Rare earth silicate supported ammonia decomposition catalyst as well as preparation method and application thereof

Abstract

The invention discloses a rare earth silicate supported ammonia decomposition catalyst as well as a preparation method and application thereof, and belongs to the technical field of catalyst preparation and heterogeneous catalysis. The catalyst comprises a carrier and an active component, wherein the carrier is rare earth silicate, and the active component is a single metal or double metal combination or multi-metal combination of iron, cobalt, nickel and ruthenium. In the preparation method, the active components are promoted to be uniformly dispersed on the surface of the rare earth silicate carrier through an optimized dipping-calcining process. The constructed catalyst has strong metal-carrier interaction, shows excellent ammonia decomposition activity in a temperature interval of 350-650 DEG C, and has excellent long-term stability. The technology is simple and convenient in preparation process, low in cost, environment-friendly, suitable for being applied to the fields of distributed hydrogen production systems and ammonia decomposition tail gas treatment, and outstanding in industrial application prospect and market development potential.

Description

Technical Field

[0001] This application relates to a rare earth silicate supported ammonia decomposition catalyst, its preparation method and application, belonging to the field of catalyst preparation and heterogeneous catalysis technology. Background Technology

[0002] Hydrogen energy, as a zero-carbon and highly efficient secondary energy source, is considered a core carrier supporting the transformation of the energy structure. However, the large-scale application of hydrogen energy has always been limited by technological bottlenecks in storage and transportation, resulting in high energy consumption and potential safety risks. Ammonia, as an ideal hydrogen energy carrier, has gradually become a research hotspot: its hydrogen storage density is as high as 17.6 wt%, far exceeding that of high-pressure gaseous hydrogen and liquid hydrogen; it is liquid at room temperature and pressure, and can be stored and transported at low cost using existing chemical storage tanks and transportation pipelines; more importantly, the ammonia synthesis process has undergone a century of development, is technologically mature, and has low cost for large-scale production, providing a solid foundation for the large-scale production of ammonia.

[0003] The ammonia decomposition reaction for hydrogen production is a crucial link between ammonia and hydrogen energy, and its efficiency directly determines the conversion efficiency of the hydrogen energy carrier. This reaction is a strongly endothermic process, and the performance of the catalyst is key to reducing the activation energy and increasing the conversion rate. Currently, ammonia decomposition catalysts are mainly divided into two categories: noble metal-based catalysts represented by ruthenium and non-noble metal-based catalysts represented by iron, cobalt, and nickel. However, ruthenium has a high market price, and global reserves are concentrated in a few regions, limiting its large-scale application. Although iron, cobalt, and nickel cost only one percent or even less than ruthenium, they suffer from insufficient low-temperature activity and easy sintering of metal particles at high temperatures. Therefore, developing catalysts that combine high activity at low temperatures, high-temperature stability, anti-sintering ability, and controllable cost has become crucial to overcoming the technological bottlenecks of ammonia decomposition for hydrogen production.

[0004] Catalyst supports, acting as the supporting framework for active components, directly influence the overall performance of catalysts by regulating the dispersion, electronic state, and interfacial interactions of active metals. However, carbon materials such as graphene and carbon nanotubes, with their abundant surface functional groups like hydroxyl and carboxyl groups, can anchor metal nanoparticles through coordination, but they suffer from poor high-temperature resistance and are prone to carbon deposition, leading to the covering of active sites and ultimately irreversible catalyst deactivation. Traditional oxides, with their low cost, high specific surface area, and acidic or basic properties, have been extensively studied, but their catalytic activity remains relatively low and they are prone to causing active metal agglomeration. Summary of the Invention

[0005] To address the limitations of existing ammonia decomposition hydrogen production technologies, where catalysts are constrained by the support, making it difficult to simultaneously achieve high activity, high-temperature resistance, and low cost, this application provides a preparation technique for a rare-earth silicate-supported ammonia decomposition catalyst. Using rare-earth silicates as the support, which possess unique surface chemical properties, precisely tunable acid-base sites, and excellent chemical stability, this catalyst not only achieves high dispersion of the active components but also significantly enhances the adsorption and activation capacity for ammonia through the construction of strong metal-support interactions. Simultaneously, this strong interaction effectively anchors the active metal, suppressing its sintering phenomenon at high temperatures, fundamentally solving the key bottlenecks in catalyst activity and stability.

[0006] The technical solution adopted in this application is as follows: According to a first aspect of this application, a method for preparing a rare earth silicate-supported ammonia decomposition catalyst is provided, comprising: The rare earth silicate support is impregnated in a solution containing the active component precursor, and then the impregnated rare earth silicate support is dried, calcined, and reduced to obtain the rare earth silicate supported ammonia decomposition catalyst.

[0007] Optionally, the rare earth silicate support is selected from lanthanum silicate (La₂SiO₅, La₂Si₂O₇), cerium silicate (Ce₂SiO₅), praseodymium silicate (Pr₂SiO₅), and neodymium silicate (Nd₂SiO₅, Nd₄Si₃O₇). 12 It includes at least one of the following: samarium silicate (Sm2SiO5), europium silicate (Eu2SiO5), gadolinium silicate (Gd2SiO5, Gd2Si2O7), terbium silicate (Tb2SiO5), dysprosium silicate (Dy2SiO5), holmium silicate (Ho2SiO5, Ho2Si2O7), erbium silicate (Er2SiO5), ytterbium silicate (Yb2SiO5, Yb2Si2O7), lutetium silicate (Lu2SiO5), yttrium silicate (Y2SiO5, Y2Si2O7), and scandium silicate (Sc2SiO5, Sc2Si2O7).

[0008] Optionally, the active component precursor is selected from at least one of ruthenium acetylacetonate, ruthenium carbonyl, potassium ruthenate, sodium ruthenate, ruthenium iodide, ruthenium nitrite, ruthenium acetate, ammonium chlororuthenate, ruthenium chloride, ferric nitrate, ferric chloride, ferric sulfate, cobalt nitrate, cobalt chloride, cobalt carbonate, cobalt sulfate, cobalt acetate, cobalt carbonyl, nickel nitrate, nickel chloride, nickel sulfate, nickel carbonate, nickel acetate, and nickel oxalate.

[0009] Optionally, the solvent in the solution containing the active component precursor is selected from at least one of water, ethanol, acetone, and tetrahydrofuran.

[0010] The concentration of the solution containing the precursor of the active component can be selected or adjusted by those skilled in the art based on the proportion of the active component in the catalyst product.

[0011] Optionally, the ratio of the rare earth silicate support to the solution containing the active component precursor is 1g:1~10mL.

[0012] Optionally, the impregnation conditions include: impregnation at 10~80°C for 0.5~48 h.

[0013] Optionally, the drying conditions include drying at 30~150℃ for 1~48 h.

[0014] Optionally, the calcination conditions include: being carried out in an atmosphere of inert gas, a calcination temperature of 300~1200℃, a calcination time of 1~48 h, and a volume hourly space velocity (VHSV) of 100~10000 mL g. cat 1 h 1 .

[0015] Optionally, the inactive gas may be at least one of nitrogen, argon, and helium.

[0016] Optionally, the reduction conditions include: being carried out in a reducing gas atmosphere, a reduction temperature of 50~850℃, a reduction time of 0.1~24 h, and a volume hourly space velocity (VHSV) of 100~10000 mL g. cat 1 h 1 .

[0017] Optionally, the reducing gas is hydrogen and / or ammonia.

[0018] Optionally, the reducing gas is a mixture of hydrogen and ammonia, wherein the volume percentage of hydrogen is 1% to 100%.

[0019] According to a second aspect of this application, a rare earth silicate-supported ammonia decomposition catalyst prepared by the aforementioned method is provided, the rare earth silicate-supported ammonia decomposition catalyst comprising a support and an active component; The carrier is a rare earth silicate; The active component is at least one of iron, cobalt, nickel, and ruthenium. For example, it can be a single metal, a bimetallic combination, or a multimetallic combination.

[0020] Optionally, the mass content of the active component in the rare earth silicate supported ammonia decomposition catalyst is 0.5~60 wt%. In this application, the mass content of the active component refers to 100% (mass of active metal element / mass of carrier).

[0021] When the active component is ruthenium and other elements, the molar ratio of ruthenium to other elements is 1:10~100, wherein the other elements are at least one of iron, cobalt, and nickel.

[0022] According to a third aspect of this application, a rare earth silicate-supported ammonia decomposition catalyst prepared by the aforementioned method is provided, and the application of at least one of the aforementioned rare earth silicate-supported ammonia decomposition catalysts in catalytic ammonia decomposition is provided, comprising: Ammonia gas or ammonia-containing feed gas is contacted with the rare earth silicate supported ammonia decomposition catalyst to carry out a catalytic reaction to generate hydrogen and nitrogen gas.

[0023] Optionally, the volume concentration of ammonia in the ammonia-containing raw material gas is 0.1% to 100%.

[0024] Optionally, the catalytic reaction is carried out in a fixed-bed reactor or a fluidized-bed reactor.

[0025] Optionally, the conditions for the catalytic reaction include: a reaction pressure of 0.1–10 MPa, a reaction temperature of 300–800 °C, and a space velocity of ammonia or a feed gas containing ammonia of 1,000–100,000 mL g. cat 1 h 1 .

[0026] The beneficial effects of this application include: (1) The catalyst provided in this application can effectively construct a strong metal-support interaction in the catalytic ammonia decomposition reaction, converting ammonia into hydrogen and nitrogen at a relatively low temperature (350~650℃), achieving high-efficiency catalysis in the low-temperature region. This significantly reduces the energy consumption requirement of the reaction and provides possibilities for the application of ammonia decomposition technology in more scenarios (such as small-scale hydrogen production equipment, mobile energy systems, ammonia decomposition tail gas treatment, etc.).

[0027] (2) The catalyst provided in this application has a low price of rare earth silicate support, and the active metal can be a non-precious metal or a low-content precious metal. The preparation adopts an impregnation process, which is simple and short. It does not require complicated equipment, and there is no use or emission of toxic or harmful reagents. It has the potential for large-scale production and is conducive to promoting the industrial application of the catalyst.

[0028] (3) The catalyst provided in this application has excellent high temperature resistance and carbon resistance, which enables the catalyst to maintain a stable structure and catalytic activity during long-term use. Attached Figure Description

[0029] Figure 1 The graph shows the stability test data of the 4% Ru / La2SiO5 catalyst prepared in Example 1 of this application under the reaction condition of 450°C for ammonia decomposition reaction. Detailed Implementation

[0030] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0031] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0032] Unless otherwise specified, all test methods are standard and all instrument settings are those recommended by the manufacturer.

[0033] In the embodiments of this application, ammonia decomposition is carried out in a fixed-bed microreactor using a quartz tube reactor. A temperature-controlled thermocouple is mounted on the outer wall of the quartz tube reactor. The reaction gas components are analyzed online using an Agilent 7890B gas chromatograph equipped with a Porapak N column and a thermal conductivity detector, with H2 as the carrier gas.

[0034] In the embodiments of this application, the ammonia conversion rate during ammonia decomposition is calculated as follows: x = (F in, NH3 - F out, NH3 / F in, NH3 ) ×100% F in, NH3 This represents the inlet flow rate of ammonia gas; F out, NH3 This represents the outlet flow rate of ammonia gas.

[0035] According to one embodiment of this application, a rare earth silicate supported catalyst comprises two parts: a support and an active component. The carrier is a rare earth silicate, and the active components are single metals or bimetallic combinations or multimetallic combinations of iron, cobalt, nickel, and ruthenium.

[0036] In one embodiment, the active component accounts for 0.5% to 60% of the carrier mass; when the active component is ruthenium and other elements, the ratio of Ru to other elements is 1:10 to 1:100.

[0037] In one embodiment, the active component as a percentage of the carrier mass is selected from any value of 0.5%, 1%, 2%, 5%, 7%, 8%, 9%, 10%, 20%, 30%, 40%, 50%, 60% or a range between any two of the above values.

[0038] In one embodiment, the ratio of Ru to other elements is selected from any value among 1:10, 1:20, 1:30, 1:40, 1:50, 1:60, 1:70, 1:80, 1:90, 1:100 or a range between any two of the above points.

[0039] According to one embodiment of this application, the preparation method of the rare earth silicate supported catalyst includes the following steps: (1) First, mix the precursor of the active component with the solvent and stir thoroughly until a homogeneous precursor solution is obtained; (2) Add rare earth silicate support to the above precursor solution, mix evenly, impregnate and dry, and then calcine it in an inactive gas environment to obtain catalyst precursor. (3) The catalyst precursor is activated in a reducing gas atmosphere to finally obtain the catalyst.

[0040] In one embodiment, the rare earth silicate support is selected from lanthanum silicate (La₂SiO₅, La₂Si₂O₇), cerium silicate (Ce₂SiO₅), praseodymium silicate (Pr₂SiO₅), and neodymium silicate (Nd₂SiO₅, Nd₄Si₃O₇). 12 It includes at least one of the following: samarium silicate (Sm2SiO5), europium silicate (Eu2SiO5), gadolinium silicate (Gd2SiO5, Gd2Si2O7), terbium silicate (Tb2SiO5), dysprosium silicate (Dy2SiO5), holmium silicate (Ho2SiO5, Ho2Si2O7), erbium silicate (Er2SiO5), ytterbium silicate (Yb2SiO5, Yb2Si2O7), lutetium silicate (Lu2SiO5), yttrium silicate (Y2SiO5, Y2Si2O7), and scandium silicate (Sc2SiO5, Sc2Si2O7).

[0041] In one embodiment, the active component precursor may be selected from one or more of the following: ruthenium acetylacetonate, ruthenium carbonyl, potassium ruthenate, sodium ruthenate, ruthenium iodide, ruthenium nitrite, ruthenium acetate, ammonium chlororuthenate, ruthenium chloride, ferric nitrate, ferric chloride, ferric sulfate, cobalt nitrate, cobalt chloride, cobalt carbonate, cobalt sulfate, cobalt acetate, cobalt carbonyl, nickel nitrate, nickel chloride, nickel sulfate, nickel carbonate, nickel acetate, and nickel oxalate. In one embodiment, the solvent may be selected from one or more of water, ethanol, acetone, and tetrahydrofuran.

[0042] In one embodiment, the solid-liquid ratio between the rare earth silicate support and the precursor is 1:1 to 1:10.

[0043] In one embodiment, the impregnation is carried out at 10~80°C for 0.5~48 h.

[0044] In one embodiment, the drying is carried out at 30~150°C for 1~48 h.

[0045] In one embodiment, the inactive gas may be one or more of nitrogen, argon, and helium.

[0046] In one embodiment, the volume hourly space velocity of the inactive gas is in the range of 100 to 10000 mL g. cat 1 h 1 .

[0047] In one embodiment, the calcination is carried out at 300~1200°C for 1~48 h.

[0048] In one embodiment, the roasting temperature is any value among 300°C, 330°C, 410°C, 490°C, 550°C, 650°C, 900°C, and 1200°C, or a range between any two of the above.

[0049] In one embodiment, the reducing gas may be hydrogen, ammonia, or a mixture of hydrogen or ammonia. If it is a mixture of gases, the volume percentage of hydrogen or ammonia is 1% to 100%.

[0050] In one embodiment, the volume hourly space velocity (VHSV) of the reducing gas is in the range of 100 to 10000 mL g. cat 1 h 1 .

[0051] In one embodiment, the activation is carried out at 50~850°C for 0.1~24 h.

[0052] In one embodiment, the activation temperature is any value among 50°C, 200°C, 300°C, 450°C, 620°C, 730°C, and 850°C, or a range between any two of the above.

[0053] According to one embodiment of this application, the aforementioned rare earth silicate supported catalyst is applied to an ammonia decomposition reaction, comprising: contacting ammonia gas or a feed gas containing ammonia with the rare earth silicate supported catalyst to generate hydrogen and nitrogen gas through the reaction.

[0054] In one embodiment, the reaction conditions are as follows: ammonia gas with a concentration of 0.1% to 100% is introduced into a fixed-bed reactor or a fluidized-bed reactor containing a rare-earth silicate supported catalyst; the reaction pressure is 0.1 to 10 MPa; the reaction temperature is 300 to 800 °C; and the space velocity of the feed gas is 1000 to 100000 mL g. cat 1 h 1 This yields hydrogen and nitrogen gas.

[0055] Example 1 Weigh 0.11 g of ruthenium chloride trihydrate and dissolve it in 2 mL of water. Then add 1.00 g of lanthanum silicate to the ruthenium chloride aqueous solution and impregnate at 26 °C for 8 hours. After drying the product at 100 °C for 10 hours, it is then subjected to a nitrogen gas flow (3000 mL g) cat 1 h 1 The temperature was raised to 500℃ and calcined for 3 hours to obtain the catalyst precursor. The catalyst precursor was then subjected to a 10% H2 / Ar mixed gas (3000 mL g) cat 1 h 1 The catalyst was reduced at 550℃ for 3 hours to obtain 4% Ru / La2SiO5 lanthanum silicate supported on ruthenium catalyst, labeled as 1#.

[0056] Example 2 Weigh 0.51 g of nickel nitrate hexahydrate and dissolve it in 2 mL of acetone. Then add 1.00 g of cerium silicate to the nickel nitrate acetone solution and impregnate at 25°C for 6 hours. After drying the product at 80°C for 40 hours, it is then subjected to an argon gas flow (1000 mL g / L). cat 1 h 1 The temperature was raised to 620℃ and calcined for 2 hours to obtain the catalyst precursor. The catalyst precursor was then subjected to a 20% H2 / N2 mixture (5000 mL g / L) for further calcination. cat 1 h 1 The catalyst was reduced at 680℃ for 2 hours to obtain 10% Ni / Ce2SiO5 cerium silicate supported nickel catalyst, labeled as 2#.

[0057] Example 3 Weigh 1.00 g of cobalt nitrate hexahydrate and dissolve it in 4 mL of acetone. Then add 1.00 g of praseodymium silicate to the cobalt nitrate acetone solution and impregnate at 15°C for 48 hours. After drying the product at 140°C for 2 hours, it is then subjected to a helium gas flow (100 mL g / L). cat 1 h 1 The temperature was raised to 1000℃ and calcined for 1 hour to obtain the catalyst precursor. The catalyst precursor was then subjected to a 60% H2 / N2 mixture (300 mL g) of gas. cat 1 h 1 The cobalt silicate catalyst 20% Co / Pr2SiO5 was obtained by reducing it at 760℃ for 1 hour, and it was labeled as 3#.

[0058] Example 4 Weigh 0.20 g of ruthenium acetylacetonate and dissolve it in 6 mL of water. Then add 1.00 g of neodymium silicate to the ruthenium acetylacetonate aqueous solution and impregnate at 70°C for 0.8 hours. After drying the product at 90°C for 11 hours, it is then subjected to an argon gas flow (10000 mL g / L). cat 1 h 1 The temperature was raised to 375℃ and calcined for 8 hours to obtain the catalyst precursor. The catalyst precursor was then subjected to a 50% NH3 / N2 mixture (5000 mL g / L) for further calcination. cat 1 h 1 The ruthenium silicate supported catalyst 5% Ru / Nd2SiO5 was obtained by reduction at 500℃ for 5 hours, and labeled as 4#.

[0059] Example 5 Weigh 0.11 g of ruthenium carbonyl and dissolve it in 1 mL of water. Then add 1.00 g of samarium silicate to the ruthenium carbonyl acetone solution and impregnate at 20 °C for 20 hours. After drying the product at 70 °C for 28 hours, it is then subjected to an argon gas flow (10000 mL g / L). cat 1 h 1 The temperature was raised to 300℃ and calcined for 45 hours to obtain the catalyst precursor. The catalyst precursor was then subjected to pure H2 gas (200 mL g / L) for further calcination. cat 1 h 1The ruthenium silicate catalyst 5% Ru / Sm2SiO5 was obtained by reducing it at 150℃ for 1 hour, and labeled as 5#.

[0060] Example 6 Weigh 0.87 g of cobalt carbonyl and dissolve it in 7 mL of tetrahydrofuran. Then add 1.00 g of europium silicate to the cobalt carbonyl tetrahydrofuran solution and impregnate at 50 °C for 5 hours. After drying the product at 60 °C for 33 hours, it is then subjected to an argon gas flow (900 mL g) cat 1 h 1 The temperature was raised to 800℃ and calcined for 2 hours to obtain the catalyst precursor. The catalyst precursor was then subjected to a 25% NH3 / N2 mixed gas (500 mL g) cat 1 h 1 The cobalt silicate catalyst 30% Co / Eu2SiO5 was obtained by reducing it at 650℃ for 3 hours, and was labeled as 6#.

[0061] Example 7 Weigh 2.42 g of nickel chloride hexahydrate and dissolve it in 10 mL of water. Then add 1.00 g of yttrium silicate to the nickel chloride aqueous solution and impregnate at 35°C for 12 hours. After drying the product at 88°C for 30 hours, it is then subjected to an argon flow (8000 mL g / L). cat 1 h 1 The temperature was raised to 750℃ and calcined for 2 hours to obtain the catalyst precursor. The catalyst precursor was then subjected to a 35% H2 / N2 mixture (6000 mL g) of gas. cat 1 h 1 The catalyst was reduced at 500℃ for 5 hours to obtain 60% Ni / Y2SiO5 yttrium silicate supported on nickel, labeled as 7#.

[0062] Comparative Example 1 Weigh 0.14 g of ruthenium chloride trihydrate and dissolve it in 2 mL of water. Then add 1.00 g of silicon dioxide to the ruthenium chloride aqueous solution and impregnate at 26 °C for 8 hours. After drying the product at 100 °C for 10 hours, it is then subjected to a nitrogen gas flow (3000 mL g) cat 1 h 1The temperature was raised to 500℃ and calcined for 3 hours to obtain the catalyst precursor. The catalyst precursor was then subjected to a 10% H2 / Ar mixed gas (3000 mL g) cat 1 h 1 The ruthenium oxide catalyst (5% Ru / SiO2) was obtained by reducing it at 550℃ for 3 hours and labeled as 8#.

[0063] Comparative Example 2 Weigh 0.14 g of ruthenium chloride trihydrate and dissolve it in 2 mL of water. Then add 1.00 g of lanthanum oxide to the ruthenium chloride aqueous solution and impregnate at 26 °C for 8 hours. After drying the product at 100 °C for 10 hours, it is then subjected to a nitrogen atmosphere (3000 mL g / L) for further processing. cat 1 h 1 The temperature was raised to 500℃ and calcined for 3 hours to obtain the catalyst precursor. The catalyst precursor was then subjected to a 10% H2 / Ar mixed gas (3000 mL g) cat 1 h 1 The catalyst was reduced at 550℃ for 3 hours to obtain lanthanum oxide supported on ruthenium (5% Ru / La2O3), labeled as 9#.

[0064] Comparative Example 3 Weigh 0.51 g of nickel nitrate hexahydrate and dissolve it in 2 mL of acetone. Then add 1.00 g of silicon dioxide to the nickel nitrate acetone solution and impregnate at 25°C for 6 hours. After drying the product at 80°C for 40 hours, it is then subjected to an argon gas flow (1000 mL g / mL). cat 1 h 1 The temperature was raised to 620℃ and calcined for 2 hours to obtain the catalyst precursor. The catalyst precursor was then subjected to a 20% H2 / N2 mixture (5000 mL g / L) for further calcination. cat 1 h 1 The silicon oxide nickel-supported catalyst (10% Ni / SiO2) was obtained by reduction at 680℃ for 2 hours and labeled as 9#.

[0065] Comparative Example 4 Weigh 1.00 g of cobalt nitrate hexahydrate and dissolve it in 2 mL of acetone. Then add 1.00 g of yttrium oxide to the cobalt nitrate acetone solution and impregnate at 25°C for 6 hours. After drying the product at 80°C for 40 hours, it is then subjected to an argon gas flow (1000 mL g / L). cat 1 h 1 The temperature was raised to 620℃ and calcined for 2 hours to obtain the catalyst precursor. The catalyst precursor was then subjected to a 20% H2 / N2 mixture (5000 mL g / L) for further calcination. cat 1 h 1 The yttrium oxide-supported cobalt catalyst (20% Co / Y2O3) was obtained by reduction at 680℃ for 2 hours and labeled as 10#.

[0066] Application Example 8: Ammonia Decomposition Catalytic Performance and Stability Test In an ammonia decomposition apparatus, an evaluation experiment was conducted on the stability of the ammonia decomposition reaction using the lanthanum silicate-supported ruthenium catalyst prepared in Example 1. A fixed-bed reactor with an inner diameter of 6 mm was used, and 0.10 g of catalyst was loaded. Reaction conditions: pure ammonia gas was used as the raw material, and the reaction space velocity was controlled at 30,000 mL g / L. cat -1 h -1 The test was conducted continuously at 450℃ for 100 hours, and the relevant results are as follows: Figure 1 As shown in Table 1, the lanthanum silicate-supported ruthenium catalyst prepared in this application exhibits excellent stability. During the 100-hour ammonia decomposition reaction, its catalytic activity remained basically stable without significant decrease.

[0067] The catalysts prepared in other embodiments of this application are tested using the same stability test method as described above. The reaction conditions and test results are shown in Table 1. The test results show that these catalysts also have good catalytic stability and have good application prospects.

[0068]

[0069] As can be clearly seen from the data in Table 1, the ammonia decomposition catalyst prepared in this application exhibits excellent ammonia decomposition catalytic performance. Compared with Comparative Examples 1 and 2, the ruthenium-based ammonia decomposition catalyst of this application shows significantly better catalytic activity than traditional ruthenium-based catalysts supported on silicon oxide or rare earth oxide lanthanum oxide. Compared with Comparative Examples 3 and 4, the nickel-based and cobalt-based ammonia decomposition catalysts of this application also show significantly higher catalytic activity than traditional nickel-based and cobalt-based catalysts supported on silicon oxide or rare earth oxide yttrium oxide.

[0070] Unless otherwise specified, all figures appearing in this application specification and claims, such as active components, temperature and time, conversion rates, etc., should not be construed as absolutely precise values. They can be obtained by rounding as needed, and due to the standard deviation of measurement techniques, the measured values ​​inevitably contain a certain amount of experimental error.

[0071] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing a rare earth silicate-supported ammonia decomposition catalyst, characterized in that, include: The rare earth silicate support is impregnated in a solution containing the active component precursor, and then the impregnated rare earth silicate support is dried, calcined, and reduced to obtain the rare earth silicate supported ammonia decomposition catalyst.

2. The preparation method according to claim 1, characterized in that, The rare earth silicate support is selected from at least one of lanthanum silicate, cerium silicate, praseodymium silicate, neodymium silicate, samarium silicate, europium silicate, gadolinium silicate, terbium silicate, dysprosium silicate, holmium silicate, erbium silicate, ytterbium silicate, lutetium silicate, yttrium silicate, and scandium silicate.

3. The preparation method according to claim 1, characterized in that, The active component precursor is selected from at least one of the following: ruthenium acetylacetonate, ruthenium carbonyl, potassium ruthenate, sodium ruthenate, ruthenium iodide, ruthenium nitrite, ruthenium acetate, ammonium chlororuthenate, ruthenium chloride, ferric nitrate, ferric chloride, ferric sulfate, cobalt nitrate, cobalt chloride, cobalt carbonate, cobalt sulfate, cobalt acetate, cobalt carbonyl, nickel nitrate, nickel chloride, nickel sulfate, nickel carbonate, nickel acetate, and nickel oxalate. Preferably, the solvent in the solution containing the active component precursor is selected from at least one of water, ethanol, acetone, and tetrahydrofuran.

4. The preparation method according to claim 1, characterized in that, The ratio of the rare earth silicate support to the solution containing the active component precursor is 1g:1~10mL; Preferably, the impregnation conditions include: impregnation at 10~80℃ for 0.5~48 h; Preferably, the drying conditions include drying at 30~150℃ for 1~48 h.

5. The preparation method according to claim 1, characterized in that, The calcination conditions include: calcination is carried out in an atmosphere of inert gas, the calcination temperature is 300–1200 °C, the calcination time is 1–48 h, and the volume hourly space velocity (VHSV) of the inert gas is 100–10000 mL g. cat 1 h 1 .

6. The preparation method according to claim 1, characterized in that, The reduction conditions include: being carried out in a reducing gas atmosphere, a reduction temperature of 50–850°C, a reduction time of 0.1–24 h, and a volume hourly space velocity (VHSV) of 100–10000 mL g / L. cat 1 h 1 ; Preferably, the reducing gas is hydrogen and / or ammonia.

7. The rare earth silicate-supported ammonia decomposition catalyst obtained by the preparation method according to any one of claims 1 to 6, characterized in that, The rare earth silicate supported ammonia decomposition catalyst includes a support and an active component; The carrier is a rare earth silicate; The active component is at least one of iron, cobalt, nickel, and ruthenium.

8. The rare earth silicate-supported ammonia decomposition catalyst according to claim 7, characterized in that, The mass content of the active component in the rare earth silicate supported ammonia decomposition catalyst is 0.5~60 wt%. When the active component is ruthenium and other elements, the molar ratio of ruthenium to other elements is 1:10~100, wherein the other elements are at least one of iron, cobalt, and nickel.

9. The application of at least one of the rare earth silicate-supported ammonia decomposition catalysts obtained by the preparation method according to any one of claims 1 to 6, and the rare earth silicate-supported ammonia decomposition catalysts according to claim 7 or 8, in catalytic ammonia decomposition, characterized in that, include: Ammonia gas or ammonia-containing feed gas is contacted with the rare earth silicate supported ammonia decomposition catalyst to carry out a catalytic reaction to generate hydrogen and nitrogen gas.

10. The application according to claim 9, characterized in that, The volume concentration of ammonia in the raw material gas containing ammonia is 0.1% to 100%. Preferably, the catalytic reaction is carried out in a fixed-bed reactor or a fluidized-bed reactor; Preferably, the conditions for the catalytic reaction include: a reaction pressure of 0.1~10 MPa, a reaction temperature of 300~800℃, and a space velocity of ammonia or a feed gas containing ammonia of 1000~100000 mL g. cat 1 h 1 .

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