Synthesis method of nano cerium oxide

Abstract

The invention discloses a nano cerium oxide synthesis method which comprises the following steps: preparing a reaction solution; performing ultrasonic reaction; carrying out aging treatment; centrifugally washing; drying and calcining; the cerium salt solution is prepared from soluble cerium salt, and the concentration of the cerium salt solution is 0.01 mol / L to 1 mol / L; the precipitant solution is one or more of ammonia water, a sodium hydroxide solution, a sodium carbonate solution and a sodium bicarbonate solution, and the concentration of the precipitant solution is 0.2 mol / L-8 mol / L; the ultrasonic power of the ultrasonic microreactor is 10W to 1000W; the calcining temperature ranges from 400 DEG C to 1000 DEG C. The nano cerium oxide with less agglomeration, controllable particle size, uniform size and adjustable morphology is obtained on the basis of super-strong mixing and crystallization promoting capabilities of the ultrasonic microreactor. Meanwhile, the method is simple and convenient to operate, easy to amplify and convenient for industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of nano rare earth materials, and particularly relates to a method for synthesizing nano cerium oxide. Background Art

[0002] Among rare earth elements, cerium (Ce) is the most abundant element. The abundance of cerium in the earth's crust (66.5 ppm) is slightly higher than that of copper (60 ppm). Cerium oxide (CeO 2 ) is the most stable and common oxide of cerium element. CeO 2 has various morphologies such as spherical, rod-shaped, cubic, flower-shaped, etc. Due to the variable valence characteristics of Ce, CeO 2 can store oxygen through Ce 2 O 3 + 1 / 2O 2 → CeO 2 when there is sufficient oxygen, and release oxygen through CeO 2 → Ce 2 O 3 + 1 / 2O 2 when there is insufficient oxygen. In addition, CeO 2 is also the oxide catalyst with the highest catalytic activity among rare earth oxides. Nano-scale CeO 2 has more excellent properties than non-nano cerium oxide and is widely used in fields such as automotive exhaust treatment and hydrogen synthesis. CeO 2 has advantages such as appropriate hardness, high polishing efficiency, and long service life, and is one of the most common polishing powders. Particle size is one of the key factors affecting the polishing effect. The usage of high-purity and ultrafine CeO 2 is gradually increasing with the development of various ultra-precision optical (electronic) instruments.

[0003] Currently, the main methods for preparing nano cerium oxide are: precipitation method and hydrothermal method. The precipitation method uses different precipitants (such as ammonia water, sodium hydroxide, etc.) to treat cerium salts to obtain precursors, and nano cerium oxide is obtained through steps such as aging, centrifugal drying, and calcination. This method is simple to operate and has low cost, and is the mainstream industrial production process. However, the nano cerium oxide powder prepared by this method has serious agglomeration and it is difficult to control the particle size of the product. The particle sizes are non-uniform and cannot meet the actual use requirements; the hydrothermal method is to place cerium salts and other reactants in a high-pressure reaction kettle and heat them to form a hydrothermal environment of high temperature and high pressure to obtain nano cerium oxide with high purity and good dispersibility. However, this method has poor safety, is difficult to scale up, and is difficult to apply in industry, and is limited to laboratory research.

[0004] In summary, the present invention has developed a continuous synthesis process for nano-sized cerium oxide with controllable particle size. Based on the ultra-strong mixing and crystallization-promoting ability of the ultrasonic microreactor, nano-sized cerium oxide with less agglomeration, controllable particle size, uniform size, and adjustable morphology is obtained. At the same time, this method is easy to operate, easy to scale up, and convenient for industrial production. Summary of the Invention

[0005] The object of the present invention is to provide a method for synthesizing nano-sized cerium oxide to solve the above technical problems. Based on the ultra-strong mixing and crystallization-promoting ability of the ultrasonic microreactor, nano-sized cerium oxide with less agglomeration, controllable particle size, uniform size, and adjustable morphology is obtained. At the same time, this method is easy to operate, easy to scale up, and convenient for industrial production.

[0006] To achieve the above invention object, the technical solution adopted by the present invention is as follows:

[0007] A method for synthesizing nano-sized cerium oxide, comprising the following steps,

[0008] Preparation of reaction solution: Prepare a cerium salt solution and a precipitant solution;

[0009] Ultrasonic reaction: Inject the prepared cerium salt solution and precipitant solution into the ultrasonic microreactor respectively, and react in the ultrasonic microreactor to obtain a precursor;

[0010] Aging treatment: Transfer and heat the precursor, and introduce air during heating to obtain a product;

[0011] Centrifugal washing: Wash the product;

[0012] Drying and calcination: Calcinate the washed product;

[0013] The cerium salt solution is made of a soluble cerium salt, and the concentration of the cerium salt solution is 0.01 mol / L - 1 mol / L;

[0014] The precipitant solution is a solution containing one or more of oxalate, hydroxide, carbonate, and bicarbonate, and the concentration of the precipitant solution is 0.2 mol / L - 8 mol / L;

[0015] The ultrasonic power of the ultrasonic microreactor is 10 W - 1000 W; the calcination temperature is 400 °C - 1000 °C.

[0016] Preferably, the cerium salt solution is made by mixing cerium nitrate hexahydrate and water, and the concentration of the cerium salt solution is 0.033 mol / L - 0.33 mol / L.

[0017] Preferably, a surfactant is added to the precipitant solution, and the surfactant includes one or more of polyvinylpyrrolidone, sodium dodecyl sulfate, ethanol, and polyvinyl alcohol.

[0018] Preferably, the surfactant is polyvinylpyrrolidone, and the concentration of the surfactant in the precipitant solution is 0 mg / mL - 30 mg / mL, wherein the concentration of the surfactant in the precipitant solution is not 0 mg / mL.

[0019] Preferably, the concentration of the surfactant in the precipitant solution is 5 mg / mL - 10 mg / mL.

[0020] Preferably, when the precipitant solution is 0.1 mol / L ammonia water, polyvinylpyrrolidone is added to the precipitant solution, and the concentration of the polyvinylpyrrolidone in the precipitant solution is 10 mg / ml. The cerium salt solution is a 0.033 mol / L cerium nitrate hexahydrate solution.

[0021] At room temperature, the precipitant solution and the cerium salt solution are respectively injected into an ultrasonic microreactor; the frequency of the ultrasonic microreactor is 20 kHz and the power is 30 W; the injection flow rates of the precipitant solution and the cerium salt solution are controlled to be the same, and the injection flow rates are both 6 ml / min - 200 ml / min, and the residence time is 0 min - 1 min to obtain a precursor.

[0022] The obtained precursor is heated at 120°C for 2 hours, and air is introduced during this period, where the flow rate of the introduced air is 100 cm 3 / min. After solid-liquid separation, a product is obtained.

[0023] The obtained product is washed three times with water and once with ethanol.

[0024] The washed product is dried at 60°C and then calcined at a temperature of 400°C for 2 hours to obtain a spherical cerium oxide product.

[0025] Preferably, the precipitant solution is replaced with a 0.5 mol / L sodium carbonate precipitant solution to obtain an olive-shaped cerium oxide product.

[0026] Preferably, the ultrasonic power of the ultrasonic microreactor is 30 W - 50 W.

[0027] Preferably, the calcination temperature is 400°C - 600°C.

[0028] Preferably, the cerium salt solution is a cerium nitrate hexahydrate - ethylene glycol solution or a cerium nitrate hexahydrate aqueous solution, and the precipitant solution is a sodium hydroxide aqueous solution or a sodium hydroxide - ethylene glycol solution.

[0029] This application has achieved beneficial technical effects:

[0030] Based on the strong mixing and crystallization - promoting ability of the ultrasonic micro - reactor of the present invention, nano - cerium oxide with less agglomeration, controllable particle size, uniform size, and adjustable morphology is obtained. At the same time, this method is easy to operate, easy to scale up, and convenient for industrial production;

[0031] Based on the precipitation method, the present invention utilizes the strong mixing performance of the ultrasonic micro - reactor to develop a synthesis method for nano - cerium oxide with uniform particle size and different morphologies. By using the dispersion effect of ultrasound, the agglomeration of nano - particles can be reduced, and at the same time, blockage caused by precipitation can be prevented;

[0032] The strong mixing performance of the synergistic effect of ultrasound and the micro - reactor can mix the precipitant solution and the salt solution more evenly during the reaction, making the particle size uniform. At the same time, the cavitation bubbles generated by ultrasonic cavitation can generate more crystal nuclei, making the particle size smaller. As the ultrasonic power increases, the cavitation effect increases, and the particles of nano - cerium oxide gradually become smaller. In summary, using the ultrasonic micro - reactor can reduce agglomeration, prepare nano - cerium oxide with uniform particle size and different morphologies, and this method is easy to scale up and can be continuously produced. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The process flow chart of the present invention is shown;

[0034] Figure 2 The transmission electron microscope image of Example 1 is shown;

[0035] Figure 3 The transmission electron microscope image of Example 2 is shown;

[0036] Figure 4 The transmission electron microscope image of Example 3 is shown;

[0037] Figure 5 The XRD results of Examples 1 - 3 are shown;

[0038] Figure 6 The transmission electron microscope image of Example 4 is shown;

[0039] Figure 7 The transmission electron microscope image of Example 5 is shown;

[0040] Figure 8 The transmission electron microscope image of Example 6 is shown;

[0041] Figure 9 The transmission electron microscope image of Example 8 is shown;

[0042] Figure 10 The transmission electron microscope image of Example 7 is shown;

[0043] Figure 11 Shown is the scanning electron microscope image of Example 7;

[0044] Figure 12 Shown is the transmission electron microscope image of Comparative Example 1. Detailed implementation manners

[0045] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with its embodiments. It should be understood that the specific implementation manners described herein are only used to explain the present invention and do not limit the protection scope of the present invention.

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the description of the present invention herein are only for the purpose of describing specific implementation manners and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0047] A method for synthesizing nano-ceria in an embodiment of the present invention includes the following steps.

[0048] Preparation of reaction solution: Prepare a cerium salt solution and a precipitant solution;

[0049] Ultrasonic reaction: Inject the prepared cerium salt solution and precipitant solution into an ultrasonic microreactor respectively, and react in the ultrasonic microreactor to obtain a precursor;

[0050] Aging treatment: Transfer and heat the precursor, and introduce air during heating to obtain a product;

[0051] Centrifugal washing: Wash the product;

[0052] Drying and calcination: Calcinate the washed product;

[0053] The cerium salt solution is made of a soluble cerium salt, and the concentration of the cerium salt solution is 0.01 mol / L - 1 mol / L;

[0054] The precipitant solution is a solution containing one or more of oxalate, hydroxide, carbonate, and bicarbonate, and the concentration of the precipitant solution is 0.2 mol / L - 8 mol / L;

[0055] The ultrasonic power of the ultrasonic microreactor is 10 W - 1000 W; the calcination temperature is 400 °C - 1000 °C;

[0056] Select to adjust the power of the ultrasonic microreactor or the calcination temperature to adjust the particle size of the product; React using an ultrasonic microreactor with a frequency of 20 kHz and a power of 30 W to obtain spherical cerium oxide with an average particle size of 6.87 nm; React using an ultrasonic microreactor with a frequency of 20 kHz and a power of 10 W to obtain spherical cerium oxide with an average particle size of 7.87 nm; React using an ultrasonic microreactor with a frequency of 20 kHz and a power of 50 W to obtain spherical cerium oxide with an average particle size of 4.42 nm. The super mixing performance of the synergistic effect of ultrasound and the microreactor can mix the precipitant solution and the salt solution more evenly during the reaction, making the particle size uniform. The action of the cavitation bubbles generated by ultrasonic cavitation can generate more crystal nuclei, making the particle size smaller. As the ultrasonic power increases, the cavitation effect increases, and the particles of nano-cerium oxide gradually become smaller.

[0057] Or, select to adjust the type of precipitant solution or the solvent of the precipitant solution and the cerium salt solution to adjust the morphology of the product.

[0058] The pH values of different precipitants are different, and the mass transfer rates in the ultrasonic microreactor are different, making the growth rates of the particles in different crystal orientations different; Different solvents surrounding the particles will also change the growth rates in different crystal orientations. Random growth results in spherical nanoparticles, and directional growth results in needle-like or olive-shaped nano-cerium oxide.

[0059] In one of the embodiments, during the aging treatment process, the precursor is transferred to an oil bath for heating, and air is introduced during the oil bath to obtain the product.

[0060] In one of the embodiments, the precipitant solution is one or a mixture of ammonia water, sodium hydroxide solution, sodium carbonate solution, and sodium bicarbonate solution.

[0061] In one of the embodiments, the concentration of the precipitant is 0.05 mol / L - 0.3 mol / L.

[0062] In one of the embodiments, in the ultrasonic reaction, the injection flow rate of the cerium salt solution is the same as that of the precipitant solution, and the injection flow rate is 6.8 ml / min.

[0063] In one of the embodiments, the cerium salt solution is specifically cerium nitrate hexahydrate solution; the cerium salt solution is made of a soluble cerium salt, and the concentration is 0.01 mol / L - 1 mol / L.

[0064] In one of the embodiments, the cerium salt solution is made by mixing cerium nitrate hexahydrate and water, and the concentration of the cerium salt solution is 0.033 mol / L - 0.33 mol / L.

[0065] In one embodiment, a surfactant is added to the precipitant solution, and the surfactant includes one or more of polyvinylpyrrolidone, sodium dodecyl sulfate, ethanol, and polyvinyl alcohol.

[0066] In one embodiment, the surfactant is polyvinylpyrrolidone, and the concentration of the surfactant in the precipitant solution is 0 mg / mL - 30 mg / mL, wherein the concentration of the surfactant in the precipitant solution is not 0 mg / mL.

[0067] In one embodiment, the surfactant is polyvinylpyrrolidone, and the concentration of the surfactant in the precipitant solution is 5 mg / mL - 10 mg / mL.

[0068] In one embodiment, when the precipitant solution is 0.1 mol / L ammonia water, polyvinylpyrrolidone is added to the precipitant solution, and the concentration of the polyvinylpyrrolidone in the precipitant solution is 10 mg / ml. The cerium salt solution is a 0.033 mol / L cerium nitrate hexahydrate solution.

[0069] Under room temperature conditions, the precipitant solution and the cerium salt solution are respectively injected into an ultrasonic microreactor; the frequency of the ultrasonic microreactor is 20 kHz, and the power is 30 W; the injection flow rates of the precipitant solution and the cerium salt solution are controlled to be the same, and the injection flow rates are both 6.8 ml / min, and the residence time is 1 min to obtain a precursor.

[0070] The obtained precursor is heated at 120 °C for 2 hours, and air is introduced during this period, wherein the flow rate of the introduced air is 100 cm 3 / min. After solid-liquid separation, a product is obtained.

[0071] The obtained product is washed three times with water and once with ethanol.

[0072] The washed product is dried at 60 °C and then calcined at 400 °C for 2 hours to obtain a spherical cerium oxide product.

[0073] In one embodiment, the precipitant solution is replaced with a 0.5 mol / L sodium carbonate precipitant solution to obtain an olive-shaped cerium oxide product.

[0074] In one embodiment, the ultrasonic power of the ultrasonic microreactor is 30 W - 50 W.

[0075] In one embodiment, the power of the ultrasonic microreactor is one of 10W, 20W, and 50W. Different particle sizes of the product can be adjusted according to different powers. The selectable particle size range is large, which is convenient to adjust the power of the ultrasonic microreactor according to the demand to achieve the adjustment of different particle sizes of cerium oxide products. It can be seen that with the increase of the power of the ultrasonic microreactor, the particle size of the obtained nano-cerium oxide product gradually decreases.

[0076] In one embodiment, the calcination temperature is 400°C - 600°C.

[0077] In one embodiment, when the calcination temperature is 400°C, spherical cerium oxide products with an average particle size of 6.87 nm are obtained; when the calcination temperature is 600°C, spherical cerium oxide products with an average particle size of 12.4 nm are obtained; when the calcination temperature is 800°C, spherical cerium oxide products with an average particle size of 27.12 nm are obtained.

[0078] In one embodiment, the cerium salt solution is cerium nitrate hexahydrate-ethylene glycol solution or cerium nitrate hexahydrate aqueous solution, and the precipitant solution is sodium hydroxide aqueous solution or sodium hydroxide-ethylene glycol solution.

[0079] In one embodiment, the cerium salt solution is cerium nitrate hexahydrate-ethylene glycol solution, and the precipitant solution is sodium hydroxide-ethylene glycol solution. Rod-shaped nano-cerium oxide is obtained after ultrasonic reaction, aging treatment, centrifugal washing, and drying and calcination.

[0080] In one embodiment, the cerium nitrate hexahydrate aqueous solution; the precipitant solution is sodium hydroxide aqueous solution. Spherical nano-cerium oxide is obtained after ultrasonic reaction, aging treatment, centrifugal washing, and drying and calcination.

[0081] In one embodiment, the residence time is 3s - 300s.

[0082] In one embodiment, the residence time is 30s - 60s.

[0083] In one embodiment, the residence time is 0 min - 1 min.

[0084] In one embodiment, the heating temperature is 80°C - 180°C.

[0085] In one embodiment, the heating temperature is 100°C - 120°C.

[0086] In one embodiment, the heating duration is 2h - 12h.

[0087] In one embodiment, the heating duration is 2h - 5h.

[0088] In one embodiment, the cerium nitrate hexahydrate solution is a mixed solution formed by cerium nitrate hexahydrate and water;

[0089] In one embodiment, the calcination time is 2 h.

[0090] In one embodiment, the injection flow rate of the precipitant solution and the injection flow rate of the cerium salt solution are the same, and the average injection flow rate is 6 ml / min - 200 ml / min.

[0091] In one embodiment, the injection flow rate of the precipitant solution and the injection flow rate of the cerium salt solution are the same, and the average injection flow rate is 6 ml / min - 13.6 ml / min.

[0092] Based on the ultra-strong mixing and crystallization-promoting ability of the ultrasonic microreactor of the present invention, nano-ceria with less agglomeration, controllable particle size, uniform size, and adjustable morphology is obtained. At the same time, this method is easy to operate, easy to scale up, and convenient for industrial production;

[0093] Based on the precipitation method, the present invention utilizes the ultra-strong mixing performance of the ultrasonic microreactor to develop a synthesis method for nano-ceria with uniform particle size and different morphologies. By using the dispersion effect of ultrasound, the agglomeration of nanoparticles can be reduced, and at the same time, blockage caused by precipitation can be prevented;

[0094] The ultra-strong mixing performance of the synergistic effect of ultrasound and the microreactor can mix the precipitant solution and the salt solution more evenly during the reaction, making the particle size uniform. At the same time, the cavitation bubbles generated by ultrasonic cavitation can generate more crystal nuclei, making the particle size smaller. As the ultrasonic power increases, the cavitation effect increases, and the particles of nano-ceria gradually become smaller. In summary, the ultrasonic microreactor can reduce agglomeration and prepare nano-ceria with uniform particle size and different morphologies, and this method is easy to scale up and can be continuously produced.

[0095] The technical solution of the present invention will be introduced in detail below with specific examples.

[0096] Example 1

[0097] 1. Preparation of reaction solution: Prepare a 0.033 mol / L cerium nitrate hexahydrate solution as the cerium salt solution; prepare a precipitant solution containing 0.1 mol / L ammonia water, and add polyvinylpyrrolidone to the precipitant solution, and the concentration of the polyvinylpyrrolidone in the precipitant solution is 10 mg / ml.

[0098] 2. Ultrasonic reaction: At room temperature, inject the precipitant solution and the cerium salt solution into the ultrasonic microreactor (20 kHz, 30 W) respectively, control the same flow rate so that the residence time is 1 min, and the injection flow rate is 6.8 ml / min.

[0099] 3. Aging treatment: Put the product obtained in 2 into a constant-temperature oil bath and heat it at 120 °C for 2 hours, while continuously introducing air (100 cm 3 / min).

[0100] 4. Centrifugal washing: Wash the product obtained in 3 three times with water and once with ethanol.

[0101] 5. Drying and calcination: Put the product obtained in 4 into an oven and dry it at 60 °C, then put it into a muffle furnace and calcine it at 400 °C for 2 hours. Grind the product with a mortar to obtain spherical cerium oxide with an average particle size of 6.87 nm.

[0102] Example 2

[0103] 1. Preparation of reaction solution: Prepare a 0.033 mol / L cerium nitrate hexahydrate solution as the cerium salt solution; prepare a precipitant solution containing 0.1 mol / L ammonia water, and add polyvinylpyrrolidone to the precipitant solution. The concentration of polyvinylpyrrolidone in the precipitant solution is 10 mg / ml.

[0104] 2. Ultrasonic reaction: At room temperature, inject the precipitant solution and the cerium salt solution into an ultrasonic microreactor (20 kHz, 10 W) respectively, control the same flow rate so that the residence time is 1 min, and the injection flow rate is 6.8 ml / min.

[0105] 3. Aging treatment: Put the product obtained in 2 into a constant-temperature oil bath and heat it at 120 °C for 2 hours, while continuously introducing air (100 cm 3 / min).

[0106] 4. Centrifugal washing: Wash the product obtained in 3 three times with water and once with ethanol.

[0107] 5. Drying and calcination: Put the product obtained in 4 into an oven and dry it at 60 °C, then put it into a muffle furnace and calcine it at 400 °C for 2 hours. Grind the product with a mortar to obtain spherical cerium oxide with an average particle size of 7.87 nm.

[0108] Example 3

[0109] 1. Preparation of reaction solution: Prepare a 0.033 mol / L cerium nitrate hexahydrate solution as the cerium salt solution; prepare a precipitant solution containing 0.1 mol / L ammonia water, and add polyvinylpyrrolidone to the precipitant solution. The concentration of polyvinylpyrrolidone in the precipitant solution is 10 mg / ml.

[0110] 2. Ultrasonic reaction: At room temperature, the precipitant solution and the cerium salt solution were respectively injected into an ultrasonic microreactor (20 kHz, 50 W). The flow rates were controlled to be the same so that the residence time was 1 min, and the injection flow rate was 6.8 ml / min.

[0111] 3. Aging treatment: The product obtained in 2 was placed in a constant-temperature oil bath and heated at 120 °C for 2 hours, during which air was continuously introduced (100 cm 3 / min).

[0112] 4. Centrifugal washing: The product obtained in 3 was washed three times with water and once with ethanol.

[0113] 5. Drying and calcination: The product obtained in 4 was dried in an oven at 60 °C and then calcined in a muffle furnace at 400 °C for 2 hours. The product was ground with a mortar to obtain spherical cerium oxide with an average particle size of 4.42 nm.

[0114] As Figure 5 shown by the XRD results, the diffraction characteristic peaks presented in the X-ray powder diffraction pattern of the sample prepared by this method are consistent with the corresponding characteristic spectrum of CeO 2 , indicating that the sample prepared by this method is a pure-phase cubic fluorite structure CeO2 with good crystallization and complete crystal form. Moreover, the larger the particle size, the narrower the diffraction peak, and the smaller the particle size, the wider the diffraction peak, and the two match well.

[0115] Comparing Example 1, Example 2, and Example 3, nano-ceria with different particle sizes was obtained by adjusting the ultrasonic power.

[0116] In Example 1, an ultrasonic microreactor with a frequency of 20 kHz and a power of 30 W was used for the reaction to obtain spherical cerium oxide with an average particle size of 6.87 nm; in Example 2, an ultrasonic microreactor with a frequency of 20 kHz and a power of 10 W was used for the reaction to obtain spherical cerium oxide with an average particle size of 7.87 nm; in Example 3, an ultrasonic microreactor with a frequency of 20 kHz and a power of 50 W was used for the reaction to obtain spherical cerium oxide with an average particle size of 4.42 nm. It can be seen that in this technical solution, as the power of the ultrasonic microreactor increases, the average particle size of the obtained cerium oxide becomes smaller, and its size is uniform. That is, the power of the ultrasonic microreactor can be adjusted according to the need of the average particle size of cerium oxide to match the corresponding average particle size of cerium oxide; the particle size of this technical solution is controllable, the control method is simple, easy to implement, the degree of particle size controllability is high, and it is easy to scale up and convenient for industrial production.

[0117] Example 4

[0118] 1. Reaction solution preparation: Prepare a 0.033 mol / L cerium nitrate hexahydrate solution as the cerium salt solution; prepare a precipitant solution containing 0.1 mol / L ammonia water, and add polyvinylpyrrolidone to the precipitant solution, with the concentration of polyvinylpyrrolidone in the precipitant solution being 10 mg / ml.

[0119] 2. Ultrasonic reaction: At room temperature, inject the cerium salt solution and the precipitant solution into an ultrasonic microreactor (20 kHz, 30 W) respectively, control the same flow rate so that the residence time is 1 min, and the injection flow rate is 6.8 ml / min.

[0120] 3. Aging treatment: Put the product obtained in 2 into a constant temperature oil bath and heat it at 120 °C for 2 hours, and continuously introduce air (100 cm 3 / min) during this period.

[0121] 4. Centrifugal washing: Wash the product obtained in 3 three times with water and once with ethanol.

[0122] 5. Drying and calcination: Put the product obtained in 4 into an oven and dry it at 60 °C, then put it into a muffle furnace and calcine it at 600 °C for 2 hours, and grind the product with a mortar to obtain spherical cerium oxide with an average particle size of 12.4 nm.

[0123] Example 5

[0124] 1. Reaction solution preparation: Prepare a 0.033 mol / L cerium nitrate hexahydrate solution as the cerium salt solution; prepare a precipitant solution containing 0.1 mol / L ammonia water, and add polyvinylpyrrolidone to the precipitant solution, with the concentration of polyvinylpyrrolidone in the precipitant solution being 10 mg / ml.

[0125] 2. Ultrasonic reaction: At room temperature, inject the cerium salt solution and the precipitant solution into an ultrasonic microreactor (20 kHz, 30 W) respectively, control the same flow rate so that the residence time is 1 min, and the injection flow rate is 6.8 ml / min.

[0126] 3. Aging treatment: Put the product obtained in 2 into a constant temperature oil bath and heat it at 120 °C for 2 hours, and continuously introduce air (100 cm 3 / min) during this period.

[0127] 4. Centrifugal washing: Wash the product obtained in 3 three times with water and once with ethanol.

[0128] 5. Drying and calcination: Put the product obtained in 4 into an oven and dry it at 60 °C, then put it into a muffle furnace and calcine it at 800 °C for 2 hours, and grind the product with a mortar to obtain spherical cerium oxide with an average particle size of 27.12 nm.

[0129] Comparing Comparative Example 1, Example 4 and Example 5, changing the calcination temperature can adjust the particle size of the cerium oxide product.

[0130] In Example 1, the calcination temperature was 400 °C, and spherical cerium oxide with an average particle size of 6.87 nm was obtained; in Example 4, the calcination temperature was 600 °C, and spherical cerium oxide with an average particle size of 12.4 nm was obtained; in Example 5, the calcination temperature was 800 °C, and spherical cerium oxide with an average particle size of 27.12 nm was obtained. It can be seen that as the calcination temperature increases, the average particle size of the obtained cerium oxide becomes larger, and its size is uniform. That is, the calcination temperature can be adjusted according to the required average particle size of cerium oxide to match the corresponding average particle size of cerium oxide. The particle size of this technical solution is controllable, the control method is simple, easy to implement, the degree of particle size controllability is high, and it is easy to scale up, facilitating industrial production.

[0131] Example 6

[0132] 1. Preparation of reaction solution: Prepare a 0.033 mol / L cerium nitrate hexahydrate solution as the cerium salt solution; prepare a precipitant solution containing 0.5 mol / L sodium carbonate, and add polyvinylpyrrolidone to the cerium salt solution. The concentration of polyvinylpyrrolidone in the precipitant solution is 10 mg / ml.

[0133] 2. Ultrasonic reaction: At room temperature, inject the cerium salt solution and the precipitant solution into an ultrasonic microreactor (20 kHz, 30 W) respectively, control the same flow rate so that the residence time is 1 min, and the injection flow rate is 6.8 ml / min.

[0134] 3. Aging treatment: Put the product obtained in step 2 into a constant temperature oil bath at 120 °C and heat for 2 hours, and continuously introduce air (100 cm 3 / min) during this period.

[0135] 4. Centrifugal washing: Wash the product obtained in step 3 three times with water and once with ethanol.

[0136] 5. Drying and calcination: Put the product obtained in step 4 into an oven and dry at 60 °C, then put it into a muffle furnace and calcine at 400 °C for 2 hours. Grind the product with a mortar to obtain olive-shaped cerium oxide with an average particle size of 5.3 μm.

[0137] Comparing Comparative Example 1 and Example 6, changing the type of precipitant can obtain nano-cerium oxide with different morphologies. In Example 1, the precipitant solution used was ammonia water, and spherical cerium oxide with an average particle size of 6.87 nm was obtained; in Example 6, the precipitant solution used was sodium carbonate solution, and olive-shaped cerium oxide with an average particle size of 5.3 μm was obtained. It can be seen that the final morphology of the synthesized cerium oxide can be adjusted by changing the type of precipitant. This adjustment method is simple, easy to control, easy to scale up, and facilitating industrial production.

[0138] In Example 1, hydroxide ions in the precipitant solution and cerous ions in the cerium salt solution form cerous hydroxide in the ultrasonic microreactor. In Example 6, carbonate ions in the precipitant and cerous ions in the cerium salt form cerium carbonate in the ultrasonic microreactor. Due to the different pH values of the two precipitant solutions, the mass transfer rates in the ultrasonic microreactor are different, and the growth rates of particles on each crystal phase change. In Example 1, the particles tend to grow randomly, forming spherical-like particles; in Example 2, the particles tend to grow directionally, forming olive-shaped particles.

[0139] Example 7

[0140] 1. Preparation of reaction solution: Prepare a 0.033 mol / L cerium nitrate hexahydrate-ethylene glycol solution as the cerium salt solution; prepare a 0.3 mol / L sodium hydroxide-ethylene glycol solution as the precipitant solution.

[0141] 2. Ultrasonic reaction: At room temperature, inject the cerium salt solution and the precipitant solution into the ultrasonic microreactor (20 kHz, 50 W) respectively, control the same flow rate so that the residence time is 30 s, and the injection flow rate is 13.6 ml / min.

[0142] 3. Aging treatment: Put the product obtained in 2 into a constant temperature oil bath at 100 °C and heat for 5 hours, and continuously introduce air (100 cm 3 / min) during this period.

[0143] 4. Centrifugal washing: Wash the product obtained in 3 three times with water and once with ethanol.

[0144] 5. Drying and calcination: Put the product obtained in 4 into an oven and dry at 60 °C, then put it into a muffle furnace and calcine at 400 °C for 2 hours, and grind the product with a mortar to obtain rod-shaped nano-ceria with a length of about 13.4 μm.

[0145] Example 8

[0146] 1. Preparation of reaction solution: Prepare a 0.033 mol / L cerium nitrate hexahydrate as the cerium salt solution; prepare a 0.3 mol / L sodium hydroxide as the precipitant solution, which is an aqueous sodium hydroxide solution.

[0147] 2. Ultrasonic reaction: At room temperature, inject the cerium salt solution and the precipitant solution into the ultrasonic microreactor (20 kHz, 50 W) respectively, control the same flow rate so that the residence time is 30 s, and the injection flow rate is 13.6 ml / min.

[0148] 3. Aging treatment: Put the product obtained in 2 into a constant temperature oil bath at 100 °C and heat for 5 hours, and continuously introduce air (100 cm 3 / min) during this period.

[0149] 4. Centrifugal washing: Wash the product obtained in step 3 three times with water and once with ethanol.

[0150] 5. Drying and calcination: Put the product obtained in step 4 into an oven and dry it at 60 °C, then put it into a muffle furnace and calcine it at 400 °C for 2 hours. Grind the product with a mortar to obtain spherical cerium oxide with an average particle size of 8.95 nm.

[0151] Comparing Comparative Example 7 with Example 8, the solvents of the precipitant solution and the cerium salt solution can be changed to obtain products with different morphologies.

[0152] In Example 7, cerium nitrate hexahydrate-ethylene glycol solution is used as the cerium salt solution, and sodium hydroxide-ethylene glycol solution is used as the precipitant solution to obtain rod-shaped nano-cerium oxide with a length of about 13.4 μm; in Example 8, cerium nitrate hexahydrate is used as the cerium salt solution and sodium hydroxide is used as the precipitant solution to obtain spherical cerium oxide with an average particle size of 8.95 nm.

[0153] It can be seen that in this technical solution, different morphologies of products can be obtained by adjusting the solvents of the precipitant solution and the cerium salt solution. This adjustment method is simple, easy to implement, easy to scale up, and convenient for industrial production.

[0154] In Comparative Example 7, the reaction solvent is ethylene glycol solution. The ethylene glycol solution can coat the surface of the nanoparticles, limit their random growth, and grow directionally to obtain rod-shaped nano-cerium oxide. In aqueous solution, it tends to grow randomly to obtain spherical nano-cerium oxide.

[0155] Comparative Example 1

[0156] The difference between this Comparative Example 1 and Example 1 lies in step 2. Instead of introducing the precipitant solution and the cerium salt solution into the ultrasonic microreactor, the precipitant solution is directly dropped into the cerium salt solution, and the other steps remain unchanged. Cerium oxide with serious agglomeration, uneven particle size, and irregular shape is obtained.

[0157] It can be seen that in this technical solution, by reacting and synthesizing nano-cerium oxide based on an ultrasonic microreactor, the number of agglomerates can be effectively reduced, and the obtained product has a uniform size, solving the technical problems of serious agglomeration of nano-cerium oxide powder prepared by the precipitation method in the prior art and difficulty in controlling the particle size of the product, and uneven particle size.

[0158] In this technical solution, based on the strong mixing and crystallization-promoting ability of the ultrasonic microreactor, nano-cerium oxide with less agglomeration, controllable particle size, uniform size, and adjustable morphology is obtained. At the same time, this method is easy to operate, easy to scale up, and convenient for industrial production.

[0159] Based on the precipitation method and utilizing the super mixing performance of an ultrasonic microreactor, the present invention has developed a synthesis method for nano-ceria with uniform particle size and different morphologies. By using the dispersion effect of ultrasound, the agglomeration of nanoparticles can be reduced, and at the same time, blockage caused by precipitation can be prevented. For example, in Example 1, the edges of the ceria particles are clearly visible, and there is almost no situation where multiple particles are agglomerated into a whole; in Comparative Example 1, the ceria particles obtained without using the ultrasonic microreactor are agglomerated into larger particles, and the small particles forming the agglomerates are hardly distinguishable. The super mixing performance of the synergistic effect of ultrasound and the microreactor can mix the precipitant solution and the salt solution more uniformly during the reaction, making the particle size uniform. For example, the particle size distribution in Example 1 is between 4 - 8 nm, while the agglomerated particles in the comparative example are between 10 - 100 nm, and the particle size of the non-agglomerated particles cannot be accurately counted. The action of the cavitation bubbles generated by ultrasonic cavitation can generate more crystal nuclei, making the particle size smaller. For example, in Example 1, Example 2, and Example 3, as the ultrasonic power increases, the cavitation effect increases, and the particles of nano-ceria gradually become smaller. In summary, the use of an ultrasonic microreactor can reduce agglomeration, prepare nano-ceria with uniform particle size and different morphologies, and this method is easy to scale up and can be continuously produced.

[0160] In this technical solution, the following advantages are possessed:

[0161] 1. It can quickly achieve precise control of the particle size and morphology of ceria products, and synthesize ceria products with uniform particle size and controllable morphology. By adjusting parameters such as the ceria concentration, precipitant concentration, dosage of the active agent, power of the ultrasonic microreactor, and reaction residence time, the particle size and morphology can be regulated.

[0162] 2. The process flow of this invention is simple, the operation is easy, the equipment investment is small, and the production cost is low. At the same time, this process is easy to scale up and can quickly achieve large-scale production.

[0163] The technical features of the above-mentioned embodiments can be combined arbitrarily. For the sake of concise description, 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, it should be considered as the scope recorded in this specification.

[0164] The above-mentioned embodiments only represent several implementation manners of the present invention. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the invention patent should be subject to the appended claims.

[0165] The above has elaborated in detail on the embodiments of a process for synthesizing nano-ceria based on an ultrasonic microreactor provided by the present invention. Specific examples are used herein to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the core idea of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for synthesizing nano cerium oxide, characterized in that, it comprises the following steps, Reaction solution preparation: Prepare a cerium salt solution and a precipitant solution; Ultrasonic reaction: Inject the prepared cerium salt solution and precipitant solution into an ultrasonic microreactor respectively, and react in the ultrasonic microreactor to obtain a precursor; Aging treatment: Transfer and heat the precursor, and introduce air during heating to obtain a product; Centrifugal washing: Wash the product; Drying and calcination: Perform calcination treatment on the washed product; The cerium salt solution is made of a soluble cerium salt, and the concentration of the cerium salt solution is 0.01 mol / L - 1 mol / L; The precipitant solution is a solution containing one or more of oxalate, hydroxide, carbonate, and bicarbonate, and the concentration of the precipitant solution is 0.2 mol / L - 8 mol / L; The ultrasonic power of the ultrasonic microreactor is 10 W - 1000 W; the calcination temperature is 400 °C - 1000 °C.

2. The method for synthesizing nano cerium oxide according to claim 1, characterized in that, The cerium salt solution is made by mixing cerium nitrate hexahydrate with water, and the concentration of the cerium salt solution is 0.033 mol / L - 0.33 mol / L.

3. The method for synthesizing nano cerium oxide according to claim 2, characterized in that, Add a surfactant to the precipitant solution, and the surfactant includes one or more of polyvinylpyrrolidone, sodium dodecyl sulfate, ethanol, and polyvinyl alcohol.

4. The method for synthesizing nano cerium oxide according to claim 3, characterized in that, The surfactant is polyvinylpyrrolidone, and the concentration of the surfactant in the precipitant solution is 0 mg / mL - 30 mg / mL, wherein the concentration of the surfactant in the precipitant solution is not 0 mg / mL.

5. The method for synthesizing nano cerium oxide according to claim 4, characterized in that, The concentration of the surfactant in the precipitant solution is 5 mg / mL - 10 mg / mL.

6. The method for synthesizing nano cerium oxide according to any one of claims 3 to 5, characterized in that, When the precipitant solution is 0.1 mol / L ammonia water, add polyvinylpyrrolidone to the precipitant solution, and the concentration of polyvinylpyrrolidone in the precipitant solution is 10 mg / ml. The cerium salt solution is a cerium nitrate hexahydrate solution with a concentration of 0.033 mol / L. Under room temperature conditions, inject the precipitant solution and the cerium salt solution into the ultrasonic microreactor respectively; the frequency of the ultrasonic microreactor is 20 kHz and the power is 30 W; control the injection flow rates of the precipitant solution and the cerium salt solution to be the same, and the injection flow rates are both 6 ml / min - 200 ml / min, and the residence time is 0 min - 1 min to obtain a precursor. The obtained precursor is heated at 120 °C for 2 hours while introducing air, and the flow rate of the introduced air is 100 cm 3 / min. After solid-liquid separation, the product is obtained. Wash the obtained product three times with water and once with ethanol. Dry the washed product at 60 °C, and then calcine it at 400 °C for 2 hours to obtain a spherical-like cerium oxide product.

7. The method for synthesizing nano cerium oxide according to claim 6, characterized in that, The precipitant solution was replaced with a 0.5 mol / L sodium carbonate precipitant solution to obtain olive-shaped cerium oxide products.

8. The method for synthesizing nano-ceria according to any one of claims 1-5, characterized in that the ultrasonic power of the ultrasonic microreactor is 30 W - 50 W.

9. The method for synthesizing nano-ceria according to any one of claims 1 to 5, characterized in that the calcination temperature is 400 °C - 600 °C.

10. The method for synthesizing nano-ceria according to claim 1, characterized in that the cerium salt solution is a cerium nitrate hexahydrate-ethylene glycol solution or an aqueous cerium nitrate hexahydrate solution, and the precipitant solution is an aqueous sodium hydroxide solution or a sodium hydroxide-ethylene glycol solution.

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