Preparation method of aluminum hydroxide with high α-Al2O3 content, aluminum hydroxide with high α-Al2O3 content and application thereof

Abstract

A preparation method of aluminum hydroxide with a high α-Al2O3 content, the aluminum hydroxide with a high α-Al2O3 content and its application, including adding α-Al2O3 seeds to a sodium aluminate solution, and inducing the precipitation and decomposition of aluminum hydroxide by the seeds, and separating and washing to obtain aluminum hydroxide with a high α-Al2O3 content. In this application, α-Al2O3 with different processing performances produced by different processes is selected as the raw material, and a series of products of ultrafine α-Al2O3 powder with high activity and narrow distribution can be prepared through grinding and sorting. Through the parameter regulation of the seed-induced decomposition process, a series of products with different particle sizes and crystal morphologies can be produced. The content of α-Al2O3 in the aluminum hydroxide product prepared in this application is 1-15%, and it can be regulated, providing high-quality raw materials for soft polishing and fine polishing, and can be applied to fields such as refractory materials, electronic ceramics, grinding and polishing materials, and catalyst carriers.

Description

Technical Field

[0001] This application belongs to the technical field of multi-variety alumina, and specifically relates to a preparation method of aluminum hydroxide with a high α-Al2O3 content, aluminum hydroxide with a high α-Al2O3 content, and its applications. Background Art

[0002] Multi-variety alumina, also known as special alumina or chemical alumina, is the deep processing of industrial alumina, accounting for 6%-8% of the total alumina. Among them, special aluminum hydroxide has the largest proportion in multi-variety alumina. Due to differences in its chemical purity, crystal structure, specific surface area, pore structure, particle size, hardness, sintering degree, etc., the properties of aluminum hydroxide vary greatly, resulting in significant differences in application performance. It is widely used in fields such as chemistry, medicine, catalysts, rubber, plastics, papermaking, fillers, pigments, etc. The technical content of special aluminum hydroxide is relatively high, and its product added value is also relatively high. With the development of science and technology and the application of new materials, the market for multi-variety alumina is becoming increasingly broad.

[0003] Currently, there are many production methods for aluminum hydroxide. The Bayer process accounts for more than 95% of the total scale, followed by the sintering process, the modified Bayer process, etc. There are also other methods such as the alcohol-aluminum method, the neutralization method, the metal-aluminum hydrolysis method, the choline method, the hydrochloric acid method, etc. Different processes determine different application capabilities of the products, and there are also significant differences in the purity, particle size, morphology, crystal form, etc. of the products. The crystal forms of aluminum hydroxide mainly include: α-gibbsite, bayerite, nordstrandite, boehmite, pseudo-boehmite, etc. There are also many studies and patents on the crystal form of aluminum hydroxide.

[0004] CN106315641A discloses a preparation method of aluminum hydroxide, including the steps of: (1) preparing a sodium aluminate solution; (2) heating the sodium aluminate solution to the initial decomposition temperature of 75°C, adding seeds and stirring for decomposition, cooling during the stirring process until the cooling ends at 55°C, with a cooling time of 8h, and finally obtaining the target product through filtration. Under the process conditions of the present invention, aluminum hydroxide micropowder with a good particle size distribution and good crystal crystallization can be obtained.

[0005] CN109721088A discloses a kind of aluminum hydroxide and its preparation method. The reaction system adopted in the preparation method of the aluminum hydroxide includes N microreactors connected in series. The first microreactor adopts an impinging stream reactor. Acidic materials and alkaline materials enter the first microreactor for co-current reaction. The obtained product enters the second microreactor to the (N - 1)th microreactor in sequence, and undergoes repeated pH swings. When swinging to the alkaline side, the reaction temperature is 20 - 30 °C lower than that of the first microreactor; when swinging to the acidic side, the reaction temperature is 20 - 30 °C higher than that of the first microreactor. The obtained reaction product mixture enters the Nth microreactor for aging reaction, and then through post-treatment, aluminum hydroxide is obtained. The aluminum hydroxide prepared by this method has high crystallinity, uniform grain size distribution, eliminates the scale-up effect, and the alumina obtained after calcination has uniform pore size distribution, large pore volume and specific surface area, and is very suitable for the preparation of mesoporous hydrotreating catalysts such as residue hydrodesulfurization and denitrification catalysts.

[0006] CN100462304C discloses a preparation method for controlling the crystal grains of aluminum hydroxide, which includes simultaneously injecting aqueous solutions of sodium aluminate (NaAlO2) and aluminum sulfate (Al2(SO4)3) into a high gravity field reactor for liquid-phase chemical reaction, collecting the obtained reaction product slurry, adjusting the pH value and temperature of the slurry to form aluminum hydroxide crystal grains with a predetermined crystal form, such as bayerite, boehmite or pseudo-boehmite crystal form.

[0007] CN109553121A discloses a preparation method for high-purity low-sodium aluminum hydroxide, including: dissolving industrial aluminum hydroxide in sodium hydroxide to obtain a sodium aluminate solution, obtaining a high-purity sodium aluminate solution through purification, adding active seeds for decomposition, and then by adjusting various process parameters such as the concentration of each component of the original decomposition sodium aluminate solution, solution temperature, CO2 ventilation rate, carbonation decomposition end point, etc., performing carbonation decomposition on the sodium aluminate solution to realize the production of high-purity low-sodium aluminum hydroxide, where the active seeds are aluminum hydroxide, amorphous Al(OH)3, pseudo-boehmite, γ-Al2O3, ultrafine SiO2 or ultrafine CaO.

[0008] CN109052442B discloses a production method for electronic-grade high heat-resistant aluminum hydroxide, including S1: after redissolving aluminum hydroxide with liquid caustic soda, diluting with water, adding a decontaminant to remove impurity elements, and obtaining a sodium aluminate solution through fine filtration, and diluting with water to obtain an electronic-grade aluminum hydroxide decomposition stock solution; S2: preparing seeds by sand grinding method;

[0009] S3: the decomposition stock solution is subjected to fine filtration again, and then the seeds are added for decomposition; S4: after the decomposed slurry separates the mother liquor, it is washed and dried to obtain aluminum hydroxide micropowder.

[0010] In the prior art, the alumina crystal phase obtained by producing alumina from aluminum hydroxide is uneven, and the particle size is uncontrollable. Therefore, in order to obtain alumina with a uniform crystal phase and a controllable particle size, it is urgent to prepare a kind of aluminum hydroxide that can inhibit uncontrollable nucleation and reduce the sintering temperature during the subsequent calcination process of preparing alumina. Summary of the Invention

[0011] In order to solve the above problems, the present application proposes a preparation method of aluminum hydroxide with a high α-Al2O3 content, the aluminum hydroxide with a high α-Al2O3 content, and its application.

[0012] A preparation method of aluminum hydroxide with a high α-Al2O3 content includes the following steps: adding α-Al2O3 seeds to a sodium aluminate solution, inducing the decomposition of the seeds to precipitate aluminum hydroxide, and separating and washing to obtain aluminum hydroxide with a high α-Al2O3 content.

[0013] Preferably, the temperature of the seed-induced decomposition is 55-75°C, and the time is 20-45h.

[0014] Preferably, the seed addition amount is 1-10% of the Al2O3 content of sodium aluminate.

[0015] Preferably, the preparation method of the α-Al2O3 seeds is: selecting the raw material α-Al2O3, mixing it with water, and grinding to obtain an α-Al2O3 seed slurry.

[0016] Preferably, the raw material α-Al2O3 is selected from α-Al2O3 produced by calcined α-Al2O3, ultrafine α-Al2O3, ammonium aluminum sulfate method, ammonium aluminum carbonate method, modified Bayer method, sol-gel method, gas-phase method or hydrochloric acid method process;

[0017] Preferably, the raw material α-Al2O3 is selected from alumina produced by the ammonium aluminum carbonate method.

[0018] Preferably, the parameters of the sodium aluminate solution are Nt: 130-180 g / L, Al2O3: 120-190 g / L.

[0019] Preferably, the process of preparing the sodium aluminate solution by the liquid caustic soda redissolution technology is: selecting an aluminum hydroxide raw material and adding it to an ion-exchange membrane caustic soda solution, adjusting it according to αk: 1.3-1.8, raising the temperature to 110-160°C for a dissolution reaction, and filtering and refining to obtain a sodium aluminate solution.

[0020] Preferably, the aluminum hydroxide raw material is selected from Bayer process aluminum hydroxide, sintering process aluminum hydroxide, modified Bayer process aluminum hydroxide, neutralization process aluminum hydroxide, carbonation process aluminum hydroxide, alcohol-aluminum process aluminum hydroxide, choline process aluminum hydroxide, or hydrolysis process aluminum hydroxide;

[0021] Preferably, the aluminum hydroxide raw material is selected from modified Bayer process aluminum hydroxide.

[0022] The aluminum hydroxide with a high α-Al2O3 content prepared by any of the above preparation methods has parameters of α-Al2O3 content of 1-15% and particle size D 50 : 5-90 μm.

[0023] The aluminum hydroxide with a high α-Al2O3 content prepared by any of the above preparation methods is applied to fields such as refractory materials, electronic ceramics, grinding and polishing materials, and catalyst carriers.

[0024] As is well known, α-Al2O3 has a low specific surface area and is inert to high temperatures, but it does not belong to activated alumina and has almost no catalytic activity. It is generally considered that α-Al2O3 cannot be used as a seed crystal. However, in the decomposition process of the solution state in this application, α-Al2O3 seed crystals are added, so that during the precipitation process of aluminum hydroxide, the precipitation of aluminum hydroxide and the very good homogeneous dispersion of α-Al2O3 are realized, and the sintering temperature during the subsequent production of alumina can be reduced.

[0025] The key point of this application is first the preparation of ultrafine α-Al2O3 seed crystals. By selecting raw materials and grinding, the seed crystals are prepared, and then the seed crystal slurry is added to the adjusted sodium aluminate solution according to a certain ratio, and the decomposition conditions are controlled, mainly temperature, time, seed crystal addition amount, etc., to realize the control of nucleation, growth, crystal morphology, and particle size during the decomposition process of aluminum hydroxide, achieve the purpose of preparing aluminum hydroxide with a high α-Al2O3 content, realize the preposition of α-Al2O3 seed crystals and have the effect of uniform dispersion, which is beneficial to low-temperature calcination and grain control during the subsequent calcination process, can realize low-temperature calcination of alumina and polishing performance, etc., can promote the high-quality development of high-temperature alumina, has very good application prospects, and can be widely applied to fields such as refractory materials, electronic ceramics, grinding and polishing materials, and catalyst carriers.

[0026] This application can bring the following beneficial effects:

[0027] 1. In this application, α-Al2O3 with different processing performances produced by different processes is selected as the raw material, and a series of powder products of α-Al2O3 can be prepared through grinding and sorting.

[0028] 2. Through the parameter control of the seed-induced decomposition process in this application, a series of products with different particle sizes and crystal morphologies can be produced.

[0029] 3. The content of α-Al2O3 in the aluminum hydroxide product is high, and the seed crystals are evenly distributed, which is beneficial to realizing low-temperature phase transformation and crystal grain size control during the calcination process, and can realize the production of low-temperature and small-grain α-Al2O3;

[0030] 4. The content of α-Al2O3 in the aluminum hydroxide product is 1-15%, and it can be regulated, providing high-quality raw materials for soft polishing and fine polishing.

[0031] 5. When preparing alumina from the aluminum hydroxide with a high α-Al2O3 content prepared by this application, the sintering temperature is 100-200°C lower than that of the prior art. Detailed implementation manners

[0032] Example 1: (1) Select Japanese Daming Chemical TM-DR alumina (i.e., alumina produced by the ammonium aluminum carbonate method) as the seed crystal of α-Al2O3, add high-purity water, make a slurry according to the ratio of material to water of 1:3, grind at 2000 r / min for 120 min, and filter to obtain the α-Al2O3 seed crystal slurry;

[0033] (2) Select modified Bayer process aluminum hydroxide, add it to the ion-exchange membrane caustic solution, adjust according to αk: 1.4, raise the temperature to 130°C for the digestion reaction, filter and refine to obtain sodium aluminate solution, Nt: 155 g / L, Al2O3: 170 g / L;

[0034] (3) Adjust the temperature of the sodium aluminate solution, the initial temperature is 65°C, add the prepared seed crystal, the addition amount of the solid content of the seed crystal is 1% of the Al2O3 content of the sodium aluminate, the final temperature is 55°C, the decomposition time is 40 h, filter, wash multiple times until the pH of the washing liquid = 7 to end the washing, and obtain the aluminum hydroxide product with a high α-Al2O3 content. After chemical analysis and particle size analyzer detection, the decomposition rate is 36.5%, the content of α-Al2O3 is 3.9%, and the particle size D 50 : 80.2 μm. Example 2: Different from Example 1 in that the addition amount of the seed crystal is 2%, and the aluminum hydroxide product with a high α-Al2O3 content is obtained. After chemical analysis and particle size analyzer detection, the decomposition rate is 42.3%, the content of α-Al2O3 is 4.2%, and the particle size D 50 : 65.4 μm.

[0035] Example 3: Different from Example 1 in that the addition amount of the seed crystal is 3%, and the aluminum hydroxide product with a high α-Al2O3 content is obtained. After chemical analysis and particle size analyzer detection, the decomposition rate is 45.2%, the content of α-Al2O3 is 6.0%, and the particle size D 50 : 56.8 μm.

[0036] Example 4: Different from Example 1 in that the addition amount of the seed crystal is 4%, and the aluminum hydroxide product with a high α-Al2O3 content is obtained. After chemical analysis and particle size analyzer detection, the decomposition rate is 47.1%, the content of α-Al2O3 is 7.1%, and the particle size D 50 : 50.3 μm.

[0037] Example 5: Different from Example 1, the seed addition amount is 8%, and an aluminum hydroxide product with high α-Al2O3 is obtained. After chemical analysis and detection by a particle size analyzer, the decomposition rate is 51.1%, the content of α-Al2O3 is 10.4%, and the particle size D 50 : 26.2 μm.

[0038] Example 6: Different from Example 1, the seed addition amount is 10%, and an aluminum hydroxide product with high α-Al2O3 is obtained. After chemical analysis and detection by a particle size analyzer, the decomposition rate is 51.1%, the content of α-Al2O3 is 10.4%, and the particle size D 50 : 26.2 μm.

[0039] Example 7: Different from Example 2, the initial decomposition temperature is 55 °C and the final decomposition temperature is 50 °C, and an aluminum hydroxide product with high α-Al2O3 is obtained. After chemical analysis and detection by a particle size analyzer, the decomposition rate is 43.7%, the content of α-Al2O3 is 4.3%, and the particle size D 50 : 23.8 μm.

[0040] Example 8: Different from Example 2, the initial decomposition temperature is 75 °C and the final decomposition temperature is 55 °C, and an aluminum hydroxide product with high α-Al2O3 is obtained. After chemical analysis and detection by a particle size analyzer, the decomposition rate is 38.4%, the content of α-Al2O3 is 4.2%, and the particle size D 50 : 66.3 μm.

[0041] Example 9: (1) Select ultrafine α-Al2O3 (0.8 μm) as the seed of α-Al2O3, add high-purity water, make a slurry according to the material: water ratio of 1:3, grind for 120 min at 2000 r / min, and filter to obtain the α-Al2O3 seed slurry; (2) Select Bayer process aluminum hydroxide, add it to the ion-exchange membrane caustic solution, adjust it according to αk: 1.3, raise the temperature to 110 °C for digestion reaction, filter and refine to obtain sodium aluminate solution, Nt: 130 g / L, Al2O3: 165 g / L; (3) Adjust the temperature of the sodium aluminate solution, the initial temperature is 65 °C, add the prepared seed, the seed addition amount is 2% of the Al2O3 content of sodium aluminate, the final temperature is 55 °C, the decomposition time is 20 h, filter, wash multiple times until the pH of the washing liquid = 7 to end the washing, and obtain an aluminum hydroxide product with high α-Al2O3. After chemical analysis and detection by a particle size analyzer, the decomposition rate is 18.6%, the content of α-Al2O3 is 5.3%, and the particle size D 50 : 69.8 μm.

[0042] Example 10: (1) Select α-Al2O3 produced by the ammonium aluminum sulfate method as the seed of α-Al2O3, add high-purity water, make a slurry according to the material: water ratio of 1:3, grind for 120 min at 2000 r / min, and filter to obtain the α-Al2O3 seed slurry;

[0043] (2) Select sintered aluminum hydroxide, add it to the ion-exchange membrane caustic solution, adjust it according to αk: 1.8, raise the temperature to 160 °C for digestion reaction, filter and refine to obtain sodium aluminate solution, Nt: 180 g / L, Al2O3: 165 g / L;

[0044] (3) Adjust the temperature of the sodium aluminate solution, the initial temperature is 65 °C, add the prepared seed crystals, the addition amount of the seed crystals is 2% of the Al2O3 content of sodium aluminate, the final temperature is 55 °C, the decomposition time is 45 h, filter, wash repeatedly until the pH of the washing liquid = 7 to end the washing, and obtain aluminum hydroxide products with high α-Al2O3. After chemical analysis and particle size analyzer detection, the decomposition rate is 34%, the content of α-Al2O3 is 5.8%, and the particle size D 50 : 32 μm.

[0045] Comparative Example 1: Different from Example 4, select commercially available aluminum hydroxide as the raw material, make pulp according to the ratio of material to water of 1:3, grind at 2000 r / min for 120 min, filter to obtain aluminum hydroxide seed crystal slurry, decompose to obtain aluminum hydroxide products, and after chemical analysis and particle size analyzer detection, the decomposition rate is 58%, the content of α-Al2O3 is 0%, and the particle size D 50 : 2.4 μm.

[0046] Comparative Example 2: Different from Example 4, select commercially available γ-Al2O3 as the raw material, make pulp according to the ratio of material to water of 1:3, grind at 2000 r / min for 120 min, filter to obtain γ-Al2O3 seed crystal slurry, decompose to obtain aluminum hydroxide products, and after chemical analysis and particle size analyzer detection, the decomposition rate is 22%, the content of α-Al2O3 is 0%, and the particle size D 50 : 28 μm.

[0047] In all examples and comparative examples of this application, the detection of the content of α-Al2O3 is quantitatively analyzed according to the "Determination of the content of α-Al2O3 in calcined α-aluminum oxide by X-ray diffraction method"; the calculation method of the decomposition rate is as follows: decomposition rate = (1 - αk (初始) / αk (终点) ) × 100%, where: αk (初始) is the αk value of the initial sodium aluminate solution for decomposition; αk (终点) is the αk value of the sodium aluminate solution at the end of decomposition.

[0048] Table 1

[0049]

[0050]

[0051] Data analysis of Examples 1-6 shows that: the more the amount of seed crystals added, the higher the content of α-Al2O3 in the precipitated aluminum hydroxide, and the higher the decomposition rate. However, the particle size of the aluminum hydroxide gradually decreases. The finer the particle size, the more difficult it is to wash the product. Considering the particle size of the product and the analysis of its α-Al2O3 content, when the seed crystal addition amount is 4% in Example 4, the performance of the obtained aluminum hydroxide product is the best.

[0052] Data analysis of Examples 2, 7, and 8 shows that: as the temperature increases, the decomposition rate gradually decreases. When the temperature is 55°C, the particle size is too small and it is difficult to wash the subsequent product. Considering the analysis of the decomposition rate and particle size, the optimal initial temperature for the decomposition process is 65°C and the final temperature is 55°C.

[0053] Data analysis of Examples 2, 9, and 10 shows that: comparing the data of the decomposition experiments of α-Al2O3 seed crystals by ammonium aluminum carbonate method, α-Al2O3 seed crystals by ammonium aluminum sulfate method, and ultrafine α-Al2O3 seed crystals, the decomposition rate indexes of ultrafine α-Al2O3 seed crystals and ammonium aluminum sulfate method seed crystals are not as good as those of the ammonium aluminum carbonate method. Therefore, the optimal choice of the seed crystal raw material is alumina produced by the ammonium aluminum carbonate method.

[0054] Data analysis of Comparative Example 1 and Example 4 shows that: when the selected seed crystal raw material is commercially available aluminum hydroxide, the α-Al2O3 content of the obtained aluminum hydroxide product is 0, and the particle size D 50 : 2.4um, and the particle size is very fine and difficult to wash.

[0055] Data analysis of Comparative Example 2 and Example 4 shows that: when the commercially available γ-Al2O3 purchased on the market is selected as the raw material, the α-Al2O3 content of the obtained aluminum hydroxide product is 0, and the decomposition rate is only 22%, which is far lower than the decomposition rate when alumina produced by the ammonium aluminum carbonate method is selected.

[0056] Each embodiment in this specification is described in a progressive manner. For the same or similar parts among the embodiments, reference can be made to each other. Each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can refer to the partial description of the method embodiment.

[0057] The above are only the embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the scope of the claims of the present application.

Claims

1. A preparation method of aluminum hydroxide with a high α-Al2O3 content, characterized in that, It includes the following steps: adding α-Al2O3 seeds into the sodium aluminate solution, inducing the decomposition of the seeds to precipitate aluminum hydroxide, and separating and washing to obtain aluminum hydroxide with a high α-Al2O3 content; The initial temperature of the decomposition induced by the seeds is 65 °C, the final temperature of the decomposition is 55 °C, and the time is 20 - 45 h; The addition amount of the seeds is 1 - 10% of the Al2O3 content of the sodium aluminate; The raw material of the α-Al2O3 seeds is selected from alumina produced by the ammonium aluminum carbonate method; The obtained aluminum hydroxide has the following parameters: the content of α-Al2O3 is 1-15%, and the particle size D 50 : 5-90 microns.

2. The preparation method according to claim 1, characterized in that, The preparation method of the α-Al2O3 seeds is: selecting the raw material α-Al2O3, grinding, and mixing with water to obtain the α-Al2O3 seed slurry.

3. The preparation method according to claim 1, wherein The parameter of the sodium aluminate solution is Nt: 130 - 180 g / L.

4. Aluminum hydroxide with a high α-Al2O3 content prepared by any of the preparation methods according to claims 1 - 3 is applied to the fields of refractory materials, electronic ceramics, grinding and polishing materials, and catalyst carriers.

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