Method and device for synthesizing ammonia through plasma coupling thermocatalysis

Abstract

The invention relates to the technical field of ammonia synthesis, in particular to a plasma coupling thermocatalytic ammonia synthesis method and device. The plasma coupling thermocatalytic synthesis ammonia method comprises the following steps: in a plasma environment, raw material gas is contacted with an iron-based catalyst or a ruthenium-based catalyst for thermocatalytic synthesis ammonia reaction to generate ammonia gas; the raw material gas is mixed gas of nitrogen and hydrogen. Through the synergistic effect of plasma and thermocatalysis, catalyst activation and ammonia synthesis reaction are synchronously carried out, the reaction temperature and energy consumption are remarkably reduced, the ammonia synthesis efficiency and the catalyst stability are improved, and good industrial application prospects are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of synthetic ammonia, in particular to a method and device for synthesizing ammonia by plasma coupling thermal catalysis. BACKGROUND

[0002] As an important chemical raw material and potential clean energy carrier, the efficient and low-carbon synthesis technology of ammonia (NH3) has become a global research hotspot. The traditional Haber-Bosch process for synthesizing ammonia requires harsh conditions of high temperature and high pressure, whether using conventional iron-based catalysts (400-500°C, 15-25MPa) or more active ruthenium-based catalysts (such as 350-450°C, 10-15MPa), in order to overcome the large reaction energy barrier. This thermodynamic limitation directly results in high energy consumption (about 30 GJ per ton of ammonia), accompanied by huge equipment investment and considerable carbon dioxide emissions (about 1.6 tons of CO2 per ton of ammonia).

[0003] Compared with the traditional H-B process and the thermal plasma Birkeland-Eyde process, the low-temperature plasma technology has lower energy consumption and more relaxed reaction conditions (the theoretical energy consumption of nitrogen fixation is at least 2.5 times lower than that of the H-B process). The high-energy particles generated by the low-temperature plasma technology not only can effectively activate N2 in the air, but also can induce rapid lattice distortion and chemical bond rupture on the surface of the metal catalyst when they contact the surface of the metal catalyst, forming a metastable state structure with high reactivity. Therefore, by innovatively designing an efficient reactor structure, the low-temperature plasma technology can be deeply coupled with the traditional catalytic process, which can solve the problems of difficulty in in-situ construction of metastable catalysts under reaction conditions and significant increase in activation energy barrier caused by high N2 bond energy, and provide the possibility for developing a green ammonia production technology that can be distributed for production. SUMMARY

[0004] Based on this, the purpose of the present application is to provide a method and device for synthesizing ammonia by plasma coupling thermal catalysis, which realizes the simultaneous performance of catalyst activation and ammonia synthesis reaction through the synergistic effect of plasma and thermal catalysis, significantly reduces the reaction temperature and energy consumption, improves the synthesis efficiency of ammonia and the stability of the catalyst, and has good industrial application prospect.

[0005] To achieve the above purpose, the technical scheme adopted by the present application is as follows: The present application provides a method for synthesizing ammonia by plasma coupling thermal catalysis, which comprises the following steps: contacting raw gas and iron-based catalyst or ruthenium-based catalyst in a plasma environment to perform a thermal catalytic ammonia synthesis reaction to generate ammonia gas; the raw gas is a mixture of nitrogen and hydrogen.

[0006] This invention utilizes low-temperature plasma to simultaneously activate the catalyst and feed gas. After plasma treatment, the gas contacts the activated catalyst to carry out a highly efficient ammonia synthesis reaction, achieving simultaneous catalyst activation and ammonia synthesis. This significantly reduces reaction temperature and energy consumption, improves ammonia synthesis efficiency and catalyst stability, and solves bottleneck problems such as the difficulty of in-situ construction of metastable catalysts under reaction conditions and the significant increase in activation energy barrier caused by the high N2 bond energy. This provides a possibility for the development of distributed production technology for green ammonia preparation.

[0007] As a further improvement to the above-mentioned scheme of the present invention, the temperature of the thermocatalytic ammonia synthesis reaction is 300-400℃.

[0008] As a further improvement to the above-mentioned scheme of the present invention, the volume ratio of nitrogen to hydrogen in the raw material gas is 1:1-3.

[0009] The present invention also provides a plasma-coupled thermocatalytic ammonia synthesis apparatus, which employs the plasma-coupled thermocatalytic ammonia synthesis method as described above, comprising: A raw material gas supply unit for supplying raw material gas, which is a mixture of nitrogen and hydrogen; Plasma generating unit, which is used to generate plasma jets; A thermocatalytic ammonia synthesis unit, internally filled with an iron-based catalyst or a ruthenium-based catalyst, is configured to receive the feed gas and the plasma jet to conduct a thermocatalytic ammonia synthesis reaction on the iron-based catalyst or the ruthenium-based catalyst in a plasma environment to generate ammonia gas; and A gas collection unit is connected to the thermocatalytic ammonia synthesis unit and is used to collect the mixed gas within the thermocatalytic ammonia synthesis unit.

[0010] As a further improvement to the above-mentioned scheme of the present invention, the thermocatalytic ammonia synthesis unit includes a reactor and a quartz tube disposed in the reactor. A tubular catalyst bed is disposed in the quartz tube and filled with an iron-based catalyst or a ruthenium-based catalyst.

[0011] As a further improvement of the above-mentioned solution of the present invention, a metal mesh for supporting iron-based catalyst or ruthenium-based catalyst is provided at the bottom of the tubular catalyst bed, and the filling height of the iron-based catalyst or ruthenium-based catalyst accounts for 30%-40% of the total height of the tubular catalyst bed.

[0012] As a further improvement to the above-mentioned solution of the present invention, the raw material gas supply unit includes a hydrogen source, a nitrogen source and a preheating furnace. The hydrogen source and the nitrogen source are respectively connected to the preheating furnace through connecting pipe one and connecting pipe two. A hydrogen flow meter and a nitrogen flow meter are respectively installed on connecting pipe one and connecting pipe two. The preheating furnace is used to heat the introduced hydrogen and nitrogen. The preheating furnace is connected to the tubular catalyst bed through connecting pipe three.

[0013] As a further improvement to the above-mentioned solution of the present invention, the connecting pipe is wrapped with a heat tracing cable.

[0014] As a further improvement to the above-mentioned solution of the present invention, the preheating furnace is used to heat the introduced hydrogen and nitrogen gas to 150-300°C.

[0015] As a further improvement to the above-described solution of the present invention, the plasma generating unit includes a plasma reactor and a stainless steel connector. The plasma reactor is mounted on the stainless steel connector, and the stainless steel connector is connected to the tubular catalyst bed.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention relates to a method for simultaneously activating a catalyst and feed gas using low-temperature plasma to achieve efficient ammonia synthesis. By directly contacting the plasma-treated gas with the in-situ activated catalyst, the catalyst activation and ammonia synthesis reaction are carried out simultaneously. This invention significantly reduces the reaction temperature and energy consumption, and improves nitrogen activation efficiency, ammonia synthesis rate, and catalyst stability by leveraging the synergistic effect of plasma and thermal catalysis.

[0017] The core of this invention lies in the close coupling of low-temperature plasma with the thermocatalytic process. By utilizing plasma to activate the catalyst at low temperatures, the activation temperature and operating energy consumption of the thermocatalytic reaction are significantly reduced. Compared with the traditional Haber-Bosch process, the reaction temperature is reduced by approximately 50-150°C, the pressure is reduced by more than an order of magnitude, and energy consumption is significantly reduced.

[0018] In terms of device design, a structure is adopted in which the plasma generator is directly connected to the tubular catalyst bed, which effectively promotes the activity of active species (such as excited-state nitrogen molecules, nitrogen atoms, NH4+). x The transfer of free radicals (and other substances) from the plasma region to the catalyst surface enhances the synergistic effect of activation and reaction processes.

[0019] The present invention features a compact process and flexible operation, providing a practical and feasible technical path for developing distributed, small-scale green ammonia production technology. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a plasma-coupled thermocatalytic ammonia synthesis device provided in an embodiment of the present invention.

[0021] Reference numerals: 1. Nitrogen source; 2. Nitrogen flow meter; 3. Preheating furnace; 4. Heating tape; 5. Plasma reactor; 6. Cathode; 7. Stainless steel connector; 8. Anode; 9. Reactor; 10. Metal mesh; 11. Quartz tube; 12. Plasma; 13. Tubular catalyst bed; 14. Iron-based catalyst or ruthenium-based catalyst; 15. Pressure valve; 16. High-voltage power supply; 17. Oscilloscope; 18. Collection container; 19. Hydrogen source; 20. Hydrogen flow meter. Detailed Implementation

[0022] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present 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 more thorough and complete understanding of the disclosure of the present invention.

[0023] 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.

[0024] Reference Figure 1 This embodiment provides a plasma-coupled thermocatalytic ammonia synthesis device, which includes a raw material gas supply unit, a plasma generation unit, a thermocatalytic ammonia synthesis unit, and a gas collection unit.

[0025] The raw material gas supply unit supplies raw material gas, which is a mixture of nitrogen and hydrogen. In this embodiment, the raw material gas supply unit includes a nitrogen source 1, a hydrogen source 19, and a preheating furnace 3. The hydrogen source 19 and the nitrogen source 1 are connected to the preheating furnace via connecting pipe one and connecting pipe two, respectively. A nitrogen flow meter 2 and a hydrogen flow meter 20 are respectively installed on connecting pipe one and connecting pipe two. By adjusting the hydrogen flow meter 20 and the nitrogen flow meter 2, the volume ratio of nitrogen to hydrogen in the gas entering the preheating furnace 3 is maintained at 1:1-3. The preheating furnace 3 heats the incoming hydrogen and nitrogen gas to 150-300°C to reduce the heat load of the gas entering the thermocatalytic ammonia synthesis unit and improve overall energy efficiency. In this embodiment, the preheating furnace 3 is a straight-tube structure with an electric heater as an auxiliary heat source. The gas enters the straight tube and is heated to the set temperature by direct electric heating. Of course, in other embodiments, the preheating furnace 3 can also be a spiral tube to preheat nitrogen and hydrogen more evenly and fully. The heated raw material gas is output through the connecting pipe 3. To avoid heat loss, the connecting pipe 3 is wrapped with a heat tracing cable 4. The heat tracing cable 4 heats the connecting pipe 3 to ensure that the temperature of the raw material gas is stable within a certain range.

[0026] The plasma generating unit is used to generate a plasma jet. In this embodiment, the plasma generating unit includes a plasma reactor 5 and a stainless steel connector 7. The plasma reactor 5 is a dielectric barrier discharge (DBD) reactor, and it is mounted on the stainless steel connector 7. The plasma reactor 5 has a cathode 6 and an anode 8. The cathode 6 is located at the top of the plasma reactor 5, and the anode 8 is directly connected to the stainless steel connector 7. The cathode 6 and anode 8 are respectively connected to the positive and negative terminals of an external AC high-voltage power supply (voltage 15-30kV, frequency 5-20kHz). The high-voltage power supply 16 is connected to an oscilloscope 17, which monitors the discharge state.

[0027] The thermocatalytic ammonia synthesis unit is internally filled with an iron-based catalyst or a ruthenium-based catalyst 14. The unit is configured to receive feed gas and a plasma jet, allowing ammonia gas to be generated through a thermocatalytic ammonia synthesis reaction on the iron-based catalyst or ruthenium-based catalyst 14 under a plasma environment. In this embodiment, the thermocatalytic ammonia synthesis unit includes a reactor 9 and a quartz tube 11 disposed within the reactor 9. The reactor 9 has a box-type structure, with a length of 25-30 cm, a width of 25-30 cm, and a height of 35-40 cm. The temperature inside the reactor 9 is controlled at 300-400℃. The diameter of the quartz tube 11 is 3.5-6 cm. A tubular catalyst bed 13 is disposed inside the quartz tube 11, which serves as insulation and high-temperature resistance. The tubular catalyst bed 13 has a tubular structure with a diameter of 3-4 cm and a height of 30-35 cm. A metal mesh 10 is provided at the bottom of the tubular catalyst bed 13 to support the iron-based catalyst or ruthenium-based catalyst 14. The filling height of the iron-based catalyst or ruthenium-based catalyst 14 accounts for 30%-40% of the total height of the tubular catalyst bed. This appropriate filling amount ensures sufficient gas-solid contact area and reaction residence time while avoiding excessive pressure drop. A certain gap is left between the tubular catalyst bed 13 and the outer quartz tube 11, with a perimeter distance of 0.5-2 cm on one side. This distance allows gas to flow around the tubular catalyst bed 13, forming a backflow effect, which prolongs the residence time of the reactants and thus improves the conversion rate. Connecting pipe 3 is directly connected to the tubular catalyst bed 13, and the stainless steel connector 7 is also directly threaded to the tubular catalyst bed 13.

[0028] The gas collection unit is connected to the thermocatalytic ammonia synthesis unit and is used to collect the mixed gas within the unit. In this embodiment, the gas collection unit includes a connecting pipe 4 and a collection container 18. One end of the connecting pipe 4 is connected to the reactor 9, and the other end is connected to the quartz tube 11. A pressure relief valve 15 is installed on the connecting pipe 4 to maintain the system pressure at 0.5-1.5 MPa. The collection container 18 is used to collect the mixed gas of nitrogen, hydrogen, and ammonia from the thermocatalytic ammonia synthesis unit for subsequent ammonia yield calculation.

[0029] Based on the above-described plasma-coupled thermocatalytic ammonia synthesis apparatus, this embodiment also provides a plasma-coupled thermocatalytic ammonia synthesis method, which includes the following steps: (1) The tubular catalyst bed 13 is filled with an iron-based catalyst or a ruthenium-based catalyst 14, and the filling height accounts for 30%-40% of the total height of the tubular catalyst bed 13; (2) Open the valves of nitrogen source 1 and hydrogen source 19, and adjust nitrogen flow meter 2 and hydrogen flow meter 20 so that nitrogen and hydrogen enter the preheating furnace 3 at a volume ratio of 1:1-3. After the raw material gas is preheated to 150-300℃, it is introduced into the tubular catalyst bed 13 through the third connecting pipe. (3) At the same time, the plasma reactor 5 generates low-temperature plasma 12 under the action of high-voltage power supply 16. The low-temperature plasma 12 activates the catalyst and raw material gas in the tubular catalyst bed 13 in situ and partially generates active nitrogen species. After plasma treatment, the gas comes into contact with the activated catalyst and carries out a high-efficiency ammonia synthesis reaction at 300-400℃ and normal pressure. (4) The gas after the reaction is pressured by the pressure relief valve 15 and finally collected by the collection container 18.

[0030] The invention will now be further illustrated with two specific implementation examples.

[0031] Example 1 (1) A commercial molten iron catalyst is filled into the tubular catalyst bed 13 with a filling amount of 500 mg and a filling height of 35% of the total height of the tubular catalyst bed 13.

[0032] (2) Open the valves of nitrogen source 1 and hydrogen source 19, and adjust nitrogen flow meter 2 and hydrogen flow meter 20 so that nitrogen and hydrogen enter the preheating furnace 3 at a volume ratio of 1:3. After the raw material gas is preheated to 200°C, it is introduced into the tubular catalyst bed 13 through the third connecting pipe. (3) At the same time, the plasma reactor generates low-temperature plasma under the action of high-voltage power supply 16 (voltage 20kV, frequency 10kHz). The low-temperature plasma activates the catalyst and raw material gas in the tubular catalyst bed 13 in situ and partially generates active nitrogen species. After plasma treatment, the gas comes into contact with the activated catalyst and carries out a high-efficiency ammonia synthesis reaction at 300℃ and normal pressure. (4) The gas after the reaction is pressured by the pressure relief valve 15 and finally collected by the collection container 18.

[0033] Testing showed that the nitrogen conversion rate in this embodiment reached 0.45%, and the ammonia synthesis selectivity was higher than 99%, demonstrating excellent reaction performance. At 300 °C and atmospheric pressure, the ammonia yield of the commercial molten iron catalyst was 4.5 mmol NH3 g.cat -1 h -1 The volume percentage of ammonia in the mixed gas collected by the gas collection unit is 8.5%.

[0034] Example 2 The difference between this embodiment and Embodiment 1 is that the tubular catalyst bed 13 in this embodiment is filled with Ru / AC catalyst.

[0035] Testing showed that the nitrogen conversion rate in this embodiment reached 2.2%, and the ammonia synthesis selectivity was higher than 99%, demonstrating excellent reaction performance. At 300 °C and atmospheric pressure, the ammonia yield of the Ru / AC catalyst was 22 mmol NH3 g. cat -1 h -1 The volume percentage of ammonia in the outlet mixed gas collected by the gas collection unit is 15.5%.

[0036] Under the same 500 mg catalyst and the same reaction conditions, the Ru / AC catalyst has a much higher ammonia yield than the conventional iron catalyst (about 5 times) and can achieve a higher outlet ammonia concentration, which clearly demonstrates the great advantage of ruthenium-based catalysts in terms of activity.

[0037] It should be noted that when a component is said to be "installed on" another component, it can be directly on the other component or it may be in a component that is centered on it. When a component is said to be "set on" another component, it can be directly set on the other component or it may also be in a component that is centered on it. When a component is said to be "fixed to" another component, it can be directly fixed to the other component or it may also be in a component that is centered on it.

[0038] 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 specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "or / and" as used herein includes any and all combinations of one or more of the associated listed items.

[0039] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0040] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A plasma-coupled thermocatalytic ammonia synthesis method, characterized in that, It includes the following steps: In a plasma environment, ammonia is generated by a thermocatalytic ammonia synthesis reaction in which the feed gas is contacted with an iron-based catalyst or a ruthenium-based catalyst; the feed gas is a mixture of nitrogen and hydrogen.

2. The plasma-coupled thermocatalytic ammonia synthesis method according to claim 1, characterized in that, The temperature for the thermocatalytic ammonia synthesis reaction is 300-400℃.

3. The plasma-coupled thermocatalytic ammonia synthesis method according to claim 1, characterized in that, In the raw material gas, the volume ratio of nitrogen to hydrogen is 1:1-3.

4. A plasma-coupled thermocatalytic ammonia synthesis apparatus, characterized in that, It employs the plasma-coupled thermocatalytic ammonia synthesis method as described in any one of claims 1-3, comprising: A raw material gas supply unit for supplying raw material gas, which is a mixture of nitrogen and hydrogen; Plasma generating unit, which is used to generate plasma jets; A thermocatalytic ammonia synthesis unit, internally filled with an iron-based catalyst or a ruthenium-based catalyst, is configured to receive the feed gas and the plasma jet to conduct a thermocatalytic ammonia synthesis reaction on the iron-based catalyst or the ruthenium-based catalyst in a plasma environment to generate ammonia gas; and A gas collection unit is connected to the thermocatalytic ammonia synthesis unit and is used to collect the mixed gas within the thermocatalytic ammonia synthesis unit.

5. The plasma-coupled thermocatalytic ammonia synthesis apparatus according to claim 4, characterized in that, The thermocatalytic ammonia synthesis unit includes a reactor and a quartz tube disposed inside the reactor. A tubular catalyst bed is disposed inside the quartz tube and is filled with an iron-based catalyst or a ruthenium-based catalyst.

6. The plasma-coupled thermocatalytic ammonia synthesis apparatus according to claim 5, characterized in that, The bottom of the tubular catalyst bed is equipped with a metal mesh for supporting the iron-based catalyst or the ruthenium-based catalyst. The filling height of the iron-based catalyst or the ruthenium-based catalyst accounts for 30%-40% of the total height of the tubular catalyst bed.

7. The plasma-coupled thermocatalytic ammonia synthesis apparatus according to claim 5, characterized in that, The feed gas supply unit includes a hydrogen source, a nitrogen source, and a preheating furnace. The hydrogen source and the nitrogen source are connected to the preheating furnace through connecting pipe one and connecting pipe two, respectively. Hydrogen flow meter and nitrogen flow meter are respectively installed on connecting pipe one and connecting pipe two. The preheating furnace is used to heat the introduced hydrogen and nitrogen. The preheating furnace is connected to the tubular catalyst bed through connecting pipe three.

8. The plasma-coupled thermocatalytic ammonia synthesis apparatus according to claim 7, characterized in that, The connecting pipe is wrapped with a heat tracing cable on all three sides.

9. The plasma-coupled thermocatalytic ammonia synthesis apparatus according to claim 7, characterized in that, The preheating furnace is used to heat the introduced hydrogen and nitrogen gas to 150-300℃.

10. The plasma-coupled thermocatalytic ammonia synthesis apparatus according to claim 5, characterized in that, The plasma generating unit includes a plasma reactor and a stainless steel connector. The plasma reactor is mounted on the stainless steel connector, which is connected to the tubular catalyst bed.

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