Large-specific-surface-area high-purity boehmite microspheres and alumina microspheres as well as preparation and application thereof

Abstract

The invention discloses large-specific-surface-area high-purity boehmite microspheres and alumina microspheres and preparation and application thereof, and relates to the technical field of inorganic materials.Water is added into an aluminum source to prepare a saturated aluminum solution, alkali is added to adjust the pH value of the aluminum solution, and a mixed solution is obtained; carrying out hydrothermal reaction on the mixed solution, and adding a small amount of aluminum source to carry out secondary hydrothermal reaction after the reaction is finished; after the secondary hydrothermal reaction is finished, cleaning and drying a product to obtain boehmite microspheres; and roasting the boehmite microspheres at a high temperature to obtain the alumina microspheres. The prepared boehmite microspheres and alumina microspheres have the characteristics of high sphericity, large specific surface area, high purity and the like, and can be applied to the fields of adsorbents, catalyst carriers, alumina ceramic materials and the like.

Description

Technical Field

[0001] The invention relates to the technical field of inorganic materials, and in particular to high-purity boehmite microspheres and alumina microspheres with large specific surface areas, and preparation and application thereof. Background Art

[0002] Boehmite and alumina are both aluminum compounds with certain hardness and corrosion resistance and are non-toxic in themselves. Boehmite and alumina with large specific surface area and porous structure are often used in fields such as adsorbents and catalyst carriers.

[0003] Patent CN102910654A discloses a method for preparing fibrous boehmite with large specific surface area and large pore volume. The method comprises reacting a sodium aluminate solution with an aluminum sulfate solution, aging, crystallizing, washing and drying to obtain fibrous boehmite with a specific surface area of ​​300 to 500 m 2 / g. This method is simple to operate and easy to realize industrial production, but the impurity sodium content is high, the removal cost is high, and it is not conducive to the stability of the product.

[0004] Patent CN102500309A discloses a porous basic aluminum carbonate and porous alumina balls and their preparation methods and applications. Aluminum nitrate (or aluminum isopropoxide) and urea are used as raw materials, and a porous basic aluminum carbonate with a large specific surface area is prepared by microwave heating, and then nano-scale porous alumina is obtained by roasting. The prepared aluminum carbonate and alumina are used to adsorb arsenic ions and fluoride ions, and both have good adsorption effects. However, the microwave heating process has high requirements for equipment and is difficult to achieve industrial mass production, which limits this process (for example, industrial metal reactors will shield microwaves).

[0005] Patent CN106882829A discloses a method for preparing an ultra-high specific surface area alumina material, which uses an organic base and metal aluminum to react to form aluminum salt, adds a template, spray-dries into particles, and then roasts them into gamma alumina, with a specific surface area greater than 550m 2 Although this method effectively avoids the introduction of inorganic metal ions during the preparation process, making the product have high purity, the involvement of organic templates will cause certain environmental pollution and increase costs.

[0006] Patent CN108258231A discloses a method for preparing porous alumina microspheres, which uses polyvinyl pyrrolidone, ammonium aluminum carbonate and sodium chloride as raw materials for hydrothermal reaction, and the product is washed with ethanol and then roasted to obtain porous alumina microspheres. The product has a through-hole structure, good firmness and bearing pressure, and a large specific surface area, but a large amount of organic matter is added during the preparation process, which makes the cost high, and contains impurity sodium ions.

[0007] Although the large specific surface area boehmite and alumina products synthesized in the above patents can obtain large specific surface area or porous structure, they have problems such as containing impurity ions, high pollution and high cost. Summary of the invention

[0008] The technical problem to be solved by the present invention is to provide a method for preparing high-purity boehmite microspheres and alumina microspheres with large specific surface area. The obtained boehmite microspheres and alumina microspheres have the characteristics of high sphericity, large specific surface area, high purity, etc., and can be applied to the fields of adsorbents, catalyst carriers and alumina ceramic materials.

[0009] The technical problem to be solved by the present invention is achieved by adopting the following technical solutions:

[0010] The first object of the present invention is to provide a method for preparing boehmite microspheres, comprising the following steps:

[0011] (1) adding water to an aluminum source to prepare a saturated aluminum solution, and adding alkali to adjust the pH value of the aluminum solution to obtain a mixed solution;

[0012] (2) subjecting the mixed solution to a hydrothermal reaction, and after the reaction is completed, adding a small amount of aluminum source to conduct a secondary hydrothermal reaction;

[0013] (3) After the secondary hydrothermal reaction is completed, the product is washed and dried to obtain boehmite microspheres.

[0014] The second object of the present invention is to provide boehmite microspheres prepared by the above-mentioned preparation method.

[0015] The specific surface area of ​​the boehmite microspheres is 200 to 400 m 2 / g, the morphology is a spherical porous / mesoporous structure, the pore size is 10-20nm, the ball diameter is 5-10μm, and the purity is ≥99.9%.

[0016] The third object of the present invention is to provide a method for preparing alumina microspheres, wherein the boehmite microspheres are calcined at a high temperature to obtain alumina microspheres.

[0017] The fourth object of the present invention is to provide alumina microspheres prepared by the aforementioned preparation method.

[0018] The specific surface area of ​​the alumina microspheres is 300 to 500 m 2 / g, the morphology is a spherical porous structure, the pore size is 20-80nm, the ball diameter is 5-10μm, and the purity is ≥99.9%.

[0019] The fifth object of the present invention is to provide the application of the aforementioned boehmite microspheres and alumina microspheres in the fields of adsorbents, catalyst carriers and alumina ceramic materials.

[0020] The beneficial effects of the present invention are:

[0021] (1) The present invention uses a saturated aluminum solution and performs two hydrothermal reactions. During the reaction process, the crystals are self-assembled and grow outward on the entire surface at the same time, thereby forming spherical boehmite. The alumina formed after high-temperature calcination inherits the shape of boehmite well and becomes spherical alumina. At the same time, due to the dehydration effect, the internal voids of the alumina spheres are connected, thereby further increasing the specific surface area, and finally obtaining alumina microspheres with a large specific surface area.

[0022] (2) The present invention prepares boehmite and alumina products with spherical morphology and porous structure without adding any template, pore-forming agent and dispersant, which has low production cost, does not pollute the environment, and is conducive to industrial production.

[0023] (3) The present invention improves the purity of boehmite itself by a hydrothermal method, and in subsequent operations, only simple cleaning is required to obtain a boehmite product with a purity of >99.9%.

[0024] (4) The boehmite and alumina prepared by the present invention have large specific surface area and high sphericity. Their porous structure and alumina characteristics give them high adsorption capacity and good corrosion resistance. They can maintain a stable structure under different acidic and alkaline conditions and have good application prospects in the fields of adsorbents, catalyst carriers and alumina ceramic materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a low-magnification SEM image of the boehmite microspheres in Example 1;

[0026] Figure 2 This is a high-magnification SEM image of the surface of the boehmite microspheres in Example 1;

[0027] Figure 3 is a low-magnification SEM image of the alumina microspheres in Example 1;

[0028] Figure 4 This is a high-magnification SEM image of the surface of the alumina microspheres in Example 1;

[0029] Figure 5 is a low-magnification SEM image of the boehmite microspheres in Example 2;

[0030] Figure 6 This is a high-magnification SEM image of the surface of the boehmite microspheres in Example 2;

[0031] Figure 7 is a low-magnification SEM image of the alumina microspheres in Example 2;

[0032] Figure 8 This is a high-magnification SEM image of the surface of the alumina microspheres in Example 2;

[0033] Fig. 9 is a low-magnification SEM image of the boehmite microspheres in Example 3;

[0034] Fig.10 This is a high-magnification SEM image of the surface of the boehmite microspheres in Example 3;

[0035] Fig.11 is a low-magnification SEM image of the alumina microspheres in Example 3;

[0036] Fig.12 This is a high-magnification SEM image of the surface of the alumina microspheres in Example 3;

[0037] Fig.13 is a SEM image of boehmite particles in Comparative Example 1;

[0038] Fig.14 This is the SEM image of the aluminum oxide particles in Comparative Example 1. DETAILED DESCRIPTION

[0039] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below in conjunction with specific embodiments and diagrams.

[0040] The present invention provides a method for preparing boehmite microspheres, comprising the following steps:

[0041] (1) adding water to an aluminum source to prepare a saturated aluminum solution, and adding alkali to adjust the pH value of the aluminum solution to obtain a mixed solution;

[0042] (2) subjecting the mixed solution to a hydrothermal reaction, and after the reaction is completed, adding a small amount of aluminum source to conduct a secondary hydrothermal reaction;

[0043] (3) After the secondary hydrothermal reaction is completed, the product is washed and dried to obtain boehmite microspheres.

[0044] Furthermore, the aluminum source includes but is not limited to at least one of inorganic aluminum sources such as aluminum nitrate, aluminum sulfate and aluminum chloride.

[0045] Furthermore, the base includes but is not limited to at least one of inorganic bases or organic bases such as ammonia water, urea, ammonium carbonate, and ammonium bicarbonate.

[0046] Furthermore, the pH value of the mixed solution is 7-10.

[0047] Furthermore, the reaction temperature of the hydrothermal reaction is 140-220° C., and the reaction time is 4-10 hours.

[0048] Furthermore, the amount of the aluminum source used in step (2) is 1 / 5 to 1 / 3 of the mass of the aluminum source used in step (1).

[0049] Furthermore, the reaction temperature of the secondary hydrothermal reaction is 150-200° C., and the reaction time is 1-5 hours.

[0050] The present invention provides boehmite microspheres prepared by the above-mentioned preparation method.

[0051] The specific surface area of ​​the boehmite microspheres is 200 to 400 m 2 / g, the morphology is a spherical porous / mesoporous structure, the pore size is 10-20nm, the ball diameter is 5-10μm, and the purity is ≥99.9%.

[0052] The present invention also provides a method for preparing alumina microspheres, wherein the boehmite microspheres are calcined at a high temperature to obtain alumina microspheres.

[0053] The calcination temperature is 300-700° C. and the calcination time is 3-5 hours.

[0054] The invention obtains alumina by high-temperature calcining boehmite. The alumina inherits the spherical morphology of the precursor boehmite and has a large specific surface area and a porous structure.

[0055] The present invention also provides alumina microspheres prepared by the above-mentioned preparation method.

[0056] The specific surface area of ​​the alumina microspheres is 300 to 500 m 2 / g, the morphology is a spherical porous structure, the pore size is 20-80nm, the ball diameter is 5-10μm, and the purity is ≥99.9%.

[0057] The present invention also provides the application of the aforementioned boehmite microspheres and alumina microspheres in the fields of adsorbents, catalyst carriers and alumina ceramic materials.

[0058] Example 1

[0059] (1) Aluminum chloride and water are mixed and dissolved to saturation, and ammonium carbonate is added to adjust the pH value of the solution to 8.5 to obtain a mixed solution.

[0060] (2) Add the mixed solution into a reactor, the volume of the mixed solution being 80% of the volume of the reactor, and heat it to 160° C. at a heating rate of 2° C. / min for hydrothermal reaction for 1 h. After natural cooling, add aluminum chloride accounting for 1 / 3 of the mass of aluminum chloride in step (1), stir evenly, and then heat it to 180° C. at a heating rate of 5° C. / min for hydrothermal reaction for 4 h.

[0061] (3) After the reaction is completed, the boehmite microspheres are washed with deionized water and dried to obtain boehmite microspheres.

[0062] (4) The boehmite microspheres are calcined at 500°C for 5 hours to obtain alumina microspheres.

[0063] Figure 1 is a low-magnification SEM image of the boehmite microspheres in Example 1. Figure 1 It can be seen that the boehmite prepared in Example 1 is spherical, has a particle size of 5 to 10 μm, and has good dispersibility.

[0064] Figure 2 This is a high-magnification SEM image of the surface of the boehmite microspheres in Example 1. Figure 2 It can be seen that the boehmite spheres prepared in Example 1 have pores on their surface, and the pore diameters are about 10 to 20 nm.

[0065] Figure 3 is a low-magnification SEM image of the alumina microspheres in Example 1. Figure 3 It can be seen that the alumina prepared in Example 1 is spherical, has a particle size of 5 to 10 μm, and has good dispersibility.

[0066] Figure 4 This is a high-magnification SEM image of the surface of the alumina microspheres in Example 1. Figure 4 It can be seen that the alumina spheres prepared in Example 1 have pores on their surface, and the pore diameters are about 60 to 80 nm.

[0067] Example 2

[0068] (1) Aluminum nitrate and water are mixed and dissolved to saturation, and ammonium carbonate is added to adjust the pH value of the solution to 8.0 to obtain a mixed solution.

[0069] (2) Add the mixed solution into a reactor, the volume of the mixed solution being 80% of the volume of the reactor, and heat it to 160° C. at a heating rate of 1° C. / min for hydrothermal reaction for 1 h. After natural cooling, add aluminum nitrate accounting for 1 / 3 of the mass of aluminum nitrate in step (1), stir evenly, and then heat it to 190° C. at a heating rate of 4° C. / min for hydrothermal reaction for 4 h.

[0070] (3) After the reaction is completed, the boehmite microspheres are washed with deionized water and dried to obtain boehmite microspheres.

[0071] (4) The boehmite microspheres are calcined at 400°C for 4 hours to obtain alumina microspheres.

[0072] Figure 5 is a low-magnification SEM image of the boehmite microspheres in Example 2. Figure 5 It can be seen that the boehmite prepared in Example 2 is spherical, with a particle size of 5 to 10 μm and good dispersibility.

[0073] Figure 6 This is a high-magnification SEM image of the surface of the boehmite microspheres in Example 2. Figure 6 It can be seen that the boehmite spheres prepared in Example 2 have pores on their surface, and the pore diameters are about 10 to 20 nm.

[0074] Figure 7is a low-magnification SEM image of the alumina microspheres in Example 2. Figure 7 It can be seen that the alumina prepared in Example 2 is spherical, has a particle size of 5 to 10 μm, and has good dispersibility.

[0075] Figure 8 This is a high-magnification SEM image of the surface of the alumina microspheres in Example 2. Figure 8 It can be seen that the alumina spheres prepared in Example 2 have pores on their surfaces, and the pore diameters are about 40 to 60 nm.

[0076] Example 3

[0077] (1) Aluminum sulfate and water are mixed and dissolved to saturation, and ammonium carbonate is added to adjust the pH value of the solution to 8.0 to obtain a mixed solution.

[0078] (2) Add the mixed solution into the reactor, the volume of the mixed solution is 75% of the volume of the reactor, heat it to 150°C at a heating rate of 2°C / min, and perform hydrothermal reaction for 1.5h. After natural cooling, add aluminum sulfate accounting for 1 / 4 of the mass of aluminum sulfate in step (1), stir evenly, and then heat it to 190°C at a heating rate of 7°C / min, and perform hydrothermal reaction for 3h.

[0079] (3) After the reaction is completed, the boehmite microspheres are washed with deionized water and dried to obtain boehmite microspheres.

[0080] (4) The boehmite microspheres are calcined at 550°C for 5 hours to obtain alumina microspheres.

[0081] Fig. 9 is a low-magnification SEM image of the boehmite microspheres in Example 3. Fig. 9 It can be seen that the boehmite prepared in Example 3 is spherical, has a particle size of 5 to 10 μm, and has good dispersibility.

[0082] Fig.10 This is a high-magnification SEM image of the surface of the boehmite microspheres in Example 3. Fig.10 It can be seen that the boehmite spheres prepared in Example 3 have pores on their surfaces, and the pore diameters are about 10 to 20 nm.

[0083] Fig.11 is a low-magnification SEM image of the alumina microspheres in Example 3. Fig.11 It can be seen that the alumina prepared in Example 3 is spherical, has a particle size of 5 to 10 μm, and has good dispersibility.

[0084] Fig.12 This is a high-magnification SEM image of the surface of the alumina microspheres in Example 3. Fig.12 It can be seen that the alumina spheres prepared in Example 3 have pores on their surfaces, and the pore diameters are about 60 to 80 nm.

[0085] Comparative Example 1

[0086] The method of Example 1 is followed, except that the aluminum source is added in one step instead of in two steps.

[0087] (1) Aluminum chloride and water are mixed and dissolved until saturated, and ammonium carbonate is added to adjust the pH value of the solution to 8.5, and then a certain amount of aluminum chloride is added, the mass of the aluminum chloride added for the second time is 1 / 3 of the mass of the aluminum chloride added for the first time, and the mixture is stirred evenly to obtain a mixed solution.

[0088] (2) The mixed solution was added into the reactor, the volume of the mixed solution being 80% of the volume of the reactor, and the temperature was raised to 180°C at a heating rate of 5°C / min for hydrothermal reaction for 4 hours.

[0089] (3) After the reaction is completed, the particles are washed with deionized water and dried to obtain boehmite particles.

[0090] (4) The boehmite microspheres are calcined at 500° C. for 5 h to obtain alumina particles.

[0091] Fig.13 is a SEM image of boehmite particles in Comparative Example 1. Fig.13 It can be seen that the boehmite particles prepared in Comparative Example 1 are mostly hedgehog-shaped.

[0092] Fig.14 is a SEM image of the alumina particles in Comparative Example 1. Fig.14 It can be seen that the aluminum oxide particles prepared in Comparative Example 1 have irregular morphology.

[0093] The specific surface area, purity and spheroidization rate of the products prepared in Examples 1 to 3 and Comparative Example 1 were tested. The results are shown in Table 1.

[0094] Table 1

[0095]

[0096] It can be seen from Table 1 that the boehmite microspheres and alumina microspheres prepared in Examples 1 to 3 have the characteristics of large specific surface area, high purity and high spheroidization rate, and adding aluminum source in batches for two hydrothermal reactions can greatly increase the specific surface area and spheroidization rate of boehmite and alumina.

[0097] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for preparing boehmite microspheres, characterized in that: The following steps are involved: (1) adding water to an aluminum source to prepare a saturated aluminum solution, and adding alkali to adjust the pH value of the aluminum solution to obtain a mixed solution; (2) subjecting the mixed solution to a hydrothermal reaction, and after the reaction is completed, adding a small amount of aluminum source to conduct a secondary hydrothermal reaction; (3) After the secondary hydrothermal reaction is completed, the product is washed and dried to obtain boehmite microspheres.

2. The preparation method according to claim 1, characterized in that: The aluminum source is at least one of aluminum nitrate, aluminum sulfate and aluminum chloride; Preferably, the base is at least one of ammonia water, urea, ammonium carbonate and ammonium bicarbonate; Preferably, the pH value of the mixed solution is 7-10.

3. The preparation method according to claim 1, characterized in that: The reaction temperature of the hydrothermal reaction is 140-220°C, and the reaction time is 4-10h; Preferably, the amount of the aluminum source in step (2) is 1 / 5 to 1 / 3 of the mass of the aluminum source in step (1); Preferably, the reaction temperature of the secondary hydrothermal reaction is 150-200° C., and the reaction time is 1-5 h.

4. Boehmite microspheres prepared by the preparation method according to any one of claims 1 to 3.

5. The boehmite microspheres according to claim 4, characterized in that: The specific surface area of ​​the boehmite microspheres is 200 to 400 m 2 / g, the morphology is a spherical porous / mesoporous structure, the pore size is 10-20nm, the ball diameter is 5-10μm, and the purity is ≥99.9%.

6. A method for preparing alumina microspheres, comprising calcining the boehmite microspheres according to claim 4 or 5 at a high temperature to obtain alumina microspheres.

7. The preparation method according to claim 6, characterized in that: The calcination temperature is 300-700° C. and the calcination time is 3-5 hours.

8. Alumina microspheres prepared by the preparation method according to claim 6 or 7.

9. The alumina microspheres according to claim 8, characterized in that: The specific surface area of ​​the alumina microspheres is 300 to 500 m 2 / g, the morphology is a spherical porous structure, the pore size is 20-80nm, the ball diameter is 5-10μm, and the purity is ≥99.9%.

10. Use of the boehmite microspheres according to claim 4 or 5 and the alumina microspheres according to claim 8 or 9 in the fields of adsorbents, catalyst carriers and alumina ceramic materials.

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