CeO2 particles and their preparation method

Abstract

This invention discloses CeO2 particles and a method for preparing the same. The preparation method includes the following steps: 1) mixing an aqueous solution of cerium salt with an ionic liquid to obtain a mixture; 2) reacting the mixture at 150–240°C, and after the reaction, obtaining a precursor through solid-liquid separation; 3) calcining the precursor to obtain CeO2 particles. Using the preparation method of this invention, CeO2 particles with a particle size of 100–500 nm and a similar polyhedral spherical shape can be obtained.

Description

Technical Field

[0001] This invention relates to CeO2 particles and a method for preparing the same. Background Technology

[0002] Cerium dioxide (CeO2), as a rare earth oxide, has attracted attention due to its unique physicochemical properties and is widely used in many fields such as chemical mechanical polishing, tribochemistry, and catalysis of precision optical glass and single-crystal silicon wafers for ultra-large-scale integrated circuits.

[0003] The key factors affecting the properties of micro and nano CeO2 are its morphology, size, and microstructure. CeO2 with different particle sizes, morphologies, and particle size distributions may have different applications.

[0004] To date, there are many methods for preparing CeO2 particles, such as coprecipitation, high-temperature calcination, melt milling, microemulsion, and sol-gel. The morphology and particle size of CeO2 obtained by different methods will vary.

[0005] CN104370300A discloses a method for hydrothermal synthesis of cerium oxide nanoparticles using cerium hydroxide as a precursor, adding different polymeric surfactants such as polyvinylpyrrolidone-K30, polyethylene glycol 2000, hexadecyltrimethylammonium bromide, and polyacrylic acid, and reacting at 150–180°C for 24–72 h, and preparing D after drying the precipitate. 50 It consists of highly dispersed, spherical cerium oxide particles ranging from 0.2 nm to 1.1 μm.

[0006] CN109516490B discloses a method for preparing cerium dioxide nanoparticles with controllable structure, comprising: adding 1g of polyvinylpyrrolidone to 13mL of ethylene glycol and stirring until homogeneous to obtain solution A; adding 2.1711g of cerium nitrate hexahydrate to 20mL of ethylene glycol and 2mL of water and stirring until homogeneous to obtain solution B; slowly adding solution B to solution A and slowly adding 2mL of acetic acid to obtain a mixed solution; placing the mixed solution in a microwave reactor for reaction, heating to 100℃ for 10min and holding for 10min; heating to 160℃ for 10min and holding for 20min, centrifuging to separate, washing and drying the solid to obtain a crude product; calcining the crude product at 500℃ for 1h to obtain cerium dioxide nanoparticles resembling short rods.

[0007] CN115448354A discloses a method for preparing cerium dioxide particles, comprising the following steps: 1) mixing a water-soluble cerium salt and a polyol in a molar ratio of 1:100-5000 to obtain a mixed solution; 2) subjecting the mixed solution to microwave digestion in a microwave digester to obtain a precursor reaction solution; wherein the microwave treatment temperature is 120-200℃ and the time is 15-60 min; 3) separating the precursor reaction solution into solid and liquid phases, washing and drying the obtained solid to obtain a precursor; 4) calcining the precursor to obtain cerium dioxide particles; wherein the cerium dioxide particles are spherical with a particle size D. 50 The wavelength range is 100–300 nm.

[0008] Ionic liquids, as a novel type of green solvent, are ionic compounds composed entirely of cations and anions, also known as organic salts. Compared with traditional organic solvents, ionic liquids are liquid at temperatures close to 100°C and have advantages such as low vapor pressure (i.e., non-volatile), low melting point, wide liquid phase temperature window (up to 400°C), low toxicity, wide potential window, and good solubility for both organic and inorganic substances.

[0009] Currently, most literature reports on the preparation of other oxide nanoparticles using ionic liquids as template agents, while there are few reports on the preparation of CeO2 particles using ionic liquids as solvents.

[0010] CN116832859A discloses a method for preparing an ionic liquid-modified cerium dioxide catalyst, comprising: adding a certain amount of solvent 1 to a glass vial, adding a certain amount of cerium salt, and stirring until homogeneous; wherein, solvent 1 is a methanol solution containing an ionic liquid, and the mass percentage of the ionic liquid in the solvent is 0-25 wt%; transferring the glass vial to a polytetrafluoroethylene liner containing solvent 2, reacting in an oven, and after the reaction is completed, cooling, washing, and drying to obtain the ionic liquid-modified cerium dioxide catalyst. Solvent 2 is deionized water or methanol. This patent document obtains a cerium dioxide precursor as a catalyst, but does not obtain CeO2 particles, nor does it mention their morphology and particle size. Summary of the Invention

[0011] In view of this, one object of the present invention is to provide a method for preparing CeO2 particles, wherein the CeO2 particles obtained by this method are basically multifaceted spherical with a particle size of 100-500 nm. The CeO2 particles prepared by the present invention have good crystallinity, regular morphology, and uniform dispersion. Another object of the present invention is to provide CeO2 particles obtained by the above method. The present invention achieves the above objects using the following technical solutions.

[0012] On one hand, the present invention provides a method for preparing CeO2 particles, comprising the following steps:

[0013] 1) Mix an aqueous solution of cerium salt with an ionic liquid to obtain a mixture;

[0014] 2) The mixture is reacted at 150–240 °C. After the reaction is complete, the precursor is obtained by solid-liquid separation.

[0015] 3) The precursor was calcined to obtain CeO2 particles.

[0016] According to the preparation method of the present invention, preferably, the cerium salt is selected from one or more of cerium chloride, cerium carbonate, and cerium nitrate.

[0017] According to the preparation method of the present invention, preferably, the cerium salt is cerium nitrate.

[0018] According to the preparation method of the present invention, preferably, the concentration of the aqueous solution of the cerium salt is 0.1 to 10.0 mol / L.

[0019] According to the preparation method of the present invention, preferably, the mass ratio of the cerium salt to the ionic liquid is 1:10 to 500.

[0020] According to the preparation method of the present invention, preferably, the cation in the ionic liquid is an imidazole class, and the anion is PF6. - .

[0021] According to the preparation method of the present invention, preferably, the ionic liquid is 1-butyl-3-methylimidazolium hexafluorophosphate.

[0022] According to the preparation method of the present invention, preferably, in step 2), the mixture is reacted at 150-240°C for 5-36 hours. After the reaction is completed, the solid and liquid are separated, and the solid is washed and dried to obtain the precursor.

[0023] According to the preparation method of the present invention, preferably, in step 3), the calcination temperature is 550-1000℃ and the calcination time is 1-6h.

[0024] On the other hand, the present invention also provides CeO2 particles obtained according to the preparation method described above.

[0025] The CeO2 particles prepared by the method of the present invention are basically multifaceted spherical, with a particle size of 100–500 nm. Furthermore, the CeO2 particles prepared by the present invention have good crystallinity, regular morphology, and uniform dispersion. The preparation process of the present invention is simple, without the addition of any other surfactants or dispersants, and without the introduction or generation of toxic or harmful substances. It avoids the problems existing in conventional methods, such as high vapor pressure, flammability, toxicity, solvent evaporation, and narrow heating temperature range, thus meeting the requirements of green chemistry. Attached Figure Description

[0026] Figure 1 This is a SEM image of the CeO2 particles obtained in Example 1 of the present invention.

[0027] Figure 2 The image shows the XRD pattern of CeO2 particles obtained in Example 1 of this invention.

[0028] Figure 3 This is a SEM image of the CeO2 particles obtained in Comparative Example 1 of the present invention. Detailed Implementation

[0029] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0030] The method for preparing CeO2 particles according to the present invention includes the following steps: (1) a mixing step; (2) a reaction and post-treatment step; and (3) a calcination step. These steps are described in detail below.

[0031] <Mixing Steps>

[0032] An aqueous solution of cerium salt is mixed with an ionic liquid to obtain a mixture.

[0033] In this invention, the cerium salt is a water-soluble cerium salt. The cerium salt is selected from one or more of cerium chloride, cerium carbonate, and cerium nitrate. Preferably, the cerium salt is selected from one of cerium chloride, cerium carbonate, and cerium nitrate. More preferably, the cerium salt is cerium nitrate.

[0034] In this invention, the cerium salts can be their corresponding hydrates.

[0035] In this invention, the concentration of the aqueous solution of the cerium salt is 0.1–10.0 mol / L, preferably 0.2–5.0 mol / L, even more preferably 0.3–1.0 mol / L, and more preferably 0.4–0.8 mol / L. This is beneficial for controlling the resulting cerium oxide particles to be similar to polyhedral spheres.

[0036] In this invention, the cation in the ionic liquid is an imidazole class, such as 1-butyl-3-methylimidazolium, 1-ethyl-2,3-dimethylimidazolium, 1-propyl-3-methylimidazolium, etc., and the anion is PF6. - According to one embodiment of the present invention, the ionic liquid is 1-butyl-3-methylimidazolium hexafluorophosphate. The purity of the ionic liquid is 99.5% or higher, preferably 99.9% or higher.

[0037] The mass ratio of cerium salt to ionic liquid can be 1:10 to 500, preferably 1:15 to 400, more preferably 1:20 to 300, even more preferably 1:25 to 200, and still more preferably 1:30 to 100. Extensive research and experiments have shown that reacting ionic liquid with cerium salt of a specific concentration can yield cerium dioxide with a generally polyhedral spherical particle size within a specific range, exhibiting relatively regular morphology and good dispersibility.

[0038] In some embodiments, an aqueous solution of cerium salt is added to an ionic liquid under stirring to obtain a mixture. No surfactants or dispersants are added during the mixing process.

[0039] <Reaction and Post-processing Steps>

[0040] The mixture was reacted at 150–240 °C. After the reaction was complete, the precursor was obtained by solid-liquid separation. This method is beneficial for controlling the morphology and particle size of the resulting CeO2 particles.

[0041] The reaction temperature can be 150–240°C, preferably 150–220°C, even more preferably 160–210°C, and even more preferably 180–210°C. The reaction time can be 5–36 h, preferably 10–30 h, even more preferably 15–25 h, and even more preferably 16–20 h.

[0042] Solid-liquid separation can be achieved through filtration or centrifugation, with centrifugation being preferred. After solid-liquid separation, the obtained solid is washed and dried to obtain the precursor. Washing can be performed using a C1-C3 alkyl alcohol as a solvent. The C1-C3 alkyl alcohol is selected from methanol, ethanol, or isopropanol, preferably ethanol, and more preferably anhydrous ethanol. This facilitates the removal of excess ionic liquid and the recovery of the ionic liquid.

[0043] Drying can be performed using an oven or a vacuum drying oven. The drying temperature can be 50–90°C, preferably 60–85°C, and more preferably 70–80°C. The drying time can be 5–20 hours, preferably 7–18 hours, and more preferably 8–15 hours.

[0044] According to a specific embodiment of the present invention, the mixture is placed in a polytetrafluoroethylene reactor and then reacted at 150-240°C for 5-36 hours. After the reaction is completed, the solid and liquid are separated, and the solid is washed and dried to obtain the precursor.

[0045] This invention uses ionic liquid as a solvent to synthesize CeO2 particles with good crystallinity, uniform dispersion, and specific morphology without any template agent.

[0046] <Roasting Steps>

[0047] The precursor was calcined to obtain CeO2 particles.

[0048] The calcination temperature can be 550–1000℃, preferably 600–900℃, more preferably 650–800℃, and even more preferably 700–750℃. The calcination time can be 1–6 hours, preferably 2–5 hours, and more preferably 2–4 hours. This is beneficial for obtaining CeO2 particles with good dispersibility.

[0049] According to one embodiment of the present invention, the method for preparing CeO2 particles includes the following specific steps:

[0050] 1) Mix an aqueous solution of cerium salt (0.1–10.0 mol / L) with an ionic liquid to obtain a mixture;

[0051] 2) React the mixture at 150–240 °C for 5–36 h. After the reaction is complete, perform solid-liquid separation, washing, and drying to obtain the precursor.

[0052] 3) The precursor was calcined at 550–1000℃ for 1–6 h to obtain CeO2 particles;

[0053] The CeO2 particles have a particle size of 100–500 nm and are basically multifaceted spherical.

[0054] The present invention has found that the precursor obtained by the method of the present invention can produce CeO2 particles with a diameter of 100-500 nm that are basically multifaceted spherical under the calcination conditions of the present invention. If the method of the present invention is not used, for example, the modified cerium dioxide catalyst method of Example 1 in the prior art CN116832859A is used, the CeO2 particles of the present invention cannot be obtained.

[0055] The CeO2 particles obtained by the method of this invention are similar to polyhedral spheres, with a particle size of 100–500 nm, preferably 200–500 nm, and more preferably 200–400 nm. They exhibit good crystallinity, relatively regular morphology, and good dispersibility. The polyhedral spheres mentioned in this invention refer to spheres with facets. These facets can be planar, circular, or polygonal, and are not fixed.

[0056] The test methods for the following embodiments and comparative examples are described below:

[0057] SEM: Tests were performed using a ZEISS Sigma 500 field emission scanning electron microscope.

[0058] XRD: Tests were performed using an X'Pert PRO X-ray diffractometer.

[0059] Example 1

[0060] Cerium nitrate hexahydrate was prepared into an aqueous solution with a molar concentration of 0.5 mol / L to obtain an aqueous solution of cerium salt.

[0061] Add 2 mL of the prepared cerium salt aqueous solution to 20 mL of 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid and stir thoroughly at room temperature for 30 min to obtain a mixture.

[0062] The mixture was placed in a polytetrafluoroethylene reactor and reacted at 180°C for 16 hours. After the reaction was completed, the mixture was cooled to room temperature and centrifuged to obtain a white precipitate. The white precipitate was washed three times with anhydrous ethanol. The washed solid was placed in an oven and dried at 80°C for 10 hours to obtain the precursor.

[0063] The precursor was placed in a muffle furnace and calcined at 700°C for 2 hours. After cooling, it was ground to obtain CeO2 particles.

[0064] The SEM results of the CeO2 particles obtained in Example 1 are shown below. Figure 1 XRD results are shown in Figure 2 .

[0065] from Figure 1 It can be seen that CeO2 particles have small and relatively uniform particle size, ranging from 200 to 400 nm, and are shaped like a multifaceted sphere with good dispersibility.

[0066] from Figure 2 As can be seen, the peaks are very sharp, indicating that the CeO2 in the obtained particles has good crystallinity, and there is only one CeO2 diffraction peak corresponding to the standard data JCPDS No. 34-0394, so only the CeO2 phase appears.

[0067] Example 2

[0068] Cerium nitrate hexahydrate was prepared into an aqueous solution with a molar concentration of 1 mol / L to obtain an aqueous solution of cerium salt.

[0069] Add 5 mL of the prepared cerium salt aqueous solution to 20 mL of 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid and stir thoroughly at room temperature for 30 min to obtain a mixture.

[0070] The mixture was placed in a polytetrafluoroethylene reactor and reacted at 200°C for 20 h. After the reaction was completed, it was cooled to room temperature and centrifuged to obtain a white precipitate. The white precipitate was washed three times with anhydrous ethanol. The washed solid was placed in an oven and dried at 80°C for 10 h to obtain the precursor.

[0071] The precursor was placed in a muffle furnace and calcined at 700°C for 2 hours. After cooling, it was ground to obtain CeO2 particles. The obtained CeO2 particles had a particle size within 500 nm and a shape similar to a multifaceted sphere.

[0072] Comparative Example 1

[0073] Cerium nitrate hexahydrate was prepared into an aqueous solution with a molar concentration of 0.2 mol / L to obtain an aqueous solution of cerium salt.

[0074] Add 5 mL of the prepared cerium salt aqueous solution to 20 mL of 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid and stir thoroughly at room temperature for 30 min to obtain a mixture.

[0075] The mixture was placed in a polytetrafluoroethylene reactor and reacted at 240°C for 5 hours. After the reaction was completed, it was cooled to room temperature and centrifuged to obtain a white precipitate. The white precipitate was washed three times with anhydrous ethanol. The washed solid was placed in an oven and dried at 80°C for 10 hours to obtain the precursor.

[0076] The precursor was placed in a muffle furnace and calcined at 500°C for 2 hours. After cooling, it was ground to obtain CeO2 particles.

[0077] The SEM results of the CeO2 particles obtained in this comparative example are shown in [the figure]. Figure 3 .from Figure 3 It can be seen that the CeO2 particles are still in the nanometer range, but they are not uniform in size. The particle size is between 100-600 nm, and the morphology varies greatly. Some are similar to multifaceted spheres, while others are short rods.

[0078] This invention is not limited to the above-described embodiments. Any modifications, improvements, or substitutions that can be conceived by those skilled in the art without departing from the essential content of this invention fall within the scope of this invention.

Claims

1. A method for preparing CeO2 particles, characterized in that, Includes the following steps: 1) A 0.4–1 mol / L aqueous solution of a cerium salt is mixed with an ionic liquid to obtain a mixture; wherein the mass ratio of the cerium salt to the ionic liquid is 1:10–100; the cation in the ionic liquid is an imidazole derivative, and the anion is PF6. - ; 2) React the mixture at 160–210 °C for 15–20 h. After the reaction is complete, perform solid-liquid separation, washing, and drying to obtain the precursor. 3) The precursor was calcined at 550–1000℃ for 1–6 h to obtain CeO2 particles; The CeO2 particles have a particle size of 100–500 nm and are basically multifaceted spherical.

2. The preparation method according to claim 1, characterized in that, The cerium salt is selected from one or more of cerium chloride and cerium nitrate.

3. The preparation method according to claim 1, characterized in that, The cerium salt is cerium nitrate.

4. The preparation method according to claim 1, characterized in that, The ionic liquid is 1-butyl-3-methylimidazolium hexafluorophosphate.

5. CeO2 particles obtained by the preparation method according to any one of claims 1 to 4.

Images