CN101367535B - A hydrothermal method for preparing γ-Al2O3 hollow microsphere polishing material without template - Google Patents

Abstract

The invention relates to a template-free hydrothermal method for preparing γ-Al ₂ O ₃ hollow microsphere polishing materials. The specific steps include: the first step, adding urea to the distilled aqueous solution of aluminum salt, stirring evenly, and transferring to a hydrothermal kettle In the hydrothermal reaction, the hydrothermal product is obtained; in the second step, after the hydrothermal product is cooled and vacuum filtered, the filter cake is washed with water to neutrality, and then the filter cake is washed once with absolute ethanol and suction filtered to obtain The filter cake is vacuum-dried at 80° C. for more than 6 hours to obtain pseudo-boehmite hollow microspheres. Step 3: Calcining the obtained pseudo-boehmite hollow microspheres at 400-700° C. for more than 3 hours to prepare γ-Al ₂ O ₃ hollow microsphere polishing materials. The method of the invention does not need to add an organic template agent, has low requirements on reaction conditions, simple operation and low cost.

Description

A hydrothermal method for preparing γ-Al2O3 hollow microsphere polishing material without template

technical field

The invention relates to the preparation of chemical alumina, in particular to a hydrothermal method for preparing gamma-Al ₂ O ₃ hollow microsphere polishing materials without a template.

Background technique

Alumina includes α-Al ₂ O ₃ and transition state alumina, which is an intermediate product in the final conversion of various aluminum hydroxides to stable α-Al ₂ O ₃ . Studies have shown that the transition state alumina has at least γ-Al ₂ O ₃ , η-Al ₂ O ₃ , ρ-Al ₂ O ₃ , χ-Al ₂ O ₃ , κ-Al ₂ O ₃ , δ-Al ₂ O ₃ and θ-Al ₂ O ₃ seven forms, the new transition state alumina is still being discovered and confirmed [Levin I, Brandon D. Metastable alumina polymorphs: crystal structures and transition sequences. J.Am.Ceram.Soc., 1998 , 81(8): 1995-2012]. Among various transition state aluminas, pseudo-boehmite (γ-AlOOH·nH ₂ O, n=0.08-0.62) is calcined at 400-700°C to form γ-alumina with higher specific surface area and larger pore volume -Al ₂ O ₃ is widely used as polishing material, catalyst carrier, catalyst and adsorbent in machinery, petrochemical and many other industries.

Alumina hollow microspheres have excellent characteristics such as low density, large surface area, high stability and high surface permeability, and have broad application prospects in the fields of polishing materials, catalyst supports and adsorbents. Kimberly et al [Kimberly A D, Andrew R B. A flexible route to high strength α-alumina and aluminate spheres. J. Mater. Science, 2003, 38: 2673-2678] once used polystyrene microstructures with a diameter of 3 μm and 50-80 μm The ball is used as a template, and aluminum salt colloid is coated on its surface, and then heated at 220 ° C to convert it into amorphous alumina, and the template in the inner layer of the microsphere is removed by washing with toluene to obtain amorphous alumina hollow microspheres. Calcined at 1000°C, α-Al ₂ O ₃ hollow microspheres with a particle size of 1-80 μm and a hardness close to that of corundum were formed. Zoltan et al [Zoltán K, János S. Hollow aluminum microspheres prepared by RF thermal plasma. Powder Technol., 2003, 132: 211-215] used gibbsite, a product of the Bayer process, as a raw material, using radio frequency thermal plasma induction method, By adding some diatomic gases to improve the heat transfer of Ar plasma, alumina hollow microspheres with a particle size of about 30-80 μm were prepared. Wu et al [Wu X Y, Wang D B, Hu Z S, Gu G H.Synthesis of γ-AlOOH(γ-Al ₂ O ₃ ) self-encapsulated and hollow architectures. Mater. Chem. Phys., 2008, 109, 560-564 .] Using composite amphiphilic block copolymer PS-b-PHEA as inducer, hydrothermal aluminum sulfate and urea solution at 150℃ for 24h, prepared boehmite and γ-Al ₂ O ₃ hollow particles with a particle size of about 4 μm Microspheres.

CN 1884083A discloses a method for preparing a nano-alumina hollow sphere structure. The mixed solution of AlCl ₃ and ethanol is vaporized in an evaporator by N ₂ , and then mixed with air and hydrogen at 200-350 ° C. It is hydrolyzed in the combustion chamber of ℃, and the nano-alumina hollow sphere structure is obtained.

The disadvantages of the above method are: the addition of organic template or inducer is required, or the reaction conditions are relatively high, or the operation is complicated. However, preparation of hollow alumina microspheres by liquid-phase method using cheap inorganic aluminum salts as raw materials, especially the preparation of γ-Al ₂ O ₃ hollow microspheres by direct hydrothermal-calcination process, has not been seen in literature and patents so far. public reporting.

Contents of the invention

The technical problem to be solved by the present invention is to provide a template-free hydrothermal method for preparing γ-Al ₂ O ₃ hollow microsphere polishing materials. The method does not need to add an organic template agent, the reaction conditions are not high, the operation is simple, and the cost is low. .

The technical solution adopted by the present invention to solve the problems of the technologies described above is:

A hydrothermal method for preparing gamma-Al ₂ O ₃ hollow microsphere polishing materials without a template, the specific steps comprising:

The first step is to add urea to the distilled aqueous solution of aluminum salt, stir evenly, transfer it to a hydrothermal kettle for hydrothermal reaction, and obtain a hydrothermal product;

The second step, after the hydrothermal product is cooled and vacuum filtered, the filter cake is washed with water to neutrality, and then the filter cake is washed once with absolute ethanol and suction filtered, and the obtained filter cake is vacuum-dried at 80°C for more than 6 hours , Pseudoboehmite hollow microspheres can be obtained.

Step 3: Calcining the obtained pseudo-boehmite hollow microspheres at 400-700° C. for more than 3 hours to prepare γ-Al ₂ O ₃ hollow microsphere polishing materials.

The aluminum salt is one or a combination of aluminum ammonium sulfate and aluminum potassium sulfate.

In the distilled aqueous solution of the aluminum salt, the concentration of Al ³⁺ is 0.005-0.30 mol/L.

The hydrothermal reaction is a closed hydrothermal reaction, the hydrothermal reaction temperature is 160-180° C., and the reaction time is 1-3 hours.

In the above scheme, the molar ratio of urea to Al ³⁺ is 2-2.5:1.

The method of the present invention uses aluminum salt as raw material, uses urea as a precipitating agent for the distilled aqueous solution of aluminum salt, and adopts template-free hydrothermal method to prepare pseudo-boehmite and γ-Al ₂ O ₃ hollow microspheres, which has low cost and breaks through the traditional template method Defects in the preparation of oxide hollow microspheres. The synthesis method of the present invention has the advantages of simple process, relatively mild hydrothermal conditions, uniform product particle size, large pore volume, high specific surface area and good hollow structure reproducibility, etc., which shows that it is used in machinery, petrochemical and other industries. Potential application prospects of polishing materials, catalyst supports, catalysts and adsorbents, etc.

The advantage of the inventive method also is:

1. The aluminum salt is one or a combination of aluminum sulfate, aluminum ammonium sulfate and aluminum potassium sulfate. The concentration of Al ³⁺ in the distilled aqueous solution is 0.005-0.30mol/L, which can make the concentration of aluminum source higher and can Further ensure that the product has uniform particle size and large pore volume.

2. The hydrothermal reaction is a closed hydrothermal reaction, the hydrothermal reaction temperature is 160-180°C, and the reaction time is 1-3 hours, which can ensure sufficient hydrothermal reaction.

The gamma-Al ₂ O ₃ hollow microsphere polishing material prepared by the invention can also be used as a catalyst carrier, a catalyst, an adsorbent and the like in the field of petrochemical industry.

Description of drawings

Fig. 1 is a scanning electron microscope (Scanning electron microscopy, SEM) photo of pseudo-boehmite hollow microspheres prepared by template-free hydrothermal method.

Fig. 2 is the SEM photo of γ-Al ₂ O ₃ hollow microspheres prepared by template-free hydrothermal method.

Fig. 3 is the SEM photo of γ-Al ₂ O ₃ hollow microspheres prepared by template-free hydrothermal method.

Fig. 4 is the SEM photo of γ-Al ₂ O ₃ hollow microspheres prepared by template-free hydrothermal method.

Fig. 5 is a SEM photo of γ-Al ₂ O ₃ hollow microspheres prepared by template-free hydrothermal method.

Fig. 6 is a SEM photo of γ-Al ₂ O ₃ hollow microspheres prepared by template-free hydrothermal method.

Fig. 7 is a SEM photo of γ-Al ₂ O ₃ hollow microspheres prepared by template-free hydrothermal method.

Fig. 8 is a SEM photo of γ-Al ₂ O ₃ hollow microspheres prepared by template-free hydrothermal method.

Detailed ways

Embodiment 1 of the inventive method:

In the first step, urea is added to the distilled aqueous solution of aluminum sulfate (Al ₂ (SO ₄ ) ₃ ·18H ₂ O), stirred evenly, and transferred to a hydrothermal kettle for hydrothermal reaction to obtain a hydrothermal product. The distilled aqueous solution of the aluminum salt is 70ml, the concentration of Al ³⁺ is 0.30mol/L, and the molar ratio of urea and Al ³⁺ is 2:1. The hydrothermal reaction is a closed hydrothermal reaction, the hydrothermal reaction temperature is 160-180° C., and the reaction time is 3 hours.

In the second step, after the hydrothermal product is cooled and vacuum filtered, the filter cake is first washed with water to neutrality, then the filter cake is washed once with absolute ethanol and suction filtered, and the obtained filter cake is vacuum-dried at 80°C for 8 hours. Alumina hydrate hollow microspheres with a flower-like structure on the surface were obtained, with a particle size of 1-5 μm, as shown in Figure 1, which was analyzed by X-ray powder diffraction (X-ray diffraction, XRD) as a pseudo-boehmite phase, namely Pseudoboehmite hollow microspheres were obtained.

The third step is calcining the obtained pseudo-boehmite hollow microspheres at 400° C. for 4 hours to prepare a γ-Al ₂ O ₃ hollow microsphere polishing material. As shown in Fig. 2, it is γ-Al ₂ O ₃ by XRD analysis, and its specific surface area and pore volume are 124.0m ² /g and 0.20cm ³ /g respectively.

Embodiment 2 of the inventive method:

In the first step, urea is added to distilled aqueous solution of potassium aluminum sulfate (KAl(SO ₄ ) ₂ ·12H ₂ O), stirred evenly, then transferred to a hydrothermal kettle for hydrothermal reaction to obtain a hydrothermal product. The distilled aqueous solution of the aluminum salt is 70ml, the concentration of Al ³⁺ is 0.005mol/L, and the molar ratio of urea and Al ³⁺ is 2:1. The hydrothermal reaction is a closed hydrothermal reaction, the hydrothermal reaction temperature is 160-180° C., and the reaction time is 3 hours.

In the second step, after the hydrothermal product is cooled and vacuum filtered, the filter cake is first washed with water to neutrality, then the filter cake is washed once with absolute ethanol and suction filtered, and the obtained filter cake is vacuum-dried at 80°C for 6 hours. Pseudoboehmite hollow microspheres were obtained. The particle size of the pseudo-boehmite hollow microspheres is 1-5 μm.

The third step is calcining the obtained pseudo-boehmite hollow microspheres at 500° C. for 4 hours to prepare a γ-Al ₂ O ₃ hollow microsphere polishing material. As shown in Fig. 3, it is γ-Al ₂ O ₃ phase analyzed by X-ray powder diffraction XRD, and its specific surface area and pore volume are 215.3m ² /g and 0.47cm ³ /g respectively.

Embodiment 3 of the inventive method:

In the first step, urea is added to the distilled aqueous solution of aluminum sulfate (Al ₂ (SO ₄ ) ₃ ·18H ₂ O), stirred evenly, and transferred to a hydrothermal kettle for hydrothermal reaction to obtain a hydrothermal product. The distilled aqueous solution of the aluminum salt is 70ml, the concentration of Al ³⁺ is 0.05mol/L, and the molar ratio of urea to Al ³⁺ is 2.5:1. The hydrothermal reaction is a closed hydrothermal reaction, the hydrothermal reaction temperature is 160-180° C., and the reaction time is 3 hours.

In the second step, after the hydrothermal product is cooled and vacuum filtered, the filter cake is first washed with water to neutrality, then the filter cake is washed once with absolute ethanol and suction filtered, and the obtained filter cake is vacuum-dried at 80°C for 8 hours. Pseudoboehmite hollow microspheres were obtained. The particle size of the pseudo-boehmite hollow microspheres is 1-5 μm.

The third step is calcining the obtained pseudo-boehmite hollow microspheres at 700° C. for 4 hours to prepare a γ-Al ₂ O ₃ hollow microsphere polishing material. As shown in Fig. 4, it is γ-Al ₂ O ₃ phase by XRD analysis, and its specific surface area and pore volume are 166.3m ² /g and 0.54cm ³ /g respectively.

Embodiment 4 of the method of the present invention:

In the first step, urea is added to the distilled aqueous solution of aluminum sulfate (Al ₂ (SO ₄ ) ₃ ·18H ₂ O), stirred evenly, and transferred to a hydrothermal kettle for hydrothermal reaction to obtain a hydrothermal product. The distilled aqueous solution of the aluminum salt is 70ml, the concentration of Al ³⁺ is 0.20mol/L, and the molar ratio of urea and Al ³⁺ is 2:1. The hydrothermal reaction is a closed hydrothermal reaction, the hydrothermal reaction temperature is 160-180° C., and the reaction time is 1 hour.

In the second step, after the hydrothermal product is cooled and vacuum filtered, the filter cake is first washed with water to neutrality, then the filter cake is washed once with absolute ethanol and suction filtered, and the obtained filter cake is vacuum-dried at 80°C for 8 hours. Pseudo-boehmite hollow microspheres were obtained. The particle size of the pseudo-boehmite hollow microspheres is 1-5 μm.

The third step is calcining the obtained pseudo-boehmite hollow microspheres at 500° C. for 4 hours to prepare a γ-Al ₂ O ₃ hollow microsphere polishing material. As shown in Fig. 5, it is γ-Al ₂ O ₃ phase by XRD analysis, and its specific surface area and pore volume are 154.2m ² /g and 0.42cm ³ /g respectively.

Embodiment 5 of the method of the present invention:

In the first step, urea is added to the distilled aqueous solution of aluminum sulfate (Al ₂ (SO ₄ ) ₃ ·18H ₂ O), stirred evenly, and transferred to a hydrothermal kettle for hydrothermal reaction to obtain a hydrothermal product. The distilled aqueous solution of the aluminum salt is 70ml, the concentration of Al ³⁺ is 0.20mol/L, and the molar ratio of urea to Al ³⁺ is 2.3:1. The hydrothermal reaction is a closed hydrothermal reaction, the hydrothermal reaction temperature is 160-180° C., and the reaction time is 2 hours.

In the second step, after the hydrothermal product is cooled and vacuum filtered, the filter cake is first washed with water to neutrality, then the filter cake is washed once with absolute ethanol and suction filtered, and the obtained filter cake is vacuum-dried at 80°C for 6 hours. Pseudoboehmite hollow microspheres were obtained.

The third step is calcining the obtained pseudo-boehmite hollow microspheres at 550° C. for 3 hours to prepare a γ-Al ₂ O ₃ hollow microsphere polishing material. As shown in Fig. 6, the particle size of the microspheres is 1-5 μm, which is γ-Al ₂ O ₃ phase by XRD analysis, and its specific surface area and pore volume are 146.3m ² /g and 0.34cm ³ /g respectively.

Embodiment 6 of the method of the present invention:

In the first step, urea is added to the distilled aqueous solution of the aluminum sulfate, aluminum ammonium sulfate, and aluminum potassium sulfate composition, stirred evenly, and then transferred to a hydrothermal kettle for hydrothermal reaction to obtain a hydrothermal product. The distilled aqueous solution of the aluminum salt is 70ml, the concentration of Al ³⁺ is 0.20mol/L, and the molar ratio of urea and Al ³⁺ is 2:1. The hydrothermal reaction is a closed hydrothermal reaction, the hydrothermal reaction temperature is 160-180° C., and the reaction time is 3 hours.

In the second step, after the hydrothermal product is cooled and vacuum filtered, the filter cake is first washed with water to neutrality, then the filter cake is washed once with absolute ethanol and suction filtered, and the obtained filter cake is vacuum-dried at 80°C for 6 hours. Pseudoboehmite hollow microspheres were obtained.

The third step is calcining the obtained pseudo-boehmite hollow microspheres at 500° C. for 4 hours to prepare a γ-Al ₂ O ₃ hollow microsphere polishing material. As shown in Fig. 7, the particle size of the microspheres is 1-5 μm, which is γ-Al ₂ O ₃ phase by XRD analysis, and its specific surface area and pore volume are 139.1m ² /g and 0.37cm ³ /g respectively.

Embodiment 7 of the inventive method:

In the first step, urea is added to the distilled aqueous solution of ammonium aluminum sulfate (AlNH ₄ (SO ₄ ) ₂ ·12H ₂ O), stirred evenly, and then transferred to a hydrothermal kettle for hydrothermal reaction to obtain a hydrothermal product. The distilled aqueous solution of the aluminum salt is 70ml, the concentration of Al ³⁺ is 0.005mol/L, and the molar ratio of urea and Al ³⁺ is 2:1. The hydrothermal reaction is a closed hydrothermal reaction, the hydrothermal reaction temperature is 160-180° C., and the reaction time is 3 hours.

In the second step, after the hydrothermal product is cooled and vacuum filtered, the filter cake is first washed with water to neutrality, then the filter cake is washed once with absolute ethanol and suction filtered, and the obtained filter cake is vacuum-dried at 80°C for 6 hours. Pseudoboehmite hollow microspheres were obtained.

The third step is calcining the obtained pseudo-boehmite hollow microspheres at 550° C. for 3 hours to prepare a γ-Al ₂ O ₃ hollow microsphere polishing material. As shown in Figure 8, the particle size of the microspheres is 1-5 μm, and it is γ-Al ₂ O ₃ phase by XRD analysis, and its specific surface area and pore volume are 161.2m ² /g and 0.60cm ³ /g, respectively.

The above description is only a preferred embodiment of the present invention. In fact, aluminum salts can be used as raw materials of the method of the present invention. Usually changes and substitutions should be included in the protection scope of the present invention.

Claims (2)

1. A template-free preparation of γ-Al ₂ O ₃ the hydrothermal method of the hollow microsphere polishing material, the concrete steps comprising: The first step is to add urea to the distilled aqueous solution of aluminum salt, stir evenly, transfer it to a hydrothermal kettle for hydrothermal reaction, and obtain a hydrothermal product; The second step, after the hydrothermal product is cooled and vacuum filtered, the filter cake is washed with water to neutrality, and then the filter cake is washed once with absolute ethanol and suction filtered, and the obtained filter cake is vacuum-dried at 80°C for more than 6 hours , the pseudoboehmite hollow microspheres can be obtained; The third step is to roast the obtained pseudoboehmite hollow microspheres at 400-700° C. for more than 3 hours to prepare γ-Al ₂ O ₃ hollow microsphere polishing materials; The aluminum salt is one or a combination of aluminum ammonium sulfate and aluminum potassium sulfate; In the distilled aqueous solution of the aluminum salt, the concentration of Al3 ⁺ is 0.005-0.30mol/L; The hydrothermal reaction is a closed hydrothermal reaction, the hydrothermal reaction temperature is 160-180° C., and the reaction time is 1-3 hours. 2. The hydrothermal method according to claim 1, characterized in that: the molar ratio of urea to Al ³⁺ is 2-2.5:1.

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