阅读说明：本技术 一种氧化铝材料及其制备方法 (Alumina material and preparation method thereof ) 是由 杨卫亚 凌凤香 张会成 王少军 王丽华 沈智奇 于 2019-10-25 设计创作，主要内容包括：本发明公开了一种氧化铝材料及其制备方法,包括如下内容：(1)将无机铝盐溶液冷却至-65～-30℃；(2)向步骤(1)得到的物料中加入一定量的无机碱和有机胺,混合均匀并老化一段时间；(3)步骤(2)得到的物料升温至一定温度,密闭水热反应,反应结束后,固液分离,干燥、焙烧,得到氧化铝材料。本发明通过特定类型的有机胺类化合物作为晶粒形态调控剂,在一定的化学环境下使氧化铝前驱物发生重排,形成八面体形貌,并相应形成特殊的晶面暴露状况。本发明氧化铝材料在催化剂、吸附材料制备等领域有着广阔的应用前景。(The invention discloses an alumina material and a preparation method thereof, comprising the following steps: (1) cooling the inorganic aluminum salt solution to-65 to-30 ℃; (2) adding a certain amount of inorganic base and organic amine into the material obtained in the step (1), uniformly mixing and aging for a period of time; (3) and (3) heating the material obtained in the step (2) to a certain temperature, carrying out closed hydrothermal reaction, carrying out solid-liquid separation after the reaction is finished, drying, and roasting to obtain the aluminum oxide material. According to the invention, a specific type of organic amine compound is used as a grain morphology regulator, an alumina precursor is rearranged under a certain chemical environment to form an octahedron shape, and a special crystal face exposure condition is correspondingly formed. The alumina material has wide application prospect in the fields of catalyst, adsorption material preparation and the like.)

1. The preparation method of the aluminum oxide material is characterized by comprising the following steps of: (1) cooling the inorganic aluminum salt solution to-65 to-30 ℃; (2) adding a certain amount of inorganic base and organic amine into the material obtained in the step (1), uniformly mixing and aging for a period of time; (3) and (3) heating the material obtained in the step (2) to a certain temperature, carrying out closed hydrothermal reaction, carrying out solid-liquid separation after the reaction is finished, drying, and roasting to obtain the aluminum oxide material.

2. The method of claim 1, wherein: the inorganic aluminum salt in the step (1) is one or more of aluminum chloride, aluminum nitrate or aluminum sulfate.

3. The method of claim 1, wherein: in the step (1), the inorganic aluminum salt solution has a mass percentage concentration of 5-35%, the solvent is a water-alcohol mixture, and the mass ratio of water to alcohol is 0.05-1, preferably 0.1-0.9; the alcohol is methanol and/or ethanol.

4. The method of claim 1, wherein: the inorganic base in the step (2) is sodium hydroxide and/or potassium hydroxide, and the organic amine is one or more of methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, n-propylamine, isopropylamine or n-butylamine.

5. The method of claim 1, wherein: the inorganic base and the inorganic aluminum salt in the step (2) are replaced by OH^-/Al³⁺The molar ratio is 3-7.

6. The method of claim 1, wherein: the molar ratio of the organic amine to the inorganic base in the step (2) is 0.2-1.

7. The method of claim 1, wherein: and (3) aging at-70 to-30 ℃ for 5 to 120 minutes in the step (2).

8. The method of claim 1, wherein: the closed hydrothermal condition of the step (3) is as follows: the hydrothermal treatment at 100-250 ℃ for 0.5-72 hours, preferably at 120-200 ℃ for 2-12 hours.

9. The method of claim 1, wherein: the drying temperature in the step (3) is not more than 250 ℃, and the drying degree is the constant weight of the material at the drying temperature; the roasting conditions are as follows: baking at 450-750 deg.C for 1-24 hr.

10. An alumina material characterized by: the aluminum oxide material is gamma-crystalline phase and has a single crystal octahedron stereo morphology; the outer 8 surfaces belong to the { 111 } crystal face family of gamma-alumina, including (111), (-111), (1-11), (11-1), (-1-1-1), (-11-1) and (-1-11) crystal faces; the 8 surfaces are equilateral triangles or nearly equilateral triangles, the side length of the triangle is 500-5000 nm, and the grain size is 1-9 μm.

Technical Field

The invention belongs to the field of inorganic material preparation, and particularly relates to an aluminum oxide material 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 crystalline material consisting of primary grains, and the crystal planes of the primary grains determine the physicochemical properties of the alumina in a manner that the crystal planes are upward from the bottom layer and finally reflect 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.

[ petroleum refining and chemical engineering, 2013, 44 (9): 47-50. by adding sodium nitrate, the crystal plane distribution range of the alumina single crystal particles can be changed to a certain extent, but the crystal plane of the alumina is still mainly (110).

CN201610494090.3 provides a preparation method of octahedral alumina with micron size. Inorganic aluminum salt and organic additive are dissolved in solvent to form solution, and the octahedral alumina precursor is obtained after 1-48 hours of hydrothermal treatment. As can be seen from the XRD spectrum of the product calcined at 200 ℃, the octahedral alumina does not have a boehmite structure or a pseudo-boehmite structure, so that the octahedral alumina cannot be converted into gamma-alumina under the conventional calcination condition of 500-700 ℃, and the application requirement in the catalysis field is difficult to be well met.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides an aluminum oxide material and a preparation method thereof, wherein a specific type of organic amine compound is used as a grain shape regulating agent, an aluminum oxide precursor is rearranged under a certain chemical environment to form an octahedron shape, and a special crystal face exposure condition is correspondingly formed.

The preparation method of the aluminum oxide material comprises the following steps:

(1) cooling the inorganic aluminum salt solution to-65 to-30 ℃;

(2) adding a certain amount of inorganic base and organic amine into the material obtained in the step (1), uniformly mixing and aging for a period of time;

(3) and (3) heating the material obtained in the step (2) to a certain temperature, carrying out closed hydrothermal reaction, carrying out solid-liquid separation after the reaction is finished, drying, and roasting to obtain the aluminum oxide material.

In the method of the present invention, the inorganic aluminum salt in step (1) is one or more of aluminum chloride, aluminum nitrate or aluminum sulfate.

In the method of the present invention, in the step (1), the inorganic aluminum salt solution has a mass percentage concentration of 5% to 35%. The solvent is a water-alcohol mixture, and the mass ratio of water to alcohol is 0.05-1, preferably 0.1-0.9; the alcohol is methanol and/or ethanol.

In the method, the inorganic base in the step (2) is sodium hydroxide and/or potassium hydroxide, and the organic amine is one or more of methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, n-propylamine, isopropylamine or n-butylamine; inorganic base and inorganic aluminium salt with OH^-/Al³⁺The molar ratio is 3-7; the molar ratio of the organic amine to the inorganic base is 0.2-1.

In the method of the present invention, the inorganic base and the organic amine in the step (2) may be added to the inorganic aluminum salt solution at the same time, or may be added separately, preferably, the organic amine is first added to the solution and mixed uniformly, and then the inorganic base is added.

In the method, the aging temperature in the step (2) is-70 to-30 ℃, and the aging time is 5 to 120 minutes.

In the method, the closed hydrothermal conditions in the step (3) are as follows: the hydrothermal treatment at 100-250 ℃ 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 aluminum oxide material is a gamma-crystalline phase, has a single crystal octahedron stereo morphology, has 8 external surfaces belonging to a { 111 } crystal face group of gamma-aluminum oxide, and comprises (111), (-111), (1-11), (11-1), (-1-1-1), (-11-1) and (-1-11) crystal faces; the 8 surfaces are equilateral triangles or nearly equilateral triangles, the side length of the triangle is 500-5000 nm, and the grain size is 1-9 μm.

The alumina material of the invention is applied in the fields of catalysis, adsorption and ceramics.

Drawings

FIG. 1 is a scanning electron micrograph of an alumina material calcined at 550 ℃ in example 1.

FIG. 2 is an electron diffraction pattern of the alumina material calcined at 550 ℃ in example 1.

FIG. 3 is an XRD spectrum of the alumina material after being dried at 200 ℃ in example 1.

FIG. 4 is an XRD spectrum of the alumina material calcined at 550 ℃ in example 1.

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. The low temperature reaction temperature is realized by adopting a low temperature circulating tank, an ultralow temperature liquid nitrogen refrigerator or liquid nitrogen hydrazine. 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

Preparing an aluminum chloride solution, cooling the solution to-40 ℃, slowly adding organic alkali, uniformly stirring, adding inorganic alkali, uniformly stirring, and aging at-50 ℃ for 60 minutes. The initial material relationship satisfies: the mass ratio of water to ethanol is 0.35; the mass concentration of the inorganic aluminum salt solution is 15 percent; the amount of sodium hydroxide satisfies OH^-/Al³⁺The molar ratio is 5.5; the molar ratio of trimethylamine to sodium hydroxide used was 0.5.

The aged material was heated to 200 ℃ for 5 hours. After washing, the product dried at 200 ℃ was calcined at 550 ℃ for 6 hours. XRD spectra of the 200 ℃ dried product and the 550 ℃ calcined product showed 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 growth rule of gamma-alumina cubic system relative to crystallography, the octahedron can only expose the crystal face of the { 111 } family. The size of the octahedron crystal grain is about 7 μm, the octahedron { 111 } family crystal face is approximately triangular, and the side length is about 2.5 μm. The octahedral crystal particle theoretically has a { 111 } family crystal face accounting for 100%.

Example 2

Preparing an aluminum chloride solution, cooling the solution to-30 ℃, slowly adding organic alkali, uniformly stirring, adding inorganic alkali, uniformly stirring, and aging at-50 ℃ for 80 minutes. The initial material relationship satisfies: the mass ratio of water to ethanol is 0.45; the mass concentration of the inorganic aluminum salt solution is 20 percent; the amount of potassium hydroxide satisfies OH^-/Al³⁺The molar ratio is 5.0; the molar ratio of propylamine to potassium hydroxide used was 0.5.

The aged material was heated to 200 ℃ for 5 hours. After washing, the product dried at 200 ℃ was calcined at 550 ℃ for 6 hours. XRD spectra of the 200 ℃ dried product and the 550 ℃ calcined product showed 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 growth rule of gamma-alumina cubic system relative to crystallography, the octahedron can only expose the crystal face of the { 111 } family. The size of the octahedron crystal grain is about 8 μm, the octahedron { 111 } family crystal face is approximately triangular, and the side length is about 1.9 μm. The octahedral crystal particle theoretically has a { 111 } family crystal face accounting for 100%.

Example 3

Preparing an aluminum chloride solution, cooling the solution to-62 ℃, slowly adding organic base, uniformly stirring, adding inorganic base, uniformly stirring, and aging at-62 ℃ for 120 minutes. The initial material relationship satisfies: the mass ratio of water/ethanol is 0.15; the mass concentration of the inorganic aluminum salt solution is 10 percent; the amount of potassium hydroxide satisfies OH^-/Al³⁺The molar ratio is 5.0;the molar ratio of propylamine to potassium hydroxide used was 0.7.

The aged material was heated to 200 ℃ for 5 hours. After washing, the product dried at 200 ℃ was calcined at 550 ℃ for 6 hours. XRD spectra of the 200 ℃ dried product and the 550 ℃ calcined product showed 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 growth rule of gamma-alumina cubic system relative to crystallography, the octahedron can only expose the crystal face of the { 111 } family. The size of the octahedron crystal grain is about 3 μm, the octahedron { 111 } family crystal face is approximately triangular, and the side length is about 0.8 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.