Self-preheating pyrolysis system and preparation method of micro-nano particles

Abstract

The invention provides a self-preheating pyrolysis system and a preparation method of micro-nano particles, and relates to the technical field of material preparation, the self-preheating pyrolysis system comprises: a gas inlet part configured to receive precursor aerosol; the combustor is configured to perform pyrolysis on the precursor aerosol by combusting combustible gas and oxidizing gas which are introduced from the outside, so as to obtain micro-nano particles and pyrolysis gas; and the heating part is arranged between the gas inlet part and the combustor and is configured to heat the precursor aerosol entering the combustor by utilizing heat contained in the pyrolysis gas.

Description

Technical Field

[0001] The present disclosure relates to the technical field of material preparation, and more specifically, to a self-preheating pyrolysis system and a method for preparing micro-nano particles. Background Art

[0002] Micro- and nanomaterials, due to their large surface area and significant size effects, have found widespread application in energy and power, high-end optics, electronic information, and space exploration. Synthesis routes for micro- and nanomaterials can be categorized by solid-phase synthesis, liquid-phase wet methods, and vapor-phase synthesis, depending on the initial state of the material. Each method has its own advantages and disadvantages. The solid-phase method is simple, but it suffers from high reaction temperatures, long calcination times, high energy consumption, and coarse product particles. The liquid-phase wet method overcomes the shortcomings of the solid-phase method, including high sintering temperatures and uneven mixing, achieving molecular-level mixing and enabling controlled particle morphology. However, the liquid-phase wet method involves numerous process steps, high equipment investment, complex reaction parameters (such as pH), difficulty in controlling the reaction progress, the need for large amounts of reagents, and the generation of waste liquids, resulting in high production costs. The preparation of micro- and nanomaterials faces the challenge of reducing production costs and time while also minimizing environmental pollution.

[0003] Currently, flame spray pyrolysis can also be used to prepare micro-nano materials. As a type of gas-phase synthesis, flame spray pyrolysis is also known as flame aerosol synthesis. Flame spray pyrolysis refers to the process in which the raw materials of the product particles, namely the precursors, are vaporized or atomized and transported via a carrier gas to a high-temperature flame field provided by a burner. The product micro-nano particles are then obtained through a series of complex physical and chemical reactions. Compared with wet chemical synthesis methods, flame spray pyrolysis does not produce wastewater and waste residue. However, during the flame spray pyrolysis process, the precursor solution will evaporate rapidly in the high-temperature flame field, destroying the intact structure of the micro-nano particles and easily producing a broken fragmented structure, which cannot produce complete spherical micro-nano particles. Summary of the Invention

[0004] In order to solve at least one of the technical problems in the prior art, the embodiments of the present disclosure provide a self-preheating pyrolysis system and a method for preparing micro-nano particles, which can obtain micro-nano particles with complete structures through pyrolysis.

[0005] An embodiment of the present disclosure provides a self-preheating pyrolysis system, comprising: an air inlet portion, configured to receive a precursor aerosol; a burner, configured to pyrolyze the precursor aerosol by burning combustible gas and oxidizing gas introduced from the outside to obtain micro-nanoparticles and pyrolysis gas; a heating portion, arranged between the air inlet portion and the burner, configured to use the heat contained in the pyrolysis gas to heat the precursor aerosol entering the burner.

[0006] According to some embodiments of the present disclosure, the heating part includes: a first conveying pipeline, one end of which is connected to the exhaust part of the burner to convey the pyrolysis gas discharged from the exhaust part; a heat exchange unit, which is connected between the air inlet and the burner, and one side of the heat exchange unit is connected to the other end of the first conveying pipeline to receive the pyrolysis gas from the first conveying pipeline, and use the pyrolysis gas to heat the precursor aerosol entering the burner.

[0007] According to some embodiments of the present disclosure, the heat exchange unit includes: an inner tube, one end of which is connected to the air inlet, and the other end of which is connected to the burner, and the inner tube is configured to receive the precursor aerosol from the air inlet; an outer tube, which is sleeved on the outside of the inner tube and connected to the other end of the first conveying pipeline, so that the pyrolysis gas heats the precursor aerosol entering the inner tube.

[0008] According to some embodiments of the present disclosure, the heating part further includes: a control valve having an air inlet and two air outlets, the air inlet being connected to the first delivery pipeline, the first air outlet being connected to the outer tube, the first air outlet being configured to open when the temperature of the precursor aerosol entering the burner is not greater than a preset temperature, so that the pyrolysis gas enters the outer tube, and the second air outlet being connected to an external exhaust gas recovery device, the second air outlet being configured to open when the temperature of the precursor aerosol entering the burner is greater than the preset temperature, so that the pyrolysis gas enters the exhaust gas recovery device.

[0009] According to some embodiments of the present disclosure, the heating portion includes: a second delivery pipeline, one end of the second delivery pipeline is connected to the air intake portion, and the other end of the second delivery pipeline is connected to the burner, and the second delivery pipeline is coiled around the outer wall of the burner to utilize the heat contained in the pyrolysis gas to heat the precursor aerosol through the outer wall of the burner and then deliver it to the burner.

[0010] According to some embodiments of the present disclosure, the heating portion further includes: a plurality of support members installed at intervals on the outer wall of the burner to fix the second delivery pipeline on the burner.

[0011] According to some embodiments of the present disclosure, the heating temperature is 50°C to 700°C.

[0012] According to some embodiments of the present disclosure, the self-preheating pyrolysis system further includes: a collecting device, disposed above the burner, wherein the collecting device is provided with a fiber membrane, which is suitable for collecting the micro-nano particles on the fiber membrane by filtration and adsorption.

[0013] According to some embodiments of another aspect of the present disclosure, a method for preparing micro-nanoparticles is provided, which is prepared using the above-mentioned self-preheating pyrolysis system. The above-mentioned preparation method includes: dissolving a compound containing a precursor target element in a solvent to obtain a precursor solution containing the above-mentioned precursor target element; atomizing the above-mentioned precursor solution and introducing a carrier gas to disperse the above-mentioned precursor solution into a precursor aerosol; preheating the above-mentioned precursor aerosol to evaporate part of the above-mentioned solvent contained in the above-mentioned precursor aerosol, thereby reducing the particle size of the above-mentioned precursor aerosol; pyrolyzing the preheated precursor aerosol, so that the above-mentioned preheated precursor aerosol evaporates, pyrolyzes, nucleates, collides, and coalesces to obtain micro-nanoparticles.

[0014] According to some embodiments of the present disclosure, the above-mentioned precursor target elements include one or more of titanium, iron, nickel, cobalt, manganese, yttrium, boron, silicon, and selenium; the concentration of the precursor target elements in the above-mentioned precursor solution is 0.1 mol / L~3 mol / L.

[0015] According to the self-preheating pyrolysis system and the preparation method of micro-nano particles in the embodiments of the present disclosure, the air inlet receives the precursor aerosol, and the burner pyrolyzes the precursor aerosol by burning combustible gas and oxidizing gas introduced from the outside to obtain micro-nano particles and pyrolysis gas. The heating part is arranged between the air inlet and the burner. The heating part uses the heat contained in the pyrolysis gas to heat the precursor aerosol entering the burner. The precursor aerosol is preheated before entering the burner, which allows some components of the precursor aerosol to be prepyrolyzed before entering the burner, and then pyrolyzed after entering the burner to obtain micro-nano particles with complete structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a cross-sectional view of a self-preheating pyrolysis system according to an illustrative embodiment of the present disclosure;

[0017] Figure 2 is a perspective view of a self-preheating pyrolysis system according to another exemplary embodiment of the present disclosure;

[0018] Figure 3 is a flow chart of a method for preparing micro-nanoparticles according to an illustrative embodiment of the present disclosure;

[0019] Figure 4 1 is a process diagram of forming solid micro-nano particles by preheating and slow evaporation according to Example 1 of the present disclosure and an SEM image of the solid micro-nano particles;

[0020] Figure 5 1 is an XRD test result diagram of solid manganese trioxide micro-nano particles prepared according to Example 1 of the present disclosure;

[0021] Figure 61 is a process diagram of forming hollow micro-nano particles by preheating and rapid evaporation according to Example 2 of the present disclosure and an SEM image of the hollow micro-nano particles;

[0022] Figure 7 1 is an XRD test result diagram of cobalt oxide micro-nano particles with a hollow spherical structure prepared according to Example 2 of the present disclosure;

[0023] Figure 8 1 is a process diagram of generating broken micro-nano particles without preheating according to Comparative Example 1 of the present disclosure and an SEM image of the broken micro-nano particles;

[0024] Figure 9 1 is an XRD test result diagram of the manganese trioxide micro-nano particles with a crushed structure prepared according to Comparative Example 1 of the present disclosure.

[0025] In the accompanying drawings, the meanings of the reference numerals are as follows:

[0026] 1. Air intake;

[0027] 2. Burner;

[0028] 21. First round tube;

[0029] 22. Second round tube;

[0030] 23. The third round tube;

[0031] 24. Housing;

[0032] 3. Heat exchange unit;

[0033] 31. Inner tube;

[0034] 32. External control;

[0035] 4. The first delivery pipeline;

[0036] 5. Control valve;

[0037] 6. Tail gas recovery equipment;

[0038] 7. Collection device;

[0039] 8. Pyrolysis gas discharge pipeline;

[0040] 9. Temperature control device;

[0041] 10. The second delivery pipeline. DETAILED DESCRIPTION

[0042] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present disclosure. In the detailed description below, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0043] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise," "include," etc. used herein indicate the presence of the features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0044] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0045] When expressions such as “at least one of A, B, and C, etc.” are used, they should generally be interpreted in accordance with the meaning commonly understood by those skilled in the art (for example, “a system having at least one of A, B, and C” should include but is not limited to systems having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, and C, etc.). When expressions such as “at least one of A, B, or C, etc.” are used, they should generally be interpreted in accordance with the meaning commonly understood by those skilled in the art (for example, “a system having at least one of A, B, or C” should include but is not limited to systems having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, and C, etc.).

[0046] Currently, methods commonly used to prevent the formation of broken particles and maintain particle integrity include adjusting the precursor type, precursor solution concentration, pyrolysis temperature, adding additives to the precursor solution, and incorporating a preheating stage. Preheating stages often use external heat sources, such as electric heating, to heat the precursor aerosol, but this results in high energy consumption. The large amount of heat present in the pyrolysis gas is generally treated as exhaust, and the residual heat is not effectively utilized.

[0047] In order to solve the problem that the precursor aerosol evaporates quickly in the high-temperature flame field and easily produces broken micro-nanoparticles, and at the same time effectively utilize the residual heat, according to the inventive concept of one aspect of the present disclosure, a self-preheating pyrolysis system and a method for preparing micro-nanoparticles are provided. The air inlet receives the precursor aerosol, and the burner pyrolyzes the precursor aerosol by burning combustible gas and oxidizing gas introduced from the outside to obtain micro-nanoparticles and pyrolysis gas. The heating part is arranged between the air inlet and the burner. The heating part uses the heat contained in the pyrolysis gas to heat the precursor aerosol entering the burner. The precursor aerosol is preheated before entering the burner, which can allow some components of the precursor aerosol to be prepyrolyzed before entering the burner, and then pyrolyzed after entering the burner to obtain micro-nanoparticles with complete structure.

[0048] Figure 1 is a cross-sectional view of a self-preheating pyrolysis system according to an exemplary embodiment of the present disclosure.

[0049] According to an embodiment of the present disclosure, a self-preheating pyrolysis system is provided, such as Figure 1 As shown, the self-preheating pyrolysis system includes an air inlet 1, a burner 2, and a heating unit. The air inlet 1 is configured to receive a precursor aerosol. The burner 2 is configured to pyrolyze the precursor aerosol by burning combustible and oxidizing gases introduced from the outside, producing micro-nanoparticles and pyrolysis gas. The heating unit is disposed between the air inlet 1 and the burner 2 and is configured to utilize the heat contained in the pyrolysis gas to heat the precursor aerosol entering the burner 2.

[0050] According to an embodiment of the present disclosure, the burner 2 may be a coaxial burner, a Hencken burner, a McKenna burner, an opposed burner, a stagnation flame burner, or the like.

[0051] According to an embodiment of the present disclosure, when the burner 2 is a coaxial burner, the coaxial burner includes a first circular tube 21, a second circular tube 22, a third circular tube 23, and a shell 24. The first circular tube 21, the second circular tube 22, and the third circular tube 23 are coaxially arranged, the second circular tube 22 is sleeved on the outside of the first circular tube 21, and the third circular tube 23 is sleeved on the outside of the second circular tube 22. A flow channel for the precursor aerosol is formed in the first circular tube 21, and an annular flow channel for the oxidizing gas is formed between the second circular tube 22 and the first circular tube 21. Oxidizing gas channels are formed by radially extending from the second circular tube 22 to both sides with the second circular tube 22 as the center. One end of each oxidizing gas channel extends outward through the shell 24. The oxidizing gas channel is configured to receive an oxidizing gas introduced from the outside, such as air, oxygen, etc. An annular combustible gas flow channel is formed between the third circular tube 23 and the second circular tube 22. With the third circular tube 23 as the center, combustible gas channels are formed by radially extending from the third circular tube 23 to both sides. One end of each combustible gas channel extends outward through the shell 24. The combustible gas channel is configured to receive combustible gas introduced from the outside, such as hydrogen, methane, propane, acetylene, natural gas, etc.

[0052] According to an embodiment of the present disclosure, the burner 2 may be ignited by spark ignition, laser ignition, heating wire ignition, etc. The temperature field in the burner 2 is controlled to be between 500°C and 3000°C.

[0053] According to an embodiment of the present disclosure, the particle size of the micro-nano particles is 0.1 μm to 15 μm.

[0054] According to an embodiment of the present disclosure, the air inlet 1 receives the precursor aerosol, and the burner 2 pyrolyzes the precursor aerosol by burning combustible gas and oxidizing gas introduced from the outside to obtain micro-nano particles and pyrolysis gas. The heating part is arranged between the air inlet 1 and the burner 2. The heating part uses the heat contained in the pyrolysis gas to heat the precursor aerosol entering the burner 2. The precursor aerosol is preheated before entering the burner 2, which allows the precursor aerosol to be pre-pyrolyzed before entering the burner 2. After entering the burner 2, it is pyrolyzed to obtain micro-nano particles with complete structure. The residual heat of the combustion pyrolysis gas is directly used as the heat source for preheating, which plays a role in preheating the precursor aerosol, promoting the generation of complete micro-nano particles while reducing energy consumption.

[0055] According to an embodiment of the present disclosure, the heating unit includes a first delivery pipeline 4 and a heat exchange unit 3. One end of the first delivery pipeline 4 communicates with the exhaust of the burner 2 to transport the pyrolysis gas discharged from the exhaust. The heat exchange unit is connected between the air inlet 1 and the burner 2. One side of the heat exchange unit 3 is connected to the other end of the first delivery pipeline 4 to receive the pyrolysis gas from the first delivery pipeline 4. The heat exchange unit 3 uses the pyrolysis gas to heat the precursor aerosol entering the burner 2.

[0056] According to an embodiment of the present disclosure, the heat exchange unit 3 receives the pyrolysis gas from the first delivery pipeline 4 and uses the heat contained in the pyrolysis gas to preheat the precursor aerosol entering the burner 2, thereby enabling the reuse of the waste heat of the pyrolysis gas.

[0057] According to an embodiment of the present disclosure, the heat exchange unit 3 includes an inner tube 31 and an outer tube 32. One end of the inner tube 31 is connected to the air inlet 1, and the other end of the inner tube 31 is connected to the burner 2. The inner tube 31 is configured to receive the precursor aerosol from the air inlet 1. The outer tube 32 is sleeved on the outside of the inner tube 31 and connected to the other end of the first delivery pipeline 4, allowing the pyrolysis gas to heat the precursor aerosol entering the inner tube 31.

[0058] According to an embodiment of the present disclosure, one end of the inner tube 31 is connected to the air inlet 1, and the other end of the inner tube 31 is connected to the first circular tube 21 of the burner 2. The pyrolysis gas enters the outer tube 32 through the first conveying pipeline 4 and fills the surrounding area of ​​the inner tube 31, preheating the precursor aerosol entering the inner tube 31. The preheated precursor aerosol enters the burner 2 through the first circular tube 21 for pyrolysis.

[0059] According to an embodiment of the present disclosure, one side of the outer tube 32 is connected to the other end of the first conveying pipeline 4, and the other side of the outer tube 32 is connected to the pyrolysis gas exhaust pipeline 8. The pyrolysis gas preheats the precursor aerosol entering the inner tube 31 and is then discharged to the external exhaust gas recovery equipment through the pyrolysis gas exhaust pipeline 8.

[0060] According to an embodiment of the present disclosure, during the preheating process of the precursor aerosol, the temperature of the pyrolysis gas is higher than the preheating temperature set for the precursor aerosol, so as to provide sufficient temperature difference to the precursor aerosol for heat transfer and ensure the preheating effect. For example, the preheating temperature set for the precursor aerosol is 150°C, and the temperature of the pyrolysis gas is 300°C.

[0061] According to an embodiment of the present disclosure, a thermocouple is provided on the inner tube 31 of the heat exchange unit 3 , and the thermocouple can measure the temperature of the inner tube 31 in real time. The thermocouple can be a K-type thermocouple.

[0062] According to an embodiment of the present disclosure, the heating part also includes a control valve 5, which has an air inlet and two air outlets. The air inlet is connected to the first delivery pipeline 4, and the first air outlet is connected to the outer tube 32. The first air outlet is configured to open when the temperature of the precursor aerosol entering the burner 2 is not greater than the preset temperature, so that the pyrolysis gas enters the outer tube 32, and the second air outlet is connected to the external exhaust gas recovery equipment 6. The second air outlet is configured to open when the temperature of the precursor aerosol entering the burner 2 is greater than the preset temperature, so that the pyrolysis gas enters the exhaust gas recovery equipment 6.

[0063] According to an embodiment of the present disclosure, the temperature data measured by the thermocouple (the temperature of the precursor aerosol entering the burner 2 from the inner tube 31) is compared with a preset temperature of the precursor aerosol (e.g., 150°C). When the temperature data measured by the thermocouple is greater than the preset temperature of the precursor aerosol by more than 2°C to 3°C, the first outlet of the control valve 5 is closed, blocking the pyrolysis gas from entering the outer tube 32. The second outlet of the control valve 5 is opened, allowing the pyrolysis gas to enter the exhaust gas recovery device 6 through the second outlet. This prevents the pyrolysis gas from continuously heating the precursor aerosol entering the inner tube 31 and exceeding the preset temperature. When the temperature data measured by the thermocouple is less than 5°C, the first outlet of the control valve 5 is opened, allowing the pyrolysis gas to enter the outer tube 32 from the first delivery pipeline 4. A pressure differential is provided by a vacuum pump, etc., and the pyrolysis gas preheats the precursor aerosol entering the inner tube 31. The second outlet of the control valve 5 is closed. The temperature of the precursor aerosol preheated by the pyrolysis gas entering the inner tube 31 is maintained within a temperature range of -5°C to 3°C from the preset temperature, thereby achieving a dynamic balance of the preheating temperature.

[0064] According to an embodiment of the present disclosure, the pyrolysis gas enters the tail gas recovery device 6 through the second gas outlet. The tail gas recovery device 6 can be a water washing device that can treat the acidic waste gas in the pyrolysis gas. The tail gas recovery device 6 can also be a high-temperature resistant tail gas treatment device that can catalytically decompose and recover the pyrolysis gas.

[0065] According to an embodiment of the present disclosure, the heating unit further includes a temperature control device 9, which is provided in the first conveying pipeline 4. The temperature control device 9 is adapted to regulate the temperature of the pyrolysis gas. The temperature of the pyrolysis gas discharged from the exhaust portion of the burner 2 is generally above 500°C. For example, the temperature of the pyrolysis gas discharged from the exhaust portion of the burner 2 is 800°C, which exceeds the requirement that the preheating temperature of the precursor aerosol is 150°C and the temperature of the pyrolysis gas is 300°C. Therefore, the pyrolysis gas can be cooled by air heat exchange, or the temperature control device 9 can be used to cool the pyrolysis gas. The temperature control device 9 can cool the pyrolysis gas by water bath heat exchange or spray cooling.

[0066] According to an embodiment of the present disclosure, when the self-preheating pyrolysis system is operated for the first time, the burner 2 is first operated for 10 to 30 minutes, the pyrolysis gas is allowed to flow in the first conveying pipeline 4 for 10 to 30 minutes, and then the precursor aerosol is introduced into the air inlet 1, so that the precursor aerosol can quickly reach the temperature range for entering the burner 2 for pyrolysis.

[0067] Figure 2 is a perspective view of a self-preheating pyrolysis system according to another exemplary embodiment of the present disclosure.

[0068] According to the embodiments of the present disclosure, Figure 2 As shown, the heating part includes a second delivery pipeline 10, one end of the second delivery pipeline 10 is connected to the air inlet 1, and the other end of the second delivery pipeline 10 is connected to the burner 2. The second delivery pipeline 10 is coiled around the outer wall of the burner 2 to utilize the heat contained in the pyrolysis gas to heat the precursor aerosol through the outer wall of the burner 2 and then deliver it to the burner 2.

[0069] According to an embodiment of the present disclosure, the precursor aerosol enters the second conveying pipeline 10 from the air inlet 1, and the heat contained in the pyrolysis gas generated by pyrolysis in the burner 2 preheats the precursor aerosol in the second conveying pipeline 10 through the outer wall of the burner 2 and is then conveyed to the burner 2.

[0070] According to an embodiment of the present disclosure, the heating portion further includes a plurality of support members, which are installed at intervals on the outer wall of the burner 2 to fix the second delivery pipeline 10 on the burner 2 .

[0071] According to an embodiment of the present disclosure, a plurality of supports can position and fix the second delivery pipeline 10 on the outer wall of the burner 2. The supports can be, for example, screws. Positioning pins are provided in the middle and top of the second delivery pipeline 10 for fixing.

[0072] According to an embodiment of the present disclosure, the temperature at which the pyrolysis gas heats the precursor aerosol entering the burner 2 is 50°C to 700°C, and the temperature range that the precursor aerosol can reach is 50°C to 350°C.

[0073] According to an embodiment of the present disclosure, when the self-preheating pyrolysis system is operated for the first time, the burner 2 is first operated for 10 to 30 minutes, so that the pyrolysis gas preheats the outer wall of the shell 24 of the burner 2 for 10 to 30 minutes, and then the precursor aerosol is introduced through the air inlet part 1, so that the precursor aerosol can quickly reach the temperature range for entering the burner 2 for pyrolysis.

[0074] According to an embodiment of the present disclosure, the self-preheating pyrolysis system further includes a collecting device 7, which is disposed above the burner 2. A fiber membrane is disposed on the collecting device 7, and the collecting device 7 is suitable for collecting micro-nanoparticles on the fiber membrane by filtration and adsorption.

[0075] According to an embodiment of the present disclosure, the collecting device 7 may be, for example, a bag dust collecting device, an electrostatic dust collecting device, or a cyclone dust collecting device.

[0076] According to an embodiment of the present disclosure, the collecting device 7 may also collect the micro-nano particles by water washing.

[0077] Figure 3 4 is a flow chart of a method for preparing micro-nanoparticles according to an illustrative embodiment of the present disclosure.

[0078] According to another embodiment of the present disclosure, Figure 3 As shown, a method for preparing micro-nano particles is provided, which is prepared using the above-mentioned self-preheating pyrolysis system. The preparation method includes the following steps S1 to S4.

[0079] Step S1: dissolving a compound containing a precursor target element in a solvent to obtain a precursor solution containing the precursor target element.

[0080] According to an embodiment of the present disclosure, in order to uniformly dissolve a compound containing a precursor target element in a solvent, additives may be added to the solvent. The additives include organic additives and inorganic additives. The organic additives may be, for example, ethanol, propylene glycol, glycerol, etc., and the inorganic additives may be acids, for example, nitric acid, hydrochloric acid, etc.

[0081] Step S2: Atomize the precursor solution and introduce a carrier gas to disperse the precursor solution into a precursor aerosol.

[0082] According to embodiments of the present disclosure, atomization can be performed using one of ultrasonic atomization, pneumatic nozzle atomization, and electrostatic atomization. The droplet size of the atomized precursor solution is normally distributed, with the droplets varying in size depending on the atomization method. The droplet size is in the micron range, for example, 3 μm to 10 μm.

[0083] According to embodiments of the present disclosure, the carrier gas can be a non-flammable gas such as air, nitrogen, or oxygen. The carrier gas flow rate should be determined by the atomization method, burner size, and heating unit design. For example, when ultrasonic atomization is used, a small laboratory coaxial atomizer is used, and the heat exchange unit 3 uses a 1 / 4-inch inner tube. The carrier gas flow rate range is controlled within 0.25 SLM to 2.00 SLM.

[0084] Step S3: preheating the precursor aerosol to evaporate part of the solvent contained in the precursor aerosol, thereby reducing the particle size of the precursor aerosol.

[0085] According to an embodiment of the present disclosure, when the heating section includes a first delivery pipeline 4 and a heat exchange unit 3, the preheating time is determined by the length of the heat exchange unit 3 and the flow rate of the carrier gas. When the length of the heat exchange unit 3 is constant, the preheating time is adjusted by adjusting the flow rate (flow velocity) of the carrier gas. For example, increasing the flow rate of the carrier gas shortens the residence time of the precursor aerosol in the inner tube 31 of the heat exchange unit 3, shortening the preheating time. Reducing the flow rate of the carrier gas prolongs the residence time of the precursor aerosol in the inner tube 31 of the heat exchange unit 3, lengthening the preheating time. When the flow rate of the carrier gas is constant, the preheating time can also be adjusted by adjusting the length of the heat exchange unit 3, for example, shortening the length of the heat exchange unit 3 or increasing the length of the heat exchange unit 3. The preheating time can also be adjusted by adjusting both the length of the heat exchange unit 3 and the flow rate of the carrier gas simultaneously.

[0086] According to an embodiment of the present disclosure, the preheating time is controlled between 0.1s and 1.5s. For example, when the length of the heat exchange unit 3 is 0.3m, the flow rate of the carrier gas is 0.5m / s, and the preheating time is 0.6s.

[0087] According to an embodiment of the present disclosure, when the heating unit includes a second delivery pipeline 10, the preheating time is determined by the length of the second delivery pipeline 10 and the flow rate of the carrier gas. When the length of the second delivery pipeline 10 is constant, the preheating time is adjusted by adjusting the flow rate (flow velocity) of the carrier gas. For example, by increasing the flow rate of the carrier gas, the residence time of the precursor aerosol in the second delivery pipeline 10 becomes shorter, and the preheating time becomes shorter. By reducing the flow rate of the carrier gas, the residence time of the precursor aerosol in the second delivery pipeline 10 becomes longer, and the preheating time becomes longer. When the flow rate of the carrier gas is fixed, the preheating time can also be adjusted by adjusting the length of the second delivery pipeline 10, for example, the length of the second delivery pipeline 10 can be shortened or increased. It is also possible to adjust the length of the second delivery unit 10 and the flow rate of the carrier gas at the same time to adjust the preheating time.

[0088] Step S4: pyrolyzing the preheated precursor aerosol, so that the preheated precursor aerosol evaporates, pyrolyzes, nucleates, collides, and coalesces to obtain micro-nanoparticles.

[0089] According to the embodiments of the present disclosure, the process of generating a complete structure includes the following two methods. The first method is that the high-temperature flame in the burner 2 is in direct contact with the preheated precursor aerosol. First, the high-temperature evaporation process of the flame converts the droplets of the precursor solution into a gaseous precursor aerosol. The flame causes the gaseous precursor aerosol to undergo thermal decomposition, that is, the flame causes the compounds of the precursor target elements in the gaseous precursor aerosol to decompose due to heat and decompose into simple oxides. The simple oxides generate small particles as nucleation points (initial nanoparticles). After the initial nanoparticles collide and agglomerate, the final product is generated, that is, micro-nanoparticles with a solid and complete structure. The second is that the high-temperature flame in the burner 2 is in direct contact with the preheated precursor aerosol, and the high temperature of the flame slowly evaporates the solvent in the aerosol droplets of the preheated precursor solution until the solvent is completely evaporated, and the solute gradually precipitates while undergoing a pyrolysis reaction to maintain a solid structure, thereby generating solid and complete micro-nanoparticles, or the high temperature of the flame quickly evaporates the solvent in the aerosol droplets of the preheated precursor solution, and the solute gradually precipitates while undergoing a pyrolysis reaction to present a hollow structure, thereby generating hollow and complete micro-nanoparticles.

[0090] According to an embodiment of the present disclosure, the precursor target element includes one or more of titanium, iron, nickel, cobalt, manganese, yttrium, boron, silicon, and selenium. The concentration of the precursor target element in the precursor solution is 0.1 mol / L to 3 mol / L.

[0091] According to an embodiment of the present disclosure, the precursor target element includes a metal element or a non-metal element. The precursor target element is an element that easily generates solid metal oxides. Metal elements include titanium (Ti), iron (Fe), nickel (Ni), cobalt (Co), manganese (Mn), yttrium (Y), etc. Non-metal elements include boron (B), silicon (Si), selenium (Se), etc.

[0092] Example 1

[0093] Manganese nitrate tetrahydrate is dissolved in ultrapure water to obtain a precursor solution, wherein the cation concentration is 2 mol / L. The precursor solution is preheated by ultrasonic atomization through a first delivery pipeline 4 and a heat exchange unit 3. The temperature of the pyrolysis gas is 125°C to 225°C, and the preheating time is 0.56 s. The preheated precursor aerosol enters a coaxial burner, and a collection device 7 uses a glass fiber membrane filtration collection method to prepare solid manganese trioxide (Mn2O3) micro-nanoparticles.

[0094] Figure 4 1 is a process diagram of generating solid micro-nano particles by preheating and slow evaporation according to Example 1 of the present disclosure and an SEM image of the solid micro-nano particles.

[0095] Before the precursor aerosol enters the flame field, a first delivery pipeline 4 and a heat exchange unit 3 are provided to achieve pre-evaporation of the liquid precursor aerosol, which can alleviate the generation of broken structures. Figure 4 As shown, after the precursor aerosol droplets are preheated, the solvent evaporates slowly in the inner tube 31 of the heat exchange unit 3, and most of the solute is inside the droplets. When the droplets enter the flame of the burner 2, the solvent evaporates further to form a Figure 4 The SEM image shows relatively stable solid structure of manganese trioxide (Mn2O3) micro-nanoparticles.

[0096] Figure 5 This is an XRD test result diagram of the solid structured manganese trioxide micro-nano particles prepared according to Example 1 of the present disclosure.

[0097] Figure 5 The diffraction peaks in the XRD test of the pyrolysis product of Example 1 are as follows: Figure 5 Only the peak of Mn2O3 appeared in the experiment, and no other peaks appeared, indicating that the manganese nitrate in Example 1 was completely pyrolyzed to generate a single Mn2O3 phase.

[0098] Example 2

[0099] Cobalt nitrate hexahydrate is dissolved in ultrapure water to obtain a precursor solution, wherein the cation concentration is 1 mol / L. The precursor solution is preheated through a second delivery pipeline 10 by ultrasonic atomization. The temperature of the pyrolysis gas is stabilized at 200°C to 450°C, and the preheating time is 0.18 s. The preheated precursor aerosol enters a Henchen burner. The collection device 7 uses a glass fiber membrane for filtration and collection to prepare cobalt trioxide (Co3O4) micro-nanoparticles with a hollow structure.

[0100] Figure 6 1 is a process diagram of generating hollow micro-nano particles by preheating and rapid evaporation according to Example 2 of the present disclosure and an SEM image of the hollow micro-nano particles.

[0101] The precursor aerosol droplets are preheated, and the solvent evaporates quickly in the second delivery pipeline 10, and the solute part is separated to form a primary hollow structure. The preheated precursor aerosol enters the flame field of the Henchen burner, and a small amount of solvent evaporates to form a hollow structure. Figure 6 Cobalt trioxide (Co3O4) micro-nanoparticles with complete hollow spherical structure in the SEM image.

[0102] Figure 7 This is an XRD test result diagram of the hollow spherical cobalt oxide micro-nanoparticles prepared according to Example 2 of the present disclosure.

[0103] Figure 7is the diffraction peak obtained by XRD test of the pyrolysis product of Example 2, Figure 7 Only the peak of Co3O4 appears in the sample, and no other peaks appear, indicating that cobalt nitrate is completely thermally decomposed to form a single Co3O4 phase.

[0104] Comparative Example 1

[0105] The system and parameters used in this comparative example 1 are substantially the same as those in Example 1, except that the first conveying pipeline 4 and the heat exchange unit 3 are not provided for preheating in this comparative example 1, and manganese trioxide (Mn2O3) micro-nanoparticles with a crushed structure are prepared.

[0106] Figure 8 1 is a process diagram of generating broken micro-nano particles without preheating according to Comparative Example 1 of the present disclosure and an SEM image of the broken micro-nano particles.

[0107] Without preheating treatment, the solvent in the precursor aerosol evaporates quickly in the flame field of the coaxial burner, which will destroy the integrity of the particle structure and easily produce a broken fragmented structure. The generation process of the fragmented structure is as follows: Figure 8 As shown in the figure, the precursor aerosol droplets are not preheated. The solvent evaporates quickly in the high temperature flame of the coaxial burner, the solute precipitates to form a shell structure, and the solvent vaporizes to form a micro-explosion, causing the shell structure to break, generating Figure 8 The broken structure of manganese trioxide (Mn2O3) micro-nanoparticles is shown.

[0108] Figure 9 1 is an XRD test result diagram of the manganese trioxide micro-nano particles with a crushed structure prepared according to Comparative Example 1 of the present disclosure.

[0109] Figure 9 The diffraction peaks obtained from the XRD test of the pyrolysis product of Comparative Example 1 only have the peak of Mn2O3 and no other peaks, indicating that the manganese nitrate is completely pyrolyzed to generate a single Mn2O3 phase.

[0110] Figure 5 、 Figure 7 and Figure 9 XRD test results show that the nitrates in Examples 1, 2, and Comparative Example 1 all achieved complete pyrolysis, yielding a single oxide phase. SEM images, however, reveal distinct structures: a solid structure in Example 1, a hollow structure in Example 2, and a fragmented structure in Comparative Example 1. This indicates that preheating does not affect the phase of the pyrolysis products, achieving complete pyrolysis. However, preheating can affect the morphology of the micro-nanoparticles, allowing for control of their morphology.

[0111] Those skilled in the art will appreciate that various combinations and / or combinations of features described in the various embodiments and / or claims of this disclosure may be made, even if such combinations and / or combinations are not explicitly described in this disclosure. In particular, various combinations and / or combinations of features described in the various embodiments and / or claims of this disclosure may be made, without departing from the spirit and teachings of this disclosure. All such combinations and / or combinations fall within the scope of this disclosure.

[0112] It should also be noted that directional terms such as "upper," "lower," "front," "back," "left," and "right" mentioned in the embodiments are merely references to the directions in the accompanying drawings and are not intended to limit the scope of protection of the present disclosure. Throughout the drawings, identical elements are represented by identical or similar reference numerals. Conventional structures or configurations are omitted where they may cause confusion in understanding the present disclosure, and the shapes and dimensions of the components in the drawings do not reflect actual size or proportion, but are merely illustrative of the embodiments of the present disclosure.

[0113] Unless otherwise indicated, the numerical parameters in this specification and the appended claims are approximate and can vary depending on the desired properties obtained through the content of the present disclosure. Specifically, all numbers used in the specification and claims to express composition amounts, reaction conditions, etc. should be understood to be modified by the term "about" in all cases. Generally, the meaning of the expression is to include variations of ±10% in some embodiments, ±5% in some embodiments, ±1% in some embodiments, and ±0.5% in some embodiments from the specific amount.

[0114] The use of ordinal numbers such as "first," "second," and "third" in the specification and claims to modify corresponding elements does not in itself mean that the elements have any ordinal number, nor does it represent the order of one element relative to another or the order in the manufacturing method. The use of such ordinal numbers is only used to clearly distinguish one element with a certain name from another element with the same name.

[0115] Furthermore, unless specifically described or required to occur sequentially, the order of the steps is not limited to the order listed above and may be varied or rearranged based on desired design requirements. Furthermore, the above embodiments may be mixed and matched with each other or with other embodiments based on design and reliability considerations. That is, the technical features of different embodiments may be freely combined to form more embodiments.

[0116] The embodiments of the present disclosure are described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of the present disclosure. Although each embodiment has been described separately above, this does not mean that the measures in each embodiment cannot be used in combination to advantage. The scope of the present disclosure is defined by the appended claims and their equivalents. Without departing from the scope of the present disclosure, those skilled in the art may make various substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. A self-preheating pyrolysis system, characterized in that: include: an air inlet configured to receive a precursor aerosol; A burner is configured to pyrolyze the precursor aerosol by burning combustible gas and oxidizing gas introduced from the outside to obtain micro-nano particles and pyrolysis gas; The heating portion is disposed between the air inlet portion and the burner and is configured to heat the precursor aerosol entering the burner using the heat contained in the pyrolysis gas.

2. The self-preheating pyrolysis system according to claim 1, characterized in that: The heating unit includes: a first delivery pipeline, one end of which is in communication with an exhaust portion of the burner to deliver the pyrolysis gas exhausted from the exhaust portion; A heat exchange unit is connected between the air inlet and the burner, and one side of the heat exchange unit is connected to the other end of the first delivery pipeline to receive the pyrolysis gas from the first delivery pipeline and use the pyrolysis gas to heat the precursor aerosol entering the burner.

3. The self-preheating pyrolysis system according to claim 2, characterized in that: The heat exchange unit comprises: an inner tube, one end of the inner tube being in communication with the air inlet, the other end of the inner tube being in communication with the burner, the inner tube being configured to receive the precursor aerosol from the air inlet; The outer tube is sleeved on the outer side of the inner tube and is connected to the other end of the first delivery pipeline, so that the pyrolysis gas heats the precursor aerosol entering the inner tube.

4. The self-preheating pyrolysis system according to claim 3, characterized in that: The heating unit further includes: A control valve having an air inlet and two air outlets, wherein the air inlet is connected to the first delivery pipeline, the first air outlet is connected to the outer tube, the first air outlet is configured to open when the temperature of the precursor aerosol entering the burner is not greater than a preset temperature, so that the pyrolysis gas enters the outer tube, and the second air outlet is connected to an external exhaust gas recovery device, and the second air outlet is configured to open when the temperature of the precursor aerosol entering the burner is greater than the preset temperature, so that the pyrolysis gas enters the exhaust gas recovery device.

5. The self-preheating pyrolysis system according to claim 1, characterized in that: The heating unit includes: A second delivery pipeline, one end of the second delivery pipeline is connected to the air inlet, and the other end of the second delivery pipeline is connected to the burner. The second delivery pipeline is coiled around the outer wall of the burner to utilize the heat contained in the pyrolysis gas to heat the precursor aerosol through the outer wall of the burner and then deliver it to the burner.

6. The self-preheating pyrolysis system according to claim 5, characterized in that: The heating unit further includes: A plurality of support members are installed at intervals on the outer wall of the burner to fix the second delivery pipeline on the burner.

7. The self-preheating pyrolysis system according to claim 3 or 5, characterized in that: The heating temperature is 50°C to 700°C.

8. The self-preheating pyrolysis system according to claim 1, characterized in that: Also includes: A collecting device is arranged above the burner. A fiber membrane is provided on the collecting device, which is suitable for collecting the micro-nano particles on the fiber membrane by filtering and adsorption.

9. A method for preparing micro-nano particles using the self-preheating pyrolysis system according to any one of claims 1 to 8, the method comprising: dissolving a compound containing a precursor target element in a solvent to obtain a precursor solution containing the precursor target element; Atomizing the precursor solution and introducing a carrier gas to disperse the precursor solution into a precursor aerosol; preheating the precursor aerosol to evaporate a portion of the solvent contained in the precursor aerosol, thereby reducing the particle size of the precursor aerosol; The preheated precursor aerosol is pyrolyzed, so that the preheated precursor aerosol evaporates, pyrolyzes, nucleates, collides, and coalesces to obtain micro-nano particles.

10. The preparation method according to claim 9, characterized in that The precursor target element includes one or more of titanium, iron, nickel, cobalt, manganese, yttrium, boron, silicon, and selenium; The concentration of the precursor target element in the precursor solution is 0.1 mol / L to 3 mol / L.

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