Preparation method and application of low-temperature high-efficiency ammonia decomposition hydrogen production catalyst

Abstract

The application discloses a preparation method and application of a low-temperature high-efficiency ammonia decomposition hydrogen production catalyst and belongs to the technical field of ammonia decomposition hydrogen production catalysts. The preparation method of the low-temperature high-efficiency ammonia decomposition hydrogen production catalyst comprises the following steps: taking a perovskite oxide, an assistant source and CaH2 as raw materials, and preparing a multi-metal oxynitride carrier through a solid-phase synthesis method and a nitriding treatment; mixing the multi-metal oxynitride carrier, a cobalt-containing compound and a solvent, and drying to obtain a mixed powder; and performing heat annealing treatment on the mixed powder after tabletting to obtain the low-temperature high-efficiency ammonia decomposition hydrogen production catalyst. The ammonia decomposition hydrogen production catalyst has the advantages of low ammonia decomposition working temperature, high decomposition rate, simple preparation process, low manufacturing cost and suitability for industrial use.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ammonia decomposition hydrogen production catalyst, in particular to a preparation method and application of a low-temperature and high-efficiency ammonia decomposition hydrogen production catalyst. BACKGROUND

[0002] As a clean energy, hydrogen energy has the characteristics of zero carbon emission (only water is generated by combustion), in addition, the mass energy density of hydrogen is 120-142 MJ / kg, which is 3 times of gasoline and 150 times of lithium ion battery, and it is particularly suitable for long endurance scenarios such as aviation and heavy transport, which can greatly reduce the dependence on fossil energy. Hydrogen energy can be used as a large-scale cross-season energy storage medium to solve the intermittency problem of wind and photovoltaic energy. Therefore, large-scale economic production, safe and efficient transportation, and convenient and efficient utilization are important factors restricting the development of hydrogen.

[0003] Ammonia as a hydrogen carrier has developed rapidly in recent years, and its application in the energy field has gradually been valued. On the one hand, ammonia has a high hydrogen content, and the hydrogen content per unit mass of ammonia is higher than that of many traditional hydrogen storage materials, and the energy density of liquid ammonia is large, which is convenient for storage and transportation; on the other hand, the liquefaction temperature of ammonia is relatively easy to achieve compared with hydrogen, which is about -33℃ at normal pressure, and the infrastructure requirements for storage and transportation are relatively low. In addition, ammonia can be prepared by various methods, such as the traditional Haber process and the electrolysis of water to produce hydrogen and then synthesis of ammonia with nitrogen.

[0004] The ammonia decomposition hydrogen production technology is mainly a process of decomposing ammonia into nitrogen and hydrogen through the action of a catalyst. The commonly used catalysts are mainly noble metals represented by ruthenium and platinum and non-noble metals represented by cobalt and iron as active materials. The use temperature of ruthenium-based catalyst is lower, and it can achieve a high ammonia decomposition rate at about 600℃, which is a relatively excellent low-temperature ammonia decomposition hydrogen production catalyst at present. However, the price of ruthenium-based catalyst is high, and the preparation cost is large, which greatly limits its large-scale application. Non-noble metal catalysts are simple to synthesize and low in price, and are a kind of catalyst commonly used in industrial production at present. However, its use temperature is high (above 700℃), the energy consumption is high, and the requirement for equipment is high. Therefore, it is of great significance to develop a low-temperature and high-efficiency ammonia decomposition hydrogen production catalyst for the development of hydrogen energy. SUMMARY

[0005] The purpose of the present application is to provide a preparation method and application of a low-temperature and high-efficiency ammonia decomposition hydrogen production catalyst to solve the problems existing in the prior art.

[0006] To achieve the above-mentioned purpose, the present application provides the following solutions:

[0007] One of the technical solutions of the present application: a preparation method of a low-temperature and high-efficiency ammonia decomposition hydrogen production catalyst, comprising the following steps:

[0008] A multi-metal nitride support was prepared by solid-state synthesis and nitriding treatment using perovskite oxide, an auxiliary source, and CaH2 as raw materials. The multi-metal nitride support, a cobalt-containing compound, and a solvent were mixed and dried to obtain a mixed powder. The mixed powder was then pressed into tablets and subjected to thermal annealing to obtain the low-temperature high-efficiency ammonia decomposition hydrogen production catalyst.

[0009] The auxiliary agent source includes one or more of CeO2 and potassium acetate.

[0010] Using perovskite oxides, promoter sources (one or more of CeO2 and potassium acetate), and CaH2 as raw materials, a multi-metal nitride support (i.e., nitrogen-doped perovskite oxides loaded with CeO2 and / or K2O3) can be obtained through solid-phase synthesis and nitriding treatment. The multi-metal nitride support, cobalt-containing compound, and solvent are mixed, dried to obtain a mixed powder, and then subjected to thermal annealing to introduce cobalt (Co) in the form of a metal oxide into the multi-metal nitride support. Therefore, the low-temperature, high-efficiency ammonia decomposition hydrogen production catalyst prepared by the method of this invention is a non-noble metal-based ammonia decomposition hydrogen production catalyst with transition metal cobalt (existing in the catalyst as Co3O4) as the core, using a nitrogen-doped perovskite oxide supported with promoters (CeO2 and / or K2O3, formed by the promoter source) as the support (referred to as a multi-metal nitride support), wherein nitrogen doping (N... 3- Replace O 2- This leads to lattice distortion, forming highly active nitrogen vacancies. These vacancies can capture lone pairs of electrons from NH3, promoting NH bond breaking and accelerating N2 desorption. Furthermore, N doping allows the Fermi level to enter the conduction band, enhancing electron conductivity and accelerating electron transfer between the metal and reactants. During the reduction process before the ammonia decomposition to hydrogen production, perovskite nitrides precipitate ultrafine active metal Co particles in situ, enhancing the catalytic effect of the active particles. The strong electronegativity of N in the support draws electrons from the d-band of the active metal, forming electron-deficient metal sites and enhancing the affinity for N atoms in NH3. The CeO2 / K2O3 promoter provides Ce... 2+ / K + Electrons are injected into the conduction band of the carrier, increasing the electron density of the metal and thus promoting N2 desorption. The active metal Co, perovskite-type nitrides, and the auxiliaries CeO2 / K2O3 provide Ce. 2+ / K + The synergistic effect between these components can effectively improve the catalytic performance of the catalyst. This catalyst is suitable for efficient low-temperature (400-550℃) decomposition of ammonia to hydrogen, and has the advantages of high stability and low cost, making it a viable alternative to precious metal catalysts (such as Ru-based catalysts).

[0011] Furthermore, the perovskite oxide includes CaTiO3, SrTiO3, BaTiO3 or PbTiO3, preferably BaTiO3.

[0012] Furthermore, the molar ratio of CaH2 to the perovskite oxide is 1:3-3.3.

[0013] Optionally, the auxiliary agent source is CeO2. The steps of preparing the multi-metal nitride support by solid-state synthesis and nitriding treatment include: mixing perovskite oxide, CeO2 and CaH2, pressing into tablets and then subjecting them to calcination and nitriding treatment in sequence to obtain the multi-metal nitride support (i.e., nitrogen-doped perovskite oxide loaded with CeO2).

[0014] The above scheme first uses solid-state synthesis to prepare hydrogen-doped perovskite oxides with added additives as precursors, and then nitrides them in a nitrogen atmosphere to introduce nitrogen into the metal lattice to form a multi-metal oxynitride support (i.e. perovskite oxynitrides with added additives).

[0015] Optionally, the auxiliary agent source is potassium acetate. The steps of preparing the multi-metal nitride support by solid-phase synthesis and nitriding treatment include: mixing perovskite oxide and CaH2, pressing into tablets, and then subjecting them to calcination and nitriding treatment in sequence; mixing the nitriding product (i.e., the nitriding product) with potassium acetate solution, drying, and high-temperature annealing treatment to obtain the multi-metal nitride support (i.e., nitrogen-doped perovskite oxide loaded with K2O3).

[0016] Optionally, the auxiliary agent source is CeO2 and potassium acetate. The steps of preparing the multi-metal nitride support by solid-state synthesis and nitriding treatment include: mixing perovskite oxide, CeO2 and CaH2, pressing into tablets and then subjecting them to calcination and nitriding treatment in sequence; mixing the nitriding product with potassium acetate solution, drying, and high-temperature annealing treatment to obtain the multi-metal nitride support (i.e., nitrogen-doped perovskite oxide loaded with CeO2 and K2O3).

[0017] Furthermore, when the auxiliary agent source is CeO2, the mass ratio of CeO2 to the perovskite oxide is 1:10-20;

[0018] When the auxiliary agent source is potassium acetate, the mass ratio of the product of the nitridation treatment to the potassium acetate contained in the potassium acetate solution is 1:0.125-0.375;

[0019] When the auxiliary agent source is CeO2 and potassium acetate, the mass ratio of CeO2 to the perovskite oxide is 1:10-20, and the mass ratio of the nitriding product to the potassium acetate contained in the potassium acetate solution is 1:0.125-0.375.

[0020] Optionally, the CeO2 loading in the polymetallic nitride support is 0 or 5-10 wt%, and the K2O3 loading is 0 or 2-5 wt%.

[0021] CeO2 loading = mass of CeO2 in the polymetallic nitride support / mass of nitrogen-doped perovskite oxide in the polymetallic nitride support × 100%.

[0022] K2O3 loading = mass of K2O3 in the polymetallic nitride support / mass of nitrogen-doped perovskite oxide in the polymetallic nitride support × 100%.

[0023] Furthermore, in the step of preparing the multi-metal nitride support by solid-phase synthesis and nitriding treatment, the tableting is carried out in an inert gas, the tableting pressure is 5-10 MPa, and the diameter of the formed tablet is 10-20 mm.

[0024] Furthermore, the calcination treatment is carried out at a temperature of 560-600℃ for a time of 24-168h.

[0025] Furthermore, the calcination treatment is performed at 10... -2 -10 -4 The procedure was carried out under a vacuum of Pa.

[0026] Furthermore, the heating rate of the calcination treatment is 5-10℃ / min.

[0027] Furthermore, the step prior to the nitriding treatment includes cleaning and removing impurities from the calcined product using a methanol-water solution.

[0028] Furthermore, the methanol-water solution is prepared by mixing methanol and water in a volume ratio of 9:1 to 5:5.

[0029] Furthermore, the specific operation of the nitriding treatment is as follows: nitriding treatment at 300-600℃ for 6-10 hours at a nitrogen flow rate of 50-100 mL / min.

[0030] Furthermore, the heating rate of the nitriding treatment is 5-10 °C / min.

[0031] Furthermore, in the step of preparing the polymetallic nitride support by solid-state synthesis and nitriding treatment, the high-temperature annealing treatment is carried out at a temperature of 300-500℃ for 3-6 hours, and the heating rate is 5-10℃ / min.

[0032] The high-temperature annealing treatment is at 10 -2 -10 -4 The procedure was carried out under a vacuum of Pa.

[0033] Furthermore, the solvent includes methanol.

[0034] Furthermore, the cobalt-containing compound is cobalt(III) acetylacetonate.

[0035] Furthermore, the ratio of the mass of cobalt in the cobalt acetylacetonate (III) to the sum of the mass of Co3O4 that can be converted from the cobalt in the cobalt acetylacetonate (III) and the mass of the polymetallic nitride support is 0.05-0.25:1. That is, the mass of Co in the cobalt acetylacetonate (III) : (mass of Co3O4 that can be converted from the Co in the cobalt acetylacetonate (III) + mass of the polymetallic nitride support) = 0.05-0.25:1.

[0036] Furthermore, the ratio of cobalt(III) acetylacetonate to the solvent is 0.76-1.52 g: 60-118 mL.

[0037] Furthermore, the temperature of the heat annealing treatment is 200-360℃, the time is 3-6h, and the heating rate is 5-10℃ / min;

[0038] The heat annealing treatment is at 10 -2 -10 -4 The procedure was carried out under a vacuum of Pa.

[0039] The process of compressing the mixed powder into tablets includes: the tableting is carried out in air, the pressure of the tableting is 5-10 MPa, and the diameter of the formed tablet is 10-20 mm.

[0040] In the preparation of the polymetallic nitride support, the process involves tableting followed by calcination and nitriding, and mixing and drying the polymetallic nitride support, cobalt-containing compound, and solvent to obtain a mixed powder, followed by tableting and then thermal annealing (to load Co onto the polymetallic nitride support). This process transforms the particle contact from point contact to surface contact, increasing the reaction contact area and facilitating atomic migration. Furthermore, the close contact reduces the interfacial barrier, lowers the ion diffusion activation energy, accelerates ion migration, and promotes the reaction. Moreover, the catalyst prepared by tableting accelerates the separation of NH4+ and the formation of N2N and H2H in the subsequent ammonia decomposition hydrogen production catalytic reaction, promoting the reaction and improving reaction efficiency.

[0041] The second technical solution of the present invention: a low-temperature high-efficiency ammonia decomposition hydrogen production catalyst prepared according to the above-mentioned preparation method of the low-temperature high-efficiency ammonia decomposition hydrogen production catalyst.

[0042] Optionally, the Co content in the low-temperature high-efficiency ammonia decomposition hydrogen production catalyst is 5-25 wt%.

[0043] The Co content = the mass of Co in the final catalyst / the mass of the final catalyst × 100%.

[0044] The third technical solution of the present invention: the application of the above-mentioned low-temperature high-efficiency ammonia decomposition hydrogen production catalyst in the ammonia decomposition hydrogen production reaction.

[0045] Furthermore, the steps of the ammonia decomposition hydrogen production reaction include: first reducing the low-temperature high-efficiency ammonia decomposition hydrogen production catalyst in a reducing gas atmosphere, and then carrying out the ammonia decomposition hydrogen production reaction in an ammonia atmosphere.

[0046] Furthermore, the reducing gas is a nitrogen-hydrogen mixture (25 vol% nitrogen + 75 vol% hydrogen), the flow rate of the reducing gas is 20-100 mL / min, the reduction temperature is 400-600℃, and the time is 2-8 h.

[0047] Before the ammonia decomposition reaction, hydrogen is used to reduce the low-temperature high-efficiency ammonia decomposition hydrogen production catalyst, so that Co3O4 in the catalyst is converted into elemental Co (CeO2 and K2O3 have reduction temperatures above 1000℃ and will not be reduced to elemental form by hydrogen during the reduction process), which can improve its catalytic performance.

[0048] Furthermore, the space velocity of the ammonia decomposition to hydrogen production reaction is 9000-12000 h⁻¹. -1 .

[0049] This invention improves the performance of an ammonia decomposition hydrogen production catalyst by altering the support and the loading of active materials. Compared to commercially available catalysts, the ammonia decomposition hydrogen production catalyst of this invention has advantages such as lower ammonia decomposition operating temperature, higher decomposition rate, longer catalyst life, stable structure, simple preparation process, low manufacturing cost, and suitability for industrial use.

[0050] The present invention discloses the following technical effects:

[0051] (1) The low-temperature high-efficiency ammonia decomposition hydrogen production catalyst of the present invention has a lower ammonia decomposition temperature than the cobalt-based catalyst currently used in industry, and the low-temperature ammonia decomposition efficiency is higher.

[0052] (2) The preparation method of the present invention has a simple preparation process, the raw materials are cheap and readily available, and the manufacturing cost is low. Attached Figure Description

[0053] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0054] Figure 1 The images show photographs of the precursor powder (a) obtained in step (1) of Example 1, the multi-metal nitride support (b) obtained in step (2), and the ammonia decomposition hydrogen production catalyst (c) obtained in step (3).

[0055] Figure 2 The XRD patterns are those of the precursor powder (a) obtained in step (1) of Example 1, the multi-metal nitride support (b) obtained in step (2), and the ammonia decomposition hydrogen production catalyst (c) obtained in step (3).

[0056] Figure 3 XPS spectra of the precursor powder (a) obtained in step (1) of Example 1 and the multi-metal nitride support (b) obtained in step (2). Detailed Implementation

[0057] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0058] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0059] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0060] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0061] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0062] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0063] As a first aspect of the present invention, the present invention provides a method for preparing a low-temperature, high-efficiency ammonia decomposition hydrogen production catalyst, comprising the following steps:

[0064] A multi-metal nitride support was prepared by solid-state synthesis and nitriding treatment using perovskite oxide, an auxiliary source, and CaH2 as raw materials. The multi-metal nitride support, a cobalt-containing compound, and a solvent were mixed and dried to obtain a mixed powder. The mixed powder was then pressed into tablets and subjected to thermal annealing to obtain the low-temperature high-efficiency ammonia decomposition hydrogen production catalyst.

[0065] In a preferred embodiment of the present invention, the preparation method includes the following more specific steps:

[0066] (1) The preparation of precursors can be divided into the following two methods depending on the source of the auxiliary agent:

[0067] Method 1 (auxiliary source is CeO2 or CeO2 + potassium acetate): First, mix CeO2 powder and perovskite oxide powder using ball milling, then add CaH2 powder for grinding, and compress the mixture into tablets in an inert gas atmosphere. Finally, place the tableted sample into a vacuum furnace and calcine it at 560-600℃ for 24-168h at a rate of 5-10℃ / min to obtain the precursor powder (i.e., hydrogen-doped perovskite oxide loaded with CeO2).

[0068] Method 2 (potassium acetate as the auxiliary agent): The perovskite oxide powder and CaH powder are mixed and ground, and then pressed into tablets in an inert gas atmosphere. Finally, the tableted sample is placed in a vacuum furnace and calcined at 560-600℃ for 24-168h at a rate of 5-10℃ / min to obtain the precursor powder (i.e., hydrogen-doped perovskite oxide).

[0069] (2) The preparation of polymetallic nitride supports can be divided into the following two methods depending on the source of the auxiliary agent:

[0070] Method 1 (CeO2 as the auxiliary source): The precursor powder (i.e., hydrogen-doped perovskite oxide loaded with CeO2) is placed in a vacuum tube furnace. First, the air in the furnace tube is evacuated using a vacuum pump, and then nitrogen gas is continuously introduced at a rate of 50-100 mL / min for atmosphere filling. The temperature control program is adjusted to raise the furnace tube temperature to 300-600℃ at a rate of 5-10℃ / min, and maintained for 6-10 hours. The temperature is then allowed to cool naturally to room temperature to obtain a multi-metal nitride support (i.e., nitrogen-doped perovskite oxide loaded with CeO2).

[0071] Method 2 (auxiliary source is potassium acetate or CeO2 + potassium acetate): The precursor powder (hydrogen-doped perovskite oxide or hydrogen-doped perovskite oxide loaded with CeO2) is placed in a vacuum tube furnace. First, the air in the furnace tube is extracted using a vacuum pump, and then nitrogen gas is continuously introduced at a rate of 50-100 mL / min for atmosphere filling. The temperature control program is adjusted to raise the furnace tube temperature to 300-600℃ at a rate of 5-10℃ / min, and maintained for 6-10 hours. The temperature is then allowed to cool naturally to room temperature to obtain the nitrided product (nitrogen-doped perovskite oxide or nitrogen-doped perovskite oxide loaded with CeO2). Potassium acetate was dissolved in an aqueous methanol solution, and then nitrogen-doped perovskite oxide or nitrogen-doped perovskite oxide loaded with CeO2 was added. After magnetic stirring for 2-4 hours, the mixed sample was evaporated to dryness using a rotary evaporator. Then, it was placed in a vacuum tube furnace and heated to 300-500℃ at a rate of 5-10℃ / min, held at that temperature for 3-6 hours, and then naturally cooled to room temperature to obtain a multi-metal nitride support (i.e., nitrogen-doped perovskite oxide loaded with K2O3 or nitrogen-doped perovskite oxide loaded with CeO2 and K2O3).

[0072] (3) Preparation of low-temperature high-efficiency ammonia decomposition hydrogen production catalyst: The polymetallic nitrogen oxide support was dissolved in methanol, and cobalt(III) acetylacetone was added. After magnetic stirring for 4-24 h, the mixed sample was evaporated to dryness using a rotary evaporator. The evaporated powder was taken out and pressed into tablets. The tableted sample was then placed in a vacuum tube furnace and heated to 200-360 °C at a rate of 5-10 °C / min, held at that temperature for 3-6 h, and then naturally cooled to room temperature. The annealed sample was taken out and ground to obtain the low-temperature high-efficiency ammonia decomposition hydrogen production catalyst (i.e., polymetallic nitrogen oxide supported on cobalt (specifically Co3O4)).

[0073] As a second aspect of the present invention, the present invention provides a low-temperature high-efficiency ammonia decomposition hydrogen production catalyst prepared according to the above-described method for preparing a low-temperature high-efficiency ammonia decomposition hydrogen production catalyst.

[0074] As a third aspect of the present invention, the present invention provides the application of the above-mentioned low-temperature high-efficiency ammonia decomposition hydrogen production catalyst in the ammonia decomposition hydrogen production reaction.

[0075] As an embodiment of the present invention, the steps of the ammonia decomposition hydrogen production reaction include: first reducing the low-temperature high-efficiency ammonia decomposition hydrogen production catalyst in a reducing gas atmosphere, and then carrying out the ammonia decomposition hydrogen production reaction in an ammonia atmosphere.

[0076] As a preferred embodiment of the present invention, the more specific steps of the ammonia decomposition to hydrogen production reaction include: under normal pressure, first introducing a nitrogen-hydrogen mixed gas (25 vol% nitrogen + 75 vol% hydrogen) at a flow rate of 20-100 mL / min as a reducing gas to reduce the low-temperature high-efficiency ammonia decomposition to hydrogen production catalyst at a reduction temperature of 400-600℃ for 2-8 h, and then introducing ammonia gas as a reactant at a reduction temperature of 9000-12000 h. -1 The space velocity is used to carry out the ammonia decomposition to produce hydrogen at a temperature of 400-550℃.

[0077] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0078] In specific embodiments of the present invention, room temperature refers to 25±5℃.

[0079] Unless otherwise specified, all raw materials used in the specific embodiments of this invention are commercially available products.

[0080] In the specific embodiments of the present invention, the loading amount and content refer specifically to the theoretical loading amount and theoretical content, that is, the content and loading amount obtained by calculating the theoretical amount of each raw material and the theoretical amount of product generated.

[0081] Example 1

[0082] A method for preparing a low-temperature, high-efficiency ammonia decomposition hydrogen production catalyst, comprising the following steps:

[0083] (1) Preparation of precursor: CeO2 powder and BaTiO3 powder were first mixed by ball milling (the mass ratio of CeO2 powder to BaTiO3 powder was 1:10), then CaH2 powder was added (the molar ratio of CaH2 powder to BaTiO3 powder was 1:3.1) and ground. The mixture was then pressed into tablets in an inert gas atmosphere (the pressing pressure was 5 MPa and the diameter of the tablets was 20 mm). Finally, the pressed sample was placed in a vacuum furnace and calcined at 560℃ for 168 h at a rate of 5℃ / min (the vacuum degree in the furnace was maintained at 10℃ during the calcination process). -4 Pa), the calcined product was placed in a methanol aqueous solution (prepared by methanol and water in a volume ratio of 9:1) for washing and impurity removal, and then dried to obtain precursor powder (hydrogen-doped perovskite oxide loaded with CeO2).

[0084] (2) Preparation of polymetallic nitride support: 5g of precursor powder was placed in a vacuum tube furnace. The air in the furnace tube was first evacuated using a vacuum pump, and then nitrogen gas was continuously introduced at a rate of 100mL / min for atmosphere filling. The temperature control program was adjusted to raise the furnace tube temperature to 600℃ at a rate of 5℃ / min, and held for 6h. The temperature was then allowed to cool naturally to room temperature to obtain the polymetallic nitride support (i.e., nitrogen-doped perovskite oxide loaded with CeO2, wherein the CeO2 loading was 10wt%).

[0085] (3) Preparation of a low-temperature, high-efficiency ammonia decomposition hydrogen production catalyst: 1 g of a polymetallic nitrogen oxide support was dissolved in 60 mL of methanol, and 0.76 g of cobalt(III) acetylacetone was added. After magnetic stirring for 24 h, the mixed sample was evaporated to dryness using a rotary evaporator. The evaporated powder was then pressed into tablets in air (the pressing pressure was 5 MPa, and the diameter of the tablets was 20 mm). The tableted sample was then placed in a vacuum tube furnace for thermal annealing. The annealing conditions were: heating to 350 °C at a rate of 5 °C / min, holding at that temperature for 6 h, and then naturally cooling to room temperature. The vacuum degree inside the furnace was maintained at 10 °C during the annealing process. -4 Pa. The annealed sample was taken out and ground to obtain a polymetallic nitride supported on cobalt (specifically Co3O4) (with a Co content of 10.6 wt%), which is a low-temperature high-efficiency ammonia decomposition hydrogen production catalyst.

[0086] Example 2

[0087] A method for preparing a low-temperature, high-efficiency ammonia decomposition hydrogen production catalyst, comprising the following steps:

[0088] Steps (1) and (2) are the same as in Example 1.

[0089] (3) Preparation of a low-temperature, high-efficiency ammonia decomposition hydrogen production catalyst: 1 g of a polymetallic nitrogen oxide support was dissolved in 118 mL of methanol, and 1.52 g of cobalt(III) acetylacetone was added. After magnetic stirring for 24 h, the mixed sample was evaporated to dryness using a rotary evaporator. The evaporated powder was then pressed into tablets in air (the pressing pressure was 5 MPa, and the diameter of the tablets was 20 mm). The tableted sample was then placed in a vacuum tube furnace for high-temperature annealing. The annealing conditions were: heating to 350 °C at a rate of 5 °C / min, holding at that temperature for 6 h, and then naturally cooling to room temperature. The vacuum degree inside the furnace was maintained at 10 °C during the annealing process. -4 Pa. The annealed sample was taken out and ground to obtain a polymetallic nitride supported on cobalt (specifically Co3O4) (with a Co content of 18.5 wt%), which is a low-temperature high-efficiency ammonia decomposition hydrogen production catalyst.

[0090] Example 3

[0091] A method for preparing a low-temperature, high-efficiency ammonia decomposition hydrogen production catalyst, comprising the following steps:

[0092] (1) Preparation of precursor: CeO2 powder and BaTiO3 powder were first mixed by ball milling (the mass ratio of CeO2 powder to BaTiO3 powder was 1:10), then CaH2 powder was added (the molar ratio of CaH2 powder to BaTiO3 powder was 1:3.1) and ground. The mixture was then pressed into tablets in an inert gas atmosphere (the pressing pressure was 5 MPa and the diameter of the tablets was 20 mm). Finally, the pressed sample was placed in a vacuum furnace and calcined at 560℃ for 168 h at a rate of 5℃ / min (the vacuum degree in the furnace was maintained at 10℃ during the calcination process). -4 Pa), the calcined product was placed in a methanol aqueous solution (prepared by methanol and water in a volume ratio of 9:1) for washing and impurity removal, and then dried to obtain precursor powder (hydrogen-doped perovskite oxide loaded with CeO2).

[0093] (2) Preparation of polymetallic nitride support: 5g of precursor powder was placed in a vacuum tube furnace. Air was first extracted from the furnace tube using a vacuum pump, followed by continuous nitrogen flow at 100mL / min for atmosphere filling. The temperature control program was adjusted to raise the furnace tube temperature to 500℃ at a rate of 5℃ / min, held for 4 hours, and then allowed to cool naturally to room temperature to obtain the nitrided product (nitrogen-doped perovskite oxide loaded with CeO2). 0.125g of potassium acetate was dissolved in 10mL of water, and 1g of the nitrided product was added. After magnetic stirring for 4 hours, the mixed sample was evaporated to dryness using a rotary evaporator. The sample was then placed in a vacuum tube furnace for high-temperature annealing. The annealing conditions were: heating to 500℃ at a rate of 5℃ / min, holding for 4 hours, and then allowing to cool naturally to room temperature. The vacuum level inside the furnace was maintained at 10℃ during the annealing process. - 4 Pa yielded a multi-metal nitride support (i.e., a nitrogen-doped perovskite oxide loaded with CeO2 and K2O3, wherein the loading of CeO2 was 10 wt% and the loading of K2O3 was 2 wt%).

[0094] (3) Preparation of a low-temperature, high-efficiency ammonia decomposition hydrogen production catalyst: 1 g of a multi-metallic nitrogen oxide support was dissolved in 118 mL of methanol, and 1.52 g of cobalt(III) acetylacetone was added. After magnetic stirring for 24 h, the mixed sample was evaporated to dryness using a rotary evaporator. The evaporated powder was then pressed into tablets in air (the pressing pressure was 5 MPa, and the diameter of the tablets was 20 mm). The tableted sample was then placed in a vacuum tube furnace for thermal annealing. The annealing conditions were: heating to 350 °C at a rate of 5 °C / min, holding at that temperature for 6 h, and then naturally cooling to room temperature. The vacuum degree inside the furnace was maintained at 10 °C during the annealing process. -4Pa. The annealed sample was taken out and ground to obtain a polymetallic nitride supported on cobalt (specifically Co3O4) (with a Co content of 18.5 wt%), which is a low-temperature high-efficiency ammonia decomposition hydrogen production catalyst.

[0095] Comparative Example 1

[0096] The preparation steps of the ammonia decomposition hydrogen production catalyst (without introducing promoters) are as follows:

[0097] (1) Preparation of precursor: CaH2 powder and BaTiO3 powder were mixed and ground (the molar ratio of CaH2 powder to BaTiO3 powder was 1:3.1). The mixed powder was then pressed into tablets in an inert gas atmosphere (the pressing pressure was 5 MPa and the diameter of the tablet was 20 mm). Finally, the pressed sample was placed in a vacuum furnace and calcined at 560 °C for 168 h at a rate of 5 °C / min (the vacuum degree in the furnace was maintained at 10 °C during the calcination process). -4 Pa), the calcined product was placed in a methanol aqueous solution (prepared by mixing methanol and water in a volume ratio of 9:1) for washing and impurity removal, and then dried to obtain precursor powder (hydrogen-doped perovskite oxide).

[0098] (2) Preparation of the support: 5g of precursor powder was placed in a vacuum tube furnace. The air in the furnace tube was first extracted with a vacuum pump, and then nitrogen gas was continuously introduced at a rate of 100mL / min for atmosphere filling. The temperature control program was adjusted to raise the furnace tube temperature to 600℃ at a rate of 5℃ / min, and held for 6h. The temperature was then allowed to cool naturally to room temperature to obtain a nitrogen-doped perovskite oxide support.

[0099] (3) Preparation of ammonia decomposition hydrogen production catalyst: 1 g of nitrogen-doped perovskite oxide support was dissolved in 60 mL of methanol, and 0.76 g of cobalt(III) acetylacetone was added. After magnetic stirring for 24 h, the mixed sample was evaporated to dryness using a rotary evaporator. The evaporated powder was then pressed into tablets in air (pressing pressure of 5 MPa, tablet diameter of 20 mm), and then placed in a vacuum tube furnace for thermal annealing. The annealing conditions were: heating to 350 °C at a rate of 5 °C / min, holding at that temperature for 6 h, and naturally cooling to room temperature. The vacuum degree inside the furnace was maintained at 10 °C during the annealing process. -4 Pa. The annealed sample was taken out and ground to obtain a nitrogen-doped perovskite oxide loaded with cobalt (specifically Co3O4) (with a Co content of 10.6 wt%), which is the catalyst for ammonia decomposition to produce hydrogen.

[0100] Comparative Example 2

[0101] The preparation steps of the catalyst for hydrogen production from ammonia decomposition are as follows:

[0102] Steps (1) and (2) are the same as in Comparative Example 1.

[0103] (3) Preparation of ammonia decomposition hydrogen production catalyst: 1 g of nitrogen-doped perovskite oxide support was dissolved in 118 mL of methanol, and 1.52 g of cobalt(III) acetylacetone was added. After magnetic stirring for 24 h, the mixed sample was evaporated to dryness using a rotary evaporator. The evaporated powder was then pressed into tablets in air (pressing pressure of 5 MPa, tablet diameter of 20 mm), and then placed in a vacuum tube furnace for thermal annealing. The annealing conditions were: heating to 350 °C at a rate of 5 °C / min, holding at that temperature for 6 h, and naturally cooling to room temperature. The vacuum degree inside the furnace was maintained at 10 °C during the annealing process. -4 Pa. The annealed sample was taken out and ground to obtain a nitrogen-doped perovskite oxide loaded with cobalt (specifically Co3O4) (with a Co content of 18.5 wt%), which is the catalyst for ammonia decomposition to produce hydrogen.

[0104] Comparative Example 3

[0105] The preparation steps of the catalyst for hydrogen production from ammonia decomposition are as follows:

[0106] (1) Preparation of precursor: First, K2O3 powder, CeO2 powder and BaTiO3 powder were mixed by ball milling (mass ratio of K2O3 powder, CeO2 powder and BaTiO3 powder was 0.2:1:10), then CaH2 powder was added (molar ratio of CaH2 powder and BaTiO3 powder was 1:3.1) and ground. The mixture was then pressed into tablets in an inert gas atmosphere (pressing pressure was 5 MPa, and the diameter of the tablet was 20 mm). Finally, the pressed sample was placed in a vacuum furnace and calcined at 560℃ for 168 h at a rate of 5℃ / min (the vacuum degree in the furnace was maintained at 10℃ during the calcination process). -4 Pa), the calcined product was placed in a methanol aqueous solution (prepared by methanol and water in a volume ratio of 9:1) for washing and impurity removal, and then dried to obtain precursor powder (hydrogen-doped perovskite oxide loaded with CeO2 and K2O3).

[0107] (2) Preparation of polymetallic nitride support: 5g of precursor powder was placed in a vacuum tube furnace. The air in the furnace tube was first evacuated by a vacuum pump, and then nitrogen gas was continuously introduced at a rate of 100mL / min for atmosphere filling. The temperature control program was adjusted to raise the furnace tube temperature to 500℃ at a rate of 5℃ / min, and held for 4h. The temperature was then allowed to cool naturally to room temperature to obtain a polymetallic nitride support (i.e., nitrogen-doped perovskite oxide loaded with CeO2 and K2O3, wherein the loading of CeO2 was 10wt% and the loading of K2O3 was 2wt%).

[0108] (3) Preparation of a low-temperature, high-efficiency ammonia decomposition hydrogen production catalyst: 1 g of a multi-metallic nitrogen oxide support was dissolved in 118 mL of methanol, and 1.52 g of cobalt(III) acetylacetone was added. After magnetic stirring for 24 h, the mixed sample was evaporated to dryness using a rotary evaporator. The evaporated powder was then pressed into tablets in air (the pressing pressure was 5 MPa, and the diameter of the tablets was 20 mm). The tableted sample was then placed in a vacuum tube furnace for thermal annealing. The annealing conditions were: heating to 350 °C at a rate of 5 °C / min, holding at that temperature for 6 h, and then naturally cooling to room temperature. The vacuum degree inside the furnace was maintained at 10 °C during the annealing process. -4 Pa. The annealed sample was taken out and ground to obtain a polymetallic nitride supported on cobalt (specifically Co3O4) (with a Co content of 18.5 wt%), which is a low-temperature high-efficiency ammonia decomposition hydrogen production catalyst.

[0109] Comparative Example 4

[0110] The preparation steps of the catalyst for hydrogen production from ammonia decomposition are as follows:

[0111] (1) Preparation of precursor: CeO2 powder and BaTiO3 powder were first mixed by ball milling (the mass ratio of CeO2 powder to BaTiO3 powder was 1:10), then CaH2 powder was added (the molar ratio of CaH2 powder to BaTiO3 powder was 1:3.1) and ground. The mixture was then pressed into tablets in an inert gas atmosphere (the pressing pressure was 5 MPa and the diameter of the tablets was 20 mm). Finally, the pressed sample was placed in a vacuum furnace and calcined at 560℃ for 168 h at a rate of 5℃ / min (the vacuum degree in the furnace was maintained at 10℃ during the calcination process). -4 Pa), the calcined product was placed in a methanol aqueous solution (prepared by methanol and water in a volume ratio of 9:1) for washing and impurity removal, and then dried to obtain precursor powder (hydrogen-doped perovskite oxide loaded with CeO2).

[0112] (2) Preparation of ammonia decomposition hydrogen production catalyst: 1 g of precursor powder was dissolved in 118 mL of methanol, and 1.52 g of cobalt(III) acetylacetonate was added. After magnetic stirring for 24 h, the mixed sample was evaporated to dryness using a rotary evaporator. The evaporated powder was then pressed into tablets in air (pressing pressure was 5 MPa, and the diameter of the tablets was 20 mm). The tableted sample was then placed in a vacuum tube furnace for thermal annealing. The annealing conditions were: heating to 350 °C at a rate of 5 °C / min, holding at that temperature for 6 h, and then naturally cooling to room temperature. The vacuum degree inside the furnace was maintained at 10 °C during the annealing process. -4 Pa. The annealed sample was taken out and ground to obtain a precursor loaded with cobalt (specifically Co3O4) (with a Co content of 18.5 wt%), which is the catalyst for hydrogen production from ammonia decomposition.

[0113] Comparative Example 5

[0114] The preparation of the ammonia decomposition hydrogen production catalyst (without tableting before thermal annealing in step (3)) is as follows:

[0115] (1) Preparation of precursor: CeO2 powder and BaTiO3 powder were first mixed by ball milling (the mass ratio of CeO2 powder to BaTiO3 powder was 1:10), then CaH2 powder was added (the molar ratio of CaH2 powder to BaTiO3 powder was 1:3.1) and ground. The mixture was then pressed into tablets in an inert gas atmosphere (the pressing pressure was 5 MPa and the diameter of the tablets was 20 mm). Finally, the pressed sample was placed in a vacuum furnace and calcined at 560℃ for 168 h at a rate of 5℃ / min (the vacuum degree in the furnace was maintained at 10℃ during the calcination process). -4 Pa), the calcined product was placed in a methanol aqueous solution (prepared by methanol and water in a volume ratio of 9:1) for washing and impurity removal, and then dried to obtain precursor powder (hydrogen-doped perovskite oxide loaded with CeO2).

[0116] (2) Preparation of polymetallic nitride support: 5g of precursor powder was placed in a vacuum tube furnace. The air in the furnace tube was first evacuated using a vacuum pump, and then nitrogen gas was continuously introduced at a rate of 100mL / min for atmosphere filling. The temperature control program was adjusted to raise the furnace tube temperature to 600℃ at a rate of 5℃ / min, and held for 6h. The temperature was then allowed to cool naturally to room temperature to obtain the polymetallic nitride support (i.e., nitrogen-doped perovskite oxide loaded with CeO2, wherein the CeO2 loading was 10wt%).

[0117] (3) Preparation of ammonia decomposition hydrogen production catalyst: 1 g of polymetallic nitrogen oxide support was dissolved in 118 mL of methanol, and 1.52 g of cobalt(III) acetylacetone was added. After magnetic stirring for 24 h, the mixed sample was evaporated to dryness using a rotary evaporator. The evaporated powder was placed in a vacuum tube furnace for thermal annealing. The annealing conditions were: heating to 350 °C at a rate of 5 °C / min, holding at that temperature for 6 h, and then naturally cooling to room temperature. The vacuum degree inside the furnace was maintained at 10 °C during the annealing process. -4 Pa. The annealed sample was taken out and ground to obtain a polymetallic nitride supported on cobalt (specifically Co3O4) (with a Co content of 18.5 wt%), which is the catalyst for hydrogen production from ammonia decomposition.

[0118] Test case

[0119] Figure 1The images show photographs of the precursor powder (a) obtained in step (1) of Example 1, the multi-metal nitride support (b) obtained in step (2), and the ammonia decomposition hydrogen production catalyst (c) obtained in step (3). It can be seen that the color and appearance of the samples obtained at different preparation stages change significantly, proving that the material composition changed at different preparation stages.

[0120] Figure 2 The XRD patterns are of the precursor powder (a) obtained in step (1) of Example 1, the multi-metal nitride support (b) obtained in step (2), and the ammonia decomposition hydrogen production catalyst (c) obtained in step (3). It can be seen that cobalt tetroxide can be loaded onto the surface of the multi-metal nitride support through heat treatment, providing a source of cobalt for the subsequent reduction stage (the hydrogen doping in the precursor powder and the nitrogen doping in the multi-metal nitride cannot be detected by XRD and are characterized by subsequent XPS spectra).

[0121] Figure 3 XPS spectra of the precursor powder (a) obtained in step (1) of Example 1 and the multi-metal nitride support (b) obtained in step (2). It can be seen that the precise analysis of specific elements proves that nitrogen completely replaces hydrogen in the nitrided material, proving the reliability of nitriding doping.

[0122] Application examples

[0123] The catalysts prepared in the various examples and comparative examples were used in the ammonia decomposition to produce hydrogen reaction under the following reaction conditions:

[0124] Under normal pressure, a nitrogen-hydrogen mixture (25 vol% nitrogen + 75 vol% hydrogen) was first introduced as a reducing gas to reduce the catalyst. The reducing gas flow rate was 100 mL / min, the reduction temperature was 500℃, and the reduction time was 5 h. Then, pure ammonia was introduced as a reactant to carry out the ammonia decomposition to hydrogen reaction at different reaction temperatures. The space velocity of the reaction was 12000 h⁻¹. -1 The ammonia conversion rate of different catalysts at different temperatures was tested, and the results are shown in Table 1.

[0125] Table 1

[0126]

[0127] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a low-temperature, high-efficiency ammonia decomposition hydrogen production catalyst, characterized in that, Includes the following steps: A multi-metal nitride support was prepared by solid-state synthesis and nitriding treatment using perovskite oxide, an auxiliary source, and CaH2 as raw materials. The multi-metal nitride support, a cobalt-containing compound, and a solvent were mixed and dried to obtain a mixed powder. The mixed powder was then pressed into tablets and subjected to thermal annealing to obtain the low-temperature high-efficiency ammonia decomposition hydrogen production catalyst. The auxiliary agent source includes one or more of CeO2 and potassium acetate; The perovskite oxides include CaTiO3, SrTiO3, BaTiO3, or PbTiO3; The auxiliary agent source is CeO2. The steps for preparing the polymetallic nitride support by solid-phase synthesis and nitriding treatment include: mixing perovskite oxide, CeO2 and CaH2, pressing into tablets and then performing calcination and nitriding treatments in sequence to obtain the polymetallic nitride support. Alternatively, the auxiliary agent source is potassium acetate. The steps for preparing the polymetallic nitride support by solid-phase synthesis and nitriding treatment include: mixing perovskite oxide and CaH2, pressing into tablets, and then subjecting them to calcination and nitriding treatment in sequence; mixing the nitriding product with potassium acetate solution, drying, and high-temperature annealing treatment to obtain the polymetallic nitride support. Alternatively, the auxiliary source is CeO2 and potassium acetate. The steps for preparing the polymetallic nitride support by solid-phase synthesis and nitriding treatment include: mixing perovskite oxide, CeO2 and CaH2, pressing into tablets and then subjecting them to calcination and nitriding treatment in sequence; mixing the nitriding product with potassium acetate solution, drying, and high-temperature annealing treatment to obtain the polymetallic nitride support. The loading of CeO2 in the polymetallic nitride support is 5-10 wt%, and / or the loading of K2O3 is 2-5 wt%. The Co content in the low-temperature high-efficiency ammonia decomposition hydrogen production catalyst is 5-25 wt%.

2. The preparation method of the low-temperature high-efficiency ammonia decomposition hydrogen production catalyst as described in claim 1, characterized in that, The molar ratio of CaH2 to the perovskite oxide is 1:3-3.

3.

3. The preparation method of the low-temperature high-efficiency ammonia decomposition hydrogen production catalyst as described in claim 1, characterized in that, The calcination treatment is carried out at a temperature of 560-600℃ for a time of 24-168 h. And / or, the specific operation of the nitriding treatment is as follows: nitriding treatment at 300-600℃ for 6-10 h at a nitrogen flow rate of 50-100 mL / min; And / or, the high-temperature annealing treatment is performed at a temperature of 300-500℃ for a time of 3-6 hours.

4. The preparation method of the low-temperature high-efficiency ammonia decomposition hydrogen production catalyst as described in claim 1, characterized in that, The heat annealing process is performed at a temperature of 200-360℃ for 3-6 hours.

5. A low-temperature high-efficiency ammonia decomposition hydrogen production catalyst prepared by the preparation method according to any one of claims 1-4.

6. The application of the low-temperature high-efficiency ammonia decomposition hydrogen production catalyst as described in claim 5 in the ammonia decomposition hydrogen production reaction.

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