A monolithic ruthenium-based ammoxidation catalyst and a method for preparing the same

Abstract

The application discloses a whole structure type ruthenium-based ammonia decomposition catalyst and a preparation method thereof. The preparation method comprises the following steps: step one, oxidizing a nickel-based carrier; step two, soaking the nickel-based carrier containing the oxidized nickel in an acidic solution with a mass concentration greater than 1 mol / L; step three, taking the nickel-based carrier out of the acidic solution and drying, and then soaking the nickel-based carrier in a mixed solution containing a ruthenium-based metal salt and an additive; and step four, taking the impregnated nickel-based carrier out of the mixed solution containing the ruthenium-based metal salt and the additive and drying, and then soaking the nickel-based catalyst in the mixed solution again until the content of the ruthenium and the additive on the nickel-based carrier reaches a target loading. The whole structure type ruthenium-based ammonia decomposition catalyst prepared by the method has both nickel and ruthenium active sites, and the ammonia decomposition reaction activity and stability are further improved.

Description

Technical Field

[0001] This invention relates to the field of ammonia decomposition technology, specifically to a ruthenium-based ammonia decomposition catalyst with an integral structure for ammonia decomposition to produce hydrogen and its preparation method. Background Technology

[0002] Ammonia decomposition catalysts are mainly used in environmental protection and the production of hydrogen and nitrogen. In environmental protection, ammonia-containing waste gas from factories is decomposed into non-toxic hydrogen and nitrogen using an ammonia decomposition catalyst, which can then be recycled to reduce pollution. The ammonia decomposition reaction primarily uses noble metal catalysts such as ruthenium and platinum, and non-noble metal catalysts such as iron and nickel. Currently available data shows that the Ru-based catalyst with the best ammonia decomposition activity uses graphitized carbon as its support. However, the carbon support may undergo methanation at temperatures above 500°C in a hydrogen atmosphere, exhibiting poor thermal stability. Existing commercially available Ni-based ammonia decomposition catalysts use alumina as their support, resulting in a high activity temperature range (above 700°C) and operating temperatures typically as high as 820°C, but poor activity at low temperatures. With long-term use, pulverization can lead to significant resistance, and the ammonia decomposition activity is low at high space velocities. Although monolithic nickel-based catalysts are being prepared using a framework, their activity still falls short of the activity and stability requirements for ammonia decomposition applications.

[0003] Chinese patent CN110270338B discloses a nickel and / or ruthenium-based ammonia decomposition catalyst, its preparation method, and its application. The catalyst comprises an active component of ruthenium and / or nickel, a support composed of graphite activated carbon, and an alkali metal oxide auxiliary. First, the support and auxiliary are mixed and calcined to obtain a catalyst support. Then, a metal salt solution is prepared. Finally, the active component of the metal salt solution is loaded onto the catalyst support using an impregnation or deposition method to obtain an ammonia decomposition catalyst containing nickel and / or ruthenium. However, the ammonia decomposition catalyst containing ruthenium and / or nickel prepared by this method exhibits low activity under high space velocity conditions, and the ammonia decomposition reaction activity and stability under low temperature conditions still fail to meet industrial application standards; its application scope is limited. Summary of the Invention

[0004] To address the shortcomings of existing nickel-based catalysts with alumina as the support, such as high operating temperatures, significant resistance due to pulverization during long-term use, and low ammonia decomposition activity at high space velocities, which fail to meet the activity and stability requirements of ammonia decomposition reactions in industrial applications, this paper proposes a monolithic ruthenium-based ammonia decomposition catalyst with a higher specific surface area and better low-temperature ammonia synthesis activity and stability at high space velocities, as well as its preparation method.

[0005] The technical solution adopted by this invention to solve its technical problem is: a method for preparing an integral ruthenium-based ammonia decomposition catalyst, comprising the following steps: Step 1: oxidizing a nickel-based support to generate nickel oxide on the surface of the nickel-based support; Step 2: immersing the nickel-based support containing nickel oxide in an acidic solution with a molar concentration greater than 1 mol / L; Step 3: removing the nickel-based support from the acidic solution, first cleaning the nickel-based support, then drying the cleaned nickel-based support, and finally immersing the nickel-based support in a mixed solution containing ruthenium-based metal salt and an additive; Step 4: removing the impregnated nickel-based support from the mixed solution containing ruthenium-based metal salt and an additive and drying it, and then immersing the nickel-based catalyst in the mixed solution again until the content of ruthenium and the additive on the nickel-based support reaches the target loading.

[0006] Furthermore, in step one, the nickel-based support is calcined in an air or oxygen environment at 400–700°C and a pressure of 0–20 MPa to generate nickel oxide on the surface of the nickel-based support.

[0007] Furthermore, after the nickel-based support is calcined, the nickel-based support containing nickel oxide on its surface is heat-treated at 400–700°C for 2–24 hours.

[0008] Furthermore, in step two, the acidic solution is hydrochloric acid, nitric acid, or sulfuric acid; when the acidic solution is hydrochloric acid, the concentration of the acidic solution is 5-20%; when the acidic solution is nitric acid, the concentration of the acidic solution is 5-40%; when the acidic solution is sulfuric acid, the concentration of the acidic solution is 5-40%; and the temperature of the acidic solution is 30-60°C.

[0009] Furthermore, in step two, the acidic solution is a sulfuric acid solution with a concentration of 1–3 mol / L, and the acidic solution is connected to a DC power supply of 12–36 volts.

[0010] Furthermore, in step three, the additives include any one or more of alkali metals, alkaline earth metals, and lanthanide rare earth metals; the mass fraction of the additives is 0.5% to 10% of the mixed solution.

[0011] Furthermore, in step three, the mass of the mixed solution composed of the ruthenium metal salt solution and the additive is equal to the mass of the nickel-based support containing nickel oxide on its surface.

[0012] Furthermore, in step three, the nickel-based support is immersed in a mixed solution consisting of a salt solution containing ruthenium metal and an additive for at least 30 minutes.

[0013] This application also discloses an integral structure ammonia decomposition catalyst, comprising a nickel-based support, wherein the surface layer of the nickel-based support contains nickel oxide, and ruthenium metal and an additive are further loaded on the surface of the nickel-based support, wherein the mass of the ruthenium metal is 0.5 to 5% of the mass of the nickel-based support, and the mass of the additive is 0.5 to 10% of the mass of the nickel-based support.

[0014] Furthermore, the mass of ruthenium metal is 0.5%, 2%, 3%, 4%, or 5% of the nickel-based support; the mass of the additives is 0.5%, 2%, 4%, 6%, 8%, and 10% of the nickel-based support.

[0015] The present invention discloses a method for preparing an integral ruthenium-based ammonia decomposition catalyst. This method utilizes nickel as a catalyst support, oxidizes the nickel-based structure, and then immerses the nickel-based support in an acidic solution and a mixed solution containing ruthenium. This results in a catalyst possessing both nickel-based and ruthenium-based active sites. Through the synergistic effect of the nickel-based and ruthenium-based sites, the catalyst maintains 99.5% ammonia decomposition activity even at a maximum space velocity of 5000 mL / g·h and a temperature of 500°C. This effectively improves the catalyst's reactivity and stability under high air velocity and low temperature conditions. 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 ruthenium-based 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 ruthenium-based ammonia decomposition catalyst of the present invention includes the following steps:

[0020] Step 1: Oxidize the nickel-based support to generate nickel oxide on the surface of the nickel-based support;

[0021] Step 2: Immerse the nickel-based support containing nickel oxide in an acidic solution with a molar concentration greater than 1 mol / L;

[0022] Step 3: Remove the nickel-based support from the acidic solution, clean it, dry it, and finally immerse it in a mixed solution containing ruthenium-based metal salt and additives.

[0023] Step 4: Remove the impregnated nickel-based support from the mixed solution containing ruthenium-based metal salt and additives and dry it. After drying, immerse the nickel-based catalyst in the mixed solution again until the ruthenium and additive content on the nickel-based support reaches the target loading.

[0024] In step one, the nickel-based support is first calcined in an air or oxygen environment at a temperature range of 400–700°C to obtain a nickel-based substrate with nickel oxide on its surface. When the nickel-based support is in an air or oxygen environment, the nickel-based substrate undergoes an oxidation reaction with oxygen to generate nickel oxide. Further, the air or oxygen pressure is 0–20 MPa. When the air or oxygen pressure is 0–10 MPa, the calcination temperature of the nickel-based support is 600–700°C; when the air or oxygen pressure is 10–15 MPa, the calcination temperature is 500–600°C; and when the air or oxygen pressure is 15–20 MPa, the calcination temperature is 400–500°C. The specific surface area of ​​the nickel-based support calcined in an air and oxygen environment at 400–700°C ranges from 60 to 200 m². 2 / g, thereby obtaining a nickel-based support with a high specific surface area and nickel oxide on the surface; wherein, in order to control the formation rate and proportion range of nickel oxide on the nickel surface, preferably, after the nickel-based support is calcined, the nickel-based support is heat-treated at 400-700℃ for 2-24 hours, and the ambient temperature of the nickel-based support is kept constant during the heat treatment process, thereby achieving the effect of controlling the oxidation rate and degree of oxidation of the nickel support.

[0025] In step two, the surface obtained in step one contains nickel oxide and has a specific surface area ranging from 60 to 200 μm². 2A nickel-based support of / g is immersed in an acidic solution with a molar concentration greater than 1mol / L, wherein the acidic solution is hydrochloric acid, nitric acid, or sulfuric acid; specifically, when hydrochloric acid is chosen as the acidic solution, the concentration of hydrochloric acid is 5-20%; when nitric acid is chosen as the acidic solution, the concentration of nitric acid is 5-40%; when sulfuric acid is chosen as the acidic solution, the concentration of sulfuric acid is 5-40%. More specifically, in order to further increase the specific surface area of ​​the nickel-based surface, the acidic solution is heated to 30-60℃, and the nickel-based support obtained in step one is immersed at 30-60℃ for 0.5-6 hours; after immersion, the nickel-based support is removed from the acidic solution and rinsed with water to remove hydrogen ions from the surface of the nickel-based support. The rinsed nickel-based support is dried at 120℃, finally obtaining a specific surface area of ​​80-200m². 2 / g contains nickel-based carriers with nickel oxide on their surface.

[0026] One method to increase the specific surface area of ​​nickel-based surfaces is electrochemical. When using electrochemical methods to increase the specific surface area of ​​nickel-based supports, the nickel-based support is first connected to a lead material, and then both the connected nickel-based support and lead material are simultaneously placed in a sulfuric acid solution with a molar concentration of 1–3 mol / L. The sulfuric acid solution is then connected to a DC power supply of 12–36 volts and energized for 10–30 hours. After energizing, the nickel-based support is removed from the sulfuric acid solution, washed with clean water, and dried in an environment above 120°C. This yields a nickel-based support with a specific surface area of ​​80–200 m² / g containing nickel oxide on its surface.

[0027] In step three, a mixed solution containing ruthenium metal salt and an additive is first prepared. Specifically, the additive includes any one or more of alkali metals, alkaline earth metals, and lanthanide rare earth metals. This provides electron-generating aids for the subsequent ammonia decomposition process, thereby improving the catalyst's reactivity in ammonia decomposition, reducing the temperature required for ammonia decomposition, saving energy consumption during the reaction, and improving the overall stability of the catalyst. The mass fraction of the additive is 0.5-10% of the total mixed solution. To ensure that the final ammonia decomposition catalyst possesses both ruthenium and nickel as active components, thus achieving better catalytic effects and performance, the nickel-based support with a high specific surface area obtained in step two is impregnated... The nickel-based support, which has a high specific surface area and contains nickel oxide, is immersed in a mixed solution consisting of a ruthenium metal salt solution and an additive. The mass of the nickel-based support used for immersion is equal to the mass of the mixed solution containing the ruthenium metal salt solution and the additive. Furthermore, in order to ensure that the ruthenium element in the ruthenium-based metal can be completely covered on the nickel-based support, the nickel-based support is immersed in the mixed solution containing the ruthenium metal salt solution and the additive for at least 30 minutes, for example, 30 to 1440 minutes. This allows the ruthenium element to be completely covered and impregnated onto the nickel-based support. The immersion time is related to the activity of the catalyst after subsequent testing, and the immersion time of the nickel-based support is adjusted according to the subsequent activity requirements of the catalyst.

[0028] In step four, the nickel-based support containing ruthenium on its surface after impregnation is removed from the mixed solution containing ruthenium-based metal salt and additives and dried. To further increase the ruthenium content on the surface of the nickel-based support, so that the catalyst can simultaneously possess the dual active components of ruthenium and nickel, preferably, the impregnated nickel-based support is immersed again in the solution containing ruthenium-based metal salt and additives. The impregnation time is controlled according to the activity requirements of the subsequent catalyst. After impregnation, it is removed and dried again. This operation is repeated until the ruthenium content and the additive content in the nickel-based support both reach the loading amount that meets the activity requirements of the subsequent catalyst.

[0029] This application also discloses an integral structured ammonia decomposition catalyst manufactured by the preparation method of the integral structured ruthenium-based ammonia decomposition catalyst, comprising a nickel-based support, wherein the surface layer of the nickel-based support contains nickel oxide, and ruthenium metal and an additive are loaded on the surface of the nickel-based support, wherein the mass of the ruthenium metal is 0.5-5% of the nickel-based support, and the mass of the additive is 0.5-10% of the nickel-based support.

[0030] Furthermore, the surface of the nickel-based support is treated by an electrochemical oxidation method, and the mass of ruthenium metal is 0.5%, 2%, 3%, 4% or 5% of the nickel-based support, and the mass of the additives is 0.5%, 2%, 4%, 6%, 8% and 10% of the nickel-based support.

[0031] Example 1

[0032] Step 1: Oxidize the nickel-based support in an air or oxygen environment at 400–500℃ and 15–20 MPa to form nickel oxide on the surface of the nickel-based support and increase the specific surface area of ​​the nickel-based support to 60 m². 2 / g; and the prepared nickel-based support was left to stand at 400-500℃ for 2 hours;

[0033] Step 2: Immerse the nickel-based support containing nickel oxide in a 5-20% hydrochloric acid solution, while heating the hydrochloric acid solution to 30°C, and then immerse the nickel-based support containing nickel oxide in the heated hydrochloric acid solution for 0.5 hours.

[0034] Step 3: Remove the nickel-based support from the 30°C hydrochloric acid solution, wash it, and then immerse the nickel-based support in a mixed solution containing ruthenium-based metal salt and additives for 30 minutes; wherein the mass fraction of the additives in the mixed solution is 0.5%;

[0035] Step 4: Remove the impregnated nickel-based support from the mixed solution containing ruthenium-based metal salt and additives and dry it. After drying, immerse the nickel-based catalyst in the mixed solution again until the mass of ruthenium on the nickel-based support reaches 0.5% of the weight of the nickel-based support and the mass of the additives reaches 0.5% of the weight of the nickel-based support.

[0036] Example 2

[0037] Step 1: Oxidize the nickel-based support in an air or oxygen environment at 400–500℃ and 15–20 MPa to form nickel oxide on the surface of the nickel-based support and increase the specific surface area of ​​the nickel-based support to 60 m². 2 / g; and the prepared nickel-based support was left to stand at 400-500℃ for 2 hours;

[0038] Step 2: Immerse the nickel-based support containing nickel oxide in a nitric acid solution with a concentration of 5-40%, while heating the nitric acid solution to 40°C, and then immerse the nickel-based support containing nickel oxide in the heated hydrochloric acid solution for 1 hour.

[0039] Step 3: Remove the nickel-based support from the nitric acid solution at 40°C, wash it, and then immerse the nickel-based support in a mixed solution containing ruthenium-based metal salt and additives for 30 minutes, wherein the mass fraction of the additives in the mixed solution is 0.5%.

[0040] Step 4: Remove the impregnated nickel-based support from the mixed solution containing ruthenium-based metal salt and additives and dry it. After drying, immerse the nickel-based catalyst in the mixed solution again until the mass of ruthenium on the nickel-based support reaches 0.5% of the weight of the nickel-based support and the mass of the additives reaches 0.5% of the weight of the nickel-based support.

[0041] Example 3

[0042] Step 1: Oxidize the nickel-based support in an air or oxygen environment at 400–500℃ and 15–20 MPa to form nickel oxide on the surface of the nickel-based support and increase the specific surface area of ​​the nickel-based support to 60 m². 2 / g; and the prepared nickel-based support was left to stand at 400-500℃ for 2 hours;

[0043] Step 2: Immerse the nickel-based support containing nickel oxide in a 5-20% hydrochloric acid solution, while heating the hydrochloric acid solution to 30°C, and then immerse the nickel-based support containing nickel oxide in the heated hydrochloric acid solution for 0.5 hours.

[0044] Step 3: Remove the nickel-based support from the 30°C hydrochloric acid solution, wash it, and then immerse the nickel-based support in a mixed solution containing ruthenium-based metal salt and additives for 30 minutes; wherein the mass fraction of the additives in the mixed solution is 10%.

[0045] Step 4: Remove the impregnated nickel-based support from the mixed solution containing ruthenium-based metal salt and additives and dry it. After drying, immerse the nickel-based catalyst in the mixed solution again until the mass of ruthenium on the nickel-based support reaches 0.5% of the weight of the nickel-based support and the mass of the additives reaches 0.5% of the weight of the nickel-based support.

[0046] Example 4

[0047] Step 1: Oxidize the nickel-based support in an air or oxygen environment at 500–600℃ and 10–15 MPa to form nickel oxide on the surface of the nickel-based support and increase the specific surface area of ​​the nickel-based support to 100 m². 2 / g; and the prepared nickel-based support was left to stand at 500-600℃ for 10 hours;

[0048] Step 2: Immerse the nickel-based support containing nickel oxide in a 5-40% nitric acid solution, while heating the nitric acid solution to 45°C, and then immerse the nickel-based support containing nickel oxide in the heated nitric acid solution for 3 hours.

[0049] Step 3: Remove the nickel-based support from the nitric acid solution at 45°C, wash it, and then immerse it in a mixed solution containing ruthenium-based metal salt and additives for 800 minutes; wherein the mass fraction of the additives in the mixed solution is 0.5%.

[0050] Step 4: Remove the impregnated nickel-based support from the mixed solution containing ruthenium-based metal salt and additives and dry it. After drying, immerse the nickel-based catalyst in the mixed solution again until the mass of ruthenium on the nickel-based support reaches 2% of the weight of the nickel-based support and the mass of the additives reaches 4% of the weight of the nickel-based support.

[0051] Example 5

[0052] Step 1: Oxidize the nickel-based support in an air or oxygen environment at 500–600℃ and 10–15 MPa to form nickel oxide on the surface of the nickel-based support and increase the specific surface area of ​​the nickel-based support to 100 m². 2 / g; and the prepared nickel-based support was left to stand at 500-600℃ for 10 hours;

[0053] Step 2: Immerse the nickel-based support containing nickel oxide in a 5-20% hydrochloric acid solution, while heating the hydrochloric acid solution to 50°C, and then immerse the nickel-based support containing nickel oxide in the heated hydrochloric acid solution for 4 hours.

[0054] Step 3: Remove the nickel-based support from the 50°C hydrochloric acid solution, wash it, and then immerse the nickel-based support in a mixed solution containing ruthenium-based metal salt and additives for 800 minutes; wherein the mass fraction of the additives in the mixed solution is 0.5%;

[0055] Step 4: Remove the impregnated nickel-based support from the mixed solution containing ruthenium-based metal salt and additives and dry it. After drying, immerse the nickel-based catalyst in the mixed solution again until the mass of ruthenium on the nickel-based support reaches 2% of the weight of the nickel-based support and the mass of the additives reaches 4% of the weight of the nickel-based support.

[0056] Example 6

[0057] Step 1: Oxidize the nickel-based support in an air or oxygen environment at 500–600℃ and 10–15 MPa to form nickel oxide on the surface of the nickel-based support and increase the specific surface area of ​​the nickel-based support to 100 m². 2 / g; and the prepared nickel-based support was left to stand at 500-600℃ for 10 hours;

[0058] Step 2: Immerse the nickel-based support containing nickel oxide in a nitric acid solution with a concentration of 5-40%, while heating the hydrochloric acid solution to 45°C, and then immerse the nickel-based support containing nickel oxide in the heated hydrochloric acid solution for 3 hours.

[0059] Step 3: Remove the nickel-based support from the 45°C hydrochloric acid solution, wash it, and then immerse the nickel-based support in a mixed solution containing ruthenium-based metal salt and additives for 800 minutes; wherein the mass fraction of the additives in the mixed solution is 10%.

[0060] Step 4: Remove the impregnated nickel-based support from the mixed solution containing ruthenium-based metal salt and additives and dry it. After drying, immerse the nickel-based catalyst in the mixed solution again until the mass of ruthenium on the nickel-based support reaches 2% of the weight of the nickel-based support and the mass of the additives reaches 4% of the weight of the nickel-based support.

[0061] Example 7

[0062] Step 1: Oxidize the nickel-based support in an air or oxygen environment at 600–700℃ and 0–10 MPa to form nickel oxide on the surface of the nickel-based support and increase the specific surface area of ​​the nickel-based support to 120 m². 2 / g; and the prepared nickel-based support was left to stand at 600-700℃ for 12 hours;

[0063] Step 2: Immerse the nickel-based support containing nickel oxide in a sulfuric acid solution with a concentration of 5-40%, while heating the sulfuric acid solution to 50°C, and then immerse the nickel-based support containing nickel oxide in the heated sulfuric acid solution for 4 hours.

[0064] Step 3: Remove the nickel-based support from the sulfuric acid solution at 50°C, wash it, and then immerse the nickel-based support in a mixed solution containing ruthenium-based metal salt and additives for 1000 minutes; wherein the mass fraction of the additives in the mixed solution is 0.5%;

[0065] Step 4: Remove the impregnated nickel-based support from the mixed solution containing ruthenium-based metal salt and additives and dry it. After drying, immerse the nickel-based catalyst in the mixed solution again until the mass of ruthenium on the nickel-based support reaches 3% of the weight of the nickel-based support and the mass of the additives reaches 6% of the weight of the nickel-based support.

[0066] Example 8

[0067] Step 1: Oxidize the nickel-based support in an air or oxygen environment at 600–700℃ and 0–10 MPa to form nickel oxide on the surface of the nickel-based support and increase the specific surface area of ​​the nickel-based support to 120 m². 2 / g; and the prepared nickel-based support was left to stand at 600-700℃ for 12 hours;

[0068] Step 2: Immerse the nickel-based support containing nickel oxide in a 5-20% hydrochloric acid solution, while heating the hydrochloric acid solution to 40°C, and then immerse the nickel-based support containing nickel oxide in the heated hydrochloric acid solution for 4 hours.

[0069] Step 3: Remove the nickel-based support from the 40°C hydrochloric acid solution, wash it, and then immerse the nickel-based support in a mixed solution containing ruthenium-based metal salt and additives for 1000 minutes; wherein the mass fraction of the additives in the mixed solution is 0.5%;

[0070] Step 4: Remove the impregnated nickel-based support from the mixed solution containing ruthenium-based metal salt and additives and dry it. After drying, immerse the nickel-based catalyst in the mixed solution again until the mass of ruthenium on the nickel-based support reaches 3% of the weight of the nickel-based support and the mass of the additives reaches 6% of the weight of the nickel-based support.

[0071] Example 9

[0072] Step 1: Oxidize the nickel-based support in an air or oxygen environment at 600–700℃ and 0–10 MPa to form nickel oxide on the surface of the nickel-based support and increase the specific surface area of ​​the nickel-based support to 120 m². 2 / g; and the prepared nickel-based support was left to stand at 600-700℃ for 12 hours;

[0073] Step 2: Immerse the nickel-based support containing nickel oxide in a sulfuric acid solution with a concentration of 5-40%, while heating the sulfuric acid solution to 50°C, and then immerse the nickel-based support containing nickel oxide in the heated sulfuric acid solution for 4 hours.

[0074] Step 3: Remove the nickel-based support from the sulfuric acid solution at 50°C, wash it, and then immerse the nickel-based support in a mixed solution containing ruthenium-based metal salt and additives for 1000 minutes; wherein the mass fraction of the additives in the mixed solution is 10%.

[0075] Step 4: Remove the impregnated nickel-based support from the mixed solution containing ruthenium-based metal salt and additives and dry it. After drying, immerse the nickel-based catalyst in the mixed solution again until the mass of ruthenium on the nickel-based support reaches 3% of the weight of the nickel-based support and the mass of the additives reaches 6% of the weight of the nickel-based support.

[0076] Example 10

[0077] Step 1: Oxidize the nickel-based support in an air or oxygen environment at 600–700℃ and 0–10 MPa to form nickel oxide on the surface of the nickel-based support and increase the specific surface area of ​​the nickel-based support to 100 m². 2 / g; and the prepared nickel-based support was left to stand at 600-700℃ for 16 hours;

[0078] Step 2: Immerse the nickel-based support containing nickel oxide in a 5-20% nitric acid solution, while heating the nitric acid solution to 50°C, and then immerse the nickel-based support containing nickel oxide in the heated nitric acid solution for 4 hours.

[0079] Step 3: Remove the nickel-based support from the 50°C nitric acid solution, wash it, and then immerse it in a mixed solution containing ruthenium-based metal salt and additives for 1200 minutes; wherein the mass fraction of the additives in the mixed solution is 0.5%.

[0080] Step 4: Remove the impregnated nickel-based support from the mixed solution containing ruthenium-based metal salt and additives and dry it. After drying, immerse the nickel-based catalyst in the mixed solution again until the mass of ruthenium on the nickel-based support reaches 4% of the weight of the nickel-based support and the mass of the additives reaches 8% of the weight of the nickel-based support.

[0081] Example 11

[0082] Step 1: Oxidize the nickel-based support in an air or oxygen environment at 600–700℃ and 0–10 MPa to form nickel oxide on the surface of the nickel-based support and increase the specific surface area of ​​the nickel-based support to 100 m². 2 / g; and the prepared nickel-based support was left to stand at 600-700℃ for 16 hours;

[0083] Step 2: Immerse the nickel-based support containing nickel oxide in a sulfuric acid solution with a concentration of 5-40%, while heating the hydrochloric acid solution to 50°C, and then immerse the nickel-based support containing nickel oxide in the heated hydrochloric acid solution for 5 hours.

[0084] Step 3: Remove the nickel-based support from the 50°C hydrochloric acid solution, wash it, and then immerse the nickel-based support in a mixed solution containing ruthenium-based metal salt and additives for 1200 minutes; wherein the mass fraction of the additives in the mixed solution is 0.5%;

[0085] Step 4: Remove the impregnated nickel-based support from the mixed solution containing ruthenium-based metal salt and additives and dry it. After drying, immerse the nickel-based catalyst in the mixed solution again until the mass of ruthenium on the nickel-based support reaches 4% of the weight of the nickel-based support and the mass of the additives reaches 8% of the weight of the nickel-based support.

[0086] Example 12

[0087] Step 1: Oxidize the nickel-based support in an air or oxygen environment at 600–700℃ and 0–10 MPa to form nickel oxide on the surface of the nickel-based support and increase the specific surface area of ​​the nickel-based support to 100 m². 2 / g; and the prepared nickel-based support was left to stand at 600-700℃ for 16 hours;

[0088] Step 2: Immerse the nickel-based support containing nickel oxide in a sulfuric acid solution with a concentration of 5-40%, while heating the hydrochloric acid solution to 50°C, and then immerse the nickel-based support containing nickel oxide in the heated hydrochloric acid solution for 5 hours.

[0089] Step 3: Remove the nickel-based support from the 50°C hydrochloric acid solution, wash it, and then immerse the nickel-based support in a mixed solution containing ruthenium-based metal salt and additives for 1200 minutes; wherein the mass fraction of the additives in the mixed solution is 10%.

[0090] Step 4: Remove the impregnated nickel-based support from the mixed solution containing ruthenium-based metal salt and additives and dry it. After drying, immerse the nickel-based catalyst in the mixed solution again until the mass of ruthenium on the nickel-based support reaches 4% of the weight of the nickel-based support and the mass of the additives reaches 8% of the weight of the nickel-based support.

[0091] Example 13

[0092] Step 1: Oxidize the nickel-based support in an air or oxygen environment at 600–700℃ and 0–10 MPa to form nickel oxide on the surface of the nickel-based support and increase the specific surface area of ​​the nickel-based support to 200 m². 2 / g; and the prepared nickel-based support was left to stand at 600-700℃ for 24 hours;

[0093] Step 2: Connect the nickel-based carrier containing nickel oxide to the lead material, and then simultaneously place the connected nickel-based carrier and lead material into a sulfuric acid solution with a molar concentration of 2 mol / L. Connect the sulfuric acid solution to a 24-volt DC power supply and apply electricity for 10 hours.

[0094] Step 3: Remove the nickel-based support from the sulfuric acid solution and rinse with water, then dry it in an environment above 120°C; after drying, immerse the nickel-based support in a mixed solution containing ruthenium-based metal salt and additives for 1440 minutes; wherein the mass fraction of the additives in the mixed solution is 0.5%.

[0095] Step 4: Remove the impregnated nickel-based support from the mixed solution containing ruthenium-based metal salt and additives and dry it. After drying, immerse the nickel-based catalyst in the mixed solution again until the mass of ruthenium on the nickel-based support reaches 5% of the weight of the nickel-based support and the mass of the additives reaches 10% of the weight of the nickel-based support.

[0096] Example 14

[0097] Step 1: Oxidize the nickel-based support in an air or oxygen environment at 600–700℃ and 0–10 MPa to form nickel oxide on the surface of the nickel-based support and increase the specific surface area of ​​the nickel-based support to 200 m². 2 / g; and the prepared nickel-based support was left to stand at 600-700℃ for 24 hours;

[0098] Step 2: Connect the nickel-based carrier containing nickel oxide to the lead material, and then simultaneously place the connected nickel-based carrier and lead material into a sulfuric acid solution with a molar concentration of 1 mol / L. Connect the sulfuric acid solution to a 24-volt DC power supply and apply the power for 20 hours.

[0099] Step 3: Remove the nickel-based support from the sulfuric acid solution and rinse with water, then dry it in an environment above 120°C; after drying, immerse the nickel-based support in a mixed solution containing ruthenium-based metal salt and additives for 1440 minutes; wherein the additive content in the mixed solution is 0.5%.

[0100] Step 4: Remove the impregnated nickel-based support from the mixed solution containing ruthenium-based metal salt and additives and dry it. After drying, immerse the nickel-based catalyst in the mixed solution again until the mass of ruthenium on the nickel-based support reaches 5% of the weight of the nickel-based support and the mass of the additives reaches 10% of the weight of the nickel-based support.

[0101] Example 15

[0102] Step 1: Oxidize the nickel-based support in an air or oxygen environment at 600–700℃ and 0–10 MPa to form nickel oxide on the surface of the nickel-based support and increase the specific surface area of ​​the nickel-based support to 200 m². 2 / g; and the prepared nickel-based support was left to stand at 600-700℃ for 24 hours;

[0103] Step 2: Connect the nickel-based carrier containing nickel oxide to the lead material, and then simultaneously place the connected nickel-based carrier and lead material into a sulfuric acid solution with a molar concentration of 3 mol / L. Connect the sulfuric acid solution to a 24-volt DC power supply and apply the power for 30 hours.

[0104] Step 3: Remove the nickel-based support from the sulfuric acid solution and wash it with water, then dry it in an environment above 120°C; after drying, immerse the nickel-based support in a mixed solution containing ruthenium-based metal salt and additives for 1440 minutes; wherein the content of additives in the mixed solution is 10%;

[0105] Step 4: Remove the impregnated nickel-based support from the mixed solution containing ruthenium-based metal salt and additives and dry it. After drying, immerse the nickel-based catalyst in the mixed solution again until the mass of ruthenium on the nickel-based support reaches 5% of the weight of the nickel-based support and the mass of the additives reaches 10% of the weight of the nickel-based support. The monolithic ruthenium-based ammonia decomposition catalysts prepared in Examples 1-15 were subjected to ammonia decomposition at 500°C and a space velocity of 3000-5000 mL / g·h to verify the activity of the prepared monolithic ruthenium-based ammonia decomposition catalysts. Specific data are as follows, based on the ruthenium metal content in different examples:

[0106] Table 1. Ammonia decomposition activity of monolithic ruthenium-based ammonia decomposition catalysts with different ruthenium contents in an environment of 500℃ and space velocity of 3000–5000 mL / g·h.

[0107]

[0108]

[0109] As shown in Table 1, when the ruthenium-based catalyst prepared by the method described above has a ruthenium content of 3% or even 5%, its activity during ammonia decomposition can reach 99.5% at a maximum space velocity of 5000 mL / g·h. Therefore, the ammonia decomposition catalyst prepared by the method described above can maintain an ammonia decomposition activity of 99.5% at a low temperature of 500℃ and a space velocity of 5000 mL / g·h. Through the synergistic effect of nickel-based and ruthenium-based groups in the catalyst, the ammonia decomposition activity of the catalyst under high space velocity and low temperature conditions is effectively improved, further enhancing the ammonia decomposition reaction activity and stability of the catalyst.

[0110] 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 monolithic ruthenium-based ammonia decomposition catalyst, characterized in that: Includes the following steps: Step 1: Oxidize the nickel-based support to generate nickel oxide on the surface of the nickel-based support; Step 2: Immerse the nickel-based support containing nickel oxide in an acidic solution with a molar concentration greater than 1 mol / L; A specific surface area of ​​80–200 m² was obtained. 2 / g contains nickel-based carriers with nickel oxide on the surface; Step 3: Remove the nickel-based support from the acidic solution, clean the nickel-based support, dry the cleaned support, and finally immerse the nickel-based support in a mixed solution containing ruthenium-based metal salt and additives; the additives include any one or more of alkaline earth metals and lanthanide rare earth metals; the mass fraction of the additives is 0.5% to 10% of the mixed solution; Step 4: Remove the impregnated nickel-based support from the mixed solution containing ruthenium-based metal salt and additives and dry it. After drying, immerse the nickel-based support in the mixed solution again until the ruthenium and additive content on the nickel-based support reaches the target loading. The integral ruthenium-based ammonia decomposition catalyst includes a nickel-based support, the surface layer of which contains nickel oxide, and ruthenium metal and an additive are loaded on the surface of the nickel-based support. The mass of the ruthenium metal is 0.5-5% of the mass of the nickel-based support, and the mass of the additive is 0.5-10% of the mass of the nickel-based support.

2. The method for preparing a monolithic ruthenium-based ammonia decomposition catalyst according to claim 1, characterized in that: In step one, the nickel-based support is calcined in an air or oxygen environment at 400–700°C and a pressure of 0–20 MPa to generate nickel oxide on the surface of the nickel-based support.

3. The method for preparing a monolithic ruthenium-based ammonia decomposition catalyst according to claim 2, characterized in that: After the nickel-based support is calcined, the nickel-based support containing nickel oxide on its surface is heat-treated at 400–700°C for 2–24 hours.

4. The method for preparing a monolithic ruthenium-based ammonia decomposition catalyst according to claim 1, characterized in that: In step two, the acidic solution is hydrochloric acid, nitric acid, or sulfuric acid; when the acidic solution is hydrochloric acid, the concentration of the acidic solution is 5-20%; when the acidic solution is nitric acid, the concentration of the acidic solution is 5-40%; when the acidic solution is sulfuric acid, the concentration of the acidic solution is 5-40%; and the temperature of the acidic solution is 30-60°C.

5. The method for preparing a monolithic ruthenium-based ammonia decomposition catalyst according to claim 1, characterized in that: In step two, the acidic solution is a sulfuric acid solution with a molar concentration of 1 to 3 mol / L, and the acidic solution is connected to a DC power supply of 12 to 36 volts.

6. The method for preparing a monolithic ruthenium-based ammonia decomposition catalyst according to claim 1, characterized in that: In step three, the nickel-based support is immersed in a mixed solution containing ruthenium-based metal salts and additives for at least 30 minutes.

7. The method for preparing a monolithic ruthenium-based ammonia decomposition catalyst according to claim 1, characterized in that: The mass of ruthenium metal is 0.5%, 2%, 3%, 4% or 5% of the nickel-based carrier; the mass of the additives is 0.5%, 2%, 4%, 6%, 8% and 10% of the nickel-based carrier.

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