Boehmite, its preparation method and application

Abstract

This application discloses a method for preparing boehmite, comprising the following steps: mixing an aluminum source and water to obtain a precursor sol, wherein the aluminum source includes basic aluminum acetate and / or aluminum isopropoxide; adding amino acids to the precursor sol to obtain a reaction raw material, wherein the pH of the reaction raw material is 5.5-7.5; reacting the reaction raw material in a microchannel reactor to obtain a boehmite suspension; and performing solid-liquid separation, washing, and drying of the boehmite suspension to obtain the boehmite. The boehmite prepared by this method has fewer impurities, higher purity, narrower particle size distribution, and is less prone to agglomeration.

Description

Technical Field

[0001] This application relates to the field of inorganic nanomaterials technology, and in particular to a boehmite, its preparation method and application. Background Technology

[0002] Boehmite (γ-AlOOH), with its excellent high-temperature resistance, insulation, wear resistance, and heat insulation properties, has become a core inorganic filler in the fields of new energy and semiconductors. The common process for preparing boehmite by the traditional hydrothermal method involves using a reaction vessel and artificially adjusting the pH with external acids and bases. Commonly used acid and base reagents include hydrochloric acid, nitric acid, sulfuric acid, ammonia, and sodium hydroxide. The acid-base environment of the hydrothermal system is controlled by adding acid and base in stages, thereby controlling nucleation and crystal growth.

[0003] Traditional processes have four inherent defects: First, exogenous acids and alkalis easily introduce residual impurities such as chloride ions, sulfate ions, sodium ions, and potassium ions, resulting in a total impurity content in the powder generally exceeding 80 ppm, making it difficult to meet the requirements of high-end, high-purity boehmite. Second, manual segmented pH adjustment leads to large pH fluctuations between production batches, uneven crystal nucleation rates, wide particle size distribution, severe agglomeration, and poor dispersibility of the product. Third, acid-base neutralization reactions easily produce byproduct salt residues, further reducing the cleanliness of the powder. Fourth, the process generates a large amount of acid and alkali cleaning wastewater, making it impossible to achieve zero discharge, resulting in high environmental pressure during mass production and high post-treatment costs.

[0004] Therefore, developing a continuous, short-process, low-energy-consumption, and highly stable synthesis method for high-purity boehmite has significant industrial value. Summary of the Invention

[0005] The boehmite, its preparation method, and its application provided according to one or more embodiments of this application solve at least one of the technical problems of low purity, wide particle size distribution, easy agglomeration, and environmental unfriendliness of boehmite produced by traditional processes.

[0006] A first aspect of this application provides a method for preparing boehmite, comprising the following steps: mixing an aluminum source and water to obtain a precursor sol, wherein the aluminum source includes basic aluminum acetate and / or aluminum isopropoxide; adding amino acids to the precursor sol to obtain a reaction raw material, wherein the pH of the reaction raw material is 5.5-7.5; reacting the reaction raw material in a microchannel reactor to obtain a boehmite suspension; and performing solid-liquid separation, washing, and drying on the boehmite suspension to obtain the boehmite.

[0007] Optionally, the aluminum source includes basic aluminum acetate and aluminum isopropoxide, wherein the mass ratio of basic aluminum acetate to aluminum isopropoxide in the aluminum source is (1~2):1.

[0008] Optionally, the solid-liquid ratio of the aluminum source and water is 1g:(8~15)mL.

[0009] Optionally, the purity of the aluminum source is ≥99.95%, and the resistivity of the water is ≥18.5 MΩ·cm.

[0010] Optionally, the amino acid includes one or more of glycine, alanine, and lysine.

[0011] Optionally, the amount of amino acid added is 0.1% to 0.5% of the mass of the precursor sol.

[0012] Optionally, the amount of amino acid added is 0.2% to 0.3% of the mass of the precursor sol.

[0013] Optionally, the step of reacting the reactants in a microchannel reactor includes a first reaction stage, a second reaction stage, and a third reaction stage performed sequentially. The temperature of the first reaction stage is 110℃~130℃, and the residence time of the first reaction stage is 2min~5min; The temperature of the second reaction stage is 150℃~170℃, and the residence time of the second reaction stage is 3min~8min; The temperature of the third reaction stage is 170℃~190℃, and the residence time of the third reaction stage is 5min~15min.

[0014] Optionally, the flow rate of the reaction feedstock is 5 L / h to 50 L / h, and / or the pressure of the reaction does not exceed 1.0 MPa.

[0015] A second aspect of this application provides a boehmite obtained by the preparation method described in the first aspect above, wherein the total impurity content of the boehmite is <22ppm, the particle size D50 of the boehmite is 40nm~100nm, and the particle size D90 / D10 of the boehmite is ≤1.4.

[0016] A third aspect of this application provides the application of boehmite as described in the second aspect above in lithium battery separators, semiconductor packaging, or grinding and polishing.

[0017] Compared with the prior art, the technical solution provided in this application has the following beneficial effects: The method for preparing boehmite in this application involves mixing basic aluminum acetate and / or aluminum isopropoxide with water to obtain a precursor sol. Amino acids are then added to the precursor sol to obtain the reaction raw material. The pH of the reaction raw material is 5.5–7.5 (i.e., the initial pH of the reaction system is 5.5–7.5). The reaction raw material is then reacted in a microchannel reactor (microchannel continuous flow reaction). During the reaction, basic aluminum acetate and / or aluminum isopropoxide can uniformly and slowly release trace amounts of H2 in situ. + / OH- This process counteracts localized pH fluctuations caused by heating, crystal hydrolysis, and dehydration. Simultaneously, amino acids act as reversible pH buffers, forming reversible buffer pairs with the precursor sol. Through reversible proton dissociation and binding reactions, the pH of the reaction system is stabilized secondaryly. The synergistic effect of the in-situ slow-release aluminum source (basic aluminum acetate and / or aluminum isopropoxide) combined with the reversible pH buffer (amino acids) ensures that the pH remains stably locked within a narrow range of 5.5–7.5 throughout the entire microchannel continuous flow reaction, achieving steady-state control over the entire crystal nucleation and growth process. The entire preparation process involves no acid or alkali intervention and no pH segmentation, completely avoiding anionic and alkali metal impurities introduced by exogenous reagents such as hydrochloric acid, sulfuric acid, ammonia, and strong alkalis. The total impurity content can be reduced to below 22 ppm, far exceeding the purity of products from traditional processes, making it suitable for high-end, high-purity boehmite applications. The microchannel continuous flow reaction maintains a stable pH within the optimal growth range of 5.5 to 7.5 throughout the process, avoiding problems such as uneven nucleation, crystal defects, and powder agglomeration caused by drastic pH fluctuations. The resulting boehmite has a uniform morphology (narrow particle size distribution) and excellent dispersibility.

[0018] Furthermore, the entire preparation process is a closed-loop reaction, and the rinsing water after washing can be recycled. No acid or alkaline wastewater or hazardous waste is generated, eliminating the need for complex acid and alkaline wastewater treatment equipment. This significantly reduces environmental and operational costs for mass production and is suitable for large-scale continuous production. Compared to batch reactors, this preparation method reduces energy consumption by 50% and shortens the cycle time by more than 70%, demonstrating strong industrial applicability. Attached Figure Description

[0019] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and disclosure, and together with the description serve to explain the principles of this application and disclosure.

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This application provides a method for preparing boehmite according to some embodiments thereof; Figure 2 Electron micrograph (SEM image) of the nano-boehmite prepared in Example 1. Figure 3 The X-ray diffraction pattern (XRD pattern) of the nano-boehmite prepared in Example 1. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. The term "implementation" as used herein has a similar understanding.

[0024] In this application, except where expressly stated, any matters or issues not mentioned are directly applicable to those known in the art without any modification. Furthermore, any implementation described in this application can be freely combined with one or more other implementations described in this application, and the resulting technical solutions or concepts shall be considered part of the original disclosure or original record of this application, and should not be regarded as new content not disclosed or anticipated in this application, unless those skilled in the art consider the combination to be clearly unreasonable.

[0025] Any method steps, processes, and operations described in this application should not be construed as necessarily requiring them to be performed in a particular order as discussed or shown, unless explicitly specified. It should also be understood that additional or alternative steps may be used unless otherwise stated.

[0026] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0027] Any specific numerical values ​​disclosed herein (including the endpoints of numerical ranges) are not limited to their exact values, but should be understood to also include values ​​close to the exact value, such as all possible values ​​within ±5% of the exact value. Furthermore, with respect to the disclosed numerical ranges, one or more new numerical ranges can be obtained by arbitrarily combining the endpoint values ​​of the range, the endpoint values ​​with specific point values ​​within the range, and the specific point values ​​themselves; these new numerical ranges should also be considered as specifically disclosed herein.

[0028] Unless otherwise stated, the terms used herein have the same meaning as commonly understood by those skilled in the art, and if a term is defined herein and its definition differs from the common understanding in the art, the definition herein shall prevail.

[0029] First aspect Please see Figure 1 Some embodiments of this application provide a method for preparing boehmite, comprising the following steps: S1, mix aluminum source and water to obtain precursor sol, the aluminum source including basic aluminum acetate and / or aluminum isopropoxide; S2, amino acids are added to the precursor sol to obtain the reaction raw material, the pH of which is 5.5~7.5; S3, the reactants are reacted in a microchannel reactor to obtain a boehmite suspension; and S4. The boehmite suspension is subjected to solid-liquid separation, washing and drying to obtain boehmite.

[0030] The method for preparing boehmite in this application involves using basic aluminum acetate and / or aluminum isopropoxide as the aluminum source, mixing them with water to obtain a precursor sol, and then adding amino acids to the precursor sol to obtain the reaction raw materials. The pH of the reaction raw materials is 5.5~7.5 (i.e., the initial pH of the reaction system is 5.5~7.5). The reaction raw materials are then reacted in a microchannel reactor (microchannel continuous flow reaction). During the reaction, basic aluminum acetate and / or aluminum isopropoxide can release trace amounts of H+ / OH- in situ uniformly and slowly, offsetting local pH fluctuations caused by heating, crystal hydrolysis, and dehydration processes; at the same time, amino acids can act as a reversible pH buffer, forming a reversible buffer pair with the precursor sol, and stabilizing the pH of the reaction system through a reversible proton dissociation and binding reaction. The in-situ slow-release aluminum source (basic aluminum acetate and / or aluminum isopropoxide) combined with a pH reversible buffer (amino acid) synergistically locks the pH within a narrow range of 5.5–7.5 throughout the entire microchannel continuous flow reaction, achieving steady-state control over the entire crystal nucleation and growth process. The entire preparation process involves no acid-base intervention and no pH segmentation, completely avoiding anionic and alkali metal impurities introduced by exogenous reagents such as hydrochloric acid, sulfuric acid, ammonia, and strong alkalis. The total impurity content can be reduced to below 22 ppm, far exceeding the purity of products from traditional processes, making it suitable for high-end, high-purity boehmite applications. The microchannel continuous flow reaction maintains a stable pH within the optimal growth range of 5.5–7.5 throughout the process, avoiding uneven nucleation, crystal defects, and powder agglomeration caused by drastic pH fluctuations. The resulting boehmite product exhibits uniform morphology and excellent dispersibility.

[0031] In some embodiments, the aluminum source includes basic aluminum acetate and aluminum isopropoxide, wherein the mass ratio of basic aluminum acetate to aluminum isopropoxide in the aluminum source is (1~2):1. Exemplarily, the mass ratio of basic aluminum acetate to aluminum isopropoxide in the aluminum source is 1:1, 1.5:1, or 2:1.

[0032] In some embodiments, the solid-liquid ratio of aluminum source to water is 1 g: (8~15) mL. Exemplarily, the solid-liquid ratio of aluminum source to water is 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14 or 1:15.

[0033] In some embodiments, the method of mixing the aluminum source and water in step S1 includes stirring. For example, the aluminum source and water are stirred at room temperature (20°C to 25°C) for 20 min to 30 min to make the pH of the precursor sol 5.5 to 7.5, and the aluminum source is initially hydrolyzed.

[0034] In some implementations, the purity of the aluminum source is ≥99.95%, and the resistivity of the water is ≥18.5 MΩ·cm, ensuring the purity of the aluminum source and water and preventing the introduction of impurities from the source.

[0035] In some embodiments, the amino acid includes one or more of glycine, alanine, and lysine.

[0036] In some embodiments, in order to ensure the uniformity of the reaction raw materials, step S2 includes a stirring step after adding amino acids to the precursor sol, stirring for 10 min to 15 min to make the amino acids uniformly dispersed and form a reversible buffer pair with the precursor sol.

[0037] In some embodiments, the amount of amino acids added is 0.1% to 0.5% of the precursor sol mass. Exemplarily, the amount of amino acids added is 0.10%, 0.15%, 0.20%, 0.25%, 0.30%, 0.35%, 0.40%, 0.45%, or 0.50% of the precursor sol mass. In some optional embodiments, the amount of amino acids added is 0.2% to 0.3% of the precursor sol mass.

[0038] Traditional boehmite synthesis mainly relies on batch hydrothermal processes, which suffer from poor batch stability, uneven heat and mass transfer, wide particle size distribution (D90 / D10>3.0), high energy consumption, and significant scale-up effects. The method presented in this application utilizes a microchannel reactor, which offers advantages such as high heat and mass transfer efficiency, narrow residence time distribution, and continuous controllability.

[0039] In some embodiments, the mechanical diameter of the microchannel reactor is 200 μm to 400 μm. It should be noted that the mechanical diameter has a meaning well-known in the art; for non-circular cross-section channels, its hydraulic diameter is defined as the ratio of four times the channel cross-sectional area to the wetting perimeter length, i.e. Where A is the cross-sectional area of ​​the channel, P is the wetting perimeter, and Dh is the hydraulic diameter; for a circular cross-section channel, the hydraulic diameter is the inner diameter of the circular pipe.

[0040] For example, the mechanical diameter of the microchannel reactor is 200 μm, 250 μm, 300 μm, 350 μm or 400 μm.

[0041] In some implementations, the microchannel reactor is a tubular microchannel reactor or a plate-shaped microchannel reactor.

[0042] In some embodiments, step S3 includes a first reaction stage, a second reaction stage, and a third reaction stage performed sequentially. The temperature of the first reaction stage is 110℃~130℃, and the residence time of the first reaction stage is 2min~5min; The temperature of the second reaction stage is 150℃~170℃, and the residence time of the second reaction stage is 3min~8min; The temperature of the third reaction stage is 170℃~190℃, and the residence time of the third reaction stage is 5min~15min.

[0043] The first reaction stage is a preheating stage. For example, the temperature of the first reaction stage is 110°C, 120°C, or 130°C, and the residence time of the first reaction stage is 2 min, 3 min, 4 min, or 5 min.

[0044] The second reaction stage is the crystal nucleation stage. For example, the temperature of the second reaction stage is 150°C, 160°C, or 170°C, and the residence time of the second reaction stage is 3 min, 4 min, 5 min, 6 min, 7 min, or 8 min.

[0045] The third reaction stage is the crystal growth stage. For example, the temperature of the third reaction stage is 170°C, 180°C, or 190°C, and the residence time of the third reaction stage is 5 min, 6 min, 7 min, 8 min, 10 min, 12 min, 14 min, or 15 min.

[0046] In some embodiments, the flow rate of the reactants is 5 L / h to 50 L / h. Exemplarily, the flow rate of the reactants can be 5 L / h, 10 L / h, 20 L / h, 30 L / h, 40 L / h, or 50 L / h. Within a given total volume of the microchannel reactor, the residence time of each reaction stage (including the first, second, and third reaction stages) is achieved by adjusting the flow rate of the reactants. This preparation method has adjustable throughput, can be directly integrated into existing production lines, can operate continuously for 24 hours, and has strong industrial adaptability.

[0047] The above reaction is carried out in a closed microchannel reactor, where the reaction system maintains liquid-phase stability through autogenous pressure generated by its own temperature rise. In some embodiments, the reaction pressure does not exceed 1.0 MPa.

[0048] In some implementations, the washing process in step S4 uses high-purity deionized water for rinsing. A single rinsing with high-purity deionized water is sufficient to remove trace amounts of residual impurities (such as decomposition products of organic raw materials). The rinse water is then filtered, sterilized, and recycled for the preparation of the next batch of feed solution, achieving zero discharge and complete closed-loop recycling of process wastewater. The recycling of rinse water eliminates the generation of acidic or alkaline wastewater and hazardous waste, eliminating the need for complex acid and alkaline wastewater treatment equipment, significantly reducing environmental protection and maintenance costs for mass production, and making it suitable for large-scale continuous production.

[0049] Second aspect Some embodiments of this application provide a boehmite obtained by the preparation method described in any embodiment of the first aspect above. The total impurity content of this boehmite is <22 ppm.

[0050] The boehmite is prepared based on the above-described method. The specific characteristics described above can be found in the above-described embodiments. Since the boehmite adopts some or all of the technical solutions described above, it has at least all the beneficial effects brought about by the technical solutions described above, which will not be elaborated here.

[0051] In some embodiments, the boehmite has a particle size D50 of 40 nm to 100 nm. For example, the boehmite has a particle size D50 of 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm or 100 nm.

[0052] In some embodiments, the boehmite has a grain size D90 / D10 ≤ 1.4. Exemplarily, the boehmite has a grain size D90 / D10 ≤ 1.2, D90 / D10 ≤ 1.0, D90 / D10 ≤ 0.8, or D90 / D10 ≤ 0.6.

[0053] The above indicates that the boehmite has a uniform morphology, narrow particle size distribution, and good dispersibility.

[0054] Third aspect Some embodiments of this application provide the use of boehmite in lithium-ion battery separators, semiconductor packaging, or grinding and polishing as described in any embodiment of the second aspect above.

[0055] The boehmite described in the second aspect above is prepared by the method described in the first aspect above, and therefore has the advantages of high purity, narrow particle size distribution and good dispersibility, and can be applied to lithium battery separators, semiconductor packaging or grinding and polishing and other application scenarios.

[0056] Example To better understand this application, the following description, in conjunction with embodiments, further illustrates this application. However, the scope of protection claimed by this application is not limited to the scope of the embodiments.

[0057] In the following examples, unless otherwise specified, all experimental instruments, raw materials, and quantities involved are commercially available products or can be prepared by known methods. Experimental methods not specifying particular conditions in the examples were performed under conventional conditions, such as those described in literature, books, or methods recommended by the manufacturer.

[0058] Unless otherwise specified, the specific parameters used in each step of the material preparation process in each embodiment and comparative example are the same.

[0059] Example 1 S1. Using 99.95% pure basic aluminum acetate and 99.95% pure aluminum isopropoxide (mass ratio 1:1) as aluminum sources, mix with 18.5 MΩ·cm high-purity deionized water at a solid-liquid ratio of 1 g: 10 mL and stir at room temperature (25℃) for 25 min to obtain a transparent precursor sol.

[0060] S2, Glycine was added to the transparent precursor sol as a pH buffer. The amount of glycine added was 0.25% of the mass of the precursor sol. The mixture was stirred for 12 minutes to disperse it evenly, and the reaction raw material was obtained. The initial pH of the system was 6.3.

[0061] S3. The reactants are transferred to a microchannel reactor with a hydraulic diameter of 200 μm for reaction. The temperature of the first reaction stage is 120℃ and the residence time is 3 min; the temperature of the second reaction stage is 160℃ and the residence time is 5 min; the temperature of the third reaction stage is 180℃ and the residence time is 12 min. The reaction is carried out at atmospheric pressure (0.1 MPa) and the flow rate of the reactants is 20 L / h.

[0062] S4. After the reaction is complete, the reaction solution is cooled and centrifuged. It is then rinsed once with high-purity deionized water, and all the rinsing water is recycled. The solid phase is dried in a vacuum drying oven at 90℃ for 4 hours to obtain boehmite.

[0063] Performance testing: The total impurity content of the boehmite powder was 12 ppm, D50 was 100 nm, D90 / D10 was 1.3, and the purity was 99.9988%. The boehmite powder exhibited excellent dispersibility and no hard agglomerates. No wastewater was discharged during the entire process. Scanning electron micrographs of the boehmite prepared in this example are shown below. Figure 2 As shown, Figure 2 As shown, its particle size distribution is uniform, its dispersibility is excellent, and there are no hard agglomerates. The X-ray diffraction pattern is as follows. Figure 3 As shown, the black dots indicate that there are strong and sharp peaks near 14.5°, 28.2°, 38.6° and 49°, which are characteristic peaks of boehmite.

[0064] Example 2 S1. Aluminum isopropoxide with a purity of 99.95% was selected as the aluminum source and mixed with 18.5 MΩ·cm high-purity deionized water at a solid-liquid ratio of 1 g: 12 mL. The mixture was stirred at room temperature (25℃) for 30 min to obtain a transparent precursor sol.

[0065] S2, Alanine was added to the transparent precursor sol as a pH buffer. The amount of alanine added was 0.2% of the mass of the precursor sol. The mixture was stirred for 15 min to obtain the reaction raw material. The initial pH of the system was 6.8.

[0066] Steps S3 and S4 are the same as in Example 1.

[0067] Performance testing: The total impurity content of the boehmite powder is 16 ppm, D50 is 80 nm, D90 / D10 is 1.1, and the purity is 99.9984%. The boehmite powder exhibits excellent dispersibility and no hard agglomerates. No wastewater is discharged during the entire process.

[0068] Example 3 S1. Basic aluminum acetate with a purity of 99.95% was selected as the aluminum source and mixed with 18.5 MΩ·cm high-purity deionized water at a solid-liquid ratio of 1 g: 9 mL. The mixture was stirred at room temperature (25℃) for 20 min to obtain a transparent precursor sol.

[0069] S2, lysine was added to the transparent precursor sol as a pH buffer. The amount of lysine added was 0.4% of the mass of the precursor sol. The mixture was stirred for 10 min to obtain the reaction raw material. The initial pH of the system was 5.8.

[0070] Steps S3 and S4 are the same as in Example 1.

[0071] Performance testing: The total impurity content of the boehmite powder is 10 ppm, D50 is 90 nm, D90 / D10 is 1.4, and the purity is 99.9990%. The boehmite powder exhibits excellent dispersibility and no hard agglomerates. No wastewater is discharged during the entire process.

[0072] Example 4 The procedure is essentially the same as in Example 1, except that in step S2, the pH buffer is composed of glycine and alanine in a mass ratio of 1:1. The amount of pH buffer added is 0.25% of the mass of the precursor sol.

[0073] Performance testing: The total impurity content of the boehmite powder is 9 ppm, D50 is 80 nm, D90 / D10 is 1.2, and the purity is 99.9991%. The boehmite powder exhibits excellent dispersibility and no hard agglomerates. No wastewater is discharged during the entire process.

[0074] Example 5 It is basically the same as Example 1, except that the hydraulic diameter of the microchannel reactor in step S3 is 300 μm.

[0075] Performance testing: The total impurity content of the boehmite powder is 21 ppm, D50 is 80 nm, D90 / D10 is 1.2, and the purity is 99.9979%. The boehmite powder exhibits excellent dispersibility and no hard agglomerates. No wastewater is discharged during the entire process.

[0076] Example 6 The process is basically the same as in Example 1, except for step S3. All other steps are the same as in Example 1. Specifically, step S3 is as follows: The reactants were transferred to a microchannel reactor with a hydraulic diameter of 200 μm for reaction. The temperature of the first reaction stage was 130 °C and the residence time was 5 min; the temperature of the second reaction stage was 170 °C and the residence time was 8 min; the temperature of the third reaction stage was 190 °C and the residence time was 15 min. The reaction was carried out at atmospheric pressure (0.1 MPa) and the flow rate of the reactants was 20 L / h.

[0077] Performance testing: The total impurity content of the boehmite powder is 18 ppm, D50 is 90 nm, D90 / D10 is 1.3, and the purity is 99.9982%. The boehmite powder exhibits excellent dispersibility and no hard agglomerates. No wastewater is discharged during the entire process.

[0078] Example 7 It is basically the same as Example 1, except that the reaction in step S3 is carried out at 0.5 MPa.

[0079] Performance testing: The total impurity content of the boehmite powder is 15 ppm, D50 is 75 nm, D90 / D10 is 1.3, and the purity is 99.9985%. The boehmite powder exhibits excellent dispersibility and no hard agglomerates. No wastewater is discharged during the entire process.

[0080] Example 8 It is basically the same as Example 1, except that the flow rate of the reaction raw material in step S3 is 42 L / h.

[0081] Performance testing: The total impurity content of the boehmite powder is 13 ppm, D50 is 70 nm, D90 / D10 is 1.3, and the purity is 99.9987%. The boehmite powder exhibits excellent dispersibility and no hard agglomerates. No wastewater is discharged during the entire process.

[0082] Comparative Example 1 The difference from Example 1 is that step S2 is omitted, and step S3 is also different. Specifically: The same transparent precursor sol as in Example 1 was added to a high-pressure hydrothermal reactor and reacted at a constant temperature of 180°C for 4.5 hours. During the reaction, the pH of the system was artificially adjusted to 6.3 in stages using nitric acid and ammonia.

[0083] Performance Testing: The total impurity content of boehmite powder was 148 ppm, containing a large amount of residual nitrate and sodium ions. The impurities mainly originated from exogenous acid and alkali reagents. The boehmite powder had a D50 of 235 nm, a purity of 99.9852%, and a D90 / D10 ratio of 3.12. It exhibited an extremely wide particle size distribution, with a large number of unevenly sized particles and hard agglomerates. The pH value of the reaction system within a single batch fluctuated by as much as ±1.2 with reaction time, and the relative standard deviation (RSD) of the pH of the reaction system between batches was 6.8%, indicating that the preparation method of this comparative example not only had extensive process control but also poor batch-to-batch repeatability. The single reaction time was as long as 4.5 hours, resulting in only intermittent single-batch production without continuous operation capability. The production process generated a large amount of acid and alkali cleaning wastewater, making it impossible to achieve zero discharge and resulting in poor product consistency.

[0084] Comparative Example 2 The difference from Example 1 is that step S2 is omitted.

[0085] Performance Testing: The pH of the reaction system fluctuated between 4.8 and 8.2, likely due to drastic local acid-base fluctuations caused by temperature differences. The total impurity content of the boehmite powder was 94 ppm, with a purity of 99.9906%, and trace amounts of hydrolysis byproducts remained. The boehmite powder had a D50 of 1.93 nm and a D90 / D10 ratio of 2.15, indicating a significantly widened particle size distribution and the presence of abnormally large particles in some areas. Slight soft agglomeration of the boehmite powder was observed; the relative standard deviation (RSD) of particle size D50 between different batches after 24 hours of continuous operation was 3.2%, indicating a significant decrease in stability. This suggests that the amino acid reversible buffer is the core key to achieving pH stability, low impurities, and a narrow particle size distribution.

[0086] Comparative Example 3 The difference from Example 1 is that step S2 is omitted, and nitric acid and ammonia are used to adjust the pH of the reaction system in real time to maintain it at 5.5~7.5.

[0087] Performance testing: The total impurity content of the boehmite powder was 38 ppm, and a large amount of NO3 was detected. - NH4 + Exogenous ion residues exist. The boehmite powder has a D50 of 185 nm and a D90 / D10 ratio of 1.98, exhibiting a wider particle size distribution than in Examples 1-9. During continuous production, trace amounts of acid and alkali accumulate, easily causing scaling and blockage on the inner walls of the microchannels, limiting the continuous operating time of the equipment. The washing process generates nitrogen-containing wastewater, making it impossible to achieve closed-loop zero-discharge.

[0088] Comparative Example 4 The process is basically the same as in Example 1, except that the three-stage gradient temperature control is omitted in step S3. Specifically, step S3 is as follows: The reactants were transferred into a microchannel reactor with a hydraulic diameter of 200 μm for reaction, and the reaction was carried out continuously at a constant temperature of 180 °C for 40 min.

[0089] Performance testing: The total impurity content of the boehmite powder was 29 ppm. The boehmite powder had a D50 of 130 nm and a D90 / D10 ratio of 2.36, indicating severe mixing of large and small particles and poor morphological regularity. Numerous crystal surface defects significantly reduced powder dispersibility, with a relative standard deviation (RSD) of 4.5% for D50 between different batches, making continuous mass production with narrow particle size distribution and high consistency impossible. The likely cause is that boehmite powder nucleation and crystal growth occur simultaneously, resulting in secondary nucleation.

[0090] Comparative Example 5 The process is basically the same as in Example 1, except that an ultra-high-speed flow microchannel reactor is used, the flow rate of the reaction raw materials is adjusted to 60 L / h, and the material residence time is significantly shortened.

[0091] Performance testing: The total impurity content of the boehmite powder was 20 ppm, the purity was 99.998%, the D50 was 75 nm, the D90 / D10 ratio was 2.05, particle size uniformity failed, the powder crystallinity was low, and the thermal stability and dispersibility were significantly reduced, with a significant increase in batch fluctuations. The possible reasons are insufficient reaction of the raw materials, incomplete crystal growth, and the presence of a large number of amorphous phases and microcrystalline impurities.

[0092] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

[0093] Although preferred embodiments have been described in this specification, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this specification.

[0094] Obviously, those skilled in the art can make various modifications and variations to this specification without departing from its spirit and scope. Therefore, if such modifications and variations fall within the scope of the claims and their equivalents, this specification is also intended to include such modifications and variations.

Claims

1. A method for preparing boehmite, characterized in that, Includes the following steps: An aluminum source and water are mixed to obtain a precursor sol, wherein the aluminum source includes basic aluminum acetate and / or aluminum isopropoxide; Amino acids are added to the precursor sol to obtain a reaction raw material, wherein the pH of the reaction raw material is 5.5~7.5; The reactants were reacted in a microchannel reactor to obtain a boehmite suspension. as well as The boehmite suspension was subjected to solid-liquid separation, washing, and drying to obtain the boehmite.

2. The preparation method according to claim 1, characterized in that, The aluminum source includes basic aluminum acetate and aluminum isopropoxide, and the mass ratio of basic aluminum acetate to aluminum isopropoxide in the aluminum source is (1~2):

1.

3. The preparation method according to claim 1 or 2, characterized in that, The solid-liquid ratio of the aluminum source and water is 1g:(8~15)mL.

4. The preparation method according to claim 3, characterized in that, The purity of the aluminum source is ≥99.95%, and the resistivity of the water is ≥18.5 MΩ·cm.

5. The preparation method according to claim 1, characterized in that, The amino acids include one or more of glycine, alanine, and lysine.

6. The preparation method according to claim 6, characterized in that, The amount of amino acid added is 0.1% to 0.5% of the mass of the precursor sol, and can be selected as 0.2% to 0.3%.

7. The preparation method according to claim 1, characterized in that, The mechanical diameter of the microchannel reactor is 200μm~400μm.

8. The preparation method according to claim 1, characterized in that, The step of reacting the reactants in a microchannel reactor includes a first reaction stage, a second reaction stage, and a third reaction stage performed sequentially. The temperature of the first reaction stage is 110℃~130℃, and the residence time of the first reaction stage is 2min~5min; The temperature of the second reaction stage is 150℃~170℃, and the residence time of the second reaction stage is 3min~8min; The temperature of the third reaction stage is 170℃~190℃, and the residence time of the third reaction stage is 5min~15min.

9. The preparation method according to claim 8, characterized in that, The flow rate of the reaction feedstock is 5 L / h to 50 L / h, and / or the pressure of the reaction does not exceed 1.0 MPa.

10. A boehmite obtained by the preparation method according to any one of claims 1 to 9, characterized in that, The total impurity content of the boehmite is <22ppm, the particle size D50 of the boehmite is 40 nm~100 nm, and the particle size D90 / D10 of the boehmite is ≤1.

4.

11. The application of boehmite as described in claim 10 in lithium battery separators, semiconductor packaging, or grinding and polishing.

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