Supported nickel catalyst, preparation method thereof and method for producing hydrogen through ammonia gas decomposition

Abstract

The invention relates to a supported nickel catalyst, a preparation method and a method for producing hydrogen through ammonia gas decomposition, and belongs to the technical field of catalysts.The supported nickel catalyst comprises a molecular sieve carrier and nickel ions supported on the molecular sieve carrier, the molecular sieve carrier is an SOD molecular sieve, and in the SOD molecular sieve, the nickel ions are loaded on the molecular sieve carrier. The molar ratio of alkali metal to aluminum to silicon is (1-4): 1: 1; the total mass of the supported nickel catalyst is 100%, and the content of the nickel ions is 0.5-20%. The supported nickel catalyst provided by the invention has the advantages of abundant microporous structures, short crystallization time and low cost, can reduce the temperature required by ammonia gas decomposition and the temperature at which ammonia gas is completely decomposed, greatly reduces the production cost, and has huge application potential.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and in particular to a supported nickel catalyst and a preparation method thereof, and a method for producing hydrogen by decomposing ammonia. Background Art

[0002] Traditional fossil fuels, when used in combustion, chemical processing, and other processes, inevitably release large amounts of carbon dioxide, causing environmental problems. Therefore, the development and utilization of non-carbon renewable energy sources are of great significance. Hydrogen (H2) is considered a clean fuel due to its high energy density (120MJ / kg) and the fact that combustion only produces water and no carbon dioxide emissions. However, H2's wide flammability range and low ignition energy (0.17kJ / mol) make it subject to significant risks during transportation and storage. Its direct use is greatly hindered by the lack of effective storage and transportation (storing H2 in cylinders requires a high pressure of approximately 700 bar). Therefore, the development of a high-density, low-cost, highly efficient "hydrogen carrier" that can be decomposed on demand to produce hydrogen is considered the key to solving the problem of effective hydrogen energy utilization.

[0003] Ammonia (NH3), containing 17.8wt% H2, can be decomposed to produce nitrogen (N2) and hydrogen (H2) in a volume ratio of 3:1. Compared with carbon-based hydrogen carriers such as methanol and methane that produce carbon dioxide during hydrogen production, ammonia has attracted widespread attention for its high hydrogen yield and zero carbon emissions [Valera-Medina, A. et al, Energy. Fuels. 2021, 35, 6964]. Ammonia decomposition to produce hydrogen provides new possibilities for the low-carbon transformation of the hydrogen energy economy [Goetsch, DA et al, WO Patent, 2001, 0187770]. For more than 20 years, the development of efficient catalysts has been the key to ammonia decomposition to produce hydrogen technology.

[0004] Previously, catalysts for hydrogen production from ammonia decomposition primarily consisted of supported alloy catalysts or composite catalysts based on ruthenium, nickel, and iron [Schuth, R. et al., Energy. Environ. Sci., 2012, 5, 6278]. Ruthenium- and nickel-based catalysts are currently the primary research areas. Ruthenium-based catalysts exhibit high ammonia decomposition activity and can decompose ammonia at temperatures between 350 and 550°C [CN107876796B; Nagaoka, K. et al., Sci Advs., 2017, 3, e1602747]. However, the scarcity and high cost of ruthenium have limited their large-scale commercial application. Nickel-based catalysts are widely used, but suffer from disadvantages such as poor low-temperature activity, low processing capacity, and rapid deactivation at high temperatures (600-1000°C). Consequently, current catalysts generally suffer from high production costs, low efficiency, high operating temperatures, and short service lives, significantly limiting the large-scale commercial application of hydrogen production from ammonia decomposition.

[0005] Therefore, there is a need to provide a new catalyst to meet application requirements. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides a supported nickel catalyst and a preparation method, and a method for producing hydrogen by decomposing ammonia.

[0007] In a first aspect, the present invention provides a supported nickel catalyst, comprising a molecular sieve support and nickel supported on the molecular sieve support, wherein:

[0008] The molecular sieve carrier is a SOD molecular sieve, in which the molar ratio of alkali metal, aluminum and silicon is (1-4):1:1;

[0009] Based on the total mass of the supported nickel catalyst being 100%, the nickel content is 0.5-20%.

[0010] As a preferred technical solution of the present invention, the nickel content is 7-11%.

[0011] As a preferred technical solution of the present invention, the molar ratio of the alkali metal, aluminum and silicon is (2-3):1:1.

[0012] As a preferred technical solution of the present invention, the alkali metal includes sodium, or a combination of sodium and any one or at least two of potassium, rubidium or cesium.

[0013] In a second aspect, the present invention provides a method for preparing the supported nickel catalyst according to the first aspect, the preparation method comprising the following steps:

[0014] (1) mixing a non-elemental aluminum source, a silicon source, and sodium hydroxide in water and performing a hydrothermal reaction to obtain a SOD molecular sieve or an aqueous solution containing the SOD molecular sieve;

[0015] (2) SOD molecular sieve or an aqueous solution containing SOD molecular sieve is mixed with nickel salt to obtain the supported nickel catalyst.

[0016] As a preferred technical solution of the present invention, the temperature of the hydrothermal reaction is 80-120° C., and / or the pressure of the hydrothermal reaction is 0.01-0.1 MPa.

[0017] As a preferred technical solution of the present invention, the mixing method in step (2) includes any one of coprecipitation, impregnation or ball milling or a combination of at least two thereof, the mixing method is coprecipitation or impregnation, and step (2) also includes drying and calcining.

[0018] In a third aspect, the present invention provides use of the supported nickel catalyst described in the first aspect in a catalytic ammonia decomposition reaction to produce hydrogen.

[0019] In a fourth aspect, the present invention provides a method for producing hydrogen by decomposing ammonia, the method comprising:

[0020] (1) placing the supported nickel catalyst described in the first aspect in a reactor;

[0021] (2) Ammonia is introduced into the reactor and decomposed under the catalysis of the catalyst to generate hydrogen and nitrogen;

[0022] (3) Separate nitrogen and hydrogen to obtain hydrogen.

[0023] As a preferred technical solution of the present invention, the decomposition reaction temperature is 200-600 ° C, the pressure is 0.5-10.0 MPa, and the volume space velocity is 3000-30000 h -1 .

[0024] The technical solution provided by the embodiment of the present invention has the following advantages compared with the prior art:

[0025] The supported nickel catalyst provided by the present invention has the advantages of rich microporous structure, short crystallization time and low cost. It can reduce the temperature required for ammonia decomposition and the temperature at which ammonia is completely decomposed, greatly reducing production costs and having huge application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0028] Figure 1 A schematic diagram of the catalytic principle of the supported nickel catalyst provided by the present invention for decomposing ammonia to produce hydrogen;

[0029] Figure 2 The X-ray diffraction spectrum comparison diagram of the SOD molecular sieve and the supported nickel catalyst prepared in Example 1;

[0030] Figure 3 TEM of the supported nickel catalyst prepared in Example 1 Figure 1 ;

[0031] Figure 4 TEM of the supported nickel catalyst prepared in Example 1 Figure 2 ;

[0032] Figure 5 This is a comparison of the X-ray diffraction spectra before and after the supported nickel catalyst in Application Example 1 catalyzed ammonia decomposition to produce hydrogen;

[0033] Figure 6 This is a diagram showing the reaction results of ammonia decomposition to produce hydrogen in Application Example 1. DETAILED DESCRIPTION

[0034] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the scheme of the present invention will be further described below. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features therein can be combined with each other.

[0035] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all the embodiments.

[0036] Currently, ruthenium and / or nickel are commonly used as metal catalysts for the decomposition of ammonia to produce hydrogen. Even if the ruthenium or nickel is modified to a certain extent, there are still disadvantages such as the catalyst operating temperature is too high, the decomposition efficiency is poor, and the catalyst stability is poor. Therefore, the present invention provides a supported nickel catalyst with a low catalyst operating temperature and good stability.

[0037] In a first aspect, the present invention provides a supported nickel catalyst, comprising a molecular sieve support and nickel supported on the molecular sieve support, wherein:

[0038] The molecular sieve carrier is a SOD molecular sieve, in which the molar ratio of alkali metal, aluminum and silicon is (1-4):1:1, for example, 1.5:1:1, 2:1:1, 2.5:1:1, 3:1:1, 3.5:1:1, etc.;

[0039] Based on the total mass of the supported nickel catalyst as 100%, the nickel content is 0.5-20%, for example, 1%, 2%, 5%, 8%, 10%, 12%, 15%, 18%, etc.

[0040] The supported nickel catalyst provided by the present invention has the advantages of rich microporous structure, short crystallization time and low cost. It can reduce the temperature required for ammonia decomposition and the temperature at which ammonia is completely decomposed, greatly reducing production costs and having huge application potential. Specifically:

[0041] The SOD cage of the SOD molecular sieve includes a large amount of alkali metals, especially sodium. The SOD cage plays a good role in fixing sodium ions. The presence of sodium ions can provide a large number of electrons to the sites where metallic nickel exists. Therefore, it can accelerate the activation of metallic nickel, thereby achieving the purpose of lowering the decomposition temperature of ammonia and the complete decomposition temperature.

[0042] Moreover, compared with other porous materials, the space inside the SOD cage is closer to the molecular size of ammonia, and can more effectively play the role of nano-confinement, destroying the adsorption of ammonia molecules in a highly symmetrical form. Therefore, ammonia molecules are more easily polarized and activated, and further promote their dissociation by nickel at a lower temperature.

[0043] At the same time, since the space inside the SOD cage only allows hydrogen to pass through, and nitrogen cannot enter the cage and can only bypass the cage, therefore, after the ammonia decomposition reaction occurs in each SOD cage, hydrogen and nitrogen can be effectively separated, which promotes the progress of the ammonia decomposition reaction and ensures that ammonia can be completely decomposed (catalytic principle such as Figure 1 As shown, Figure 1 Schematic diagram of the catalytic principle of the supported nickel catalyst provided by the present invention for decomposing ammonia to produce hydrogen).

[0044] Therefore, the present invention prepares a supported nickel catalyst by loading metallic nickel onto a sodium ion-rich SOD molecular sieve, which can realize ammonia decomposition to produce hydrogen in a medium temperature range (200-600°C, or even 200-550°C), and the ammonia can be completely decomposed. That is, the supported nickel catalyst provided by the present invention can be used in environmentally friendly, highly stable, and long-cycle industrial production of ammonia decomposition to produce hydrogen.

[0045] As a preferred technical solution of the present invention, the nickel content is 7-11%, for example, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, etc.

[0046] In the present invention, when the nickel content is within the range of 7-11%, the amount of nickel used can be saved and the catalytic efficiency of hydrogen production by decomposing ammonia is more excellent.

[0047] As a preferred technical solution of the present invention, the molar ratio of the alkali metal, aluminum and silicon is (2-3):1:1.

[0048] As a preferred technical solution of the present invention, the alkali metal includes sodium, or a combination of sodium and any one or at least two of potassium, rubidium or cesium.

[0049] Alkali metals are introduced into SOD molecular sieves. The addition of alkali metal elements can change the morphology and electronic state of Ni active sites, or reduce the binding energy between Ni substances and N atoms, thereby improving the catalytic performance of the catalyst.

[0050] In a second aspect, the present invention provides a method for preparing the supported nickel catalyst according to the first aspect, the preparation method comprising the following steps:

[0051] (1) mixing a non-elemental aluminum source, a silicon source, and sodium hydroxide in water and performing a hydrothermal reaction to obtain a SOD molecular sieve or an aqueous solution containing the SOD molecular sieve;

[0052] (2) SOD molecular sieve or an aqueous solution containing SOD molecular sieve is mixed with nickel salt to obtain the supported nickel catalyst.

[0053] The present invention prepares a supported nickel catalyst by preparing a SOD molecular sieve or an aqueous solution containing the SOD molecular sieve and mixing the solution with a nickel salt (or a solution containing the nickel salt). The preparation method of the supported nickel catalyst provided by the present invention is simple and easy, has low production cost, and is conducive to industrial promotion.

[0054] As a preferred technical solution of the present invention, the temperature of the hydrothermal reaction is 80-120°C, for example, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, etc., and / or the pressure of the hydrothermal reaction is 0.01-0.1MPa, for example, 0.02MPa, 0.03MPa, 0.04MPa, 0.05MPa, 0.06MPa, 0.08MPa, etc.

[0055] As a preferred technical solution of the present invention, the mixing method in step (2) includes any one of coprecipitation, impregnation or ball milling or a combination of at least two thereof, the mixing method is coprecipitation or impregnation, and step (2) also includes drying and calcining.

[0056] As a preferred technical solution of the present invention, if the nickel salt is used in the form of an aqueous solution, a coprecipitation or impregnation method can be used, followed by drying and / or calcination, and can also be formed and granulated. The forming method includes but is not limited to extrusion molding, ball rolling or spraying methods.

[0057] As a preferred technical solution of the present invention, if the nickel salt and the SOD molecular sieve are both in solid state, nickel loading can be achieved by physical blending such as grinding and blending.

[0058] As a specific embodiment of the present invention, the preparation method of the supported nickel catalyst comprises the following steps:

[0059] (1) weighing a non-elemental aluminum source, a silicon source, and sodium hydroxide according to a formula amount and mixing them in ultrapure water, and then performing a hydrothermal reaction at 80-120° C. to obtain an aqueous solution containing a SOD molecular sieve, and optionally centrifuging, washing, and drying the aqueous solution to obtain a SOD molecular sieve;

[0060] (2) After mixing the nickel salt aqueous solution with the SOD molecular sieve, the pH value is adjusted using sodium hydroxide, and after aging, the mixture is calcined at 300°C for 1 hour and at 600°C for 3 hours, and then formed and granulated;

[0061] or:

[0062] The nickel salt aqueous solution and the SOD aqueous solution are mixed and aged, calcined at 300°C for 1 hour and 600°C for 3 hours, and then formed and granulated;

[0063] As a specific embodiment of the present invention, the preparation method also includes reducing the supported nickel catalyst, including: reducing the product obtained above in an atmosphere containing hydrogen, reducing the nickel ions to metallic nickel for decomposing ammonia to produce hydrogen, and further, the reduction temperature is 550°C and the time is 2 hours.

[0064] The step of reducing the supported nickel catalyst described in the present invention can be carried out in conjunction with the process of decomposing ammonia to produce hydrogen. In the reactor for decomposing ammonia to produce hydrogen, the temperature is first increased to reduce the catalyst, and then the temperature is lowered to a certain temperature before ammonia is introduced to decompose and produce hydrogen.

[0065] In a third aspect, the present invention provides use of the supported nickel catalyst described in the first aspect in a catalytic ammonia decomposition reaction to produce hydrogen.

[0066] The supported nickel catalyst provided by the present invention can effectively avoid the problems of high operating temperature and high cost of nickel-based catalysts, greatly reduces production costs and has excellent catalytic effect.

[0067] In a fourth aspect, the present invention provides a method for producing hydrogen by decomposing ammonia, the method comprising:

[0068] (1) placing the supported nickel catalyst described in the first aspect in a reactor;

[0069] (2) Ammonia is introduced into the reactor and decomposed under the catalysis of the catalyst to generate hydrogen and nitrogen;

[0070] (3) Separate nitrogen and hydrogen to obtain hydrogen.

[0071] As a preferred technical solution of the present invention, the temperature of the decomposition reaction is 200-600°C, for example, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, the pressure is 0.5-10.0 MPa, for example, 1 MPa, 2 MPa, 3 MPa, 4 MPa, 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa, etc., and the volume space velocity is 3000-30000 h -1 , for example 5000h -1, 6000h -1 , 8000h -1 、10000h -1 、12000h -1 、15000h -1 、18000h -1 、20000h -1 、22000h -1 , 25000h -1 , 28000h -1 wait.

[0072] As a preferred technical solution of the present invention, the device used for separating hydrogen and nitrogen can be a membrane separation device, a PSA separator or a cryogenic distillation tower.

[0073] The following is explained through specific examples:

[0074] Example 1

[0075] This embodiment provides a supported nickel catalyst and a preparation method thereof, wherein:

[0076] The supported nickel catalyst consists of a SOD molecular sieve carrier and nickel supported on the surface of the carrier; in the SOD molecular sieve, the molar ratio of sodium, aluminum and silicon is 2.732:1:1; based on the total mass of the supported nickel catalyst being 100%, the content of nickel ions is 7%.

[0077] The preparation method is as follows:

[0078] (1) Preparation of SOD molecular sieve

[0079] Take a clean container, add ultrapure water, mix sodium aluminate, sodium hydroxide and sodium silicate nonahydrate in ultrapure water at a molar ratio of 7.5 (Na2O): 1.0 (A12O3): 2.0 (SiO2): 165 (H2O) (sodium hydroxide is excessive) to prepare a gel, crystallize at 100°C for 12 hours, centrifuge, wash and dry the precipitate to obtain a SOD molecular sieve;

[0080] (2) Preparation of supported nickel catalyst

[0081] A 1 mol / L nickel nitrate aqueous solution was prepared according to a nickel content of 7%, the SOD molecular sieve and the nickel nitrate aqueous solution were stirred and mixed at 600 r / min, and then a 0.2 mol / L sodium hydroxide aqueous solution was added dropwise until the pH value of the solution was 9. The mixture was stirred and aged for 2 h, filtered, washed, dried, and calcined at 300°C in an air atmosphere for 1 h and 600°C for 3 h to obtain a supported nickel catalyst.

[0082] Application Example 1

[0083] This application example provides a method for producing hydrogen by decomposing ammonia, as follows:

[0084] (1) The spherical catalyst (40-60 mesh) obtained in Example 1 was filled into a fixed reactor;

[0085] (2) In an inert gas atmosphere, the catalyst was heated to 550°C, and then hydrogen was introduced for reduction reaction for 2 h. As the inert gas was introduced, the temperature was lowered to 300°C;

[0086] (3) After cooling, ammonia gas was introduced to cause decomposition reaction at a flow rate of 50 mL / min (volume space velocity of 6000 mL·h -1 ·g -1 ), the reaction pressure is 0.05MPa, and the temperature is raised by 50°C to 550°C every 1h to complete the reaction and obtain hydrogen and nitrogen;

[0087] (3) The mixed gas of hydrogen and nitrogen is separated by a nitrogen-hydrogen separation unit to obtain high-purity hydrogen.

[0088] Performance Test 1

[0089] (1) X-ray diffraction analysis was performed on the SOD molecular sieve and the supported nickel catalyst obtained in Example 1. The results were as follows:

[0090] Figure 2 The X-ray diffraction spectrum comparison diagram of the SOD molecular sieve and the supported nickel catalyst prepared in Example 1 is shown in FIG. Figure 2 In the figure, after the SOD molecular sieve is loaded with metal oxide, the diffraction peak position of SOD does not change, indicating that the preparation method provided by the present invention does not have any effect on the SOD molecular sieve carrier itself; at the same time, there is no diffraction peak of nickel oxide in the figure, indicating that the preparation method provided by the present invention can ensure that nickel oxide is uniformly dispersed on the SOD molecular sieve.

[0091] (2) The supported nickel catalyst obtained in Example 1 was subjected to microscopic morphology characterization, and the results were as follows:

[0092] Figure 3 and Figure 4 This is a TEM image of the supported nickel catalyst (reduced) prepared in Example 1. It can be seen from the figure that nickel is successfully supported on the surface of the SOD molecular sieve, that is, the supported nickel catalyst is successfully prepared by the preparation method provided by the present invention.

[0093] (3) X-ray diffraction analysis of the catalyst before and after the ammonia decomposition reaction to produce hydrogen in Example 1 was performed. The results are as follows:

[0094] Figure 5This is a comparison diagram of the X-ray diffraction spectra before and after the supported nickel catalyst of Application Example 1 catalyzes the decomposition of ammonia to produce hydrogen. As can be seen from the figure, the diffraction peaks of the catalyst do not change before and after the catalytic decomposition of ammonia to produce hydrogen, indicating that the entire catalytic process does not change the skeleton of the molecular sieve and can maintain its original form. This proves that the supported nickel catalyst provided by the present invention has better stability.

[0095] (4) The catalyst was evaluated for ammonia decomposition reaction using a single-channel reactor. The results are as follows:

[0096] Figure 6 This is a diagram showing the reaction results of ammonia decomposition to produce hydrogen in Application Example 1. As can be seen from the figure, ammonia begins to decompose at 300°C, and at 550°C, the conversion rate of the decomposition reaction is above 99.9%. This shows that the use of the supported nickel catalyst provided in Example 1 of the present invention can reduce the decomposition temperature of ammonia and the reaction temperature for complete decomposition of ammonia, and ammonia can be completely decomposed at 550°C.

[0097] Example 2

[0098] This embodiment provides a supported nickel catalyst and a preparation method thereof.

[0099] The supported nickel catalyst consists of a SOD molecular sieve carrier and nickel ions supported on the surface of the carrier; in the SOD molecular sieve, the molar ratio of sodium, aluminum and silicon is 7.5:1:1; based on the total mass of the supported nickel catalyst being 100%, the content of nickel ions is 7%.

[0100] The preparation method is as follows:

[0101] (1) Preparation of SOD molecular sieve

[0102] Take a clean container, add ultrapure water, mix sodium aluminate, sodium hydroxide and sodium silicate nonahydrate in ultrapure water at a molar ratio of 7.5 (Na2O):1.0 (A12O3):2.0 (SiO2):165 (H2O) to prepare a gel, and crystallize at 100°C for 12 hours to obtain an alkaline solution containing SOD molecular sieve;

[0103] (2) Preparation of supported nickel catalyst

[0104] A 1 mol / L nickel nitrate aqueous solution was prepared according to a nickel ion ratio of 7%, and the solution containing SOD molecular sieve and the nickel nitrate aqueous solution were stirred and mixed at 600 r / min, aged for 2 h, filtered and washed, dried, calcined at 300 ° C for 1 h, and calcined at 600 ° C for 3 h to obtain a supported nickel catalyst.

[0105] Example 3

[0106] This embodiment provides a supported nickel catalyst and a preparation method thereof.

[0107] The difference from Example 1 is that in this example, ammonia water is used to adjust the pH value in step (2).

[0108] Example 4

[0109] This embodiment provides a supported nickel catalyst and a preparation method thereof.

[0110] The difference from Example 3 is that, in this embodiment, step (1) further includes the following steps after the SOD molecular sieve is prepared:

[0111] The SOD molecular sieve was placed in a 0.1 mol / L ammonium chloride solution and mixed evenly according to the molecular sieve: solution mass ratio of 1:30. The mixture was stirred in an 80°C oil bath for 6 h. The precipitate was centrifuged, washed and dried, and calcined at 550°C for 2 h. The above process was repeated twice to obtain the H-SOD molecular sieve.

[0112] Example 5

[0113] This embodiment provides a supported nickel catalyst and a preparation method thereof.

[0114] The difference from Example 3 is that, in this embodiment, step (1) further includes the following steps after the SOD molecular sieve is prepared:

[0115] The SOD molecular sieve was placed in a 0.1 mol / L ammonium chloride solution and mixed evenly according to the molecular sieve: solution mass ratio of 1:30. The mixture was stirred in an 80°C oil bath for 6 h. The precipitate was centrifuged, washed and dried, and calcined at 550°C for 2 h. The above process was repeated twice to obtain the H-SOD molecular sieve.

[0116] Prepare 1 mol / L potassium nitrate solution, mix H-SOD molecular sieve and solution at a molecular sieve: solution mass ratio of 1:30, stir in an oil bath at 70°C for 2 h, centrifuge, wash and dry the precipitate, and calcine at 550°C for 2 h to obtain K-SOD.

[0117] Example 6

[0118] This embodiment provides a supported nickel catalyst and a preparation method thereof.

[0119] The difference from Example 3 is that, in this embodiment, step (1) further includes the following steps after the SOD molecular sieve is prepared:

[0120] The SOD molecular sieve was placed in a 0.1 mol / L ammonium chloride solution and mixed evenly according to the molecular sieve: solution mass ratio of 1:30. The mixture was stirred in an 80°C oil bath for 6 h. The precipitate was centrifuged, washed and dried, and calcined at 550°C for 2 h. The above process was repeated twice to obtain the H-SOD molecular sieve.

[0121] Prepare 1 mol / L rubidium nitrate solution, mix H-SOD molecular sieve and solution at a molecular sieve: solution mass ratio of 1:30, stir in an oil bath at 70°C for 2 h, centrifuge, wash and dry the precipitate, and calcine at 550°C for 2 h to obtain Rb-SOD.

[0122] Example 7

[0123] This embodiment provides a supported nickel catalyst and a preparation method thereof.

[0124] The difference from Example 1 is that, in this embodiment, step (2) is: according to the nickel ion ratio of 7%, SOD molecular sieve and nickel nitrate hexahydrate are put into a ball mill and ball milled for 1 hour to obtain a uniformly mixed powdered supported nickel catalyst.

[0125] Example 8

[0126] This embodiment provides a supported nickel catalyst and a preparation method thereof.

[0127] The difference from Example 1 is that, in this embodiment, step (2) is: preparing a nickel nitrate aqueous solution according to a nickel ion ratio of 7%, adding the SOD molecular sieve to the nickel nitrate aqueous solution for immersion and stirring, drying at 80°C for 10 hours, calcining at 300°C for 1 hour, and calcining at 600°C for 3 hours.

[0128] Example 9

[0129] This embodiment provides a supported nickel catalyst and a preparation method thereof.

[0130] The difference from Example 1 is that, in this embodiment, step (2) is: nickel oxide is taken according to a nickel ion ratio of 7%, and is placed in a mortar with SOD molecular sieves, and ground for 20 minutes.

[0131] Examples 10-13

[0132] This embodiment provides a supported nickel catalyst and a preparation method thereof.

[0133] The difference from Example 1 is that in this embodiment, the nickel ion accounts for 3% (Example 10), 5% (Example 11), 9% (Example 12), and 11% (Example 13).

[0134] Examples 14-17

[0135] This embodiment provides a supported nickel catalyst and a preparation method thereof.

[0136] The difference from Example 2 is that in this example, the nickel ion accounts for 3% (Example 14), 5% (Example 15), 9% (Example 16), and 11% (Example 17).

[0137] Comparative Example 1

[0138] This comparative example provides a supported nickel catalyst and a preparation method thereof.

[0139] The difference from Example 1 is that, in this comparative example, step (1) is: take a clean container, add ultrapure water, sodium aluminate, sodium hydroxide and sodium silicate nonahydrate, and prepare a gel with a molar ratio of 3.165 (Na2O):1.0 (A12O3):2.0 (SiO2):160 (H2O), and crystallize at 100°C for 4h; after centrifugation, washing and drying, 4A molecular sieve is obtained.

[0140] Comparative Example 2

[0141] This comparative example provides a supported nickel catalyst and a preparation method thereof.

[0142] The difference from Example 1 is that, in this comparative example, step (1) is: take a clean container, add ultrapure water, sodium aluminate, sodium hydroxide and sodium silicate nonahydrate, and prepare a gel with a molar ratio of 5.5 (Na2O): 1.0 (A12O3): 1.65 (K2O): 2.0 (SiO2): 143 (H2O), let it stand at 70°C for 6 hours, and crystallize at 95°C for 3 hours; after centrifugation, washing and drying, 13X molecular sieve is obtained.

[0143] Comparative Example 3

[0144] This comparative example provides a supported nickel catalyst and a preparation method thereof.

[0145] The difference from Example 1 is that, in this comparative example, step (1) is: take a clean container, add ultrapure water, sodium aluminate, sodium hydroxide, tetraethyl silicate and tetrapropylammonium hydroxide, and prepare a gel with a molar ratio of 100 (SiO2):1.1 (A12O3):2 (Na2O):1.0 (TPAOH):1920 (H2O), and crystallize at 170°C for 36 hours; after centrifugation, washing and drying, ZSM-5 molecular sieve is obtained.

[0146] Application Example 2-17

[0147] This application example provides a method for producing hydrogen by decomposing ammonia.

[0148] The difference from Application Example 1 is that in this application example, the catalyst used is the catalyst provided in Example 2-17.

[0149] Application Examples 18-20

[0150] This application example provides a method for producing hydrogen by decomposing ammonia.

[0151] The difference from Application Example 1 is that in this application example, the volumetric space velocity of ammonia is 3000 mL·h -1 ·g -1 (Application Example 18), 15000 mL·h -1 ·g -1 (Application Example 19), 30000 mL·h -1 ·g -1 (Application Example 20).

[0152] Comparative Examples 1-3

[0153] This comparative example provides a method for producing hydrogen by decomposing ammonia.

[0154] The difference from Application Example 1 is that in this comparative example, the catalyst used is the catalyst provided in Comparative Examples 1-3.

[0155] Performance Test 2

[0156] The ammonia conversion rate at different temperature stages was tested according to the test method in Performance Test 1. The results are shown in Table 1:

[0157] Table 1

[0158]

[0159] As can be seen from the examples and performance tests, the supported nickel catalyst provided by the present invention has a low operating temperature, ammonia can begin to decompose at 300°C, and has an excellent conversion rate at 550°C, preferably reaching 94% and even 100%.

[0160] From the comparison of Application Examples 1-2 and Application Examples 3-9, it can be seen that in the present invention, the catalytic efficiency of the catalyst can be increased by adopting the co-precipitation method and adjusting the pH value with sodium hydroxide; from the comparison of Application Examples 1-2 and Application Examples 10-17, it can be seen that when the nickel ion content is in the range of 7-11%, the catalytic efficiency for the decomposition of ammonia to produce hydrogen is the highest, which can reach 100%.

[0161] From the comparison between the application examples and the comparative examples, it can be seen that in the present invention, the introduction of SOD molecular sieve as a catalyst carrier can reduce the temperature required for the decomposition of ammonia and the temperature at which ammonia is completely decomposed.

[0162] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the element.

[0163] The foregoing description is intended only to provide specific embodiments of the present invention, which will enable those skilled in the art to understand and implement the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not intended to be limited to the embodiments described herein, but is to be construed in the widest manner consistent with the principles and novel features disclosed herein.

Claims

1. A supported nickel catalyst, characterized in that The supported nickel catalyst comprises a molecular sieve support and nickel supported on the molecular sieve support, wherein: The molecular sieve carrier is a SOD molecular sieve, in which the molar ratio of alkali metal, aluminum and silicon is (1-4):1:1; Based on the total mass of the supported nickel catalyst being 100%, the nickel content is 0.5-20%.

2. The supported nickel catalyst according to claim 1, wherein The nickel content is 7-11%.

3. The supported nickel catalyst according to claim 1, wherein The molar ratio of the alkali metal, aluminum and silicon is (2-3):1:

1.

4. The supported nickel catalyst according to claim 1, wherein The alkali metal includes sodium, or a combination of sodium and any one or at least two of potassium, rubidium or cesium.

5. The method for preparing the supported nickel catalyst according to any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: (1) mixing a non-elemental aluminum source, a silicon source, and sodium hydroxide in water and performing a hydrothermal reaction to obtain a SOD molecular sieve or an aqueous solution containing the SOD molecular sieve; (2) SOD molecular sieve or an aqueous solution containing SOD molecular sieve is mixed with nickel salt to obtain the supported nickel catalyst.

6. The preparation method according to claim 5, characterized in that The temperature of the hydrothermal reaction is 80-120° C., and / or the pressure of the hydrothermal reaction is 0.01-0.1 MPa.

7. The preparation method according to claim 5, characterized in that The mixing method in step (2) includes any one of coprecipitation, impregnation or ball milling or a combination of at least two thereof, wherein the mixing method is coprecipitation or impregnation, and step (2) further includes drying and calcining.

8. Use of the supported nickel catalyst according to any one of claims 1 to 4 in a catalytic ammonia decomposition reaction to produce hydrogen.

9. A method for producing hydrogen by decomposing ammonia, characterized in that: The method comprises: (1) placing the supported nickel catalyst according to any one of claims 1 to 4 in a reactor; (2) Ammonia is introduced into the reactor and decomposed under the catalysis of the catalyst to generate hydrogen and nitrogen; (3) Separate nitrogen and hydrogen to obtain hydrogen.

10. The method according to claim 9, characterized in that The decomposition reaction temperature is 200-600°C, the pressure is 0.5-10.0 MPa, and the volume space velocity is 3000-30000 h -1 .

Images