Preparation method of ultra-large pore pseudo-boehmite

Abstract

The present application belongs to the technical field of pseudo-boehmite preparation, and particularly relates to a preparation method of super-large pore pseudo-boehmite. The method comprises the following steps: S1: uniformly mixing composite aluminum alcohol salt, solvent and dispersant to obtain a mixed solution, and then performing microwave step-by-step hydrolysis, normal-pressure distillation and drying to obtain a hydrolysis product; S2: mixing the hydrolysis product, konjac glucomannan and water, adjusting pH and performing ultrasonic dispersion, and then performing hydrothermal reaction, cooling, centrifugation, washing and drying to obtain an expanded pore product; and S3: performing plasma treatment on the expanded pore product, and then cooling, crushing and sieving to obtain the super-large pore pseudo-boehmite. The product prepared by the method has regular pore structure, high purity and good thermal stability, and the process is green, environmentally friendly, controllable and convenient for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of boehmite preparation technology, specifically relating to a method for preparing ultra-large pore boehmite. Background Technology

[0002] pseudoboehmite (AlOOH) nH2O is the core precursor for the preparation of γ-Al2O3. With its high specific surface area and excellent colloidal solubility, it has become a key basic material in the fields of petrochemicals, environmental catalysis, and new energy materials.

[0003] However, current industrial-scale preparation methods for pseudoboehmite struggle to achieve an effective balance between precise control of pore structure, cost control, and environmental friendliness.

[0004] (1) Carbonation method: Sodium aluminate is used as raw material, and CO2 is introduced to carry out carbonation precipitation. This is one of the mainstream processes in China. The raw materials are readily available and the production cost is low. However, due to the limitations of reaction kinetics, the product has a small pore volume and a wide pore size distribution.

[0005] (2) Precipitation method: Aluminum sulfate and sodium aluminate are co-flowed to form a gel. The reaction conditions are mild and easy to control, and the product has high purity. It is often used in the preparation of catalyst supports. However, the traditional process uses a single pH value to form the gel. Under acidic conditions, the crystal nuclei are uniform, but the pore size is small. Under weakly alkaline conditions, the pore size can be moderately increased, but it is easy to cause crystal nuclei agglomeration, resulting in uneven pore size distribution.

[0006] (3) Aluminum alkoxide method: High-purity aluminum alkoxides are used as raw materials and prepared by hydrolysis and condensation reaction. The product has high purity and regular crystal phase, but the product obtained by this method has small pore size.

[0007] (4) Rapid de-powdering hydration method: Using ρ-alumina as raw material, pseudoboehmite is prepared through hydration reaction. The process is short and no harmful by-products are generated. However, this method lacks precise pore expansion control. The hydration reaction can only achieve crystal phase transformation and cannot effectively control the pore size and distribution.

[0008] Chinese patent application CN1940096A discloses a method for preparing low-sodium boehmite. This method uses primary aluminum or refined high-purity aluminum as raw material, which is washed and dried before reacting with alcohol to generate aluminum alkoxides. After filtering the solid particles through a sieve, the aluminum alkoxides are hydrolyzed, and the resulting alcohol is evaporated to obtain crude boehmite. This method optimizes the traditional aluminum alkoxide refining process, solving the problems of high sodium impurities and cumbersome alkoxide refining. However, the boehmite prepared by this method still has a conventional microporous / mesoporous structure, exhibiting poor thermal stability. After calcination to γ-Al₂O₃, the pore structure is prone to collapse, making it difficult to meet the structural stability requirements of high-end applications. Summary of the Invention

[0009] Existing methods for controlling the pore structure of pseudoboehmite are poor; to address this issue, this invention provides a method for preparing ultra-large pore pseudoboehmite.

[0010] To achieve the objectives of this invention, the following technical solution is adopted:

[0011] This invention provides a method for preparing ultra-large porosilicate boehmite, comprising the following steps:

[0012] S1: Mix the composite aluminum alkoxide, solvent, and dispersant evenly to obtain a mixture; place the mixture in a microwave reactor, control the microwave power to be 200~300W, the temperature to be 50~60℃, and the stirring speed to be 100~150rpm, and add water to carry out the first reaction; increase the microwave power to 400~500W, raise the temperature to 80~90℃, increase the stirring speed to 250~350rpm, continue to add water to carry out the second reaction, distill under normal pressure, and dry to obtain the hydrolysis product;

[0013] S2: Mix the hydrolysate, konjac glucomannan and water evenly, adjust the pH to 7.5-9.0, and ultrasonically disperse for 15-20 minutes to obtain a slurry; subject the slurry to a hydrothermal reaction; cool, centrifuge, wash and dry to obtain the pore-expanding product;

[0014] S3: The expanded pore product is subjected to plasma treatment, cooling, crushing, and sieving to obtain ultra-large porosilicate boehmite.

[0015] By adopting the above technical solutions, step S1 uses a stepwise hydrolysis and microwave-assisted hydrolysis mode. By gradient control of microwave power, temperature, stirring rate and water addition, the controllability of the reaction is improved and crystal agglomeration is effectively avoided. Step S2 uses konjac glucomannan template to assist hydrothermal pore expansion, further regularizing the pore structure, and finally stabilizing the product pore size in the ultra-large pore range, with sufficient pore volume and uniform pore size distribution. Step S3 uses plasma treatment to replace traditional high-temperature calcination and high-temperature hydrothermal treatment, ensuring the thermal stability of the product and reducing industrial production costs.

[0016] Preferably, in step S1, the preparation method of the composite aluminum alkoxide includes the following steps:

[0017] Metallic aluminum, anhydrous isopropanol, anhydrous n-hexanol and catalyst are mixed evenly and heated to 90~115℃ for 12~24h; then silane coupling agent KH-550 is added and the reaction is continued for 2~4h; vacuum distillation and drying are performed to obtain composite aluminum alkoxide.

[0018] By adopting the above technical solution, a composite aluminum alkoxide is prepared by reacting short-chain anhydrous isopropanol and long-chain anhydrous n-hexanol with metallic aluminum. Anhydrous isopropanol can accelerate the reaction rate and ensure that the metallic aluminum is fully dissolved, while anhydrous n-hexanol can slow down the subsequent hydrolysis rate. The synergistic effect of the two facilitates the precise control of subsequent stepwise hydrolysis. The siloxane group of the silane coupling agent KH-550 can form a coordination effect with the aluminum alkoxide, which can not only improve the stability of the composite aluminum alkoxide, but also regulate the growth direction of crystal nuclei during subsequent hydrolysis, reduce grain agglomeration, and improve the crystal stability of boehmite.

[0019] Preferably, the mass ratio of the metallic aluminum, anhydrous isopropanol, anhydrous n-hexanol, catalyst and silane coupling agent KH-550 is (80~100):(300~400):(100~150):(0.08~0.12):(1~3).

[0020] By adopting the above technical solution, the reaction rate is moderate at this ratio, and the yield of composite aluminum alkoxide is high, which provides a guarantee for the subsequent formation of ultraporous structures.

[0021] Preferably, in step S1, the mass ratio of the composite aluminum alkoxide to the solvent is 1:(3~5); the solvent is prepared by mixing isopropanol and cyclohexane in a mass ratio of 1:(1.5~2).

[0022] By adopting the above technical solution, the composite aluminum alkoxide is fully dissolved in the solvent at this ratio, avoiding the problems of aluminum alkoxide agglomeration and uneven hydrolysis reaction. At the same time, isopropanol and cyclohexane are mixed at a mass ratio of 1:(1.5~2). Isopropanol can improve the solubility of the composite aluminum alkoxide, and cyclohexane can inhibit the excessively fast hydrolysis reaction rate. The two work synergistically to provide a stable reaction environment for subsequent stepwise rate-controlled hydrolysis, effectively reducing crystal nucleus agglomeration and resulting in a more uniform pore size distribution, laying the foundation for the formation of regular ultra-large channels.

[0023] Preferably, in step S1, the dispersant is polyethylene glycol 400, and the amount of dispersant used is 0.3% to 0.5% of the total mass of the composite aluminum alkoxide and the solvent.

[0024] By adopting the above technical solution, the hydroxyl groups at both ends of the polyethylene glycol 400 molecular chain can form hydrogen bonds with the hydroxyl groups on the surface of the composite aluminum alkoxide and subsequent hydrolysis products. The hydrophobic segment in the middle is compatible with the mixed solvent and can be effectively adsorbed on the surface of aluminum alkoxide molecules and crystal nuclei, forming steric hindrance, significantly inhibiting crystal nucleus aggregation, and ensuring uniform particle size of hydrolysis products.

[0025] Preferably, in step S1, the molar ratio of water to composite aluminum alkoxide in the first reaction is (3~5):1; and the molar ratio of water to composite aluminum alkoxide in the second reaction is (3~4):1.

[0026] By adopting the above technical solution, the molar ratio of water to composite aluminum alkoxide is controlled stepwise, achieving a gradient regulation of the hydrolysis reaction from slow to fast. The first reaction requires less water, which can slowly initiate the hydrolysis reaction and uniformly form pseudo-boehmite crystal nuclei, avoiding excessively rapid hydrolysis and crystal nuclei agglomeration due to excessive water. The second reaction replenishes water, which can promote further growth of crystal nuclei and guide the initial formation of pores. The stepwise hydrolysis reaction is more controllable, avoiding the problem of wide pore size distribution caused by hydrolysis with a single amount of water.

[0027] Preferably, in step S1, the time for the first reaction is 2-3 hours, and the time for the second reaction is 3-5 hours.

[0028] By adopting the above technical solution, the first reaction of 2-3 hours can ensure the slow hydrolysis of composite aluminum alkoxides, forming uniform and stable crystal nuclei; the second reaction of 3-5 hours can ensure the full growth of crystal nuclei, while avoiding the collapse of channels or excessively large grains due to excessive reaction time. The above reaction time can improve the hydrolysis efficiency while ensuring the crystal phase purity and pore structure regularity of the hydrolysis products, providing a good precursor for subsequent hydrothermal pore expansion.

[0029] Preferably, in step S2, the mass ratio of hydrolysate to water is (8~12):(88~92); the amount of konjac glucomannan used is 2%~5% of the total mass of hydrolysate and water.

[0030] By adopting the above technical solution, the hydrolysis products and water can be uniformly dispersed at this ratio; konjac glucomannan can inhibit the growth of small crystals and guide the formation of regular ultra-large channels through the steric hindrance of its molecular chains, while its hydroxyl groups can form hydrogen bonds with the hydroxyl groups on the surface of boehmite, thereby improving the stability of the channels.

[0031] Preferably, in step S2, the hydrothermal reaction temperature is 140~180℃ and the hydrothermal reaction time is 18~30h.

[0032] By adopting the above technical solution, within this temperature and time range, the dual effects of low-temperature energy saving and high-efficiency hole expansion can be achieved, and the resulting expanded hole product has stable pore size and high pore regularity.

[0033] Preferably, in step S3, the plasma treatment conditions are as follows: argon flow rate is 10~20mL / min, plasma power is 150~250W, treatment temperature is 120~150℃, and treatment time is 30~60min.

[0034] By adopting the above technical solution, plasma treatment can replace high-temperature calcination, which can avoid the collapse of pores caused by high temperature and reduce pore volume loss. The power of 150~250W and the processing time of 30~60min can achieve the full removal of impurities and the activation of the product surface. The activated boehmite surface has more hydroxyl groups, which can further reduce grain agglomeration and improve product dispersibility.

[0035] In summary, the beneficial effects of this invention are:

[0036] 1. This invention broadens the range of hydrolysis rate regulation by using aluminum alkoxides with different chain lengths and combining them with KH-550 silane modification. It also improves the crystal stability of boehmite through the coordination effect of siloxane groups, thus solving the problems of easy agglomeration and easy collapse of pores in traditional products.

[0037] 2. This invention employs a two-step hydrolysis method combined with microwave uniform heating, resulting in low temperature deviation and significantly improved process efficiency and product uniformity.

[0038] 3. This invention uses natural konjac glucomannan as a template agent, which is renewable and biodegradable. At the same time, the steric hindrance of its molecular chain can achieve stable expansion of ultra-large pores, improve pore volume, and balance environmental protection and product performance.

[0039] 4. This invention uses medium-low temperature plasma treatment, which reduces energy consumption and minimizes pore volume loss. At the same time, it can activate the product surface and improve dispersibility. Attached Figure Description

[0040] Figure 1 The XRD diffraction pattern of the ultra-large porosity pseudoboehmite of this invention is shown. Detailed Implementation

[0041] The present invention will be further described below with reference to specific embodiments.

[0042] Unless otherwise specified, the experimental methods used in the following examples and comparative examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples and comparative examples are commercially available.

[0043] Preparation example, preparation of composite aluminum alkoxides

[0044] The aluminum granules in the following preparation examples all underwent the following pretreatment:

[0045] After ultrasonication in an ethanol / deionized water medium for 30 min (ethanol / deionized water = 1:1, v / v), aluminum particles were activated by acid washing with dilute nitric acid for 10 min, washed with deionized water until neutral, and then vacuum dried for later use.

[0046] Preparation Example 1

[0047] The preparation method of the composite aluminum alkoxide in this example includes the following specific steps:

[0048] 95g of metallic aluminum granules, 400g of anhydrous isopropanol, 130g of anhydrous n-hexanol and 0.1g of aluminum trichloride catalyst were added to a reaction vessel, heated to 115℃ and reacted for 20h; then 3g of silane coupling agent KH-550 was added and the reaction was continued for 3h; the mixture was then distilled under reduced pressure and placed in a vacuum drying oven and dried at 60℃ for 12h to obtain a composite aluminum alkoxide.

[0049] Preparation Example 2

[0050] The preparation method of the composite aluminum alkoxide in this example includes the following specific steps:

[0051] 85g of aluminum granules, 350g of anhydrous isopropanol, 100g of anhydrous n-hexanol and 0.12g of aluminum trichloride catalyst were added to a reaction vessel, heated to 95℃ and reacted for 24h; then 1g of silane coupling agent KH-550 was added and the reaction was continued for 2h; the mixture was then distilled under reduced pressure and placed in a vacuum drying oven and dried at 60℃ for 12h to obtain a composite aluminum alkoxide.

[0052] Preparation Example 3

[0053] The preparation method of the composite aluminum alkoxide in this example includes the following specific steps:

[0054] 80g of aluminum granules, 320g of anhydrous isopropanol, 100g of anhydrous n-hexanol and 0.08g of aluminum trichloride catalyst were added to a reaction vessel, heated to 90℃ and reacted for 18h; then 1.5g of silane coupling agent KH-550 was added and the reaction continued for 3h; the mixture was then distilled under reduced pressure and placed in a vacuum drying oven and dried at 60℃ for 12h to obtain a composite aluminum alkoxide.

[0055] Preparation Example 4

[0056] The preparation method of the composite aluminum alkoxide in this example includes the following specific steps:

[0057] 90g of aluminum granules, 400g of anhydrous isopropanol, 150g of anhydrous n-hexanol and 0.12g of aluminum trichloride catalyst were added to a reaction vessel, heated to 110℃ and reacted for 15h; then 2g of silane coupling agent KH-550 was added and the reaction was continued for 4h; the mixture was then distilled under reduced pressure and placed in a vacuum drying oven and dried at 60℃ for 12h to obtain a composite aluminum alkoxide.

[0058] Example

[0059] Example 1

[0060] The preparation method of ultra-large porous pseudo-boehmite in this embodiment includes the following specific steps:

[0061] S1: Mix 50g of the composite aluminum alkoxide prepared in Preparation Example 4 with 220g of solvent, add 1.08g of dispersant polyethylene glycol-400, and stir for 30min to obtain a mixture; place the mixture in a microwave reactor, control the microwave power at 280W, the temperature at 55℃, and the stirring rate at 140rpm, add water dropwise for the first reaction, the molar ratio of water to composite aluminum alkoxide is 5:1, and react for 3h; increase the microwave power to 420W, raise the temperature to 90℃, increase the stirring rate to 250rpm, and continue to add water dropwise for the second reaction, the molar ratio of water to composite aluminum alkoxide is 4:1, and react for 4h; after hydrolysis, distill under normal pressure, place in a vacuum drying oven, and dry at 80℃ for 12h to obtain the hydrolysis product; the solvent is prepared by mixing isopropanol and cyclohexane in a mass ratio of 1:1.5;

[0062] S2: Mix 10g of hydrolysis product with 90g of deionized water, then add 3.5g of konjac glucomannan, stir for 20min, adjust pH to 8.0, and ultrasonically disperse for 20min; transfer the slurry to an autoclave, control the temperature at 160℃, and hydrothermally react for 30h; after hydrothermal reaction, allow it to cool naturally to room temperature, centrifuge at 3000rpm for 10min, wash three times with deionized water, and place the centrifuged solid product in a vacuum drying oven and dry at 80℃ for 10h to obtain the pore-expanding product;

[0063] S3: The expanded pore product is placed in a plasma reactor for plasma treatment. Argon gas is introduced at a flow rate of 20 mL / min, the plasma power is controlled at 250 W, the treatment time is 60 min, and the reaction temperature is controlled at 150℃. After the plasma treatment is completed, the product is cooled to room temperature, pulverized, and passed through a 200-mesh sieve to obtain ultra-large porosity pseudoboehmite.

[0064] Figure 1 The XRD diffraction pattern of the obtained ultra-large porous pseudoboehmite is shown below; Figure 1 It can be seen that the product has pseudoboehmite characteristic peaks around 14°, 28°, 38°, and 49°, indicating that the product is pseudoboehmite.

[0065] Example 2

[0066] The preparation method of ultra-large porous pseudo-boehmite in this embodiment includes the following specific steps:

[0067] S1: Mix 50g of the composite aluminum alkoxide prepared in Preparation Example 1 with 250g of solvent, add 1.05g of dispersant polyethylene glycol 400, and stir for 30min to obtain a mixture; place the mixture in a microwave reactor, control the microwave power at 250W, the temperature at 60℃, and the stirring speed at 130rpm, add water dropwise for the first reaction, the molar ratio of water to composite aluminum alkoxide is 3:1, and react for 3h; increase the microwave power to 500W, raise the temperature to 80℃, increase the stirring speed to 300rpm, and continue to add water dropwise for the second reaction, the molar ratio of water to composite aluminum alkoxide is 4:1, and react for 4h; after hydrolysis, distill under normal pressure, place in a vacuum drying oven, and dry at 80℃ for 12h to obtain the hydrolysis product; the solvent is prepared by mixing isopropanol and cyclohexane in a mass ratio of 1:1.5;

[0068] S2: Mix 8g of hydrolysis product with 90g of deionized water, then add 4.5g of konjac glucomannan, stir for 20min, adjust pH to 7.5, and ultrasonically disperse for 20min; transfer the slurry to an autoclave, control the temperature at 140℃, and hydrothermally react for 18h; after hydrothermal reaction, allow it to cool naturally to room temperature, centrifuge at 3000rpm for 10min, wash three times with deionized water, and place the centrifuged solid product in a vacuum drying oven and dry at 80℃ for 10h to obtain the pore-expanding product;

[0069] S3: The expanded pore product is placed in a plasma reactor for plasma treatment. Argon gas is introduced at a flow rate of 20 mL / min, the plasma power is controlled at 250 W, the treatment time is 30 min, and the reaction temperature is controlled at 140℃. After the plasma treatment is completed, the product is cooled to room temperature, crushed, and passed through a 200-mesh sieve to obtain ultra-large porosity pseudoboehmite.

[0070] Example 3

[0071] The preparation method of ultra-large porous pseudo-boehmite in this embodiment includes the following specific steps:

[0072] S1: Mix 50g of the composite aluminum alkoxide prepared in Preparation Example 2 with 150g of solvent, add 0.8g of dispersant polyethylene glycol 400, and stir for 30min to obtain a mixture; place the mixture in a microwave reactor, control the microwave power at 300W, the temperature at 50℃, and the stirring speed at 110rpm, add water dropwise for the first reaction, the molar ratio of water to composite aluminum alkoxide is 5:1, and react for 2h; increase the microwave power to 450W, raise the temperature to 80℃, increase the stirring speed to 320rpm, and continue to add water dropwise for the second reaction, the molar ratio of water to composite aluminum alkoxide is 4:1, and react for 5h; after hydrolysis, distill under normal pressure, place in a vacuum drying oven, and dry at 80℃ for 12h to obtain the hydrolysis product; the solvent is prepared by mixing isopropanol and cyclohexane in a mass ratio of 1:2;

[0073] S2: Mix 8g of hydrolysis product with 88g of deionized water, then add 2.88g of konjac glucomannan, stir for 20min, adjust pH to 8.0, and ultrasonically disperse for 15min; transfer the slurry to an autoclave, control the temperature at 140℃, and perform hydrothermal reaction for 28h; after hydrothermal reaction, allow it to cool naturally to room temperature, centrifuge at 3000rpm for 10min, wash three times with deionized water, and place the centrifuged solid product in a vacuum drying oven to dry at 80℃ for 10h to obtain the pore-expanding product;

[0074] S3: The expanded pore product is placed in a plasma reactor for plasma treatment. Argon gas is introduced at a flow rate of 20 mL / min, the plasma power is controlled at 150 W, the treatment time is 40 min, and the reaction temperature is controlled at 150℃. After the plasma treatment is completed, the product is cooled to room temperature, crushed, and passed through a 200-mesh sieve to obtain ultra-large porosity pseudoboehmite.

[0075] Example 4

[0076] The preparation method of ultra-large porous pseudo-boehmite in this embodiment includes the following specific steps:

[0077] S1: Mix 50g of the composite aluminum alkoxide prepared in Preparation Example 4 with 200g of solvent, add 1.25g of dispersant polyethylene glycol 400, and stir for 30min to obtain a mixture; place the mixture in a microwave reactor, control the microwave power at 200W, the temperature at 55℃, and the stirring speed at 100rpm, add water dropwise for the first reaction, the molar ratio of water to composite aluminum alkoxide is 4:1, and react for 2h; increase the microwave power to 400W, raise the temperature to 85℃, increase the stirring speed to 350rpm, and continue to add water dropwise for the second reaction, the molar ratio of water to composite aluminum alkoxide is 4:1, and react for 3h; after hydrolysis, distill under normal pressure, place in a vacuum drying oven, and dry at 80℃ for 12h to obtain the hydrolysis product; the solvent is prepared by mixing isopropanol and cyclohexane in a mass ratio of 1:2;

[0078] S2: Mix 10g of hydrolysis product with 92g of deionized water, then add 2.4g of konjac glucomannan, stir for 20min, adjust pH to 9.0, and ultrasonically disperse for 15min; transfer the slurry to an autoclave, control the temperature at 180℃, and hydrothermally react for 20h; after hydrothermal reaction, allow it to cool naturally to room temperature, centrifuge at 3000rpm for 10min, wash three times with deionized water, and place the centrifuged solid product in a vacuum drying oven and dry at 80℃ for 10h to obtain the pore-expanding product;

[0079] S3: The expanded pore product is placed in a plasma reactor for plasma treatment. Argon gas is introduced at a flow rate of 15 mL / min, the plasma power is controlled at 200 W, the treatment time is 60 min, and the reaction temperature is controlled at 120℃. After the plasma treatment is completed, the product is cooled to room temperature, crushed, and passed through a 200-mesh sieve to obtain ultra-large porosity pseudoboehmite.

[0080] Example 5

[0081] The preparation method of ultra-large porous pseudo-boehmite in this embodiment includes the following specific steps:

[0082] S1: Mix 50g of the composite aluminum alkoxide prepared in Preparation Example 1 with 250g of solvent, add 1.45g of dispersant polyethylene glycol 400, and stir for 30min to obtain a mixture; place the mixture in a microwave reactor, control the microwave power at 300W, the temperature at 55℃, and the stirring rate at 150rpm, add water dropwise for the first reaction, the molar ratio of water to composite aluminum alkoxide is 5:1, and react for 3h; increase the microwave power to 400W, raise the temperature to 90℃, increase the stirring rate to 250rpm, and continue to add water dropwise for the second reaction, the molar ratio of water to composite aluminum alkoxide is 3:1, and react for 5h; after hydrolysis, distill under normal pressure, place in a vacuum drying oven, and dry at 80℃ for 12h to obtain the hydrolysis product; the solvent is prepared by mixing isopropanol and cyclohexane in a mass ratio of 1:2;

[0083] S2: Mix 12g of hydrolysis product with 88g of deionized water, add 4g of konjac glucomannan, stir for 20min, adjust pH to 8.0, and ultrasonically disperse for 15min; transfer the slurry to an autoclave, control the temperature at 180℃, and hydrothermally react for 24h; after hydrothermal reaction, allow it to cool naturally to room temperature, centrifuge at 3000rpm for 10min, wash three times with deionized water, and place the centrifuged solid product in a vacuum drying oven and dry at 80℃ for 10h to obtain the pore-expanding product;

[0084] S3: The expanded pore product is placed in a plasma reactor for plasma treatment. Argon gas is introduced at a flow rate of 20 mL / min, the plasma power is controlled at 250 W, the treatment time is 30 min, and the reaction temperature is controlled at 150℃. After the plasma treatment is completed, the product is cooled to room temperature, crushed, and passed through a 200-mesh sieve to obtain ultra-large porosity pseudoboehmite.

[0085] Comparative Example 1

[0086] The difference from Example 1 is that the preparation method of this comparative example of boehmite uses commercially available aluminum isopropoxide instead of the composite aluminum alkoxide used in step S1, while the remaining steps and process parameters are the same as in Example 1.

[0087] Comparative Example 2

[0088] The difference from Example 1 is that the preparation method of this comparative example of pseudoboehmite, step S1 is as follows, and the remaining steps and process parameters are the same as in Example 1:

[0089] S1: Mix 50g of composite aluminum alkoxide with 250g of solvent, add 1.5g of dispersant polyethylene glycol 400, stir for 30min to obtain a mixture; place the mixture in a microwave reactor, control the microwave power to be 350W, the temperature to be 75℃, the stirring speed to be 200rpm, add water dropwise at once, the total molar ratio of water to composite aluminum alkoxide is 8:1, react for 8h; after hydrolysis, distill under normal pressure, place in a vacuum drying oven, dry at 80℃ for 12h to obtain the hydrolysis product; the solvent is prepared by mixing isopropanol and cyclohexane in a mass ratio of 1:2.

[0090] Comparative Example 3

[0091] The difference from Example 1 is that in the preparation method of this comparative example of boehmite, konjac glucomannan is not added in step S2, while the remaining steps and process parameters are the same as in Example 1.

[0092] Comparative Example 4

[0093] The difference from Example 1 is that the preparation method of this comparative example of boehmite, step S3 is as follows, while the remaining steps and process parameters are completely consistent with those of Example 1:

[0094] S3: Place the expanded pore product in a muffle furnace, calcine at 350℃ for 3 hours, cool to room temperature, pulverize, and pass through a 200-mesh sieve to obtain pseudoboehmite.

[0095] Related performance tests

[0096] The performance of the macroporous pseudoboehmite prepared in Examples 1-5 and Comparative Examples 1-4 was measured, and the test results are shown in Table 1.

[0097] Table 1 Test Results

[0098]

[0099] As shown in Table 1, the ultra-large porosity pseudo-boehmite prepared in Examples 1-5 of this invention has an average pore diameter of ≥20 nm and a pore volume of ≥1.5 cm³. 3 / g, specific surface area ≥350m² 2 / g, with excellent thermal stability; the products of Comparative Examples 1-4 all have defects in performance, with low average pore size, small pore volume and poor thermal stability.

[0100] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing ultra-large porous boehmite, characterized in that, Includes the following steps: S1: The composite aluminum alkoxide, solvent, and dispersant are mixed evenly to obtain a mixture; the mixture is placed in a microwave reactor, and the microwave power is controlled at 200~300W, the temperature at 50~60℃, and the stirring speed at 100~150rpm. Water is added for a first reaction; the microwave power is increased to 400~500W, the temperature is raised to 80~90℃, and the stirring speed is increased to 250~350rpm. Water is added again for a second reaction. The mixture is then distilled under normal pressure and dried to obtain the hydrolysis product. The preparation method of the composite aluminum alkoxide includes the following steps: metallic aluminum, anhydrous isopropanol, anhydrous n-hexanol, and catalyst are mixed evenly and heated to 90~115℃ for 12~24h; then silane coupling agent KH-550 is added, and the reaction is continued for 2~4h; the mixture is then distilled under reduced pressure and dried to obtain the composite aluminum alkoxide; the dispersant is polyethylene glycol 400, and the amount of dispersant is 0.3%~0.5% of the total mass of the composite aluminum alkoxide and the solvent. S2: Mix the hydrolysate, konjac glucomannan and water evenly, adjust the pH to 7.5~9.0, and ultrasonically disperse for 15~20 min to obtain a slurry; subject the slurry to a hydrothermal reaction; Cool, centrifuge, wash, and dry to obtain the expanded pore product; S3: The expanded pore product is subjected to plasma treatment, cooled, crushed, and sieved to obtain ultra-large porosilicate boehmite; the plasma treatment conditions are as follows: argon flow rate is 10~20mL / min, plasma power is 150~250W, treatment temperature is 120~150℃, and treatment time is 30~60min.

2. The method for preparing a macroporous pseudoboehmite according to claim 1, characterized in that, The mass ratio of the metallic aluminum, anhydrous isopropanol, anhydrous n-hexanol, catalyst and silane coupling agent KH-550 is (80~100):(300~400):(100~150):(0.08~0.12):(1~3).

3. The method for preparing a macroporous pseudoboehmite according to claim 1, characterized in that, The mass ratio of the composite aluminum alkoxide to the solvent is 1:(3~5); the solvent is prepared by mixing isopropanol and cyclohexane in a mass ratio of 1:(1.5~2).

4. The method for preparing a macroporous pseudoboehmite according to claim 1, characterized in that, In step S1, the molar ratio of water to composite aluminum alkoxide in the first reaction is (3~5):1; and the molar ratio of water to composite aluminum alkoxide in the second reaction is (3~4):

1.

5. The method for preparing a macroporous pseudoboehmite according to claim 1, characterized in that, In step S1, the time for the first reaction is 2-3 hours; the time for the second reaction is 3-5 hours.

6. The method for preparing a macroporous pseudoboehmite according to claim 1, characterized in that, In step S2, the mass ratio of hydrolysis product to water is (8~12):(88~92); the amount of konjac glucomannan used is 2%~5% of the total mass of hydrolysis product and water.

7. The method for preparing a macroporous pseudoboehmite according to claim 1, characterized in that, In step S2, the hydrothermal reaction temperature is 140~180℃ and the hydrothermal reaction time is 18~30h.

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