A method for nitrogen-hydrogen ammonia synthesis based on gas-liquid interface

Abstract

This invention provides a method for synthesizing ammonia from nitrogen and hydrogen based on a gas-liquid interface. The method includes the following steps: mixing nitrogen and hydrogen to form a mixed gas; forming microbubbles in a liquid; and generating ammonia from the nitrogen-hydrogen mixed gas within the microbubbles through a free radical reaction at the gas-liquid interface. This invention provides a method for directly synthesizing ammonia from nitrogen and hydrogen using nitrogen and hydrogen as reaction sources, directly synthesizing ammonia at room temperature and pressure using free radicals at the gas-liquid interface of microbubbles. No catalyst is required, the reaction process is simple, the reaction conditions are mild, and it is easy to operate, achieving a completely green, catalytic-free, room-temperature and atmospheric-pressure synthesis of ammonia.

Description

Technical Field

[0001] This invention belongs to the field of ammonia synthesis technology, and relates to a method for nitrogen-hydrogen ammonia synthesis, particularly a method for nitrogen-hydrogen ammonia synthesis based on the gas-liquid interface. Background Technology

[0002] Ammonia is the world's second-largest produced chemical and an important chemical raw material, playing a vital role in the synthesis of fertilizers, explosives, fibers, and plastics. Furthermore, its high volumetric energy density and easy liquefaction properties make it a promising candidate for development as an important green fuel.

[0003] Currently, the industrial synthesis of ammonia involves using hydrogen and nitrogen as raw materials in the presence of a catalyst at a concentration of 1×10⁻⁶. 7 -6×10 7 Achieving this at 400-600℃ requires high-temperature and high-pressure conditions, placing demanding requirements on equipment, consuming significant energy, and resulting in high production costs. CN116081640A discloses a method and apparatus for synthesizing green ammonia. This method involves mixing nitrogen gas and water vapor at a certain pressure, and then conducting a photothermal coupled catalytic reaction under photothermal coupled catalyst, temperature, and light conditions to produce green ammonia. This method reduces the temperature and pressure required for ammonia synthesis, but still requires multiple components and high-cost precious metals as catalysts.

[0004] Research has revealed abundant free radicals at micro- and nano-scale curved gas-liquid interfaces, such as spontaneously formed hydroxyl radicals on the surfaces of micro- and nano-bubbles (J. Phys. Chem. B 2007, 111, 1343-1347) and micro-droplets (Proc Natl Acad Sci USA 2022, 119:e2200991119). Utilizing these abundant free radicals at the gas-liquid interface holds promise for the synthesis and application of ammonia.

[0005] CN116924432A discloses a method for preparing green ammonia based on a confined catalytic reaction at the gas-liquid interface of water and nitrogen microdroplets. This method involves mixing water and a regulator, selected from nanomaterials, conductive polymers, or inorganic salts with redox properties. The aqueous solution is then used to generate microdroplets, and a nitrogen atmosphere is created at the spray tip of the microdroplets, causing the water and microdroplets to react and generate ammonia. However, this method still requires the addition of a regulator containing noble metals for auxiliary conversion.

[0006] Therefore, there is an urgent need to develop alternative ammonia production processes based on green and low-cost methods. Summary of the Invention

[0007] The purpose of this invention is to provide a method for nitrogen-hydrogen ammonia synthesis based on the gas-liquid interface, which utilizes gas-liquid interface free radicals to reduce the activation energy of the ammonia synthesis reaction and achieve direct nitrogen-hydrogen ammonia synthesis at room temperature and pressure.

[0008] To achieve this objective, the present invention employs the following technical solution:

[0009] This invention provides a method for synthesizing ammonia from nitrogen and hydrogen based on a gas-liquid interface, the method comprising the following steps:

[0010] Nitrogen and hydrogen are mixed to form a mixed gas. This mixed gas is then used to form micro- and nano-bubbles in a liquid. The nitrogen and hydrogen in the micro- and nano-bubbles react with free radicals at the gas-liquid interface to generate ammonia.

[0011] The method for synthesizing ammonia from nitrogen and hydrogen provided by this invention uses nitrogen and hydrogen as reaction sources. It utilizes hydroxyl radicals at the gas-liquid interface in micro-nano bubbles to convert into nitrogen and hydrogen atoms or corresponding free radicals, directly synthesizing ammonia at room temperature and pressure. Compared to microdroplets, micro-nano bubbles have extremely high internal pressure and a large internal surface area, resulting in good conversion effect and high efficiency. Furthermore, it does not require precious metals or other heterogeneous catalysts, reducing the use of catalysts. The reaction process is simple, the reaction conditions are mild, and it is easy to operate, achieving a completely green, catalytic-free, room temperature and pressure synthesis of ammonia.

[0012] Preferably, the size of the micro-nano bubbles is 0.01-10μm, for example, it can be 0.01μm, 0.05μm, 0.1μm, 0.5μm, 1μm, 2μm, 4μm, 5μm, 6μm, 8μm or 10μm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0013] Preferably, the micro-nano bubbles are formed using a micro-nano bubble generator.

[0014] Preferably, in the micro-nano bubble generator, the operating pressure of the mixed gas is 0.1-1 MPa, for example, it can be 0.1 MPa, 0.2 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.8 MPa or 1 MPa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0015] Preferably, in the micro-nano bubble generator, the flow rate of the mixed gas is 10-100 mL / min, for example, it can be 10 mL / min, 20 mL / min, 40 mL / min, 50 mL / min, 60 mL / min, 80 mL / min or 100 mL / min, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0016] Preferably, the method further includes: mixing the liquid that forms micro-nano bubbles with an acid solution to convert ammonia into ammonium ions.

[0017] Preferably, the acid solution includes hydrochloric acid.

[0018] Preferably, the mass fraction of the acid solution is 0.01-0.1%, for example, it can be 0.01%, 0.02%, 0.04%, 0.05%, 0.06%, 0.08% or 0.1%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0019] Preferably, the ammonia detection method includes any one or a combination of at least two of the following: salicylic acid-hypochlorite spectrophotometry, Nessler's reagent spectrophotometry, titration, or ammonia gas sensor method.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The method for direct synthesis of ammonia from nitrogen and hydrogen provided by this invention uses nitrogen and hydrogen as reaction sources and utilizes free radicals at the gas-liquid interface of micro-nano bubbles to directly synthesize ammonia at room temperature and pressure without any catalyst. The reaction process is simple, the reaction conditions are mild, and it is easy to operate, enabling the complete green, catalytic-free, room temperature and pressure synthesis of ammonia. Attached Figure Description

[0022] Figure 1 The bar chart shows the ammonia content in the liquid after the reaction, as provided in the examples and comparative examples. Detailed Implementation

[0023] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0024] Example 1

[0025] This embodiment provides a method for synthesizing ammonia from nitrogen and hydrogen based on a gas-liquid interface, the method comprising the following steps:

[0026] (1) Take ultrapure water into a beaker, introduce a mixture of nitrogen and hydrogen into a micro-nano bubble generator, turn on the micro-nano bubble generator, the operating pressure of the mixed gas is 0.35MPa, the flow rate is 100mL / min, and continuously circulate to generate bubbles. The size of the micro-nano bubbles is about 100nm. The nitrogen and hydrogen in the micro-nano bubbles generate ammonia through the free radical reaction at the gas-liquid interface.

[0027] (2) Prepare hydrochloric acid with a mass fraction of 0.1% and add it to the micro-nano bubble water after the reaction to improve the stability of ammonia nitrogen in the water and convert it into ammonium ions.

[0028] The micro-nano bubble generator used is a commercial micro-nano bubble generator.

[0029] Comparative Example 1

[0030] This comparative example provides water that does not contain micro- or nano-bubbles, and the method for preparing the water without micro- or nano-bubbles is as follows:

[0031] (1) Take ultrapure water into a beaker, let it stand, and then take a sample.

[0032] (2) Prepare hydrochloric acid with a mass fraction of 0.1% and add it to the sampled water.

[0033] Comparative Example 2

[0034] This comparative example provides argon-gas micro-nano bubble water, and the preparation method of the argon-gas micro-nano bubbles is as follows:

[0035] (1) Take ultrapure water and put it into a beaker. Pass argon gas into the micro-nano bubble generator, turn on the micro-nano bubble generator, and continuously generate bubbles to obtain argon gas micro-nano bubble water.

[0036] (2) Prepare hydrochloric acid with a mass fraction of 0.1% and add it to argon micro-nano bubble water.

[0037] Comparative Example 3

[0038] This comparative example provides a method for nitrogen-hydrogen ammonia synthesis based on the gas-liquid interface. Compared with Example 1, in step (1), a capillary tube is used to introduce mixed gas into ultrapure water to form bubbles. The size of the bubbles is 1-6 mm. All other steps are the same as in Example 1.

[0039] The ammonia nitrogen content in the reaction liquids provided in the examples and comparative examples was determined using salicylic acid-hypochlorite spectrophotometry.

[0040] The ammonia nitrogen content of the water after the reaction obtained in Example 1, Comparative Example 1, and Comparative Example 2 is as follows: Figure 1 As shown, the method provided by this invention enables the direct synthesis of ammonia from nitrogen and hydrogen using free radicals on the surface of micro- and nano-bubbles, without the need for a catalyst. In Comparative Example 3, millimeter-sized bubbles cannot exist stably in solution, free radicals cannot form on their surface, and the direct reaction between nitrogen and hydrogen cannot be achieved.

[0041] In summary, the method for direct nitrogen-hydrogen ammonia synthesis provided by this invention uses nitrogen and hydrogen as reaction sources and utilizes free radicals at the gas-liquid interface of micro-nano bubbles to directly synthesize ammonia at room temperature and pressure without any catalyst. The reaction process is simple, the reaction conditions are mild, and it is easy to operate, enabling a completely green, catalytic-free, room temperature and pressure ammonia synthesis.

[0042] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for the synthesis of ammonia by the nitrogen-hydrogen process based on a gas-liquid interface, characterized in that, The method comprises the following steps: nitrogen and hydrogen are mixed to form a mixed gas, the mixed gas is used to form micro-nano bubbles in a liquid, and the nitrogen and hydrogen in the micro-nano bubbles are reacted by free radicals at the gas-liquid interface to generate ammonia; the size of the micro-nano bubbles is 0.01-8 μm.

2. The method of claim 1, wherein, The micro-nano bubbles are formed by a micro-nano bubble generator.

3. The method of claim 2, wherein, In the micro-nano bubble generator, the operating pressure of the mixed gas is 0.1-1 MPa.

4. The method of claim 2, wherein, In the micro-nano bubble generator, the flow rate of the mixed gas is 10-100 mL / min.

5. The method of claim 1, wherein, The liquid comprises water.

6. The method of claim 1, wherein, The method further comprises mixing the reacted liquid with an acid liquid to convert the ammonia into ammonium ions.

7. The method of claim 6, wherein, The acid liquid comprises hydrochloric acid.

8. The method of claim 6, wherein, The mass fraction of the acid liquid is 0.01-0.1%.

9. The method according to any one of claims 1 to 8, characterized in that, The detection method of the ammonia comprises any one or a combination of at least two of salicylic acid-hypochlorite spectrophotometry, Nash reagent spectrophotometry, titration, or an ammonia gas sensitive sensor method.

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