A method for converting nitrogen gas to ammonia gas by a metal hydride

Abstract

The application discloses a method for converting nitrogen into ammonia by metal hydride, which comprises the following steps: stirring a magnesium-based hydrogen storage material MgH2, a composite magnesium-based hydrogen storage material and an active alumina supported catalyst under an argon atmosphere, so that the MgH2 and the composite magnesium-based hydrogen storage material are adsorbed into the pore structure of the active alumina supported catalyst, and a supported catalyst adsorbing the MgH2 and the composite magnesium-based hydrogen storage material is obtained; and reacting nitrogen with the supported catalyst adsorbing the MgH2 and the composite magnesium-based hydrogen storage material at 400-600 DEG C to obtain NH3 gas. The conversion efficiency is high, the required reaction condition is not harsh, and the reaction can be carried out only under high temperature and normal pressure, so that the purpose of saving and emission reduction is achieved.

Description

Technical Field

[0001] This invention belongs to the field of ammonia preparation technology, specifically relating to a method for converting nitrogen into ammonia through metal hydrides. Background Technology

[0002] Currently, the main methods for synthesizing ammonia on the market are as follows: The Haber-Bosch process is the most common ammonia synthesis method. It is carried out at high temperature (approximately 450°C) and high pressure (approximately 200 to 300 atmospheres). In this process, hydrogen and nitrogen react in the presence of an iron catalyst to produce ammonia. Although this is an efficient method, it requires a large amount of energy to maintain the high temperature and high pressure conditions. Gas-phase ammonia synthesis is another ammonia synthesis method, usually carried out at even higher temperatures and pressures, approximately 600°C and 200 to 400 atmospheres. This process uses a graphite catalyst, which has even more stringent reaction conditions. High-temperature electrolysis is a method of preparing ammonia using electrolysis. This method involves electrolyzing nitrogen in a solution at high temperature (approximately 700–1000°C), causing it to combine with hydrogen atoms to form ammonia.

[0003] The main shortcomings and deficiencies of existing ammonia production technologies are as follows: Energy consumption: Traditional ammonia production methods require high temperature and high pressure conditions, which consume a large amount of energy. Reactions under high temperature conditions require a significant amount of electricity to heat the reactor, and under high pressure conditions, even more electricity is needed to maintain the pressure. Therefore, this is a significant energy consumption problem. Environmental issues: Traditional ammonia synthesis methods are accompanied by high carbon emissions, which have a negative impact on the environment. Reactions under high temperature and high pressure conditions usually require large amounts of natural gas or other fossil fuels, leading to increased carbon dioxide emissions and exacerbating the greenhouse effect. Catalyst issues: Existing catalysts are usually based on metals such as iron and molybdenum, which require high temperatures to operate effectively. Furthermore, they are prone to poisoning and need frequent replacement, increasing production costs. Hydrogen production: Hydrogen production is one of the key steps in the ammonia production process. Currently, most hydrogen is produced by steam reforming or gasification of natural gas, which not only requires a large amount of energy but also relies on limited fossil fuel resources. Summary of the Invention

[0004] To overcome the problems in the prior art, the purpose of this invention is to provide a method for converting nitrogen into ammonia through metal hydrides, which can convert nitrogen into ammonia with high conversion efficiency.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for converting nitrogen gas into ammonia gas via a metal hydride includes the following steps:

[0007] Magnesium-based hydrogen storage material MgH2, composite magnesium-based hydrogen storage material and active alumina supported catalyst are stirred under argon atmosphere to allow MgH2 and composite magnesium-based hydrogen storage material to be adsorbed into the pore structure of active alumina supported catalyst, thus obtaining a supported catalyst that adsorbs MgH2 and composite magnesium-based hydrogen storage material.

[0008] Ammonia is obtained by reacting nitrogen with a supported catalyst that adsorbs MgH2 and a composite magnesium-based hydrogen storage material at 400–600 °C.

[0009] Furthermore, the reaction time is 3–24 hours.

[0010] Furthermore, the stirring time is 8–12 hours.

[0011] Furthermore, the mass ratio of magnesium-based hydrogen storage material MgH2, composite magnesium-based hydrogen storage material, and activated alumina-supported catalyst is 1:1:2.

[0012] Furthermore, the magnesium-based hydrogen storage material MgH2 is prepared by the following process: placing Mg powder in a hydrogen atmosphere and carrying out a hydrogenation reaction at 300-600℃ for 3-24 hours to obtain the magnesium-based hydrogen storage material MgH2.

[0013] Furthermore, the Mg powder is placed in a hydrogen atmosphere with a hydrogen pressure of 1.5–4.5 MPa.

[0014] Furthermore, Mg powder and transition metal powder are mixed evenly under a nitrogen atmosphere, and then hydrogenated at 300–600°C for 3–24 hours under a hydrogen atmosphere to obtain a composite magnesium-based hydrogen storage material.

[0015] Furthermore, the transition metal powder is Fe.

[0016] Furthermore, the particle size of both Mg powder and transition metal powder is no greater than 325 mesh.

[0017] Furthermore, transition metals account for 10% to 50% of the total mass of Mg powder and transition metal powder.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] This invention provides a method for converting nitrogen into ammonia via metal hydrides. Magnesium-based hydrogen storage material MgH2, a composite magnesium-based hydrogen storage material, and an activated alumina-supported catalyst are stirred, causing MgH2 and the composite magnesium-based hydrogen storage material to be adsorbed into the pore structure of the activated alumina-supported catalyst. Then, they react with nitrogen at high temperature to generate ammonia, thus increasing reaction efficiency. This invention achieves a one-step nitrogen-to-ammonia conversion, which, compared to current mainstream ammonia production methods, requires less stringent reaction conditions, only requiring high temperature and normal pressure, thus achieving energy conservation and emission reduction. The remaining solids after the reaction can be recycled. The generated magnesium nitride (Mg3N2) is an important inorganic compound with wide applications, including the preparation of special ceramic materials and the manufacture of foaming agents for special alloys in various industrial fields. Attached Figure Description

[0020] Figure 1 This is a single-process flow diagram of the ammonia gasification reaction to produce ammonia as described in Comparative Example 1 of the present invention.

[0021] Figure 2 This is a single-process flow diagram of ammonia production via ammonia vaporization reaction according to the present invention.

[0022] Figure 3 This is a flow chart of the cyclic process of the present invention;

[0023] Figure 4 This is a graph showing the volume content of NH3, H2, and N2 under different cycles of the ammonia gasification reaction in Comparative Example 1 of the present invention.

[0024] Figure 5 The graph shows the volume content of NH3, H2, and N2 under different cycles of the ammonia gasification reaction in Example 1 of the present invention.

[0025] Figure 6 The graph shows the volume content of NH3, H2, and N2 under different cycles of the ammonia gasification reaction in Example 2 of the present invention.

[0026] In the diagram: 1-First reactor, 2-Agitator, 3-Second reactor, 4-Vacuum ball mill jar, 5-Planetary ball mill. Detailed Implementation

[0027] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0028] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples can be purchased directly from the market.

[0029] This invention discloses a method for converting nitrogen gas into ammonia gas via a metal hydride, comprising the following steps:

[0030] (1) In the first reactor 1 containing metallic Mg powder, the air in the first reactor 1 is first replaced with Ar gas at a pressure of 0.1-0.3 MPa. Then H2 is introduced to make the pressure 1.5-4.5 MPa. The metallic Mg powder is hydrogenated at 300-600℃ for 3-24 hours. The first reactor 1 is then cooled to obtain magnesium-based hydrogen storage material MgH2.

[0031] First, Mg powder and transition metal powder are added to the same vacuum ball mill jar 4. The air in the vacuum ball mill jar 4 is extracted using a vacuum pump. Then, Ar gas with a purity ≥99% is introduced into the vacuum ball mill jar 4 at a pressure of 0.1–0.3 MPa. Introducing Ar gas can prevent Mg powder and transition metal powder from oxidizing and burning with air. After that, the ball mill jar is ball milled in a planetary ball mill 5 at a speed of 310–450 rpm for 3–24 hours with a ball-to-material ratio (mass ratio) of 10:1. H2 with a purity ≥99% is introduced into the reactor containing the ball-milled transition metal and Mg powder, and the pressure is increased to 1.5–4.5 MPa. The metal powder is hydrogenated at 300–600℃ for 3–24 hours. The reactor is then cooled to obtain a composite magnesium-based hydrogen storage material.

[0032] In this invention, gas H2, metallic Mg powder, and transition metal powder Fe can all be purchased directly from the market. The particle size of metallic Mg powder and transition metal powder is no larger than the size corresponding to 325 mesh. Transition metal Fe accounts for 10% to 50% of the total mass of metallic Mg powder and transition metal powder. The transition metal plays a catalytic role in the hydrogenation reaction, and most of it forms an alloy. If too much is used, agglomeration is likely to occur.

[0033] (2) Magnesium-based hydrogen storage material MgH2, composite magnesium-based hydrogen storage material, and activated alumina supported catalyst are placed into mixer 2. Air is extracted from mixer 2 using a vacuum pump. Then, Ar gas with a purity ≥99% is introduced into a vacuum ball mill jar 4 at a pressure of 0.1–0.3 MPa. The mixing time is set to 8–12 hours to ensure that MgH2 and composite magnesium-based hydrogen storage material are adsorbed into the pore structure of the activated alumina supported catalyst, thus obtaining a supported catalyst adsorbed with MgH2 and composite magnesium-based hydrogen storage material. The activated alumina supported catalyst can be purchased directly from the market (manufacturer: Henan Shengwei Environmental Protection Technology Co., Ltd.).

[0034] The composite magnesium-based hydrogen storage material in this invention consists of MgH2 and magnesium iron hydride. The reason for adding magnesium-based hydrogen storage material MgH2 in this step is to increase the hydrogen content in the reaction in step (3).

[0035] (3) Nitrogen gas is reacted with a supported catalyst that has adsorbed MgH2 and composite magnesium hydrogen storage material at 400-600℃ for 3-24h to obtain NH3 gas.

[0036] The remaining material after the reaction is carried out at least five more times in accordance with step (2) above.

[0037] Comparative Example 1

[0038] according to Figure 1 The process shown is the ammonia vaporization of nitrogen gas, as detailed below.

[0039] 40g of Mg powder with a purity ≥99% and a particle size of 300 mesh is weighed and placed in the first reactor 1. H2 with a purity ≥99% is first replaced with Ar gas at a pressure of 0.1 MPa and then introduced into the first reactor 1 until the pressure of H2 introduced is 1.6 MPa. The reactor is heated to 400℃ and reacted for 12 hours to complete the hydrogenation reaction. Finally, the first reactor 1 is cooled to 30℃ to obtain the product MgH2.

[0040] The product MgH2 in the first reactor 1 and the active alumina supported catalyst were put into the stirrer 2, and Ar gas was introduced into the stirrer 2 for mixing. The mixing time was set to 8-12 h to obtain the catalyst supported on which MgH2 was adsorbed.

[0041] The product from the first stirrer 2, containing MgH2-supported catalyst and nitrogen, is mixed and placed into the second reactor 3. The pressure in the second reactor is one standard atmosphere. The mixture is heated to 600°C and reacted for 24 hours. Afterward, the second reactor 3 is cooled to 30°C. The gas obtained at the outlet is the final NH3 product. The remaining material at the bottom of the second reactor 3 is then processed as follows... Figure 3 The cycle shown is repeated six times.

[0042] After six cycles, 80% of MgH remains, which is converted into Mg3N2 and can be reused in various industrial fields, such as preparing special ceramic materials and manufacturing foaming agents for special alloys. The remaining MgH can also be recycled for new reactions.

[0043] The initial gas composition was 4% NH3, 8% H2, and 56% N2 by volume. The NH3 content decreased sequentially with each cycle. (Specific details are as follows...) Figure 4 As shown.

[0044] Example 1

[0045] according to Figure 2 The process shown involves the ammonia conversion of nitrogen gas, and the specific steps are as follows:

[0046] In the first reactor 1 containing metallic Mg powder, the air in the first reactor 1 is first replaced with Ar gas at a pressure of 0.2 MPa. Then, H2 is introduced to make the pressure 3 MPa. The metallic Mg powder is hydrogenated at 450°C for 15 hours. The first reactor 1 is then cooled to obtain magnesium-based hydrogen storage material MgH2.

[0047] Weigh 36g of Mg powder, then add 4g of Fe powder (325 mesh). The Fe powder content in the total metal powder is 10wt.%. Place the mixture into a vacuum ball mill jar 4. Use a vacuum pump to remove air from the vacuum ball mill jar 4. Ar purity ≥99%. Fill the vacuum ball mill jar 4 with Ar gas until the pressure is 0.1MPa. Place the vacuum ball mill jar 4 into a planetary ball mill 55 for co-ball milling for 12 hours at a speed of 400 rpm. Then, place the co-milled product into the first reactor 1. H2 purity ≥99%. Fill the first reactor 1 until the pressure is 2MPa. Heat to 450℃ and carry out a hydrogenation reaction for 12 hours. Cool the first reactor 1 to 30℃ to form a MgFeH composite magnesium-based hydrogen storage material.

[0048] Magnesium-based hydrogen storage material MgH2, the product MgFeH composite magnesium-based hydrogen storage material from the first reactor 1, and the activated alumina-supported catalyst were placed into a mixer 2, and Ar gas was introduced into the mixer 2 for mixing. The Ar gas pressure was 0.2 MPa, and the mixing time was set to 8–12 h to obtain a catalyst supported on which MgFeH composite magnesium-based hydrogen storage material was adsorbed. The mass ratio of magnesium-based hydrogen storage material MgH2, MgFeH composite magnesium-based hydrogen storage material, and activated alumina-supported catalyst was 1:1:2.

[0049] The product from mixer 2, containing a catalyst supported on a MgFeH composite magnesium-based hydrogen storage material, is mixed with nitrogen and placed into the second reactor 3. The pressure in the second reactor is one standard atmosphere. The mixture is heated to 600°C and reacted for 24 hours. Afterward, the second reactor 3 is cooled to 30°C. The gas obtained at the outlet is the final NH3 product. The remaining material at the bottom of the second reactor 3 is then processed as follows... Figure 3 The cycle reaction is repeated six times. The remaining material is hydrogenated with hydrogen in the first reactor 1, and then the remaining material after hydrogenation is reacted with nitrogen in the second reactor 3 to produce ammonia.

[0050] After six cycles, 80% of MgH2 remains, which is converted into Mg3N2 and can be reused in various industrial fields, such as preparing special ceramic materials and manufacturing foaming agents for special alloys. The remaining MgH2 can also be recycled for new reactions.

[0051] The initial gas composition was 25% NH3, 6% H2, and 69% N2 by volume. The NH3 content decreased sequentially with each cycle. (Specific details are as follows...) Figure 5 As shown.

[0052] Example 2

[0053] In the first reactor 1 containing metallic Mg powder, the air in the first reactor 1 is first replaced with Ar gas at a pressure of 0.1 MPa. Then, H2 is introduced to make the pressure 1.5 MPa. The metallic Mg powder is hydrogenated at 500°C for 14 hours. The first reactor 1 is then cooled to obtain magnesium-based hydrogen storage material MgH2.

[0054] Weigh 36g of metallic Mg powder, then add metallic Fe powder (325 mesh). The metallic Fe powder accounts for 50wt.% of the total mass of metallic Mg powder and transition metal powder. Place the mixture into a vacuum ball mill jar 4. Use a vacuum pump to remove air from the vacuum ball mill jar 4. Ar gas with a purity ≥99% is added. The pressure in the vacuum ball mill jar 4 is increased to 0.2MPa. The vacuum ball mill jar 4 is then placed in a planetary ball mill 55 for co-ball milling for 3 hours at a speed of 310 rpm. The co-milled product is then placed into the first reactor 1. H2 with a purity ≥99% is added to the first reactor 1. The pressure in the first reactor 1 is increased to 4MPa. The reactor is heated to 300℃ and subjected to a hydrogenation reaction for 24 hours. The first reactor 1 is then cooled to 30℃ to form a MgFeH composite magnesium-based hydrogen storage material.

[0055] Magnesium-based hydrogen storage material MgH2, the product MgFeH composite magnesium-based hydrogen storage material from the first reactor 1, and the activated alumina-supported catalyst were placed into a mixer 2. Ar gas with a purity ≥99% was introduced into the mixer 2 for mixing at a pressure of 0.3 MPa for 8 hours, resulting in a catalyst supported on which the MgFeH composite magnesium-based hydrogen storage material was adsorbed. The mass ratio of magnesium-based hydrogen storage material MgH2, MgFeH composite magnesium-based hydrogen storage material, and activated alumina-supported catalyst was 1:1:2.

[0056] The product from mixer 2, containing a catalyst supported on a MgFeH composite magnesium-based hydrogen storage material, is mixed with nitrogen and placed into the second reactor 3. The pressure in the second reactor is one standard atmosphere. The mixture is heated to 400°C and reacted for 24 hours. Afterward, the second reactor 3 is cooled to 30°C. The gas obtained at the outlet is the final NH3 product. The remaining material at the bottom of the second reactor 3 is then processed as follows... Figure 3 The cycle reaction is repeated six times. The remaining material is hydrogenated with hydrogen in the first reactor 1, and then the remaining material after the hydrogenation reaction is reacted with nitrogen in the second reactor 3 to produce ammonia.

[0057] The initial gas composition was 76% NH3, 5% H2, and 19% N2 by volume. The NH3 content decreased sequentially with each cycle. (Specific details are as follows...) Figure 6 As shown.

[0058] Example 3

[0059] according to Figure 2 The process shown involves the ammonia conversion of nitrogen gas, and the specific steps are as follows:

[0060] In the first reactor 1 containing metallic Mg powder, the air in the first reactor 1 is first replaced with Ar gas at a pressure of 0.1 MPa. Then, H2 is introduced to make the pressure 4.5 MPa. The metallic Mg powder is hydrogenated at 300°C for 24 hours. The first reactor 1 is then cooled to obtain magnesium-based hydrogen storage material MgH2.

[0061] Weigh 36g of Mg powder, then add Fe powder (325 mesh). The Fe powder content in the total metal powder is 50wt.%. Place the mixture into a vacuum ball mill jar 4. Use a vacuum pump to remove air from the vacuum ball mill jar 4. Ar purity ≥99%. Fill the vacuum ball mill jar 4 with Ar gas until the pressure reaches 0.3MPa. Place the vacuum ball mill jar 4 into a planetary ball mill 55 for co-ball milling for 24 hours at a speed of 310 rpm. Then, place the co-milled product into the first reactor 1. H2 purity ≥99%. Fill the first reactor 1 until the pressure reaches 1.5MPa. Heat to 300℃ and carry out a hydrogenation reaction for 24 hours. Cool the first reactor 1 to 30℃ to form a MgFeH composite magnesium-based hydrogen storage material.

[0062] Magnesium-based hydrogen storage material MgH2, the product MgFeH composite magnesium-based hydrogen storage material from the first reactor 1, and the activated alumina-supported catalyst were placed into a mixer 2, and Ar gas was introduced into the mixer 2 for mixing at a pressure of 0.1 MPa for 12 hours to obtain a catalyst supported on which the MgFeH composite magnesium-based hydrogen storage material was adsorbed. The mass ratio of magnesium-based hydrogen storage material MgH2, MgFeH composite magnesium-based hydrogen storage material, and activated alumina-supported catalyst was 1:1:2.

[0063] The product from mixer 2, containing a catalyst supported on a MgFeH composite magnesium-based hydrogen storage material, is mixed with nitrogen and placed into the second reactor 3. The pressure in the second reactor is one standard atmosphere. The mixture is heated to 400°C and reacted for 24 hours. Afterward, the second reactor 3 is cooled to 30°C. The gas obtained at the outlet is the final NH3 product. The remaining material at the bottom of the second reactor 3 is then processed as follows... Figure 3The cycle reaction is repeated six times. The remaining material is hydrogenated with hydrogen in the first reactor 1, and then the remaining material after hydrogenation is reacted with nitrogen in the second reactor 3 to produce ammonia.

[0064] Example 4

[0065] according to Figure 2 The process shown involves the ammonia conversion of nitrogen gas, and the specific steps are as follows:

[0066] In the first reactor 1 containing metallic Mg powder, the air in the first reactor 1 is first replaced with Ar gas at a pressure of 0.2 MPa. Then, H2 is introduced to make the pressure 1.5 MPa. The metallic Mg powder is hydrogenated at 500°C for 15 hours. The first reactor 1 is then cooled to obtain magnesium-based hydrogen storage material MgH2.

[0067] Weigh 36g of Mg powder, then add Fe powder (325 mesh). The Fe powder content in the total metal powder is 20wt.%. Place the mixture into a vacuum ball mill jar 4. Use a vacuum pump to remove air from the vacuum ball mill jar 4. Ar purity ≥99%. Fill the vacuum ball mill jar 4 with Ar gas until the pressure reaches 0.2MPa. Place the vacuum ball mill jar 4 into a planetary ball mill 55 for co-ball milling for 3 hours at a speed of 450 rpm. Then, place the co-milled product into the first reactor 1. H2 purity ≥99%. Fill the first reactor 1 until the pressure reaches 4.5MPa. Heat to 600℃ and perform a hydrogenation reaction for 3 hours. Cool the first reactor 1 to 30℃ to form a MgFeH composite magnesium-based hydrogen storage material.

[0068] Magnesium-based hydrogen storage material MgH2, the product MgFeH composite magnesium-based hydrogen storage material from the first reactor 1, and the activated alumina-supported catalyst were placed into a mixer 2, and Ar gas was introduced into the mixer 2 for mixing at a pressure of 0.3 MPa for 8 hours, resulting in a catalyst supported on which MgFeH composite magnesium-based hydrogen storage material was adsorbed. The mass ratio of magnesium-based hydrogen storage material MgH2, MgFeH composite magnesium-based hydrogen storage material, and activated alumina-supported catalyst was 1:1:2.

[0069] The product from mixer 2, containing a catalyst supported on a MgFeH composite magnesium-based hydrogen storage material, is mixed with nitrogen and placed into the second reactor 3. The pressure in the second reactor is one standard atmosphere. The mixture is heated to 600°C and reacted for 3 hours. Afterward, the second reactor 3 is cooled to 30°C. The gas obtained at the outlet is the final NH3 product. The remaining material at the bottom of the second reactor 3 is then processed as follows... Figure 3 The cycle reaction is repeated six times. The remaining material is hydrogenated with hydrogen in the first reactor 1, and then the remaining material after hydrogenation is reacted with nitrogen in the second reactor 3 to produce ammonia.

[0070] Example 5

[0071] according to Figure 2 The process shown involves the ammonia conversion of nitrogen gas, and the specific steps are as follows:

[0072] In the first reactor 1 containing metallic Mg powder, the air in the first reactor 1 is first replaced with Ar gas at a pressure of 0.3 MPa. Then, H2 is introduced to make the pressure 3 MPa. The metallic Mg powder is hydrogenated at 600°C for 3 hours. The first reactor 1 is then cooled to obtain magnesium-based hydrogen storage material MgH2.

[0073] Weigh 36g of Mg powder, then add Fe powder (325 mesh). The Fe powder content in the total metal powder is 30wt.%. Place the mixture into a vacuum ball mill jar 4. Use a vacuum pump to remove air from the vacuum ball mill jar 4. Ar purity ≥99%. Fill the vacuum ball mill jar 4 with Ar gas until the pressure is 0.1MPa. Place the vacuum ball mill jar 4 into a planetary ball mill 55 for co-ball milling for 10 hours at a speed of 280 rpm. Then, place the co-milled product into the first reactor 1. H2 purity ≥99%. Fill the first reactor 1 until the pressure is 3MPa. Heat to 450℃ and carry out a hydrogenation reaction for 12 hours. Cool the first reactor 1 to 30℃ to form a MgFeH composite magnesium-based hydrogen storage material.

[0074] Magnesium-based hydrogen storage material MgH2, the product MgFeH composite magnesium-based hydrogen storage material from the first reactor 1, and the activated alumina-supported catalyst were placed into a mixer 2, and Ar gas was introduced into the mixer 2 for mixing at a pressure of 0.2 MPa for 10 hours to obtain a catalyst supported on which the MgFeH composite magnesium-based hydrogen storage material was adsorbed. The mass ratio of magnesium-based hydrogen storage material MgH2, MgFeH composite magnesium-based hydrogen storage material, and activated alumina-supported catalyst was 1:1:2.

[0075] The product from mixer 2, containing a catalyst supported on a MgFeH composite magnesium-based hydrogen storage material, is mixed with nitrogen and placed into the second reactor 3. The pressure in the second reactor is one standard atmosphere. The mixture is heated to 500°C and reacted for 15 hours. Afterward, the second reactor 3 is cooled to 30°C. The gas obtained at the outlet is the final NH3 product. The remaining material at the bottom of the second reactor 3 is then processed as follows... Figure 3 The cycle reaction is repeated six times. The remaining material is hydrogenated with hydrogen in the first reactor 1, and then the remaining material after hydrogenation is reacted with nitrogen in the second reactor 3 to produce ammonia.

[0076] From the comparison between Comparative Example 1 and Examples 1-4 of the present invention, it can be seen that the reason for using magnesium-based hydrogen storage material MgH2 is to increase the hydrogen content in the reaction in step (3), thereby increasing the volume content of ammonia in the final gas.

[0077] The above description is only of the preferred embodiment of the present invention and should not be construed as limiting the scope of the claims. The present invention is not limited to the above embodiments, and variations in its specific structure are permitted. All variations made within the scope of the independent claims of the present invention are also within the scope of protection of the present invention.

[0078] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

Claims

1. A method for converting nitrogen gas into ammonia gas via a metal hydride, characterized in that, Includes the following steps: Magnesium-based hydrogen storage material MgH2, composite magnesium-based hydrogen storage material and active alumina supported catalyst are stirred under argon atmosphere to allow MgH2 and composite magnesium-based hydrogen storage material to be adsorbed into the pore structure of active alumina supported catalyst, thus obtaining a supported catalyst that adsorbs MgH2 and composite magnesium-based hydrogen storage material. Ammonia is obtained by reacting nitrogen with a supported catalyst that adsorbs MgH2 and a composite magnesium-based hydrogen storage material at 400–600 °C. Mg powder and transition metal powder are mixed evenly under a nitrogen atmosphere, and then hydrogenated at 300-600℃ for 3-24 hours under a hydrogen atmosphere to obtain a composite magnesium-based hydrogen storage material. The transition metal powder is Fe.

2. The method for converting nitrogen gas into ammonia gas via metal hydride according to claim 1, characterized in that, The reaction time is 3 to 24 hours.

3. The method for converting nitrogen gas into ammonia gas via metal hydride according to claim 1, characterized in that, The stirring time is 8 to 12 hours.

4. The method for converting nitrogen gas into ammonia gas via metal hydride according to claim 1, characterized in that, The mass ratio of magnesium-based hydrogen storage material MgH2, composite magnesium-based hydrogen storage material, and activated alumina-supported catalyst is 1:1:

2.

5. The method for converting nitrogen gas into ammonia gas via metal hydride according to claim 1, characterized in that, Magnesium-based hydrogen storage material MgH2 is prepared by the following process: placing Mg powder in a hydrogen atmosphere and carrying out a hydrogenation reaction at 300-600℃ for 3-24 hours to obtain magnesium-based hydrogen storage material MgH2.

6. The method for converting nitrogen gas into ammonia gas via metal hydride according to claim 5, characterized in that, Place the Mg powder in a hydrogen atmosphere with a hydrogen pressure of 1.5–4.5 MPa.

7. The method for converting nitrogen gas into ammonia gas via metal hydride according to claim 1, characterized in that, The particle size of both Mg powder and transition metal powder is no greater than 325 mesh.

8. The method for converting nitrogen gas into ammonia gas via metal hydride according to claim 1, characterized in that, Transition metals account for 10% to 50% of the total mass of Mg powder and transition metal powder.

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