An integral structured ammonia decomposition catalyst with a coating and a method for producing the same

Abstract

The application discloses a whole structure type ammonia decomposition catalyst containing a coating and a preparation method thereof, and comprises the following steps: step one, selecting a magnesium oxide or magnesium-aluminum spinel carrier, mixing the carrier with water to form a mixed solution; then ball milling the mixed solution to obtain a colloidal spraying solution; step two, spraying the obtained colloidal spraying solution on the surface of a carrier made of nickel, stainless steel or cordierite; step three, drying the carrier containing the colloidal spraying solution and placing the carrier in an environment above 400 DEG C for calcination; step four, immersing the calcined carrier in a colloidal solution containing a ruthenium salt, the mass fraction of ruthenium metal in the colloidal solution being 0.5-5%, until the content of ruthenium on the surface of the carrier reaches 5-20 g / L, and then taking out and drying. The ammonia decomposition catalyst prepared by the preparation method has good thermal stability and ammonia decomposition activity, and the ammonia decomposition activity can be maintained at 99.5% under high space velocity; the preparation method improves the dispersion degree of noble metal in the catalyst and prolongs the service life of the catalyst.

Description

Technical Field

[0001] This invention relates to the field of clean energy equipment technology, specifically to an ammonia decomposition catalyst with an integral structure containing an internal coating and containing both nickel-based and ruthenium-based components, and its preparation method. Background Technology

[0002] Ammonia is not only an important inorganic chemical product, but it also has unique advantages as a hydrogen carrier. Ammonia is easily liquefied, has a pungent odor, is non-flammable and non-toxic at low concentrations, has high hydrogen storage density, and its production, storage, and transportation technologies are mature. Furthermore, hydrogen production is carbon-free, making it a highly efficient, clean, and safe hydrogen carrier. Producing hydrogen by decomposing ammonia is also a feasible and effective hydrogen production technology. Current publicly available information shows that the Ru-based catalyst with the best ammonia decomposition reaction activity uses graphitized carbon as its support. However, carbon supports may undergo methanation reactions at temperatures above 500°C in a hydrogen atmosphere, resulting in poor thermal stability. Existing commercially available Ni-based ammonia decomposition catalysts use alumina as their support, exhibiting a high activity temperature range, typically reaching 820°C, but with poor activity at low temperatures. Long-term use can lead to increased resistance due to pulverization, and the ammonia decomposition activity is low at high space velocities.

[0003] Chinese patent CN102476052A discloses a supported ruthenium catalyst and its preparation method. The method involves first selecting a soluble alkaline earth metal salt, such as alumina, as a support, with the mass of the soluble alkaline earth metal salt being 0.1-20% of the support. Ruthenium is used as the main active component, and one or more of nickel, cobalt, palladium, and platinum are used as co-catalyst components. Ruthenium and any one of nickel, cobalt, palladium, and platinum are coated onto the support using an impregnation or spraying method. After coating, the catalyst precursor is dried, and then a reduction reaction is performed using the dried catalyst precursor to obtain the supported ruthenium catalyst. Although the supported ruthenium ammonia decomposition catalyst prepared by this method exhibits high activity, its activity is poor at high space velocities and low temperatures, failing to meet the requirements for catalyst activity and stability under ammonia decomposition conditions. Summary of the Invention

[0004] To address the shortcomings of existing ruthenium-containing nickel-based ammonia decomposition catalysts, such as high active temperature range and operating temperature, poor low-temperature activity, and increased resistance due to pulverization during long-term use, as well as low ammonia decomposition activity at high space velocities, which fail to meet the activity and stability requirements of catalysts under ammonia decomposition conditions, this paper proposes a coated, integrally structured ammonia decomposition catalyst with a high specific surface area, high low-temperature ammonia synthesis activity at high space velocities, and improved ruthenium metal dispersion and thermal stability. This catalyst can meet the requirements for catalyst activity, stability, and service life under ammonia decomposition conditions.

[0005] The technical solution adopted by this invention to solve its technical problem is: a method for preparing an integrally structured ammonia decomposition catalyst with a coating, comprising the following steps: Step 1: Selecting a magnesium oxide or magnesium aluminum spinel support, mixing it with water to form a mixture; then ball milling the mixture to obtain a colloidal spraying liquid; Step 2: Spraying the obtained colloidal spraying liquid onto the surface of a support made of nickel, stainless steel, or cordierite; Step 3: Drying the support containing the colloidal spraying liquid and calcining it in an environment above 400°C; Step 4: Immersing the calcined support containing the colloidal spraying layer in a colloid containing ruthenium salt, wherein the mass fraction of ruthenium metal in the colloid containing ruthenium salt is 0.5-5%, until the ruthenium content on the surface of the support reaches 5-20 g / L; after immersion, removing the support containing the colloidal spraying layer from the colloid and drying it; thus obtaining an integrally structured ammonia decomposition catalyst with a coating.

[0006] Furthermore, in step one, alumina or magnesium aluminum spinel and water are mixed in a ratio of 1:1 to 1:3 to form a mixture, and then an additive is added to the mixture before grinding.

[0007] Furthermore, the additives are β-molecular sieve and aluminum nitrate, with the mass fraction of the additives being 10-50% of the mixture.

[0008] Furthermore, in step one, the ball milling time is 2 to 48 hours; the particle size range of the colloidal spray liquid is 1 to 50 μm.

[0009] Furthermore, in step two, when nickel or stainless steel is selected as the carrier, the nickel and stainless steel materials are first placed in an air or oxygen environment at 400-700°C for calcination; then the nickel or stainless steel carrier with nickel oxide on its surface is immersed in an acidic solution at an ambient temperature range of 30-60°C for at least 0.5 hours.

[0010] Furthermore, the carrier containing nickel oxide or stainless steel is immersed in hydrochloric acid with a concentration of 5-20%, nitric acid with a concentration of 5-40%, or sulfuric acid with a concentration of 5-40% for at least 0.5 hours.

[0011] Furthermore, in step three, the mass fraction of the colloidal spray liquid on the carrier containing the colloidal spray coating is 20–100 g / L.

[0012] Furthermore, in step four, the ruthenium metal salt solution is first mixed with alumina, and the mixture of ruthenium metal salt solution and alumina is ball-milled to form a mixed colloid containing ruthenium metal salt solution and alumina; ruthenium metal accounts for 2 to 10% of the mass of the mixed colloid.

[0013] This application also discloses an integral structured ammonia decomposition catalyst with a coating, comprising a support made of nickel, stainless steel or cordierite; the surface of the support is covered with a colloidal spray coating containing magnesium oxide or magnesium aluminum spinel, the colloidal spray coating containing ruthenium metal element, the ruthenium content on the colloidal spray coating being 5-20 g / L.

[0014] Furthermore, the thickness of the colloidal spray coating ranges from 0.5 to 1 mm.

[0015] This invention discloses a coated monolithic ammonia decomposition catalyst and its preparation method. The monolithic ammonia decomposition catalyst is prepared by coating a support surface with a layer of alumina or magnesium aluminum spinel containing a high specific surface area as a transition layer, followed by impregnation of ruthenium metal onto the coating. This method effectively improves the thermal stability and ammonia decomposition activity of the monolithic ammonia decomposition catalyst, maintaining an ammonia decomposition activity of 99.5% at high space velocities. It also improves the dispersion of precious metals in the catalyst, extending its lifespan. Furthermore, this preparation method uses a relatively low amount of precious metals, resulting in a high cost-performance ratio for the catalyst. 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 This is a process flow diagram of the preparation method of the monolithic ammonia decomposition catalyst according to the present invention. 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 Figure 1 As shown, the preparation method of the monolithic ammonia decomposition catalyst with coating according to the present invention includes the following steps:

[0020] Step 1: Select magnesium oxide or magnesium aluminum spinel carrier and mix it with water to form a mixture; then ball mill the mixture to obtain a colloidal spraying liquid;

[0021] Step 2: Spray the obtained colloidal coating liquid onto the surface of a carrier made of nickel, stainless steel or cordierite;

[0022] Step 3: Dry the carrier containing the colloidal spray liquid, and then bake it in an environment above 400°C;

[0023] Step 4: Immerse the calcined carrier containing the colloidal coating in a rubidium-containing colloid, wherein the mass fraction of ruthenium metal in the rubidium-containing colloid is 0.5-5%, until the ruthenium content on the surface of the carrier reaches 5-20 g / L; after immersion, remove the carrier containing the colloidal coating from the colloid and dry it; to obtain an integral structural ammonia decomposition catalyst with a coating.

[0024] In step one, specifically, a ball milling method is used to prepare the colloidal spraying solution: first, alumina or magnesium aluminum spinel carrier and water are mixed in a ratio of 1:1 to 1:3 to initially form a suspension. Then, additives, including β-molecular sieves and aluminum nitrate, are added to the initially formed suspension to improve the bonding strength between the subsequent colloidal spraying solution and the carrier, reducing the risk of cracking during use. More preferably, the mass fraction of the additives is 10-50% of the mixture. The additives are then mixed with oxygen... After mixing aluminum oxide or magnesium aluminum spinel to form a mixture, the resulting mixture is ball-milled for 2–48 hours to form a stable colloidal spraying solution. During the ball milling process, the viscosity of the colloid is controlled and the particle size is tested to determine whether the colloidal spraying solution meets the coating standard. The viscosity and particle size of the colloidal spraying solution are adjusted by changing the ball milling intensity and time. The particle size range of the colloidal spraying solution is between 1 and 50 μm, for example, 20 μm.

[0025] In step two, nickel, stainless steel, or cordierite is selected as the raw material for the carrier. When nickel or stainless steel is used to make the carrier, it needs to be chemically treated first. This includes the following steps: first, the nickel and stainless steel materials are placed in an air or oxygen environment at 400-700°C to form a nickel oxide surface with a high specific surface area on the surface of the nickel or stainless steel; then, the nickel or stainless steel carrier containing nickel oxide on the surface is immersed in an acidic solution, such as hydrochloric acid, sulfuric acid, or nitric acid, to remove part of the nickel oxide surface on the carrier, so that the surface of the nickel or stainless steel carrier exhibits a porous structure. Specifically, concentrated... The surface of a nickel or stainless steel substrate is acid-treated with hydrochloric acid (5-20%), nitric acid (5-40%), or sulfuric acid (5-40%) at an ambient temperature range of 30-60°C, resulting in the formation of a nickel oxide surface with a higher specific surface area. More specifically, the nickel or stainless steel substrate is immersed in an acidic solution for at least 0.5 hours to ensure that the nickel oxide surface on the nickel or stainless steel substrate has a sufficient specific surface area, for example, 5-20%. When cordierite is used as the raw material for the substrate, it can be used as a substrate without chemical treatment.

[0026] After completing the chemical treatment of the carrier, the colloidal spraying liquid prepared by mixing alumina or magnesium aluminum spinel carrier and additives obtained in step one is applied to the carrier by spraying, for example, alumina spraying, or by immersing the carrier in the colloidal spraying liquid prepared by mixing alumina or magnesium aluminum spinel carrier and additives, so that the surface of the carrier is covered with the colloidal spraying liquid.

[0027] In step three, to ensure that the colloidal spray liquid on the carrier surface can play its corresponding role, including improving the dispersion, thermal stability, and catalyst activity of the ruthenium catalyst, the carrier with the colloidal spray layer on its surface is dried after impregnation or spraying. After drying, the surface of the carrier is sprayed with colloidal spray liquid again or the carrier is impregnated in colloidal spray liquid. Then, the carrier with colloidal spray liquid on its surface is dried again. This process is repeated to increase the content of colloidal spray liquid on the carrier to achieve the target loading. This ensures that the colloidal spray liquid sprayed or impregnated on the carrier can play its corresponding role, while also improving the stability of the colloidal spray liquid layer and the activity of the catalyst. More specifically, the mass fraction of the colloidal spray liquid on the carrier surface is 20–100 g / L.

[0028] After drying the carrier containing the colloidal spray liquid on its surface, the carrier containing the colloidal spray layer is placed in an environment of 400-600℃ for calcination treatment; thereby further improving the stability of the colloidal spray liquid layer; providing a stable substrate for subsequent coating of ruthenium metal on the colloidal spray liquid layer, and forming a stable colloidal spray liquid layer on the carrier surface.

[0029] In step four, a ruthenium metal salt solution is first mixed with alumina, and the resulting mixture is then ball-milled to form a mixed colloid containing both ruthenium metal salt solution and alumina. To ensure sufficient ruthenium metal can be loaded onto the catalyst support, specifically, the ruthenium metal accounts for 2-10% of the mass of the mixed colloid. After forming the ruthenium-containing mixed colloid, the support, which has been dried and heat-treated in step three, is immersed in the mixed colloid containing 0.5-5% ruthenium metal for 0.5-3 hours, allowing the ruthenium metal in the mixed colloid to fully fill the colloid. A colloid coating is applied to the surface of the carrier. After impregnation, the carrier is removed from the mixed colloid and dried. Preferably, to ensure sufficient ruthenium metal on the carrier surface, after drying, the carrier is impregnated again in the mixed colloid for 0.5–3 hours. This process is repeated until the mass fraction of ruthenium metal on the carrier reaches 5–20 g / L. After impregnation, the carrier with the colloid coating is removed from the colloid and dried. This yields a monolithic ammonia decomposition catalyst with a coating.

[0030] This application also discloses a coated monolithic ammonia decomposition catalyst prepared by the method of preparing the coated monolithic ammonia decomposition catalyst, comprising a support made of nickel, stainless steel or cordierite; the surface of the support is covered with a colloidal sprayed layer containing magnesium oxide or magnesium aluminum spinel, and the colloidal sprayed layer is covered with a ruthenium metal film layer, wherein the ruthenium content on the colloidal sprayed layer is 5-20 g / L.

[0031] The thickness of the colloidal spray coating ranges from 0.5 to 1 mm; and the proportion of ruthenium metal is 0.5% to 5%.

[0032] Example 1

[0033] Step 1: Select magnesium oxide as the carrier of the colloidal spray liquid. Mix magnesium oxide and water in a 1:1 ratio to form a mixture. Add an additive containing β molecular sieve and aluminum nitrate to the mixture, wherein the mass fraction of the additive is 10% of the mixture. Ball mill the mixture containing magnesium oxide, water and additive for 2 hours, and control the particle size of the colloidal spray liquid to 1 μm; to obtain the colloidal spray liquid.

[0034] Step 2: Select a nickel-based carrier and calcine it in an air or oxygen environment at 400°C. After calcination, immerse the carrier in a 10% hydrochloric acid environment for 0.5 hours to obtain a specific surface area of ​​50 m². 2 / g of carrier; then the colloidal spraying liquid obtained in step one is sprayed on the carrier to form a colloidal spraying layer;

[0035] Step 3: Dry the carrier with the colloidal coating on its surface, and then bake it at 400℃.

[0036] Step 4: First, mix the ruthenium metal salt solution with alumina. After mixing, ball mill the mixture of ruthenium metal salt solution and alumina to obtain a mixed colloid containing ruthenium metal and alumina; wherein the mass fraction of ruthenium metal is controlled to be 0.5%. Immerse the carrier containing the colloidal coating after calcination in Step 3 in the colloid containing ruthenium salt for 0.5 hours. After immersion, remove the carrier containing the colloidal coating and dry it; thus, obtain the monolithic ammonia decomposition catalyst with coating.

[0037] Example 2

[0038] Step 1: Select magnesium oxide as the carrier of the colloidal spray liquid. Mix magnesium oxide and water in a 1:1 ratio to form a mixture. Add an additive containing β molecular sieve and aluminum nitrate to the mixture, wherein the mass fraction of the additive is 50% of the mixture. Ball mill the mixture containing magnesium oxide, water and additive for 2 hours, and control the particle size of the colloidal spray liquid to 1 μm; to obtain the colloidal spray liquid.

[0039] Step 2: Select a nickel-based carrier and calcine it in an air or oxygen environment at 400°C. After calcination, immerse the carrier in a 10% hydrochloric acid environment for 0.5 hours to obtain a specific surface area of ​​50 m². 2 / g of carrier; then the colloidal spraying liquid obtained in step one is sprayed on the carrier to form a colloidal spraying layer;

[0040] Step 3: Dry the carrier with the colloidal coating on its surface, and then bake it at 400℃.

[0041] Step 4: First, mix the ruthenium metal salt solution with alumina. After mixing, ball mill the mixture of ruthenium metal salt solution and alumina to obtain a mixed colloid containing ruthenium metal and alumina; wherein the mass fraction of ruthenium metal is controlled to be 0.5%. Immerse the carrier containing the colloidal coating after calcination in Step 3 in the colloid containing ruthenium salt for 0.5 hours. After immersion, remove the carrier containing the colloidal coating and dry it; thus, obtain the monolithic ammonia decomposition catalyst with coating.

[0042] Example 3

[0043] Step 1: Select magnesium oxide as the carrier of the colloidal spray liquid. Mix magnesium oxide and water in a 1:1 ratio to form a mixture. Add an additive containing β molecular sieve and aluminum nitrate to the mixture, wherein the mass fraction of the additive is 10% of the mixture. Ball mill the mixture containing magnesium oxide, water and additive for 2 hours, and control the particle size of the colloidal spray liquid to 1 μm; to obtain the colloidal spray liquid.

[0044] Step 2: Select a nickel-based support and calcine it in an air or oxygen environment at 400°C. After calcification, immerse the support in a 20% nitric acid environment for 0.5 hours to obtain a specific surface area of ​​50 m². 2 / g of carrier; then the colloidal spraying liquid obtained in step one is sprayed on the carrier to form a colloidal spraying layer;

[0045] Step 3: Dry the carrier with the colloidal coating on its surface, and then bake it at 400℃.

[0046] Step 4: First, mix the ruthenium metal salt solution with alumina. After mixing, ball mill the mixture of ruthenium metal salt solution and alumina to obtain a mixed colloid containing ruthenium metal and alumina; wherein the mass fraction of ruthenium metal is controlled to be 0.5%. Immerse the carrier containing the colloidal coating after calcination in Step 3 in the colloid containing ruthenium salt for 0.5 hours. After immersion, remove the carrier containing the colloidal coating and dry it; thus, obtain the monolithic ammonia decomposition catalyst with coating.

[0047] Example 4

[0048] Step 1: Select magnesium oxide as the carrier of the colloidal spray liquid. Mix magnesium oxide and water at a ratio of 1:1.5 to form a mixture. Add an additive containing β molecular sieve and aluminum nitrate to the mixture, wherein the mass fraction of the additive is 30% of the mixture. Ball mill the mixture containing magnesium oxide, water and additive for 10 hours, and control the particle size of the colloidal spray liquid to be 10 μm. The colloidal spray liquid is then obtained.

[0049] Step 2: Select a nickel-based carrier and calcine it in an air or oxygen environment at 500°C. After calcination, immerse the carrier in a 20% hydrochloric acid environment for 1 hour to obtain a specific surface area of ​​100 m². 2 / g of carrier; then the colloidal spraying liquid obtained in step one is sprayed on the carrier to form a colloidal spraying layer;

[0050] Step 3: Dry the carrier with the colloidal coating on its surface, and then bake it at 500℃.

[0051] Step 4: First, mix the ruthenium metal salt solution with alumina. After mixing, ball mill the mixture of ruthenium metal salt solution and alumina to obtain a mixed colloid containing ruthenium metal and alumina; wherein the mass fraction of ruthenium metal is controlled to be 2%. Immerse the carrier containing the colloidal coating obtained in Step 3 into the colloid containing ruthenium salt for 1 hour. After immersion, remove the carrier containing the colloidal coating and dry it; thus, obtain the monolithic ammonia decomposition catalyst with coating.

[0052] Example 5

[0053] Step 1: Select magnesium oxide as the carrier of the colloidal spray liquid. Mix magnesium oxide and water at a ratio of 1:1.5 to form a mixture. Add an additive containing β molecular sieve and aluminum nitrate to the mixture, wherein the mass fraction of the additive is 40% of the mixture. Ball mill the mixture containing magnesium oxide, water and additive for 10 hours, and control the particle size of the colloidal spray liquid to be 10 μm. The colloidal spray liquid is then obtained.

[0054] Step 2: Select a nickel-based carrier and calcine it in an air or oxygen environment at 500°C. After calcination, immerse the carrier in a 20% hydrochloric acid environment for 1 hour to obtain a specific surface area of ​​100 m². 2 / g of carrier; then the colloidal spraying liquid obtained in step one is sprayed on the carrier to form a colloidal spraying layer;

[0055] Step 3: Dry the carrier with the colloidal coating on its surface, and then bake it at 500℃.

[0056] Step 4: First, mix the ruthenium metal salt solution with alumina. After mixing, ball mill the mixture of ruthenium metal salt solution and alumina to obtain a mixed colloid containing ruthenium metal and alumina; wherein the mass fraction of ruthenium metal is controlled to be 2%. The carrier containing the colloidal coating after calcination in Step 3 is immersed in the colloid containing ruthenium salt for 1 hour. After immersion, the carrier containing the colloidal coating is taken out and dried; thus, an integral structural ammonia decomposition catalyst with coating is obtained.

[0057] Example 6

[0058] Step 1: Select magnesium oxide as the carrier of the colloidal spray liquid. Mix magnesium oxide and water at a ratio of 1:1.5 to form a mixture. Add an additive containing β molecular sieve and aluminum nitrate to the mixture, wherein the mass fraction of the additive is 30% of the mixture. Ball mill the mixture containing magnesium oxide, water and additive for 10 hours, and control the particle size of the colloidal spray liquid to be 10 μm. The colloidal spray liquid is then obtained.

[0059] Step 2: Select a nickel-based substrate and calcine it in an air or oxygen environment at 500°C. After calcination, immerse the substrate in a 40% sulfuric acid solution for 1 hour to obtain a specific surface area of ​​100 m². 2 / g of carrier; then the colloidal spraying liquid obtained in step one is sprayed on the carrier to form a colloidal spraying layer;

[0060] Step 3: Dry the carrier with the colloidal coating on its surface, and then bake it at 500℃.

[0061] Step 4: First, mix the ruthenium metal salt solution with alumina. After mixing, ball mill the mixture of ruthenium metal salt solution and alumina to obtain a mixed colloid containing ruthenium metal and alumina; wherein the mass fraction of ruthenium metal is controlled to be 2%. The carrier containing the colloidal coating after calcination in Step 3 is immersed in the colloid containing ruthenium salt for 1 hour. After immersion, the carrier containing the colloidal coating is taken out and dried; thus, an integral structural ammonia decomposition catalyst with coating is obtained.

[0062] Example 7

[0063] Step 1: Select magnesium oxide as the carrier of the colloidal spray liquid. Mix magnesium oxide and water in a 1:2 ratio to form a mixture. Add an additive containing β molecular sieve and aluminum nitrate to the mixture, wherein the mass fraction of the additive is 35% of the mixture. Ball mill the mixture containing magnesium oxide, water and additive for 20 hours, and control the particle size of the colloidal spray liquid to 5 μm. The colloidal spray liquid is then obtained.

[0064] Step 2: Select a nickel-based support and calcine it in an air or oxygen environment at 500°C. After calcification, immerse the support in a 10% nitric acid environment for 1 hour to obtain a specific surface area of ​​100 m². 2 / g of carrier; then the colloidal spraying liquid obtained in step one is sprayed on the carrier to form a colloidal spraying layer;

[0065] Step 3: Dry the carrier with the colloidal coating on its surface, and then bake it at 500℃.

[0066] Step 4: First, mix the ruthenium metal salt solution with alumina. After mixing, ball mill the mixture of ruthenium metal salt solution and alumina to obtain a mixed colloid containing ruthenium metal and alumina; wherein the mass fraction of ruthenium metal is controlled to be 3%. The carrier containing the colloidal coating after calcination in Step 3 is immersed in the colloid containing ruthenium salt for 1.5 hours. After immersion, the carrier containing the colloidal coating is taken out and dried; thus, an integral structural ammonia decomposition catalyst with coating is obtained.

[0067] Example 8

[0068] Step 1: Select magnesium oxide as the carrier of the colloidal spray liquid. Mix magnesium oxide and water in a 1:2 ratio to form a mixture. Add an additive containing β molecular sieve and aluminum nitrate to the mixture, wherein the mass fraction of the additive is 40% of the mixture. Ball mill the mixture containing magnesium oxide, water and additive for 20 hours, and control the particle size of the colloidal spray liquid to 5 μm. The colloidal spray liquid is then obtained.

[0069] Step 2: Select a nickel-based support and calcine it in an air or oxygen environment at 500°C. After calcification, immerse the support in a 10% nitric acid environment for 1 hour to obtain a specific surface area of ​​100 m². 2 / g of carrier; then the colloidal spraying liquid obtained in step one is sprayed on the carrier to form a colloidal spraying layer;

[0070] Step 3: Dry the carrier with the colloidal coating on its surface, and then bake it at 500℃.

[0071] Step 4: First, mix the ruthenium metal salt solution with alumina. After mixing, ball mill the mixture of ruthenium metal salt solution and alumina to obtain a mixed colloid containing ruthenium metal and alumina; wherein the mass fraction of ruthenium metal is controlled to be 3%. The carrier containing the colloidal coating after calcination in Step 3 is immersed in the colloid containing ruthenium salt for 1.5 hours. After immersion, the carrier containing the colloidal coating is taken out and dried; thus, an integral structural ammonia decomposition catalyst with coating is obtained.

[0072] Example 9

[0073] Step 1: Select magnesium oxide as the carrier of the colloidal spray liquid. Mix magnesium oxide and water in a 1:2 ratio to form a mixture. Add an additive containing β molecular sieve and aluminum nitrate to the mixture, wherein the mass fraction of the additive is 35% of the mixture. Ball mill the mixture containing magnesium oxide, water and additive for 20 hours, and control the particle size of the colloidal spray liquid to 5 μm. The colloidal spray liquid is then obtained.

[0074] Step 2: Select a nickel-based substrate and calcine it in an air or oxygen environment at 500°C. After calcination, immerse the substrate in a 5% sulfuric acid environment for 4 hours to obtain a specific surface area of ​​100 m². 2 / g of carrier; then the colloidal spraying liquid obtained in step one is sprayed on the carrier to form a colloidal spraying layer;

[0075] Step 3: Dry the carrier with the colloidal coating on its surface, and then bake it at 500℃.

[0076] Step 4: First, mix the ruthenium metal salt solution with alumina. After mixing, ball mill the mixture of ruthenium metal salt solution and alumina to obtain a mixed colloid containing ruthenium metal and alumina; wherein the mass fraction of ruthenium metal is controlled to be 3%. The carrier containing the colloidal coating after calcination in Step 3 is immersed in the colloid containing ruthenium salt for 1.5 hours. After immersion, the carrier containing the colloidal coating is taken out and dried; thus, an integral structural ammonia decomposition catalyst with coating is obtained.

[0077] Example 10

[0078] Step 1: Select magnesium oxide as the carrier of the colloidal spray liquid. Mix magnesium oxide and water at a ratio of 1:2.5 to form a mixture. Add an additive containing β molecular sieve and aluminum nitrate to the mixture, wherein the mass fraction of the additive is 40% of the mixture. Ball mill the mixture containing magnesium oxide, water and additive for 30 hours, and control the particle size of the colloidal spray liquid to be 20 μm. The colloidal spray liquid is then obtained.

[0079] Step 2: Select a nickel-based support and calcine it in an air or oxygen environment at 600°C. After calcination, immerse the support in a 20% sulfuric acid solution for 2 hours to obtain a specific surface area of ​​150 m². 2 / g of carrier; then the colloidal spraying liquid obtained in step one is sprayed on the carrier to form a colloidal spraying layer;

[0080] Step 3: Dry the carrier with the colloidal coating on its surface, and then bake it at 500℃.

[0081] Step 4: First, mix the ruthenium metal salt solution with alumina. After mixing, ball mill the mixture of ruthenium metal salt solution and alumina to obtain a mixed colloid containing ruthenium metal and alumina; wherein the mass fraction of ruthenium metal is controlled to be 4%. The carrier containing the colloidal coating after calcination in Step 3 is immersed in the colloid containing ruthenium salt for 2 hours. After immersion, the carrier containing the colloidal coating is taken out and dried; thus, an integral structural ammonia decomposition catalyst with coating is obtained.

[0082] Example 11

[0083] Step 1: Select magnesium oxide as the carrier of the colloidal spray liquid. Mix magnesium oxide and water at a ratio of 1:2.5 to form a mixture. Add an additive containing β molecular sieve and aluminum nitrate to the mixture, wherein the mass fraction of the additive is 50% of the mixture. Ball mill the mixture containing magnesium oxide, water and additive for 30 hours, and control the particle size of the colloidal spray liquid to be 20 μm. The colloidal spray liquid is then obtained.

[0084] Step 2: Select a nickel-based support and calcine it in an air or oxygen environment at 600°C. After calcination, immerse the support in a 20% sulfuric acid solution for 2 hours to obtain a specific surface area of ​​150 m². 2 / g of carrier; then the colloidal spraying liquid obtained in step one is sprayed on the carrier to form a colloidal spraying layer;

[0085] Step 3: Dry the carrier with the colloidal coating on its surface, and then bake it at 500℃.

[0086] Step 4: First, mix the ruthenium metal salt solution with alumina. After mixing, ball mill the mixture of ruthenium metal salt solution and alumina to obtain a mixed colloid containing ruthenium metal and alumina; wherein the mass fraction of ruthenium metal is controlled to be 4%. The carrier containing the colloidal coating after calcination in Step 3 is immersed in the colloid containing ruthenium salt for 2 hours. After immersion, the carrier containing the colloidal coating is taken out and dried; thus, an integral structural ammonia decomposition catalyst with coating is obtained.

[0087] Example 12

[0088] Step 1: Select magnesium oxide as the carrier of the colloidal spray liquid. Mix magnesium oxide and water at a ratio of 1:2.5 to form a mixture. Add an additive containing β molecular sieve and aluminum nitrate to the mixture, wherein the mass fraction of the additive is 40% of the mixture. Ball mill the mixture containing magnesium oxide, water and additive for 30 hours, and control the particle size of the colloidal spray liquid to be 20 μm. The colloidal spray liquid is then obtained.

[0089] Step 2: Select a nickel-based support and calcine it in an air or oxygen environment at 600°C. After calcination, immerse the support in a 40% nitric acid environment for 2 hours to obtain a specific surface area of ​​150 m². 2 / g of carrier; then the colloidal spraying liquid obtained in step one is sprayed on the carrier to form a colloidal spraying layer;

[0090] Step 3: Dry the carrier with the colloidal coating on its surface, and then bake it at 500℃.

[0091] Step 4: First, mix the ruthenium metal salt solution with alumina. After mixing, ball mill the mixture of ruthenium metal salt solution and alumina to obtain a mixed colloid containing ruthenium metal and alumina; wherein the mass fraction of ruthenium metal is controlled to be 4%. The carrier containing the colloidal coating after calcination in Step 3 is immersed in the colloid containing ruthenium salt for 2 hours. After immersion, the carrier containing the colloidal coating is taken out and dried; thus, an integral structural ammonia decomposition catalyst with coating is obtained.

[0092] Example 13

[0093] Step 1: Select magnesium oxide as the carrier of the colloidal spray liquid. Mix magnesium oxide and water at a ratio of 1:2.5 to form a mixture. Add an additive containing β molecular sieve and aluminum nitrate to the mixture, wherein the mass fraction of the additive is 40% of the mixture. Ball mill the mixture containing magnesium oxide, water and additive for 30 hours, and control the particle size of the colloidal spray liquid to be 20 μm. The colloidal spray liquid is then obtained.

[0094] Step 2: Select a nickel-based support and calcine it in an air or oxygen environment at 600°C. After calcination, immerse the support in a 20% sulfuric acid solution for 2 hours to obtain a specific surface area of ​​150 m². 2 / g of carrier; then the colloidal spraying liquid obtained in step one is sprayed on the carrier to form a colloidal spraying layer;

[0095] Step 3: Dry the carrier with the colloidal coating on its surface, and then bake it at 500℃.

[0096] Step 4: First, mix the ruthenium metal salt solution with alumina. After mixing, ball mill the mixture of ruthenium metal salt solution and alumina to obtain a mixed colloid containing ruthenium metal and alumina; wherein the mass fraction of ruthenium metal is controlled to be 5%. The carrier containing the colloidal coating after calcination in Step 3 is immersed in the colloid containing ruthenium salt for 3 hours. After immersion, the carrier containing the colloidal coating is taken out and dried; thus, an integral structural ammonia decomposition catalyst with coating is obtained.

[0097] Example 14

[0098] Step 1: Select magnesium oxide as the carrier of the colloidal spray liquid. Mix magnesium oxide and water at a ratio of 1:2.5 to form a mixture. Add an additive containing β molecular sieve and aluminum nitrate to the mixture, wherein the mass fraction of the additive is 50% of the mixture. Ball mill the mixture containing magnesium oxide, water and additive for 30 hours, and control the particle size of the colloidal spray liquid to be 20 μm. The colloidal spray liquid is then obtained.

[0099] Step 2: Select a nickel-based support and calcine it in an air or oxygen environment at 600°C. After calcination, immerse the support in a 20% sulfuric acid solution for 2 hours to obtain a specific surface area of ​​150 m². 2 / g of carrier; then the colloidal spraying liquid obtained in step one is sprayed on the carrier to form a colloidal spraying layer;

[0100] Step 3: Dry the carrier with the colloidal coating on its surface, and then bake it at 500℃.

[0101] Step 4: First, mix the ruthenium metal salt solution with alumina. After mixing, ball mill the mixture of ruthenium metal salt solution and alumina to obtain a mixed colloid containing ruthenium metal and alumina; wherein the mass fraction of ruthenium metal is controlled to be 5%. The carrier containing the colloidal coating after calcination in Step 3 is immersed in the colloid containing ruthenium salt for 3 hours. After immersion, the carrier containing the colloidal coating is taken out and dried; thus, an integral structural ammonia decomposition catalyst with coating is obtained.

[0102] Example 15

[0103] Step 1: Select magnesium oxide as the carrier of the colloidal spray liquid. Mix magnesium oxide and water at a ratio of 1:2.5 to form a mixture. Add an additive containing β molecular sieve and aluminum nitrate to the mixture, wherein the mass fraction of the additive is 40% of the mixture. Ball mill the mixture containing magnesium oxide, water and additive for 30 hours, and control the particle size of the colloidal spray liquid to be 20 μm. The colloidal spray liquid is then obtained.

[0104] Step 2: Select a nickel-based carrier and calcine it in an air or oxygen environment at 600°C. After calcination, immerse the carrier in a 5% hydrochloric acid environment for 5 hours to obtain a specific surface area of ​​150 m². 2 / g of carrier; then the colloidal spraying liquid obtained in step one is sprayed on the carrier to form a colloidal spraying layer;

[0105] Step 3: Dry the carrier with the colloidal coating on its surface, and then heat it in an environment of 500℃.

[0106] Step 4: First, mix the ruthenium metal salt solution with alumina. After mixing, ball mill the mixture of ruthenium metal salt solution and alumina to obtain a mixed colloid containing ruthenium metal and alumina; wherein the mass fraction of ruthenium metal is controlled to be 5%. The carrier containing the colloidal coating after calcination in Step 3 is immersed in the colloid containing ruthenium salt for 3 hours. After immersion, the carrier containing the colloidal coating is taken out and dried; thus, an integral structural ammonia decomposition catalyst with coating is obtained.

[0107] The monolithic ammonia decomposition catalysts with coatings obtained in the above different embodiments were tested for dispersibility, ammonia decomposition activity, and catalyst stability under 1000 hours at 500°C and space velocities of 4000, 6000, and 8000 mL / g·h. The test results are shown in Table 1 below.

[0108] Table 1. Results of catalyst dispersion, ammonia decomposition activity, and stability tests at 500℃ and space velocities of 4000, 6000, and 8000 mL / g·h for 1000 hours.

[0109] Ruthenium content (%) Space velocity (mL / g·h) Dispersion (%) Ammonia decomposition activity (%) 1000-hour stability (%) 0.5 4000 67 61 63 2 4000 55 81 82 3 4000 41 99.5 99.5 4 6000 37 99.5 99.5 5 8000 30 99.5 99.5

[0110] As shown in the table above, the higher the ruthenium content in the prepared catalyst, the lower the catalyst dispersion at the same space velocity, such as 4000 mL / g·h, the higher the ruthenium content. The ammonia decomposition activity and stability both increase with increasing ruthenium content. When the space velocity reaches 6000 mL / g·h and 8000 mL / g·h, the catalyst dispersion at 500℃ can reach a minimum of 30%, and the ammonia decomposition activity and 1000-hour stability both reach 99.5%. This indicates that preparing an ammonia decomposition catalyst with an integral structure by spraying a colloidal coating containing magnesium oxide or magnesium aluminum spinel onto a nickel-based substrate, and then spraying ruthenium sol onto this coating, still exhibits good ammonia decomposition activity and stability at high space velocities. Furthermore, the catalyst dispersion decreases with increasing ruthenium content, effectively improving the catalyst's thermal stability and ammonia decomposition activity, while also extending its service life.

[0111] 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 process for the preparation of a monolithic structured ammonia decomposition catalyst with a coating, characterized in that: The method comprises the following steps: Step one: magnesium oxide or magnesium-aluminum spinel carrier is mixed with water to form a mixture, and then an additive is added to the mixture and the mixture is ball milled to obtain a colloidal spray solution; the additive is beta molecular sieve and aluminum nitrate, and the mass fraction of the additive in the mixture is 10-50%; Step two: the obtained colloidal spray solution is sprayed on the surface of a carrier made of nickel, stainless steel or cordierite; Step three: the carrier containing the colloidal spray solution is dried, and then is calcined in an environment with a temperature higher than 400 DEG C; Step four: the carrier containing the colloidal spray layer after calcination is immersed in a colloidal solution containing a ruthenium salt, and the mass fraction of ruthenium metal in the colloidal solution containing the ruthenium salt is 0.5-5%, until the content of ruthenium on the surface of the carrier reaches 5-20 g / L; after immersion, the carrier containing the colloidal spray layer is taken out of the colloidal solution and dried; thus an integral structure type ammonia decomposition catalyst containing a coating is obtained.

2. A method for producing a monolithic ammonia decomposition catalyst having a coating according to claim 1, characterized by: In step one, the magnesium oxide or magnesium-aluminum spinel carrier is mixed with water in a ratio of 1:1-1:3 to form a mixture, and then an additive is added to the mixture, followed by ball milling.

3. The method of claim 1, wherein the preparation of a monolithic ammonia decomposition catalyst with a coating is characterized by: In step one, the ball milling time is 2-48 hours; and the particle size of the colloidal spray solution ranges from 1 to 50 microns.

4. The method of claim 1, wherein the preparation of a monolithic ammonia decomposition catalyst with a coating is characterized by: In step two, when nickel or stainless steel is selected as the carrier, the nickel and stainless steel materials are first calcined in an air or oxygen environment with a temperature of 400-700 DEG C; then the nickel carrier or stainless steel carrier containing nickel oxide on the surface is immersed in an acidic solution with a temperature ranging from 30 to 60 DEG C for at least 0.5 hours.

5. A method of making a coated monolithic ammonia decomposition catalyst according to claim 4, characterized in that: The nickel carrier or stainless steel carrier containing nickel oxide on the surface is immersed in hydrochloric acid with a concentration of 5-20%, or nitric acid with a concentration of 5-40%, or sulfuric acid with a concentration of 5-40% for at least 0.5 hours.

6. The method of claim 1, wherein the preparation of a monolithic ammonia decomposition catalyst with a coating is characterized by: In step three, the mass fraction of the colloidal spray solution used on the carrier containing the colloidal spray layer is 20-100 g / L.

7. The method of claim 1, wherein the preparation of a monolithic ammonia decomposition catalyst with a coating is characterized by: In step four, a ruthenium metal salt solution is first mixed with aluminum oxide, and then the mixed ruthenium metal salt solution and aluminum oxide mixture are ball milled to form a mixed colloidal solution containing the ruthenium metal salt solution and aluminum oxide; the mass fraction of ruthenium metal in the mixed colloidal solution is 2-5%.

8. A coated monolithic ammonia decomposition catalyst produced by the production method of a coated monolithic ammonia decomposition catalyst according to any one of claims 1 to 7, characterized by: The method comprises the following steps:

9. A monolithic washcoated ammonia decomposition catalyst according to claim 8, characterized in that: The method comprises the following steps: The thickness of the colloidal spray layer ranges from 0.5 to 1 millimeter.

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