A visualization system and method for synthesizing nano-composite zirconia and its core-shell structure

Abstract

The present invention discloses a visualization system and method for synthesizing nanocomposite zirconium oxide and its core-shell structure, comprising a mixing and material conveying unit, a heat recycling unit, a multi-stage visualization reaction unit, and a post-processing unit. The setting of the first-stage visualization reactor can observe the phase behavior and crystallization evolution process between the precursor, alkali, and supercritical water in situ, and clarify the crystallization mechanism of zirconium oxide nanoparticles; the setting of the second-stage visualization reactor can observe the preparation of the core-shell structure in situ, predict its behavior law, and reduce the consumption of valuable materials; by using high-grade heat for preheating unreacted water or solvent, and low-grade heat for waste liquid post-processing and drying nanoparticles, energy level matching is achieved as much as possible during the utilization process, thereby improving the thermal efficiency of the system. The design of the entire system integrates visualization and energy recycling functions into one, providing certain conditions for large-scale batch production of nanocomposite zirconium oxide and accelerating the industrialization process.

Description

Technical Field

[0001] The present invention belongs to the field of energy chemical preparation technology, and relates to a visualization system and method for synthesizing nano-composite zirconia and its core-shell structure, specifically a multi-segment visualization system and method for supercritical hydrothermal and solvent thermal synthesis of nano-composite zirconia and its core-shell structure. Background Art

[0002] The design of metal oxide nanoparticles is crucial for obtaining highly functional materials with tunable properties. Nanosizing and controlling the crystal growth of metal oxide materials opens up new possibilities in catalysis, biosensing, electrochemical sensing, and drug delivery. Zirconia is currently considered a promising matrix for the design and fabrication of innovative nanomaterials due to its excellent mechanical properties (fracture toughness and strength), thermal stability (low thermal conductivity, suitable thermal expansion coefficient), and catalytic potential. Zirconia consists of three crystalline phases: monoclinic, tetragonal, and cubic. Monoclinic zirconia reversibly transforms to the tetragonal phase upon heating to approximately 1170°C, and the tetragonal phase transforms to the cubic phase at temperatures exceeding 2370°C. There are two approaches to stabilizing the high-temperature phase. First, zirconia can be nanosized. Studies have shown that the cubic and tetragonal phases exhibit significant size effects. When the particles are smaller than a certain size, the tetragonal and cubic phases can be stabilized at room temperature. Second, ion doping can be used to create oxygen vacancies. Low doping levels can stabilize the tetragonal and cubic phases, while high doping levels can alter the crystal composition to synthesize zirconia-based composites. The particularity of different crystal forms enables nano-zirconia and zirconia-based composites to be used in various fields such as catalysts, thermal barrier coatings, denture materials, mobile phone back panels, solid fuel cell electrolytes, etc.

[0003] Core / shell nanoparticles can be broadly defined as structures consisting of a core (inner material) and a shell (outer material). This includes some hollow structures. The purpose of core / shell materials encompasses a combination of improved functionality, stability, and dispersibility, controlled core release, and reduced consumption of valuable materials. While there are various core / shell structures, recent developments have increased demand for inorganic / inorganic types, with the primary materials bound to zirconia being metals (e.g., Ag) and oxides such as Y2O3, CeO2, and SiO2. Zirconia core / shell structures can be formed by synthesizing a zirconia core followed by a shell of other materials.

[0004] Current methods for synthesizing nanozirconia include sol-gel, chemical coprecipitation, and spray pyrolysis. While these methods can produce micron- and nanoscale zirconia, they suffer from numerous drawbacks, including slow reaction rates, complex and time-consuming processes, and high energy consumption (calcination is required to remove some impurities). Furthermore, the synthesis of core-shell structures is complex, often batch-wise, or even impossible. Therefore, a simple, fast, and cost-effective method for synthesizing core-shell structures is urgently needed. Continuous supercritical hydrothermal and solvothermal synthesis methods can obtain crystalline materials directly from aqueous solutions by cleverly controlling parameters. As the temperature increases, metal oxides such as zirconia rapidly precipitate due to their low solubility at higher temperatures. Furthermore, the continuous synthesis of core-shell structures requires only the addition of a single precursor, offering advantages such as high efficiency, low cost, controllable reactions, and environmental friendliness.

[0005] However, there are still many problems in the process of synthesizing nanocomposite zirconia:

[0006] (1) Under harsh conditions of high temperature and high pressure, it is difficult to explore the phase behavior and crystallization evolution process between precursors, alkali and supercritical water. Therefore, the crystallization mechanism of zirconia nanoparticles is still ex situ speculation and cannot be observed in situ.

[0007] (2) In the traditional zirconia synthesis system, the preparation of core-shell structure is not considered, let alone its visualization, which makes it impossible to predict its behavior, reduce the consumption of valuable materials, and provide theoretical guidance for its latest development.

[0008] (3) In the heating and pressure increasing unit and the cooling and pressure decreasing unit, the heat of the high-temperature fluid is directly dissipated, resulting in a large amount of energy waste and increasing the operating cost of the system. Summary of the Invention

[0009] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a visualization system and method for synthesizing nano-composite zirconia and its core-shell structure, which can effectively solve the technical problems that the existing preparation process cannot be visualized in situ, has poor heat utilization, and cannot continuously prepare core-shell structured zirconia products.

[0010] In order to achieve the above object, the present invention adopts the following technical solutions:

[0011] The present invention discloses a visualization system for synthesizing nano-composite zirconium oxide and its core-shell structure, comprising a mixing and material conveying unit, a heat recycling unit, a multi-stage visualization reaction unit and a post-processing unit;

[0012] The mixing and material delivery unit includes a primary precursor storage tank, a solvent storage tank, an additive storage tank and a secondary precursor storage tank. The outlet pipelines of the primary precursor storage tank, the solvent storage tank, the additive storage tank and the secondary precursor storage tank are respectively provided with a high-pressure pump 1, a high-pressure pump 2, a high-pressure pump 3 and a high-pressure pump 4. A branch line is also provided on the pipeline between the primary precursor storage tank and the high-pressure pump 1, and a composite storage tank is arranged on the branch line.

[0013] The heat recovery unit includes a preheater, a heater, a cooling unit and a slow cooling unit. The outlet of the second high-pressure pump is divided into two paths, one of which is connected to the preheater and the other is connected to the heater. The outlet of the preheater is divided into two paths, the hot side outlet is connected to the heater and the cold side outlet is connected to the cooling unit. The outlet of the cooling unit is divided into two paths, one of which is connected to the slow cooling unit and the other returns to the preheater. The slow cooling unit is connected to the post-processing unit.

[0014] The multi-stage visualization reaction unit includes a mixing unit, a first-level visualization reactor for observing the synthesis of pure zirconia, and a second-level visualization reactor for observing the synthesis of core-shell structured nano-zirconia. The inlet of the first-level visualization reactor is connected to the outlet of the mixing unit. The second-level visualization reactor includes two inlets, one inlet is connected to the outlet of the first-level visualization reactor, and the other inlet is connected to high-pressure pump four. Each level of the visualization reactor is connected to the display. The mixing unit is provided with three inlets, one side inlet is connected to the heater outlet, and the other two side inlets are respectively connected to the outlets of high-pressure pump one and high-pressure pump three.

[0015] Preferably, a pH value online monitoring unit is also provided on the mixing unit, a flow meter 1 is provided on the pipeline between valve 1 and high-pressure pump 3, a flow meter 2 is provided on the outlet pipeline of the composite storage tank, and the pH value online monitoring unit is interlocked with flow meters 1 and 2.

[0016] Preferably, the first-level visualization reactor and the second-level visualization reactor have the same structure, including an explosion-proof sleeve, a visualization reaction tube is provided in the explosion-proof sleeve, the upper part of the visualization reaction tube is connected to the upper pipe through an upper flange, and the lower part of the visualization reaction tube is connected to the lower pipe through a lower flange; a visual window and a light source window are provided on the visualization reaction tube, and the visual window and the light source window are distributed at a coaxial right angle, and a camera is nested at the same axial position of the visual window.

[0017] More preferably, the visualization reaction tube is not limited to transparent materials such as quartz tubes and sapphire glass tubes that are resistant to high temperature and high pressure.

[0018] Further preferably, the explosion-proof sleeve is formed by fastening and butting two semi-cylindrical metal shells or ceramic shells, and a heat-insulating layer is provided inside the explosion-proof sleeve.

[0019] More preferably, the material of the insulation layer is not limited to ceramic fiber blanket, aluminum silicate felt, silicon carbide fiber, aerogel felt, glass wool, rock wool, expanded perlite, foamed cement, etc., which have thermal insulation effects.

[0020] Preferably, the post-processing unit includes a pressure reduction unit, a gas-liquid separation unit, a solid-liquid separation unit, a drying unit and a composite zirconium oxide nanomaterial storage unit connected in sequence; the inlet of the pressure reduction unit is connected to one outlet of the slow cooling unit, the other outlet of the slow cooling unit is connected to the drying unit through a waste liquid treatment unit, and the other outlet of the drying unit is connected to the slow cooling unit, and a waste gas treatment unit is also provided on one branch of the gas-liquid separation unit.

[0021] Further preferably, the waste liquid treatment unit adopts forward osmosis, RO reverse osmosis, ultrafiltration membrane, falling film evaporation or triple effect evaporation; the drying unit adopts forced air drying, vacuum drying or freeze drying.

[0022] Preferably, the high-pressure pump one, high-pressure pump two, high-pressure pump three and high-pressure pump four can be diaphragm or piston high-pressure pumps, and the composite storage tank is not limited to two or more; the heater is not limited to electromagnetic heaters, infrared heaters or resistance heaters; the mixing unit is not limited to T-type three-way mixers, sleeve-type countercurrent mixers and cross-type jet mixers; the heat exchange form of the preheater, cooling unit and slow cooling unit is not limited to coil type or sleeve type.

[0023] The present invention also discloses a method for synthesizing nano-composite zirconia and its core-shell structure using a visualization system, which comprises the following steps:

[0024] 1) After mixing the zirconium precursor (such as zirconyl nitrate, zirconium acetate, zirconium nitrate, zirconium oxychloride, etc.) stored in the primary precursor storage tank and the ligand and stabilizer stored in the composite storage tank, the pressure is increased by a high-pressure pump to reach the critical pressure value of supercritical hydrothermal synthesis to obtain the pressurized material, which is then pumped into the mixing unit. At the same time, the alkaline solution in the additive storage tank is pressurized by a high-pressure pump and then pumped into the mixing unit;

[0025] 2) Close valve three and open valve four. The solvent in the solvent storage tank is pressurized by high-pressure pump two and pumped into the heater. After the solvent is heated to the supercritical temperature, it is transported to the mixing unit and fully mixed with the precursor mixture and the alkaline solution. Open valve three and close valve four. The unheated solvent enters the preheater for preheating. After preheating, it enters the heater for supplementary heating to reach the supercritical state and is also mixed with the alkaline solution and the precursor mixture in the mixing unit.

[0026] 3) The reaction liquid mixed in step 2) enters a primary visualization reactor to undergo hydrolysis and dehydration reactions to synthesize a nano-zirconia particle suspension, and an image or video of the reaction process is displayed on a display;

[0027] 4) The nano-zirconia particle suspension and the precursor stored in the secondary precursor storage tank are transported to the secondary visualization reactor via a high-pressure pump 4 for reaction to generate nano-zirconia with a core-shell structure, and images or videos of the reaction process are displayed on a display screen;

[0028] 5) The core-shell nano-zirconia suspension synthesized in step 4) is transported to a post-processing unit after passing through a cooling unit and a slow cooling unit for treatment; wherein the heat of the hot fluid in the cooling unit is used to preheat the cold fluid in the preheater, and the waste heat in the slow cooling unit provides steam and drying heat for the post-processing unit.

[0029] Preferably, in step 3), the reaction liquid mixed in step 2) is subjected to hydrolysis and dehydration reactions in a primary visual reactor, the pH value online monitoring unit and the flow meter 1 are started to be interlocked, and the pH value is adjusted by adjusting the proportion of the alkaline solution so that the mixed liquid reaches acidity, neutrality and alkalinity respectively, thereby achieving stable regulation of the crystal phases of the tetragonal phase and cubic phase of nano-composite zirconia.

[0030] Preferably, the post-processing unit includes a depressurization unit, a gas-liquid separation unit, a solid-liquid separation unit, a drying unit and a composite zirconium oxide nanomaterial storage unit connected in sequence; wherein:

[0031] In step 5), the solid-liquid-gas three-phase products enter the gas-liquid separation unit and are divided into two paths. The gas enters the waste gas treatment unit, and the liquid and solid enter the solid-liquid separation unit and are divided into two paths again. The liquid phase enters the waste liquid treatment unit, and the solid phase enters the drying unit and the composite zirconia nanomaterial storage unit.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The visualization system for synthesizing nano-composite zirconia and its core-shell structure disclosed in the present invention is equipped with a mixing and material conveying unit, a heat recovery unit, a multi-stage visualization reaction unit and a post-processing unit. On the one hand, the multi-stage visualization reaction unit corresponds to different reaction stages of synthesizing nano-composite zirconia, including a visualization reactor that can observe the phase behavior and crystallization evolution process between precursors, alkali solution and supercritical water in situ (which can clarify the crystallization mechanism of zirconia nanoparticles), and a visualization reactor that can observe the preparation of core-shell structures in situ (which can predict behavioral patterns and reduce the consumption of valuable materials). On the other hand, the heat recovery unit uses high-grade heat for preheating unreacted water or solvent through a preheater, while low-grade heat is used for post-reaction treatment (including waste liquid post-treatment and drying of nanoparticles). In the process of utilizing thermal energy, energy level matching is achieved as much as possible, thereby improving the thermal efficiency of the system, reducing operating costs, and saving energy. Therefore, the system disclosed in the present invention integrates visualization and energy recovery functions into one, which can effectively solve the technical problems of the existing preparation process that cannot be visualized in situ and the poor heat utilization rate. At the same time, it can continuously prepare core-shell structured zirconia products based on the prepared nano-composite zirconia. The design of the entire system provides good reaction conditions for large-scale production of nano-composite zirconia and its core-shell structure products, thereby accelerating its industrialization process. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the structure of the visualization system for synthesizing nanocomposite zirconia and its core-shell structure according to the present invention;

[0035] Figure 2 This is the main view of the internal structure of the first-level visual reactor;

[0036] Figure 3 This is a top view of the internal structure of the first-level visualization reactor.

[0037] Among them: V1 is valve one; V2 is valve two; V3 is valve three; V4 is valve four; V5 is valve five; FIC1 is flow meter one; FIC2 is flow meter two.

[0038] 1 is the first-stage precursor storage tank; 2 is the solvent storage tank; 3 is the additive storage tank; 4 is the second-stage precursor storage tank; 5 is the composite storage tank; 6 is the high-pressure pump 1; 7 is the high-pressure pump 2; 8 is the high-pressure pump 3; 9 is the high-pressure pump 4; 10 is the preheater; 11 is the heater; 12 is the mixing unit; 13 is the pH value online monitoring unit; 14 is the first-stage visual reactor; 14-1 is the upper connecting pipe; 14-2 is the upper flange; 14-3 is the visual reaction tube; 14-4 is the light source window; 14- 5 is a visual window; 14-6 is a camera; 14-7 is an insulation layer; 14-8 is a lower flange; 14-9 is an explosion-proof sleeve; 14-10 is a lower connecting pipe; 15 is a secondary visual reactor; 16 is a display; 17 is a cooling unit; 18 is a slow cooling unit; 19 is a pressure reduction unit; 20 is a gas-liquid separation unit; 21 is a waste gas treatment unit; 22 is a solid-liquid separation unit; 23 is a waste liquid treatment unit; 24 is a drying unit; 25 is a composite zirconia nanomaterial storage unit. DETAILED DESCRIPTION

[0039] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0040] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0041] The present invention is described in further detail below with reference to the accompanying drawings:

[0042] See also Figure 1 The present invention discloses a visualization system for synthesizing nanocomposite zirconium oxide and its core-shell structure, comprising a mixing and material conveying unit, a heat recycling unit, a multi-stage visualization reaction unit, and a post-processing unit;

[0043] The composite preparation and material conveying unit includes several storage tanks, high-pressure pumps, flow meters and valves, among which the first-level precursor storage tank 1, solvent storage tank 2, additive storage tank 3, and second-level precursor storage tank 4 are respectively connected to high-pressure pump 1 6, high-pressure pump 2 7, high-pressure pump 3 8 and high-pressure pump 4 9 through pipelines. The composite storage tank 5 is located between the first-level precursor storage tank 1 and high-pressure pump 1 6, and a valve five V5 is provided at the outlet of high-pressure pump 4 9.

[0044] The heat recovery unit includes a preheater 10, a heater 11, a cooling unit 17 and a slow cooling unit 18. The outlet of the high-pressure pump 7 is divided into two paths, one path enters the preheater 10 through valve 3 V3, and the other path enters the heater 11 through valve 4 V4.

[0045] The multi-stage visual reaction unit includes a mixing unit 12, a pH value online monitoring unit 13, a primary visual reactor 14, a secondary visual reactor 15 and a display 16, wherein the primary visual reactor 14 and the secondary visual reactor 15 have the same structure. Figure 2 and Figure 3 As shown, it includes an upper connecting pipe 14-1, an upper flange 14-2, a visualization reaction tube 14-2, a light source window 14-4, a visual window 14-5, a camera 14-6, an insulation layer 14-7, a lower flange 14-8, an explosion-proof sleeve 14-9 and a lower connecting pipe 14-10.

[0046] The pressure reduction unit 19, gas-liquid separation unit 20, solid-liquid separation unit 22, drying unit 24 and composite zirconium oxide nanomaterial storage unit 25 in the post-processing unit are connected end to end in sequence, the waste gas treatment unit 21 is placed on another branch of the gas-liquid separation unit 20, and the waste liquid treatment unit 23 is placed on another branch of the solid-liquid separation unit 22.

[0047] Preferably, a valve V1 and a flow meter FIC1 are sequentially provided on the pipeline between the additive storage tank 3 and the high-pressure pump 3 8, a valve V2 and a flow meter FIC2 are sequentially provided on the pipeline between the outlet of the composite storage tank 5 and the high-pressure pump 1 6, and the pH value online monitoring unit 13 is interlocked with the flow meter FIC1 and the flow meter FIC2.

[0048] Preferably, the preheater 10 includes two inlets and two outlets, the cold side inlet of which is connected to the high-pressure pump 2 7, and a valve 3 V3 is provided on the connected pipeline, the hot side inlet of which is connected to the hot side outlet of the cooling unit 17, the cold side outlet of which is connected to the cold side inlet of the cooling unit 17, and the hot side outlet of which is connected to the inlet end of the heater 11.

[0049] Preferably, the primary visualization reactor 14 and the secondary visualization reactor 15 are connected to a display 16 respectively.

[0050] Preferably, the secondary visualization reactor 15 includes two inlets, one inlet is connected to the high-pressure pump 29 9, a valve 5 V5 is provided on the branch line, and the other inlet is connected to the primary visualization reactor 14.

[0051] Preferably, see Figure 2 and Figure 3 In the first-level visualization reactor 14, the upper and lower parts of the visualization reaction tube 14-3 are fastened and connected to the upper connecting pipe 14-1 and the lower connecting pipe 14-10 respectively through the upper flange 14-2 and the lower flange 14-8. The visual window 14-5 and the light source window 14-4 are located on any horizontal plane of the visualization reaction tube 14-3, and are coaxially distributed at a 90-degree angle. The camera 14-6 is nested in the same axial position of the visual window 14-5.

[0052] Preferably, the first-level visualization reactor 14 is based on an explosion-proof sleeve 14-9 as a skeleton. The explosion-proof sleeve 14-9 is formed by two semi-cylindrical metal shells or ceramic shells fastened together, and is filled with a thermal insulation layer 14-7 of not limited to one or more layers. The material of the thermal insulation layer 14-7 is not limited to ceramic fiber blanket, aluminum silicate felt, silicon carbide fiber, aerogel felt, glass wool, rock wool, expanded perlite, foamed cement, etc. with thermal insulation effect.

[0053] Preferably, the interior of the secondary visualization reactor 15 is exactly the same as that of the primary visualization reactor. The visualization reactor of the entire system is not limited to two or more stages, and the visualization reaction tube 14-3 is not limited to transparent materials resistant to high temperature and high pressure such as quartz tubes and sapphire glass tubes.

[0054] Preferably, high-pressure pump 1 6, high-pressure pump 2 7, high-pressure pump 3 8 and high-pressure pump 4 9 can be selected as diaphragm or piston high-pressure pumps, and the composite storage tank 5 is not limited to two or more; the heater 11 is not limited to electromagnetic heaters, infrared heaters or resistance heaters; the mixing unit 12 is not limited to T-type three-way mixers, sleeve countercurrent mixers and cross-type jet mixers; the heat exchange form of the preheater 10, cooling unit 17 and slow cooling unit 18 is not limited to coil type or sleeve type; the treatment form of the waste liquid treatment unit 23 is not limited to forward osmosis, RO reverse osmosis, ultrafiltration membrane, falling film evaporation, triple effect evaporation, etc.; the form of the drying unit 24 is not limited to forced air drying, vacuum drying and freeze drying, etc.

[0055] The multi-stage visualization system for supercritical hydrothermal and solvothermal synthesis of nanocomposite zirconia of the present invention can visualize the synthesis process of pure acidic, neutral, and alkaline zirconia and the corresponding core-shell structures, as described in detail below:

[0056] Example 1

[0057] When the system needs to observe the synthesis process of pure zirconium oxide, valve five V5 is closed. At this time, the precursor in the secondary precursor storage tank 4 (single solution or mixed solution of metal or non-metal such as yttrium precursor, lanthanum precursor, cerium precursor, silver precursor, silicon precursor, etc.) cannot be transported by the high-pressure pump four 9. The secondary visualization reactor 15 can extend the reaction time of synthesizing pure zirconium oxide, making it convenient to observe the crystallization behavior.

[0058] Zirconium-based precursors (zirconium oxynitrate, zirconium acetate, zirconium nitrate, zirconium oxychloride, etc.) are stored in the primary precursor storage tank 4, and one or more ligands such as PVP, EDTA and one or more stabilizers such as yttrium salts, lanthanum salts, and cerium salts are stored in the composite storage tank 5. After the two are mixed, they are pressurized by a high-pressure pump 6 to reach the critical pressure value of supercritical hydrothermal synthesis. The pressurized materials are pumped into the mixing unit 12. At the same time, the alkaline solution in the additive storage tank 3, such as sodium hydroxide, potassium hydroxide, ammonia water, etc., which can provide hydroxide ions, is pumped into the mixing unit 12 after being pressurized by a high-pressure pump 3 8.

[0059] During the initial operation of the system, valve four V4 is opened, and the pure water or other solvent in the solvent storage tank is pressurized by high-pressure pump two 7 and then pumped into the heater 11. The pure water or other solvent is quickly heated to the supercritical temperature and then mixed with the alkaline solution and the precursor mixture in the mixing unit 12; when the system is operating normally, valve four V4 is closed and valve three V3 is opened, and the unheated pure water or other solvent enters the preheater 10 for preheating, and after preheating, enters the heater 11 for supplementary heating to reach the supercritical state and is also mixed with the alkaline solution and the precursor mixture in the mixing unit 12. The mixer form is not limited to countercurrent mixing, cross-jet mixing, and other elements that can increase the mixing area and improve the mixing efficiency.

[0060] The mixed liquid undergoes hydrolysis and dehydration reactions in the first-level visualization reactor 14 and the second-level visualization reactor 15. Since the nucleation mechanism of zirconium oxide is different under acidic, neutral and alkaline conditions, the tetragonal phase or cubic phase can be completely stabilized by adding stabilizers and ligands. The pH value is adjusted by adjusting the proportion of alkali through the linkage of the pH value online monitoring unit 13 and the flow meter FIC1 so that the pH value reaches acidic, neutral and alkaline respectively. When the pH value in the pH value online monitoring unit 13 reaches the maximum value, the tetragonal phase or cubic phase cannot be completely stabilized. The linkage with the flow meter FIC1 is opened, and the proportion of stabilizer and ligand is increased to achieve stable tetragonal phase or cubic phase. In the first-level visualization reactor 14 and the second-level visualization reactor 15, the camera 14-6 records the images and videos of the process and transmits them to the display 16.

[0061] The synthesized pure zirconium oxide suspension passes through the cooling unit 17, slow cooling unit 18, and pressure reduction unit 19 to achieve temperature and pressure reduction. The solid-liquid-gas three-phase product enters the gas-liquid separation unit 20 and is divided into two paths. The gas enters the waste gas treatment unit 21, and the liquid and solid enter the solid-liquid separation unit 22 and are further divided into two paths. The liquid phase enters the waste liquid treatment unit 23, and the solid phase enters the drying unit 24 and the composite zirconium oxide nanomaterial storage unit 25. The heat of the hot fluid in the cooling unit 17 is used to preheat the cold fluid in the preheater 10. The waste heat in the slow cooling unit 18 is passed through the waste liquid treatment unit 23 and the drying unit 24 to provide steam and drying heat, respectively.

[0062] Example 2

[0063] When the system needs to simultaneously observe the synthesis of pure zirconium oxide and the reaction process of the core-shell structure, valve five V5 is opened. At this time, the precursor in the secondary precursor storage tank 4 (single solution or mixed solution of metal or non-metal such as yttrium precursor, lanthanum precursor, cerium precursor, silver precursor, silicon precursor, etc.) is transported to the secondary visualization reactor 15 through the high-pressure pump four 9.

[0064] Its initial operation process is consistent with that of Example 1. The mixture of the alkaline solution, the precursor mixture and pure water or other solvents undergoes hydrolysis and dehydration reactions in the primary visualization reactor 14. Since the nucleation mechanism of zirconium oxide is different under acidic, neutral and alkaline conditions, the tetragonal phase or cubic phase can be completely stabilized by adding stabilizers and ligands. The pH value is adjusted by adjusting the proportion of alkali through the linkage of the pH value online monitoring unit 13 and the flow meter FIC1 so that the pH value of the mixture reaches acidic, neutral and alkaline conditions respectively. When the pH value in the pH value online monitoring unit 13 reaches the maximum value, the tetragonal phase or cubic phase cannot be completely stabilized. The linkage with the flow meter FIC1 is opened, the proportion of stabilizer and ligand is increased, and the tetragonal phase or cubic phase is stabilized. In the primary visualization reactor 14, the camera 14-6 records the images and videos of the process and transmits them to the display 16.

[0065] The precursors in the secondary precursor storage tank (single solutions or mixed solutions of metals or non-metals such as yttrium precursors, lanthanum precursors, cerium precursors, silver precursors, silicon precursors, etc.) enter the secondary visualization reactor 15 simultaneously with the suspension of nano-zirconia single particles through valve five V5, and the core-shell structure formation process is transmitted to the display 16 through the camera 14-6.

[0066] The internal structures of the primary visualization reactor 14 and the secondary visualization reactor 15 are identical. For example, the upper and lower pipes 14-1 and 14-10 of the primary visualization reactor 14 are connected to the system piping. A light source is positioned on the same level as the light source window 14-4, providing light throughout the primary visualization reactor 14. The explosion sleeve 14-9, consisting of two semi-cylindrical metal or ceramic shells fastened together, prevents injury from explosions in the visualization reaction tube 14-3 under high-temperature and high-pressure conditions, thereby enhancing system safety. An insulation layer 14-7, comprised of one or more layers, maintains the internal temperature of the primary visualization reactor 14 and prevents heat loss.

[0067] The synthesized zirconia core-shell structure suspension passes through the cooling unit 17, slow cooling unit 18, and pressure reduction unit 19 to achieve temperature and pressure reduction. The solid-liquid-gas three-phase product enters the gas-liquid separation unit 20 and is divided into two paths. The gas enters the waste gas treatment unit 21, and the liquid and solid enter the solid-liquid separation unit 22 and are further divided into two paths. The liquid phase enters the waste liquid treatment unit 23, and the solid phase enters the drying unit 24 and the composite zirconia nanomaterial storage unit 25. The heat of the hot fluid in the cooling unit 17 is used to preheat the cold fluid in the preheater 10. The waste heat in the slow cooling unit 18 is passed through the waste liquid treatment unit 23 and the drying unit 24 to provide steam and drying heat, respectively.

[0068] In summary, the visualization system for synthesizing nanocomposite zirconium oxide and its core-shell structure disclosed in the present invention can realize the in-situ observation of the supercritical hydrothermal and solvent thermal synthesis of nanocomposite zirconium oxide and its core-shell structure, wherein the setting of the first-level visualization reactor can in-situ observe the phase behavior and crystallization evolution process between the precursor, alkali and supercritical water, and clarify the crystallization mechanism of zirconium oxide nanoparticles; the setting of the second-level precursor path and the second-level visualization reactor can in-situ observe the preparation of the core-shell structure, predict its behavior law, reduce the consumption of valuable materials, and provide theoretical guidance for its latest development. Therefore, the system of the present invention can provide a powerful theoretical guidance for exploring the phase behavior and crystallization evolution process between the precursor, alkali and supercritical water and the behavior law of the core-shell structure and the latest development of the core-shell structure. In addition, the system achieves energy level matching as much as possible in the process of utilizing thermal energy. The high-grade heat is used for preheating unreacted water or solvent through the preheater, while the low-grade heat is used for waste liquid post-treatment and drying nanoparticles. In the process of utilizing thermal energy, energy level matching is achieved as much as possible, improving the thermal efficiency of the system, reducing operating costs, and saving energy. It can be seen that the design of the entire system provides certain conditions for large-scale batch production of nano-composite zirconia and accelerates its industrialization process.

[0069] The above content is only for explaining the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A visualization system for synthesizing nanocomposite zirconium oxide and its core-shell structure, characterized in that: It includes a mixing and material conveying unit, a heat recovery unit, a multi-stage visual reaction unit and a post-processing unit; The mixing and material delivery unit comprises a primary precursor storage tank (1), a solvent storage tank (2), an additive storage tank (3) and a secondary precursor storage tank (4); high-pressure pump 1 (6), high-pressure pump 2 (7), high-pressure pump 3 (8) and high-pressure pump 4 (9) are respectively provided on the outlet pipelines of the primary precursor storage tank (1), the solvent storage tank (2), the additive storage tank (3) and the secondary precursor storage tank (4); a branch line is further provided on the pipeline between the primary precursor storage tank (1) and the high-pressure pump 1 (6); a composite storage tank (5) is provided on the branch line; The heat recovery unit includes a preheater (10), a heater (11), a cooling unit (17) and a slow cooling unit (18). The outlet of the second high-pressure pump (7) is divided into two paths, one path is connected to the preheater (10) through a valve three (V3), and the other path is connected to the heater (11) through a valve four (V4). The outlet of the preheater (10) is divided into two paths, the hot side outlet is connected to the heater (11), and the cold side outlet is connected to the cooling unit (17). The outlet of the cooling unit (17) is divided into two paths, one path is connected to the slow cooling unit (18), and the other path returns to the preheater (10). The slow cooling unit (18) is connected to the post-processing unit. The multi-stage visualization reaction unit includes a mixing unit (12), a first-stage visualization reactor (14) for observing the synthesis of pure zirconium oxide, and a second-stage visualization reactor (15) for observing the synthesis of nano zirconium oxide with a core-shell structure. The inlet of the first-stage visualization reactor (14) is connected to the outlet of the mixing unit (12). The second-stage visualization reactor (15) includes two inlets, one inlet is connected to the outlet of the first-stage visualization reactor (14), and the other inlet is connected to the high-pressure pump four (9). Each stage visualization reactor is connected to the display (16). The mixing unit (12) is provided with three inlets, one inlet is connected to the outlet of the heater (11), and the other two inlets are connected to the outlets of the high-pressure pump one (6) and the high-pressure pump three (8), respectively. A pH value online monitoring unit (13) is also provided on the mixing unit (12). A valve 1 (V1) and a flow meter 1 (FIC1) are provided in sequence on the pipeline between the additive storage tank (3) and the high-pressure pump 3 (8). A valve 2 (V2) and a flow meter 2 (FIC2) are provided in sequence on the pipeline between the outlet of the composite storage tank (5) and the high-pressure pump 1 (6). The pH value online monitoring unit (13) is interlocked with the flow meter 1 (FIC1) and the flow meter 2 (FIC2).

2. The visualization system for synthesizing nanocomposite zirconium oxide and its core-shell structure according to claim 1, characterized in that: The first-stage visualization reactor (14) and the second-stage visualization reactor (15) have the same structure, including an explosion-proof sleeve, a visualization reaction tube is arranged in the explosion-proof sleeve, the upper part of the visualization reaction tube is connected to the upper pipe via an upper flange, and the lower part of the visualization reaction tube is connected to the lower pipe via a lower flange; a visual window and a light source window are provided on the visualization reaction tube, and the visual window and the light source window are coaxially distributed at a right angle, and a camera is nested at the same axial position of the visual window.

3. The visualization system for synthesizing nanocomposite zirconia and its core-shell structure according to claim 2, characterized in that: The explosion-proof sleeve is formed by fastening and butting two semi-cylindrical metal shells or ceramic shells, and a heat-insulating layer is provided inside the explosion-proof sleeve.

4. The visualization system for synthesizing nanocomposite zirconia and its core-shell structure according to claim 1, characterized in that: The post-processing unit comprises a pressure reduction unit (19), a gas-liquid separation unit (20), a solid-liquid separation unit (22), a drying unit (24) and a composite zirconium oxide nanomaterial storage unit (25) which are connected in sequence; the inlet of the pressure reduction unit (19) is connected to one outlet of the slow cooling unit (18), the other outlet of the slow cooling unit (18) is connected to the drying unit (24) via a waste liquid treatment unit (23), the other outlet of the drying unit (24) is connected to the slow cooling unit (18), and a waste gas treatment unit is also provided on one branch of the gas-liquid separation unit (20).

5. The visualization system for synthesizing nanocomposite zirconia and its core-shell structure according to claim 4, characterized in that: The waste liquid treatment unit (23) adopts forward osmosis, RO reverse osmosis, ultrafiltration membrane, falling film evaporation or triple effect evaporation; the drying unit (24) adopts forced air drying, vacuum drying or freeze drying.

6. The visualization system for synthesizing nanocomposite zirconia and its core-shell structure according to any one of claims 1 to 5, characterized in that: The high-pressure pump 1 (6), high-pressure pump 2 (7), high-pressure pump 3 (8) and high-pressure pump 4 (9) are selected from diaphragm high-pressure pumps or piston high-pressure pumps, and the number of the composite storage tanks (5) is multiple; the heater (11) adopts an electromagnetic heater, an infrared heater or a resistance heater; the mixing unit (12) adopts a T-type three-way mixer, a sleeve-type countercurrent mixer or a cross-type jet mixer; the preheater (10), the cooling unit (17) and the slow cooling unit (18) adopt coil heat exchange or sleeve-type heat exchange.

7. A method for synthesizing nanocomposite zirconia and its core-shell structure based on the visualization system for synthesizing nanocomposite zirconia and its core-shell structure according to any one of claims 1 to 6, characterized in that: The following steps are involved: 1) After mixing the zirconium precursor stored in the first-stage precursor storage tank (1) and the ligand and stabilizer stored in the composite storage tank (5), the pressure is increased by a high-pressure pump (6) to reach the critical pressure value of supercritical hydrothermal synthesis to obtain a pressurized material, which is then pumped into a mixing unit (12). At the same time, the alkaline solution in the additive storage tank (3) is pressurized by a high-pressure pump (8) and then pumped into the mixing unit (12); 2) Valve three (V3) is closed, and valve four (V4) is opened. The solvent in the solvent storage tank (2) is pressurized by high-pressure pump two (7) and then pumped into the heater (11). After the solvent is heated to the supercritical temperature, it is transported to the mixing unit (12) and fully mixed with the precursor mixture material and the alkaline solution; Valve three (V3) is opened, and valve four (V4) is closed. The unheated solvent enters the preheater (10) for preheating. After preheating, it enters the heater (11) for supplementary heating to reach the supercritical state and is also mixed with the alkaline solution and the precursor mixture material in the mixing unit (12); 3) The reaction liquid mixed in step 2) enters the first-level visualization reactor (14) to undergo hydrolysis and dehydration reactions to synthesize a nano-zirconia particle suspension, and an image or video of the reaction process is displayed on a display (16); 4) The nano-zirconia particle suspension and the precursor stored in the secondary precursor storage tank (4) are transported to the secondary visualization reactor (15) via a high-pressure pump (9) to react and generate nano-zirconia with a core-shell structure, and an image or video of the reaction process is displayed via a display (16); 5) The nano-zirconia suspension with a core-shell structure synthesized in step 4) is transported to a post-processing unit for processing after passing through a cooling unit (17) and a slow cooling unit (18); wherein the heat of the hot fluid in the cooling unit (17) is used to preheat the cold fluid in the preheater (10), and the waste heat in the slow cooling unit (18) provides steam and drying heat for the post-processing unit.

8. The method for synthesizing nanocomposite zirconium oxide and its core-shell structure according to claim 7, characterized in that: In step 3), the reaction liquid mixed in step 2) is subjected to hydrolysis and dehydration reactions in a first-level visual reactor (14), and the interlocking of the pH value online monitoring unit (13) and the flow meter 1 (FIC1) is started. The pH value is adjusted by adjusting the proportion of the alkaline solution so that the mixed liquid reaches acidity, neutrality and alkalinity respectively, thereby achieving stable control of the crystal phases of the nano-composite zirconia tetragonal phase and cubic phase.

9. The method for synthesizing nanocomposite zirconium oxide and its core-shell structure according to claim 7, characterized in that: The post-processing unit includes a pressure reduction unit (19), a gas-liquid separation unit (20), a solid-liquid separation unit (22), a drying unit (24) and a composite zirconium oxide nanomaterial storage unit (25) which are connected in sequence; wherein: In step 5), the solid-liquid-gas three-phase product enters the gas-liquid separation unit (20) and is divided into two paths. The gas enters the waste gas treatment unit (21), and the liquid-solid enters the solid-liquid separation unit (22) and is further divided into two paths. The liquid phase enters the waste liquid treatment unit (23), and the solid phase enters the drying unit (24) and the composite zirconium oxide nanomaterial storage unit (25).

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