A method of chemical looping ammonia decomposition

Abstract

The application discloses a method for chemical chain ammonia decomposition, specifically comprising the following steps: a. ammonia gas is contacted with alkali metal M to obtain an amino compound, and the amino compound is ball milled with a catalyst to obtain a material body; b. the material body is placed in a sealed container under a non-active atmosphere, and is decomposed to obtain nitrogen, hydrogen and regenerated alkali metal. The method provided by the application can carry out ammonia decomposition at low temperature, the reaction condition is mild, the process is easy to control, is not only suitable for small-scale and distributed ammonia decomposition for hydrogen production, but also can take the amino compound as a solid ammonia carrier, and transportation is convenient.

Description

Technical Field

[0001] This application relates to a method for chemical chain decomposition of ammonia, belonging to the field of ammonia decomposition. Background Technology

[0002] With increasing environmental pollution and the greenhouse effect, hydrogen, as a highly efficient and clean secondary energy carrier, possesses unparalleled advantages over traditional energy sources, such as high density, high calorific value, and wide availability of raw materials. In recent decades, the development and utilization of hydrogen energy and fuel cell technologies have been listed as a key research area in the field of clean energy by countries worldwide. The large-scale utilization of hydrogen energy involves three related stages: hydrogen production, storage and transportation, and application. Among these, efficient and safe hydrogen storage technology is a key technology affecting the promotion and application of hydrogen fuel cell vehicles and is currently the main technical obstacle to the large-scale application of hydrogen energy.

[0003] Compared with other hydrogen production technologies, ammonia decomposition for hydrogen production (2NH3=N2+3H2) has the following main advantages: (1) the related technologies and infrastructure for ammonia synthesis, storage and transportation are mature; (2) the annual output of ammonia is large and the production price is relatively low; (3) it has a high hydrogen density (hydrogen content 17.7wt%) and a high energy density; (4) it is easy to store and transport; (5) the hydrogen production process is simple and the product is CO-free. x (6) It is environmentally friendly; (7) It has good safety and a narrow explosion limit range. In recent years, ammonia catalytic decomposition has provided CO-free fuel cells. x Hydrogen technology has begun to receive widespread attention and is considered one of the effective ways to solve the hydrogen energy source problem for fuel cells. The key to developing ammonia decomposition hydrogen production technology using ammonia as a hydrogen source carrier and realizing its co-operation with on-board PEMFC systems is to develop ammonia decomposition catalysts with high activity and high stability at the lowest possible temperature.

[0004] Currently, the catalysts used in the ammonia decomposition to produce hydrogen mainly include noble metal catalysts (Ir, Pt, etc.) represented by Ru and transition metal catalysts (Co, Mo, etc.) represented by Fe and Ni. Fe and Ni-based catalysts are inexpensive, but have low catalytic activity and require temperatures above 700℃ to achieve high conversion.

[0005] Chemical looping is an emerging research field that has shown advantages in areas such as fossil fuel combustion, syngas production, and hydrogen generation. In recent years, the chemical looping process for ammonia synthesis has attracted increasing attention due to its ease of coupling with renewable energy sources, atmospheric pressure operation, and avoidance of reactant adsorption competition. However, the use of chemical looping for ammonia decomposition is still rarely reported, indicating significant research potential. Summary of the Invention

[0006] The purpose of this application is to provide a new ammonia decomposition circuit, which can achieve a 100% ammonia conversion rate at low temperatures and significantly reduce energy consumption compared with traditional processes.

[0007] According to one aspect of this application, a method for the chemical chain decomposition of ammonia is provided, comprising the following steps:

[0008] a) Ammonia gas and alkali metal M are reacted to obtain an amino compound, and the amino compound is ball-milled with a catalyst to obtain the main material;

[0009] b. Under an inactive atmosphere, the material body is placed in a sealed container and decomposed to obtain nitrogen, hydrogen and recycled alkali metal.

[0010] Optionally, the alkali metal M is selected from Group IA or IIA elements.

[0011] Optionally, the Group IA and IIA elements are selected from at least one of Li, Na, K, Rb, Cs, Mg, Ca, Sr, and Ba.

[0012] Optionally, the amino compound has the molecular formula M. x N y H m(3y-nx) n is the chemical valence state of M, which is 1 or 2, and m is the chemical valence state of H, which is 1 or -1.

[0013] When m = 1, the molecular formula is M. x N y H 3y-nx x = 1 to 2, y = 0 to 3;

[0014] When m = -1, the molecular formula is M. x N y H nx-3y x = 1 to 3, y = 0 to 1.

[0015] Optionally, the catalyst is a transition metal.

[0016] Optionally, the transition metal is selected from at least one of V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Pb, Ag, Hf, Ta, Re, Os, Ir, Pt, and Au.

[0017] Optionally, the inactive atmosphere is selected from at least one of helium, neon, and argon.

[0018] Optionally, the molar ratio of the alkali metal to the ammonia is 1:1 to 10.

[0019] Optionally, the molar ratio of the alkali metal to the ammonia is selected from any ratio or a range between two ratios, such as 1:1, 1:2.5, 1:5, 1:7.5, and 1:10.

[0020] Optionally, the catalyst accounts for 50% to 90% of the bulk material.

[0021] Optionally, the mass of the catalyst accounts for any value or a range between 50%, 60%, 70%, 80%, and 90% of the bulk material.

[0022] Optionally, in step a, the reaction conditions are: temperature 25–300°C, ammonia pressure 1–10 bar, and time 2–24 h.

[0023] Optionally, the temperature of the reaction is selected from any value or a range between two values ​​from 25°C, 50°C, 100°C, 200°C, and 300°C.

[0024] Optionally, the ammonia pressure of the reaction is selected from any value of 1 bar, 2 bar, 5 bar, 8 bar, 10 bar, or a range between two values.

[0025] Optionally, the reaction time is selected from any value of 2h, 5h, 10h, 15h, 24h or a range between two values.

[0026] Optionally, the ball milling conditions are: rotation speed of 150-300 rpm and time of 1-24 hours.

[0027] Optionally, in step b, the decomposition conditions are: temperature 250–600°C, and space velocity of 10000 ml / g / h–60000 ml / g / h in a non-inert atmosphere.

[0028] Optionally, the decomposition temperature is selected from any value or a range between two values ​​from 250°C, 300°C, 400°C, 500°C, and 600°C.

[0029] Optionally, the air velocity is selected from any value or a range between two values ​​from 10000 ml / g / h, 20000 ml / g / h, 30000 ml / g / h, 40000 ml / g / h, and 60000 ml / g / h.

[0030] The chemical chain ammonia decomposition process provided by this invention can be used to prepare CO-free ammonia gas during the ammonia decomposition process. x It can absorb hydrogen gas. Furthermore, it can solidify ammonia at room temperature, and at a maximum temperature of 500℃, it can completely convert the ammonia gas absorbed by the material into nitrogen and hydrogen gas.

[0031] The beneficial effects that this application can produce include:

[0032] 1) The method provided in this application is simple to operate and operates under mild conditions in the chemical chaining process.

[0033] 2) The method provided in this application involves the alkali metal ammonia fixation process being carried out at room temperature, and the ammonia compound can be decomposed to produce hydrogen at a minimum temperature of 250°C under the action of a catalyst.

[0034] 3) The method provided in this application can achieve complete fixation of ammonia at 300°C during the chemical chain ammonia decomposition process.

[0035] 4) The intermediate product amino catalyst prepared by the method provided in this application can be used as a solid ammonia support, which is convenient for storage and transportation. Detailed Implementation

[0036] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0037] Unless otherwise specified, the raw materials and catalysts used in the embodiments of this application were all purchased commercially.

[0038] Comparative Example 1.

[0039] Ammonia gas at a pressure of 1 ar was brought into contact with metallic sodium and reacted at 25°C for 5 hours to obtain NaNH2; wherein the molar ratio of ammonia gas to metallic sodium was 1:5.

[0040] In an argon glove box, 0.0300 g of the prepared NaNH2 sample was accurately weighed and placed in a fixed-bed stainless steel reactor. The sample was first heated to 400 °C in an Ar atmosphere at atmospheric pressure, with a gas flow rate controlled at 30 ml / min. The generated hydrogen gas was tracked using gas chromatography. This was a single activity measurement. If the reaction was to proceed continuously, chromatographic tracking continued until no more hydrogen gas was produced. After 3 hours, the gas was switched to a 10% NH3-Ar mixture, and the reaction was carried out at room temperature for 6 hours. The above process was then repeated. As shown in Table 1, the hydrogen production rate from the chemical chain decomposition of NaNH2 by ammonia was 198 μmol / g. -1 min -1 .

[0041] Comparative Example 2.

[0042] Ammonia gas at a pressure of 1 bar was brought into contact with metallic potassium and reacted at 25°C for 5 hours to obtain KNH2; the molar ratio of ammonia gas to metallic potassium was 1:5.

[0043] In an argon glove box, 0.0300 g of the prepared KNH2 sample was accurately weighed and placed in a fixed-bed stainless steel reactor. The sample was first heated to 400 °C in an Ar atmosphere at atmospheric pressure, with a gas flow rate controlled at 30 ml / min. The generated hydrogen gas was tracked using gas chromatography. This was a single activity measurement. If the reaction was to proceed continuously, chromatographic tracking continued until no more hydrogen gas was produced. After 3 hours, the gas was switched to a 10% NH3-Ar mixture, and the reaction was carried out at room temperature for 6 hours. The above process was then repeated. As shown in Table 1, the hydrogen production rate from the chemical chain reaction of KNH2 via ammonia decomposition was 237 μmol / g. -1 min -1 .

[0044] Example 1.

[0045] Ammonia gas at a pressure of 1 bar was contacted with metallic sodium and reacted at 25°C for 5 hours to obtain NaNH2. 1 g of NaNH2 and 1 g of transition metal Fe were placed in a stainless steel ball mill jar and ball-milled at 200 rpm for 2 hours to obtain 50% Fe-NaNH2.

[0046] In an argon glove box, 0.0300 g of the prepared 50% Fe-NaNH2 sample was accurately weighed and placed in a fixed-bed stainless steel reactor. The sample was first heated to 400 °C in an Ar atmosphere at atmospheric pressure, with a gas flow rate controlled at 30 ml / min. The generated hydrogen gas was tracked by gas chromatography. This was a single activity measurement. If the reaction was to proceed continuously, chromatographic tracking continued until no more hydrogen gas was produced. After 3 hours, the gas was switched to a 10% NH3-Ar mixture, and the reaction was carried out at room temperature for 6 hours. The above process was then repeated. As shown in Table 1, the hydrogen production rate of the chemical chain ammonia decomposition of 50% Fe-NaNH2 was 1073 μmol.g -1 min -1 .

[0047] Example 2.

[0048] Ammonia gas at a pressure of 1 bar was contacted with metallic sodium and reacted at 25°C for 5 hours to obtain NaNH2. 1 g of NaNH2 and 1 g of transition metal Mn were placed in a stainless steel ball mill jar and ball-milled at 200 rpm for 2 hours to obtain 50% Mn-NaNH2.

[0049] In an argon glove box, 0.0300 g of the prepared 50% Mn-NaNH2 sample was accurately weighed and placed in a fixed-bed stainless steel reactor. The sample was first heated to 400 °C in an Ar atmosphere at atmospheric pressure, with a gas flow rate controlled at 30 ml / min. The generated hydrogen gas was tracked by gas chromatography. This was a single activity measurement. If the reaction was to proceed continuously, chromatographic tracking continued until no more hydrogen gas was produced. After 3 hours, the gas was switched to a 10% NH3-Ar mixture, and the reaction was carried out at room temperature for 6 hours. The above process was then repeated. As shown in Table 1, the hydrogen production rate of the chemical chain ammonia decomposition of 50% Mn-NaNH2 was 1854 μmol / g. -1 min -1 .

[0050] Example 3.

[0051] Ammonia gas at a pressure of 1 bar was contacted with metallic sodium and reacted at 25°C for 5 hours to obtain NaNH2. 1 g of NaNH2 and 1 g of transition metal Co were placed in a stainless steel ball mill jar and ball-milled at 200 rpm for 2 hours to obtain 50% Co-NaNH2.

[0052] In an argon glove box, 0.0300 g of the prepared 50% Co-NaNH2 sample was accurately weighed and placed in a fixed-bed stainless steel reactor. The sample was first heated to 400℃ in an Ar atmosphere at atmospheric pressure, with a gas flow rate controlled at 30 ml / min. The generated hydrogen gas was tracked by gas chromatography. This was a single activity measurement. If the reaction was to proceed continuously, chromatographic tracking continued until no more hydrogen gas was produced. After 3 hours, the gas was switched to a 10% NH3-Ar mixture, and the reaction was carried out at room temperature for 6 hours. The above process was then repeated. As shown in Table 1, the hydrogen production rate of the chemical chain ammonia decomposition of 50% Co-NaNH2 was 945 μmol / g. -1 min -1 .

[0053] Example 4.

[0054] Ammonia gas at a pressure of 1 bar was contacted with metallic sodium and reacted at 25°C for 5 hours to obtain NaNH2. 1 g of NaNH2 and 1 g of transition metal Ni were placed in a stainless steel ball mill jar and ball-milled at 200 rpm for 2 hours to obtain 50% Ni-NaNH2.

[0055] In an argon glove box, 0.0300 g of the prepared 50% Ni-NaNH2 sample was accurately weighed and placed in a fixed-bed stainless steel reactor. The sample was first heated to 400 °C in an Ar atmosphere at atmospheric pressure, with a gas flow rate controlled at 30 ml / min. The generated hydrogen gas was tracked using gas chromatography. This was a single activity measurement. If the reaction was to proceed continuously, chromatographic tracking continued until no more hydrogen gas was produced. After 3 hours, the gas was switched to a 10% NH3-Ar mixture, and the reaction was carried out at room temperature for 6 hours. The above process was then repeated. As shown in Table 1, the hydrogen production rate from the chemical chain ammonia decomposition of 50% Ni-NaNH2 was 718 μmol / g. -1 min -1 .

[0056] Example 5.

[0057] Ammonia gas at a pressure of 1 bar was contacted with metallic sodium and reacted at 25°C for 5 hours to obtain NaNH2. 1 g of NaNH2 and 1 g of transition metal Cu were placed in a stainless steel ball mill jar and ball-milled at 200 rpm for 2 hours to obtain 50% Cu-NaNH2.

[0058] In an argon glove box, 0.0300 g of the prepared 50% Cu-NaNH2 sample was accurately weighed and placed in a fixed-bed stainless steel reactor. The sample was first heated to 400 °C in an Ar atmosphere at atmospheric pressure, with a gas flow rate controlled at 30 ml / min. The generated hydrogen gas was tracked by gas chromatography. This was a single activity measurement. If the reaction was to proceed continuously, chromatographic tracking continued until no more hydrogen gas was produced. After 3 hours, the gas was switched to a 10% NH3-Ar mixture, and the reaction was carried out at room temperature for 6 hours. The above process was then repeated. As shown in Table 1, the hydrogen production rate of the chemical chain ammonia decomposition of 50% Cu-NaNH2 was 639 μmol / g. -1 min -1 .

[0059] Example 6.

[0060] Ammonia gas at a pressure of 1 bar was contacted with metallic sodium and reacted at 25°C for 5 hours to obtain NaNH2. 1 g of NaNH2 and 1 g of transition metal Ru were placed in a stainless steel ball mill jar and ball-milled at 200 rpm for 2 hours to obtain 50% Ru-NaNH2.

[0061] In an argon glove box, 0.0300 g of the prepared 50% Ru-NaNH2 sample was accurately weighed and placed in a fixed-bed stainless steel reactor. The sample was first heated to 400 °C in an Ar atmosphere at atmospheric pressure, with a gas flow rate controlled at 30 ml / min. The generated hydrogen gas was tracked by gas chromatography. This was a single activity measurement. If the reaction was to proceed continuously, chromatographic tracking continued until no more hydrogen gas was produced. After 3 hours, the gas was switched to a 10% NH3-Ar mixture, and the reaction was carried out at room temperature for 6 hours. The above process was then repeated. As shown in Table 1, the chemical chain ammonia decomposition hydrogen production rate of 50% Ru-NaNH2 was 1448 μmol.g -1 min -1 .

[0062] Example 7.

[0063] Ammonia gas at a pressure of 1 bar was contacted with metallic potassium and reacted at 25°C for 5 hours to obtain KNH2. 1 g of KNH2 and 1 g of transition metal Ru were placed in a stainless steel ball mill jar and ball-milled at 200 rpm for 2 hours to obtain 50% Ru-KNH2.

[0064] In an argon glove box, 0.0300 g of the prepared 50% Fe-KNH2 sample was accurately weighed and placed in a fixed-bed stainless steel reactor. The sample was first heated to 400 °C in an Ar atmosphere at atmospheric pressure, with a gas flow rate controlled at 30 ml / min. The generated hydrogen gas was tracked by gas chromatography. This was a single activity measurement. If the reaction was to proceed continuously, chromatographic tracking continued until no more hydrogen gas was produced. After 3 hours, the gas was switched to a 10% NH3-Ar mixture, and the reaction was carried out at room temperature for 6 hours. The above process was then repeated. As shown in Table 1, the hydrogen production rate of the chemical chain ammonia decomposition of 50% Fe-KNH2 was 1558 μmol / g. -1 min -1 .

[0065] Example 8.

[0066] Ammonia gas at a pressure of 1 bar was contacted with metallic potassium and reacted at 25°C for 5 hours to obtain KNH2. 1 g of KNH2 and 1 g of transition metal Mn were placed in a stainless steel ball mill jar and ball-milled at 200 rpm for 2 hours to obtain 50% Mn-KNH2.

[0067] In an argon glove box, 0.0300 g of the prepared 50% Mn-KNH2 sample was accurately weighed and placed in a fixed-bed stainless steel reactor. The sample was first heated to 400 °C in an Ar atmosphere at atmospheric pressure, with a gas flow rate controlled at 30 ml / min. The generated hydrogen gas was tracked by gas chromatography. This was a single activity measurement. If the reaction was to proceed continuously, chromatographic tracking continued until no more hydrogen gas was produced. After 3 hours, the gas was switched to a 10% NH3-Ar mixture, and the reaction was carried out at room temperature for 6 hours. The above process was then repeated. As shown in Table 1, the hydrogen production rate of the chemical chain ammonia decomposition of 50% Mn-KNH2 was 2657 μmol / g. -1 min -1 .

[0068] Example 9.

[0069] Ammonia gas at a pressure of 1 bar was contacted with metallic potassium and reacted at 25°C for 5 hours to obtain KNH2. 1 g of KNH2 and 1 g of transition metal Co were placed in a stainless steel ball mill jar and ball-milled at 200 rpm for 2 hours to obtain 50% Co-KNH2.

[0070] In an argon glove box, 0.0300 g of the prepared 50% Co-KNH2 sample was accurately weighed and placed in a fixed-bed stainless steel reactor. The sample was first heated to 400 °C in an Ar atmosphere at atmospheric pressure, with a gas flow rate controlled at 30 ml / min. The generated hydrogen gas was tracked by gas chromatography. This was a single activity measurement. If the reaction was to proceed continuously, chromatographic tracking continued until no more hydrogen gas was produced. After 3 hours, the gas was switched to a 10% NH3-Ar mixture, and the reaction was carried out at room temperature for 6 hours. The above process was then repeated. As shown in Table 1, the hydrogen production rate of the chemical chain ammonia decomposition of 50% Co-KNH2 was 1183 μmol / g. -1 min -1 .

[0071] Example 10.

[0072] Ammonia gas at a pressure of 1 bar was contacted with metallic potassium and reacted at 25°C for 5 hours to obtain KNH2. 1 g of KNH2 and 1 g of transition metal Ni were placed in a stainless steel ball mill jar and ball-milled at 200 rpm for 2 hours to obtain 50% Ni-KNH2.

[0073] In an argon glove box, 0.0300 g of the prepared 50% Ni-KNH2 sample was accurately weighed and placed in a fixed-bed stainless steel reactor. The sample was first heated to 400 °C in an Ar atmosphere at atmospheric pressure, with a gas flow rate controlled at 30 ml / min. The generated hydrogen gas was tracked using gas chromatography. This was a single activity measurement. If the reaction was to proceed continuously, chromatographic tracking continued until no more hydrogen gas was produced. After 3 hours, the gas was switched to a 10% NH3-Ar mixture, and the reaction was carried out at room temperature for 6 hours. The above process was then repeated. As shown in Table 1, the hydrogen production rate from the chemical chain ammonia decomposition of 50% Ni-KNH2 was 961 μmol / g. -1 min -1 .

[0074] Example 11.

[0075] Ammonia gas at a pressure of 1 bar was contacted with metallic potassium and reacted at 25°C for 5 hours to obtain KNH2. 1 g of KNH2 and 1 g of transition metal Cu were placed in a stainless steel ball mill jar and ball-milled at 200 rpm for 2 hours to obtain 50% Cu-KNH2.

[0076] In an argon glove box, 0.0300 g of the prepared 50% Cu-KNH2 sample was accurately weighed and placed in a fixed-bed stainless steel reactor. The sample was first heated to 400 °C in an Ar atmosphere at atmospheric pressure, with a gas flow rate controlled at 30 ml / min. The generated hydrogen gas was tracked by gas chromatography. This was a single activity measurement. If the reaction was to proceed continuously, chromatographic tracking continued until no more hydrogen gas was produced. After 3 hours, the gas was switched to a 10% NH3-Ar mixture, and the reaction was carried out at room temperature for 6 hours. The above process was then repeated. As shown in Table 1, the hydrogen production rate of the chemical chain ammonia decomposition of 50% Cu-KNH2 was 734 μmol / g. -1 min -1 .

[0077] Example 12.

[0078] Ammonia gas at a pressure of 1 bar was contacted with metallic potassium and reacted at 25°C for 5 hours to obtain KNH2. 1 g of KNH2 and 1 g of transition metal Ru were placed in a stainless steel ball mill jar and ball-milled at 200 rpm for 2 hours to obtain 50% Ru-KNH2.

[0079] In an argon glove box, 0.0300 g of the prepared 50% Ru-KNH2 sample was accurately weighed and placed in a fixed-bed stainless steel reactor. The sample was first heated to 400 °C in an Ar atmosphere at atmospheric pressure, with a gas flow rate controlled at 30 ml / min. The generated hydrogen gas was tracked by gas chromatography. This was a single activity measurement. If the reaction was to proceed continuously, chromatographic tracking continued until no more hydrogen gas was produced. After 3 hours, the gas was switched to a 10% NH3-Ar mixture, and the reaction was carried out at room temperature for 6 hours. The above process was then repeated. As shown in Table 1, the hydrogen production rate of the chemical chain ammonia decomposition of 50% Ru-KNH2 was 1938 μmol / g. -1 min -1 .

[0080] Table 1. Hydrogen production rate from ammonia decomposition in a chemical chain.

[0081] Material body Hydrogen production rate (umol / g / min) <![CDATA[NaNH2]]> 198 <![CDATA[KNH2]]> 237 <![CDATA[50%Fe-NaNH2]]> 1073 <![CDATA[50%Co-NaNH2]]> 945 <![CDATA[50%Ni-NaNH2]]> 718 <![CDATA[50%Cu-NaNH2]]> 639 <![CDATA[50%Ru-NaNH2]]> 1448 <![CDATA[50%Mn-NaNH2]]> 1854 <![CDATA[50%Fe-KNH2]]> 1558 <![CDATA[50%Co-KNH2]]> 1183 <![CDATA[50%Ni-KNH2]]> 961 <![CDATA[50%Cu-KNH2]]> 734 <![CDATA[50%Ru-KNH2]]> 1938 <![CDATA[50%Mn-KNH2]]> 2657

[0082] Table 1 shows that NaNH2 and KNH2 can achieve a chemical chain decomposition of ammonia under mild conditions. The introduction of transition metals can significantly increase the rate of hydrogen production from the decomposition of amino compounds. Ru and Mn show the best promoting effect. Under the same conditions, the hydrogen production rate of KNH2 is higher than that of NaNH2. In this chemical chain decomposition process, the first step can be completed at room temperature, and the second step can achieve complete hydrogen production below 400℃. For ammonia decomposition, the chemical chain process provided by this invention can greatly reduce the reaction temperature and achieve ammonia decomposition under mild conditions.

[0083] 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 the chemical chain decomposition of ammonia, characterized in that, Specifically, the following steps are included: a) Ammonia gas and alkali metal M are reacted to obtain an amino compound, and the amino compound is ball-milled with a catalyst to obtain the main material; b. Under an inactive atmosphere, the main body of the material is placed in a sealed container and decomposed to obtain nitrogen, hydrogen and recycled alkali metal; The alkali metal M is selected from elements of Group IA and IIA. In step a, the reaction conditions are: temperature 25~300℃, ammonia pressure 1~10 bar, time 2~24 h; The catalyst is a transition metal; The transition metal is selected from at least one of Mn, Fe, Co, Ni, Cu, and Ru; In step b, the decomposition temperature is 250~600℃.

2. The method according to claim 1, characterized in that, The Group IA and IIA elements are selected from at least one of Li, Na, K, Rb, Cs, Mg, Ca, Sr, and Ba.

3. The method according to claim 1, characterized in that, The molecular formula of the amino compound is M x N y H m(3y-nx) n is the chemical valence state of M, which is 1 or 2, and m is the chemical valence state of H, which is 1 or -1. When m=1, the molecular formula is M x N y H 3y-nx x = 1~2, y = 0~3; When m = -1, the molecular formula is M x N y H nx-3y x = 1~3, y = 0~1.

4. The method according to claim 1, characterized in that, The inactive atmosphere is selected from at least one of helium, neon, and argon.

5. The method according to claim 1, characterized in that, The molar ratio of the alkali metal to the ammonia is 1:1 to 10.

6. The method according to claim 1, characterized in that, The catalyst accounts for 50% to 90% of the bulk material.

7. The method according to claim 1, characterized in that, In step a, the conditions for ball milling are: rotation speed 150~300 rpm, time 1~24h.

8. The method according to claim 1, characterized in that, In step b, the decomposition conditions are: space velocity of the inactive atmosphere of 10000 ml / g / h - 60000 ml / g / h.