A perovskite oxide catalyst for ammonia decomposition in situ leaching and a preparation method thereof

Abstract

The application belongs to the technical field of catalysts, and discloses a perovskite oxide in-situ dissolved ammonia cracking catalyst and a preparation method thereof.The ammonia cracking catalyst comprises a non-noble metal active component, a perovskite oxide carrier and an alkaline earth metal additive, the non-noble metal active component is in the form of nanoparticles and is distributed on the surface of the perovskite oxide carrier, the non-noble metal active component is a non-noble metal element and / or a non-noble metal alloy in-situ dissolved from the perovskite oxide, the perovskite oxide carrier is the perovskite oxide after in-situ dissolution of the non-noble metal active component, and the alkaline earth metal additive is loaded on the perovskite oxide carrier.The ammonia cracking catalyst has excellent catalytic activity and stability, and can be comparable to the performance of a traditional noble metal ruthenium-based catalyst, and is conducive to reducing the cost in the field of medium-temperature ammonia decomposition.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of catalysts, and particularly relates to a perovskite oxide in-situ dissolved ammonia cracking catalyst and a preparation method. BACKGROUND

[0002] Under the background of hydrogen energy development, using ammonia as a hydrogen carrier is one of the ways to solve the current hydrogen storage and transportation problems. In the application end, ammonia cracking for hydrogen production is an extremely important link in the field of ammonia energy. Among them, developing low-cost, high-activity and high-stability ammonia cracking catalyst is one of the current research priorities. Although ruthenium-based catalysts have good catalytic activity below 450 DEG C, the storage of noble metal ruthenium is limited, and the cost problem will be faced in industrial application, so developing non-noble metal catalysts with low temperature and high efficiency is the top priority.

[0003] Most of the current ammonia cracking catalysts are supported catalysts, mainly composed of active components, carrier materials and other parts, usually prepared by precipitation deposition method and impregnation method, so that the external active components are loaded on the carrier material. For example, alumina is used as a carrier material, impregnated into a Co ion solution, and after drying and sintering, the active component Co will be deposited on the carrier material. The catalyst prepared by the traditional method has the following problems: (1) the particle size of the active component metal particles is large, the reaction active area is low, and the catalyst activity is low; (2) the combination strength of the metal particles and the carrier is low, which leads to the easy falling off of the metal particles under variable working conditions; (3) the metal particles are easy to agglomerate during long-term work, which leads to performance degradation of the catalyst during long-term work.

[0004] Therefore, how to reduce the cost of ammonia cracking catalyst, improve the catalytic activity and long-term stability is a technical problem to be solved in the field. SUMMARY

[0005] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application provides a perovskite oxide in-situ dissolved ammonia cracking catalyst and a preparation method, which does not contain noble metal active components, has low cost, and has excellent catalytic activity and long-term stability.

[0006] In a first aspect, the present application provides an ammonia cracking catalyst, which comprises a non-noble metal active component, a perovskite oxide carrier and an alkaline earth metal additive, the non-noble metal active component is in the form of nanoparticles distributed on the surface of the perovskite oxide carrier, the non-noble metal active component is a non-noble metal element and / or a non-noble metal alloy in-situ dissolved from the perovskite oxide, the perovskite oxide carrier is the perovskite oxide after in-situ dissolution of the non-noble metal active component, and the alkaline earth metal additive is loaded on the perovskite oxide carrier.

[0007] In some embodiments of the present application, the chemical formula of the ammonia cracking catalyst is (A 1-x A’ x ) z B 1-y B’ y O 3-δ wherein A, A’ elements are independently selected from one or more of La, Pr, Sr, Ca, Mg, Ba; B, B’ elements are independently selected from one or more of Fe, Co, Ni, Mo, Cr, Cu, Mn, Nb; 0.2≤x≤0.8, 0.2≤y≤0.8, 0.5≤z≤1; δ represents oxygen defects.

[0008] In some embodiments of the present application, A, A’ elements are independently selected from one or more of La, Pr, Sr, Ba.

[0009] In some embodiments of the present application, A element is selected from La or Pr, and A’ element is selected from Sr or Ba.

[0010] In some embodiments of the present application, B, B’ elements are independently selected from one or more of Fe, Co, Ni.

[0011] In some embodiments of the present application, B element is selected from Fe or Co, and B’ element is selected from Ni or Fe.

[0012] In some embodiments of the present application, the non-noble metal active component is one or more of Fe, Co, Ni elements dissolved in-situ from perovskite oxides, and / or an alloy containing at least two of Fe, Co, Ni elements.

[0013] In some embodiments of the present application, the alkaline earth metal additive includes one or more of oxides, hydroxides, carbonates of alkaline earth metals.

[0014] In some embodiments of the present application, the alkaline earth metal additive is a carbonate of alkaline earth metal.

[0015] In some embodiments of the present application, the alkaline earth metal additive is strontium carbonate.

[0016] In the second aspect of the present application, a preparation method of the ammonia cracking catalyst of the first aspect of the present application is provided, wherein the ammonia cracking catalyst is prepared by a sol-gel method or a glycine-nitrate method.

[0017] In some embodiments of the present application, when the sol-gel method is used to prepare the ammonia cracking catalyst, the method includes the following steps:

[0018] (1) preparing a metal salt solution according to a stoichiometric ratio of the ammonia cracking catalyst, and mixing the metal salt solution with a complexing agent to obtain a metal salt complex solution;

[0019] (2) adjusting the pH of the metal salt complex solution to be alkaline to obtain a precursor solution;

[0020] (3) heating, stirring and drying the precursor solution to obtain a dry gel;

[0021] (4) sintering the dry gel to obtain a perovskite oxide;

[0022] (5) placing the perovskite oxide in a reducing atmosphere for reduction treatment, so that the non-noble metal active component in the perovskite oxide is in-situ dissolved out to obtain an ammonia cracking catalyst.

[0023] In some embodiments of the present application, the ratio of the molar amount of the complexing agent to the total molar amount of metal ions in the metal salt solution is (1-3):1.

[0024] In some embodiments of the present application, the complexing agent comprises citric acid and / or ethylenediaminetetraacetic acid.

[0025] In some embodiments of the present application, the pH value of the alkaline is 9-10.

[0026] In some embodiments of the present application, the specific process of step (3) of the sol-gel method is: heating and stirring the precursor solution at a constant temperature to obtain a wet gel; and then vacuum drying the wet gel to obtain a dry gel.

[0027] In some embodiments of the present application, the temperature of the constant temperature heating is 80-100℃, and the stirring time is 2-5h.

[0028] In some embodiments of the present application, the temperature of the vacuum drying is 160-200℃, and the pressure of the vacuum drying is -0.7bar to -0.9bar.

[0029] In some embodiments of the present application, the glycine-nitrate method is used to prepare the ammonia cracking catalyst, which comprises the following steps:

[0030] (1) preparing a metal salt solution according to a stoichiometric ratio of the ammonia cracking catalyst, and mixing the metal salt solution with glycine to obtain a precursor solution;

[0031] (2) heating and stirring the precursor solution to obtain a gel;

[0032] (3) heating the gel, and obtaining a powder after the gel is self-ignited by heating;

[0033] (4) sintering the powder to obtain a perovskite oxide;

[0034] (5) placing the perovskite oxide into a reducing atmosphere to perform a reduction treatment, so that the non-noble metal active component in the perovskite oxide is in-situ dissolved out, to obtain an ammonia cracking catalyst.

[0035] In some embodiments of the present application, the ratio of the molar amount of the glycine to the total molar amount of the metal ions in the metal salt solution is (1-2.31):1.

[0036] The specific process of step (2) of the glycine-nitrate method is that the precursor solution is heated at a constant temperature of 80-100℃ and stirred for 2-5h to obtain a gel.

[0037] In some embodiments of the present application, the gel is heated to 150-300℃.

[0038] In some embodiments of the present application, the sintering temperature is 800-1000℃, and the sintering time is 2-5h.

[0039] In some embodiments of the present application, the sintering temperature is 800-900℃, and the sintering time is 4-5h.

[0040] In some embodiments of the present application, the reduction temperature is 600-800℃, and the reduction time is 2-8h.

[0041] In some embodiments of the present application, the reduction temperature is 650-750℃, and the reduction time is 2-4h, preferably 4h.

[0042] In a third aspect of the present application, the ammonia cracking catalyst of the first aspect of the present application is applied in the preparation of hydrogen by ammonia cracking.

[0043] Compared with the prior art, the present application has the following advantages:

[0044] (1) The ammonia cracking catalyst provided by the present application has the following advantages: the non-noble metal active particles distributed on the surface of the perovskite oxide carrier are in-situ precipitated from the perovskite oxide, and are more uniformly distributed; the particle size is smaller than that of the active particles loaded by the traditional deposition method or impregnation method, and the reaction active area is larger, so the catalytic activity is higher; the non-noble metal active particles of the present application are more closely combined with the carrier, and the combination strength is higher, so the problem of performance degradation caused by agglomeration of active particles during long-term operation of the catalyst is avoided, and the stability is better; in addition, the perovskite oxide carrier of the present application exhibits Lewis base characteristics, which changes the electronic structure of the active metal, thereby optimizing the catalytic activity of the material; the alkaline earth metal elements such as Sr at A or A' sites act as adjuvants, further improving the overall activity of the catalyst.

[0045] (2) The present application is prepared by adopting sol-gel method or glycine-nitrate method, non-noble metal particles are in-situ precipitated at B or B' position of perovskite oxide, non-noble metal active component, perovskite oxide carrier and alkaline earth metal additive can be obtained at one time, the traditional repeated impregnation, repeated sintering and other processes are avoided, and the preparation steps are simplified.

[0046] (3) The ammonia cracking catalyst prepared by the present application has excellent catalytic activity and stability, for example, under the conditions of temperature 600℃ and space velocity 30000mL / (g·h), the ammonia cracking rate reaches more than 95%, and after 100h of stability test, the ammonia cracking rate still remains more than 95%, which can be comparable to the performance of traditional noble metal ruthenium-based catalyst, and is conducive to reducing the cost in the field of medium-temperature ammonia decomposition. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 XRD pattern of the ammonia cracking catalyst prepared for Example 4;

[0048] Figure 2 SEM pattern of the perovskite oxide prepared for Example 4 before and after reduction;

[0049] Figure 3 TEM pattern of the ammonia cracking catalyst prepared for Example 4;

[0050] Figure 4 Results of the ammonia cracking catalyst prepared for Example 4 after 100h of stability test. DETAILED DESCRIPTION

[0051] The content of the present application is further described in detail through specific examples. The raw materials, reagents or devices used in the examples can be obtained from conventional commercial channels or can be obtained by existing technical methods, unless otherwise specified. Unless otherwise specified, the test or test method is a conventional method in the art.

[0052] Example 1

[0053] La 0.6 Sr 0.4 Co 0.2 Ni 0.8 O 3-δ The ammonia cracking catalyst is prepared by a preparation method comprising the following steps:

[0054] (1) according to La 0.6 Sr 0.4 Co 0.2 Ni 0.8 O 3-δThe stoichiometric ratio of the ammonia cracking catalyst was prepared by adding 5.7704 g of lanthanum nitrate, 1.8802 g of strontium nitrate, 1.2928 g of cobalt nitrate and 5.1668 g of nickel nitrate into 200 mL of deionized water, stirring and dissolving to obtain a metal salt solution, and then adding 17.0682 g of citric acid and 12.9815 g of EDTA, stirring to obtain a metal salt complex solution;

[0055] (2) Ammonia was added dropwise to the metal salt complex solution, the pH value of the solution was adjusted to 10, and the solution was stirred to obtain a precursor solution;

[0056] (3) The precursor solution was heated at 80°C and stirred for 4 h to obtain a wet gel;

[0057] (4) The wet gel was placed in a vacuum drying oven at 180°C and -0.8 bar to further evaporate water to obtain a dry gel;

[0058] (5) The dry gel was placed in a muffle furnace and sintered at 850°C for 5 h to obtain a perovskite oxide;

[0059] (6) The perovskite oxide was placed in a tube furnace in a hydrogen atmosphere and reduced at 650°C for 2 h to obtain the ammonia cracking catalyst of the example.

[0060] Example 2

[0061] The difference from Example 1 is only that the type and amount of raw materials in step (1) are adjusted in Example 2, specifically: 5.7858 g of lanthanum nitrate, 1.8852 g of strontium nitrate, 1.7994 g of iron nitrate, 5.1807 g of nickel nitrate, 17.1138 g of citric acid, and 13.0162 g of EDTA; the remaining preparation steps are the same as in Example 1.

[0062] La 0.6 Sr 0.4 Fe 0.2 Ni 0.8 O 3-δ ammonia cracking catalyst was prepared in this example.

[0063] Example 3

[0064] The difference from Example 2 is only that the reduction time in step (6) is adjusted from 2 h to 4 h in Example 3; the remaining raw materials, amounts and preparation steps are the same as in Example 2.

[0065] La 0.6 Sr 0.4 Fe 0.2 Ni 0.8 O 3-δ ammonia cracking catalyst was prepared in this example.

[0066] Example 4

[0067] The difference from Example 3 is that the raw material amount in step (1) is adjusted in Example 4, specifically: 5.1744 g of lanthanum nitrate, 1.6860 g of strontium nitrate, 2.0116 g of iron nitrate, 5.7915 g of nickel nitrate, 17.2185 g of citric acid, and 13.0958 g of EDTA; the remaining preparation steps are the same as those of Example 3.

[0068] The perovskite oxide prepared in this example is (La 0.6 Sr 0.4 ) 0.8 Fe 0.2 Ni 0.8 O 3-δ ammonia decomposition catalyst.

[0069] Example 5

[0070] A Pr 0.5 Ba 0.5 Co 0.8 Fe 0.2 O 3-δ ammonia decomposition catalyst is prepared by a preparation method comprising the following steps:

[0071] (1) 7.2502 g of praseodymium nitrate, 4.3557 g of barium nitrate, 7.7608 g of cobalt nitrate, and 2.6933 g of iron nitrate are added to 50 mL of deionized water according to the stoichiometric ratio of the Pr 0.5 Ba 0.5 Co 0.8 Fe 0.2 O 3-δ ammonia decomposition catalyst, and stirred and dissolved to obtain a metal salt solution, and then 11.55 g of glycine is added and stirred to obtain a precursor solution;

[0072] (2) The precursor solution is heated at 80°C and stirred for 2 h to obtain a gel;

[0073] (3) The gel is heated to 267°C to cause the gel to spontaneously combust upon heating, and the ash powder after combustion is collected;

[0074] (4) The powder is placed in a muffle furnace and sintered at 850°C for 4 h to obtain a perovskite oxide;

[0075] (5) The perovskite oxide is placed in a tube furnace in a hydrogen atmosphere and reduced at 750°C for 4 h to obtain the ammonia decomposition catalyst of this example.

[0076] Example 6

[0077] The difference between Example 6 and Example 5 is that the kind and amount of metal salt in step (1) is adjusted in Example 6, specifically: 7.2502 g praseodymium nitrate, 3.5272 g strontium nitrate, 7.7608 g cobalt nitrate, and 2.6933 g iron nitrate; the rest of the preparation steps are the same as in Example 5.

[0078] Pr 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ ammonia cracking catalyst.

[0079] Example 7

[0080] The difference between Example 7 and Example 5 is that the kind and amount of metal salt in step (1) is adjusted in Example 7, specifically: 7.2168 g lanthanum nitrate, 3.5272 g strontium nitrate, 7.7608 g cobalt nitrate, and 2.6933 g iron nitrate; the rest of the preparation steps are the same as in Example 5.

[0081] La 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ ammonia cracking catalyst.

[0082] Example 8

[0083] The difference between Example 8 and Example 5 is that the kind and amount of metal salt in step (1) is adjusted in Example 8, specifically: 8.6602 g lanthanum nitrate, 2.8217 g strontium nitrate, 1.9402 g cobalt nitrate, and 10.7333 g iron nitrate; the rest of the preparation steps are the same as in Example 5.

[0084] La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ ammonia cracking catalyst.

[0085] Comparative Example 1 (non-in-situ dissolution nickel)

[0086] A Ni-La 0.6 Sr 0.4 CoO 3-δ ammonia cracking catalyst is prepared by the following steps:

[0087] (1) 0.5 g of La 0.6 Sr 0.4 Co 0.2 Ni 0.8 O 3-δThe stoichiometric ratio of the ammonia cracking catalyst was prepared by adding 5.7662 g of lanthanum nitrate, 1.8788 g of strontium nitrate and 6.4586 g of cobalt nitrate into 200 mL of deionized water, stirring and dissolving to obtain a metal salt solution, and then adding 17.0561 g of citric acid and 12.9723 g of EDTA, stirring to obtain a metal salt complex solution;

[0088] (2) Ammonia was added dropwise to the metal salt complex solution, the pH value of the solution was adjusted to 10, and stirring was performed to obtain a precursor solution;

[0089] (3) The precursor solution was heated at 80°C and stirred for 4 h to obtain a wet gel;

[0090] (4) The wet gel was placed in a vacuum drying oven at 180°C and -0.8 bar to further evaporate water to obtain a dry gel;

[0091] (5) The dry gel was placed in a muffle furnace and sintered at 850°C for 5 h to obtain a perovskite oxide La 0.6 Sr 0.4 CoO 3-δ ;

[0092] (6) 0.6 g of NiO and 0.4 g of the perovskite oxide La 0.6 Sr 0.4 CoO 3-δ obtained in step (5) were weighed and added to a ball mill jar, and ethanol was used as a dispersant to mill at 400 rpm for 1 h in a ball mill;

[0093] (7) The material after ball milling in step (6) was dried and placed in a muffle furnace, and reduced at 650°C in a hydrogen atmosphere for 2 h to obtain a Ni-La 0.6 Sr 0.4 CoO 3-δ ammonia cracking catalyst.

[0094] Comparative Example 2 (non-in-situ dissolution of nickel)

[0095] The difference from Comparative Example 1 is only that the amount of NiO and the perovskite oxide La 0.6 Sr 0.4 CoO 3-δ in step (6) is adjusted, specifically: 0.1 g of NiO and 0.9 g of the perovskite oxide La 0.6 Sr 0.4 CoO 3-δ ; and the remaining preparation steps are the same as those of Comparative Example 1.

[0096] Material characterization and performance test

[0097] 1. Material characterization

[0098] Figure 1 The XRD pattern of the ammonia cracking catalyst prepared in Example 4 can be seen that the ammonia cracking catalyst contains layered perovskite phase, strontium carbonate phase, Ni3Fe phase, indicating that the non-noble metal active component, perovskite oxide carrier and alkaline earth metal additive can be obtained at one time.

[0099] Figure 2 The SEM patterns of the perovskite oxide prepared in Example 4 before and after reduction can be seen from Figure 2 The surface of the perovskite oxide before reduction is smooth; from Figure 2 b) of FIG. 4, it can be seen that the surface of the perovskite oxide after reduction (ammonia cracking catalyst) precipitates active nanoparticles, proving the occurrence of in-situ dissolution phenomenon, and the active nanoparticles are embedded on the surface of the carrier and are closely combined.

[0100] Figure 3 The TEM pattern of the ammonia cracking catalyst prepared in Example 4 can be seen that the average particle size of the ammonia cracking catalyst particles is about 50 nm, and the surface thereof is distributed with Ni-Fe alloy particles with an average particle size of about 20 nm. Combined with Figure 2 It is further proved that the B-site metal of the ABO3-type perovskite oxide is dissolved from the crystal lattice under the reducing atmosphere and forms Ni-Fe alloy on the surface of the material according to the present application.

[0101] 2. Performance test

[0102] Ammonia cracking performance test: 0.1 g of ammonia cracking catalyst was mixed with gaseous SiO2 and then fixed in a glass tube to carry out ammonia cracking performance test by introducing ammonia. For Examples 1-4, Comparative Examples 1-2, the measurement conditions were temperature 600℃, space velocity 30000 mL / (g·h); for Examples 5-8, the measurement conditions were temperature 600℃, space velocity 18000 mL / (g·h). The results are shown in Table 1.

[0103] Table 1

[0104] Example 1 85.1％ Example 2 86.5％ Example 3 94.3％ Example 4 96.1％ Example 5 97.6％ Example 6 91％ Example 7 88％ Example 8 96％ Comparative Example 1 79.4％ Comparative Example 2 69.2％

[0105] As can be seen from Table 1, the ammonia cracking catalyst prepared in the examples of the present application exhibits excellent ammonia cracking catalytic activity, and the ammonia cracking rate of Example 4 can reach 96.1% under the conditions of 600℃ and 30000 mL / (g·h). Compared with the results of Comparative Examples 1-2, the ammonia cracking catalyst prepared in Examples 1-8 exhibits significantly higher ammonia cracking rate, and the reason is that the in-situ precipitated active metal of the ammonia cracking catalyst has smaller particle size, larger effective active area and stronger interaction between the metal and the carrier.

[0106] Figure 4The results of the 100 h stability test of the ammonia cracking catalyst prepared in Example 4 show that the ammonia cracking rate remains above 95% after the 100 h stability test at 600°C and 30000 mL / (g.h).

[0107] The above describes the preferred embodiments of the present application, but the present application is not limited to the above-described embodiments. Those skilled in the art can make various equivalent modifications or replacements without departing from the spirit of the present application, and these equivalent modifications or replacements are included in the scope defined by the claims of the present application.

Claims

1. An ammonia cracking catalyst characterized in that, The ammonia cracking catalyst comprises a non-noble metal active component, a perovskite oxide carrier and an alkaline earth metal additive, the non-noble metal active component is distributed on the surface of the perovskite oxide carrier in the form of nanoparticles, the non-noble metal active component is a non-noble metal alloy dissolved in-situ from the perovskite oxide, the perovskite oxide carrier is the perovskite oxide after the in-situ dissolution of the non-noble metal active component, and the alkaline earth metal additive is loaded on the perovskite oxide carrier. The chemical formula of the ammonia cracking catalyst is (A 1-x A' x ) z B 1-y B' y O 3-δ , wherein the A element is selected from La or Pr, the A' element is selected from Sr or Ba; the B and B' elements are respectively and independently selected from two of Fe, Co and Ni; 0.2≤x≤0.8, 0.2≤y≤0.8, 0.5≤z≤1; and δ represents oxygen defects.

2. The ammonia cracking catalyst of claim 1, wherein The alkaline earth metal additive comprises one or more of oxides, hydroxides and carbonates of alkaline earth metals.

3. Process for the preparation of an ammonia cracking catalyst as claimed in claim 1 or 2, characterized in that The ammonia cracking catalyst is prepared by a sol-gel method or a glycine-nitrate method.

4. The production method according to claim 3, characterized by, When the sol-gel method is used to prepare the ammonia cracking catalyst, the following steps are included: (1) a metal salt solution is prepared according to the stoichiometric ratio of the ammonia cracking catalyst, and then mixed with a complexing agent to obtain a metal salt complex solution; (2) the pH of the metal salt complex solution is adjusted to alkaline to obtain a precursor solution; (3) the precursor solution is heated, stirred and dried to obtain a dry gel; (4) the dry gel is sintered to obtain a perovskite oxide; (5) the perovskite oxide is placed in a reducing atmosphere for reduction treatment to cause the non-noble metal active component in the perovskite oxide to be dissolved in-situ, thereby obtaining the ammonia cracking catalyst.

5. The preparation method according to claim 4, characterized in that, The ratio of the molar amount of the complexing agent to the total molar amount of metal ions in the metal salt solution is (1-3):

1.

6. The preparation method according to claim 3, characterized in that, When the glycine-nitrate method is used to prepare the ammonia cracking catalyst, the following steps are included: (1) a metal salt solution is prepared according to the stoichiometric ratio of the ammonia cracking catalyst, and then mixed with glycine to obtain a precursor solution; (2) the precursor solution is heated and stirred to obtain a gel; (3) the gel is heated, and after the gel is self-ignited by heat, a powder is obtained; (4) the powder is sintered to obtain a perovskite oxide; (5) the perovskite oxide is placed in a reducing atmosphere for reduction treatment to cause the non-noble metal active component in the perovskite oxide to be dissolved in-situ, thereby obtaining the ammonia cracking catalyst.

7. The production method according to claim 6, characterized by, The ratio of the molar amount of glycine to the total molar amount of metal ions in the metal salt solution is (1-2.31):

1.

8. The production method according to claim 4 or 6, characterized by, The temperature of the reduction is 600-800℃, and the time of the reduction is 2-8h.

9. Use of the ammonia cracking catalyst of claim 1 or 2 in the production of hydrogen by ammonia cracking.

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