阅读说明：本技术 一种γ-氧化铝纳米晶粒及其制备方法 (Gamma-alumina nano-crystal and preparation method thereof ) 是由 杨卫亚 凌凤香 张会成 王少军 沈智奇 王丽华 于 2019-10-25 设计创作，主要内容包括：本发明公开了一种γ-氧化铝纳米晶粒及其制备方法。该晶粒为单晶结构,呈现八面体形貌,γ-氧化铝纳米晶粒暴露的8个等边三角形或近似等边三角形的表面都属于γ-氧化铝的｛111｝晶面族；三角形的边长为50～500nm；纳米晶粒大小为100～900nm。制备方法如下内容：(1)向温度为-70～-30℃的无机铝盐醇水溶液中加入温度为-70～-30℃的有机胺醇水溶液,混合均匀,然后加入冷冻为固相的无机碱溶液,搅拌条件下保温老化一定时间；(2)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-氧化铝纳米晶粒。本发明材料具有八面体形貌,并构成特殊的晶面暴露状况,在催化、吸附及陶瓷材料领域有着广阔的应用前景。(The invention discloses a gamma-alumina nano-crystalline and a preparation method thereof. The crystal grain is of a single crystal structure and presents an octahedral shape, and the surfaces of 8 equilateral triangles or approximately equilateral triangles exposed by the gamma-alumina nano crystal grain belong to a { 111 } crystal face family of gamma-alumina; the side length of the triangle is 50-500 nm; the size of the nano-crystalline grains is 100-900 nm. The preparation method comprises the following steps: (1) adding an organic amine alcohol aqueous solution at the temperature of-70 to-30 ℃ into an inorganic aluminum salt alcohol aqueous solution at the temperature of-70 to-30 ℃, uniformly mixing, then adding an inorganic alkali solution which is frozen into a solid phase, and preserving heat and aging for a certain time under the stirring condition; (2) 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 the gamma-alumina nano-crystalline particles. The material has the octahedral appearance, forms a special crystal face exposure condition, and has wide application prospects in the fields of catalysis, adsorption and ceramic materials.)

1. A gamma-alumina nanocrystal characterized by: the gamma-alumina nano-crystal grain is of a single crystal structure and presents an octahedral appearance, and the exposed surfaces of 8 equilateral triangles or approximately equilateral triangles of the gamma-alumina nano-crystal grain belong to the { 111 } crystal face group of gamma-alumina, and comprise (111), (-111), (1-11), (11-1), (-1-1-1), (-11-1) and (-1-11) crystal faces; the side length of the triangle is 50-500 nm; the size of the nano-crystalline grains is 100-900 nm.

2. A method for preparing the gamma-alumina nano-particles according to claim 1, characterized by comprising: (1) adding an organic amine alcohol aqueous solution at the temperature of-70 to-30 ℃ into an inorganic aluminum salt alcohol aqueous solution at the temperature of-70 to-30 ℃, uniformly mixing, then adding an inorganic alkali solution which is frozen into a solid phase, and preserving heat and aging for a certain time under the stirring condition; (2) 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 the gamma-alumina nano-crystalline particles.

3. The method of claim 2, wherein: the inorganic aluminum salt in the step (1) is one or more of aluminum chloride, aluminum nitrate or aluminum sulfate, the mass percentage concentration of the inorganic aluminum salt alcohol aqueous solution is 1-15%, the mass ratio of water to alcohol is 0.01-0.6, preferably 0.05-0.25, and the alcohol is methanol and/or ethanol.

4. The method of claim 2, wherein: the organic amine in the step (1) is one or more of methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, n-propylamine, ethanolamine, diethanolamine or triethanolamine, the mass percentage concentration of the organic amine alcohol aqueous solution is 1-15%, the mass ratio of water to alcohol is 0.01-0.6, preferably 0.05-0.25, and the alcohol is methanol and/or ethanol.

5. The method of claim 2, wherein: freezing the inorganic alkali solution in the step (1) to-150 to-70 ℃ to form a solid phase.

6. The method of claim 2, wherein: the inorganic base in the step (1) is sodium hydroxide and/or potassium hydroxide, the used solvent is water or an alcohol-water mixture, the proportion of the alcohol-water mixture is the proportion capable of forming a solid phase under the condition of freezing temperature of-150 to-70 ℃, and the alcohol is methanol and/or ethanol.

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

8. The method of claim 2, wherein: the mass percentage concentration of the inorganic alkali solution in the step (1) is 5-30%.

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

10. The method of claim 2, wherein: the aging temperature in the step (1) is-70 to-30 ℃, and the aging time is 5 to 120 minutes.

11. The method of claim 2, wherein: the closed hydrothermal treatment conditions in the step (2) are as follows: the temperature is 100-250 ℃ and the time is 0.5-72 hours.

12. The method of claim 2, wherein: the drying temperature in the step (2) is not more than 250 ℃, and the drying degree is the constant weight of the material at the drying temperature; the roasting conditions in the step (2) are as follows: roasting at 450-750 ℃ for 1-24 hours, preferably at 500-650 ℃ for 3-12 hours.

13. The use of the gamma-alumina nano-particles of claim 1 in the high-efficiency hydrodesulphurization of light gasoline, the selective hydrodeolefination of catalytic gasoline and the deep hydrodesulfurization reaction of distillate oil.

Technical Field

The invention belongs to the field of inorganic material preparation, and particularly relates to gamma-alumina nano-crystalline particles 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. Dissolving inorganic aluminum salt and organic additive in solvent to form solution, and carrying out hydrothermal treatment to obtain the octahedral aluminum oxide precursor. XRD spectrum of the product after roasting at 200 ℃ shows that the octahedron alumina does not have boehmite or pseudo-boehmite structure, so that the octahedron alumina cannot be converted into gamma-alumina under the conventional roasting condition of 500-700 ℃, and the application requirement of the catalysis field is difficult to be well met.

Disclosure of Invention

The invention provides a gamma-alumina nano-crystalline and a preparation method thereof, aiming at the defects of the prior art, the invention uses specific types of organic alkali and inorganic alkali as a crystalline morphology regulator to ensure that an alumina precursor is subjected to specific rearrangement under a certain chemical environment to form an octahedron morphology and form a special crystal face exposure condition, and has wide application prospect in the fields of catalysis, adsorption and ceramic materials.

The gamma-alumina nanocrystal is of a single crystal structure and presents an octahedral appearance, and the exposed surfaces of 8 equilateral triangles or approximately equilateral triangles of the gamma-alumina nanocrystal belong to the { 111 } crystal face group of gamma-alumina, including (111), (-111), (1-11), (11-1), (-1-1-1), (11-1), (-11-1) and (-1-11) crystal faces; the side length of the triangle is 50-500 nm; the size of the nano-crystalline grains is 100-900 nm.

The preparation method of the gamma-alumina nano-crystalline particles comprises the following steps:

(1) adding an organic amine alcohol aqueous solution at the temperature of-70 to-30 ℃ into an inorganic aluminum salt alcohol aqueous solution at the temperature of-70 to-30 ℃, uniformly mixing, then adding an inorganic alkali solution which is frozen into a solid phase, and preserving heat and aging for a certain time under the stirring condition;

(2) 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 the gamma-alumina nano-crystalline particles.

In the method, the inorganic aluminum salt in the step (1) is one or more of aluminum chloride, aluminum nitrate or aluminum sulfate, the mass percentage concentration of the alcohol aqueous solution of the inorganic aluminum salt is 1-15%, the mass ratio of water to alcohol is 0.01-0.6, preferably 0.05-0.25, and the alcohol is methanol and/or ethanol.

In the method, the organic amine in the step (1) is one or more of methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, n-propylamine, ethanolamine, diethanolamine or triethanolamine, the mass percentage concentration of the organic amine alcohol aqueous solution is 1-15%, the mass ratio of water to alcohol is 0.01-0.6, preferably 0.05-0.25, and the alcohol is methanol and/or ethanol.

In the method, the inorganic base in the step (1) is sodium hydroxide and/or potassium hydroxide, the inorganic alkali solution is frozen to-150 to-70 ℃ and forms a solid phase, the used solvent can be water or an alcohol-water mixture, the proportion of the alcohol-water mixture is the proportion capable of forming the solid phase under the condition of the freezing temperature, and the alcohol is methanol and/or ethanol. The mass percentage concentration of the inorganic alkali solution is 5-30%; the inorganic base and the inorganic aluminum salt are replaced by OH^-/Al³⁺The calculated molar ratio is 3-7,

in the method, the molar ratio of the organic amine to the inorganic base in the step (1) is 0.2-1.

In the method, the aging temperature in the step (1) is-70 to-30 ℃, and the aging time is 5 to 120 minutes.

In the method, the closed hydrothermal treatment conditions in the step (2) are as follows: the temperature is 100-250 ℃, preferably 120-200 ℃, and the time is 0.5-72 hours, preferably 2-12 hours.

In the method of the invention, the drying temperature in the step (2) 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 (2) are as follows: roasting at 450-750 ℃ for 1-24 hours, preferably at 500-650 ℃ for 3-12 hours.

The gamma-alumina nano-crystalline particles can be used as a carrier material of a catalyst for high-efficiency hydrogenation sweetening of light gasoline, selective hydrogenation olefin reduction of catalytic gasoline, deep hydrogenation desulfurization of distillate oil and the like.

Drawings

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

FIG. 2 is an electron diffraction pattern of alumina nano-particles after baking at 550 ℃ in example 1.

FIG. 3 is the XRD spectrum of alumina nano-crystalline particles after drying at 200 ℃ in example 1.

FIG. 4 is the XRD spectrum of alumina nano-crystalline particles after baking 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 the alumina nano-crystalline particles are observed and measured according to 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 (water and ethanol are used as solvents), cooling the solution to-35 ℃, slowly adding a methylamine solution (water and ethanol are used as solvents) at the temperature of-50 ℃, uniformly stirring, then adding a quantitative sodium hydroxide solution (in the form of ice blocks, the mass percentage of the sodium hydroxide is 10%) at the temperature of-100 ℃, continuously stirring, and finally aging for 70 minutes at the temperature of-50 ℃. The mass ratio of water to ethanol is 0.45; the mass percentage concentration of the inorganic aluminum salt solution is 8 percent; the amount of sodium hydroxide satisfies OH^-/Al³⁺The molar ratio is 5; the molar ratio of methylamine to sodium hydroxide used was 0.7.

The aged material was heated to 130 ℃ for 12 hours. After the reaction, the sample was washed, and the product dried at 200 ℃ was calcined at 550 ℃ for 6 hours. XRD spectra of the 200 ℃ dried product and the 550 ℃ calcined product show that the materials correspond to 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 700nm, the crystal face of the octahedron { 111 } family is approximately triangular, and the side length is about 280 nm. The octahedral crystal particle theoretically has a { 111 } family crystal face accounting for 100%.

Example 2

Preparing an aluminum nitrate solution, cooling the solution to-90 ℃ (the solvent is water and methanol), slowly adding a trimethylamine solution at-60 ℃ (the solvent is water and methanol), uniformly stirring, then adding a quantitative potassium hydroxide solution at-130 ℃ (in the form of ice blocks, wherein the mass percentage of the potassium hydroxide is 7%), continuously stirring, and finally aging for 100 minutes at-90 ℃.

The mass ratio of water/methanol was 0.40; the mass concentration of the inorganic aluminum salt solution is 15 percent; the amount of potassium hydroxide satisfies OH^-/Al³⁺The molar ratio is 4; the molar ratio of trimethylamine to potassium hydroxide used was 0.5.

The aged material was heated to 150 ℃ for 9 hours. After the reaction, the sample was washed, and the product dried at 200 ℃ was calcined at 550 ℃ for 6 hours. XRD spectra of the 200 ℃ dried product and the 550 ℃ calcined product show that the materials correspond to 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 550nm, the octahedron { 111 } family crystal face is approximately triangular, and the side length is about 180 nm. The octahedral crystal particle theoretically has a { 111 } family crystal face accounting for 100%.

Example 3

Preparing an aluminum nitrate solution, cooling the solution to-100 ℃ (the solvent is water and methanol), slowly adding an ethanolamine solution (the solvent is water and methanol) at-60 ℃, stirring uniformly, then adding a quantitative sodium hydroxide solution (in the form of ice blocks and with the mass percentage of the sodium hydroxide being 15%) at-130 ℃, continuously stirring, and finally aging for 100 minutes at-100 ℃.

The mass ratio of water/methanol was 0.25; the mass concentration of the inorganic aluminum salt solution is 10 percent; the amount of sodium hydroxide satisfies OH^-/Al³⁺The molar ratio is 6; the molar ratio of ethanolamine to sodium hydroxide used was 0.8.

The aged material was heated to 200 ℃ for 4 hours. After the reaction, the sample was washed, and the product dried at 200 ℃ was calcined at 550 ℃ for 6 hours. XRD spectra of the 200 ℃ dried product and the 550 ℃ calcined product show that the materials correspond to 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 760nm, the crystal face of the octahedron { 111 } family is approximately triangular, and the side length is about 340 nm. 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 6 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.