A green ammonia preparation method based on water and nitrogen microdroplet gas-liquid interface confined catalytic reaction

Abstract

The present disclosure provides a green ammonia preparation method based on water and nitrogen microdroplet gas-liquid interface confined catalytic reaction, relating to the field of green energy technology. The method comprises: mixing water and an adjusting agent to obtain an aqueous solution, wherein the adjusting agent is selected from nanomaterials, magnetic nanoparticles, conductive polymers and inorganic salts; inputting the aqueous solution into a microdroplet generating device to generate microdroplets, the size of the microdroplets being less than or equal to 10 microns, and hydrogen radicals and hydroxyl radicals being spontaneously generated by means of a strong electric field in the gas-liquid interface double electric layer of the microdroplets. In a nitrogen atmosphere, a large number of hydrogen radicals and nitrogen in the gas phase undergo radical chain reactions at the gas-liquid interface to generate ammonia, and the hydroxyl radicals combine to generate hydrogen peroxide. The preparation process of the method is simple, green and environmentally friendly, and is not limited by catalysts. It only needs to provide an adjusting agent with good electron conductivity to meet the requirements of different production processes. It helps to meet the environmental protection requirements and strategic needs of hydrogen energy storage under the background of "double carbon".

Description

Technical Field

[0001] This disclosure relates to the field of green energy technology, and in particular to a method for preparing green ammonia based on a confined catalytic reaction at the gas-liquid interface of water and nitrogen microdroplets. Background Technology

[0002] Ammonia, as an important chemical raw material, is widely used in fertilizers, pharmaceuticals, energy, and other fields. Driven by the "dual-carbon" vision, ammonia is considered a promising "energy carrier" and "hydrogen carrier." Breakthroughs in its green synthesis technology are crucial for the long-term development of hydrogen energy. Currently, industrial ammonia synthesis mainly employs the Haber-Bosch process, which uses Fe-based catalysts and operates under reaction conditions of 350-550°C and 100-300 atm. This process is characterized by high energy consumption, heavy pollution, and demanding equipment and process requirements. Studies show that the Haber-Bosch process releases approximately 670 million tons of CO2 annually, accounting for about 2.4% of global carbon emissions, creating significant pressure for emission reduction. Therefore, a new ammonia synthesis technology is urgently needed to address the excessive carbon emissions in existing ammonia synthesis processes and ultimately achieve "zero-carbon" ammonia production, i.e., green ammonia production.

[0003] In recent years, with the development of the hydrogen energy industry, a modified Habere-Bosch method has emerged as a promising technology for producing green ammonia by reacting green hydrogen (obtained through water electrolysis) with nitrogen. This approach, compared to the gray and blue ammonia produced in traditional industries, relies heavily on renewable energy to achieve green hydrogen-ammonia fusion. Furthermore, ammonia, as a liquid organic hydrogen storage carrier, plays a crucial role in the subsequent hydrogen industry chain (production, storage, transportation, and application). However, the preparation of green ammonia involves two processes: the production of green hydrogen through water electrolysis and the production of green ammonia through the reaction of nitrogen with green hydrogen. While this process depends on the widespread availability and cost reduction of renewable energy sources such as wind, solar, and electricity, its cost remains limited by the cost per kilowatt-hour of green hydrogen, thus increasing the cost of the final green ammonia and hindering its large-scale development.

[0004] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] This disclosure provides a method for preparing green ammonia based on the confined catalytic reaction of water and nitrogen microdroplets at the gas-liquid interface. It mainly utilizes microdroplet reaction and gas-liquid interface confined catalysis, with nitrogen and water as direct reactants. Through the free radical chain reaction initiated by the confined catalysis of the microdroplet gas-liquid interface, a new method for the direct preparation of green ammonia is realized, providing a new idea and method for achieving "zero carbon" technology in ammonia preparation.

[0006] This invention discloses a method for preparing green ammonia based on a confined catalytic reaction at the gas-liquid interface of water and nitrogen microdroplets, comprising:

[0007] S1, water and a regulator are mixed to obtain an aqueous solution, wherein the regulator is selected from one or more of nanomaterials, conductive polymers, and inorganic salts with redox properties;

[0008] S2, Input the aqueous solution into the microdroplet generating device to generate microdroplets, wherein the size of the microdroplets is less than or equal to 10 μm;

[0009] S3, a nitrogen atmosphere is formed at the spray end of the microdroplet so that water and nitrogen in the microdroplet can generate ammonia through a spontaneous free radical reaction at the gas-liquid interface;

[0010] S4, Detect or collect the ammonia. Specifically, the generated ammonia may be ammonia gas in gaseous form or ammonia water in liquid form.

[0011] Specifically, in this invention, the essence lies in the combination of nitrogen gas and hydrogen free radicals (·H) generated at the gas-liquid interface of microdroplets to form (·HNN), which lowers the activation energy and reaction barrier of the nitrogen gas reaction. At the same time, hydroxyl free radicals in the system form hydrogen peroxide free radicals through a self-consistent combination process, as detailed below:

[0012]

[0013] The overall reaction equation is as follows:

[0014] .

[0015] In one exemplary embodiment of this disclosure, the microdroplet generating device is selected from one of an electrospray device, a pneumatic spray device, and an ultrasonic atomizing device.

[0016] In an exemplary embodiment of this disclosure, the microdroplet generating device is an electrospray device, which has an electrospray probe. The aqueous solution is injected into the electrospray probe at a flow rate of 5-150 μL / min. The inner diameter of the electrospray probe is 5-150 μm, and a bias voltage of 3-7 kV is applied to generate microdroplets with a size of less than 10 μm. Nitrogen gas is applied to the spray end of the electrospray probe to form a nitrogen atmosphere.

[0017] In one exemplary embodiment of this disclosure, the electrospray device has a plurality of electrospray probes.

[0018] In an exemplary embodiment of this disclosure, the microdroplet generating device is a pneumatic spraying device, which includes an inner tube and an outer tube nested outside the inner tube. The end of the inner tube forms a spray end. Nitrogen gas is introduced into the outer tube as a sheath gas. The aqueous solution is injected into the inner tube and atomized by the sheath gas to form the microdroplets. The sheath gas flows to the spray end to form the nitrogen atmosphere.

[0019] In one exemplary embodiment of this disclosure, the aqueous solution is injected into the inner tube at a flow rate of 5-150 μL / min, the nitrogen gas used as a sheath gas is at a pressure of 60-120 psi, and the generated microdroplets have a flight speed of 65-110 m / s.

[0020] In one exemplary embodiment of this disclosure, the inorganic salt is selected from one or more of chloroauric acid, palladium chloride, and chloroauric acid-palladium chloride; the nanomaterial is selected from one or more of gold nanoparticles, palladium-coated gold nanoparticles, gold-palladium nanocomposites, and magnetic nanoparticles; the conductive polymer is selected from C 60 One or more of -(OH)n, alkalized polyaniline-gold nanoparticle complex and acidified polyaniline-gold nanoparticle complex, wherein the modifier has or can generate an electron conduction effect in the microdroplet reaction.

[0021] In one exemplary embodiment of this disclosure, when the regulator is an inorganic salt, the concentration of the inorganic salt in the aqueous solution is 50~1000 μg / mL; when the regulator is a nanomaterial or a conductive polymer, the concentration of the nanomaterial or conductive polymer in the aqueous solution is 10 μg / mL. -5 ~10 -1 mg / mL.

[0022] In one exemplary embodiment of this disclosure, the step of collecting the ammonia includes: the step of detecting or collecting the ammonia includes:

[0023] A mass spectrometer is installed at the spray end of the microdroplet generating device. The mass spectrometer receives the product generated at the spray end and performs mass spectrometry detection. The product is ammonia or amide. An organic acid is added to the aqueous solution in step S1. The amide is generated by the reaction of organic acid and ammonia.

[0024] or,

[0025] A collection device is provided at the spray end of the microdroplet generating device. The collection device has a sealed collection chamber, and the spray end is placed in the collection chamber.

[0026] In one exemplary embodiment of this disclosure, the collecting cavity is further provided with a conductive plate and / or a heating device, the conductive plate being grounded or connected to a high voltage to remove the charge accumulated in the collecting cavity.

[0027] In one exemplary embodiment of this disclosure, the collecting chamber is connected to an inlet pipe and an outlet pipe, nitrogen gas is introduced into the inlet pipe, and the generated ammonia gas is output through the outlet pipe.

[0028] The beneficial effects of the green ammonia preparation method based on microdroplet reaction in this disclosure are:

[0029] The green ammonia preparation method of this disclosure obtains microdroplets with a diameter of less than 10 μm through a microdroplet generation device. These microdroplets exhibit a "confined effect" at the microscopic scale, possessing unique physicochemical properties such as high specific surface area, abundant charge density, and a strong electric field in the dielectric bilayer. As a microreactor, the microdroplets function based on the unique gas-liquid interface effect and the strong electric field at the gas-liquid interface (10 μm). 7 V / cm), causing water molecules to ionize (H + ), forming hydrogen radicals (·H, H) + +e - →·H), further recombination occurs between ·H radicals (2·H→H2). However, due to the relatively short half-life of hydrogen radicals (·H) (<10), further recombination occurs between ·H radicals. -9 s), which will transiently reverse to form hydrogen ions (·He - →H + This process is controlled by electrons (e.g., electrons). - Whether electrons are transferred depends on the excellent electron transport properties of conductive metallic materials, nanomaterials, and inorganic salts. Electrons generated at the interface (e) can be transferred... - The hydrogen radicals (·H, H) are transferred to the forward direction of the reaction, causing the reaction to proceed in the forward direction. + +e - →·H) accumulates at the gas-liquid interface and recombines with N2 in the gas phase under the influence of a strong electric field at the gas-liquid interface to generate a transition state (NNH·), initiating a free radical chain reaction to ultimately generate NH3. This realizes a new method for preparing green ammonia based on the synergistic effect of water microdroplets, nitrogen, and an electronically capable regulator. Simultaneously, the combination of hydroxyl radicals (·OH) generates H2O2 (2·OH→ H2O2).

[0030] This method for preparing green ammonia differs from current methods that use green electricity to produce hydrogen, followed by a modified HaberBosch process involving hydrogen and ammonia. It directly uses water and nitrogen as raw materials, leveraging the gas-liquid interface confinement effect in the microdroplet reaction to generate ammonia. Furthermore, a regulator significantly improves the ammonia generation efficiency (683.9 mmol / gh). Therefore, this method is environmentally friendly, energy-efficient, and allows for the direct production of ammonia from water and nitrogen under "zero-carbon" conditions, opening a new avenue for the preparation and production of green ammonia.

[0031] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this disclosure and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a flowchart of a method for preparing green ammonia based on a confined catalytic reaction at the gas-liquid interface of water and nitrogen microdroplets, according to an embodiment of this disclosure.

[0034] Figure 2 This is a schematic diagram of the structure of a pneumatic atomizing device according to an embodiment of the present disclosure;

[0035] Figure 3 This is a schematic diagram of the structure of a receiving device and a mass spectrometer according to an embodiment of the present disclosure;

[0036] Figure 4 This is a schematic diagram of a collection device according to an embodiment of the present disclosure;

[0037] Figure 5 The mass spectra of microdroplets generated from the fumaric acid aqueous solution of Example 1 of this disclosure in negative ion and positive ion modes;

[0038] Figure 6 The mass spectra of microdroplets generated from aqueous solutions a~d in Example 1 of this disclosure in positive ion mode;

[0039] Figure 7 The mass spectra are obtained from the microdroplets generated by the negative control, pure water, and aqueous solutions a to d in Example 2 of this disclosure. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions in the embodiments of this disclosure will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0041] The method for preparing green ammonia based on microdroplet reaction according to the embodiments of this disclosure will be described in detail below.

[0042] Please see Figure 1 This invention provides a method for preparing green ammonia based on a confined catalytic reaction at the gas-liquid interface of water and nitrogen microdroplets, comprising:

[0043] S1, water and a regulator are mixed to obtain an aqueous solution, wherein the regulator is selected from one or more of nanomaterials, conductive polymers, and inorganic salts with redox properties;

[0044] S2, Input the aqueous solution into the microdroplet generating device to generate microdroplets, wherein the size of the microdroplets is less than or equal to 10 μm;

[0045] S3, a nitrogen atmosphere is formed at the spray end of the microdroplet so that water and nitrogen in the microdroplet can generate ammonia through a spontaneous free radical reaction at the gas-liquid interface;

[0046] S4, detect or collect the ammonia.

[0047] Microdroplet reactions primarily rely on droplets with a size of 10 μm or less generated under external forces as microreactors. Unlike bulk reactions, this approach challenges the traditional understanding of water as a solvent at the macroscopic physicochemical scale, endowing it with unique physicochemical properties such as increased specific surface area, strong interfacial electric field, reduced reaction barrier, and special redox characteristics. Compared to the macroscopic scale, microdroplets under microscopic conditions, and gas-liquid interfaces at the interfacial scale (i.e., confined conditions), possess a strong dielectric bilayer, with electric field strengths reaching 10⁻⁶. 7 V / cm can induce HER (hydrogen evolution reaction) and OER (oxygen evolution reaction) reactions at the microscopic scale. Depending on the electrochemical catalytic reaction characteristics, under the action of special dielectric materials, the catalytic effect at the gas-liquid interface of microdroplets can be enhanced, thus forming a gas-liquid interface confined catalytic reaction system. The green ammonia preparation method provided in this embodiment uses microdroplets as microreactors. Through specific regulators, electronic conductors are introduced into the microreactors, selectively adjusting the dielectric bilayer thickness or conductivity to improve electron stripping efficiency. This promotes the combination of nitrogen gas with hydrogen free radicals generated at the gas-liquid interface of the microdroplets, thereby converting them into ammonia gas.

[0048] In one embodiment of this disclosure, in step S1, the inorganic salt is selected from one or more of chloroauric acid (HAuCl4), palladium chloride (PdCl2), and chloroauric acid-palladium chloride (HAuCl4-PdCl2). Through the redox effect of the above-mentioned inorganic salt, the gas-liquid interface properties of the microdroplets are improved, thereby increasing the ammonia generation efficiency.

[0049] In one embodiment of this disclosure, the nanomaterial is selected from one or more of Au NPs, palladium-coated gold nanoparticles (Au@PdNPs), gold-palladium alloy nanoparticles (AuPd alloy NPs), and magnetic nanoparticles. Specifically, the magnetic nanoparticles may be, for example, iron(III) oxide nanoparticles (Fe3O4NPs).

[0050] In one embodiment of this disclosure, the conductive polymer is selected from C 60 One or more of the following nanoparticles are used: -(OH)n, alkalized polyaniline-gold nanoparticle composite (PANI@AuNPs-NaOH), and acidified polyaniline-gold nanoparticle composite (PANI@AuNPs-HCl). The addition of these nanoparticles can enhance the interfacial effect, adjust the dielectric bilayer thickness, alter the electron stripping efficiency, and promote ammonia formation.

[0051] Specifically, C 60 -(OH)n is C 60 Polyhydroxy compounds, also known as fullerols, are readily soluble in water due to the presence of multiple hydroxyl groups in their molecules. For example, they can be synthesized using amine catalysis. 60 -(OH)n. ANI@AuNPs-NaOH and PANI@AuNPs-HCl can be prepared according to existing techniques. For example, in one embodiment, 3.5 mL of 55 nm gold nanoparticles are dispersed in 1.5 mL of 2 mM aniline and 0.25 mL of 40 mM SDS solution, vortexed for 1 min, and then 1.5 mL of 2 mM (NH4)2S2O8-HCl aqueous solution is added. The mixture is vortexed for 10 s and reacted at room temperature for 12 h. The aniline in the system polymerizes and coats the surface of the gold nanoparticles, forming a polymer-coated gold nanoparticle aqueous solution with a thickness of approximately 16 nm. After centrifugation and rinsing, PANI@AuNPs-HCl is obtained. PANI@AuNPs-HCl particles are then dispersed in an aqueous solution, 2 M NaOH solution is added, the pH of the solution is adjusted to 11.4, and the solution is magnetically stirred for 2 h to obtain PANI@AuNPs-NaOH.

[0052] In one embodiment of this disclosure, when the regulator is an inorganic salt, the concentration of the inorganic salt in the aqueous solution is 50-1000 μg / mL; when the regulator is a nanomaterial or a conductive polymer, the concentration of the nanomaterial or conductive polymer in the aqueous solution is 10 μg / mL. -5 ~10 -1 mg / mL. Different concentrations of regulator result in different concentrations of ammonia being produced in the reaction system.

[0053] Furthermore, in one embodiment of this disclosure, the regulator is HAuCl4, PdCl2, or HAuCl4-PdCl2, and the concentration of the regulator in the aqueous solution is 500 μg / mL. At this concentration, the ammonia yield reaches 98 mmol / gh or higher. Further, when the regulator is AuPd alloy NPs, the concentration of AuPd alloy NPs in the aqueous solution is 10... -2 At a concentration of mg / mL, the ammonia yield reached over 683.9 mmol / gh. Inorganic salts and nanoalloys differed in ammonia production efficiency, with nanoalloys exhibiting superior ammonia production capacity. This is partly due to the excellent electron stripping properties of nanoalloys, which promote the generation of hydrogen radicals (·H) and their reaction with nitrogen at the gas-liquid interface. On the other hand, inorganic salts act as sacrificial agents, resulting in redox reactions between hydrogen radicals and the inorganic salt system (3·H + HAuCl4 → Au + 4HCl, 2·H + PdCl2 → Pd + 2HCl), which consume hydrogen radicals (·H).

[0054] In one embodiment of this disclosure, the microdroplet generating device is selected from an electrospray device, a pneumatic spray device, and an ultrasonic atomizing device. The specific construction of the electrospray device, pneumatic spray device, and ultrasonic atomizing device can be found in the prior art; for example, the specific construction of the electrospray device can be referred to the electrospray device in mass spectrometry analysis technology.

[0055] In one specific embodiment, the electrospray device may include a syringe, a connector, an electrospray probe, and a high-voltage power supply. The connector may be, for example, a two-way connector, through which the syringe and the electrospray probe are connected. The aqueous solution enters the electrospray probe through the syringe. An electric field is generated at the spray tip of the electrospray probe by the high-voltage power supply, causing the aqueous solution to atomize into microdroplets based on electrohydrodynamic principles. Nitrogen gas is applied around the periphery of the electrospray probe to induce a free radical chain reaction between the nitrogen gas and the microdroplets, generating ammonia gas or ammonia solution.

[0056] Furthermore, the electrospray device can be equipped with multiple parallel electrospray probes, which can be connected to the same injector, or each electrospray probe can be connected to a separate injector. The use of multiple parallel electrospray probes effectively improves ammonia production efficiency.

[0057] Furthermore, the aqueous solution is injected into the electrospray probe at a flow rate of 5-150 μL / min; the inner diameter of the electrospray probe is 5-150 μm, and the applied bias voltage is 3-7 kV to generate microdroplets smaller than 10 μm. Nitrogen gas is applied to the spray tip of the electrospray probe via a gas cylinder or similar device to create a nitrogen atmosphere, enabling a free radical chain reaction between nitrogen and microdroplets to generate ammonia or ammonia solution. Under these parameters, spatially, the generated microdroplets are smaller, and the aqueous solution per unit volume has a higher or higher specific surface area, increasing the probability of contact between nitrogen and the gas-liquid interface. Simultaneously, temporally, the reaction time between nitrogen and the microdroplet gas-liquid interface is prolonged. These spatial and temporal effects are beneficial in improving the rate and efficiency of ammonia generation from microdroplets.

[0058] In one specific embodiment, such as Figure 2 As shown, the pneumatic spray device 200 may include an inner tube 210 and an outer tube 220 nested outside the inner tube 210. The outer tube 220 is connected to a gas cylinder 230 for inputting sheath gas (nitrogen) at different pressures. One end of the inner tube 210 is connected to a syringe (not shown). The other end forms a spray end 240. Specifically, the inner diameter of the inner tube gradually decreases to form a spray end at the end. The aqueous solution enters the inner tube 210 through the syringe and forms microdroplets at the spray end under pneumatic atomization. Sheath gas flows to the spray end 240 to form the nitrogen atmosphere.

[0059] Furthermore, the flow rate of the aqueous solution injected into the inner tube is 5-150 μL / min, the pressure of nitrogen as the sheath gas is 60-120 psi, and the flight velocity of the generated microdroplets is 65-110 m / s. More preferably, the flight velocity of the generated microdroplets is 80-90 m / s. Under the above parameters, the ammonia generation rate is higher.

[0060] In one specific embodiment, the ultrasonic atomizing device includes a syringe, an ultrasonic generator, and a spray head. The ultrasonic generator produces ultrasonic oscillation wave energy, which atomizes the aqueous solution into microdroplets under the action of the ultrasonic oscillation wave energy. Nitrogen gas is output around the microdroplets through a device such as a gas cylinder to form a nitrogen atmosphere.

[0061] In one embodiment of this disclosure, in step S4, the generated ammonia gas or ammonia solution is detected. Specifically, the step of detecting the ammonia includes: setting a mass spectrometer at the spray end of the microdroplet generating device, the mass spectrometer receiving the product generated at the spray end of the microdroplet generating device, and performing mass spectrometry detection.

[0062] Specifically, in one embodiment, the product can be ammonia, which is received by a receiving device and then input into a mass spectrometer for detection. Figure 3 The diagram shows a sample apparatus for receiving and detecting ammonia. Figure 3 As shown, the receiving device 310 has a sealed receiving cavity 311 (in an air environment), and the spray end 321 of the microdroplet generating device (electrospray device or pneumatic device) extends into the receiving cavity 311. The receiving cavity 311 can be constructed, for example, using a round-bottom flask. The receiving cavity 311 has a transmission line 312 for delivering ammonia gas from the cavity to the mass spectrometer. A cooling cavity 330 is disposed outside the receiving cavity 311. The receiving cavity 311 is placed in the cooling cavity 330, which is filled with refrigerant to form a cold trap system for cooling and solidifying the water formed during the spraying process. The outlet line 212 delivers the generated ammonia gas to the mass spectrometer 340 for online detection.

[0063] Furthermore, in one embodiment of this disclosure, a refrigerant is provided outside the collection chamber to cool and solidify the water formed during the spraying process; the refrigerant is selected from one or more of liquid nitrogen, ice water, ice-containing brine, and ethylene glycol. By using a refrigerant, the influence of water in microdroplets on the mass spectrometry detector can be effectively removed during real-time, online mass spectrometry detection.

[0064] Specifically, in another embodiment, the product in the ammonia detection step can also be an amide. Specifically, for ease of detection, an organic acid can be added to the aqueous solution in step S1. The ammonia generated at the microdroplet gas-liquid interface with nitrogen reacts with the organic acid in the microdroplet to generate an amide compound. The amide compound is detected in positive ion mass spectrometry, thereby indirectly determining the ammonia in the system. For example, in one example, fumaric acid is added to the aqueous solution, and microdroplets are generated using a pneumatic nebulizer. The organic acid in the pneumatically nebulized microdroplets reacts with ammonia to generate an amide compound, while hydrogen peroxide is also added. The amide compound is detected by mass spectrometry, further demonstrating that the nitrogen-water microdroplet gas-liquid interface confined catalytic reaction includes the generation of both ammonia and hydrogen peroxide.

[0065] In another embodiment of this disclosure, in step S4, the generated ammonia gas or ammonia water is collected. Specifically, the step of collecting the ammonia includes: setting a collecting device at the spray end of the microdroplet generating device, the collecting device having a sealed collecting chamber, and the spray end of the microdroplet generating device being placed in the collecting chamber.

[0066] Furthermore, the collection chamber is also equipped with a conductive plate or a heating device.

[0067] In one embodiment, a heating device is provided inside the collection chamber. The heating device can be a heating tube, heating plate, or other similar device. The heating temperature can be set to 35-50°C. Heating the collection chamber through the heating device helps the ammonia vaporization and improves the ammonia production efficiency.

[0068] In another embodiment, a conductive plate is connected to the collection chamber. This conductive plate is grounded or connected to a high voltage to remove accumulated charge within the collection chamber, preventing the formation of a strong capacitive system and suppressing microdroplets formed based on electrohydrodynamics. This also helps improve the Faraday efficiency of the microdroplet reaction. Specifically, when the microdroplet generating device is an electrospray device, the conductive plate can be connected to a high voltage with the opposite polarity to the electrospray probe. The conductive plate can be, for example, a conductive polymer plate, which can be grounded or connected to a high voltage with the opposite polarity to the microdroplet generating device. More preferably, the conductive polymer plate can be, for example, a dense, porous polyaniline plate with a thickness of 0.5–2 cm. By setting the conductive polymer plate, excess charge is removed, promoting ammonia generation. Simultaneously, it receives the microdroplets during soft landing, collects the regulators within the microdroplets, and enables the recycling of the regulators.

[0069] More preferably, in another embodiment, a conductive plate and a heating device can be simultaneously provided in the collection chamber. For example, a heating device can be provided on the outer wall of the collection chamber, which can both remove the charge using the conductive plate and heat the ammonia dissolved in the aqueous solution to vaporize it and accelerate the production of ammonia.

[0070] Furthermore, in one embodiment of this disclosure, the collection chamber of the collection device is also connected to an air inlet pipe, through which carrier gas (nitrogen) is input into the collection chamber to drive the generated ammonia to be output from the air outlet pipe.

[0071] Specifically, Figure 4 This schematic diagram illustrates the structure of a collection device 400 in one embodiment of the present disclosure. Please refer to [link / reference]. Figure 4 The collecting device 400 has a sealed collecting chamber 410, into which the electrospray probe 420 of the microdroplet generating device (electrospray device) extends. The collecting chamber 410 can be constructed, for example, as a sealed housing. The collecting chamber 410 has an outlet pipe 412 and an inlet pipe 411. The outlet pipe 412 is located at the upper right of the collecting chamber 410, and the inlet pipe 411 is located at the lower left of the collecting chamber 410. Carrier gas is input through the inlet pipe 411, driving the gas to exit from the outlet pipe 412. A polyaniline plate 430, which can assist in heating, is installed inside the collecting chamber 410. The polyaniline plate 430 is located below the electrospray probe 420 and is connected to a high voltage with the opposite polarity to that of the electrospray probe 420.

[0072] The features and performance of this disclosure will be further described in detail below with reference to embodiments.

[0073] Example 1

[0074] This embodiment provides a method for preparing green ammonia, and through... Figure 3 The receiving device and mass spectrometer shown indirectly detect ammonia generated from the reaction of water and nitrogen microdroplets. Details are as follows:

[0075] (1) Prepare a 20 μmol / L fumaric acid aqueous solution, wherein aqueous solution a is a 500 μg / mL HAuCl4 aqueous solution; aqueous solution b is a 500 μg / mL PdCl2 aqueous solution; aqueous solution c is a 500 μg / mL HAuCl4-PdCl2 aqueous solution; and aqueous solution d is a 10 μmol / L fumaric acid aqueous solution. -2 An aqueous solution of AuPd alloy NPs at a concentration of mg / mL.

[0076] (2) Aqueous solutions a~d are fed into the pneumatic spray device to generate microdroplets. The inner diameter of the spray end of the inner tube of the pneumatic spray device is 150 μm, the flow rate of the syringe is 10 μL / min, and the diameter of the outer tube is 365 μm. Nitrogen gas is used as the sheath gas, and the sheath gas pressure is set to 60 psi.

[0077] like Figure 5 The image shows the mass spectra of fumaric acid aqueous solution in negative and positive ion modes. The left side shows the mass spectrum in negative ion mode, and the right side shows the mass spectrum in positive ion mode. Figure 5 As can be seen, fumaric acid has a m / z of 114.9468 in negative ion mode and a theoretical m / z of 115.0003, while in positive ion mode its m / z is 115.0481. The reason for this difference is that fumaric acid is an organic acid and should not respond in positive ion mode. However, the mass spectrum peak at m / z 115.0481 represents the amide compound formed after the reaction of fumaric acid with ammonia. Due to the presence of nitrogen atoms, it exhibits a strong response in positive ion mode. (See also...) Figure 6As shown, in positive ion mode, the mass spectrum peak at m / z=149.0578 of the fumaric acid aqueous solution (a-d) with added modifiers, based on its own ammonia amidation reaction with nitrogen (m / z=115.0481), differs from the fumaric acid amidation mass spectrum peak (m / z=115.0481) by 34, indicating that the two hydroxyl radicals (·OH) in the microdroplet reaction react simultaneously with fumaric acid. This result can also be observed in negative ion mode, although the signal response is weaker. Among the modifiers corresponding to the a-d aqueous solution, AuPd alloy has a higher response, with a response value of 76% of the amidation product. The above results indicate that nitrogen and water can generate ammonia through microdroplet reaction, and the ammonia yield is related to the type of modifier.

[0078] Example 2

[0079] This embodiment provides a method for preparing ammonia, and through methods such as... Figure 3 The mass spectrometer shown performs online mass spectrometry analysis. Details are as follows:

[0080] (1) Prepare aqueous solutions, wherein aqueous solution a is an aqueous solution of HAuCl4 with a concentration of 500 μg / mL; aqueous solution b is an aqueous solution of PdCl2 with a concentration of 500 μg / mL; aqueous solution c is an aqueous solution of HAuCl4-PdCl2 with a concentration of 500 g / mL; and aqueous solution d is an aqueous solution of AuPd alloy NPs with a concentration of 50 μg / mL.

[0081] (2) Aqueous solutions a~d are fed into the electrospray device to generate microdroplets. Nitrogen gas is applied to the spray end of the electrospray device. The inner diameter of the electrospray probe is 50 μm, the flow rate of the injection pump is 10 μL / min, and the electrospray bias voltage is -3 kV.

[0082] (3) The ammonia generated at the gas-liquid interface of the microdroplets enters the mass spectrometer through the transfer tube for online detection and analysis.

[0083] like Figure 7 As shown, the first spectrum on the left is the mass spectrum obtained from microdroplets formed from pure water under an air atmosphere, serving as a negative control. The first spectrum on the right is the mass spectrum obtained from microdroplets formed from pure water under a nitrogen atmosphere. The next spectrum shows the mass spectra of ammonia formed from aqueous solutions a~d and pure water (H2O) under an air atmosphere. Figure 7 It can be seen that, using air as a control, only trace amounts of ammonia were detected in the microdroplets formed from pure water. Microdroplets formed from aqueous solutions a~d exhibited a characteristic ammonia peak at m / z 17. Compared to aqueous solutions of chloroauric acid, palladium chloride, and chloroauric acid-palladium chloride, the abundance of ammonia generated from the gold-palladium alloy aqueous solution was significantly enhanced.

[0084] Example 3

[0085] This embodiment provides a method for preparing ammonia, and through methods such as... Figure 4 The collection device shown collects ammonia generated from the reaction of water and nitrogen microdroplets. Details are as follows:

[0086] (1) Prepare aqueous solutions, wherein aqueous solution a is a 500 μg / mL HAuCl4 aqueous solution; aqueous solution b is a 500 μg / mL PdCl2 aqueous solution; aqueous solution c is a 500 μg / mL HAuCl4-PdCl2 aqueous solution; and aqueous solution d is a 10 μg / mL PdCl2 aqueous solution. -2 An aqueous solution of AuPd alloy NPs at a concentration of mg / mL.

[0087] (2) Aqueous solutions a~d are respectively fed into the electrospray device to generate microdroplets. The electrospray probe 420 of the electrospray device has an inner diameter of 50 μm, the injection pump flow rate is 10 μL / min, and the electrospray bias voltage is -3 kV. The distance between the end of the electrospray probe 420 and the polyaniline plate 430 below is 3 cm.

[0088] (3) Nitrogen gas with a certain flow rate is introduced into the lower left of the collection chamber 410 as a carrier gas, and the ammonia generated in the collection chamber 410 is carried out through the gas outlet pipe 412 in the upper right.

[0089] After spraying for 60 minutes, the collected ammonia was detected by gas chromatography. The ammonia production capacity of nitrogen gas and pure water microdroplets formed by aqueous solutions a~d is shown in Table 1 below.

[0090] Table 1

[0091]

[0092] As shown in Table 1, the green ammonia preparation method disclosed in this paper significantly increases the ammonia production during the reaction of nitrogen and water microdroplets by adding different regulators. The ammonia content in microdroplets formed from pure water is extremely low and difficult to detect. The 500 μg / mL HAuCl4-PdCl2 (500 μg / mL) system can produce a maximum of 74.3 mol / gh, while 10 -2 The AuPd alloy system with a concentration of mg / mL can produce up to 683.9 mmol / gh, which is 9.2 times that of the chloroauric acid-palladium chloride system. It is highly practical and can provide support for hydrogen generation from the perspective of green environmental protection and economic conservation, providing a powerful solution for achieving the "dual carbon" goal.

[0093] The embodiments described above are some, but not all, of the embodiments of this disclosure. The detailed description of the embodiments of this disclosure is not intended to limit the scope of the claimed disclosure, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without inventive effort are within the scope of protection of this disclosure.

Claims

1. A method for preparing green ammonia based on a confined catalytic reaction at the gas-liquid interface of water and nitrogen microdroplets, characterized in that, include: S1, water and a regulator are mixed to obtain an aqueous solution, wherein the regulator is selected from one or more of nanomaterials, conductive polymers, and inorganic salts with redox properties; S2, Input the aqueous solution into the microdroplet generating device to generate microdroplets, wherein the size of the microdroplets is less than or equal to 10 μm; S3, a nitrogen atmosphere is formed at the spray end of the microdroplets, so that water and nitrogen in the microdroplets react spontaneously with free radicals generated at the gas-liquid interface to produce ammonia. The overall reaction equation is: ； S4, Detect or collect the ammonia; The microdroplet generating device is selected from one of an electro-spraying device, a pneumatic spraying device, and an ultrasonic atomizing device; The inorganic salt is selected from one or more of chloroauric acid, palladium chloride, and chloroauric acid-palladium chloride; the nanomaterial is selected from one or more of gold nanoparticles, palladium-coated gold nanoparticles, gold-palladium nanocomposites, and magnetic nanoparticles; the conductive polymer is selected from C 60 -(OH) n One or more of alkalized polyaniline-gold nanoparticle composites and acidified polyaniline-gold nanoparticle composites, wherein the modifier has an electron conduction promoting effect in the microdroplet reaction.

2. The method for preparing green ammonia based on the confined catalytic reaction at the gas-liquid interface of water and nitrogen microdroplets according to claim 1, characterized in that, The microdroplet generation device is an electrospray device, which has an electrospray probe. The flow rate of the aqueous solution injected into the electrospray probe is 5-150 μL / min. The inner diameter of the electrospray probe is 5-150 μm, and the applied bias voltage is 3-7 kV to generate microdroplets with a size of less than 10 μm. Nitrogen gas is applied to the spray end of the electrospray probe to form a nitrogen atmosphere.

3. The method for preparing green ammonia based on the confined catalytic reaction at the gas-liquid interface of water and nitrogen microdroplets according to claim 2, characterized in that, The electrospray device has multiple electrospray probes.

4. The method for preparing green ammonia based on the confined catalytic reaction at the gas-liquid interface of water and nitrogen microdroplets according to claim 1, characterized in that, The microdroplet generating device is a pneumatic spraying device, which includes an inner tube and an outer tube nested outside the inner tube. The end of the inner tube forms a spray end. Nitrogen gas is introduced into the outer tube as a sheath gas. The aqueous solution is injected into the inner tube and atomized by the sheath gas to form the microdroplets. The sheath gas flows to the spray end to form the nitrogen atmosphere.

5. The method for preparing green ammonia based on the confined catalytic reaction at the gas-liquid interface of water and nitrogen microdroplets according to claim 4, characterized in that, The aqueous solution is injected into the inner tube at a flow rate of 5-150 μL / min, the nitrogen gas used as sheath gas is at a pressure of 60-120 psi, and the generated microdroplets have a flight speed of 65-110 m / s.

6. The method for preparing green ammonia based on the confined catalytic reaction at the gas-liquid interface of water and nitrogen microdroplets according to claim 1, characterized in that, The step of detecting or collecting the ammonia includes: A mass spectrometer is installed at the spray end of the microdroplet generating device. The mass spectrometer receives the product generated at the spray end and performs mass spectrometry detection. The product is ammonia or amide. An organic acid is added to the aqueous solution in step S1. The amide is generated by the reaction of organic acid and ammonia. or, A collection device is provided at the spray end of the microdroplet generating device. The collection device has a sealed collection chamber, and the spray end is placed in the collection chamber.

7. The method for preparing green ammonia based on the confined catalytic reaction at the gas-liquid interface of water and nitrogen microdroplets according to claim 6, characterized in that, The collection chamber is also equipped with a conductive plate and / or a heating device. The conductive plate is grounded or connected to a high voltage to remove the charge accumulated in the collection chamber.

8. The method for preparing green ammonia based on the confined catalytic reaction at the gas-liquid interface of water and nitrogen microdroplets according to claim 6, characterized in that, The collection chamber is connected to an inlet pipe and an outlet pipe. Nitrogen gas is introduced into the inlet pipe, and the generated ammonia gas is output through the outlet pipe.

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