Green method for preparing monodisperse rod-like micron cerium oxide

Abstract

The invention discloses a green method for preparing monodisperse rod-like micron cerium oxide, which comprises the following steps: 1, adding alkali lignin into deionized water to obtain an alkali lignin solution, then adding cerium nitrate hexahydrate and polyvinylpyrrolidone into the alkali lignin solution to carry out hydrothermal reaction, centrifuging, then taking out precipitate, and sequentially washing and freeze-drying the precipitate to obtain a cerium oxide precursor; a cerium complex precursor is obtained; and 2, carrying out segmented reaction on the cerium complex precursor to obtain cerium oxide. The monodisperse rod-like micron cerium oxide with uniform size is prepared by using the alkali lignin with good dispersion and complexation effects as the complexing agent and the dispersing agent, is suitable for the polishing field of glass, does not need subsequent separation or cleaning, is wide in raw material source, low in cost, safe, non-toxic and stable in performance, realizes green preparation, is simple in process, and is suitable for industrial production. The energy consumption is low, the amplification difficulty is relatively low, and large-scale industrial production is facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of micro-nano powder preparation, and in particular to a green method for preparing monodisperse rod-shaped 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 0.8~2μm and the crystal consistency to be higher than 95%.

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

[0004] In order to overcome the above problems, in recent years, a variety of new 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 salt, and the resulting precipitate product is separated, dried and heat-treated to obtain nano CeO2. However, this preparation method has not yet deviated from the essence of the traditional method. The precursor particles are very easy to agglomerate during the thermal drying process, resulting in the agglomerated particles being easily transformed into hard agglomerates during high-temperature heat treatment. The resulting product still requires subsequent mechanical crushing and grading, so the product quality is difficult to be fundamentally improved. On the other hand, the flux thermal method utilizes the decomposition of cerium salt in high-temperature molten salt and disperses the resulting particles with the help of the fluidity of the molten salt. In this process method, there are major problems in the separation and cleaning of the product. Overall, these methods have obvious process characteristics, and the products prepared also show certain performance advantages, 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 green method for preparing monodisperse rod-shaped micron cerium oxide in view of the shortcomings of the above-mentioned prior art. The method uses alkali lignin with good dispersing and complexing effects as a complexing agent and dispersant to prepare monodisperse, rod-shaped and uniformly sized micron cerium oxide, without the need for subsequent separation or cleaning, and the raw material has a wide source, low cost, safety and non-toxicity, stable performance, and realizes green preparation, solving the problem that the cerium oxide particles prepared by the prior art are easy to agglomerate or the subsequent treatment is cumbersome.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a green method for preparing monodisperse rod-shaped micron cerium oxide, characterized in that the method comprises the following steps: Step 1, adding alkali lignin into deionized water and stirring to dissolve to obtain an alkali lignin solution, then adding cerium nitrate hexahydrate and polyvinyl pyrrolidone into the alkali lignin solution, stirring to dissolve and performing a hydrothermal reaction, taking out a precipitate after centrifugation, and washing and freeze-drying the precipitate in turn to obtain a cerium complex precursor; Step 2: Place the cerium complex precursor obtained in step 1 into a muffle furnace for staged reaction to obtain monodisperse rod-shaped micronized cerium oxide.

[0007] The above-mentioned green method for preparing monodisperse rod-shaped micron cerium oxide is characterized in that the mass of alkali lignin in the alkali lignin solution in step one is 75g~1650g, the volume of deionized water is 2L~33L, the added mass of cerium nitrate hexahydrate is 37.5g~825g, and the added mass of polyvinyl pyrrolidone is 30g~660g.

[0008] The above-mentioned green method for preparing monodisperse rod-shaped micron cerium oxide is characterized in that the temperature of the hydrothermal reaction in step one is 130°C~180°C, and the time is 3h~10h; the centrifugal speed is 6000rpm~12000rpm, the time is 1min~10min, the washing number is 3~7 times, and the freeze-drying time is 12h~24h.

[0009] The above-mentioned green method for preparing monodisperse rod-shaped micron cerium oxide is characterized in that the staged reaction in step 2 includes two stages of reaction: the first stage reaction temperature is 300°C to 500°C, the roasting time is 1h to 3h, and the second stage reaction temperature is 500°C to 800°C, and the roasting time is 1h to 3h. The present invention adopts staged roasting to avoid the cerium complex precursor powder directly reacting violently at high temperature and causing agglomeration.

[0010] The above-mentioned green method for preparing monodisperse rod-shaped micron cerium oxide is characterized in that the particle size of the cerium oxide in step 2 is 1.5μm~2μm, the size is uniform, and it is monodisperse rod-shaped.

[0011] Compared with the prior art, the present invention has the following advantages: 1. The present invention adopts alkali lignin as a complexing agent and dispersant, and polyvinyl pyrrolidone as a dispersant. By utilizing the good dispersing and complexing properties of alkali lignin, a large number of hydroxyl groups, aldehyde groups and carboxyl groups contained in the alkali lignin are combined with cerium ions to form a cerium complex precursor, which is then calcined and heat-treated to form cerium oxide, thereby avoiding the agglomeration of cerium salts during the heat treatment. At the same time, the macromolecular alkali lignin is conducive to the dispersion of the cerium complex precursor and limits the growth of crystal faces in the precursor, thereby preparing monodisperse, rod-shaped and uniformly sized micron cerium oxide, which does not require subsequent separation or cleaning, and solves the problem that the cerium oxide particles prepared by the prior art are easy to agglomerate or the subsequent treatment is cumbersome.

[0012] 2. The present invention uses alkali lignin as a complexing agent and a reducing agent. This raw material has a wide source, low cost, is safe and non-toxic, and avoids the problem of environmental pollution caused by the preparation of cerium oxide with toxic chemicals. It also has stable performance and realizes green preparation.

[0013] 3. The present invention adopts a hydrothermal method and a staged roasting method, which has simple process, low energy consumption, relatively low difficulty in scaling up, and is conducive to large-scale industrial production.

[0014] 4. The particle size of the cerium oxide prepared by the present invention is 1.5 μm to 2 μm, the size is uniform, and it is in the shape of a monodispersed rod, and is suitable for the field of glass polishing.

[0015] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the XRD pattern of cerium oxide prepared in Example 2 of the present invention.

[0017] Figure 2 This is a SEM image of cerium oxide prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0018] Example 1 This embodiment includes the following steps: Step 1: slowly add 75g of alkali lignin into 2L of deionized water and stir to dissolve to obtain an alkali lignin solution, then add 37.5g of cerium nitrate hexahydrate and 30g of polyvinyl pyrrolidone to the alkali lignin solution, stir and dissolve the components to obtain a mixed solution, place the mixed solution in a 50L stainless steel hydrothermal reactor and heat it to 130°C for hydrothermal reaction for 10h, centrifuge at a speed of 6000rpm for 1min, take out the precipitate, wash the precipitate 3 times, and then put it into a freeze dryer for freeze drying for 12h to obtain a cerium complex precursor; Step 2: Place the cerium complex precursor obtained in step 1 into a muffle furnace, calcine at 300° C. for 3 h, and then heat to 600° C. for 3 h for oxidation to obtain monodisperse rod-shaped micronized cerium oxide.

[0019] According to the test, the particle size of the cerium oxide prepared in this embodiment is 1.5 μm-2 μm, the size is uniform, and the particle size is monodispersed rod-shaped.

[0020] Example 2 This embodiment includes the following steps: Step 1: slowly add 1650g of alkali lignin into 33L of deionized water and stir to dissolve to obtain an alkali lignin solution, then add 825g of cerium nitrate hexahydrate and 660g of polyvinyl pyrrolidone to the alkali lignin solution, stir and dissolve the components to obtain a mixed solution, place the mixed solution in a 50L stainless steel hydrothermal reactor and heat it to 180°C for hydrothermal reaction for 3h, centrifuge at a speed of 12000rpm for 10min0, take out the precipitate, wash the precipitate 7 times, and then put it into a freeze dryer for freeze drying for 24h to obtain a cerium complex precursor; Step 2: Place the cerium complex precursor obtained in step 1 into a muffle furnace, calcine at 500° C. for 1 hour, and then heat to 800° C. for 1 hour for oxidation to obtain monodisperse rod-shaped micron cerium oxide.

[0021] Figure 1 The XRD pattern of cerium oxide prepared in this example is as follows. Figure 1 It can be seen that cerium oxide has obvious diffraction peaks at 28.83, 33.30, 47.70, 56.55, 69.72, 76.94, 79.13 and 88.75, which are consistent with CeO2 numbered PDF#34-0394 in the standard library, indicating that the product of this example is cerium oxide.

[0022] Figure 2 This is the SEM image of the cerium oxide prepared in this example. Figure 2 It can be seen that the particle size of cerium oxide prepared using alkali lignin as a complexing agent is 1.5 μm~2 μm, the size is uniform, and the shape is a rod-like structure.

[0023] Example 3 This embodiment includes the following steps: Step 1: slowly add 500g of alkali lignin into 10L of deionized water and stir to dissolve to obtain an alkali lignin solution, then add 250g of cerium nitrate hexahydrate and 200g of polyvinyl pyrrolidone to the alkali lignin solution, stir and dissolve the components to obtain a mixed solution, place the mixed solution in a 50L stainless steel hydrothermal reactor and heat it to 150°C for hydrothermal reaction for 8h, centrifuge at a speed of 10000rpm for 8min, take out the precipitate, wash the precipitate 4 times, and then put it into a freeze dryer for freeze drying for 18h to obtain a cerium complex precursor; Step 2: Place the cerium complex precursor obtained in step 1 into a muffle furnace, calcine at 400° C. for 2 h, and then heat to 700° C. and calcine for 2 h for oxidation to obtain monodisperse rod-shaped micron cerium oxide.

[0024] According to the test, the particle size of the cerium oxide prepared in this embodiment is 1.5 μm-2 μm, the size is uniform, and the particle size is monodispersed rod-shaped.

[0025] Example 4 This embodiment includes the following steps: Step 1: slowly add 1000g of alkali lignin into 20L of deionized water and stir to dissolve to obtain an alkali lignin solution, then add 500g of cerium nitrate hexahydrate and 400g of polyvinyl pyrrolidone to the alkali lignin solution, stir and dissolve the components to obtain a mixed solution, place the mixed solution in a 50L stainless steel hydrothermal reactor and heat it to 160°C for hydrothermal reaction for 8h, centrifuge at a speed of 11000rpm for 5min, take out the precipitate, wash the precipitate 5 times, and then put it into a freeze dryer for freeze drying for 20h to obtain a cerium complex precursor; Step 2: Place the cerium complex precursor obtained in step 1 into a muffle furnace, calcine at 500° C. for 1 h, and then heat to 800° C. for 2 h for oxidation to obtain monodisperse rod-shaped micronized cerium oxide.

[0026] According to the test, the particle size of the cerium oxide prepared in this embodiment is 1.5 μm-2 μm, the size is uniform, and the particle size is monodispersed rod-shaped.

[0027] Example 5 This embodiment includes the following steps: Step 1: slowly add 1500g of alkali lignin into 30L of deionized water and stir to dissolve to obtain an alkali lignin solution, then add 750g of cerium nitrate hexahydrate and 600g of polyvinyl pyrrolidone to the alkali lignin solution, stir and dissolve the components to obtain a mixed solution, place the mixed solution in a 50L stainless steel hydrothermal reactor and heat it to 145°C for hydrothermal reaction for 8h, centrifuge at a speed of 12000rpm for 4min, take out the precipitate, wash the precipitate 3 times, and then put it into a freeze dryer for freeze drying for 20h to obtain a cerium complex precursor; Step 2: Place the cerium complex precursor obtained in step 1 into a muffle furnace, calcine at 300° C. for 3 h, and then heat to 800° C. for 1 h for oxidation to obtain monodisperse rod-shaped micronized cerium oxide.

[0028] According to the test, the particle size of the cerium oxide prepared in this embodiment is 1.5 μm-2 μm, the size is uniform, and the particle size is monodispersed rod-shaped.

[0029] 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 green method for preparing monodisperse rod-shaped micronized cerium oxide, characterized in that: The method comprises the following steps: Step 1, adding alkali lignin into deionized water and stirring to dissolve to obtain an alkali lignin solution, then adding cerium nitrate hexahydrate and polyvinyl pyrrolidone into the alkali lignin solution, stirring to dissolve and performing a hydrothermal reaction, taking out a precipitate after centrifugation, and washing and freeze-drying the precipitate in turn to obtain a cerium complex precursor; Step 2: Place the cerium complex precursor obtained in step 1 into a muffle furnace for staged reaction to obtain monodisperse rod-shaped micronized cerium oxide.

2. A green method for preparing monodisperse rod-shaped micronized cerium oxide according to claim 1, characterized in that: The mass of alkali lignin in the alkali lignin solution in step 1 is 75g~1650g, the volume of deionized water is 2L~33L, the added mass of cerium nitrate hexahydrate is 37.5g~825g, and the added mass of polyvinyl pyrrolidone is 30g~660g.

3. The green method for preparing monodisperse rod-shaped micron cerium oxide according to claim 1, characterized in that: The temperature of the hydrothermal reaction in step 1 is 130°C~180°C, and the time is 3h~10h; the speed of the centrifugation is 6000rpm~12000rpm, the time is 1min~10min, the number of washing times is 3~7 times, and the freeze-drying time is 12h~24h.

4. The green method for preparing monodisperse rod-shaped micron cerium oxide according to claim 1, characterized in that: The staged reaction in step 2 includes two stages: the first stage reaction temperature is 300°C to 500°C, the roasting time is 1h to 3h, and the second stage reaction temperature is 500°C to 800°C, the roasting time is 1h to 3h.

5. The green method for preparing monodisperse rod-shaped micron cerium oxide according to claim 1, characterized in that: The particle size of the cerium oxide in step 2 is 1.5 μm to 2 μm, the size is uniform, and the cerium oxide is in the shape of monodispersed rods.

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