A method for preparing ultrafine high-purity aluminum hydroxide, ultrafine high-purity aluminum hydroxide and its application

Abstract

A method for preparing ultrafine high-purity aluminum hydroxide, ultrafine high-purity aluminum hydroxide and its application, comprising: adding seed crystals to a sodium aluminate solution, decomposing to obtain an inducer, adding the inducer to the sodium aluminate solution for decomposition, separating and washing to obtain ultrafine high-purity aluminum hydroxide. In the present application, the inducer obtained by the first-stage decomposition is a milky white homogeneous precipitate composed of nanoparticles. Adding the inducer for the second-stage decomposition can inhibit disordered nucleation in the solution, and the obtained aluminum hydroxide has the advantages of fine particle size and high purity; high-purity ultrafine aluminum hydroxide can be subjected to hydrothermal treatment to obtain high-purity ultrafine boehmite, with a purity of over 99.99%; the ultrafine high-purity alumina obtained in the present application has a purity of over 99.99%, and the product particle size D 50 : 0.1-0.5μm, with controllable specific surface area, it can be widely used in high-end fields such as electronic ceramics, structural ceramics, transparent ceramics, catalyst supports, CMP polishing, etc.

Description

Technical Field

[0001] The present application belongs to the technical field of multi-variety aluminum oxide, and specifically relates to a preparation method of ultrafine high-purity aluminum hydroxide, ultrafine high-purity aluminum hydroxide and applications thereof. Background Art

[0002] In recent years, with the rapid development of electronic information technology and new energy technologies, new requirements have been put forward for the application of electronic ceramics, developing towards miniaturization, high purification, and functionalization. Alumina ceramics account for more than 90% of electronic ceramics, resulting in an increasing demand for ultrafine high-purity alumina. High-purity alumina has high insulation, heat resistance, super wear resistance, and high corrosion resistance. It is widely used in defense and military industry, aerospace, 5G communications, new energy, and semiconductor fields, and is an irreplaceable key material. At present, my country still has some key technologies for the preparation of ultrafine high-purity alumina powder. Problems such as low quality, high production costs, and poor batch stability cannot meet the needs of my country in key areas. Domestic enterprises and research institutions have also conducted continuous research and development. Ultrafine high-purity alumina production technologies mainly include ammonium aluminum sulfate process, aluminum carbonate process, aluminum alcohol process, choline process, hydrolysis process, hydrothermal process, modified Bayer process, sol-gel process, etc.

[0003] CN110436496A discloses a method for preparing ultrafine high-purity aluminum oxide using industrial sodium aluminate solution, comprising: (1) taking an industrial sodium aluminate solution and performing deep ultrasonic purification to obtain a high-purity sodium aluminate solution; (2) adding an alcohol reagent to the high-purity sodium aluminate solution obtained in step (1) for ultrasonic emulsification; (3) adding a crystallization aid to the emulsified solution in step (2) and precipitating aluminum hydroxide crystals in an ultrasonic state; and (4) ultrasonically acid-washing the aluminum hydroxide crystals obtained in step (3), drying them, and then calcining them to obtain ultrafine high-purity aluminum oxide powder.

[0004] CN107529518A provides a method for preparing ultrafine alumina, comprising the following steps: (1) coarsely grinding alumina slurry in the presence of a first dispersant; (2) filtering the coarsely ground alumina slurry; (3) finely grinding the filtered alumina slurry in the presence of a second dispersant; and (4) drying and crushing the finely ground alumina slurry, wherein the first dispersant is ammonium polyacrylate and the second dispersant is a mixture of polyacrylic acid and ammonium polyacrylate.

[0005] CN108329036A achieves this through the following steps: first, preparing a mixed powder of Al2O3 and carbon powder; then, placing the mixed powder in a BN crucible and sintering it under atmospheric pressure to produce ultrafine, high-purity AlON powder. The present invention uses conventional alumina and carbon powder as raw materials to produce AlON powder at relatively low temperatures. The preparation process is simple, controllable, and highly operable. The AlON powder produced by the present invention has high purity and small particle size.

[0006] CN112047367B discloses a method for preparing highly active aluminum hydroxide crystals, comprising: adding aluminum hydroxide seed crystals into a sodium aluminate solution to carry out a clustering reaction to obtain highly active aluminum hydroxide crystals, wherein the added mass of the aluminum hydroxide seed crystals is 1 g / L to 100 g / L of the sodium aluminate solution, and the aluminum hydroxide particle size of the aluminum hydroxide seed crystals is D 50 1 to 60 μm; the sodium aluminate solution satisfies the following conditions: Na2O k The mass concentration is 100-200 g / L, the caustic ratio αk is 1.2-2.0; the cluster reaction temperature is 65-90°C. A method for preparing low-zinc aluminum hydroxide is also disclosed, characterized in that the method comprises: obtaining a sodium aluminate solution and aluminum hydroxide seeds, wherein the sodium aluminate solution meets the following conditions: Na2O k The mass concentration is 100-200 g / L, the caustic ratio αk is 1.2-2.0, the sodium aluminate solution contains Zn; the aluminum hydroxide particle size D of the aluminum hydroxide seed crystal is 50 The sodium aluminate solution and the aluminum hydroxide seed crystals are subjected to a clustering reaction to obtain a slurry, the clustering reaction temperature is 65 to 90° C., and the added mass of the aluminum hydroxide seed crystals is 1 g / L sodium aluminate solution to 100 g / L sodium aluminate solution; the slurry is separated into a solid and a liquid and a high-activity aluminum hydroxide crystal that adsorbs zinc; the liquid is subjected to a seed decomposition reaction to obtain low-zinc aluminum hydroxide.

[0007] The particle size and purity of the aluminum hydroxide produced in the above prior art still cannot meet the demand for ultrafine high-purity aluminum oxide in actual use. Summary of the Invention

[0008] In order to solve the above problems, the present application proposes a method for preparing ultrafine high-purity aluminum hydroxide, ultrafine high-purity aluminum hydroxide and its application, including:

[0009] A method for preparing ultrafine high-purity aluminum hydroxide comprises the following steps: adding seed crystals to a sodium aluminate solution, decomposing the seed crystals to obtain an inducer, adding the inducer to the sodium aluminate solution, decomposing the inducer, and separating and washing the inducer to obtain ultrafine high-purity aluminum hydroxide.

[0010] Preferably, the method for preparing the seed crystals is as follows: mixing the seed crystal raw material with water, configuring them according to a material-water ratio of 1:(3-8), preparing ultrafine seed crystals by grinding, the grinding equipment being lined with polyurethane, the grinding media being high-purity alumina microbeads, high-purity water, etc., grinding at 2000 r / min for 0.5 to 5 hours, removing large particles by membrane filtration, the pore size of the membrane being 0.5 to 1.5 μm, and obtaining the filtrate which is the seed crystal solution, wherein the Al2O3 content is 0.5 to 5%.

[0011] Preferably, the seed crystal raw material is selected from high-purity aluminum hydroxide (99.9%), low-sodium pseudo-boehmite (Na2O<0.1%), high-purity pseudo-boehmite obtained by alcohol aluminum method, high-purity aluminum hydroxide obtained by hydrolysis method or aluminum colloid obtained by neutralization method.

[0012] Preferably, the seed crystal raw material is selected from high-purity pseudo-boehmite obtained by the alcohol aluminum process.

[0013] Preferably, the preparation method of the sodium aluminate solution is: high-purity aluminum hydroxide is selected as the raw material, and the sodium aluminate solution is prepared by high-temperature dissolution with ion membrane liquid alkali, and the ratio is adjusted according to αk (Na2O / Al2O3 molar ratio) = 1.3 to 1.8. The sodium aluminate solution is purified and refined to obtain a qualified high-purity sodium aluminate solution.

[0014] Preferably, the high-purity aluminum hydroxide raw material is selected from modified Bayer process high-purity aluminum hydroxide, high-purity pseudo-boehmite, alcohol aluminum process high-purity pseudo-boehmite, hydrolysis process high-purity aluminum hydroxide or neutralization process aluminum colloid.

[0015] Preferably, the high-purity aluminum hydroxide raw material is selected from modified Bayer process high-purity aluminum hydroxide.

[0016] Preferably, the method further comprises: taking a certain amount of sodium aluminate solution and preparing it so that the Al2O3 content is 30-100 g / L, adding seed crystals into the prepared sodium aluminate solution in an amount of 0.5-2% of the Al2O3 content of the sodium aluminate solution, controlling the temperature at 30-70°C, and decomposing it under high-speed stirring for 5-20 hours to obtain an inducer.

[0017] Preferably, the method further comprises: taking a certain amount of sodium aluminate solution and preparing it so that the Al2O3 content is 80-150 g / L, adding an inducer to the prepared sodium aluminate solution at a rate of 0.5-2% of the Al2O3 content of the sodium aluminate solution, controlling the temperature at 40-80°C, decomposing for 8-20 hours, and separating and washing to obtain ultrafine high-purity aluminum hydroxide.

[0018] An ultrafine high-purity aluminum hydroxide with a purity of more than 99.99% and a particle size of 0.1 to 0.5 μm.

[0019] A high-purity boehmite with a purity of more than 99.99% and a particle size of 0.1 to 0.5 μm is prepared by adding high-purity aluminum hydroxide into an autoclave at a solid content of 150 to 250 g / L, stirring and heating to 160 to 220° C. for a holding time of 0.5 to 3 hours, and separating and washing to obtain the high-purity boehmite.

[0020] Disclosed is an ultrafine high-purity alumina having an alumina purity of over 99.99% and a product particle size D50 of 0.1 to 0.5 μm. The ultrafine high-purity alumina is prepared by calcining high-purity boehmite to obtain the ultrafine high-purity alumina.

[0021] Preferably, the calcination temperature of the high-purity boehmite is 1100-1500° C., and the calcination time is 100-300 min.

[0022] An ultrafine high-purity alumina is used in high-end fields such as electronic ceramics, structural ceramics, transparent ceramics, catalyst carriers, new energy batteries, and CMP polishing.

[0023] The purpose of grinding the seed crystals in the present application is to deagglomerate the originally agglomerated seed crystals in the seed crystal raw material, which is more conducive to the subsequent decomposition reaction.

[0024] The present application prepares ultrafine seed liquid through active crystal seeds and adopts a multi-stage decomposition process. The first stage decomposition produces an inducer, the second stage decomposition produces ultrafine high-purity aluminum hydroxide, the purity is improved by hydrothermal sodium removal, and high-purity boehmite is obtained, which is then roasted to obtain an ultrafine high-purity alumina product.

[0025] This application can bring the following beneficial effects:

[0026] 1. This application can prepare ultrafine high-purity aluminum hydroxide through multi-stage decomposition, which has the advantages of fine particle size and high purity;

[0027] 2. High-purity ultrafine aluminum hydroxide can be obtained through hydrothermal treatment to obtain high-purity ultrafine boehmite. The product has a narrow particle size distribution and a purity of more than 99.99%;

[0028] 3. By adjusting different process conditions, a series of products with different particle sizes and activities can be obtained to meet the needs of different application fields;

[0029] 4. The inducer obtained by the first-stage decomposition in this application is a milky white homogeneous precipitate composed of nanoparticles. Adding the inducer to the second-stage decomposition process can inhibit disordered nucleation in the solution and obtain aluminum hydroxide with uniform particle size;

[0030] 5. The purity of the ultra-fine high-purity alumina obtained in this application is as high as 99.99% or more, and the product particle size is fine. 50: 0.1~0.5μm, the specific surface area is controllable, and it can be widely used in high-end fields such as electronic ceramics, structural ceramics, transparent ceramics, catalyst carriers, new energy batteries, CMP polishing, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The drawings in the specification, which constitute a part of this application, are used to provide further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute improper limitations on this application.

[0032] Figure 1 This is the SEM image of ultrafine high-purity alumina;

[0033] Figure 2 This is the SEM image of ultrafine high-purity alumina; DETAILED DESCRIPTION

[0034] Example 1: (1) Preparation of seed solution: High-purity pseudo-boehmite obtained by the alcohol-aluminum process (Sasol SB, Germany) was selected as the raw material, slurried at a material:water ratio of 1:5, ground at 2000 r / min for 120 min, and filtered through a membrane with a pore size of 1.0 μm to remove large particles to obtain seed solution A1;

[0035] (2) Preparation of high-purity sodium aluminate solution: Selecting high-purity aluminum hydroxide from the modified Bayer process as raw material, sodium aluminate solution is prepared by high-temperature dissolution using ion membrane liquid alkali, and the ratio is adjusted according to αk (Na2O / Al2O3 molar ratio) = 1.3~1.8. The sodium aluminate solution is purified and refined to obtain high-purity sodium aluminate solution B1;

[0036] (3) A certain amount of high-purity sodium aluminate solution B1 was prepared, Al2O3: 70g / L, to obtain sodium aluminate solution B2. The seed solution A1 was slowly added to the prepared sodium aluminate solution B2, with the solid content being 1% of the Al2O3 content of the solution. The temperature was controlled at 50°C, and the solution was decomposed for 16 hours under high-speed stirring to obtain the inducer C1.

[0037] (4) A certain amount of high-purity sodium aluminate solution B1 was prepared, Al2O3: 100 g / L, to obtain sodium aluminate solution B3, and the inducer C1 was slowly added to the prepared sodium aluminate solution B3, and the solid content was added according to the Al2O3 content of the solution of 1.5%. The temperature was controlled at 45 ° C. Under high-speed stirring conditions, it was decomposed for 24 hours. After separation and washing, ultrafine high-purity aluminum hydroxide D1 was obtained, and chemical analysis was carried out. The particle size was detected by sedimentation particle size analyzer.

[0038] Example 2: The difference from Example 1 is that in step (1), the seed raw material is high-purity aluminum hydroxide (99.9%); in step (2), the raw material is selected from high-purity pseudo-boehmite; in step (3), the seed addition amount is 0.5%, the temperature is 30°C, and the decomposition time is 20h; ultrafine high-purity aluminum hydroxide D2 is obtained, and chemical analysis is performed, and the particle size is detected by sedimentation particle size analyzer analysis.

[0039] Example 3: The difference from Example 1 is that the seed raw material in step (1) is low-sodium pseudo-boehmite; the raw material in step (2) is selected from high-purity aluminum hydroxide produced by hydrolysis; the seed addition amount in step (3) is 2%, the temperature is 70°C, and the decomposition time is 5h; ultrafine high-purity aluminum hydroxide D3 is obtained, and chemical analysis is performed, and the particle size is detected by sedimentation particle size analyzer analysis.

[0040] Example 4: The difference from Example 1 is that the amount of inducer added in step (4) is 0.5%, the temperature is 40°C, and the decomposition time is 20h, to obtain ultrafine high-purity aluminum hydroxide D4, which is subjected to chemical analysis and the particle size is detected by a sedimentation particle size analyzer.

[0041] Example 5: The difference from Example 1 is that the amount of inducer added in step (4) is 2%, the temperature is 80°C, and the decomposition time is 8h, to obtain ultrafine high-purity aluminum hydroxide D5, which is subjected to chemical analysis and the particle size is detected by a sedimentation particle size analyzer.

[0042] Example 6: Based on Example 1, the ultrafine high-purity aluminum hydroxide D1 prepared in Example 1 was slurried with high-purity water and formulated according to a solid content of 200 g / L. The mixture was added to a magnetic stirring high-pressure reactor and heated to 200°C. The mixture was kept warm for 1 hour and then cooled and discharged. The high-purity boehmite E1 was obtained by separation and washing, and analyzed by ICP.

[0043] Example 7: Different from Example 6, the ingredients are prepared according to a solid content of 150 g / L, the temperature is 160° C., and the holding time is 3 h to obtain high-purity boehmite E2, which is detected and analyzed by ICP.

[0044] Example 8: Different from Example 6, the ingredients are prepared according to a solid content of 250 g / L, the temperature is 220° C., and the holding time is 0.5 h to obtain high-purity boehmite E3, which is detected and analyzed by ICP.

[0045] Example 9: Based on Example 6, high-purity boehmite E1 was low-temperature calcined to 600°C, cooled, ground and depolymerized, and then re-loaded into a sagger for calcination. The calcination temperature was slowly increased (2.5°C / min) before 900°C, and then rapidly increased (6°C / min) from 900 to 1250°C, kept warm for 180 minutes, cooled to room temperature, ground and depolymerized to obtain ultrafine high-purity alumina, which was analyzed by ICP and subjected to SEM examination.

[0046] Comparative Example 1: Different from Example 1, the seed solution A1 is directly added to the sodium aluminate solution B3 for decomposition, and ultrafine high-purity aluminum hydroxide D6 is obtained after separation and washing, and chemical analysis is performed. The particle size is detected by sedimentation particle size analyzer.

[0047] Comparative Example 2: Different from Example 1, in step (1), aluminum hydroxide (Al2O3 content of 0.1%) is selected as the seed crystal raw material, and ultrafine high-purity aluminum hydroxide D7 is obtained after separation and washing, and chemical analysis is performed, and the particle size is detected by sedimentation particle size analyzer.

[0048] Comparative Example 3: Different from Example 1, in step (1), aluminum hydroxide (Al2O3 content of 10%) is used as the seed crystal raw material, and ultrafine high-purity aluminum hydroxide D8 is obtained after separation and washing, and chemical analysis is performed, and the particle size is detected by sedimentation particle size analyzer.

[0049] Comparative Example 4: The difference from Example 1 is that in step (4), the inducer is added according to 5% of the Al2O3 content of the sodium aluminate solution, and ultrafine high-purity aluminum hydroxide D9 is obtained after separation and washing, and chemical analysis is performed, and the particle size is detected by sedimentation particle size analyzer.

[0050] Table 1 Particle size analysis of ultrafine high-purity aluminum hydroxide (μm)

[0051]

[0052] Table 2 Purity analysis of ultrafine high purity aluminum hydroxide

[0053]

[0054] Table 3 Particle size purity analysis of high purity boehmite

[0055]

[0056] Table 4 Purity analysis of ultrafine high purity alumina

[0057]

[0058] From the data analysis of Examples 1-3 in Tables 1 and 2, it can be seen that the aluminum hydroxide corresponding to different decomposition seeds and different processes has different primary particles and aggregation states due to the differences in the morphology and structure of the precipitated aluminum hydroxide, and the particle size and seed activity of the ground seeds are also different. When the seed raw material is selected from high-purity pseudo-boehmite produced by the alcohol aluminum method, the seed addition amount is 1%, the decomposition temperature is 50°C, and the decomposition time is 16 hours, the particle size of the ultrafine high-purity aluminum hydroxide obtained in Example 1 is the smallest, and the content of various impurities is the lowest.

[0059] From the data analysis of Examples 1, 4, and 5 in Tables 1 and 2, it can be seen that when the amount of inducer added is in the range of 0.5 to 2.0%, the induced decomposition temperature in Example 1 is 45°C, the decomposition time is 24 hours, and the seed addition amount is 1%, the particle size of the obtained ultrafine high-purity aluminum hydroxide is the smallest and the content of various impurities is the lowest.

[0060] Analysis of the data from Examples 6, 7, and 8 in Table 2 reveals that hydrothermal reactions conducted under varying conditions of temperature, solid content, and duration achieve lattice rearrangement and improved product purity, with process conditions being crucial. The highest purity of high-purity boehmite E1 was obtained in Example 6 when the ultrafine, high-purity aluminum hydroxide solids content was 200 g / L, the temperature was 200°C, and the reaction was incubated for 1 hour.

[0061] like Figure 1 and Figure 2 As shown, from the data analysis of Example 9 in Table 4, it is known that the obtained ultrafine high-purity alumina has a particle size distribution of 0.1 to 0.5 μm, a purity of 99.99%, and excellent performance.

[0062] From the data analysis of Example 1 and Comparative Example 1, it can be seen that when the seed crystals are directly added to the sodium aluminate solution without decomposition of the inducer, a large amount of explosive nucleation is easily caused, and the particles are obviously agglomerated. The particle size of the ultrafine high-purity aluminum hydroxide D6 obtained in Comparative Example 1 is much larger than that obtained in Example 1, and the content of various impurities is also much larger. It can be seen that the scheme of first synthesizing the inducer with seed crystals and then adding the inducer to the sodium aluminate solution has a very good effect.

[0063] From the data analysis of Example 1, Example 2, Example 3 and Comparative Example 2 and Comparative Example 3, it is known that: when aluminum hydroxide (Al2O3 content of 0.1% and 10%) is selected as the seed crystal raw material, the amount of seed crystals is too small, resulting in obvious agglomeration and very easy generation of large particles, while the amount of seed crystals is too high, the amount of ultrafine particles is too large, local agglomeration is easy to occur, and the slurry is relatively viscous, which is not conducive to the transportation of the slurry. The particle size of the ultrafine high-purity aluminum hydroxide D7 and D8 obtained in Comparative Examples 2 and 3 is much larger than that obtained in Example 1, and the content of various impurities is also much larger. It can be seen that when the Al2O3 content of the aluminum hydroxide seed crystals is 0.5-5%, the performance of the ultrafine high-purity aluminum hydroxide obtained is the best.

[0064] From the data analysis of Examples 1, 4, 5 and Comparative Example 4, it can be seen that when the inducer is added at 5% of the Al2O3 content of the sodium aluminate solution, the particle size of the ultrafine high-purity aluminum hydroxide D9 obtained is compared with the aluminum hydroxide obtained in Examples 1, 4, and 5. The aluminum hydroxide in Comparative Example 4 is viscous, has poor filtration performance, is difficult to wash, and has a much higher content of various impurities. It can be seen that when the Al2O3 content of the aluminum hydroxide seed crystal is 0.5-2%, the performance of the ultrafine high-purity aluminum hydroxide obtained is the best.

[0065] The various embodiments in this specification are described in a progressive manner. Similar parts between the various embodiments can be referred to in conjunction with each other. Each embodiment focuses on the differences between the other embodiments. In particular, the system embodiments are generally similar to the method embodiments, so the description is relatively simple. For relevant parts, refer to the description of the method embodiments.

[0066] The foregoing is merely an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should all be included within the scope of the claims of the present application.

Claims

1. A method for preparing ultrafine high-purity aluminum hydroxide, characterized in that: The steps include: (1) Seed solution preparation: High-purity pseudo-boehmite produced by the alcohol aluminum process was mixed with water, ground, and filtered through a membrane to remove large particles to obtain seed solution A1; (2) Preparation of high-purity sodium aluminate solution: Using high-purity aluminum hydroxide from the modified Bayer process as raw material, sodium aluminate solution was prepared by high-temperature dissolution using an ion-exchange membrane alkali solution, and the ratio was adjusted to αk (Na2O / Al2O3 molar ratio) = 1.3-1.

8. The sodium aluminate solution was purified and refined to obtain a high-purity sodium aluminate solution B1; (3) Prepare high-purity sodium aluminate solution B1 with Al2O3 content of 70 g / L to obtain sodium aluminate solution B2. Add seed solution A1 to the prepared sodium aluminate solution B2 at a solid content of 1% of the Al2O3 content of the solution. Control the temperature at 50°C and decompose under high-speed stirring for 16 hours to obtain inducer C1. (4) High-purity sodium aluminate solution B1 was prepared, Al2O3: 100g / L, to obtain sodium aluminate solution B3, and inducer C1 was slowly added to the prepared sodium aluminate solution B3, with the solid content being 1.5% of the Al2O3 content of the solution. The temperature was controlled at 45°C, and the solution was decomposed for 24 hours under high-speed stirring conditions. Ultrafine high-purity aluminum hydroxide was obtained after separation and washing.

2. The preparation method according to claim 1, characterized in that The Al2O3 content in the seed solution A1 is 0.5-5%.

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