Cerium oxide dispersion and preparation method thereof

Abstract

The present invention provides a cerium oxide dispersion and a preparation method thereof; a pipeline continuous synthesis device is used to prepare the cerium oxide dispersion, and the pipeline continuous synthesis device includes a tubular heat exchanger and a pipeline reactor; the preparation method includes the following steps: heating a mixed solution including a cerium-containing precursor, a pH regulator, water and a dispersion medium to a reaction temperature of a hydrothermal reaction in a tubular heat exchanger; the heated mixed solution is subjected to a hydrothermal reaction in a reaction pipeline of the pipeline reactor to prepare a cerium oxide dispersion; wherein the diameter of the reaction pipeline is 3mm-6mm and the length is 30m-60m. By using a pipeline continuous synthesis device including a tubular heat exchanger and a pipeline reactor to prepare the cerium oxide dispersion, the reaction time is greatly shortened, and the safety of the pipeline reactor is higher than that of a kettle reactor, especially a glass stirred kettle, etc., and the efficiency and safety of the cerium oxide dispersion preparation process are significantly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of inorganic material synthesis, in particular to a cerium oxide dispersion and a preparation method thereof. Background Art

[0002] Due to the presence of oxygen defects on the surface of nano-cerium oxide, cerium presents two valence states and can 3+ and Ce 4+ Reversible conversion between valence states allows for the scavenging of excess free radicals in living organisms. With the advancement of nanosynthesis technology, nanoceria with a variety of morphologies has become possible, including one-dimensional nanorods, nanowires, and nanotubes; two-dimensional nanosheets and nanoplates; nanopolyhedrons, and nanocubes. Common methods, such as solvothermal, template, seed-mediated secondary growth, microwave / ultrasound radiation, and electrochemical deposition, can all be used for the controlled synthesis of nanoceria. The hydrothermal method, in particular, allows for precise control of the morphology and size distribution of nanocrystals, making it an increasingly universal method for synthesizing nanoceria.

[0003] However, the hydrothermal method has poor repeatability, long reaction time, and requires the use of a high-pressure reactor. The reaction process is prone to decomposition and release of gas, which may cause a pressure surge and pose a safety hazard. In addition, the post-processing of the resulting product is relatively difficult, resulting in low efficiency and poor safety of the hydrothermal method for synthesizing nanocerium oxide. Summary of the Invention

[0004] Based on this, it is necessary to provide a cerium oxide dispersion and a preparation method thereof to improve the efficiency and safety of the cerium oxide dispersion preparation process.

[0005] A first aspect of the present invention provides a method for preparing a cerium oxide dispersion, wherein the method is performed using a pipeline continuous synthesis device comprising a tubular heat exchanger and a pipeline reactor. The method comprises the following steps:

[0006] heating a mixture of a cerium-containing precursor, a pH regulator, water, and a dispersion medium to a reaction temperature of a hydrothermal reaction in the tubular heat exchanger;

[0007] The heated mixed solution undergoes a hydrothermal reaction in the reaction tube of the tube reactor to prepare the cerium oxide dispersion;

[0008] The reaction pipe has a diameter of 3 mm to 6 mm and a length of 30 m to 60 m.

[0009] In some embodiments, the tubular heat exchanger includes a preheating pipe with a diameter of 3mm-6mm and a length of 5m-15m.

[0010] In some embodiments, the pipeline continuous synthesis device further comprises a storage tank, a feed pump, a condenser, a temperature controller, a pressure transmitter, and a liquid collecting tank; the storage tank, the feed pump, the tubular heat exchanger, the pipeline reactor, the condenser, and the liquid collecting tank are connected in sequence; the temperature controller is connected to the pipeline reactor, and the pressure transmitter is connected to the condenser;

[0011] The storage tank is used to store the mixed liquid, and the feed pump is used to promote the operation of the mixed liquid and / or the cerium oxide dispersion in the pipeline continuous synthesis device; the condenser is used to cool the product of the hydrothermal reaction; the temperature controller is used to control the temperature of the tubular heat exchanger and the pipeline reactor; the pressure transmitter is used to monitor the pressure of the condenser; and the liquid collecting tank is used to collect the cerium oxide dispersion.

[0012] In some embodiments, the reaction tube and the preheating tube are coils.

[0013] In some embodiments, the reaction temperature of the hydrothermal reaction is 170° C.-210° C., the reaction time is 3 min-15 min, and the back pressure is 0.5 MPa-1.5 MPa.

[0014] In some embodiments, the mixture comprises at least one of the following conditions:

[0015] (1) The cerium-containing precursor includes one or more of cerium nitrate hexahydrate and cerium nitrate;

[0016] (2) The pH adjuster includes one or more of acetic acid, formic acid and propionic acid;

[0017] (3) The dispersion medium includes ethylene glycol;

[0018] (4) The mass proportion of the cerium-containing precursor in the mixed solution is 3%-15%;

[0019] (5) The mass volume ratio of the cerium-containing precursor and the pH adjuster is (200-600) g: (200-600) mL;

[0020] (6) The mass volume ratio of the cerium-containing precursor to the dispersion medium is (200-600) g: (6000-7000) mL;

[0021] (7) The mass volume ratio of the cerium-containing precursor to the water is (200-600) g: (100-200) mL;

[0022] (8) The mass ratio of the cerium-containing precursor, the pH adjuster, the water and the dispersion medium is 1:(0.2-1):(0.5-1):(30-35).

[0023] In some embodiments, the preparation method further comprises:

[0024] The product of the hydrothermal reaction is subjected to solid-liquid separation, the solid matter obtained after the solid-liquid separation is washed with water until it is neutral, and then the solid matter is mixed with water to prepare the cerium oxide dispersion.

[0025] In some embodiments, the cooled product of the hydrothermal reaction is filtered using a ceramic filter membrane;

[0026] Optionally, the average pore size of the ceramic filter membrane is 100 nm-500 nm;

[0027] Optionally, the filtration method is cross-flow filtration.

[0028] The second aspect of the present invention provides a cerium oxide dispersion, which is prepared using the preparation method of the first aspect of the present invention.

[0029] In some embodiments, the cerium oxide dispersion contains cerium oxide nanospheres, and the hydrodynamic radius of the cerium oxide nanospheres is 100 nm-1000 nm.

[0030] The above-mentioned method for preparing cerium oxide dispersion adopts a pipeline continuous synthesis device including a tubular heat exchanger and a pipeline reactor to prepare the cerium oxide dispersion, which greatly shortens the reaction time. In addition, the safety of the pipeline reactor is higher than that of a kettle reactor, especially a glass stirred kettle, etc., and the efficiency and safety of the cerium oxide dispersion preparation process are significantly improved; in addition, the DPPH removal rate of the cerium oxide dispersion can be increased by more than 90%. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A schematic structural diagram of a pipeline continuous synthesis device provided in one embodiment of the present invention;

[0032] Figure 2 The figures are scanning electron micrographs and size distribution diagrams of the cerium oxide nanospheres prepared in Example 1 and Example 7;

[0033] Figure 3 Schematic diagrams of optical microscopy and transmission electron microscopy of the cerium oxide microspheres prepared in Comparative Example 1;

[0034] Figure 4 Schematic diagram of the hydrodynamic radius results of the cerium oxide nanospheres prepared in Example 1 and Example 7 and the cerium oxide microspheres prepared in Comparative Example 1;

[0035] Figure 5 Schematic diagram of the sedimentation stability results of the cerium oxide dispersions prepared in Example 1, Example 7 and Comparative Example 1;

[0036] Figure 6 Schematic diagram of the change in backscattered light intensity in the middle of the cerium oxide dispersions prepared in Example 1, Example 7 and Comparative Example 1;

[0037] Figure 7 Schematic diagram of the sedimentation of the cerium oxide dispersions prepared in Example 1, Example 7 and Comparative Example 1;

[0038] Figure 8 The product results at different reaction times when cerium oxide dispersion was prepared using a reactor;

[0039] Figure 9 Schematic diagram of the DPPH radical scavenging effect of the cerium oxide dispersion in Example 4 and Comparative Example 2. DETAILED DESCRIPTION

[0040] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the accompanying drawings. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the present disclosure.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in this specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0042] In the present invention, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0043] In the present invention, when referring to numerical ranges, unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Furthermore, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges subsumed therein.

[0044] Only certain numerical ranges are specifically disclosed herein. However, any lower limit may be combined with any upper limit to form an unspecified range; and any lower limit may be combined with other lower limits to form an unspecified range, and similarly, any upper limit may be combined with any other upper limit to form an unspecified range. In addition, each individually disclosed point or single value may itself serve as a lower limit or upper limit and be combined with any other point or single value, or with other lower limits or upper limits, to form an unspecified range.

[0045] The temperature parameters in the present invention, unless otherwise specified, allow for either constant temperature treatment or treatment within a certain temperature range. The constant temperature treatment allows for temperature fluctuations within the precision range controlled by the instrument.

[0046] In the description of the invention, “plurality” means at least two, for example, two, three, etc., unless otherwise clearly and specifically defined.

[0047] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form a new technical solution. Unless otherwise specified, all technical features and optional technical features of the present invention can be combined with each other to form a new technical solution.

[0048] Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, but are preferably performed sequentially.

[0049] In the related art, when nano-cerium oxide is prepared by a hydrothermal method, although the morphology and size distribution of the nanocrystals can be precisely controlled, the efficiency is low and the safety is poor.

[0050] Based on the above problems, the present invention provides a method for preparing cerium oxide microspheres, which uses a closed, pressure-resistant pipeline reactor that operates continuously in a plug flow manner to replace an intermittent metal kettle / glass reactor with a large gas phase space on the top, thereby reducing the impact of gas phase overflow on the apparent reaction kinetics, breaking through the limitation of the normal pressure boiling point on the actual reaction temperature, and increasing the reaction temperature while ensuring that the back pressure does not exceed the safe value, thereby improving the reaction efficiency by an order of magnitude.

[0051] A first aspect of the present invention provides a method for preparing a cerium oxide dispersion, wherein the method is performed using a pipeline continuous synthesis device comprising a tubular heat exchanger and a pipeline reactor. The method comprises the following steps:

[0052] heating a mixture of a cerium-containing precursor, a pH regulator, water, and a dispersion medium to a reaction temperature of a hydrothermal reaction in a tubular heat exchanger;

[0053] The heated mixed liquid undergoes a hydrothermal reaction in a reaction pipe of a pipe reactor to prepare a cerium oxide dispersion;

[0054] The diameter of the reaction pipe is 3mm-6mm and the length is 30m-60m.

[0055] The diameter of the reaction pipe is 3mm-6mm; for example, it can be but not limited to 3mm, 3.2mm, 3.5mm, 3.8mm, 4mm, 4.2mm, 4.5mm, 4.7mm, 5mm, 5.2mm, 5.5mm, 5.8mm, 6mm or a range between any two of the above diameters. Examples of diameter intervals between any two diameters include but are not limited to 3.2mm-6mm, 3.5mm-6mm, 3.8mm-6mm, 4mm-6mm, 4.2mm-6mm, 4.5mm-6mm, 4.7mm-6mm, 5mm-6mm, 5.2mm-6mm, 5.5mm-6mm or 5.8mm-6mm. When the diameter of the reaction pipe is within the above range, the material flow rate is moderate, the system pressure can be kept stable, and the probability of pipe blockage caused by material sticking to the wall is reduced.

[0056] The length of the reaction pipe is 30m-60m; for example, it can be, but is not limited to, 30m, 32m, 35m, 38m, 40m, 42m, 45m, 47m, 50m, 52m, 55m, 58m, 60m, or a range between any two of the above lengths. Examples of length intervals between any two lengths include, but are not limited to, 30m-58m, 30m-55m, 30m-52m, 30m-50m, 30m-47m, 30m-45m, 30m-42m, 30m-40m, 30m-38m, 30m-35m, or 30m-32m. When the length of the reaction pipe is within the above range, the actual residence time of the material in the pipe can be close to the theoretical time of "liquid holdup / flow rate", which is conducive to improving the yield.

[0057] The pipeline reactor used in the present invention is sealed, pressure-resistant, and operates continuously in a plug flow mode. In contrast, metal kettles or glass reactors have a large gas phase space at the top and operate intermittently. When preparing cerium oxide dispersions, the sealed, pressure-resistant, plug flow-operated pipeline reactor is used instead of the intermittent metal kettle / glass reactor with a large gas phase space at the top. This reduces the impact of gas phase overflow on the apparent reaction kinetics, overcomes the limitation of the atmospheric boiling point on the actual reaction temperature, and increases the reaction temperature while ensuring that the back pressure does not exceed a safe value, thereby improving the reaction efficiency by orders of magnitude.

[0058] It can be understood that by using a pipeline continuous synthesis device including a tubular heat exchanger and a pipeline reactor to prepare cerium oxide dispersion, the reaction time is shortened from 200 minutes to 3-15 minutes, and the safety of the pipeline reactor is higher than that of a tank reactor, especially a glass stirred tank, etc., the production efficiency and safety of the cerium oxide dispersion preparation process are significantly improved; in addition, the DPPH removal rate of the cerium oxide dispersion can be increased by more than 90%.

[0059] In addition, the cerium oxide nanospheres in the cerium oxide dispersion prepared by this preparation method have stable quality and small size. This preparation method is easy to scale up and control, and meets the requirements of green production.

[0060] In some embodiments, the tubular heat exchanger includes a preheating pipe having a diameter of 3 mm to 6 mm and a length of 5 m to 15 m. The diameter of the preheating pipe is 3 mm to 6 mm; for example, it can be, but is not limited to, 3 mm, 3.2 mm, 3.5 mm, 3.8 mm, 4 mm, 4.2 mm, 4.5 mm, 4.7 mm, 5 mm, 5.2 mm, 5.5 mm, 5.8 mm, 6 mm, or a range between any two of the above diameters. Examples of diameter intervals between any two diameters include, but are not limited to, 3.2 mm to 6 mm, 3.5 mm to 6 mm, 3.8 mm to 6 mm, 4 mm to 6 mm, 4.2 mm to 6 mm, 4.5 mm to 6 mm, 4.7 mm to 6 mm, 5 mm to 6 mm, 5.2 mm to 6 mm, 5.5 mm to 6 mm, or 5.8 mm to 6 mm. When the diameter of the preheating pipe is within the above range, the medium in the pipe of the pipe reactor can be better exchanged with heat, thereby improving the conversion rate of the product cerium oxide.

[0061] During their research, the inventors discovered that using smaller-diameter pipes resulted in insufficient sample collection due to the low flow rate. Furthermore, they discovered that even without turbulent flow within the pipes, the system pressure gradually increased over time, causing the material to slightly adhere to the pipe wall. Once a point of adherence occurs, as in the crystallization process after nucleation, it will increase until the pipe is blocked. Therefore, to prevent adherence and insufficient material, a 6mm pipe diameter is preferred for the pipe reactor.

[0062] The length of the preheating pipe is 5m-15m; for example, it can be, but is not limited to, 5m, 6m, 7m, 8m, 9m, 10m, 11m, 12m, 13m, 14m, 15m, or a range between any two of the above lengths. Examples of length intervals between any two lengths include, but are not limited to, 6m-15m, 7m-14m, 8m-13m, or 9m-12m. When the preheating pipe length is within the above range, the material can form a plug flow in the coil and achieve a longer maximum residence time, which is beneficial for improving yield.

[0063] As a possible embodiment, the pipeline continuous synthesis device further includes a storage tank, a feed pump, a condenser, a temperature controller, a pressure transmitter and a liquid collecting tank; the storage tank, the feed pump, the tubular heat exchanger, the pipeline reactor, the condenser and the liquid collecting tank are connected in sequence; the temperature controller is connected to the pipeline reactor, and the pressure transmitter is connected to the condenser;

[0064] The storage tank is used to store the mixed liquid, the feed pump is used to promote the operation of the mixed liquid and / or cerium oxide dispersion in the pipeline continuous synthesis device; the condenser is used to cool the product of the hydrothermal reaction; the temperature controller is used to control the temperature of the pipeline reactor; the pressure transmitter is used to monitor the pressure of the condenser; and the liquid collecting tank is used to collect the cerium oxide dispersion.

[0065] In some embodiments, the condenser includes a condensing pipe having a length of 10 m to 15 m. For example, the condensing pipe may be, but is not limited to, 10 m, 11 m, 12 m, 13 m, 14 m, 15 m, or a range between any two of the foregoing lengths. Optionally, the condensing pipe is a coil; thus, the condenser can efficiently cool the hydrothermal reaction product to below 50°C.

[0066] A schematic diagram of the structure of a pipeline continuous synthesis device is shown in FIG. Figure 1 As shown, it includes a storage tank 1, a feed pump 2, a tubular heat exchanger 3, a pipeline reactor 4, a condenser 5, a temperature controller 7, a pressure transmitter 8 and a liquid collecting tank 6; the storage tank 1, the feed pump 2, the tubular heat exchanger 3, the pipeline reactor 4, the condenser 5 and the liquid collecting tank 6 are connected in sequence; the temperature controller 7 is connected to the pipeline reactor 4, and the gas conveyor 8 is connected to the liquid collecting tank 6.

[0067] In order to ensure the safety of the preparation process, the pipeline continuous synthesis device is also provided with a pressure measuring point 9, a first bursting disc 10, a second bursting disc 11 and a pressure gauge 12; the pressure measuring point 9 and the first bursting disc 10 are connected in sequence, and the pressure measuring point 9 is connected to the line between the feed pump 2 and the tubular heat exchanger 3; the second bursting disc 11 is connected to the liquid collecting tank 6, the pressure gauge 12 is connected to the back pressure valve, and the pressure gauge 12 is connected to the liquid collecting tank 6.

[0068] Use Figure 1 When preparing a cerium oxide dispersion using the illustrated continuous pipeline synthesis apparatus, a mixed liquid, driven by a feed pump 2, enters a tubular heat exchanger 3 from a storage tank 1. The mixed liquid is heated to the hydrothermal reaction temperature by the tubular heat exchanger 3. The heated mixed liquid then enters a pipeline reactor 4, where a hydrothermal reaction occurs. The hydrothermal reaction product enters a condenser 5 and, after condensation, enters a liquid collection tank 6. During the preparation process, a temperature controller 7 controls the temperature of the tubular heat exchanger 3 and the pipeline reactor 4. The reaction product flows from the liquid collection tank 6 and enters a ceramic membrane 13 for washing. The resulting filtrate is then bottled to obtain the primary product.

[0069] In some embodiments, the reaction and preheating tubes are coiled tubing. Made of high-strength Hastelloy alloy, the coils offer excellent corrosion resistance in common environments and are resistant to attack by many chemicals, including acidic and alkaline solutions. Furthermore, they maintain excellent structural stability and strength even in high-temperature environments, making them suitable for high-temperature heating or cooling processes. Their high strength allows them to withstand significant pressure and force, making them suitable for applications requiring high reaction pressures.

[0070] As a possible embodiment, the reaction temperature of the hydrothermal reaction is 170°C-210°C; for example, it can be but not limited to 170°C, 175°C, 180°C, 185°C, 190°C, 195°C, 200°C, 205°C, 210°C or a range between any two of the above temperatures. The temperature interval between any two temperatures includes but is not limited to 175°C-210°C, 180°C-210°C, 185°C-210°C, 190°C-210°C, 195°C-210°C, 200°C-210°C or 205°C-210°C, etc. Within this temperature range, the precursor cerium nitrate hexahydrate can be fully decomposed to obtain the product cerium oxide; below 170°C, cerium nitrate hexahydrate is difficult to decompose; above 210°C, high temperature not only does not bring high energy consumption but also leads to excessively high reaction pressure.

[0071] The reaction time is 3 min to 15 min; for example, it can be, but is not limited to, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, or a range between any two of the above time periods. The time interval between any two time periods includes, but is not limited to, 3 min to 14 min, 4 min to 13 min, 5 min to 12 min, 6 min to 11 min, 7 min to 10 min, or 8 min to 9 min. Within this reaction time range, the yield of the product cerium oxide is relatively ideal; if the reaction time is less than 3 min, the cerium nitrate hexahydrate is difficult to decompose completely, resulting in a low yield; after 15 min of reaction, the cerium oxide conversion rate no longer increases.

[0072] The back pressure is 0.5 MPa-1.5 MPa; for example, it can be, but is not limited to, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1 MPa, 1.1 MPa, 1.2 MPa, 1.3 MPa, 1.4 MPa, 1.5 MPa, or a range between any two of the above pressures. The pressure interval between any two pressures includes, but is not limited to, 0.5 MPa-1.4 MPa, 0.6 MPa-1.3 MPa, 0.7 MPa-1.2 MPa, 0.8 MPa-1.1 MPa, or 0.9 MPa-1 MPa.

[0073] When the reaction temperature, reaction time and back pressure of the hydrothermal reaction are respectively within the above ranges, the reaction conditions are relatively mild, the reactant cerium nitrate hexahydrate can be completely converted, and the yield of the product cerium oxide is high.

[0074] As a possible implementation manner, the cerium-containing precursor in the mixed solution includes one or more of cerium nitrate hexahydrate and cerium nitrate.

[0075] In some optional embodiments, the pH adjuster includes one or more of acetic acid, formic acid, and propionic acid. Acetic acid not only has the effect of adjusting pH, but also can coordinate with Ce(III) to regulate the crystallization rate of CeO2, which is a necessary condition for the synthesis of cerium oxide nanospheres.

[0076] In some optional embodiments, the dispersion medium includes ethylene glycol. Ethylene glycol has good stability and a boiling point of 197° C. As a dispersion medium for the cerium-containing precursor, it has a good dispersion effect and is easy to separate after the reaction is completed.

[0077] In some embodiments, the mass percentage of the cerium-containing precursor in the mixed solution is 3%-15%. For example, it can be, but is not limited to, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or a range between any two of the above mass percentages. The mass percentage interval between any two mass percentages includes, but is not limited to, 4%-15%, 5%-14%, 6%-13%, 7%-12%, 8%-11%, or 9%-10%. When the mass percentage of the cerium-containing precursor in the mixed solution is within the above range, the product cerium oxide has a uniform size distribution, good dispersibility in aqueous solution, and high free radical scavenging performance.

[0078] In some embodiments, the mass volume ratio of the cerium-containing precursor to the pH adjuster is (200-600) g:(200-600) mL; for example, it can be, but is not limited to, 200 g:(200-600) mL, 250 g:(200-600) mL, 300 g:(200-600) mL, 350 g:(200-600) mL, 400 g:(200-600) mL, 450 g:(200-600) mL, 500 g:(200-600) mL, 600 g:(200-600) mL, or a range between any two of the above ratios. When the mass volume ratio of the cerium-containing precursor to the pH adjuster is within the above range, spherical cerium oxide microspheres with a large specific surface area can be obtained.

[0079] In some embodiments, the mass volume ratio of the cerium-containing precursor to the dispersion medium is (200-600) g:(6000-7000) mL; for example, it can be, but is not limited to, 200 g:(6000-7000) mL, 250 g:(6000-7000) mL, 300 g:(6000-7000) mL, 350 g:(6000-7000) mL, 400 g:(6000-7000) mL, 450 g:(6000-7000) mL, 500 g:(6000-7000) mL, 550 g:(6000-7000) mL, 600 g:(6000-7000) mL, or a range between any two of the above ratios. When the mass volume ratio of the cerium-containing precursor to the dispersion medium is within the above range, the cerium-containing precursor can form a homogeneous solution with the dispersion medium.

[0080] In some embodiments, the mass volume ratio of the cerium-containing precursor to water is (200-600) g:(100-200) mL; for example, it can be, but is not limited to, 200 g:(100-200) mL, 250 g:(100-200) mL, 300 g:(100-200) mL, 350 g:(100-200) mL, 400 g:(100-200) mL, 450 g:(100-200) mL, 500 g:(100-200) mL, 550 g:(100-200) mL, 600 g:(100-200) mL, or a range between any two of the above ratios. When the mass volume ratio of the cerium-containing precursor to water is within the above range, the precursor cerium nitrate hexahydrate can be fully dissolved in water.

[0081] In some embodiments, the mass ratio of the cerium-containing precursor, pH adjuster, water, and dispersion medium is 1:(0.2-1):(0.5-1):(30-35). When the mass ratio of the cerium-containing precursor, pH adjuster, water, and dispersion medium is within the above range, a cerium oxide microsphere product with uniform size, good dispersibility, and high free radical scavenging efficiency can be obtained.

[0082] The mass ratio of the cerium-containing precursor to the pH adjuster is 1:(0.2-1); for example, it can be, but is not limited to, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, or a range between any two of the above ratios. The ratio interval between any two ratios includes, but is not limited to, 1:(0.2-0.9), 1:(0.3-0.8), 1:(0.4-0.7), or 1:(0.5-0.6).

[0083] The mass ratio of the cerium-containing precursor to water is 1:(0.5-1); for example, it can be, but is not limited to, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, or a range between any two of the above ratios. The ratio interval between any two ratios includes, but is not limited to, 1:(0.5-0.9), 1:(0.6-0.8), 1:(0.6-0.7), or 1:(0.7-0.8).

[0084] The mass ratio of the cerium-containing precursor to the dispersion medium is 1:(30-35); for example, it can be, but is not limited to, 1:30, 1:30.5, 1:31, 1:31.5, 1:32, 1:32.5, 1:33, 1:33.5, 1:34, 1:34.5, 1:35, or a range between any two of the above ratios. The ratio interval between any two ratios includes, but is not limited to, 1:(30.5-35), 1:(30.5-34.5), 1:(31-34), 1:(31.5-33.5), 1:(32-33), or 1:(32.5-33).

[0085] In some embodiments, the preparation method further comprises: performing solid-liquid separation on the product of the hydrothermal reaction, washing the solid matter obtained after the solid-liquid separation with water until it is neutral, and then mixing the solid matter with water to prepare a cerium oxide dispersion.

[0086] As an example, the solid-liquid separation of the product of the hydrothermal reaction after cooling is performed by centrifugation or filtration.

[0087] In some embodiments, a ceramic filter membrane is used to filter the cooled hydrothermal reaction product.

[0088] As a possible implementation, the filtration method is cross-flow filtration; that is, the feed liquid flows at high speed within the membrane tube. Driven by pressure, the permeate containing small molecules flows outward along the membrane layer in a direction perpendicular to the membrane layer, while the concentrate containing large molecular components is retained by the membrane, thereby achieving the purpose of separating, purifying, and concentrating the product cerium oxide slurry. The ceramic membrane filter system has a high degree of process integration and fully automated control, enabling continuous feed, continuous discharge of filter residue and filtrate, and continuous product separation. The resulting filtrate is clear and transparent, which will bring higher economic benefits.

[0089] In an optional embodiment, the average pore size of the ceramic filter membrane is 100nm-500nm; for example, it can be but not limited to 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm or a range between any two of the above pore sizes.

[0090] The second aspect of the present invention provides a cerium oxide dispersion prepared by the preparation method of the first aspect of the present invention.

[0091] In some embodiments, the cerium oxide dispersion contains cerium oxide nanospheres, and the hydrodynamic radius of the cerium oxide nanospheres is 100 nm to 1000 nm; for example, it can be, but is not limited to, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, or a range between any two of the above hydrodynamic radii. The radius range between any two hydrodynamic radii includes, but is not limited to, 150 nm to 1000 nm, 150 nm to 950 nm, 200 nm to 900 nm, 250 nm to 850 nm, 300 nm to 800 nm, 350 nm to 750 nm, 400 nm to 700 nm, 450 nm to 650 nm, 500 nm to 600 nm, or 550 nm to 600 nm. When the hydrodynamic radius of the cerium oxide nanospheres is within the above range, they have good dispersibility in aqueous solution and can avoid significant coagulation. When the particle size is less than 100 nm, the product is difficult to separate, and when the particle size is greater than 1000 nm, the product tends to agglomerate to form aggregates that are difficult to disperse.

[0092] It should be noted that the hydrodynamic radius includes the solvent layer bound to the particle surface or other molecules moving with the particle, and is therefore slightly larger than the actual particle size. The hydrodynamic radius reflects the degree of dispersion of the cerium oxide nanospheres in water; the smaller the hydrodynamic radius, the more dispersed the cerium oxide particles are in water.

[0093] Cerium oxide has a fluorite cubic structure, a space group of Fm-3m, and a unit cell parameter a of 0.5411nm. In the crystal structure of cerium oxide, Ce 4+Occupies the octahedral voids, O 2- Occupies tetrahedral voids. The low-index crystal faces of cerium oxide are {100}, {110}, and {111}. Due to the electron transition from O 2p to Ce 4f, cerium oxide has strong absorption in the ultraviolet region, resulting in a pale yellow color and can be used as a UV absorber.

[0094] In cerium oxide, Ce 3+ and Ce 4+ It can be reversibly converted, and the conversion process is accompanied by the generation and elimination of oxygen vacancies. Equation, this process can be described by the following defect reaction:

[0095]

[0096] Among them, Oo represents O 2- , Ce Ce Representative Ce 4+ , is an electrically neutral oxygen vacancy, while Ce' Ce Representative Ce 3+ When cerium oxide is reduced, the oxygen in the tetrahedral gap will escape, and the remaining two electrons will be taken away by the two adjacent Ce 4+ Get, and then Ce 4+ Reduced to Ce 3+ This characteristic gives CeO2 excellent oxygen storage and release capabilities, and this defect property is also the basis of its catalytic, antioxidant and anti-aging properties.

[0097] The technical solution of the present invention is described in detail below with reference to specific embodiments.

[0098] 1. Preparation of Cerium Oxide Dispersion

[0099] Example 1

[0100] A pipeline continuous synthesis device is used to prepare a cerium oxide dispersion. The specific process includes: weighing 40g of cerium nitrate hexahydrate (as a cerium-containing precursor), 40mL of acetic acid (as a pH adjuster), 40mL of deionized water and 600mL of ethylene glycol (as a dispersion medium), mixing the above substances evenly to obtain a mixed liquid and placing it in a storage tank; using a feed pump to transport the mixed liquid to a tubular heat exchanger, the temperature of the mixed liquid flowing through the tubular heat exchanger rises to 170°C (hydrothermal reaction temperature), and then flows through to a pipeline reactor. After staying in the pipeline reactor for 7.5min (hydrothermal reaction time), the hydrothermal reaction product flows through a condenser, and the condensed hydrothermal reaction product is filtered using a ceramic filter membrane. The filtered solid matter is washed with water until it is neutral and stored in a liquid collecting tank; wherein, the mass proportion of the cerium-containing precursor in the mixed liquid is 5%, the diameter of the pipeline reactor is 6mm, and the length is 30m.

[0101] Example 2-18

[0102] The preparation method of the cerium oxide dispersion in Examples 2-18 is basically similar to the preparation method of the cerium oxide dispersion in Example 1, with the main differences being: the amount of the cerium-containing precursor, the amount of deionized water, the amount of the pH adjuster, the amount of the dispersion medium, the mass proportion of the cerium-containing precursor in the mixed liquid, the temperature of the heating reaction, the time of the heating reaction, the diameter of the tube substitute reactor, and the length of the tube reactor. For details, see Table 1.

[0103] Comparative Example 1-2

[0104] In Comparative Examples 1-2, a cerium oxide dispersion was prepared in a reactor. The specific preparation method was as follows: 40 g of cerium nitrate hexahydrate (as a cerium-containing precursor), 40 mL of acetic acid (as a pH adjuster), 40 mL of deionized water, and 600 mL of ethylene glycol (as a dispersion medium) were weighed. After uniform mixing, the mixture was poured into a 1-L Hastelloy alloy reactor, heated to 170°C (approximately 40 minutes), and then cooled after the predetermined reaction time (90 minutes / 180 minutes). The cooled hydrothermal reaction product was centrifuged, and the filtered solids were washed with water until neutral and ready for use.

[0105] It should be noted that the cerium oxide dispersion prepared in Comparative Example 1 contains cerium oxide microspheres.

[0106] The cerium oxide dispersions prepared in the above examples were observed by electron scanning electron microscopy, and the hydrodynamic radius of the cerium oxide nanospheres was measured as shown in Table 1; the cerium oxide dispersions prepared in Comparative Examples 1-2 were observed by electron scanning electron microscopy, and the hydrodynamic radius of the cerium oxide microspheres was measured as shown in Table 1.

[0107] Table 1

[0108]

[0109]

[0110]

[0111] Where w1 represents the mass fraction of the cerium-containing precursor in the mixed solution. Radius refers to the hydrodynamic radius of the cerium oxide nanospheres or the hydrodynamic radius of the cerium oxide microspheres.

[0112] The results in Table 1 show that the hydrodynamic radius of the cerium oxide nanospheres increases with increasing mass fraction of cerium nitrate hexahydrate in the mixed solution. Furthermore, at the same reaction temperature, the conversion rate of the hydrothermal reaction decreases with increasing length of the tubular reactor. This is likely due to the large amount of gas generated during the reaction, resulting in an actual residence time far shorter than the time calculated using the "holdup / flow rate" formula. Therefore, a 30m tubular reactor length is preferred.

[0113] Comparison of the results of Examples 1-18 and Comparative Example 1 shows that the use of a pipeline reactor can significantly reduce the reaction time, requiring only 3-15 minutes for the reaction to be complete; whereas the use of a reactor requires 3 hours for the reaction to be complete.

[0114] The electron scanning electron micrographs and size distribution of the cerium oxide nanospheres prepared in Example 1 and Example 7 are shown in FIG. Figure 2 As shown; Figure 2 Figures ac are scanning electron micrographs of cerium oxide nanospheres in Example 1. Figure 2 Where g is the size distribution of cerium oxide nanospheres in Example 1, Figure 2 df in the figure is the electron scanning electron micrograph of the cerium oxide nanospheres in Example 7. Figure 2 Where h is the size distribution of cerium oxide nanospheres in Example 7. Figure 2 It can be seen that the average particle size of the cerium oxide nanospheres prepared in Example 1 is about 80 nm, and the average particle size of the cerium oxide nanospheres prepared in Example 7 is about 120 nm.

[0115] The optical microscope diagram and transmission electron microscope diagram of the cerium oxide microspheres prepared in Comparative Example 1 are shown in FIG. Figure 3 As shown; Figure 3 Figure a is a schematic diagram of an optical microscope of the cerium oxide microspheres in Comparative Example 1, and figure b is a schematic diagram of a transmission electron microscope of the cerium oxide microspheres in Comparative Example 1. Figure 3 As shown in Figure a, the size of the cerium oxide microspheres prepared in Comparative Example 1 is greater than 1 μm and can be clearly observed under an optical microscope; Figure 3 As can be seen from Figure b, the cerium oxide prepared in Comparative Example 1 has agglomerated and is in the form of large-sized aggregated micron particles.

[0116] The hydrodynamic radius of the cerium oxide nanospheres prepared in Example 1 and Example 7 and the cerium oxide microspheres prepared in Comparative Example 1 is as follows: Figure 4 As shown; Figure 4 Where a is the hydrodynamic radius of the cerium oxide nanospheres prepared in Example 1, Figure 4 Where b is the hydrodynamic radius of the cerium oxide nanospheres prepared in Example 7, Figure 4Where c is the hydrodynamic radius of the cerium oxide microspheres prepared in Comparative Example 1. Figure 4 As can be seen, the hydrodynamic radii of the cerium oxide nanospheres prepared using the pipeline reactor in Examples 1 and 7 were 165 nm and 261 nm, respectively, slightly larger than their TEM-observed sizes. In contrast, the hydrodynamic radius of the cerium oxide microspheres prepared using the autoclave in Comparative Example 1 was significantly larger, reaching 679 nm. Because the hydrodynamic radius of particles in aqueous solution can reflect their degree of dispersion in water, these results further confirm that the use of the pipeline reactor facilitates the preparation of cerium oxide nanospheres with better dispersion.

[0117] Depend on Figure 2-4 The results show that the average particle size and hydrodynamic radius of cerium oxide nanospheres prepared by the pipeline reactor are smaller, which is more conducive to dispersion in cosmetic formulas and has better antioxidant properties.

[0118] 2. Cerium Oxide Dispersion Performance Test

[0119] 1. Comparison of dispersion stability

[0120] The Turbiscan optical stability analyzer is used to test the stability of suspension systems and is crucial for accurately evaluating system stability. Compared to traditional evaluation methods such as dynamic light scattering, this method requires no sample pretreatment and can measure the intensity of backscattered and transmitted light in real time. It can calculate parameters such as the migration rate of particles within the system, the thickness of the sediment layer, and the system's instability index, enabling accurate and efficient analysis of system stability changes.

[0121] The results of the sedimentation stability of the cerium oxide dispersions prepared in Example 1, Example 7 and Comparative Example 1 were respectively tested using a Turbiscan optical stability analyzer are shown in FIG. Figure 5 As shown; Example 1, Example 7 and Comparative Example 1 prepared in the middle of the cerium oxide dispersion backscattered light intensity change results schematic diagram as shown Figure 6 As shown. Figure 5 It can be seen that within the scanning time (0 to 60 minutes), the backscattered light intensity at each height of the cerium oxide nanosphere samples prepared by the pipeline reactor in Example 1 and Example 7 hardly changes with time, and the dispersion has good stability; while the backscattered light intensity at each height of the cerium oxide microsphere sample prepared by the reactor in Comparative Example 1 gradually decreases with time, indicating that the sample particle size is large and the dispersion has stratified precipitation. This phenomenon can also be seen from Figure 6 The changes in backscattered light intensity are more clearly observed in the middle part.

[0122] The schematic diagram of the sedimentation of the cerium oxide dispersion prepared by the pipeline reactor in Example 1, Example 7 and Comparative Example 1 is as follows: Figure 7 shown. Figure 7 a and d are the sedimentation results of the cerium oxide dispersion in Example 1. Figure 7 b and e are the sedimentation results of the cerium oxide dispersion in Example 7. Figure 7 Figures c and f are the sedimentation results of the cerium oxide dispersion in Comparative Example 1. Figure 7 The results show that the cerium oxide dispersions in Examples 1, 7, and Comparative Example 1 all exhibited good dispersibility upon initial preparation. After 6 hours of natural aging, the cerium oxide nanospheres in Examples 1 and 7 showed no significant demixing, indicating that the cerium oxide nanospheres prepared in Examples 1 and 7 exhibited good dispersibility and a small size distribution. After 6 hours of natural aging, the cerium oxide microspheres in Comparative Example 1 exhibited significant sedimentation, consistent with their larger particle size. Figure 7 The results in this paper can further confirm that the cerium oxide nanospheres prepared by the pipeline reactor have better dispersibility.

[0123] 2. Comparison of Synthesis Efficiency of Cerium Oxide Dispersions

[0124] When using a reactor to prepare cerium oxide dispersion, the product results at different reaction times are as follows: Figure 8 As shown, the mass proportion of the cerium-containing precursor in the mixed solution is 5%; Figure 8 a means the reaction was carried out at 170℃ for 0.5h. Figure 8 b means the reaction was carried out at 170℃ for 1h. Figure 8 In the reaction, the reaction temperature was 170℃ for 1.5h. Figure 8 Where d is the reaction time at 170℃ for 2h. Figure 8 The results show that when the reaction temperature is between 170°C for 0.5 and 1 hour, the raw material solution remains clear, and no cerium oxide product is obtained. After the reaction time reaches 1.5 hours, a turbid suspension is observed, indicating the start of cerium oxide production. After the reaction time reaches 2.0 hours, a large amount of cerium oxide product is obtained. Using the pipeline reactor, a yield of >80% can be achieved in just 15 minutes, demonstrating the excellent efficiency of the pipeline reactor.

[0125] 2.DPPH free radical scavenging effect

[0126] It should be noted that DPPH (1,1-disphenyl-2-picryl-hydrazyl), chemically named 1,1-diphenyl-2-trinitrophenylhydrazine, has a molecular formula of (C6H5)2N-NC6H2(NO2)3. This compound has an unpaired valence electron on one of the nitrogen bridge atoms, and the orbital motion of this electron is nearly offset by the molecular structure. The capture of DPPH free radicals is often used as an indicator of antioxidant capacity. DPPH is a stable organic free radical with a maximum absorption peak in the visible light region at 517 nm. In ethanol solution, each DPPH molecule generates a stable nitrogen-containing free radical with a typical purple color. When it reacts with a free radical scavenger that donates one electron (for example, cerium oxide dispersion), it produces a colorless product, which lightens the solution's typical purple color. The degree of discoloration is stoichiometrically related to the number of paired electrons. Therefore, spectrophotometry can be used for quantitative analysis to detect the free radical scavenging situation, thereby evaluating the free radical scavenging ability of the sample; the DPPH scavenging reaction process of cerium oxide dispersion is as follows:

[0127]

[0128] 1.1 Instruments and Experiments

[0129] (1) Analytical balance (d = 0.1 mg, purchased from Sartorius, model BSA2202S-CW, Max 220 g);

[0130] (2) Vortex mixer (model MX-F);

[0131] (3) Multifunctional microplate reader (purchased from Tecan), 96-well plate (model jet)

[0132] (4) Pipette (5 mL, 200 μL, 1000 μL, purchased from Eppendorf);

[0133] (5) DPPH (purchased from Sigma, analytical grade, C 18 H 12 N5O6, molecular weight 394.32);

[0134] (6) Vitamin C (purchased from Bio-Di Biotechnology Co., Ltd., analytical grade);

[0135] (7) Anhydrous ethanol (purchased from Sinopharm Chemical Reagent Co., Ltd., analytical grade).

[0136] 1.2 Experimental preparation

[0137] 1.2.1 Reagent preparation

[0138] (1) 0.2 mmol / L DPPH solution

[0139] Weigh 0.0200 g of DPPH, dissolve it in anhydrous ethanol and dilute it to volume in a 250 mL volumetric flask, and shake well.

[0140] (2) 200 μg / mL VC solution (Note: Prepare immediately before use)

[0141] Weigh 0.0500 g VC, dissolve it in deionized water and dilute it to volume in a 250 mL volumetric flask, and shake well.

[0142] (3) 15 μg / mL VC solution

[0143] Take 0.600 mL of 200 μg / mL VC aqueous solution, add 7.400 mL of anhydrous ethanol, and mix well.

[0144] (4) 0.5 wt% cerium oxide dispersion

[0145] Take 50 mg of the cerium oxide sample to be tested, disperse it in 10 mL of deionized water, ultrasonically disperse it for 10 minutes, and shake it evenly to obtain a 0.5 wt% cerium oxide dispersion.

[0146] 1.2.2 Test operation

[0147] A blank group C, a negative control group B, a positive control group AVc and a sample group A were set up respectively; wherein, the sample group A refers to the cerium oxide dispersions prepared in Examples 1-15 and Comparative Example 1 with concentrations of 0.1 wt%, 0.3 wt% and 0.5 wt%, respectively.

[0148] 1.2.3 Result Processing

[0149] The calculation formula of DPPH free radical scavenging rate is: scavenging rate = [(Y+Z)-X] / B*100%

[0150] Where: X represents the absorbance value after the sample solution is mixed with the DPPH solution; Y represents the absorbance value after the anhydrous ethanol is mixed with the DPPH solution; Z represents the absorbance value after the anhydrous ethanol is mixed with the sample solution.

[0151] 1.2.3 Experimental operation process

[0152] The specific order of adding samples and the dosage are shown in Table 2-1 and Table 2-2 respectively.

[0153] Table 2-1. Reagent addition in sample tubes

[0154]

[0155] Table 2-2. Reagent addition in sample tubes

[0156]

[0157] It should be noted that A1-A10 indicate that 10 samples of each cerium oxide product were set and measured in parallel 10 times.

[0158] 1.2.4 Results Analysis

[0159] The DPPH scavenging results of the cerium oxide dispersions in Examples 1-18 are shown in Table 3.

[0160] Table 3

[0161]

[0162] The results of the DPPH free radical scavenging efficiency of the cerium oxide dispersions prepared in Example 4 and Comparative Example 2 are as follows: Figure 9 As shown in Table 3 and Figure 9 The results show that when the cerium oxide concentration is 0.1wt%, the DPPH clearance rate of the product synthesized by the pipeline reactor in Example 4 can reach 72.9%, which is twice that of the product synthesized by the reactor in Comparative Example 2 (36.3%), an increase of 100.8%. When the cerium oxide concentration is 0.3wt%, the DPPH clearance rate of the product synthesized by the pipeline reactor in Example 4 reaches 93.2%, which is still 27.3% higher than the product synthesized by the reactor in Comparative Example 2. When the cerium oxide concentration is as high as 0.5wt%, the DPPH clearance rate of the product synthesized by the pipeline reactor in Example 4 is 94.4%, and the DPPH clearance rate of the product synthesized by the reactor in Comparative Example 2 also reaches 93.0%, and the difference between the two is no longer obvious. The cerium oxide nanospheres synthesized by the pipeline reactor have already shown a higher DPPH clearance rate at low concentrations, indicating that it has a lower effective concentration in the formula because it may have better compatibility.

[0163] From the above experimental results, it can be seen that the reaction time for preparing cerium oxide nanospheres using a pipeline reactor is greatly shortened, the synthesis efficiency of cerium oxide is higher, and the obtained cerium oxide nanospheres are smaller in size; the stability of the cerium oxide dispersion is higher, the dispersibility of the cerium oxide nanospheres in water is better, and the cerium oxide dispersion has an excellent DPPH scavenging rate.

[0164] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0165] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for preparing a cerium oxide dispersion, It is characterized in that The preparation method is carried out using a pipeline continuous synthesis device, which includes a tubular heat exchanger and a pipeline reactor; the preparation method includes the following steps: A mixed solution including a cerium-containing precursor, a pH adjusting agent, water and a dispersion medium is heated to a reaction temperature of a hydrothermal reaction in the tubular heat exchanger; the mass proportion of the cerium-containing precursor in the mixed solution is 3%-5%; the cerium-containing precursor includes one or more of cerium nitrate hexahydrate and cerium nitrate; the pH adjusting agent includes one or more of acetic acid, formic acid and propionic acid; the dispersion medium includes ethylene glycol; the mass volume ratio of the cerium-containing precursor to the pH adjusting agent is (200-600) g: (200-600) mL; the mass volume ratio of the cerium-containing precursor to the dispersion medium is (200-600) g: (6000-7000) mL; the mass volume ratio of the cerium-containing precursor to the water is (200-600) g: (100-200) mL; The heated mixed solution is subjected to the hydrothermal reaction in the reaction pipe of the pipe reactor to prepare the cerium oxide dispersion; the reaction temperature of the hydrothermal reaction is 170° C.-210° C., the reaction time is 7.5 min.-15 min., and the back pressure is 0.5 MPa-1.5 MPa; Among them, the diameter of the reaction pipe is 3mm-6mm and the length is 30m-60m; the tubular heat exchanger includes a preheating pipe with a diameter of 3mm-6mm and a length of 5m-15m; the reaction pipe and the preheating pipe are coils.

2. The method for preparing the cerium oxide dispersion according to claim 1, It is characterized in that The pipeline continuous synthesis device also includes a storage tank, a feed pump, a condenser, a temperature controller, a pressure transmitter and a liquid collecting tank; the storage tank, the feed pump, the tubular heat exchanger, the pipeline reactor, the condenser and the liquid collecting tank are connected in sequence; the temperature controller is connected to the pipeline reactor, and the pressure transmitter is connected to the condenser; The storage tank is used to store the mixed solution, and the feed pump is used to promote the operation of the mixed solution and / or the cerium oxide dispersion in the pipeline continuous synthesis device; The condenser is used to cool the product of the hydrothermal reaction; The temperature controller is used to control the temperature of the tubular heat exchanger and the pipeline reactor; the pressure transmitter is used to monitor the pressure of the condenser; and the liquid collecting tank is used to collect the cerium oxide dispersion.

3. The method for preparing the cerium oxide dispersion according to claim 1, It is characterized in that The reaction pipe has a diameter of 6 mm and a length of 30 m.

4. The method for preparing the cerium oxide dispersion according to claim 1, It is characterized in that The mass ratio of the cerium-containing precursor, the pH adjuster, the water and the dispersion medium is 1:(0.2-1):(0.5-1):(30-35).

5. The method for preparing the cerium oxide dispersion according to any one of claims 1 to 4, It is characterized in that The preparation method further comprises: The product of the hydrothermal reaction is subjected to solid-liquid separation, the solid matter obtained after the solid-liquid separation is washed with water to be neutral, and then the solid matter is mixed with water to obtain the cerium oxide dispersion.

6. The method for preparing the cerium oxide dispersion according to claim 5, It is characterized in that The cooled product of the hydrothermal reaction is filtered using a ceramic filter membrane.

7. The method for preparing the cerium oxide dispersion according to claim 6, It is characterized in that The average pore size of the ceramic filter membrane is 100nm-500nm.

8. The method for preparing the cerium oxide dispersion according to claim 6, It is characterized in that The filtering method is cross-flow filtration.

9. A cerium oxide dispersion, It is characterized in that The cerium oxide dispersion is prepared by the preparation method according to any one of claims 1 to 8.

10. The cerium oxide dispersion according to claim 9, It is characterized in that The cerium oxide dispersion contains cerium oxide nanospheres, and the hydrodynamic radius of the cerium oxide nanospheres is 100nm-1000nm.

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