A method for preparing monodisperse spherical micron cerium oxide

Abstract

The invention discloses a method for preparing monodisperse spherical micron cerium oxide, which comprises: 1. adding chitosan to an acetic acid solution, stirring and dissolving to obtain a chitosan solution, then adding a cerium salt to the chitosan solution, stirring and dissolving and performing a hydrothermal reaction, taking out a precipitate after centrifugation, washing and drying to obtain a cerium complex; 2. placing the cerium complex in a muffle furnace, heating and reacting to obtain a monodisperse spherical micron cerium oxide. The invention utilizes chitosan with good dispersing and complexing effects as a complexing agent and a reducing agent, and while reducing the cerium salt by a hydrothermal reaction, the reduced product is fully dispersed and complexed to avoid its agglomeration, and spherical, monodispersed, uniformly sized and stable micron cerium oxide particles are prepared by roasting and oxidation, and the size and shape of the cerium oxide particles are effectively controlled, the process is simple, the repeatability is good, the raw material source is wide, the energy consumption is low, it is green and environmentally friendly, and it is conducive to large-scale industrial production.

Description

Technical Field

[0001] The invention belongs to the technical field of micro-nano powders, and in particular relates to a method for preparing monodisperse spherical micron cerium oxide. Background Art

[0002] Rare earth polishing materials are mixed powders with cerium oxide as the main component, which are used to improve the surface finish of products or parts. Compared with traditional abrasive materials such as Fe2O3 and Al2O3, rare earth polishing powder has the advantages of fine particle size, good chemical activity, strong grinding ability and long service life. It is widely used in optical glass parts, TV picture tube glass shells, eyeglass lenses, flat glass, oscilloscopes and organic glass products. In 2021, my country's output of rare earth polishing materials was 44,000 tons, a year-on-year increase of 29.7%, ranking first in the world. Among them, cerium oxide (CeO2), as the main component of rare earth polishing materials, generally requires the raw material particle size to be 0.8μm~2μm, the crystal consistency is higher than 95%, and the morphology is spherical.

[0003] Research results in recent decades have shown that the structural characteristics of CeO2 particles are one of the most important indicators of their application performance. Among them, spherical CeO2 particles with high dispersibility and narrow particle size distribution are the best structures for grinding materials, polishing powders, etc. At present, the commercial production of cerium dioxide is mainly through the thermal decomposition of cerium salts (such as cerium carbonate, cerium hydroxide or cerium nitrate), and then mechanical grinding and classification to finally obtain the product. Although this method can obtain highly chemically active CeO2, the size and shape of the particles are difficult to control.

[0004] In order to overcome the above problems, a variety of processes for preparing CeO2 have been proposed, including the sol-gel method and the flux thermal method. The sol-gel method is to add a precipitant (such as urea, alkali metal hydroxide, ammonia water, etc.) to an aqueous solution containing cerium salts, and the resulting product is separated, dried and heat-treated to obtain nano CeO2. This method does not deviate from the essence of the traditional method. It is very easy to agglomerate during the drying process and is easy to turn into hard agglomerates during high-temperature heat treatment. Subsequent mechanical crushing and grading are still required, so the product quality is difficult to fundamentally improve. The flux thermal method is the decomposition of cerium salts in high-temperature molten salts. In this process method, there are major problems in the separation and cleaning of the products. In general, these methods have obvious process characteristics, and the products prepared also show certain performance characteristics, but it still takes a long time to reach industrial production scale. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing monodisperse spherical micron cerium oxide in view of the shortcomings of the above-mentioned prior art. The present invention combines green hydrothermal reaction with roasting oxidation method, and utilizes chitosan dispersion, complexation and reduction to obtain spherical, monodisperse, uniform and stable micron cerium oxide particles, effectively controlling the size and shape of cerium oxide particles, solving the problem that the current preparation method is not environmentally friendly, and saving costs.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing monodisperse spherical micron cerium oxide, characterized in that the method comprises the following steps:

[0007] Step 1, adding chitosan to an acetic acid solution and stirring to dissolve to obtain a chitosan solution, then adding a cerium salt to the chitosan solution and stirring to dissolve and performing a hydrothermal reaction, taking out a precipitate after centrifugation, washing and drying to obtain a cerium complex;

[0008] Step 2: Place the cerium complex obtained in step 1 in a muffle furnace and heat to react to obtain monodisperse spherical micron cerium oxide.

[0009] The above-mentioned method for preparing monodisperse spherical micron cerium oxide is characterized in that the cerium salt in step 1 is cerium nitrate hexahydrate or cerium carbonate.

[0010] The above-mentioned method for preparing monodisperse spherical micron cerium oxide is characterized in that the mass ratio of chitosan in the chitosan solution, the volume of acetic acid and the mass ratio of cerium nitrate hexahydrate in step 1 is 0.6-12:2-40:8-100, wherein the unit of mass is g and the unit of volume is mL. This preferred raw material ratio effectively ensures that the chitosan solution is within a suitable viscosity range, which is conducive to the smooth progress of the hydrothermal reaction.

[0011] The above-mentioned method for preparing monodisperse spherical micron cerium oxide is characterized in that the temperature of the hydrothermal reaction in step 1 is 150°C to 200°C, the time is 5h to 15h, the centrifugal time is 1min to 10min, the number of washings is 3 to 7 times, and the drying time is 8h to 24h. The process parameters ensure the hydrothermal reaction and the subsequent centrifugation, washing, and drying processes, and ensure the smooth acquisition of monodisperse spherical micron cerium oxide.

[0012] The above-mentioned method for preparing monodisperse spherical micron cerium oxide is characterized in that the temperature of heating in the muffle furnace in step 2 is 350°C to 650°C and the time is 2h to 6h. The temperature and time of heating, roasting and oxidation ensure that monodisperse spherical micron cerium oxide is successfully obtained.

[0013] Compared with the prior art, the present invention has the following advantages:

[0014] 1. The present invention firstly utilizes chitosan with good dispersing and complexing effects as a complexing agent and a reducing agent, and while reducing the cerium salt by a hydrothermal reaction, fully disperses and complexes the reduction product to avoid its agglomeration, thereby obtaining a uniformly dispersed cerium complex, and then removes the residual chitosan by heating, roasting, and oxidation, thereby preparing spherical, monodisperse, uniformly sized and stable micron cerium oxide particles, without the need for mechanical dispersion and classification, and subsequent separation and cleaning processes, thereby effectively controlling the size and shape of the cerium oxide particles and meeting the market's usage requirements.

[0015] 2. The present invention uses chitosan as a complexing agent and a reducing agent. Chitosan has a wide source, low cost, is safe and non-toxic, and has stable performance. It solves the problem that cerium oxide is not environmentally friendly when prepared with toxic chemicals, saves raw material costs, and improves the practicality of the method of the present invention.

[0016] 3. The present invention combines the hydrothermal method with the roasting method, has a simple process, good repeatability, a wide source of raw materials, low energy consumption, and is conducive to large-scale industrial production.

[0017] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is the XRD pattern of the monodisperse spherical micron cerium oxide prepared in Example 2 of the present invention.

[0019] Figure 2a This is a SEM image (×10000) of the monodisperse spherical micron cerium oxide prepared in Example 2 of the present invention.

[0020] Figure 2b This is a SEM image (×5000) of the monodisperse spherical micron cerium oxide prepared in Example 2 of the present invention.

[0021] Figure 2c This is a SEM image (×2000) of the monodisperse spherical micron cerium oxide prepared in Example 2 of the present invention.

[0022] Figure 2d This is a SEM image (×1000) of the monodisperse spherical micron cerium oxide prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0023] Example 1

[0024] This embodiment includes the following steps:

[0025] Step 1, adding 2 mL of acetic acid to 98 mL of deionized water, mixing by magnetic stirring to obtain an acetic acid solution; slowly adding 0.6 g of chitosan to the acetic acid solution, stirring and dissolving to obtain a chitosan solution, and then adding 8 g of cerium nitrate hexahydrate to the chitosan solution, stirring and dissolving and fully mixing to obtain a mixed solution, placing the mixed solution in a muffle furnace and heating it to 150° C. for hydrothermal reaction for 5 hours, centrifuging at 6000 rpm for 1 minute, taking out the precipitate, washing it 3 times, and then placing it in a drying oven at 50° C. for 8 hours to obtain a cerium complex;

[0026] Step 2: Place the cerium complex obtained in step 1 into a muffle furnace, heat it to 350° C. at a rate of 3° C. / min, and calcine it for 2 h for oxidation to obtain monodisperse spherical micron cerium oxide particles.

[0027] The cerium salt in this embodiment can also be replaced by cerium carbonate.

[0028] Example 2

[0029] This embodiment includes the following steps:

[0030] Step 1, adding 4 mL of acetic acid to 196 mL of deionized water, mixing by magnetic stirring to obtain an acetic acid solution; slowly adding 1.2 g of chitosan to the acetic acid solution, stirring and dissolving to obtain a chitosan solution, and then adding 16 g of cerium nitrate hexahydrate to the chitosan solution, stirring and dissolving and fully mixing to obtain a mixed solution, placing the mixed solution in a muffle furnace and heating it to 180° C. for hydrothermal reaction for 12 hours, centrifuging at 10000 rpm for 5 minutes, taking out the precipitate, washing it 5 times, and then placing it in a drying oven at 60° C. for 12 hours to obtain a cerium complex;

[0031] Step 2: Place the cerium complex obtained in step 1 into a muffle furnace, heat it to 450° C. at a rate of 3° C. / min, and calcine for 3 h for oxidation to obtain monodisperse spherical micron cerium oxide particles.

[0032] Figure 1 The XRD pattern of the monodisperse spherical micron cerium oxide prepared in this example is as follows: Figure 1 It can be seen that there are obvious cerium oxide diffraction peaks at 28.83, 33.30, 47.70, 56.55, 69.72, 76.94, 79.13 and 88.75, indicating that the product prepared in this example is cerium oxide.

[0033] Figure 2a~Figure 2d The SEM images of the monodisperse spherical micron cerium oxide prepared in this example at different magnifications are shown in FIG. Figure 2a~Figure 2d It can be seen that the particle size of the monodisperse spherical micron cerium oxide is 1.5 μm to 2 μm.

[0034] The specific surface area of ​​the monodisperse spherical micron cerium oxide prepared in this embodiment is 28.19 m 2 / g.

[0035] Example 3

[0036] This embodiment includes the following steps:

[0037] Step 1, adding 40 mL of acetic acid to 1960 mL of deionized water, mixing by magnetic stirring to obtain an acetic acid solution; slowly adding 12 g of chitosan to the acetic acid solution, stirring and dissolving to obtain a chitosan solution, and then adding 100 g of cerium nitrate hexahydrate to the chitosan solution, stirring and dissolving and fully mixing to obtain a mixed solution, placing the mixed solution in a muffle furnace and heating it to 200° C. for hydrothermal reaction for 24 hours, centrifuging at 12000 rpm for 10 minutes, taking out the precipitate, washing it 7 times, and then placing it in a drying oven and drying it at 80° C. for 24 hours to obtain a cerium complex;

[0038] Step 2: Place the cerium complex obtained in step 1 into a muffle furnace, heat it to 650° C. at a rate of 10° C. / min, and calcine for 6 hours for oxidation to obtain monodisperse spherical micron cerium oxide particles.

[0039] Example 4

[0040] This embodiment includes the following steps:

[0041] Step 1, add 6 mL of acetic acid to 294 mL of deionized water, mix evenly by magnetic stirring, and obtain an acetic acid solution; slowly add 1.8 g of chitosan to the above acetic acid solution, stir and dissolve, and obtain a chitosan solution; then add 24 g of cerium nitrate hexahydrate to the above chitosan solution, stir and dissolve, and fully mix to obtain a mixed solution, place the mixed solution in a muffle furnace and heat it to 170° C. for hydrothermal reaction for 18 hours, centrifuge at 11000 rpm for 4 minutes, take out the precipitate, wash it 4 times, and then put it in a drying oven at 70° C. for 16 hours to obtain a cerium complex;

[0042] Step 2: Place the cerium complex obtained in step 1 into a muffle furnace, heat it to 550° C. at a rate of 5° C. / min, and calcine for 3 hours for oxidation to obtain monodisperse spherical micron cerium oxide particles.

[0043] Example 5

[0044] This embodiment includes the following steps:

[0045] Step 1, adding 20 mL of acetic acid to 980 mL of deionized water, mixing by magnetic stirring to obtain an acetic acid solution; slowly adding 6 g of chitosan to the acetic acid solution, stirring and dissolving to obtain a chitosan solution, and then adding 80 g of cerium nitrate hexahydrate to the chitosan solution, stirring and dissolving and fully mixing to obtain a mixed solution, placing the mixed solution in a muffle furnace and heating it to 190° C. for hydrothermal reaction for 15 hours, centrifuging at 12000 rpm for 5 minutes, taking out the precipitate, washing it 5 times, and then placing it in a drying oven at 80° C. for 12 hours to obtain a cerium complex;

[0046] Step 2: Place the cerium complex obtained in step 1 into a muffle furnace, heat it to 400° C. at a rate of 8° C. / min, and calcine it for 4 hours for oxidation to obtain monodisperse spherical micron cerium oxide particles.

[0047] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing monodisperse spherical micron cerium oxide, characterized in that: The method comprises the following steps: Step 1, adding chitosan to an acetic acid solution and stirring to dissolve to obtain a chitosan solution, then adding a cerium salt to the chitosan solution and stirring to dissolve and performing a hydrothermal reaction, taking out a precipitate after centrifugation, washing and drying to obtain a cerium complex; the mass ratio of chitosan in the chitosan solution, the volume of acetic acid and the mass ratio of the cerium salt are 0.6-12:2-40:8-100, wherein the unit of mass is g and the unit of volume is mL; PVP is not added to the hydrothermal reaction system; Step 2: Place the cerium complex obtained in step 1 in a muffle furnace and heat to react to obtain monodisperse spherical micron cerium oxide.

2. The method for preparing monodisperse spherical micron cerium oxide according to claim 1, characterized in that: The cerium salt in step 1 is cerium nitrate hexahydrate or cerium carbonate.

3. The method for preparing monodisperse spherical micron cerium oxide according to claim 1, characterized in that: The temperature of the hydrothermal reaction in step 1 is 150°C to 200°C, the time is 5h to 15h, the centrifugal time is 1min to 10min, the number of washings is 3 to 7 times, and the drying time is 8h to 24h.

4. The method for preparing monodisperse spherical micron cerium oxide according to claim 1, characterized in that: The heating temperature in the muffle furnace in step 2 is 350° C. to 650° C., and the heating time is 2 h to 6 h.

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