Preparation method of cerium oxide nanoparticles with ultra-small particle size

Abstract

The invention discloses a preparation method of ultra-small cerium oxide nanoparticles, which comprises the following steps: preparing a mixed solution from magnesium sulfate and cerium salt, adding organic solvents such as ethanol, precipitating cerium-containing magnesium sulfate heptahydrate, drying to obtain cerium-containing anhydrous magnesium sulfate, and calcining the dried substance below the decomposition temperature of magnesium sulfate to obtain cerium-containing anhydrous magnesium sulfate; and washing the mixture with water to obtain the high-dispersion cerium oxide nano-particles with the ultra-small particle size, wherein the high-dispersion cerium oxide nano-particles with the ultra-small particle size are obtained. According to the method, high-temperature sintering of the cerium oxide nano-particles can be avoided, the high-dispersion cerium oxide nano-particles with the particle size being only 3-4 nm are prepared, the process cost is low, and large-scale production is easy to achieve.

Description

Technical Field

[0001] The invention belongs to the field of nano particle material preparation, and relates to a method for preparing ultra-small-diameter cerium oxide nano particles. Background Art

[0002] Cerium oxide nanoparticles have a wide range of applications in the fields of optical glass polishing, catalysis, ultraviolet absorption materials, solid oxide fuel cells, gas sensors, etc. For example, cerium oxide nanoparticles have an irreplaceable position in the fields of high-precision optical components, photolithography machine lenses, and integrated circuit polishing; in cosmetic applications, nano-cerium oxide has strong absorption of ultraviolet rays and high transparency to visible light, and can be used in anti-ultraviolet sunscreen products. It does not turn white when applied to the skin, and the effect is obvious due to titanium dioxide products; nano-scale cerium oxide particles have a wide absorption band in the range of 300-450nm, which is more efficient than organic anti-ultraviolet absorbers; in automobile exhaust purification applications, cerium oxide nanoparticles have a large specific surface area and high oxygen storage capacity, and can control the precious metal particles in the catalyst to be at the nano level, greatly improving the catalytic activity; in solid oxide fuel cells, nano-scale cerium oxide has a large specific surface area and high reaction activity, which further increases the ability to store and transfer oxygen; cerium oxide nanoparticles also show excellent performance in photocatalytic degradation of wastewater technology.

[0003] In all the above-mentioned application environments of cerium oxide nanoparticles, it is hoped that the particle size of cerium oxide nanoparticles is as small as possible. For example, small-sized cerium oxide nanoparticles have stronger ultraviolet absorption performance; the smaller the particle size, the better the catalytic performance of nano-cerium oxide; high-precision lithography machine lenses require that the particle size of nano-cerium oxide used for polishing is 10nm, and the particles are uniform and dispersed. Therefore, particle size and dispersibility have become the main indicators for evaluating the performance of cerium oxide nanoparticles.

[0004] The preparation methods of cerium oxide nanoparticles mainly include solid phase method and liquid phase method. The solid phase method is to use cerium oxalate, carbonate or basic carbonate to calcine at high temperature, but it is difficult to prepare small particle size and highly dispersed cerium oxide nanoparticles by this method; the liquid phase method refers to a method of obtaining cerium oxide nanoparticles or precursors of cerium oxide nanoparticles by physical or chemical processes through liquid, and then calcining at high temperature to obtain cerium oxide nanoparticles. Common liquid phase methods include precipitation method, hydrothermal method, microemulsion method and sol-gel method. The typical process of precipitation method is to prepare cerium salt solution with cerous nitrate, cerium acetate, cerium chloride, etc., add precipitants such as inorganic alkali, carbonate, oxalic acid or oxalate, and then dry the precipitate and calcine at high temperature to obtain cerium oxide nanoparticles. However, this method cannot avoid the sintering of nanoparticles during high temperature calcination, and it is difficult to obtain dispersed cerium oxide nanoparticles. The hydrothermal method uses a reactor to prepare cerium oxide nanoparticles in a high-temperature, high-pressure reaction environment. This method can produce cerium oxide nanoparticles with good dispersibility and narrow particle size distribution, but this method is cumbersome to operate, has low preparation efficiency, and is prone to residual hydroxyl groups and impurity elements.

[0005] In the early stage, our research group studied a variety of technologies for preparing nanoparticle materials by water-soluble salt isolation method to solve the problem of high-temperature sintering of nanoparticles. For example, Chinese invention patent CN201610699775.1 first prepares a transparent hydrosol containing water-soluble salt and oxide precursor nanoparticles, then precipitates with a weak polar solvent, calcines after drying, and washes with water to obtain oxide nanoparticles. Invention patent CN 201810037875.7 first prepares a mixed solution of metal sulfate and potassium sulfate containing polyacrylic acid, then precipitates with a weak polar organic solvent to obtain a mixture of metal sulfate and potassium sulfate nanoparticles, and then calcines at high temperature and washes with water to obtain dispersed metal oxide nanoparticles. CN202210450039.8 first prepares a mixed solution with water-soluble salt, cerium and a complex of doped elements, precipitates cerium and the complex of doped elements and water-soluble salt, and then calcines and washes with water to obtain highly dispersed cerium oxide-based nanoparticles. However, although the above-mentioned salt isolation methods can prepare cerium oxide nanoparticles, their particle sizes are all over 10 nm, and ultra-small cerium oxide nanoparticles cannot be obtained.

[0006] In summary, the existing cerium oxide preparation technology has problems such as easy sintering of particles, low preparation efficiency or residual impurities, making it difficult to prepare ultra-small particle size and highly dispersed cerium oxide nanoparticles. Summary of the invention

[0007] Technical problem: The purpose of the present invention is to provide a method for preparing ultra-small particle size cerium oxide nanoparticles which can solve the particle sintering problem of cerium oxide nanoparticles and has a simple process and high production efficiency. Another purpose of the present invention is to provide cerium oxide nanoparticles prepared by this method.

[0008] Technical solution: The present invention provides a method for preparing ultra-small particle size cerium oxide nanoparticles, comprising the following steps:

[0009] (1) dissolving magnesium sulfate or a magnesium sulfate precursor and a cerium salt in water to obtain a mixed solution containing cerium and magnesium sulfate;

[0010] (2) mixing an organic solvent with the mixed solution to obtain a precipitate, wherein the precipitate includes a magnesium sulfate heptahydrate phase containing cerium;

[0011] (3) drying the precipitate, and calcining the precipitate below the decomposition temperature of magnesium sulfate to obtain a mixture of cerium oxide nanoparticles and anhydrous magnesium sulfate;

[0012] (4) removing magnesium sulfate from the mixture to obtain cerium oxide nanoparticles.

[0013] Furthermore, in step (1), the amount of magnesium sulfate is not less than the amount of cerium ions in terms of molar amount, and the obtained mixed solution is a uniform mixed solution.

[0014] Furthermore, in step (1), the magnesium sulfate is anhydrous magnesium sulfate and / or hydrated magnesium sulfate, and the magnesium sulfate precursor is a water-soluble salt containing sulfate and magnesium ions.

[0015] Furthermore, in step (1), the cerium salt is at least one of cerous nitrate, cerous sulfate and cerous sulfate.

[0016] Furthermore, in step (1), the molar ratio of magnesium sulfate to cerous nitrate is ≥ 2, the molar ratio of magnesium sulfate to cerous sulfate is ≥ 10, and the molar ratio of magnesium sulfate to ceric sulfate is ≥ 5. Under these conditions, the cerium salt is fully isolated by magnesium sulfate and the obtained mixed solution is clear.

[0017] Furthermore, in step (2), the organic solvent is one or a mixture of ethanol, methanol, propanol, isopropanol, tert-butanol, diethylene glycol, pyridine, dioxane, tetrahydrofuran, acetone, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol propyl ether, ethylene glycol butyl ether, diethylene glycol butyl ether, dimethyl sulfoxide or dimethylformamide.

[0018] Furthermore, in step (3), the calcination temperature is 300-700°C.

[0019] Furthermore, in step (3), the calcination time is not less than 1 hour.

[0020] Furthermore, in step (4), magnesium sulfate in the mixture is removed by washing with water.

[0021] The cerium oxide nanoparticles prepared by the above method have a particle size of less than 5nm.

[0022] The invention prepares a mixed solution containing cerium salt and magnesium sulfate, then adds an organic solvent to precipitate magnesium sulfate heptahydrate containing cerium, dries to obtain anhydrous magnesium sulfate containing cerium, and calcines the dried product at below 700°C to obtain a mixture of nano cerium oxide and magnesium sulfate, in which ultra-small particle size nano cerium oxide is embedded in micropores inside anhydrous magnesium sulfate particles, and then highly dispersed ultra-small particle size cerium oxide nano particles are obtained after washing to remove magnesium sulfate.

[0023] Beneficial effects: Compared with the prior art, the present invention has the following advantages: 1. The obtained cerium oxide has a small particle size of less than 5nm, and is uniformly dispersed / has a narrow particle size distribution range: the obtained cerium oxide nanoparticles have a particle size range of 3 to 4nm and are uniformly distributed, which effectively avoids sintering problems; 2. The process of the present invention is very simple and suitable for mass production; 3. No high temperature or high pressure equipment is required, and the production safety is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The cerium oxide nanoparticles are prepared according to Example 1 of the present invention;

[0025] Figure 2 The cerium oxide nanoparticles are prepared according to the scheme of Example 3 of the present invention;

[0026] Figure 3 These are cerium oxide nanoparticles prepared according to Example 5 of the present invention.

[0027] Figure 4 This is the XRD diagram of the precipitate obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0028] The preferred embodiments of the present invention are described in detail below.

[0029] In the present invention, the organic solvent that can dissolve mutually with water and can make water-soluble salt and cerium and doping element complex solubility reduce all can be applicable.The organic solvent used for the present invention can be ethanol, methanol, propyl alcohol, isopropanol, the tert-butyl alcohol, diethylene glycol, pyridine, dioxane, tetrahydrofuran, acetone, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol propyl ether, ethylene glycol butyl ether, diethylene glycol butyl ether, dimethyl formamide or dimethyl sulfoxide.From the perspective of chemical stability, toxicity and economy, preferably ethanol, propyl alcohol, isopropanol, the tert-butyl alcohol, diethylene glycol, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol propyl ether, ethylene glycol butyl ether, diethylene glycol butyl ether, dimethyl sulfoxide or dimethyl formamide.

[0030] In the present invention, cerium oxide can be generated at temperatures above 300°C, but magnesium sulfate begins to decompose when calcined at temperatures above 700°C, and magnesium oxide remains after the product is washed with water, requiring further impurity removal, which increases process costs. Therefore, the calcination temperature of the present invention is not higher than 700°C.

[0031] The preparation method of the present invention is further described in detail below in conjunction with specific examples.

[0032] Example 1: Weigh 2 mol of anhydrous magnesium sulfate and 0.1 mol of cerium nitrate and prepare a 1 liter mixed solution with deionized water. Add 500 ml of ethanol to obtain a precipitate, dry it, calcine it at 600°C, cool it, wash it with water 2-3 times, and dry it to obtain ultra-small particle size cerium oxide nanoparticles. The test results of the cerium oxide nanoparticles obtained in this example are as follows: Figure 1 shown.

[0033] In this embodiment, a mixed solution containing cerium salt and magnesium sulfate is first prepared, in which the cerium element is evenly distributed at the ion level. After adding an organic solvent, the solubility of magnesium sulfate in the solution is reduced and precipitated from water. The elemental analysis results of the supernatant and the precipitate show that the cerium element is all distributed in the precipitate. Further phase analysis of the precipitate shows that Figure 4 As shown, the result is a pure magnesium sulfate heptahydrate phase, and no second phase is found. In the crystal structure of magnesium sulfate heptahydrate, crystal water occupies a large proportion, one of which is coordinated with sulfate, and six of which form a coordination structure with magnesium ions. Combined with the ultra-small particle size cerium oxide finally prepared, we believe that in the precipitate, the cerium element is combined with the crystal water of hydrated magnesium sulfate in some form. During the drying and high-temperature calcination process, magnesium sulfate heptahydrate loses its crystal water and becomes porous anhydrous magnesium sulfate particles, and the generated cerium oxide is embedded in the micropores of the anhydrous magnesium sulfate particles. Therefore, the ultra-small particle size cerium oxide nanoparticles formed are always dispersed and isolated by magnesium sulfate, thereby effectively solving the high-temperature sintering problem of nanoparticles. Therefore, ultra-small particle size cerium oxide particles below 5nm can be prepared after washing.

[0034] Our research group has not found any reports on this phenomenon in the literature, nor has it found any reports on the use of this phenomenon in the known technical means in the field to prepare nanoparticle materials, and there is no report on the preparation of cerium oxide particle materials less than 5nm.

[0035] Example 2: Weigh 2 mol of anhydrous magnesium sulfate and 0.1 mol of cerium nitrate and prepare a 1 liter mixed solution with deionized water. Add 500 ml of propanol to obtain a precipitate, dry it, calcine it at 600°C, cool it, wash it with water 2-3 times, and dry it to obtain ultra-small particle size (less than 5 nm) cerium oxide nanoparticles.

[0036] Example 3: Weigh 2 mol of anhydrous magnesium sulfate and 0.1 mol of cerium nitrate and prepare a 1 liter mixed solution with deionized water. Add 500 ml of isopropanol to obtain a precipitate, dry it, calcine it at 600°C, cool it, wash it with water 2-3 times, and dry it to obtain ultra-small particle size cerium oxide nanoparticles. The test results of the cerium oxide nanoparticles obtained in this example are as follows: Figure 2As shown, the particle size is less than 5 nm and the dispersion is good.

[0037] Example 4: Weigh 2 mol of anhydrous magnesium sulfate and 0.1 mol of cerium nitrate, and prepare a 1 liter mixed solution with deionized water. Add 500 ml of tert-butyl alcohol to obtain a precipitate, dry it, calcine it at 600°C, cool it, wash it with water 2-3 times, and dry it to obtain ultra-small particle size cerium oxide nanoparticles.

[0038] Example 5: Weigh 2 mol of anhydrous magnesium sulfate and 0.1 mol of cerium nitrate and prepare a 1 liter mixed solution with deionized water. Add 500 ml of diethylene glycol to obtain a precipitate, dry it, calcine it at 700°C, cool it, wash it with water 2-3 times, and dry it to obtain ultra-small particle size cerium oxide nanoparticles. The test results of the cerium oxide nanoparticles obtained in this example are as follows: Figure 3 As shown, the particle size is less than 5 nm. Since the boiling point of diethylene glycol is as high as 245°C, the de-crystallization water of magnesium sulfate heptahydrate and the precipitation of cerium oxide are both completed in a diethylene glycol environment, and the dispersibility of the obtained nano-cerium oxide is slightly poor.

[0039] Example 6: Weigh 2 mol of anhydrous magnesium sulfate and 0.1 mol of cerium nitrate and prepare a 1 liter mixed solution with deionized water. Add 500 ml of ethylene glycol methyl ether to obtain a precipitate, dry it, calcine it at 600°C, cool it, and wash it with water 2-3 times. After drying, ultra-small cerium oxide nanoparticles with a particle size of less than 5 nm and good dispersibility can be obtained.

[0040] Example 7: Weigh 2 mol of anhydrous magnesium sulfate and 0.1 mol of cerium nitrate, and prepare a 1 liter mixed solution with deionized water. Add 500 ml of ethylene glycol ether to obtain a precipitate, dry it, calcine it at 600°C, cool it, and wash it with water 2-3 times. After drying, ultra-small cerium oxide nanoparticles with a particle size of less than 5 nm and good dispersibility can be obtained.

[0041] Example 8: Weigh 2 mol of anhydrous magnesium sulfate and 0.1 mol of cerium nitrate, and prepare a 1 liter mixed solution with deionized water. Add 500 ml of ethylene glycol propyl ether to obtain a precipitate, dry it, calcine it at 600°C, cool it, and wash it with water 2-3 times. After drying, ultra-small cerium oxide nanoparticles with a particle size of less than 5 nm and good dispersibility can be obtained.

[0042] Example 9: Weigh 2 mol of anhydrous magnesium sulfate and 0.1 mol of cerium nitrate and prepare a 1 liter mixed solution with deionized water. Add 500 ml of ethylene glycol butyl ether to obtain a precipitate, dry it, calcine it at 600°C, cool it, and wash it with water 2-3 times. After drying, ultra-small cerium oxide nanoparticles with a particle size of less than 5 nm and good dispersibility can be obtained.

[0043] Example 10: Weigh 2 mol of anhydrous magnesium sulfate and 0.1 mol of cerium nitrate and prepare a 1 liter mixed solution with deionized water. Add 500 ml of diethylene glycol butyl ether to obtain a precipitate, dry it, calcine it at 600°C, cool it, and wash it with water 2-3 times. After drying, ultra-small cerium oxide nanoparticles with a particle size of less than 5 nm and good dispersibility can be obtained.

[0044] Example 11: Weigh 2 mol of anhydrous magnesium sulfate and 0.1 mol of cerium nitrate and prepare a 1 liter mixed solution with deionized water. Add 500 ml of dimethyl sulfoxide to obtain a precipitate, dry it, calcine it at 600°C, cool it, and wash it with water 2-3 times. After drying, ultra-small cerium oxide nanoparticles with a particle size of less than 5 nm and good dispersibility can be obtained.

[0045] Example 12: Weigh 2 mol of anhydrous magnesium sulfate and 0.1 mol of cerium nitrate and prepare a 1 liter mixed solution with deionized water. Add 500 ml of dimethylformamide to obtain a precipitate, dry it, calcine it at 600°C, cool it, and wash it with water 2-3 times. After drying, ultra-small cerium oxide nanoparticles with a particle size of less than 5 nm and good dispersibility can be obtained.

[0046] Example 13: Weigh 2 mol of anhydrous magnesium sulfate and 0.1 mol of cerous sulfate, and prepare a 1 liter mixed solution with deionized water. Add 500 ml of ethanol to obtain a precipitate, dry it, calcine it at 600°C, cool it, and wash it with water 2-3 times. After drying, ultra-small cerium oxide nanoparticles with a particle size of less than 5 nm and good dispersibility can be obtained.

[0047] Example 14: Weigh 2 mol of anhydrous magnesium sulfate and 0.1 mol of cerium sulfate and prepare a 1 liter mixed solution with deionized water. Add 500 ml of ethanol to obtain a precipitate, dry it, calcine it at 600°C, cool it, and wash it with water 2-3 times. After drying, ultra-small cerium oxide nanoparticles with a particle size of less than 5 nm and good dispersibility can be obtained.

[0048] Example 15: Weigh 2 mol of anhydrous magnesium sulfate and 0.4 mol of cerium sulfate, and prepare a 1 liter mixed solution with deionized water. Add 500 ml of ethanol to obtain a precipitate, dry it, calcine it at 600°C, cool it, and wash it with water 2-3 times. After drying, ultra-small cerium oxide nanoparticles with a particle size of less than 5 nm and good dispersibility can be obtained.

[0049] Example 16: Weigh 2 mol of anhydrous magnesium sulfate and 1 mol of cerium nitrate, and prepare a 1 liter mixed solution with deionized water. Add 500 ml of ethanol to obtain a precipitate, dry it, calcine it at 600°C, cool it, and wash it with water 2-3 times. After drying, ultra-small cerium oxide nanoparticles with a particle size of less than 5 nm and good dispersibility can be obtained.

[0050] Example 17: Weigh 2 mol of anhydrous magnesium sulfate and 0.5 mol of cerium nitrate and prepare a 1 liter mixed solution with deionized water. Add 500 ml of ethanol to obtain a precipitate, dry it, calcine it at 400°C, cool it, and wash it with water 2-3 times. After drying, ultra-small cerium oxide nanoparticles with a particle size of less than 5 nm and good dispersibility can be obtained.

[0051] Comparative Example 1: 2 mol of magnesium sulfate and 0.5 mol of cerous sulfate were weighed and prepared into a mixed solution with 1 liter of deionized water. The obtained mixed solution could not be dissolved.

[0052] The above embodiments are only preferred implementation modes of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and equivalent substitutions without departing from the principles of the present invention. These technical solutions after improvements and equivalent substitutions to the claims of the present invention all fall within the protection scope of the present invention.

Claims

1. A method for preparing ultra-small particle size cerium oxide nanoparticles, characterized in that: The following steps are involved: (1) dissolving magnesium sulfate or a magnesium sulfate precursor and a cerium salt in water to obtain a mixed solution containing cerium and magnesium sulfate; (2) mixing an organic solvent with the mixed solution to obtain a precipitate, wherein the precipitate includes a magnesium sulfate heptahydrate phase containing cerium; (3) drying the precipitate, and calcining the precipitate below the decomposition temperature of magnesium sulfate to obtain a mixture of cerium oxide nanoparticles and anhydrous magnesium sulfate; (4) removing magnesium sulfate from the mixture to obtain cerium oxide nanoparticles.

2. The method for preparing ultra-small particle size cerium oxide nanoparticles according to claim 1, characterized in that: In step (1), the amount of magnesium sulfate is not less than the amount of cerium in terms of molar amount, and the obtained mixed solution is a uniform mixed solution.

3. The method for preparing ultra-small particle size cerium oxide nanoparticles according to claim 1 or 2, characterized in that: In step (1), the magnesium sulfate is anhydrous magnesium sulfate and / or hydrated magnesium sulfate, and the magnesium sulfate precursor is a water-soluble salt containing sulfate and magnesium ions.

4. The method for preparing ultra-small particle size cerium oxide nanoparticles according to claim 1 or 2, characterized in that: In step (1), the cerium salt is at least one of cerous nitrate, cerous sulfate and cerous sulfate.

5. The method for preparing ultra-small particle size cerium oxide nanoparticles according to claim 4, characterized in that: In step (1), the molar ratio of magnesium sulfate to cerous nitrate is ≥2, the molar ratio of magnesium sulfate to cerous sulfate is ≥10, and the molar ratio of magnesium sulfate to ceric sulfate is ≥5.

6. The method for preparing ultra-small particle size cerium oxide nanoparticles according to claim 1, characterized in that: In step (2), the organic solvent is one or a mixture of ethanol, methanol, propanol, isopropanol, tert-butanol, diethylene glycol, pyridine, dioxane, tetrahydrofuran, acetone, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol propyl ether, ethylene glycol butyl ether, diethylene glycol butyl ether, dimethyl sulfoxide or dimethylformamide.

7. The method for preparing ultra-small particle size cerium oxide nanoparticles according to claim 1, characterized in that: In step (3), the calcination temperature is 300-700°C.

8. The method for preparing ultra-small particle size cerium oxide nanoparticles according to claim 7, characterized in that: In step (3), the calcination time is not less than 1 hour.

9. The method for preparing ultra-small particle size cerium oxide nanoparticles according to claim 7, characterized in that: In step (4), magnesium sulfate in the mixture is removed by washing with water.

10. Cerium oxide nanoparticles obtained by the preparation method according to claim 1.

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