Method and system for preparing SiO2 multi-shell hollow microsphere powder with adjustable void ratio

Abstract

The invention discloses a method and a system for preparing SiO2 multi-shell hollow microsphere powder with adjustable void ratio. The method comprises the processes of synthesis of a silicon amine precursor, controllable hydrolysis aging, dehydration drying and the like. The diameter of the hollow SiO2 microspheres prepared by the method is about 1.5-3.5 microns, and the porosity is adjustable in a range of 0.05-0.85. The system comprises a controllable hydrolysis aging device (2), a separation device (3), a drying device (4) and a pH monitoring and adjusting device (5). Compared with the traditional technology, the method not only solves the problem that the SiO2 multi-shell hollow microspheres with adjustable porosity are difficult to synthesize by the traditional process, but also has the advantages of simple process flow, low synthesis cost and industrial batch preparation capability.

Description

Technical Field

[0001] The present invention relates to the field of chemical materials, and specifically to a method and a system for preparing SiO2 multi-shell hollow microsphere powder with adjustable porosity. Background Art

[0002] Due to the multiple shells with rich pores and the mutually independent multiple cavity structures, SiO2 multi-shell hollow microspheres can significantly increase the specific surface area and effectively regulate the mass diffusion and energy transfer. Therefore, they have broad application prospects in the fields of confined catalysis, energy storage, mass adsorption and separation, and drug controlled release. Porosity (the ratio of the total volume of voids in the multi-shell microsphere to the volume of the microsphere) is an important structural feature of SiO2 multi-shell microspheres, which can significantly affect the size of the space for accommodating substances and the wall effect of the microspheres, and has an important impact on mass adsorption, encapsulation, storage, and diffusion regulation. However, there is currently a lack of an effective method for large-range adjustment of it.

[0003] Generally, the main methods for synthesizing SiO2 multi-shell hollow microspheres are as follows:

[0004] (1) Self-assembly method (soft template method): By adjusting the types and proportions of organic solvents, water, and surfactants, the three substances spontaneously assemble to form a multi-shell vesicle (about 150 nm) microemulsion system (Science., 1998). After tetraethyl orthosilicate (TEOS) is added, a hydrolysis reaction occurs to generate silicic acid precursor nanoparticles (Si(OCH2CH3)4(l)+4H2O(l)=Si(OH)4(s)+4C2H5OH(l)). After being adsorbed by the vesicle template, the particles become multi-shell silica microspheres containing the microemulsion template. Then, the vesicle template is etched away by high-temperature calcination, and the multi-shell silica microspheres are hardened (H4SiO4(s)=SiO2(s)+2H2O(g)). Finally, SiO2 multi-shell hollow microspheres are obtained. The size of the obtained microspheres is 150 nm, the number of layers does not exceed two, and the porosity is generally less than 0.3. It is currently difficult to increase or decrease the porosity. This is because to regulate the porosity, a stable vesicle structure with adjustable porosity needs to be obtained. To achieve this goal, there are currently two major problems: First, to obtain a stable vesicle, it is necessary to satisfy the strict ratio of water, organic solvent, and surfactant to ensure that the intermolecular forces and solvent surface tension in the liquid environment are reasonably balanced. Second, there is still a lack of an effective method for regulating the water-oil thickness ratio and there is no reference theoretical guiding principle. Therefore, the powder synthesized based on this method usually has a fixed porosity and cannot be controllably adjusted currently.

[0005] (2) Layer-by-layer templating method: Generally, a carbon-based polymer material is used as a spherical template (for example, polystyrene microspheres with a diameter of 100 nm). TEOS and the precursor of the carbon-based polymer are alternately deposited on the template multiple times to obtain a multi-shell microsphere structure with alternating encapsulation of polymer@silicate. Finally, the carbon-based polymer shell layer is etched away by high-temperature calcination (>500 °C) to obtain SiO2 multi-shell hollow microspheres (Biomaterials., 2011). The size of the microspheres synthesized by this method is mainly 300 nm, and the number of shell layers can vary from 2 to 10 layers with the number of times of alternately coating the template and the silicate shell layer. The porosity of the SiO2 multi-shell microspheres is mainly affected by the thickness of the polymer shell layer, and the formation of this shell layer is caused by the electrostatic adsorption of polymer precursor particles to the surface of the microspheres. Therefore, the particle size of the polymer precursor becomes the key to porosity regulation. Currently, a large number of research results show that the particle sizes of polymer precursor particles and silicate particles that can be deposited on the microsphere template are usually limited to about 20 - 30 nm, resulting in a comparable SiO2 shell thickness and layer spacing, and the porosity of the microspheres often varies slightly between 0.3 and 0.4.

[0006] (3) Sequential templating method: The silicate precursor generated by the hydrolysis of Na2SiO3 (Na2SiO3(s) + 3H2O(l) = H4SiO4(s) + 2NaOH(aq)) is adsorbed on the surface of the carbon-based material to obtain a core-shell microsphere with a silicate-coated carbon-based template (1 - 3 μm). During the high-temperature calcination process, the silicate precursor solidifies on the template from the outside to the inside as the carbon-based template decreases, forming SiO2 multi-shell microspheres with a size of 1 - 3 μm and a number of layers of 3 - 5 layers (Nat. Mater., 2016). The only current method to regulate the porosity is to change the heating temperature to simultaneously change the template etching rate and the hardening rate of the silicate shell layer. For example, the faster the template etching rate and the faster the silicate hardening rate, the more shell layers in the microsphere and the lower the porosity, and vice versa, the porosity will increase. The porosity of the SiO2 multi-shell hollow microspheres obtained by this method only varies between 0.3 and 0.5. However, there is still a lack of an effective method to significantly adjust the porosity.

[0007] In addition, based on the above analysis, it can be seen that the self-assembly method, the layer-by-layer templating method, and the sequential templating method all require template coating, repeated washing, and drying, resulting in a complex and lengthy preparation process. At the same time, high-temperature heat treatment is required to remove the template, which not only increases the difficulty of control but also significantly increases the energy consumption and equipment cost. In summary, there is an urgent need to develop a low-cost, efficient, and controllable method to prepare SiO2 multi-shell hollow microsphere powders with a wide range of adjustable porosity. Summary of the Invention

[0008] In view of the problems of complex synthesis process and high cost in the existing synthesis methods of SiO2 multi-shell hollow microsphere powders, the present invention proposes a method and a system for preparing SiO2 multi-shell hollow microsphere powders with adjustable porosity. The method provided by the present invention revolutionizes the traditional process flow, avoids the use of templates and high-temperature calcination post-treatment processes, directly synthesizes SiO2 multi-shell hollow microsphere powders with adjustable porosity in solution, and the adjustment range of porosity realizes a large range change between 0.05 and 0.85. In addition, the method and system provided by the present invention have the advantages of high synthesis efficiency, simple process, low cost, and can realize industrial mass production.

[0009] To achieve the above object, the present method adopts the following technical solutions:

[0010] A method for preparing SiO2 multi-shell hollow microsphere powders with adjustable porosity, the method comprising:

[0011] Precursor synthesis: reacting a halosilane with ammonia in a molar ratio of 1:1 to 1:30 at a temperature of -30 to 100 °C to obtain a mixture of a silylamine precursor and an ammonium halide;

[0012] Hydrolysis and aging: placing the mixture of the silylamine precursor and the ammonium halide in a liquid medium, and performing controllable hydrolysis and aging within a certain pH and temperature range to obtain a solution of silicic acid multi-shell microsphere powders;

[0013] Separation and drying: separating the solid and liquid of the solution of silicic acid multi-shell microsphere powders, and then drying to obtain SiO2 multi-shell hollow microsphere powders with a specific porosity.

[0014] Preferably, the halosilane is SiCl x H 4-x and / or SiBr x H 4-x , 0 ≤ x ≤ 4.

[0015] The SiO2 multi-shell hollow microsphere powders with a specific porosity provided by the present invention have a particle size of 1 to 3.5 microns, a porosity of 0.05 to 0.85; and the number of layers ranges from 2 to 8 layers.

[0016] Preferably, in the hydrolysis and aging, the mass ratio of the liquid medium to the mixture is 1:1 to 1:100.

[0017] Preferably, the liquid medium is one or at least two of ammonia water, water, and ethanol.

[0018] Preferably, in the hydrolysis and aging, the hydrolysis temperature is 10 to 40 °C, the pH range is 8 to 14, and the aging time is 0.5 to 48 h; in the separation and drying, the drying temperature is 30 to 60 °C.

[0019] Preferably, in the separation process, an impurity remover is added to the silica multi-shelled microsphere powder solution, and then solid-liquid separation is carried out; the impurity remover is liquid ammonia and / or ethylenediamine.

[0020] Preferably, in the hydrolysis and aging process, the acidic medium for pH adjustment is HCl gas and / or hydrochloric acid solution; the alkaline medium is one or at least two of ammonia water, ammonia gas, NaOH solution and KOH solution.

[0021] A system for preparing SiO2 multi-shelled hollow microsphere powder with adjustable porosity provided by the present invention, the system includes a controllable hydrolysis and aging device 2, a separation device 3, a drying device 4, and a pH monitoring and adjustment device 5;

[0022] The controllable hydrolysis and aging device 2, the separation device 3 and the drying device 4 are connected in sequence through pipelines, and the pH monitoring and adjustment device 5 is connected to the controllable hydrolysis and aging device 2 through a pipeline, and the pH change of the liquid medium in the controllable hydrolysis and aging device 2 is monitored in real time and adjusted to a preset value;

[0023] Or,

[0024] The separation device 3, the controllable hydrolysis and aging device 2 and the drying device 4 are connected in sequence through pipelines, and the pH monitoring and adjustment device 5 is connected to the controllable hydrolysis and aging device 2 through a pipeline, and the pH change of the liquid medium in the controllable hydrolysis and aging device 2 is monitored in real time and adjusted to a preset value.

[0025] Furthermore, the system further includes a precursor gas-phase synthesis device 1, and the precursor gas-phase synthesis device 1 is connected to the controllable hydrolysis and aging device 2 or the separation device 3 through a pipeline.

[0026] Preferably, the reactor of the precursor gas-phase synthesis device 1 is a fluidized-bed reactor, a fixed reaction bed or an impinging-stream reactor; the controllable hydrolysis and aging device 2 is a fluidized-bed reactor, a fixed reaction bed or a stirring reaction tank; the separation device 3 is a centrifuge or a filter; the drying device 4 is a fluidized-bed reactor or a fixed reaction bed; the pH monitoring and adjustment device 5 is composed of a pH detector, an acidic medium replenishing device and an alkaline medium replenishing device.

[0027] Preferably, the fluidizing gas of the fluidized-bed reactor is one or a mixed gas of any two or more of N2, H2, NH3, NH3·H2O, H2O and Ar.

[0028] The precursor gas-phase synthesis device 1 and the controllable hydrolysis and aging device 2 are directly connected through pipelines and material valves. A silane halide and ammonia react in the precursor gas-phase synthesis device 1 to form a mixture of a silazane precursor and ammonium halide NH4X (X = Br, Cl). The mixture enters the controllable hydrolysis and aging device 2 for hydrolysis and aging, and spontaneously forms a multi-shelled silica microsphere.

[0029] In the present invention, the silane halide and ammonia can also directly enter the controllable hydrolysis and aging device 2, react to form a mixture of a silazane precursor and ammonium halide NH4X (X = Br, Cl), and directly undergo hydrolysis and aging to spontaneously form a multi-shelled silica microsphere. This setting method can omit the precursor gas-phase synthesis device 1, achieving the effect of further saving processes and reducing equipment.

[0030] The pH monitoring and adjusting device 5 is directly connected to the controllable hydrolysis and aging device 2 through pipelines and material valves, and real-time monitors the pH change of the hydrolysis medium in the hydrolysis reactor and adjusts it to a preset value.

[0031] The separation device 3 is connected to the controllable hydrolysis and aging device 2. The multi-shelled silica microsphere powder obtained from the controllable hydrolysis and aging device 2 and the hydrolysis liquid medium jointly enter the separation device 3 for solid-liquid separation, thereby obtaining a moist multi-shelled hollow silica microsphere powder.

[0032] When there is a precursor gas-phase synthesis device 1, the separation device 3 can also be arranged in front of the controllable hydrolysis and aging device 2 to first separate the silazane precursor and ammonium halide. The separated silazane precursor enters the controllable hydrolysis and aging device 2 for further hydrolysis and aging to obtain a multi-shelled silica microsphere.

[0033] The drying device 4 is directly connected to the separation device 3 through pipelines and material valves. The moist multi-shelled hollow silica microsphere powder enters the drying device 4 from the separation device 3 and is dried, thereby obtaining a dry multi-shelled hollow SiO2 microsphere product.

[0034] The separation device 3 of the present invention is used to separate ammonium halide in the product. The separation method can be to add impurity removing agents liquid ammonia and / or ethylenediamine to the multi-shelled silica microsphere powder solution, and then perform solid-liquid separation using a centrifuge or a filter.

[0035] The present invention has the following advantages compared with the prior art:

[0036] (1) In the present invention, only the silazane precursor needs to be immersed in ammonia water for hydrolysis and aging, and then dried to obtain a multi-shelled hollow SiO2 microsphere powder, significantly improving the synthesis efficiency.

[0037] (2) It significantly expands the regulation range of the porosity, broadening the traditional regulation range of 0.3 - 0.5 to 0.05 - 0.85.

[0038] (3) The process is simpler, eliminating the preparation of spherical templates, the cumbersome washing and separation devices, and the high-temperature calcination process, significantly reducing the cost. Description of the Drawings

[0039] The drawings are used to provide further illustration of the present invention and form a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation to the present invention.

[0040] Figure 1 It is a system diagram for preparing SiO2 multi-shell hollow microsphere powder according to Embodiment 1 of the present invention;

[0041] Figure 2 It is a system diagram for preparing SiO2 multi-shell hollow microsphere powder according to Embodiment 2 of the present invention;

[0042] Figure 3 It is a system diagram for preparing SiO2 multi-shell hollow microsphere powder according to Embodiment 3 of the present invention;

[0043] Figure 4 It is a TEM diagram of the SiO2 multi-shell hollow microsphere powder obtained in Embodiment 3 of the present invention. Detailed Description of the Invention

[0044] The technical solutions of the present invention will be described in detail below with reference to the drawings and embodiments.

[0045] Embodiment 1

[0046] As Figure 1 shown, a system for preparing SiO2 multi-shell hollow microsphere powder with adjustable porosity, the system includes a precursor gas-phase synthesis device 1, a controllable hydrolysis and aging device 2, a separation device 3, a drying device 4, and a pH monitoring and adjustment device 5;

[0047] The precursor gas-phase synthesis device 1, the controllable hydrolysis and aging device 2, the separation device 3, and the drying device 4 are connected in sequence through pipelines, and the pH monitoring and adjustment device 5 is connected to the controllable hydrolysis and aging device 2 through a pipeline to monitor the pH change of the liquid medium in the controllable hydrolysis and aging device 2 in real time and adjust it to a preset value.

[0048] The precursor gas-phase synthesis device 1 is completed by an impinging stream reactor; the controllable hydrolysis and aging device 2 is completed by a conical gas-liquid-solid three-phase fluidized bed reactor; the separation device 3 is completed by a centrifuge; the drying device 4 is completed by a gas-solid fluidized bed reactor.

[0049] SiCl4 and NH3 enter the precursor gas-phase synthesis device 1 in a molar ratio of 1:1 and undergo a violent impact reaction to obtain a mixture powder of a silicon amine precursor and NH4Cl; the mixture powder enters the controllable hydrolysis and aging device 2, hydrolyzes in ammonia water and ages into silica multi-shell hollow microspheres; the ammonia water mixture containing the silica multi-shell hollow microspheres enters the separation device 3 for solid-liquid separation, thereby obtaining wet silica multi-shell hollow microspheres; the wet silica multi-shell hollow microspheres enter the drying device 4 and after drying and baking, an SiO2 multi-shell hollow microsphere product is obtained.

[0050] In this embodiment, the temperature of the precursor gas-phase synthesis device 1 is -30°C; in the controllable hydrolysis and aging device 2, the ammonia water medium maintains a pH of 14, the mass ratio of the ammonia water medium to the mixture of the silicon amine precursor and NH4Cl is 1:1, and the hydrolysis and aging time is 0.5 h; the heating method is resistance heating, the temperature is 10°C, and the fluidizing gas is N2 gas; the drying device 4 is resistance heating, the temperature is 30°C, and the fluidizing gas is Ar gas; the pH monitoring and regulating device 5 dynamically inputs NH3 into the hydrolysis medium.

[0051] Through TEM and infrared analysis, the obtained product is an SiO2 multi-shell hollow microsphere powder with a particle size of about 3.5 μm, 8 layers, and a porosity of about 0.85.

[0052] Example 2

[0053] As Figure 2 shown, a system for preparing SiO2 multi-shell hollow microsphere powder with adjustable porosity, the system includes a precursor gas-phase synthesis device 1, a controllable hydrolysis and aging device 2, a separation device 3, a drying device 4, and a pH monitoring and regulating device 5;

[0054] The precursor gas-phase synthesis device 1, the separation device 3, the controllable hydrolysis and aging device 2, and the drying device 4 are connected in sequence through pipelines, and the pH monitoring and regulating device 5 is connected to the controllable hydrolysis and aging device 2 through a pipeline to monitor the pH change of the liquid medium in the controllable hydrolysis and aging device 2 in real time and adjust it to a preset value.

[0055] The precursor gas-phase synthesis device 1 is completed by a fluidized bed reactor; the controllable hydrolysis and aging device 2 is completed by a fixed bed reactor; the separation device 3 is completed by a gas-solid fluidized bed reactor; the drying device 4 is completed by a heat pump dryer.

[0056] A mixture of SiH2Cl2 and SiH3Br enters the precursor gas-phase synthesis device 1 with ammonia in a molar ratio of 1:10 to react to obtain a mixture powder of a silazane precursor and NH4Cl and NH4Br; the mixture powder and ethylenediamine enter the separation device 3 together, and NH4Cl and NH4Br are dissolved in ethylenediamine and discharged through filtration, thereby obtaining a pure silazane precursor powder; the pure silazane precursor powder enters the controllable hydrolysis and aging device 2, and a mixture of NH3·H2O and H2O enters together to cause the silazane precursor to undergo hydrolysis and aging during the fluidization process, spontaneously forming silica multi-shell hollow microspheres; the wet silica multi-shell hollow microspheres enter the drying device 4 and after drying and baking, a SiO2 multi-shell hollow microsphere product is obtained.

[0057] In this embodiment, the heating method of the precursor gas-phase synthesis device 1 is conventional resistance heating, the reaction temperature is 100 °C, and the fluidizing gas is NH3; the separation device 3 is resistance heating, the temperature is 350 °C, and the fluidizing gas is H2 gas. In the controllable hydrolysis and aging device 2, pH = 10, the mass ratio of the ammonia medium to the mixture of the silazane precursor and NH4Cl is 1:30, and the hydrolysis and aging time is 20 h; the heating method is resistance heating, the temperature is 25 °C; the drying device 4 is resistance heating, the temperature is 40 °C; the pH monitoring and adjusting device 5 dynamically inputs HCl gas into the controllable hydrolysis and aging device 2.

[0058] Through TEM and infrared analysis, the obtained product is a SiO2 multi-shell hollow microsphere powder with a particle size of about 2.0 μm, 2 layers, and a porosity of about 0.05.

[0059] Example 3

[0060] As Figure 3 shown, a system for preparing SiO2 multi-shell hollow microsphere powder with adjustable porosity, the system includes a controllable hydrolysis and aging device 2, a separation device 3, a drying device 4, and a pH monitoring and adjusting device 5;

[0061] The controllable hydrolysis and aging device 2, the separation device 3, and the drying device 4 are connected in sequence through pipelines, and the pH monitoring and adjusting device 5 is connected to the controllable hydrolysis and aging device 2 through a pipeline to monitor the pH change of the liquid medium in the controllable hydrolysis and aging device 2 in real time and adjust it to a preset value.

[0062] The controllable hydrolysis and aging device 2 is completed by a stirring reaction tank; the separation device 3 is completed by a sedimentation tank; the drying device 4 is completed by a fixed reaction bed.

[0063] A mixed gas of SiH3Cl and SiHBr3 enters the controllable hydrolysis aging device 2 together with ammonia water in a molar ratio of 1:30. Ammonia reacts with SiH3Cl and SiHBr3 first to form a silicon amine precursor and a mixture of NH4Cl and NH4Br, and then undergoes hydrolysis aging to spontaneously form silica multi-shell hollow microspheres. The mixed solution containing the silica multi-shell hollow microspheres enters the separation device 3 for static filtration to achieve solid-liquid separation, and wet silica multi-shell hollow microspheres are obtained. The wet silica multi-shell hollow microspheres enter the drying device 4 and are dried to obtain SiO2 multi-shell hollow microsphere products.

[0064] In this embodiment, the hydrolysis medium in the controllable hydrolysis aging device 2 is a mixed medium of ammonia water and ethanol (mass ratio 2:3), pH = 8. The ratio of the mixed powder of the silicon amine precursor and NH4Cl to the mixed hydrolysis medium of ammonia water and ethanol is 1:100. The hydrolysis aging time is 48 h, the heating method is conventional resistance heating, and the reaction temperature is 40 °C. The drying device 4 is resistance heated at a temperature of 60 °C. The pH monitoring and adjustment device 5 dynamically inputs hydrochloric acid solution into the controllable hydrolysis aging device 2.

[0065] Through TEM (as Figure 4 shown) and infrared analysis, the obtained product is a powder of SiO2 multi-shell hollow microspheres with a particle size of about 1 μm, 6 layers, and a porosity of about 0.5.

[0066] The upper and lower limit values and interval values of the process parameters (such as temperature, time, etc.) of the present invention can all implement this method, and the embodiments are not listed one by one here.

[0067] The content not detailed in the present invention can all adopt the conventional technical knowledge in the art.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the embodiments, those of ordinary skill in the art should understand that any modification or equivalent replacement of the technical solutions of the present invention does not depart from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing SiO2 multi-shell hollow microsphere powder with adjustable porosity, the method comprising: Precursor synthesis: Halosilanes and ammonia are reacted at a molar ratio of 1:1 to 1:30 at -30 to 100°C to obtain a mixture of silylamine precursor and ammonium halide; Hydrolysis and aging: placing a mixture of a silane precursor and an ammonium halide in a liquid medium, and controlling the hydrolysis and aging within a certain pH and temperature range to obtain a silicate multi-shell microsphere powder solution; Separation and drying: The silicic acid multi-shell microsphere powder solution is solid-liquid separated, and then dried to obtain SiO2 multi-shell hollow microsphere powder with a specific porosity.

2. The method according to claim 1, characterized in that The halosilane is SiCl x H 4-x and / or SiBr x H 4-x , 0≤x≤4; The particle size of the SiO2 multi-shell hollow microsphere powder with a specific porosity is 1 to 3.5 microns, the porosity is 0.05 to 0.85, and the number of layers ranges from 2 to 8.

3. The method according to claim 1, characterized in that In the hydrolysis aging, the mass ratio of the liquid medium to the mixture is 1:1 to 1:100; The liquid medium is one or at least two of ammonia water, water and ethanol.

4. The method according to claim 1, characterized in that: In the hydrolysis and aging, the hydrolysis temperature is 10-40°C, the pH range is 8-14, and the aging time is 0.5-48h; in the separation and drying, the drying temperature is 30-60°C.

5. The method according to claim 1, characterized in that In the separation, an impurity remover is added to the silicate multi-shell microsphere powder solution, and then solid-liquid separation is performed; the impurity remover is liquid ammonia and / or ethylenediamine.

6. The method according to claim 1, characterized in that In the hydrolysis aging, the acidic medium for pH adjustment is HCl gas and / or hydrochloric acid solution; the alkaline medium is one or at least two of ammonia water, ammonia gas, NaOH solution and KOH solution.

7. A system for preparing SiO2 multi-shell hollow microsphere powder with adjustable porosity, characterized in that: The system comprises a controllable hydrolysis and aging device (2), a separation device (3), a drying device (4), and a pH monitoring and adjustment device (5); The controllable hydrolysis and aging device (2), the separation device (3) and the drying device (4) are connected in sequence, and the pH monitoring and adjusting device (5) is connected to the controllable hydrolysis and aging device (2) to monitor the pH change of the liquid medium in the controllable hydrolysis and aging device (2) in real time and adjust the pH to a preset value; or, The separation device (3), the controllable hydrolysis and aging device (2) and the drying device (4) are connected in sequence, and the pH monitoring and adjustment device (5) is connected to the controllable hydrolysis and aging device (2) to monitor the pH change of the liquid medium in the controllable hydrolysis and aging device (2) in real time and adjust it to a preset value.

8. The system according to claim 7, characterized in that The system further comprises a precursor gas phase synthesis device (1), wherein the precursor gas phase synthesis device (1) is connected to a controllable hydrolysis and aging device (2) or a separation device (3).

9. The system according to claim 7 or 8, characterized in that: The reactor of the precursor gas phase synthesis device (1) is a fluidized reactor, a fixed reaction bed or an impinging flow reactor; the controlled hydrolysis and aging device (2) is a fluidized reactor, a fixed reaction bed or a stirred reaction tank; the separation device (3) is a sedimentation tank, a centrifuge or a filter; the drying device (4) is a heat pump dryer, a fluidized reactor or a fixed reaction bed; the pH monitoring and adjustment device (5) is composed of a pH detector, an acidic medium replenishing device and an alkaline medium replenishing device.

10. The system according to claim 9, characterized in that The fluidizing gas of the fluidized reactor is one of N2, H2, NH3, NH3·H2O, H2O and Ar, or a mixed gas of any two or more thereof.

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