Spherical cerium dioxide, and preparation method and application thereof

Abstract

This application discloses a spherical cerium dioxide, its preparation method, and its application. The method includes: mixing a cerium source, water, nitric acid, and a mixed organic acid, purifying the mixture to obtain a mixed solution; wherein the mixed organic acid includes citric acid and γ-hydroxybutyric acid; adding ammonia and an ammonium source to the mixed solution, controlling the mass ratio of ammonia, ammonium source, and water to be 6-10:5:30-100, and adjusting the pH of the system to 9-12; conducting a sol-gel reaction at 20-95℃ for 2-240 hours to obtain a reaction solution; and concentrating and spray-drying the solution to obtain spherical cerium dioxide. The spherical cerium dioxide prepared by this method has the advantages of low impurity content, high purity, concentrated particle size, and regular morphology, making it suitable for use in high-end cosmetics.

Description

Technical Field

[0001] This application relates to the field of nanomaterials with metal oxides, specifically to a spherical cerium dioxide, its preparation method, and its application. Background Technology

[0002] Currently, sunscreens in cosmetics mainly fall into three categories: physical sunscreens, chemical sunscreens, and biological sunscreens. Physical sunscreens, such as titanium dioxide, form "micromirrors" or "shields" on the skin's surface, reflecting and scattering ultraviolet rays. Their advantages include immediate effectiveness, good stability, and low irritation, making them suitable for sensitive skin, children, and the skin around the eyes. However, traditional formulas are thick and tend to leave a white cast after application, affecting skin feel and appearance. Chemical sunscreens absorb ultraviolet rays and convert them into heat energy to protect the skin. Common ingredients include ethylhexyl methoxycinnamate, octocrylene, avobenzone, and ethylhexyl salicylate. They are lightweight, transparent, and easy to apply, but some ingredients may irritate the skin, requiring pre-application and repeated reapplication. Broad-spectrum sunscreens often require the formulation of multiple chemical sunscreens, increasing formula complexity and the risk of irritation. Biological sunscreen ingredients such as vitamins C / E, polyphenols (such as green tea extract), carotenoids, and sodium hyaluronate are usually used as auxiliary ingredients to exert indirect protection by scavenging free radicals generated by ultraviolet rays and repairing damaged cells. However, their protection lasts for a short time and their effects are unstable, so they cannot be used as the main sun protection barrier on their own.

[0003] Cerium dioxide possesses excellent UV protection capabilities, reflecting and scattering ultraviolet rays. However, existing methods for preparing cerium dioxide often fail to yield high-purity powders, resulting in the widespread presence of impurities. These impurities can lead to skin allergies and reduce the safety of cosmetics, particularly failing to meet the stringent safety and protective efficacy requirements of high-end cosmetics.

[0004] Therefore, there is an urgent need to develop a method for preparing high-purity cerium dioxide with excellent UV resistance and low irritation to meet the application requirements of high-end cosmetics. Summary of the Invention

[0005] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application proposes a method for preparing spherical cerium dioxide.

[0006] This application also provides a spherical cerium dioxide.

[0007] This application also provides for the application of the above-mentioned spherical cerium dioxide.

[0008] Specifically, the first aspect of this application relates to a method for preparing spherical cerium dioxide, comprising the following steps: S1. Mix cerium source, water, nitric acid, and mixed organic acid, and purify to obtain a mixed solution; wherein the mixed organic acid includes citric acid and γ-hydroxybutyric acid, and the volume ratio of nitric acid, mixed organic acid, and water is 2:3~5:150~200. S2. Add ammonia and ammonium source to the mixed solution, control the mass ratio of ammonia, ammonium source and water in step S1 to be 6~10:5:30~100, and make the pH of the system 9~12. Carry out the sol-gel reaction at 20~95℃ for 2~240h to obtain the reaction solution. S3. The reaction solution is concentrated and spray-dried to obtain spherical cerium dioxide.

[0009] The method for preparing spherical cerium dioxide according to the first aspect of this application has at least the following beneficial effects: This application employs a mixed organic acid system composed of citric acid and γ-hydroxybutyric acid, which can improve the purification effect of the cerium source system. Citric acid contains multiple carboxyl and hydroxyl groups, which can form relatively stable complexes with cerium ions, and can also complex metal impurity ions in the cerium source; γ-hydroxybutyric acid molecules contain carboxyl and hydroxyl groups, which can provide a milder auxiliary complexing and dispersing effect. The combination of the two can form a synergistic system of strong and weak complexes, reducing the probability of impurities co-precipitating with the cerium component or entering the gel network, which helps to obtain high-purity cerium dioxide.

[0010] By limiting the volume ratio of nitric acid, mixed organic acids, and water, it is beneficial to balance the dissolution of the cerium source, complexation purification, and the stability of subsequent gelation reactions. Simultaneously, the system contains high effective concentrations of ammonia and ammonium sources; ammonia can provide OH-. - This promotes the complete hydrolysis of cerium ions and the formation of cerium hydroxide; the ammonium source and ammonia water together constitute NH3 / NH4. + The buffer system stabilizes the system pH, reducing agglomeration and impurity entrapment caused by drastic local pH fluctuations. The complexation and release of cerium ions by the mixed organic acids, combined with the alkaline buffer environment formed by ammonia / ammonium sources, allows cerium hydroxide to form sol particles in a more uniform manner. At the same time, controlling the pH of the reaction system at 9-12 is beneficial for the full formation of cerium precursors and maintaining the overall reaction homogeneity of the system.

[0011] Concentration treatment increases the solute content, making the spray-dried particles more uniform; spray drying ensures particle dispersion while rapidly evaporating the solvent.

[0012] Through the above-described multi-step control, the spherical cerium dioxide prepared by this invention has the advantages of low impurity content, high purity, concentrated particle size, and regular morphology, making it suitable for use in high-end cosmetics. This spherical cerium dioxide exhibits excellent anti-UV properties, and due to its high purity and low impurity characteristics, it significantly reduces skin irritation, improves formulation stability, and enhances the user experience.

[0013] According to some embodiments of this application, the cerium source is selected from at least one of cerium carbonate, cerium nitrate, and cerium hydroxide, which helps to obtain high-purity cerium dioxide.

[0014] According to some embodiments of this application, the concentration of the cerium source in the mixed solution is 0.025~10wt%.

[0015] According to some embodiments of this application, the mass ratio of citric acid to γ-hydroxybutyric acid is 1:1 to 5.

[0016] According to some embodiments of this application, the purification is carried out using a recrystallization method.

[0017] Preferably, the recrystallization temperature is -10 to 4°C, and the process is repeated at least 3 times.

[0018] According to some embodiments of this application, the purification process is carried out until the purity of the resulting solution reaches 9N or higher, meaning that the content of impurities detected in the solution is less than 10%. -7 %.

[0019] According to some embodiments of this application, the concentration of the ammonia water is 0.1wt%~10wt%, and the purity is ≥99.99%.

[0020] According to some embodiments of this application, the ammonium source is ammonium carbonate with a purity ≥99.99%.

[0021] According to some embodiments of this application, the molar ratio of ammonia to ammonium source in the ammonia water is 1:0.4-2.

[0022] According to some embodiments of this application, the temperature of the sol-gel reaction is 40~80℃, and the reaction time is 100~200h.

[0023] According to some embodiments of this application, the sol-gel reaction is stirred at a speed of 5-500 rpm. By controlling the reaction conditions, especially by appropriately increasing the stirring rate during the reaction, it is helpful to obtain a fine and uniform powder morphology.

[0024] According to some embodiments of this application, the concentration results in a liquid with a solid content of 5-30 wt%. The concentration temperature is 25-75°C, and the concentration time is 3-24 hours. Excessive concentration temperature can lead to agglomeration.

[0025] According to some embodiments of this application, the inlet temperature of the spray dryer is 20~80℃, the liquid flow rate is ≥1L / min, and the nozzle pressure is ≥0.1MPa.

[0026] According to some embodiments of this application, the spray drying is followed by a re-drying process, wherein the temperature of the re-drying process is 40~200℃ and the drying time is 0.5~3h.

[0027] The second aspect of this application relates to spherical cerium dioxide prepared using the aforementioned preparation method.

[0028] According to some embodiments of this application, the spherical cerium oxide has a particle size D50 of 100~2000nm as measured by a laser particle size analyzer, a dispersion index (D90-D10) / D50≤1.2, and an impurity content ≤0.1ppm.

[0029] The third aspect of this application relates to the use of the spherical cerium dioxide in the preparation of cosmetics.

[0030] In this article, “approximately” indicates that the allowable error range is ±5%. For example, approximately 100 means 100 ± 5% × 100.

[0031] The numerical ranges involved all include endpoint values ​​and cover any value within that range or any smaller range, such as the range obtained by any combination of the specifically listed numerical values.

[0032] Other features and advantages of this application will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing this application. Attached Figure Description

[0033] Figure 1 This is a particle SEM image from Example 1.

[0034] Figure 2 This is a SEM image of the particles in Comparative Example 5. Detailed Implementation

[0035] The embodiments of this application are described in detail below. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0036] In the following examples, some of the raw materials are described below: Ammonia water: concentration 10wt%, purity ≥9N.

[0037] Nitric acid: concentration 68~70wt%, purity 5N (≥99.999%).

[0038] Cerium carbonate: purity > 99.99%.

[0039] Cerium hydroxide: purity > 99.99%.

[0040] Cerium sulfate: purity > 99.99%.

[0041] Citric acid: Purity > 99.99%.

[0042] γ-hydroxybutyric acid: purity > 99.99%.

[0043] Glycine: Purity > 99.99%.

[0044] Ammonium carbonate: purity > 99.99%.

[0045] Unless otherwise specified, all raw materials or equipment mentioned are commercially available and can be purchased directly from the market.

[0046] Example 1 The method for preparing spherical cerium oxide includes the following steps: (1) Cerium carbonate is dissolved in water, nitric acid, and a mixed organic acid by heating, and then purified by multiple recrystallization processes to obtain a mixed solution with a purity of 9N. The mass ratio of cerium carbonate to the mixed solution is approximately 1:2000; the mixed organic acid is a mixture of citric acid and γ-hydroxybutyric acid in a mass ratio of 1:2; and the volume ratio of nitric acid, the mixed organic acid, and water is 2:3:180. The recrystallization temperature is 0℃, and the recrystallization is performed more than 3 times until the required purity is achieved.

[0047] (2) Add ammonia and ammonium carbonate to the mixed solution obtained in step (1), control the mass ratio of water in step (1) to ammonia and ammonium carbonate in step (2) to be 75:10:5, the pH of the reaction system is 10.1, and carry out sol-gel reaction at 60℃ to generate nano-spherical cerium oxide sol solution (reaction solution) for 120h.

[0048] (3) The reaction solution obtained in step (2) was concentrated at 50°C for 12 hours until the solid content of the solution was 20 wt%. Then, it was spray-dried at 60°C with a high-pressure spray pressure of 1 MPa and a liquid flow rate of 5 L / min. Finally, it was rolled and dried at 120°C for 1 hour to obtain spherical cerium dioxide particles with the following morphology. Figure 1 As shown.

[0049] Example 2 (1) Cerium hydroxide is dissolved by heating with water, nitric acid and a mixed organic acid, and then purified by multiple recrystallization processes to obtain a mixed solution with a purity of 9N. The mass ratio of cerium hydroxide to the mixed solution is 1:500; the mixed organic acid is a mixture of citric acid and γ-hydroxybutyric acid in a mass ratio of 1:2; the volume ratio of nitric acid, mixed organic acid and water is 2:5:150. The recrystallization temperature is 0℃, and the recrystallization is performed more than 4 times until the required purity is achieved.

[0050] (2) Add ammonia and ammonium carbonate to the mixed solution obtained in step (1), control the mass ratio of water in step (1) to ammonia and ammonium carbonate in step (2) to be 80:18:13, the pH of the reaction system is 10.8, and carry out sol-gel reaction at 60℃ to generate nano-spherical cerium oxide sol solution (reaction solution) for 200h.

[0051] (3) The reaction solution obtained in step (2) is concentrated at a temperature of 50°C for 12 hours until the solid content of the solution is 30 wt%. Then, it is spray-dried at an inlet temperature of 50°C, a high-pressure spray pressure of 1 MPa, and a liquid flow rate of 5 L / min. Finally, it is rolled and dried at 120°C for 1 hour to obtain spherical cerium dioxide particles.

[0052] Comparative Example 1 Compared with Example 1, the difference is that cerium carbonate in step (1) is replaced with an equal amount of cerium sulfate, while the other conditions remain unchanged. The particle size is larger, the morphology is uneven, and the purity decreases.

[0053] Comparative Example 2 Compared with Example 1, the difference is that the mixed organic acid in step (1) is replaced with an equal amount of citric acid, while the other conditions remain unchanged. The particle morphology is uneven and the purity decreases.

[0054] Comparative Example 3 Compared with Example 1, the difference is that the mass ratio of water in step (1) to ammonia and ammonium carbonate in step (2) is 80:2:2, while the other conditions remain unchanged. A low ammonia source concentration will lead to fluctuations in the reaction rate, an increase in particulate impurities, and a decrease in the final purity.

[0055] Comparative Example 4 Compared with Example 1, the difference is that the mass ratio of water in step (1) to ammonia and ammonium carbonate in step (2) is 80:1:1, while the other conditions remain unchanged. Due to insufficient ammonia source, the reaction rate is too low, the reaction cannot proceed completely, and nanoparticles cannot be formed.

[0056] Comparative Example 5 Compared to Example 1, the difference lies in reducing the amount of ammonia in step (2) to a system pH of 3-4, while keeping other conditions unchanged. The sol-gel reaction cannot be fully completed, and spherical nanoparticles cannot be obtained; their morphology is as follows... Figure 2 As shown.

[0057] Comparative Example 6 The difference from Example 1 is that the composite organic acid is citric acid / butyric acid in a mass ratio of 1:2.

[0058] Test case 1. Particle size and dispersion index: Tested using a laser particle size analyzer, wet dispersion was performed, and deionized water was used as the dispersion medium. D50 is the volumetric median particle size Dv50, which is the particle size corresponding to a cumulative volume distribution of 50%. The dispersion index is calculated using the formula (D90-D10) / D50, where D10 and D90 are the particle sizes corresponding to a cumulative volume distribution of 10% and 90%, respectively.

[0059] 2. Impurity content: Tested by inductively coupled plasma optical emission spectrometry (ICP-OES).

[0060] 3. Average transmittance of UVA and UVB: Weigh 2g of the powder to be tested and prepare a paste with deionized water and petroleum jelly. The mass fraction of petroleum jelly in the paste is 10%, and the mass fraction of the powder is 5%. Coat the paste evenly onto the surface of a 2mm thick transparent PMMA plate with a coating amount of 0.2g / cm². Then cover it with another identical PMMA plate, ensuring the sample is evenly distributed between the two PMMA plates. Measure using a UV-Vis spectrophotometer. Use the two uncoated PMMA plates as blank controls for baseline correction. The UVB test band is 280–320nm, and the UVA test band is 320–400nm. Record the transmittance at each wavelength, taking values ​​every 5nm, and calculate the average transmittance in the UVA and UVB bands.

[0061] The test results are shown in Table 1.

[0062] Table 1

[0063] In Table 1, the control group was formed by replacing the spherical cerium dioxide powder in the paste with an equal amount of nano titanium dioxide in the UVA and UVB average transmittance tests. That is, the paste contained 10wt% nano titanium dioxide, and the average particle size D50 of titanium dioxide was 200nm.

[0064] As shown in Table 1, the impurity content of the spherical cerium dioxide obtained in Examples 1 and 2 is less than 0.1 ppm. Among them, the particle size of Example 1 is smaller and the distribution is more uniform, showing better particle concentration and ultraviolet blocking performance. After adjusting the parameters such as cerium source, raw material ratio and concentrated solid content, spherical cerium dioxide with low impurity content can still be obtained in Example 2, but the particle size is increased.

[0065] In Comparative Example 1, replacing cerium carbonate with an equal amount of cerium sulfate resulted in increased particle size, higher dispersion index, higher impurity content, and higher average UVA and UVB transmittance, indicating a decrease in both purity and UV blocking performance. This may be because sulfate ions affect the complexation state of cerium ions, precipitation rate, and the growth process of colloidal particles, leading to uneven particle growth, a wider particle size distribution, and an increased risk of impurity residue or entrainment.

[0066] Comparative Example 2 used only citric acid as the organic acid. Although citric acid alone can complex cerium ions, it is insufficient in controlling the hydrolysis, precipitation, and gelation processes of the system, easily leading to a significant widening of the particle size distribution and making impurity ions more prone to co-precipitation, adsorption, or encapsulation. In contrast, Example 1 uses a combination of citric acid and γ-hydroxybutyric acid, which can form a strong-weak complexing synergistic system. This is beneficial for stabilizing cerium ions and improving the uniformity of particle nucleation and growth during the sol-gel process, thereby obtaining a lower impurity content and a more concentrated particle size distribution.

[0067] Comparative Examples 3 and 4 show that when the amounts of ammonia and ammonium carbonate are too low, the system is insufficiently alkaline, making it difficult for cerium ion hydrolysis precipitation and sol-gel reactions to proceed stably. Specifically, a low ammonia source concentration leads to fluctuations in the reaction rate and an increase in impurities; further reductions in the ammonia source concentration prevent the reaction from proceeding completely, making it difficult to form nanoparticles. This indicates that appropriate amounts of ammonia and ammonium sources play a crucial role in maintaining an alkaline buffer environment, promoting the uniform formation of cerium precursors, and reducing impurity entrainment.

[0068] The pH of the reaction system in Comparative Example 5 was acidic, which led to insufficient sol-gel reaction, failure to form a regular spherical morphology, and a decrease in UV blocking performance.

[0069] In Comparative Example 6, replacing the complex organic acid with a citric acid / butyric acid system significantly broadened the particle size distribution and reduced UV blocking performance. This is because butyric acid lacks hydroxyl groups, resulting in weaker auxiliary complexing, hydrogen bonding, and dispersion regulation capabilities compared to γ-hydroxybutyric acid, making it difficult to effectively improve the uniform nucleation and growth process of cerium precursor particles.

Claims

1. A method for preparing spherical cerium dioxide, characterized in that, Includes the following steps: S1. Mix cerium source, water, nitric acid, and mixed organic acid, and purify to obtain a mixed solution; wherein the mixed organic acid includes citric acid and γ-hydroxybutyric acid, and the volume ratio of nitric acid, mixed organic acid, and water is 2:3~5:150~200. S2. Add ammonia and ammonium source to the mixed solution, control the mass ratio of ammonia, ammonium source and water in step S1 to be 6~10:5:30~100, and make the pH of the system 9~12. Carry out the sol-gel reaction at 20~95℃ for 2~240h to obtain the reaction solution. S3. The reaction solution is concentrated and spray-dried to obtain spherical cerium dioxide.

2. The preparation method according to claim 1, characterized in that, The cerium source is selected from at least one of cerium carbonate, cerium nitrate, and cerium hydroxide; And / or, in the mixed solution, the concentration of the cerium source is 0.025~10 wt%; And / or, the mass ratio of citric acid to γ-hydroxybutyric acid is 1:1~5.

3. The preparation method according to claim 1, characterized in that, The purification is performed by recrystallization; and / or the purification is performed until the purity of the resulting solution reaches 9N or higher.

4. The preparation method according to claim 1, characterized in that, The concentration of the ammonia water is 0.1wt%~10wt%, and the purity is ≥9N; And / or, the ammonium source is ammonium carbonate with a purity ≥99.99%; And / or, the molar ratio of ammonia to ammonium source in the ammonia water is 1:0.4-2.

5. The preparation method according to claim 1, characterized in that, The sol-gel reaction is stirred at a speed of 5-500 rpm.

6. The preparation method according to claim 1, characterized in that, The concentration process results in a liquid with a solid content of 5-30 wt%; and / or the concentration temperature is 25-75°C, and the concentration time is 3-24 h.

7. The preparation method according to claim 1, characterized in that, The inlet temperature of the spray drying is 20~80℃, the liquid flow rate is ≥1L / min, and the nozzle pressure is ≥0.1MPa; and / or, the spray drying is followed by a re-drying treatment, the temperature of the re-drying treatment is 40~200℃, and the drying time is 0.5~3h.

8. A spherical cerium dioxide, characterized in that, The spherical cerium dioxide is prepared by the preparation method described in any one of claims 1 to 7.

9. The spherical cerium dioxide according to claim 8, characterized in that, The spherical cerium oxide particles, as measured by a laser particle size analyzer, have a particle size D50 of 100~2000nm, a dispersion index (D90-D10) / D50 of [value missing], and an impurity content ≤0.1ppm.

10. The use of spherical cerium dioxide as described in claim 8 or 9 in the preparation of cosmetics.

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