Method for preparing green ammonia on basis of microdroplet gas-liquid interface confined catalytic reaction of water and nitrogen gas

Abstract

A method for preparing green ammonia on the basis of microdroplet gas-liquid interface confined catalytic reaction of water and nitrogen gas. The preparation method comprises: mixing water and a regulator to obtain an aqueous solution, wherein the regulator is selected from one or more of a nanomaterial, a conductive polymer and an inorganic salt; and feeding the aqueous solution into a microdroplet generation device to generate microdroplets, the size of the microdroplets being less than or equal to 10 μm, and spontaneously generating hydrogen radicals and hydroxyl radicals by means of a dual-dielectric-layer strong electric field at a gas-liquid interface of the microdroplets. In a nitrogen atmosphere, a large number of hydrogen radicals and nitrogen in a gas phase are subjected to a radical chain reaction at the gas-liquid interface to generate ammonia, and hydroxyl radicals are combined to generate hydrogen peroxide. The method is simple in terms of preparation process, is green and environmentally friendly, and is not limited by a catalyst, and different production process requirements can be met by simply providing a regulator having a good electron conduction performance, which helps to meet the requirements of environmental protection in the context of "carbon peaking and carbon neutrality", and the strategic requirements of hydrogen energy storage.

Description

A method for preparing green ammonia based on the confined catalytic reaction of water and nitrogen microdroplets at the gas-liquid interface Technical Field

[0001] The present 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 of water and nitrogen microdroplets at a gas-liquid interface. Background Art

[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 an "energy carrier" and "hydrogen carrier" with significant application prospects. Breakthroughs in its green synthesis technology will contribute to the long-term development of hydrogen energy and are of great significance. Currently, industrial ammonia production mainly uses the Haber-Bosch process, which uses an Fe-based catalyst and operates at reaction conditions of 350-550°C and 100-300 atm. This process is characterized by high energy consumption, severe pollution, and demanding equipment and process technology. Research has shown that the Haber-Bosch process releases approximately 670 million tons of CO2 annually, accounting for approximately 2.4% of global carbon emissions, creating significant pressure to reduce emissions. Therefore, new ammonia synthesis technologies are urgently needed to address the high carbon emissions of existing ammonia synthesis processes and ultimately achieve "zero-carbon" ammonia production, known as green ammonia production.

[0003] In recent years, with the development of the hydrogen energy industry, a modified Habere-Bosch method has emerged, utilizing green hydrogen produced by water electrolysis and reacting it with nitrogen to produce green ammonia. Compared to the gray and blue ammonia produced in traditional industries, this route relies primarily 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 utilization). However, the production of green ammonia involves two steps: the production of green hydrogen through water electrolysis and the reaction of green ammonia with nitrogen and green hydrogen. While this process relies on the widespread availability and cost reduction of renewable energy sources such as wind, solar, and electricity, its cost, in terms of actual end-use applications, is still limited by the cost per kilowatt-hour of green hydrogen, which in turn increases the cost of end-use green ammonia and hinders its scalability.

[0004] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may include information that does not constitute prior art known to ordinary technicians in the field.

[0005] Summary of the Invention

[0006] The present disclosure provides a method for preparing green ammonia based on the gas-liquid interface confined catalytic reaction of water and nitrogen microdroplets. The method mainly utilizes microdroplet reaction, gas-liquid interface confined catalysis, etc., uses nitrogen and water as direct reactants, and realizes a new method for directly preparing green ammonia through a free radical chain reaction triggered by microdroplet gas-liquid interface confinement catalysis, providing new ideas and methods for achieving the "zero carbon" technical problem in the ammonia preparation process.

[0007] The present invention discloses a method for preparing green ammonia based on a confined catalytic reaction of water and nitrogen micro-droplets at a gas-liquid interface, comprising:

[0008] S1, mixing water and a regulator to obtain an aqueous solution, wherein the regulator is selected from one or more of nanomaterials, conductive polymers, and inorganic salts with redox properties;

[0009] S2, inputting the aqueous solution into a micro-droplet generating device to generate micro-droplets, wherein the size of the micro-droplets is less than or equal to 10 μm;

[0010] S3, forming a nitrogen atmosphere at the spray end of the micro-droplet, so that water and nitrogen in the micro-droplet react to generate ammonia by means of free radicals spontaneously generated at the gas-liquid interface;

[0011] S4, detecting or collecting the ammonia. Specifically, the generated ammonia can be ammonia gas in the form of gas or ammonia water in the form of liquid.

[0012] Specifically, in the present invention, the essence lies in the combination of nitrogen and hydrogen radicals (·H) generated at the gas-liquid interface of the microdroplets to form (·HNN), which reduces the activation energy and reaction barrier of the nitrogen reaction. At the same time, the hydroxyl radicals in the system form hydrogen peroxide through self-consistent combination, which is specifically as follows: H2O→·H+·OH N2+·H→·HNN ·HNN+·H→·HNNH ·HNNH·+ 2·H→2NH3 6·OH→3H2O2

[0013] The overall reaction equation is as follows:

[0014] In an exemplary embodiment of the present disclosure, the micro-droplet generating device is selected from one of an electrospray device, a pneumatic spray device and an ultrasonic atomization device.

[0015] In an exemplary embodiment of the present disclosure, the micro-droplet generating device is an electrospray device, which has an electrospray probe, and 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 micro-droplets with a size of less than 10 μm; wherein nitrogen is applied to the spray end of the electrospray probe to form a nitrogen atmosphere.

[0016] In an exemplary embodiment of the present disclosure, the electrospray device has a plurality of electrospray probes.

[0017] In an exemplary embodiment of the present disclosure, the micro-droplet generating device is a pneumatic spray 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 is introduced into the outer tube as sheath gas, the aqueous solution is injected into the inner tube, and is atomized by the sheath gas to form the micro-droplets; and the sheath gas flows to the spray end to form the nitrogen atmosphere.

[0018] In an exemplary embodiment of the present disclosure, the flow rate of the aqueous solution injected into the inner tube is 5-150 μL / min, the pressure of the nitrogen as sheath gas is 60-120 psi, and the flight speed of the generated microdroplets is 65-110 m / s.

[0019] In an exemplary embodiment of the present 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 -(OH)n, one or more of alkalized polyaniline-gold nanoparticle complexes and acidified polyaniline-gold nanoparticle complexes, wherein the modifier has or can generate an electron conduction effect in the microdroplet reaction.

[0020] In an exemplary embodiment of the present disclosure, when the regulator is an inorganic salt, the concentration of the inorganic salt in the aqueous solution is 50 to 1000 μg / mL; when the regulator is a nanomaterial or a conductive polymer, the concentration of the nanomaterial or the conductive polymer in the aqueous solution is 10 - 5 ~10 -1 mg / mL.

[0021] In an exemplary embodiment of the present disclosure, the step of collecting the ammonia includes: the step of detecting or collecting the ammonia includes:

[0022] A mass spectrometer is provided at the spray end of the micro-droplet generating device, and the mass spectrometer receives the product generated at the spray end and performs mass spectrometry detection; the product is ammonia or amide, and an organic acid is added to the aqueous solution in step S1, and the amide is generated by the reaction of the organic acid and ammonia;

[0023] or,

[0024] A collecting device is provided at the spray end of the micro-droplet generating device. The collecting device has a sealed collecting chamber, and the spray end is placed in the collecting chamber.

[0025] In an exemplary embodiment of the present disclosure, a conductive plate and / or a heating device is further provided in the collection chamber, and the conductive plate is grounded or connected to a high voltage to remove the charge accumulated in the collection chamber.

[0026] In an exemplary embodiment of the present disclosure, the collecting chamber is connected to an air inlet pipe and an air outlet pipe, nitrogen is introduced into the air inlet pipe, and the generated ammonia is output through the air outlet pipe.

[0027] The beneficial effects of the green ammonia preparation method based on micro-droplet reaction in the embodiment of the present disclosure are:

[0028] The green ammonia preparation method disclosed herein is implemented by using a micro-droplet generating device to obtain micro-droplets with a diameter of less than 10 μm. The micro-droplets have a "confinement effect" at the boundary scale and have special physical and chemical properties, such as high specific surface area, rich charge density, and a strong electric field of the dielectric double layer. The micro-droplets act as microreactors based on the special gas-liquid interface effect and the strong electric field effect of the gas-liquid interface (10 7 V / cm), ionizing water molecules (H + ), forming hydrogen radicals (·H,H + +e - →·H), further compound reaction between·H occurs (2·H→H2). However, due to the short half-life of hydrogen radical (·H) (<10 -9 s), will transiently reverse to form hydrogen ions (·He - →H + ). This process is controlled by electrons (e - ) is transferred, the electrons generated at the interface (e - ) to transfer, so that the reaction proceeds in the forward direction, hydrogen radicals (·H, H + +e -The hydroxyl radicals (NH) (H) (→·H) accumulate at the gas-liquid interface and combine with nitrogen in the gas phase under the strong electric field at the gas-liquid interface to form a transition state (NNH·), initiating a free radical chain reaction that ultimately produces NH3. This method realizes a new method for preparing green ammonia based on the synergistic effect of water microdroplets, nitrogen gas, and an electronically capable regulator. Simultaneously, hydroxyl radicals (·OH) combine to form H2O2 (2·OH→H2O2).

[0029] Compared to the current green ammonia production method, which uses green electricity to produce hydrogen and then combines hydrogen and ammonia through a modified Haber-Bosch process, this method uses water and nitrogen directly as raw materials, leveraging the gas-liquid interface confinement effect in a micro-droplet reaction to directly generate ammonia. Furthermore, a modifier significantly improves the ammonia production efficiency (683.9mmol / gh). Therefore, this method is environmentally friendly, low in energy consumption, and "zero-carbon" by directly producing ammonia from water and nitrogen, opening up a new path for the production of green ammonia.

[0030] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present disclosure and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0032] FIG1 is a flow chart of a method for preparing green ammonia based on a confined catalytic reaction of water and nitrogen micro-droplets at a gas-liquid interface according to an embodiment of the present disclosure;

[0033] FIG2 is a schematic structural diagram of a pneumatic atomization device according to an embodiment of the present disclosure;

[0034] FIG3 is a schematic structural diagram of a receiving device and a mass spectrometer according to an embodiment of the present disclosure;

[0035] FIG4 is a schematic diagram of a collection device according to an embodiment of the present disclosure;

[0036] FIG5 is a mass spectrogram of microdroplets generated by the fumaric acid aqueous solution in Example 1 of the present disclosure in negative ion and positive ion modes;

[0037] FIG6 is a mass spectrum of microdroplets generated from aqueous solutions a to d in Example 1 of the present disclosure in positive ion mode;

[0038] FIG7 is a mass spectrogram obtained from microdroplets generated from the negative control, pure water, and aqueous solutions a to d in Example 2 of the present disclosure. DETAILED DESCRIPTION

[0039] To make the purpose, technical solutions, and advantages of the embodiments of the present disclosure more clear, the technical solutions in the embodiments of the present disclosure are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer were followed. Reagents or instruments used where the manufacturer is not specified are conventional products that can be purchased commercially.

[0040] The following is a detailed description of the method for preparing green ammonia based on micro-droplet reaction according to an embodiment of the present disclosure.

[0041] Referring to FIG1 , an embodiment of the present invention provides a method for preparing green ammonia based on a confined catalytic reaction of water and nitrogen micro-droplets at a gas-liquid interface, comprising:

[0042] S1, mixing water and a regulator to obtain an aqueous solution, wherein the regulator is selected from one or more of nanomaterials, conductive polymers, and inorganic salts with redox properties;

[0043] S2, inputting the aqueous solution into a micro-droplet generating device to generate micro-droplets, wherein the size of the micro-droplets is less than or equal to 10 μm;

[0044] S3, forming a nitrogen atmosphere at the spray end of the micro-droplet, so that water and nitrogen in the micro-droplet react to generate ammonia by means of free radicals spontaneously generated at the gas-liquid interface;

[0045] S4, detecting or collecting the ammonia.

[0046] Microdroplet reactions rely primarily on droplets of 10 μm or less generated under external forces as microreactors. Unlike bulk reactions, they break the traditional understanding of water as a solvent at the macroscopic physicochemical scale and are endowed with special physicochemical properties, such as increased specific surface area, strong interfacial electric fields, reduced reaction barriers, and special redox properties. Compared to the macroscopic scale, microdroplets under microscopic conditions, as well as the gas-liquid interface at the bounding size (i.e., confined conditions), have a strong dielectric double layer with an electric field strength of up to 10 7 V / cm, which can induce the HER (hydrogen evolution reaction) and OER (oxygen evolution reaction) reactions at the boundary size. Depends on the characteristics of the electrochemical catalytic reaction, under the action of special dielectric materials, the catalytic effect of the gas-liquid interface of the micro-droplets can be enhanced, thus forming a gas-liquid interface confined catalytic reaction system. The green ammonia preparation method provided in this embodiment uses micro-droplets as micro-reactors, introduces electronic conductors into the micro-reactors through specific regulators, selectively adjusts the dielectric double layer thickness or conductive properties, improves the electron stripping efficiency, and promotes the combination of nitrogen and hydrogen radicals generated at the gas-liquid interface of the micro-droplets, thereby converting them into ammonia.

[0047] In one embodiment of the present 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). The redox effects of these inorganic salts improve the gas-liquid interface properties of the microdroplets and increase the efficiency of ammonia generation.

[0048] In one embodiment of the present disclosure, the nanomaterial is selected from one or more of Au NPs, palladium-coated gold nanoparticles (Au@Pd NPs), gold-palladium alloy nanoparticles (AuPd alloy NPs), and magnetic nanoparticles. Specifically, the magnetic nanoparticles may be, for example, ferrosoferric oxide nanoparticles (Fe3O4 NPs).

[0049] In one embodiment of the present disclosure, the conductive polymer is selected from C 60 The addition of one or more of the following nanoparticles: -(OH)n, alkaline polyaniline-gold nanoparticle complex (PANI@AuNPs-NaOH), and acidified polyaniline-gold nanoparticle complex (PANI@AuNPs-HCl). These nanoparticles can enhance interfacial effects, adjust the dielectric double layer thickness, alter electron stripping efficiency, and promote ammonia production.

[0050] Specifically, C 60 -(OH)n is C 60 Polyhydroxy compounds, also known as fullerols, are easily soluble in water because they contain multiple hydroxyl groups in their molecules. For example, C 60 -(OH)n. ANI@AuNPs-NaOH and PANI@AuNPs-HCl can be obtained according to the preparation method in the prior art. For example, in one embodiment, 3.5mL of 55nm gold nanoparticles are dispersed in 1.5mL of 2mM aniline and 0.25mL of 40mM SDS solution, shaken on a vortex mixer for 1min, and 1.5mL of 2mM (NH4)2S2O8-HCl aqueous solution is added. The mixture is mixed on a vortex oscillator for 10s. After reacting at room temperature for 12h, the aniline in the system is polymerized and wrapped on the surface of the gold nanoparticles to form a polymer-coated gold nanoparticle aqueous solution with a thickness of about 16nm. After centrifugation and washing, PANIAuNPs-HCl is obtained. PANI@AuNPs-HCl particles are dispersed in an aqueous solution, 2M NaOH solution is added, the pH of the solution is adjusted to 11.4, and magnetic stirring is performed for 2h to obtain PANI@AuNPs-NaOH.

[0051] In one embodiment of the present disclosure, when the regulator is an inorganic salt, the concentration of the inorganic salt in the aqueous solution is 50 to 1000 μg / mL; when the regulator is a nanomaterial or a conductive polymer, the concentration of the nanomaterial or the conductive polymer in the aqueous solution is 10 -5 ~10 -1 mg / mL. Different concentrations of regulator will generate different concentrations of ammonia in the reaction system.

[0052] Furthermore, in one embodiment of the present 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 more than 98 mmol / gh. Furthermore, when the regulator is AuPd alloy NPs, the concentration of AuPd alloy NPs in the aqueous solution is 10 -2 mg / mL. At this concentration, the ammonia yield reached over 683.9 mmol / gh. There are certain differences in the ammonia production efficiency between inorganic salts and nanoalloys, with nanoalloys exhibiting superior ammonia production capabilities. On the one hand, due to the excellent electron stripping properties of nanoalloys, they can promote the generation of hydrogen radicals (·H) and react with nitrogen at the gas-liquid interface. On the other hand, because the inorganic salt acts as a sacrificial agent, a redox reaction occurs between the hydrogen radicals and the inorganic salt system (3·H+HAuCl4→Au+4HCl, 2·H+PdCl2→Pd+2HCl), which consumes the hydrogen radicals (·H).

[0053] In one embodiment of the present disclosure, the micro-droplet generating device is selected from one of an electrospray device, a pneumatic spray device, and an ultrasonic atomization device. The specific structures of the electrospray device, the pneumatic spray device, and the ultrasonic atomization device can be referred to in the prior art. For example, the specific structure of the electrospray device can refer to the electrospray device used in mass spectrometry analysis technology.

[0054] In a 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, the syringe and the electrospray probe being connected via the connector, and the aqueous solution entering the electrospray probe via the syringe. The high-voltage power supply forms an electric field force at the spray end of the electrospray probe, and the aqueous solution is atomized to form microdroplets based on the principle of electrohydrodynamics. Nitrogen is applied to the periphery of the electrospray probe so that the nitrogen and the microdroplets undergo a free radical chain reaction to generate ammonia or ammoniacal liquor.

[0055] Furthermore, the electrospray device can be provided with multiple electrospray probes arranged in parallel, and the multiple electrospray probes can be connected to the same syringe, or each electrospray probe can be connected to a syringe. By using multiple electrospray probes arranged in parallel, the production efficiency of ammonia can be effectively improved.

[0056] Furthermore, 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 to 150 μm, and the bias voltage applied is 3 to 7 kV to generate micro-droplets with a size of less than 10 μm. Nitrogen gas is applied to the spray end of the electrospray probe through a gas cylinder or other device to form a nitrogen atmosphere, thereby achieving a free radical chain reaction between nitrogen and micro-droplets to generate ammonia gas or ammonia water. Under the above parameters, in terms of spatial dimension, the size of the generated micro-droplets is small, and the unit volume of aqueous solution has a higher or highest specific surface area, which increases the probability of nitrogen contacting the gas-liquid interface. At the same time, from the time dimension, the reaction time of nitrogen and micro-droplets at the gas-liquid interface is prolonged; the above spatial dimension and time dimension effects are beneficial to improving or enhancing the rate and efficiency of micro-droplet ammonia generation.

[0057] In a specific embodiment, as shown in Figure 2, 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) of 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 micro droplets at the spray end under the action of pneumatic atomization. The sheath gas flows to the spray end 240 to form the nitrogen atmosphere.

[0058] Furthermore, the aqueous solution is injected into the inner tube at a flow rate of 5-150 μL / min, the nitrogen sheath gas pressure is 60-120 psi, and the generated microdroplets have a flight velocity of 65-110 m / s. More preferably, the generated microdroplets have a flight velocity of 80-90 m / s. Under these parameters, the ammonia production rate is higher.

[0059] In one embodiment, the ultrasonic atomization device includes a syringe, an ultrasonic generator, and a spray head. The ultrasonic generator generates ultrasonic shock wave energy, which atomizes the aqueous solution into microdroplets. Nitrogen gas is output around the microdroplets through a device such as a gas cylinder to form a nitrogen atmosphere.

[0060] In one embodiment of the present disclosure, in step S4, the generated ammonia gas or ammonia water is detected. Specifically, the step of detecting the ammonia includes: providing a mass spectrometer at the spray end of the micro-droplet generating device, the mass spectrometer receiving the product generated by the spray end of the micro-droplet generating device and performing mass spectrometry detection.

[0061] 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 shows a device diagram for receiving and detecting ammonia in an example. As shown in Figure 3, the receiving device 310 has a sealed receiving chamber 311 (under air environment), and the spray end 321 of the micro-droplet generating device (electrospray device or pneumatic device) extends into the receiving chamber 311. The receiving chamber 311 can be obtained by, for example, constructing a round-bottom flask. The receiving chamber 311 has a transmission line 312, which is used to transport the ammonia in the chamber to the mass spectrometer. A refrigeration chamber 330 is provided outside the receiving chamber 311. The receiving chamber 311 is placed in the refrigeration chamber 330, which is filled with refrigerant to form a cold trap system for cooling the moisture formed during the solidification spraying process. The outlet pipe 212 transports the generated ammonia to the mass spectrometer 340 for online detection.

[0062] Furthermore, in one embodiment of the present disclosure, a refrigerant is provided outside the collection chamber to cool water formed during the solidification spraying process; the refrigerant is selected from one or more of liquid nitrogen, ice water, ice-containing brine, and ethylene glycol. This refrigerant effectively eliminates the effect of water in the microdroplets on the mass spectrometer detector during real-time, online mass spectrometry detection.

[0063] Specifically, in another embodiment, in the step of detecting ammonia, the product may also be an amide. Specifically, for ease of detection, an organic acid may be added to the aqueous solution in step S1, and the ammonia generated by the micro-droplet gas-liquid interface and nitrogen reacts with the organic acid in the micro-droplet to generate an amide compound. The amide compound is detected in mass spectrometry positive ion mode, thereby indirectly determining the ammonia in the system. For example, in one example, fumaric acid is added to the aqueous solution, and micro-droplets are generated by a pneumatic atomization device. The organic acid in the pneumatic atomized micro-droplets reacts with ammonia to generate an amide compound, and there is also the addition of hydrogen peroxide. The amide compound is detected by a mass spectrometry detector, which further proves that the confined catalytic reaction of nitrogen and water micro-droplet gas-liquid interface includes the generation of ammonia and the generation of hydrogen peroxide.

[0064] In another embodiment of the present disclosure, in step S4, the generated ammonia gas or ammonia water is collected. Specifically, the step of collecting the ammonia includes: providing a collection device at the spray end of the micro-droplet generating device, the collection device having a sealed collection chamber, and the spray end of the micro-droplet generating device is placed in the collection chamber.

[0065] Furthermore, a conductive plate or a heating device is provided in the collecting chamber.

[0066] In one embodiment, a heating device is provided in the collection chamber. The heating device may be a heating tube, a heating plate, or the like. The heating temperature may be set to 35-50°C. The heating device heats the collection chamber, thereby facilitating the vaporization of ammonia and improving ammonia production efficiency.

[0067] In another embodiment, the collection chamber is connected to a conductive plate, which is grounded or connected to a high voltage to remove the accumulated charge in the collection chamber, avoid the formation of a strong capacitance system, suppress the microdroplets formed based on electrohydrodynamics, and at the same time help 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 a polarity opposite to that of 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 a polarity opposite to that of the microdroplet generating device. More preferably, the conductive polymer plate can be, for example, a dense and porous polyaniline layer plate, and the thickness of the polyaniline layer plate can be 0.5 to 2 cm. By providing a conductive polymer plate, on the one hand, it is used to remove excess charge and promote the generation of ammonia, and on the other hand, it is used to receive microdroplets to form soft landing droplets, collect the regulator in the microdroplets, and realize the recycling of the regulator.

[0068] 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 is provided on the outer wall of the collection chamber, and the conductive plate can be used to remove the charge and to heat the solution to vaporize the ammonia dissolved in the aqueous solution, thereby accelerating the production of ammonia.

[0069] Furthermore, in one embodiment of the present disclosure, the collection chamber of the collection device is also connected to an air inlet pipe, through which a carrier gas (nitrogen) is input into the collection chamber to drive the generated ammonia to be output from the air outlet pipe.

[0070] Specifically, FIG4 schematically shows a schematic structural diagram of a collecting device 400 in one embodiment of the present disclosure. Referring to FIG4 , the collecting device 400 has a sealed collecting chamber 410, and an electrospray probe 420 of a micro-droplet generating device (electrospray device) extends into the collecting chamber 410. The collecting chamber 410 can be obtained by, for example, constructing a sealed box. The collecting chamber 410 has an outlet pipe 412 and an inlet pipe 411. The outlet pipe 412 is arranged at the upper right of the collecting chamber 410, and the inlet pipe 411 is arranged at the lower left of the collecting chamber 410. Carrier gas is input through the inlet pipe 411, driving the gas to be output from the outlet pipe 411. A polyaniline layer 430 that can assist in heating is installed in the collecting chamber 420. The polyaniline layer 430 is arranged below the electrospray probe 410 and is connected to a high voltage with a polarity opposite to that of the electrospray probe 420.

[0071] The features and performance of the present disclosure are further described in detail below with reference to the embodiments.

[0072] Example 1

[0073] This embodiment provides a method for preparing green ammonia, and indirectly detects ammonia generated by the reaction of water and nitrogen microdroplets using a receiving device and a mass spectrometer as shown in Figure 3. The details are as follows:

[0074] (1) Prepare a 20 μmol / L fumaric acid aqueous solution, wherein aqueous solution a is a HAuCl4 aqueous solution with a concentration of 500 μg / mL; aqueous solution b is a PdCl2 aqueous solution with a concentration of 500 μg / mL; aqueous solution c is a HAuCl4-PdCl2 aqueous solution with a concentration of 500 μg / mL; aqueous solution d is a HAuCl4-PdCl2 aqueous solution with a concentration of 10 -2 mg / mL AuPd alloy NPs aqueous solution.

[0075] (2) Aqueous solutions a to d were introduced into a pneumatic spray device to generate microdroplets. The inner diameter of the spray tip of the inner tube of the pneumatic spray device was 150 μm, the flow rate of the syringe was 10 μL / min, and the diameter of the outer tube was 365 μm. Nitrogen was used as the sheath gas, and the sheath gas pressure was set to 60 psi.

[0076] Figure 5 shows the mass spectra of an aqueous solution of fumaric acid 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. As can be seen in Figure 5, the m / z of fumaric acid in negative ion mode is 114.9468, while the theoretical m / z is 115.0003. In positive ion mode, the m / z is 115.0481. This is because fumaric acid is an organic acid and should have no response in positive ion mode. However, the mass peak at m / z 115.0481 is the amide compound formed by the reaction of fumaric acid and ammonia. Due to the presence of a nitrogen atom, it has a strong response in positive ion mode. As shown in Figure 6, in positive ion mode, the mass spectrum peak at m / z = 149.0578, based on the amidation reaction of fumaric acid with nitrogen (aqueous solutions a-d), differs by 34 from the fumaric acid amidation peak (m / z = 115.0481). This indicates that two hydroxyl radicals (·OH) reacted simultaneously with fumaric acid in the microdroplet reaction. This phenomenon was also observed in negative ion mode, albeit with a weaker signal response. Among the modifiers corresponding to aqueous solutions ad, AuPd alloy exhibited the highest response, with a response value of 76% of the amidation product. These results demonstrate that nitrogen and water can generate ammonia through microdroplet reactions, and that the ammonia yield is related to the type of modifier.

[0077] Example 2

[0078] This embodiment provides a method for preparing ammonia, and performs mass spectrometry online detection and analysis using a mass spectrometer as shown in FIG3 . The details are as follows:

[0079] (1) Aqueous solutions were prepared, wherein aqueous solution a was a HAuCl4 aqueous solution with a concentration of 500 μg / mL; aqueous solution b was a PdCl2 aqueous solution with a concentration of 500 μg / mL; aqueous solution c was a HAuCl4-PdCl2 aqueous solution with a concentration of 500 g / mL; and aqueous solution d was a AuPd alloy NPs aqueous solution with a concentration of 50 μg / mL.

[0080] (2) Aqueous solutions a to d were respectively introduced into an electrospray apparatus to generate microdroplets. Nitrogen gas was applied to the spray tip of the electrospray apparatus. The inner diameter of the electrospray probe was 50 μm, the flow rate of the syringe pump was 10 μL / min, and the electrospray bias voltage was -3 kV.

[0081] (3) The ammonia generated at the gas-liquid interface of the microdroplets enters the mass spectrometer through a transmission tube for online detection and analysis.

[0082] As shown in Figure 7, the first spectrum on the left is the mass spectrum obtained from microdroplets generated by pure water under an air atmosphere, serving as a negative control. The first spectrum on the right is the mass spectrum obtained from microdroplets generated by pure water under a nitrogen atmosphere. The mass spectra of ammonia generated by aqueous solutions a-d and pure water (H2O) under an air atmosphere are shown. As can be seen from Figure 7, with air as the control, only trace amounts of ammonia were detected in the microdroplets generated by pure water. The microdroplets generated by aqueous solutions a-d exhibit 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 by the gold-palladium alloy aqueous solution is significantly higher.

[0083] Example 3

[0084] This embodiment provides a method for producing ammonia, and collects ammonia generated by the reaction of water and nitrogen micro-droplets using a collection device as shown in Figure 4. The details are as follows:

[0085] (1) Aqueous solutions were prepared, wherein aqueous solution a was a HAuCl4 aqueous solution with a concentration of 500 μg / mL; aqueous solution b was a PdCl2 aqueous solution with a concentration of 500 μg / mL; aqueous solution c was a HAuCl4-PdCl2 aqueous solution with a concentration of 500 μg / mL; aqueous solution d was a HAuCl4-PdCl2 aqueous solution with a concentration of 10 -2 mg / mL AuPd alloy NPs aqueous solution.

[0086] (2) Aqueous solutions a through d were introduced into an electrospray apparatus to generate droplets. The electrospray probe 420 had an inner diameter of 50 μm, the syringe pump flow rate was 10 μL / min, and the electrospray bias voltage was -3 kV. The distance between the end of the electrospray probe 420 and the underlying polyaniline layer 430 was 3 cm.

[0087] (3) Nitrogen gas at a certain flow rate is input into the lower left corner of the collecting chamber 410 as a carrier gas, and the ammonia generated in the collecting chamber 420 is carried out through the outlet pipe 412 at the upper right corner.

[0088] After 60 minutes of spraying, the collected ammonia was detected by gas chromatography. The ammonia production capacity of nitrogen gas and pure water droplets formed by aqueous solutions a to d is shown in Table 1 below.

[0089] Table 1

[0090] As can be seen from Table 1, the green ammonia preparation method disclosed herein, by adding different regulators, greatly increases the amount of ammonia produced in the reaction of nitrogen and water microdroplets. The ammonia content in the microdroplets formed by pure water is extremely low and difficult to detect. The 500μg / mL HAuCl4-PdCl2 (500μg / mL) system can produce a maximum of 74.3mol / gh, while 10 -2 The AuPd alloy system with a concentration of 1 mg / mL can produce a maximum of 683.9 mmol / gh, which is 9.2 times that of the chloroauric acid-palladium chloride system. It is highly practical and can easily support hydrogen generation from the perspective of green environmental protection and economic savings, providing a powerful solution for achieving the "dual carbon" goal.

[0091] The embodiments described above are some of the embodiments of the present disclosure, rather than all of them. The detailed description of the embodiments of the present disclosure is not intended to limit the scope of the present disclosure as claimed, but merely represents selected embodiments of the present disclosure. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present disclosure without creative effort are within the scope of protection of the present disclosure.

Claims

1. A method for preparing green ammonia based on the confined catalytic reaction of water and nitrogen micro-droplets at the gas-liquid interface, characterized in that: include: S1, mixing water and a regulator 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, inputting the aqueous solution into a micro-droplet generating device to generate micro-droplets, wherein the size of the micro-droplets is less than or equal to 10 μm; S3, forming a nitrogen atmosphere at the spray end of the micro-droplet, so that the water and nitrogen in the micro-droplet react with the free radicals spontaneously generated at the gas-liquid interface to generate ammonia, wherein the overall reaction equation is: S4, detecting or collecting the ammonia.

2. The method for preparing green ammonia based on the confined catalytic reaction of water and nitrogen micro-droplets at the gas-liquid interface according to claim 1, characterized in that: The micro-droplet generating device is selected from one of an electrospray device, a pneumatic spray device and an ultrasonic atomization device.

3. The method for preparing green ammonia based on the confined catalytic reaction of water and nitrogen micro-droplets at the gas-liquid interface according to claim 2, characterized in that: The micro-droplet generating device is an electrospray device, which has an electrospray probe, and 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 magnitude of the applied bias voltage is 3-7 kV to generate micro-droplets with a size less than 10 μm; wherein nitrogen is applied to the spray end of the electrospray probe to form a nitrogen atmosphere.

4. The method for preparing green ammonia based on the confined catalytic reaction of water and nitrogen micro-droplets at the gas-liquid interface according to claim 3, characterized in that: The electrospray device has a plurality of electrospray probes.

5. The method for preparing green ammonia based on the confined catalytic reaction of water and nitrogen micro-droplets at the gas-liquid interface according to claim 2, characterized in that: The micro-droplet generating device is a pneumatic spray 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 is introduced into the outer tube as sheath gas, the aqueous solution is injected into the inner tube, and is atomized by the sheath gas to form the micro-droplets; and the sheath gas flows to the spray end to form the nitrogen atmosphere.

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

7. The method for preparing green ammonia based on the confined catalytic reaction of water and nitrogen micro-droplets at the gas-liquid interface according to claim 1, characterized in that: 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 complexes and acidified polyaniline-gold nanoparticle complexes, wherein the regulator has an effect of promoting electron conduction in microdroplet reactions.

8. The method for preparing green ammonia based on the confined catalytic reaction of water and nitrogen micro-droplets at the gas-liquid interface according to claim 1, characterized in that: The step of detecting or collecting the ammonia comprises: A mass spectrometer is arranged at the spray end of the micro-droplet generating device, and the mass spectrometer receives the product generated at the spray end and performs mass spectrometry detection; the product is ammonia or amide, and an organic acid is added to the aqueous solution in step S1, and the amide is generated by the reaction of the organic acid and ammonia; or, A collecting device is arranged at the spray end of the micro-droplet generating device. The collecting device has a sealed collecting chamber, and the spray end is placed in the collecting chamber.

9. The method for preparing green ammonia based on the confined catalytic reaction of water and nitrogen micro-droplets at the gas-liquid interface according to claim 8, characterized in that: A conductive plate and / or a heating device is also provided in the collection chamber. The conductive plate is grounded or connected to a high voltage to remove the charges accumulated in the collection chamber.

10. The method for preparing green ammonia based on the confined catalytic reaction of water and nitrogen micro-droplets at the gas-liquid interface according to claim 8, characterized in that: The collecting chamber is connected with an air inlet pipe and an air outlet pipe, nitrogen is introduced into the air inlet pipe, and the generated ammonia is output through the air outlet pipe.

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