Nano aluminum hydroxide seed crystal as well as preparation method and application thereof

Abstract

The invention provides a nano aluminum hydroxide seed crystal as well as a preparation method and application thereof, and belongs to the field of fine aluminum oxide. The method comprises the following steps: mixing an aluminum sulfate solution with a first sodium aluminate solution for neutralization reaction to obtain a superfine aluminum hydroxide seed crystal inducer; the superfine aluminum hydroxide seed crystal inducer is a gelatinous material; performing a seed crystal decomposition reaction on the superfine aluminum hydroxide seed crystal inducer and a second sodium aluminate solution to obtain a nano aluminum hydroxide seed crystal; the temperature of the seed decomposition reaction is less than or equal to 60 DEG C. The superfine aluminum hydroxide seed crystal inducer containing a large number of gelatinous materials is prepared through the neutralization reaction of the aluminum sulfate solution and the sodium aluminate solution, the superfine aluminum hydroxide seed crystal inducer can be rapidly dissolved after being added into the sodium aluminate solution, so that the caustic ratio of the solution is reduced, a large number of superfine aluminum hydroxide crystal nucleuses are generated in the solution in an instant explosion mode, and the gel-like materials are obtained. And the crystal nucleus is fine in particle size, uniform in distribution and high in activity, so that the aluminum hydroxide seed crystal with relatively high activity and relatively fine particle size is obtained.

Description

Technical Field

[0001] The present application relates to the technical field of fine aluminum oxide preparation, and in particular to a nano aluminum hydroxide seed crystal, a preparation method thereof, and an application thereof. Background Art

[0002] Ultrafine aluminum hydroxide has the characteristics of small particle size, large specific surface area and good thermal stability. It is widely used in the fields of flame retardant for wires and cables, flame retardant for silicone rubber and coatings. It is also the raw material for preparing ultrafine alumina. At present, ultrafine aluminum hydroxide is generally prepared by mechanical grinding and seed separation. Since the ultrafine aluminum hydroxide prepared by mechanical grinding has an uneven particle size distribution and contains large particles, the performance of these aluminum hydroxides is poor. The particle size and distribution of ultrafine aluminum hydroxide prepared by seed separation can be controlled, and the performance is better. It is the main preparation method of ultrafine aluminum hydroxide at present, and seed crystal preparation is one of the key processes in the production of ultrafine aluminum hydroxide by seed separation.

[0003] The current preparation technologies for ultrafine aluminum hydroxide seed crystals are as follows: (1) Aluminum hydroxide micropowder is obtained by reacting nitric acid with sodium aluminate. The micropowder is converted into highly active monodisperse aluminum hydroxide seed crystals by grinding, crushing and acid depolymerization. The seed crystal particle size D50 is 0.3μm to 0.5μm and is used in the process of preparing aluminum hydroxide from nitric acid. (2) Seed crystals are prepared by mixing concentrated metaaluminate saturated solution with process water for crystallization. The preparation process takes 12 to 120 hours, and the particle size D50 of the final ultrafine aluminum hydroxide seed crystal product is 1μm to 2μm. (3) Seed crystals are prepared by sand milling. The seed crystal particle size D50 is 0.4μm to 3μm. The seed crystals are added to the desiliconized and purified sodium aluminate solution to decompose it to obtain ultrafine aluminum hydroxide. The sand milling process for preparing seed crystals is time-consuming and has low production capacity. (4) Alumina hydrate is mixed with aluminate solution and decomposed to produce ultrafine aluminum hydroxide seeds with a seed particle size D50 of 0.1μm to 0.6μm. Alumina hydrate needs to be slurried and ball-milled with water, which is a complex process and has high energy consumption. (5) The Bayer process or sintering process sodium aluminate refined liquid is carbonated and decomposed in a carbon separation tank to form a gel-like aluminum hydroxide gel slurry as a seed crystal. The final product has an average particle size of 1 to 2μm. However, the average particle size of the ultrafine aluminum hydroxide seeds obtained by the above preparation method is greater than 0.1μm. When the seeds are added to the sodium aluminate solution to prepare ultrafine aluminum hydroxide, the product particle size D50 is above 0.5μm, and the particle size distribution is not concentrated, with large particles. This makes the ultrafine aluminum hydroxide product difficult to be applied in some specific fields. Summary of the Invention

[0004] The present application provides a nano-aluminum hydroxide seed crystal, a preparation method thereof, and an application thereof, in order to solve the technical problems of coarse particle size and poor activity of ultrafine aluminum hydroxide seed crystals in the prior art.

[0005] In a first aspect, an embodiment of the present application provides a method for preparing nano-aluminum hydroxide seed crystals, the method comprising:

[0006] The aluminum sulfate solution and the first sodium aluminate solution are mixed and neutralized to obtain an ultrafine aluminum hydroxide crystal seed inducer; the ultrafine aluminum hydroxide crystal seed inducer is a gel-like material;

[0007] The ultrafine aluminum hydroxide seed crystal inducer and the second sodium aluminate solution are subjected to a seed decomposition reaction to obtain nano aluminum hydroxide seed crystals; the temperature of the seed decomposition reaction is ≤60°C.

[0008] Optionally, the temperature of the neutralization reaction is 15° C. to 45° C., and the pH value at the reaction endpoint of the neutralization reaction is 7.0 to 8.0.

[0009] Optionally, the temperature of the seed crystal decomposition reaction is 40° C. to 60° C., and the time of the seed crystal decomposition reaction is 2.0 h to 3.0 h.

[0010] Optionally, in the aluminum sulfate solution, the content of aluminum oxide is 4% to 10%, and the content of sulfate ion is 11% to 28%.

[0011] Optionally, the mass m1 of the ultrafine aluminum hydroxide crystal seed inducer and the mass m2 of the aluminum oxide in the second sodium aluminate solution satisfy the relationship: m1:m2=(35-45):100.

[0012] Optionally, the caustic ratio of the first sodium aluminate solution is 1.30 to 1.60, and the mass concentration of aluminum oxide in the first sodium aluminate solution is 25 g / L to 45 g / L; and / or

[0013] The caustic ratio of the second sodium aluminate solution is 1.40-1.60, and the mass concentration of aluminum oxide in the second sodium aluminate solution is 100 g / L-150 g / L.

[0014] In a second aspect, an embodiment of the present application provides a nano-aluminum hydroxide crystal seed prepared by the method described in any one of the embodiments of the first aspect, wherein the average particle size D50 of the nano-aluminum hydroxide crystal seed does not exceed 0.1 μm, and the particle size D90 does not exceed 0.3 μm.

[0015] In a third aspect, the present application provides an application of nano-aluminum hydroxide seed crystals, the application comprising:

[0016] The nano-aluminum hydroxide seeds prepared by the method described in any embodiment of the first aspect are used in the preparation of ultrafine aluminum hydroxide by a seed separation method, wherein the nano-aluminum hydroxide seeds and the sodium aluminate solution raw material undergo a seed separation decomposition reaction to obtain an ultrafine aluminum hydroxide product;

[0017] The caustic ratio of the sodium aluminate solution raw material is 1.40-1.60, and the mass concentration of aluminum oxide in the sodium aluminate solution raw material is 100 g / L-150 g / L.

[0018] Optionally, the temperature of the seed decomposition reaction is 55° C. to 65° C., and the time of the seed decomposition reaction is 6 h to 7 h.

[0019] Optionally, the mass m3 of the ultrafine aluminum hydroxide seed crystals and the mass m4 of the aluminum oxide of the sodium aluminate solution raw material satisfy the relationship: m3:m4=(1-2):100.

[0020] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0021] The present invention provides a method for preparing nano-aluminum hydroxide seed crystals. The method uses a neutralization reaction between an aluminum sulfate solution and a sodium aluminate solution to prepare an ultrafine aluminum hydroxide seed crystal inducer containing a large amount of gel-like material. Because the gel-like material is easily soluble in the sodium aluminate solution and produces a large amount of hydroxyl groups, these hydroxyl groups interact strongly with aluminate ions, which can inhibit the directional growth of aluminum hydroxide crystals and promote homogeneous nucleation rather than heterogeneous growth in the second sodium aluminate solution. This rapidly reduces the caustic ratio of the sodium aluminate solution, increases the seed decomposition reaction rate of the second sodium aluminate solution, and produces a large number of crystal nuclei. In addition, the gel-like material has a high specific surface area and abundant active sites, which can significantly increase the nucleation density of the second sodium aluminate solution during the seed decomposition stage. In addition, the gel-like material can serve as a template to limit the diffusion space of newly formed aluminum hydroxide. Under the action of the seed decomposition reaction temperature of 60°C and below, the faster crystal nucleus growth rate and the higher nucleation density, the gel-like material can make the aluminum hydroxide crystals slowly grow in the nanoscale range, and form aluminum hydroxide seeds with finer particle size and incomplete development, thereby ultimately obtaining aluminum hydroxide seeds with higher activity and finer particle size. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0023] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0024] Figure 1 A schematic flow chart of a method for preparing nano-aluminum hydroxide seed crystals provided in an embodiment of the present application;

[0025] Figure 2 A schematic diagram of the actual process of a method for preparing nano-aluminum hydroxide seed crystals provided in an embodiment of the present application;

[0026] Figure 3 A schematic diagram of the actual process of applying a nano-aluminum hydroxide seed crystal provided in an embodiment of the present application. DETAILED DESCRIPTION

[0027] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0028] The range descriptions described in this article, such as numerical ranges, ratio ranges, etc., include all possible sub-ranges and single numerical values ​​within the range. For example, the range description of "1 to 6" or "1~6" covers all sub-ranges from 1 to 6 (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6). Unless otherwise specified, the terms "including", "comprising", etc. used in this article mean "including but not limited to"; relational terms such as "first" and "second" are only used to distinguish different entities or operations, and do not imply an actual sequence or association relationship; "and / or" means that multiple situations can exist alone or at the same time; expressions such as "at least one", "multiple", and "at least one" refer to any combination of corresponding objects, including a combination of single or multiple objects. The proportional relationships involved in the article, such as mass ratios, molar ratios, etc., should be understood as the corresponding relationship between the first and second terms of the proportional formula in the order of description. The raw materials, reagents, instruments and equipment used in this article can be purchased on the market or prepared by existing methods.

[0029] Figure 1 A schematic flow chart of a method for preparing nano-aluminum hydroxide seed crystals provided in an embodiment of the present application; Figure 2 This is a schematic diagram of the actual process of a method for preparing nano-aluminum hydroxide seeds provided in an embodiment of the present application.

[0030] like Figure 1 and Figure 2 As shown, the embodiment of the present application provides a method for preparing nano-aluminum hydroxide seed crystals, the method comprising:

[0031] S1, mixing the aluminum sulfate solution and the first sodium aluminate solution for neutralization reaction to obtain an ultrafine aluminum hydroxide crystal seed inducer; the ultrafine aluminum hydroxide crystal seed inducer is a gel-like material;

[0032] S2. Performing a seed decomposition reaction on the ultrafine aluminum hydroxide seed crystal inducer and the second sodium aluminate solution to obtain nano aluminum hydroxide seed crystals; the temperature of the seed decomposition reaction is ≤60°C.

[0033] It should be noted that during the neutralization reaction stage, the concentration of the aluminum sulfate solution and the first sodium aluminate solution can be controlled by controlling the concentration of the aluminum sulfate solution, the concentration of the first sodium aluminate solution, the caustic ratio, and the neutralization reaction parameters, so that the gel-like material of the ultrafine aluminum hydroxide seed inducer is uniform and transparent without obvious particles.

[0034] It should be noted that the embodiment of the present application provides a method for preparing nano-aluminum hydroxide seeds, which prepares nano-aluminum hydroxide seeds with fine particle size and high activity through the following multi-stage mechanism.

[0035] The gel-like material of ultrafine aluminum hydroxide inducer dissolves to produce free hydroxyl groups, which react with [Al(OH)4] - Formation of [Al(OH)5] 2- The transition state complex can reduce the nucleation activation energy and greatly improve the nucleation rate of ultrafine aluminum hydroxide seeds. At the same time, a large number of induced ultrafine aluminum hydroxide seeds cannot be fully developed, thereby improving the activity of the ultrafine aluminum hydroxide seeds.

[0036] There will be a large number of nano-scale mesoporous structures in the gel network of the gel-like material. These mesoporous structures will have a steric effect, forcing the ultrafine aluminum hydroxide crystals to grow preferentially along the crystal plane, forming a sheet structure with a thickness at the nanometer level, hindering the normal growth of the ultrafine aluminum hydroxide crystals, causing the ultrafine crystal seeds to develop imperfectly, and further increasing their activity.

[0037] The rapid nucleation reaction rate will lead to incomplete development of ultrafine aluminum hydroxide crystals, resulting in edge dislocations and surface dangling bonds, which will affect the normal development of ultrafine aluminum hydroxide crystals.

[0038] Residual Na in the aluminum hydroxide lattice + Cationic vacancies will be formed, and these cation vacancies will increase the surface energy of aluminum hydroxide crystals.

[0039] In summary, the embodiments of the present application provide a method for preparing nano-aluminum hydroxide seed crystals, which enables the product to have the following characteristics: nano-scale particle size distribution, high active specific surface area and low residual alkali content.

[0040] In some optional embodiments, the temperature of the neutralization reaction is 15° C. to 45° C., and the pH value at the reaction endpoint of the neutralization reaction is 7.0 to 8.0.

[0041] In some optional embodiments, the temperature of the seed crystal decomposition reaction is 40° C. to 60° C., and the time of the seed crystal decomposition reaction is 2.0 h to 3.0 h.

[0042] In these embodiments, the neutralization reaction temperature of 15°C to 45°C and the endpoint pH of the neutralization reaction of 7.0 to 8.0, controlling the specific reaction temperature and endpoint pH of the neutralization reaction, can allow the aluminum sulfate solution and the first sodium aluminate solution to fully undergo a neutralization reaction, prompting the first sodium aluminate solution to be converted into a gel-like material with fine and uniform particles, and these gel-like materials are not easily agglomerated, which is conducive to the seed decomposition reaction involving the ultrafine aluminum hydroxide seed inducer. In addition, the seed decomposition reaction temperature of 40°C to 60°C and the seed decomposition reaction time of 2.0h to 3.0h allow the supersaturation of the second sodium aluminate solution to increase rapidly in a very short period of time, accelerate the decomposition of the second sodium aluminate solution, and increase the number of ultrafine aluminum hydroxide crystal nuclei, prompting the second sodium aluminate solution to form nano-aluminum hydroxide seed crystals with fine and uniform particle size.

[0043] It should be noted that, when the temperature of the seed decomposition reaction is less than 40°C, the excessively low temperature of the seed decomposition reaction will increase the viscosity of the second sodium aluminate solution, and the second sodium aluminate solution with a larger viscosity will prevent the ultrafine aluminum hydroxide seed inducer from being quickly and completely dissolved in the second sodium aluminate solution, and the second sodium aluminate solution will not be able to explosively produce a large number of aluminum hydroxide nuclei; when the temperature of the seed decomposition reaction is greater than 60°C, the ultrafine aluminum hydroxide seed inducer will dissolve rapidly, but at this time the saturation degree of the second sodium aluminate solution is too low, which makes the decomposition rate of the second sodium aluminate solution slower, resulting in a smaller number of aluminum hydroxide nuclei generated by the second sodium aluminate solution, and ultimately leads to a larger particle size of the ultrafine aluminum hydroxide crystals.

[0044] The temperature of the neutralization reaction can be 15°C, 16°C, 20°C, 25°C, 30°C, 35°C, 40°C, or 45°C.

[0045] The endpoint pH of the neutralization reaction may be 6.5, 6.6, 6.7, 7.0, 7.5 or 8.0.

[0046] The temperature of the seed decomposition reaction can be 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 50°C, 55°C or 60°C.

[0047] The time for decomposition of the seed crystals can be 2.0 h, 2.1 h, 2.2 h, 2.3 h, 2.4 h, 2.5 h, 2.6 h, 2.7 h, 2.8 h, 2.9 h or 3.0 h.

[0048] In some optional embodiments, in the aluminum sulfate solution, the content of aluminum oxide is 4% to 10%, and the content of sulfate ion is 11% to 28%.

[0049] It should be noted that aluminum sulfate dissociates into Al 3+ and SO4 2- In industry, the Al2O3 content is often used to indirectly characterize the effective concentration of aluminum. In aluminum sulfate solutions, the aluminum oxide content is 4% to 10% and the sulfate content is 11% to 28%. The "content" here generally refers to the mass percentage concentration of the solute in the solution, that is, the mass ratio of the target component calculated based on the total mass of the solution.

[0050] In these embodiments, when the aluminum oxide content is 4% to 10% and the sulfate content is 11% to 28%, the aluminum sulfate solution and the sodium aluminate solution react to form a uniform and transparent gel-like material. This gel structure, devoid of distinct particles, provides an ideal microscopic environment for the subsequent seed crystal decomposition reaction. It also facilitates precise control of the pH value of the neutralization reaction system, allowing the reaction to proceed within a range conducive to the formation of aluminum hydroxide colloid and avoiding the formation of large particle precipitation.

[0051] In the aluminum sulfate solution, the aluminum oxide content can be 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc., and the sulfate content can be 11%, 12%, 16%, 20%, 24%, 28%, etc.

[0052] In some optional embodiments, the mass m1 of the ultrafine aluminum hydroxide crystal seed inducer and the mass m2 of the aluminum oxide in the second sodium aluminate solution satisfy the relationship: m1:m2=(35-45):100.

[0053] In these embodiments, the mass ratio of the ultrafine aluminum hydroxide seed crystal inducer to the aluminum oxide of the second sodium aluminate solution is (35-45):100, so that the ultrafine aluminum hydroxide seed crystal inducer can be quickly dissolved in the second sodium aluminate solution, so that the second sodium aluminate solution instantly bursts out a large number of ultrafine aluminum hydroxide crystal nuclei, which facilitates the subsequent acquisition of ultrafine aluminum hydroxide crystals with fine particle size.

[0054] The mass m1 of the ultrafine aluminum hydroxide crystal seed inducer can be 35, 36, 37, 40, 41 or 45.

[0055] In some optional embodiments, the caustic ratio of the first sodium aluminate solution is 1.30-1.60, and the mass concentration of aluminum oxide in the first sodium aluminate solution is 25 g / L-45 g / L; and / or

[0056] The caustic ratio of the second sodium aluminate solution is 1.40-1.60, and the mass concentration of aluminum oxide in the second sodium aluminate solution is 100 g / L-150 g / L.

[0057] In these embodiments, the first sodium aluminate solution with a caustic ratio of 1.30 to 1.60 has good decomposition kinetics and stability. In the presence of an aluminum sulfate solution, the crystal nuclei of the first sodium aluminate solution can grow rapidly to produce an ultrafine aluminum hydroxide seed inducer with a relatively fine particle size and high activity. The aluminum oxide in the first sodium aluminate solution with a mass concentration of 25 g / L to 45 g / L can give the first sodium aluminate solution good fluidity, prompting the first sodium aluminate solution to undergo an acid-base neutralization reaction at an appropriate reaction rate, ultimately producing an ultrafine aluminum hydroxide inducer with an appropriate pH and uniform dispersion. In addition, the crystal nuclei of the second sodium aluminate solution with a caustic ratio of 1.40 to 1.60 can grow rapidly to produce a nano-aluminum hydroxide seed product with a fine particle size and high activity. The aluminum oxide in the second sodium aluminate solution with a mass concentration of 100 g / L to 150 g / L can make the second sodium aluminate solution have good fluidity, promote the second sodium aluminate solution to perform seed decomposition reaction at an appropriate reaction rate, and ultimately obtain a nano-aluminum hydroxide seed product with suitable pH and uniform dispersion.

[0058] The caustic ratio of the first sodium aluminate solution may be 1.30, 1.35, 1.40, 1.45, 1.50, 1.55, or 1.60.

[0059] The mass concentration of aluminum oxide in the first sodium aluminate solution can be 25 g / L, 30 g / L, 35 g / L, 40 g / L or 45 g / L.

[0060] The caustic ratio of the second sodium aluminate solution may be 1.40, 1.45, 1.50, 1.55 or 1.60.

[0061] The mass concentration of aluminum oxide in the second sodium aluminate solution can be 100 g / L, 110 g / L, 120 g / L, 130 g / L, 140 g / L or 150 g / L.

[0062] It should be noted that, when the caustic ratio of the first sodium aluminate solution is less than 1.30, the viscosity of the first sodium aluminate solution is poor, which makes the stability of the first sodium aluminate solution poor and the neutralization reaction process difficult to control; when the caustic ratio of the first sodium aluminate solution is greater than 1.60, the alkalinity of the first sodium aluminate solution is high, which makes the neutralization reaction process of the first sodium aluminate solution slow, and the crystal nucleus growth rate is too fast, which results in the ultrafine aluminum hydroxide inducer having a coarse particle size and poor activity, which is not conducive to the subsequent seed crystal decomposition reaction.

[0063] It should be noted that, when the mass concentration of aluminum oxide in the first sodium aluminate solution is less than 25 g / L, the first sodium aluminate solution will cause the acid-base neutralization reaction to be too fast, making it difficult to ultimately control the pH of the ultrafine aluminum hydroxide seed inducer, and at the same time reduce the viscosity of the ultrafine aluminum hydroxide seed inducer, greatly affecting the production capacity of the ultrafine aluminum hydroxide seed inducer; when the mass concentration of aluminum oxide in the first sodium aluminate solution is greater than 45 g / L, the first sodium aluminate solution will be too viscous, reducing the fluidity of the first sodium aluminate solution; in addition, the viscous first sodium aluminate solution will cause serious agglomeration between the particles, which is not conducive to the preparation of nano aluminum hydroxide seeds.

[0064] It should be noted that, when the caustic ratio of the second sodium aluminate solution is less than 1.40, the viscosity of the second sodium aluminate solution is poor, which makes the stability of the second sodium aluminate solution poor and the seed decomposition reaction difficult to control; in addition, the second sodium aluminate solution with poor viscosity is difficult to completely dissolve the ultrafine aluminum hydroxide seed inducer, so that the second sodium aluminate solution cannot explosively produce a large number of aluminum hydroxide nuclei, and ultimately the number of ultrafine aluminum hydroxide seeds is small and the particle size is large; when the caustic ratio of the second sodium aluminate solution is greater than 1.60, the decomposition power of the second sodium aluminate solution is small, which makes the decomposition rate of the second sodium aluminate solution too slow, and the nucleus growth rate is too fast, which results in the ultrafine aluminum hydroxide seeds having a coarse particle size and poor activity, which is not conducive to the subsequent preparation of ultrafine aluminum hydroxide.

[0065] It should be noted that when the mass concentration of aluminum oxide in the second sodium aluminate solution is less than 100 g / L, although the second sodium aluminate solution with a relatively dilute concentration will make the seed decomposition reaction faster, the seed inducer is difficult to dissolve quickly in the relatively dilute sodium aluminate solution, and a large number of aluminum hydroxide nuclei cannot be produced explosively, which ultimately results in a small number of ultrafine aluminum hydroxide seeds and a larger particle size. At the same time, the sodium aluminate solution with a relatively dilute mass concentration will also reduce the viscosity of the ultrafine aluminum hydroxide seeds, greatly affecting the production capacity of the ultrafine aluminum hydroxide seeds; when the mass concentration of aluminum oxide in the second sodium aluminate solution is greater than 150 g / L, the second sodium aluminate solution will be too viscous, reducing the fluidity of the second sodium aluminate solution; in addition, the viscous second sodium aluminate solution will cause serious agglomeration between the particles, which is not conducive to the preparation of nano aluminum hydroxide seeds.

[0066] It should be noted that the raw material of the sodium aluminate solution is aluminum hydroxide, which is obtained by dissolving aluminum hydroxide and liquid alkali at a temperature of 102°C to 120°C, and then diluting and adjusting to a set caustic ratio and mass concentration of aluminum oxide.

[0067] Based on a general inventive concept, an embodiment of the present application provides a nano-aluminum hydroxide crystal seed prepared by the method described in any one of the above embodiments, wherein the average particle size D50 of the nano-aluminum hydroxide crystal seed does not exceed 0.1 μm, and the particle size D90 does not exceed 0.3 μm.

[0068] The nano-aluminum hydroxide seed crystal is realized based on the above-mentioned preparation method. The specific steps of the preparation method can refer to the above-mentioned embodiment. Since the nano-aluminum hydroxide seed crystal adopts part or all of the technical solutions of the above-mentioned embodiment, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiment, which will not be described one by one here.

[0069] Figure 3 A schematic diagram of the actual process of applying a nano-aluminum hydroxide seed crystal provided in an embodiment of the present application.

[0070] Based on a general inventive concept, such as Figure 3 As shown, the embodiment of the present application provides an application of nano-aluminum hydroxide seed crystals, and the application includes:

[0071] The nano-aluminum hydroxide seeds prepared by the method described in any of the above embodiments are used in the seed separation method to prepare ultrafine aluminum hydroxide, wherein the nano-aluminum hydroxide seeds and the sodium aluminate solution raw material undergo a seed separation decomposition reaction to obtain an ultrafine aluminum hydroxide product;

[0072] The caustic ratio of the sodium aluminate solution raw material is 1.40-1.60, and the mass concentration of aluminum oxide in the sodium aluminate solution raw material is 100 g / L-150 g / L.

[0073] The crystal nuclei of sodium aluminate solutions with a caustic ratio of 1.40 to 1.60 can grow smoothly, resulting in ultrafine aluminum hydroxide products with fine and uniform particle size. Alumina in sodium aluminate solutions with a mass concentration of 100g / L to 150g / L can give the sodium aluminate solution good fluidity, prompting the sodium aluminate solution to undergo seed crystal decomposition at an appropriate reaction rate, ultimately resulting in ultrafine aluminum hydroxide products with appropriate pH and uniform dispersion.

[0074] The caustic ratio of the sodium aluminate solution feedstock may be 1.40, 1.45, 1.50, 1.55, or 1.60.

[0075] The mass concentration of aluminum oxide in the sodium aluminate solution raw material can be 100 g / L, 110 g / L, 120 g / L, 130 g / L, 140 g / L or 150 g / L.

[0076] In some optional embodiments, the temperature of the seed decomposition reaction is 55° C. to 65° C., and the time of the seed decomposition reaction is 6 h to 7 h.

[0077] In some optional embodiments, the mass m3 of the ultrafine aluminum hydroxide seed crystals and the mass m4 of the aluminum oxide of the sodium aluminate solution raw material satisfy the relationship: m3:m4=(1-2):100.

[0078] When the seed dosage is too low (<1:100), there are insufficient nucleation sites, and the accumulation of solution supersaturation leads to explosive nucleation, forming particles with uneven particle sizes. When the dosage is too high (2:100), the seed crystals compete for the adsorption of aluminate ions, and some seed crystals stop growing due to insufficient nutrients, resulting in a waste of resources.

[0079] The value of m3 can be 1, 1.2, 1.4, 1.6, 1.8, 2, etc.

[0080] In summary, the preparation method and application of nano-aluminum hydroxide seed crystals provided in this application have significant advantages in terms of material properties, process controllability and application adaptability through multi-level parameter coordinated regulation and innovative action mechanism. The specific summary is as follows:

[0081] 1. Innovation and controllability advantages of the preparation process

[0082] (1) Multi-level nucleation control mechanism: a gel-like inducing agent is generated by neutralization reaction, and free hydroxyl groups are used to react with [Al(OH)4] - Formation of [Al(OH)5] 2-The transition state complex reduces the nucleation activation energy by over 30%, increasing the nucleation rate to twice that of traditional methods, enabling the rapid generation of nanoscale nuclei. The nano-mesoporous structure of the gel network creates a steric effect, forcing the crystals to grow preferentially along the (001) plane, forming a lamellar structure and avoiding the coarse particle size caused by three-dimensional disordered growth.

[0083] (2) Precise parameter collaborative design: The combination of a neutralization reaction temperature of 15-45°C and an endpoint pH of 7.0-8.0 enables aluminum sulfate and sodium aluminate solution to react to form a uniform, particle-free gel. Compared with the traditional acid-base neutralization method, the gel agglomeration rate is reduced from 40% to below 5%. When the seed decomposition reaction temperature is ≤60°C, by controlling the sudden increase in supersaturation, the second sodium aluminate solution is promoted to explosive nucleation within 2-3 hours. The number of crystal nuclei increases by 50% compared to reactions above 60°C, and the particle size distribution D50 / D90 is optimized from 0.2 / 0.5μm to 0.1 / 0.3μm.

[0084] 2. Breakthrough Advantages of Product Performance

[0085] (1) Nano-scale particle size and uniform distribution: The average particle size of the prepared seed crystals is D50 ≤ 0.1μm, D90 ≤ 0.3μm, and the particle size distribution span (D90-D50) is only 0.2μm, a 50% improvement over the traditional method (span 0.5μm), meeting the stringent requirements of high-end electronic ceramics for powder dispersion. The flaky nanostructured aluminum hydroxide provides more active sites for applications such as catalysis and adsorption.

[0086] (2) High activity and low residual alkali: The synergistic effect of crystal edge dislocations, surface dangling bonds, and cation vacancies increases the surface energy of the seed crystal, increasing its activity by 30% compared to conventional products. This accelerates the decomposition rate of sodium aluminate solution during the seeding reaction. The residual alkali content (calculated as Na2O) is <0.5%, which is lower than the industry standard (1.0%), avoiding the impact of alkalinity on the compatibility of polymer materials. It is particularly suitable for flame retardants, lithium battery separator coatings, and other applications.

[0087] 3. High efficiency and economic advantages of application technology

[0088] (1) Adaptability of the seeding method for preparing ultrafine aluminum hydroxide: Optimizing the sodium aluminate solution caustic ratio of 1.40-1.60 and the concentration of 100-150 g / L increased the solution fluidity by 20%, improving mass transfer efficiency. Combined with a reaction temperature of 55-65°C and a reaction time of 6-7 h, the product D50 remained stable below 0.2 μm, with batch-to-batch particle size fluctuations of ≤5%. A precise ratio of seed crystals (m3:m4 = 1-2:100) reduced seed crystal consumption by 30% and raw material costs by 15% compared to traditional methods while ensuring the density of nucleation sites.

[0089] (2) Process stability and production capacity advantages: The sodium aluminate solution is controlled at a caustic ratio of 1.30-1.60 and a concentration of 25-45 g / L, which prevents agglomeration or uncontrolled decomposition caused by abnormal solution viscosity. The neutralization reaction yield is stable at over 98%, and the annual production capacity can reach over 5,000 tons. The low-temperature process with a seed decomposition reaction temperature of ≤60°C saves 25% energy compared to the traditional high-temperature process (above 80°C), while also avoiding the generation of toxic gases such as AsH3, significantly improving safety.

[0090] The present application will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present application only and are not intended to limit the scope of the present application. The experimental methods in the following examples where specific conditions are not specified are generally measured according to industry standards. If there are no corresponding industry standards, then the methods are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0091] Example 1

[0092] like Figure 2 As shown, this embodiment provides a method for preparing nano-aluminum hydroxide seed crystals, comprising the following steps:

[0093] S11. The aluminum sulfate solution and the first sodium aluminate solution are neutralized to obtain ultrafine aluminum hydroxide seed crystals as an inducer; wherein the ultrafine aluminum hydroxide seed crystals as an inducer are a uniform gel-like material;

[0094] S21. Perform a seed decomposition reaction on the ultrafine aluminum hydroxide seed crystal inducer and the second sodium aluminate solution to obtain nano aluminum hydroxide seed crystals.

[0095] The temperature of the neutralization reaction is 30°C, and the endpoint pH value of the neutralization reaction is 7.5;

[0096] The temperature of the seed crystal decomposition reaction is 60° C., and the time of the seed crystal decomposition reaction is 2.5 h.

[0097] In the aluminum sulfate solution, the mass concentration of aluminum oxide is 8%, and the mass concentration of sulfate ion is 23%.

[0098] The mass m1 of the ultrafine aluminum hydroxide crystal seed inducer and the mass m2 of the aluminum oxide in the second sodium aluminate solution satisfy the relationship: m1:m2=35:100.

[0099] The caustic ratio of the first sodium aluminate solution is 1.33, and the mass concentration of aluminum oxide in the first sodium aluminate solution is 45 g / L;

[0100] The caustic ratio of the second sodium aluminate solution is 1.60, and the mass concentration of aluminum oxide in the second sodium aluminate solution is 100 g / L.

[0101] Based on the nano-aluminum hydroxide crystal seeds obtained above, this embodiment also provides an application of nano-aluminum hydroxide crystal seeds, including:

[0102] S31. The obtained aluminum hydroxide seed crystals are applied to the seed separation method for preparing ultrafine aluminum hydroxide. When the temperature of the sodium aluminate solution rises to 60°C, 2.0% (the ratio of the mass of aluminum hydroxide in the seed crystals to the mass of aluminum hydroxide in the sodium aluminate solution) of seed crystals are added dropwise. After the decomposition is completed, ultrafine aluminum hydroxide is obtained by filtration, washing and drying.

[0103] Example 2

[0104] Compared with Example 1, this embodiment has the following differences, and the rest are the same:

[0105] The temperature of the neutralization reaction was 15°C, and the endpoint pH value of the neutralization reaction was 7.0;

[0106] The temperature of the seed crystal decomposition reaction was 50° C., and the time of the seed crystal decomposition reaction was 3.0 h.

[0107] In the aluminum sulfate solution, the mass concentration of aluminum oxide is 10%, and the mass concentration of sulfate ion is 28%.

[0108] The mass m1 of the ultrafine aluminum hydroxide crystal seed inducer and the mass m2 of the aluminum oxide in the second sodium aluminate solution satisfy the relationship: m1:m2=45:100.

[0109] The caustic ratio of the first sodium aluminate solution is 1.60, and the mass concentration of aluminum oxide in the first sodium aluminate solution is 25 g / L;

[0110] The caustic ratio of the second sodium aluminate solution is 1.40, and the mass concentration of aluminum oxide in the second sodium aluminate solution is 150 g / L.

[0111] Example 3

[0112] Compared with Example 1, this embodiment has the following differences, and the rest are the same:

[0113] The temperature of the neutralization reaction is 45°C, and the endpoint pH value of the neutralization reaction is 8.0;

[0114] The temperature of the seed crystal decomposition reaction is 40° C., and the time of the seed crystal decomposition reaction is 2.0 h.

[0115] In the aluminum sulfate solution, the mass concentration of aluminum oxide is 5%, and the mass concentration of sulfate ion is 14%.

[0116] The mass m1 of the ultrafine aluminum hydroxide crystal seed inducer and the mass m2 of the aluminum oxide in the second sodium aluminate solution satisfy the relationship: m1:m2=40:100.

[0117] The caustic ratio of the first sodium aluminate solution is 1.50, and the mass concentration of aluminum oxide in the first sodium aluminate solution is 30 g / L;

[0118] The caustic ratio of the second sodium aluminate solution is 1.50, and the mass concentration of aluminum oxide in the second sodium aluminate solution is 120 g / L.

[0119] Comparative Example 1

[0120] Compared with Example 1, the differences of this comparative example are as follows, and the rest are the same:

[0121] The mass m1 of the ultrafine aluminum hydroxide crystal seed inducer and the mass m2 of the aluminum oxide in the second sodium aluminate solution satisfy the relationship: m1:m2=55:100.

[0122] The temperature of the seed crystal decomposition reaction was 65°C.

[0123] The caustic ratio of the second sodium aluminate solution was 1.30.

[0124] Comparative Example 2

[0125] Compared with Example 1, the differences of this comparative example are as follows, and the rest are the same:

[0126] The temperature of the neutralization reaction was 65°C.

[0127] The caustic ratio of the first sodium aluminate solution is 1.65, and the mass concentration of aluminum oxide in the first sodium aluminate solution is 65 g / L.

[0128] The embodiments described above are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0129] Related experiments and effect data:

[0130] The particle size of the ultrafine aluminum hydroxide seed crystals prepared in Examples 1 to 3 and Comparative Examples 1 to 2 was tested, and the results are shown in Table 1. The particle size and alkali content of the prepared ultrafine aluminum hydroxide product were tested, and the results are shown in Table 2.

[0131] Table 1 Particle size test data of ultrafine aluminum hydroxide seeds obtained in Examples and Comparative Examples

[0132]

[0133] Table 2 Performance data of ultrafine aluminum hydroxide products obtained in Examples and Comparative Examples

[0134]

[0135] In Table 1, the nano-aluminum hydroxide seeds obtained in Examples 1 to 3 have a D50 of 0.058 to 0.093 μm and a D90 of 0.152 to 0.238 μm. Their particle size is smaller than the average particle size (D50 < 2.0 μm) of the seeds of conventional mechanically ground micro-powder aluminum hydroxide, and their particle size distribution is more concentrated and their activity is higher. The average particle size D50 of the ultrafine aluminum hydroxide produced as seeds is < 0.3 μm, and the particle size distribution is concentrated.

[0136] In Comparative Examples 1 and 2, the preparation processes of the seed crystals are different, the mass ratio of the seed crystal inducer to the aluminum oxide in the sodium aluminate solution is too high (>50%), the decomposition reaction temperature is too high (>60°C), the caustic ratio of the sodium aluminate solution is too small (<1.40) or too large (>1.60), and the obtained aluminum hydroxide seed crystals have a particle size D50>2.5μm. Compared with Examples 1 to 3 of the present invention, their particle size is significantly coarse and their activity is poor. The ultrafine aluminum hydroxide prepared as the seed crystal has a coarse particle size, an uneven particle size distribution, and large particles.

[0137] In Table 2, the average particle size D50 of the ultrafine aluminum hydroxide prepared in Examples 1 to 3 is 0.115-0.201 μm, not exceeding 0.3 μm, and D90 is 0.367-0.429 μm, not exceeding 0.5 μm, indicating that the ultrafine aluminum hydroxide has a small particle size and a concentrated particle size distribution; the Na2O content is 0.187-0.202%.

[0138] In comparison, the ultrafine aluminum hydroxide prepared in Comparative Examples 1 and 2 has coarse particle size, uneven particle size distribution, and high content of impurity Na2O. This is because the coarse seed crystals prepared in Comparative Examples 1 and 2, or the decomposition temperature is too high, are not conducive to the decomposition and preparation of ultrafine aluminum hydroxide with fine and uniform particle size.

[0139] In addition, one or more technical solutions in the embodiments of the present application have at least the following technical effects or advantages:

[0140] In the embodiments of the present application, the nano-aluminum hydroxide crystal seeds and the ultrafine aluminum hydroxide preparation technology use a seed separation method, which has a simple preparation process, is green and environmentally friendly, has low cost, is suitable for industrial production, and the prepared ultrafine aluminum hydroxide has the characteristics of fine particle size, good dispersibility, and narrow particle size distribution. It is a method commonly used in industry to produce ultrafine aluminum hydroxide.

[0141] In the embodiment of the present application, this nano-aluminum hydroxide seed preparation technology first makes a homemade ultrafine aluminum hydroxide seed inducer, and mixes aluminum sulfate solution with sodium aluminate solution for neutralization reaction to obtain an ultrafine aluminum hydroxide seed inducer. By controlling the solution concentration, neutralization reaction temperature, endpoint pH value and other conditions, the ultrafine aluminum hydroxide seed inducer is in a colloidal state and can be quickly dissolved when added to the sodium aluminate solution, thereby reducing the causticity ratio of the solution. A large number of ultrafine aluminum hydroxide crystal nuclei are instantly produced in the solution, and the crystal nuclei have fine particle size, uniform distribution, and high activity.

[0142] In the examples of the present application, this technology does not require the addition of an external organic dispersant. The prepared nano-aluminum hydroxide seeds have high activity, fine particle size, good dispersibility, concentrated particle size distribution, and an average particle size D50 of no more than 0.1 μm and a D90 of no more than 0.3 μm. These seeds are used in the sodium aluminate solution seed separation method to prepare ultrafine aluminum hydroxide. The ultrafine aluminum hydroxide product has an average particle size D50 of no more than 0.3 μm, a D90 of no more than 0.5 μm, and a Na2O content of less than 0.3%. This solves the problem of coarse particle size and large particles in current ultrafine aluminum hydroxide products, broadening the application field of ultrafine aluminum hydroxide.

[0143] In the embodiments of the present application, the prepared nano-aluminum hydroxide seeds have high activity, fine particle size and good dispersibility. These seeds are used to prepare ultrafine aluminum hydroxide by the sodium aluminate solution seed separation method. They have special properties that general ultrafine aluminum hydroxide does not have, and can also be used as raw materials for preparing nano-alumina.

[0144] In the embodiments of the present application, the method for preparing nano-aluminum hydroxide seeds provided has technical characteristics such as simple process, low cost, and green environmental protection. It solves the current problems of high cost, high impurity content, especially severe agglomeration, and coarse particle size of ultrafine aluminum hydroxide products. It can be applied to fields such as flame retardants, has better application performance, and therefore has broad market application prospects.

[0145] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A method for preparing nano-aluminum hydroxide seed crystals, comprising: The aluminum sulfate solution is mixed with the first sodium aluminate solution to carry out a neutralization reaction to obtain an ultrafine aluminum hydroxide crystal seed inducer; The ultrafine aluminum hydroxide crystal seed inducer is a gel-like material; The ultrafine aluminum hydroxide seed crystal inducer and the second sodium aluminate solution are subjected to a seed decomposition reaction to obtain nano aluminum hydroxide seed crystals; the temperature of the seed decomposition reaction is ≤60°C.

2. The method according to claim 1, characterized in that The temperature of the neutralization reaction is 15° C. to 45° C., and the pH value at the reaction end point of the neutralization reaction is 7.0 to 8.

0.

3. The method according to claim 1, characterized in that The temperature of the seed crystal decomposition reaction is 40° C. to 60° C., and the time of the seed crystal decomposition reaction is 2.0 h to 3.0 h.

4. The method according to claim 1, wherein In the aluminum sulfate solution, the content of aluminum oxide is 4% to 10%, and the content of sulfate radical is 11% to 28%.

5. The method according to claim 1, wherein The mass m1 of the ultrafine aluminum hydroxide crystal seed inducer and the mass m2 of the aluminum oxide in the second sodium aluminate solution satisfy the relationship: m1:m2=(35-45):

100.

6. The method according to claim 1, characterized in that The caustic ratio of the first sodium aluminate solution is 1.30 to 1.60, and the mass concentration of aluminum oxide in the first sodium aluminate solution is 25 g / L to 45 g / L; and / or The caustic ratio of the second sodium aluminate solution is 1.40-1.60, and the mass concentration of aluminum oxide in the second sodium aluminate solution is 100 g / L-150 g / L.

7. A nano-aluminum hydroxide seed crystal prepared by the method according to any one of claims 1 to 6, characterized in that: The average particle size D50 of the nano-aluminum hydroxide seed crystals does not exceed 0.1 μm, and the particle size D90 does not exceed 0.3 μm.

8. An application of nano-aluminum hydroxide seed crystals, comprising: The nano-aluminum hydroxide seeds prepared by the method according to any one of claims 1 to 6 are used in the seed separation method to prepare ultrafine aluminum hydroxide, and the nano-aluminum hydroxide seeds and the sodium aluminate solution raw material undergo a seed separation decomposition reaction to obtain an ultrafine aluminum hydroxide product; The caustic ratio of the sodium aluminate solution raw material is 1.40-1.60, and the mass concentration of aluminum oxide in the sodium aluminate solution raw material is 100 g / L-150 g / L.

9. The use according to claim 8, characterized in that The temperature of the seed decomposition reaction is 55° C. to 65° C., and the time of the seed decomposition reaction is 6 h to 7 h.

10. The use according to claim 8, characterized in that The mass m3 of the ultrafine aluminum hydroxide seed crystals and the mass m4 of the aluminum oxide of the sodium aluminate solution raw material satisfy the relationship: m3:m4=(1-2):100.

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