阅读说明：本技术 一种γ-氧化铝晶粒及其制备方法 (Gamma-alumina crystal grain and preparation method thereof ) 是由 杨卫亚 隋宝宽 凌凤香 张会成 王少军 沈智奇 于 2019-10-25 设计创作，主要内容包括：本发明公开了一种γ-氧化铝晶粒及其制备方法。γ-氧化铝晶粒的制备方法,包括如下内容：(1)将拟薄水铝石粉体焙烧后,再掺入一定量的无机钠盐,然后采用高能球磨机将粉体研磨,然后洗涤去除钠盐后,加入醇水混合溶剂配成一定浓度的悬浊液,添加一定量的有机酸后,进行高速剪切处理；(2)向步骤(1)得到的物料中加入一定量氨水与有机碱混合物,然后把混合物搅拌均匀；(3)步骤(2)得到的物料进行密闭水热处理,处理完毕后,固液分离,干燥、焙烧,得到γ-氧化铝晶粒。本发明的γ-氧化铝晶粒具有八面体形貌,暴露出特殊的晶面分布,在催化及吸附领域具有广阔的应用前景。(The invention discloses a gamma-alumina crystal grain and a preparation method thereof. The preparation method of the gamma-alumina crystal grain comprises the following steps: (1) calcining pseudo-boehmite powder, adding a certain amount of inorganic sodium salt, grinding the powder by using a high-energy ball mill, washing to remove the sodium salt, adding an alcohol-water mixed solvent to prepare a suspension with a certain concentration, adding a certain amount of organic acid, and carrying out high-speed shearing treatment; (2) adding a certain amount of ammonia water and organic base mixture into the material obtained in the step (1), and then uniformly stirring the mixture; (3) and (3) carrying out closed hydrothermal treatment on the material obtained in the step (2), and after the treatment is finished, carrying out solid-liquid separation, drying and roasting to obtain gamma-alumina grains. The gamma-alumina crystal grain has the octahedral appearance, exposes out special crystal face distribution, and has wide application prospect in the fields of catalysis and adsorption.)

1. A preparation method of gamma-alumina crystal grains is characterized by comprising the following steps: (1) calcining pseudo-boehmite powder, adding a certain amount of inorganic sodium salt, grinding the powder by using a high-energy ball mill, washing to remove the sodium salt, adding an alcohol-water mixed solvent to prepare a suspension with a certain concentration, adding a certain amount of organic acid, and carrying out high-speed shearing treatment; (2) adding a certain amount of ammonia water and organic base mixture into the material obtained in the step (1), and then uniformly stirring the mixture; (3) and (3) carrying out closed hydrothermal treatment on the material obtained in the step (2), and after the treatment is finished, carrying out solid-liquid separation, drying and roasting to obtain gamma-alumina grains.

2. The method of claim 1, wherein: the roasting conditions of the pseudo-boehmite powder in the step (1) are as follows: 600 ℃ and 750 ℃, and the roasting time is 1-12 hours.

3. The method of claim 1, wherein: the grinding particle size in the step (1) is less than 5000 meshes, preferably 10000-.

4. The method of claim 1, wherein: the inorganic sodium salt in the step (1) is one or more of sodium nitrate, sodium chloride or sodium sulfate, and accounts for 0.1-10% of the mass of the calcined pseudo-boehmite powder.

5. The method of claim 1, wherein: the mass concentration of the suspension prepared in the step (1) is 10-50 g/L.

6. The method of claim 1, wherein: in the alcohol-water mixed solvent in the step (1), the alcohol is methanol or ethanol, and the mass ratio of water/alcohol is 0.2-1.

7. The method of claim 1, wherein: the organic acid in the step (1) is one or more of formic acid, acetic acid or citric acid, and the amount of the organic acid is 0.1-10% of the mass of the calcined pseudo-boehmite aluminum powder.

8. The method of claim 1, wherein: the high-speed shearing treatment conditions in the step (1) are as follows: the rotation speed is 2000 plus 50000 r/min, and the time is 1-60 min, preferably the conditions are that the rotation speed is 5000 plus 50000 r/min, and the time is 5-45 min.

9. The method of claim 1, wherein: the organic alkali in the step (2) is one or more of tetramethylammonium hydroxide, tetraethylammonium hydroxide or tetrapropylammonium hydroxide; the mass concentration of the organic alkali in the material system is 30-200g/L

The method of claim 1, wherein: the mass concentration of the ammonia water in the step (2) in the material system is 100-280 g/L.

10. The method of claim 1, wherein: the closed hydrothermal condition of the step (3) is as follows: hydrothermal treatment at 100-220 deg.c for 0.5-72 hr.

11. The method of claim 1, wherein: the roasting conditions in the step (3) are as follows: baking at 450-750 deg.C for 1-24 hr.

12. A gamma-alumina grain characterized by: the crystal grain is in a single crystal octahedron shape, and 8 exposed surfaces of the crystal grain belong to a { 111 } crystal face group of gamma-aluminum oxide, namely 8 crystal faces of (111), (-111), (1-11), (11-1), (-1-1-1), (-11-1) and (-1-11); the shape of 8 external surfaces of the octahedral crystal grain is triangular or approximately triangular, and the side length of the triangle is 2-10 mu m; the grain size of the gamma-alumina grains is 6-22 μm.

13. Use of the gamma-alumina crystallites according to claim 13 in the fields of catalysis, adsorption and ceramics.

Technical Field

The invention belongs to the field of inorganic material preparation, and particularly relates to a gamma-alumina crystal grain and a preparation method thereof.

Background

The active alumina has good physicochemical properties such as large specific surface area, adjustable pore structure, acid centers with different properties on the surface, higher mechanical strength, thermal stability and the like, and is widely used as a catalyst carrier in the fields of oil refining hydrogenation catalysis and the like, and the property of the alumina is one of key factors influencing the performance of the catalyst. Alumina is a crystal material composed of primary grains, and the crystal planes of the primary grains determine the physicochemical properties of the alumina in a Bottom-Up (Bottom-Up) mode and are finally reflected on the catalytic performance of the catalyst.

Various crystal faces of the aluminum oxide crystal grains have different atom densities and atom symmetries, so that the properties of electronic structures, surface energy, chemical activity and the like of the crystal faces are greatly different. By regulating the restriction factor of the growth of the alumina crystal grains and regulating the crystal face type and proportion of the alumina crystal grains, the deep regulation and control of the key physicochemical properties of the alumina, such as the specific surface, the pore structure, the acidity, the atomic and molecular chemical environment and the like, can be realized from the source.

Currently, in the industrial hydrogenation catalyst using γ -alumina as a carrier, the alumina is mainly based on the crystal plane distribution of (110), (111) and (100), wherein the crystal plane distribution of (110) is generally about 70%. The three crystal faces and the distribution of the alumina can obviously affect the active phase of the hydrogenation catalyst, and respectively lead the catalyst to show the hydrodesulfurization and olefin saturation performances with various characteristics. Therefore, if the relative proportion of the crystal faces of the alumina (110), (111) and (100) can be flexibly regulated and controlled to respectively achieve the advantage distribution, and the influence rule of the advantage crystal faces on the catalytic performance of the hydrogenation catalyst is determined, theoretical guidance can be provided for the development of a novel hydrogenation catalyst carrier. However, due to the limitation of crystal growth habit, the dominant distribution of the crystal plane of the alumina (110) is difficult to be effectively controlled in the conventional synthesis method, the dominant distribution of the crystal planes (111) and (100) cannot be realized, the influence of the specific crystal plane on the catalytic performance of the catalyst is difficult to reflect, and the regulation of the activity and the selectivity of the catalyst according to the surface crystal plane property of crystal grains is not facilitated.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides the gamma-alumina crystal grain and the preparation method thereof, and the gamma-alumina crystal grain has an octahedral shape, exposes special crystal face distribution and has wide application prospect in the fields of catalysis and adsorption.

The preparation method of the gamma-alumina crystal grain comprises the following steps:

(1) calcining pseudo-boehmite powder, adding a certain amount of inorganic sodium salt, grinding the powder by using a high-energy ball mill, washing to remove the sodium salt, adding an alcohol-water mixed solvent to prepare a suspension with a certain concentration, adding a certain amount of organic acid, and carrying out high-speed shearing treatment;

(2) adding a certain amount of ammonia water and organic base mixture into the material obtained in the step (1), and then uniformly stirring the mixture;

(3) and (3) carrying out closed hydrothermal treatment on the material obtained in the step (2), and after the treatment is finished, carrying out solid-liquid separation, drying and roasting to obtain gamma-alumina grains.

In the method of the invention, the roasting conditions of the pseudo-boehmite powder in the step (1) are as follows: 600 ℃ and 750 ℃, and the roasting time is 1-12 hours.

In the method of the present invention, the grinding particle size in step (1) is less than 5000 mesh, preferably 10000-.

In the method, the inorganic sodium salt in the step (1) is one or more of sodium nitrate, sodium chloride or sodium sulfate, and the inorganic sodium salt accounts for 0.1-10% of the mass of the calcined pseudo-boehmite powder. The washing for removing the sodium salt can be carried out by adopting distilled water.

In the method, the mass concentration of the suspension prepared in the step (1) is 10-50 g/L.

In the method, in the alcohol-water mixed solvent in the step (1), the alcohol is methanol or ethanol, and the mass ratio of water to alcohol is 0.2-1.

In the method, the organic acid in the step (1) is one or more of formic acid, acetic acid or citric acid, and the amount of the organic acid is 0.1-10% of the mass of the calcined pseudo-boehmite aluminum powder, preferably 0.5-5%.

In the method of the invention, the high-speed shearing treatment conditions in the step (1) are as follows: the rotation speed is 2000 plus 50000 r/min, and the time is 1-60 min, preferably the conditions are that the rotation speed is 5000 plus 50000 r/min, and the time is 5-45 min.

In the method, the organic alkali in the step (2) is one or more of tetramethylammonium hydroxide, tetraethylammonium hydroxide or tetrapropylammonium hydroxide; the mass concentration of the organic alkali in the material system is 30-200g/L

In the method, the mass concentration of the ammonia water in the step (2) in a material system is 100-280 g/L.

In the method, the closed hydrothermal conditions in the step (3) are as follows: the hydrothermal treatment is carried out at 100-220 ℃ for 0.5-72 hours, preferably at 120-200 ℃ for 2-12 hours.

In the method of the invention, the drying temperature in the step (3) is not more than 250 ℃, preferably not more than 120 ℃, and the drying degree is the constant weight of the material at the drying temperature.

In the method, the roasting conditions in the step (3) are as follows: roasting at 750 ℃ for 1-24 hours at 450-.

The gamma-alumina crystal grain is in a single crystal octahedron shape, 8 exposed surfaces of the crystal grain belong to a { 111 } crystal face group of gamma-alumina, and are respectively (111), (-111), (1-11), (11-1), (-1-1-1), (-11-1) and (-1-11)8 crystal faces; the shape of 8 external surfaces of the octahedral crystal grain is triangular or approximately triangular, and the side length of the triangle is 2-10 mu m; the grain size of the gamma-alumina grains is 6-22 μm.

The gamma-alumina crystal grain of the invention is an excellent inorganic material due to the regular octahedral morphology and single crystal structure, and has wide application prospect in the fields of catalysis, adsorption and ceramics.

Drawings

FIG. 1 is a scanning electron micrograph of alumina grains after baking at 550 ℃ in example 1.

FIG. 2 is an electron diffraction pattern of alumina grains of example 1 after baking at 550 ℃.

FIG. 3 is the XRD spectrum of alumina grains after drying at 200 ℃ in example 1.

FIG. 4 is the XRD spectrum of the alumina grains of example 1 after calcination at 550 ℃.

Detailed Description

The process of the present invention is illustrated in detail by the following examples. The shape and size of octahedral alumina crystal grains are observed and measured by a scanning electron microscope. The crystal form is characterized by X-ray diffraction, and the sample particles are judged to be single crystals or polycrystal through electron diffraction analysis. According to the scanning electron microscope image, the lengths of two top ends of the octahedral crystal grains are taken as the crystal grain sizes.

Example 1

Calcining pseudo-boehmite powder at 650 ℃ for 7 hours, uniformly doping sodium chloride accounting for 3% of the mass of the pseudo-boehmite powder, grinding the pseudo-boehmite powder into micro powder by using a ball mill, sieving the micro powder with about 1000 meshes, washing the micro powder by using distilled water to remove the sodium chloride, and preparing 25g/L suspension, wherein the solvent of the suspension is a mixture of water and ethanol, and the mass ratio of the water to the ethanol is 3. Part of acetic acid was added to the suspension so that the amount of acetic acid was 3% by mass of the alumina precursor. A high-speed shear stirrer (20000 rpm) was used, and the mixture was shear-stirred at room temperature for 15 minutes. Adding ammonia water and tetraethyl ammonium hydroxide into the system, and finally, respectively adding the ammonia water and the tetraethyl ammonium hydroxide into the system, uniformly stirring the ammonia water and the tetraethyl ammonium hydroxide to obtain the ammonia water and the tetraethyl ammonium hydroxide, sealing the system and heating the system to 200 ℃ for hydrothermal treatment for 6 hours. The product dried at 120 ℃ is respectively dried at 200 ℃ and roasted at 550 ℃ for 6 hours. XRD spectra of the products obtained at the two treatment temperatures show that the products are pseudo-boehmite and gamma-alumina respectively. The observation of a scanning electron microscope shows that the drying or roasting temperature has no obvious influence on the appearance, the products are all in the shape of octahedral particles, and the electron diffraction spectrum of the product slices is diffraction spots which are regularly arranged, so that the particles have a single crystal structure. According to the relevant crystallographic growth law, the octahedron can only expose the { 111 } family crystal face. The size of the octahedron crystal grain is about 21 μm, and the octahedron { 111 } family crystal face is approximately triangular, and the side length is about 11 μm. The octahedral crystal particle theoretically has a { 111 } family crystal face accounting for 100%.

Example 2

Calcining pseudo-boehmite powder at 750 ℃ for 2 hours, uniformly doping sodium chloride accounting for 3% of the mass of the pseudo-boehmite powder, grinding the pseudo-boehmite powder into micro powder by using a ball mill, sieving powder of about 10000 meshes, washing the micro powder by using distilled water to remove the sodium chloride, and preparing 20g/L suspension, wherein the solvent of the suspension is a mixture of water and ethanol, and the mass ratio of the water to the ethanol is 4. Part of acetic acid was added to the suspension so that the amount of acetic acid was 3% by mass of the alumina precursor. The mixture was stirred with a high-speed shear stirrer (20000 rpm) at room temperature for 20 minutes. Adding ammonia water and tetrapropylammonium hydroxide into the system, wherein the final concentrations of the ammonia water and the tetrapropylammonium hydroxide are respectively 200g/L and 85g/L, uniformly stirring, sealing the system, and heating to 180 ℃ for hydrothermal treatment for 10 hours. The product dried at 120 ℃ is respectively dried at 200 ℃ and roasted at 550 ℃ for 6 hours. XRD spectra of the products obtained at the two treatment temperatures show that the products are pseudo-boehmite and gamma-alumina respectively. The observation of a scanning electron microscope shows that the drying or roasting temperature has no obvious influence on the appearance, the products are all in the shape of octahedral particles, and the electron diffraction spectrum of the product slices is diffraction spots which are regularly arranged, so that the particles have a single crystal structure. According to the related crystallography structural rules, the octahedron can only expose the 111 family crystal face. The size of the octahedron crystal grain is about 19 μm, and the octahedron { 111 } family crystal face is approximately triangular, and the side length is about 8 μm. The octahedral crystal particle theoretically has a { 111 } family crystal face accounting for 100%.

Example 3

Calcining the pseudo-boehmite powder for 6 hours at 600 ℃, then uniformly doping sodium chloride accounting for 3 percent of the mass of the pseudo-boehmite powder, grinding the pseudo-boehmite powder into micro powder by using a ball mill, sieving the micro powder with about 20000 meshes, washing the micro powder with distilled water to remove the sodium chloride, and preparing 15g/L suspension, wherein the solvent of the suspension is a mixture of water and methanol, and the mass ratio of the water to the methanol is 5. Part of citric acid was added to the suspension so that the amount of citric acid was 6% by mass of the alumina precursor. The mixture was stirred with a high-speed shear stirrer (20000 rpm) at room temperature for 20 minutes. Adding ammonia water and tetramethyl ammonium hydroxide into the system, wherein the final concentrations of the ammonia water and the tetramethyl ammonium hydroxide are respectively 220g/L and 60g/L, uniformly stirring, sealing the system, and heating to 150 ℃ for hydrothermal treatment for 12 hours. The product dried at 120 ℃ is respectively dried at 200 ℃ and roasted at 550 ℃ for 6 hours. XRD spectra of the products obtained at the two treatment temperatures show that the products are pseudo-boehmite and gamma-alumina respectively. The observation of a scanning electron microscope shows that the drying or roasting temperature has no obvious influence on the appearance, the products are all in the shape of octahedral particles, and the electron diffraction spectrum of the product slices is diffraction spots which are regularly arranged, so that the particles have a single crystal structure. According to the related crystallography structural rules, the octahedron can only expose the 111 family crystal face. The size of the octahedron crystal grain is about 12 μm, and the octahedron { 111 } family crystal face is approximately triangular, and the side length is about 6 μm. The octahedral crystal particle theoretically has a { 111 } family crystal face accounting for 100%.

Comparative example 1

Octahedral alumina crystallites were prepared according to the method provided in example 1 of CN 201610494090.3. The obtained product is roasted for 5 hours at 200 ℃ and 550 ℃ respectively. The 200 ℃ roasted product has no pseudo-boehmite or boehmite structure, and the 550 ℃ roasted product cannot form gamma-alumina.