

7. The application of a highly active potassium ruthenium catalyst, characterized in that: Used for hydrogen production from ammonia decomposition.

Images