阅读说明：本技术 一种高纯氧化铝的制备方法 (Preparation method of high-purity alumina ) 是由 王耀武 彭建平 桓书星 狄跃忠 于 2019-10-17 设计创作，主要内容包括：一种高纯氧化铝的制备方法,按以下步骤进行：(1)工业氧化铝磨细；(2)将氧化铝粉料与金属铝粉混合制成混合粉料；(3)加入粘结剂混合后压制成球团；(4)在真空、氩气或覆盖条件下,将球团烘干制成干球团；(5)干球团置于带有结晶器的真空还原炉,进行真空铝热还原反应；反应后剩余还原渣；(6)还原渣冷却至室温,取出后磨细,用氢氧化钠溶液碱浸；(7)过滤、水洗获得一次固相；(8)用盐酸酸浸,过滤、水洗、烘干制成高纯氧化铝。本发明的方法设备简单、成本低、可操作性强,可制备99.999％以上的高纯氧化铝。(The preparation method of the high-purity alumina comprises the following steps: (1) grinding industrial alumina; (2) mixing alumina powder and metal aluminum powder to prepare mixed powder; (3) adding a binder, mixing and pressing into pellets; (4) drying the pellets under vacuum, argon or covering conditions to prepare dry pellets; (5) putting the dry pellets into a vacuum reduction furnace with a crystallizer to carry out vacuum aluminothermic reduction reaction; reducing slag remained after the reaction; (6) cooling the reducing slag to room temperature, taking out, grinding, and performing alkaline leaching by using a sodium hydroxide solution; (7) filtering and washing to obtain a primary solid phase; (8) acid leaching with hydrochloric acid, filtering, washing and drying to prepare the high-purity alumina. The method has the advantages of simple equipment, low cost and strong operability, and can prepare over 99.999 percent of high-purity alumina.)

1. The preparation method of the high-purity alumina is characterized by comprising the following steps of:

(1) grinding industrial alumina to a particle size of less than or equal to 0.075mm to prepare alumina powder;

(2) mixing alumina powder and metal aluminum powder to prepare mixed powder; wherein the metal aluminum powder accounts for 0.5-3% of the total mass of the alumina powder; the grain diameter of the metal aluminum powder is less than or equal to 0.075 mm;

(3) adding a binder into the mixed powder, uniformly mixing, and pressing into pellets;

(4) drying the pellets for 1-10 h at 100-300 ℃ under the vacuum condition or argon atmosphere condition or in a mode of covering with alumina powder to prepare dry pellets;

(5) putting the dry pellets into a vacuum reduction furnace with a crystallizer, heating to 800-1300 ℃ under the condition that the vacuum degree is less than or equal to 10Pa, and preserving the heat for 1-10 h to perform vacuum aluminothermic reduction reaction; during the vacuum aluminothermic reduction reaction, metal sodium, metal calcium, metal magnesium, metal lithium and metal potassium are distilled out and enter a crystallizer for crystallization, and P formed by decomposing aluminum dihydrogen phosphate₂O₅Crystallizing in a crystallizer, wherein the residual material is reducing slag;

(6) cooling the reducing slag to room temperature along with the furnace, taking out the reducing slag, grinding the reducing slag to the grain size of less than or equal to 0.075mm, and then placing the reducing slag into a sodium hydroxide solution for alkaline leaching to enable unreacted metal aluminum in the reducing slag and simple substance silicon generated by reduction to react with sodium hydroxide to generate sodium aluminate and sodium silicate;

(7) filtering and washing the material after alkaline leaching until the washing liquid is neutral to obtain a primary solid phase; wherein sodium silicate and sodium aluminate enter the filtrate;

(8) placing the primary solid phase in hydrochloric acid for acid leaching, and reacting metallic iron in the primary solid phase with HCl to generate ferric chloride; filtering the acid-leached material and washing the material with water until the washing liquid is neutral to obtain a secondary solid phase, wherein ferric chloride enters the filtrate; drying the secondary solid phase to remove water, and preparing the high-purity alumina.

2. The method for preparing high-purity aluminum oxide according to claim 1, wherein the purity of the metal aluminum powder is more than or equal to 99%.

3. The method for preparing high-purity alumina according to claim 1, wherein the binder is an aluminum dihydrogen phosphate solution, the concentration of the aluminum dihydrogen phosphate solution is 10-60%, and the usage amount of the aluminum dihydrogen phosphate solution is 3-10% of the total mass of the mixed powder.

4. The preparation method of high-purity alumina according to claim 1, wherein in the step (3), the briquetting pressure when pressing into pellets is 20-200 MPa.

5. The preparation method of high-purity alumina according to claim 1, wherein in the step (4), the alumina powder is industrial alumina powder with a particle size of 0.075-0.15 mm.

6. The method for preparing high-purity alumina according to claim 1, wherein in the step (4), the vacuum condition is 0.1-100 Pa.

7. The preparation method of high-purity aluminum oxide according to claim 1, wherein in the step (6), the mass concentration of the sodium hydroxide solution is 3-25%, and the amount of the sodium hydroxide solution is 1-10 mL/g according to the liquid-solid ratio of the sodium hydroxide solution to the reducing slag.

8. The method for preparing high-purity alumina according to claim 1, wherein in the step (8), the mass concentration of the hydrochloric acid is 3-25%, and the amount of the hydrochloric acid is 1-10 mL/g according to the liquid-solid ratio of the hydrochloric acid to the solid component in the primary solid phase.

9. The method for preparing high-purity alumina according to claim 1, wherein the purity of the high-purity alumina is more than or equal to 99.999 percent.

Technical Field

The invention belongs to the technical field of metallurgy, and particularly relates to a preparation method of high-purity aluminum oxide.

Technical Field

The alumina is a high-hardness compound, the melting point is 2054 ℃, and the boiling point is 2980 ℃; the high-purity alumina is widely applied to the industries of abrasives, luminescent materials, single crystals, diaphragms, lithium ion batteries and the like due to stable chemical properties, good mechanical properties, thermal properties and sintering properties; with the rapid development of industries such as ceramics, medicine, lithium ion batteries and the like, the market has a larger growing space for the demand of high-purity alumina.

The aluminum sulfate ammonia process, the Bayer process, the hydrolysis process of high-purity aluminum powder and the aluminum alkoxide process are commonly used as the production methods of high-purity aluminum oxide.

The purity of the high-purity alumina produced by the aluminum-ammonia sulfate method and the Bayer method is relatively low and can only reach 99.99 percent; the aluminum powder hydrolysis method for producing high-purity aluminum oxide is to process a high-purity metal aluminum block into metal powder by using a metal cutter, the metal powder enters water for hydrolysis to obtain high-purity aluminum hydroxide, and the high-purity aluminum hydroxide is heated to prepare the high-purity aluminum oxide; however, in the production process of the method, although the metal cutter material is hard, iron and other metals need to be ground, alloy elements in the cutter enter water to generate iron hydroxide, nickel hydroxide, zirconium hydroxide and the like, and the hydroxides are inorganic substances which cannot be filtered and removed, and cannot be subjected to membrane separation and rectification; therefore, the purity of the alumina produced by the method reaches 99.995 percent at most.

The alumina produced by the aluminum alkoxide process is 1-2 orders of magnitude higher than that produced by the direct hydrolysis method of metallic aluminum, the aluminum sulfate ammonia process and the Bayer process; the aluminum alkoxide method comprises the steps of reacting 99.999% of metal aluminum blocks with isopropanol butanol or ethanol to obtain aluminum isopropoxide or aluminum ethoxide, rectifying at the temperature of 230 ℃ and 250 ℃ to remove impurities of front fraction and bottom fraction, gasifying rectified aluminum alkoxide, and condensing to obtain aluminum alkoxide liquid; performing high-purity ceramic membrane separation and purification at 230 ℃ to remove impurities such as potassium, sodium, zinc and the like; two times of purification are carried out; and hydrolyzing the aluminum alkoxide with high-purity water, finally, continuously separating by adopting a ceramic membrane at 150-160 ℃, removing impurities, and then, washing and purifying to obtain the high-purity aluminum hydroxide.

The high-purity aluminum oxide prepared by the aluminum-ammonia sulfate method and the Bayer method has lower purity, and the hydrolysis method of the high-purity aluminum powder and the alcohol aluminum method both use high-purity metal aluminum as raw materials to prepare the high-purity aluminum oxide, and have complex flow and high cost.

Disclosure of Invention

The invention provides a preparation method of high-purity alumina, which aims to solve the problems of the existing high-purity alumina preparation technology, and the preparation method comprises the steps of taking industrially produced alumina as a raw material, firstly carrying out aluminothermic reduction to reduce metal oxides such as sodium, iron and silicon in the industrial alumina into metal, simultaneously distilling the sodium in vacuum to separate the sodium from the alumina, carrying out alkali liquor leaching on the aluminothermic reduced alumina to remove aluminum and silicon in the alumina, then carrying out dilute acid leaching to remove metallic iron and other impurities in the alumina, simplifying the process and reducing the cost, and simultaneously realizing the purification of the alumina.

The method of the invention comprises the following steps:

(1) grinding industrial alumina to a particle size of less than or equal to 0.075mm to prepare alumina powder;

(2) mixing alumina powder and metal aluminum powder to prepare mixed powder; wherein the metal aluminum powder accounts for 0.5-3% of the total mass of the alumina powder; the grain diameter of the metal aluminum powder is less than or equal to 0.075 mm;

(3) adding a binder into the mixed powder, uniformly mixing, and pressing into pellets;

(4) drying the pellets for 1-10 h at 100-300 ℃ under the vacuum condition or argon atmosphere condition or in a mode of covering with alumina powder to prepare dry pellets;

(5) putting the dry pellets into a vacuum reduction furnace with a crystallizer, heating to 800-1300 ℃ under the condition that the vacuum degree is less than or equal to 10Pa, and preserving the heat for 1-10 h to perform vacuum aluminothermic reduction reaction; during the vacuum aluminothermic reduction reaction, metal sodium, metal calcium, metal magnesium, metal lithium and metal potassium are distilled out and enter a crystallizer for crystallization, and P formed by decomposing aluminum dihydrogen phosphate₂O₅Crystallizing in a crystallizer, wherein the residual material is reducing slag;

(6) cooling the reducing slag to room temperature along with the furnace, taking out the reducing slag, grinding the reducing slag to the grain size of less than or equal to 0.075mm, and then placing the reducing slag into a sodium hydroxide solution for alkaline leaching to enable unreacted metal aluminum in the reducing slag and simple substance silicon generated by reduction to react with sodium hydroxide to generate sodium aluminate and sodium silicate;

(7) filtering and washing the material after alkaline leaching until the washing liquid is neutral to obtain a primary solid phase; wherein sodium silicate and sodium aluminate enter the filtrate;

(8) placing the primary solid phase in hydrochloric acid for acid leaching, and reacting metallic iron in the primary solid phase with HCl to generate ferric chloride; filtering the acid-leached material and washing the material with water until the washing liquid is neutral to obtain a secondary solid phase, wherein ferric chloride enters the filtrate; drying the secondary solid phase to remove water, and preparing the high-purity alumina.

The purity of the metal aluminum powder is more than or equal to 99 percent.

The binder is aluminum dihydrogen phosphate solution, the concentration of the binder is 10-60%, and the usage amount of the binder is 3-10% of the total mass of the mixed powder.

In the step (3), the briquetting pressure for pressing the pellets is 20-200 MPa.

In the step (4), the alumina powder is industrial alumina powder, and the particle size is 0.075-0.15 mm.

In the step (4), the vacuum condition is 0.1-100 Pa.

In the step (5), the main reaction formula of the vacuum reduction reaction is as follows:

2Al(H₂PO₄)₃→Al₂O₃+P₂O₅+3H₂O (1)、

2Al+3Na₂O＝Al₂O₃+6Na (2)、

2Al+3K₂O＝Al₂O₃+6K (3)、

2Al+3Li₂O＝Al₂O₃+6Li (4)、

Al+Fe₂O₃＝Al₂O₃+Fe (5)、

4Al+3SiO₂＝2Al₂O₃+3Si (6)、

2Al+3MgO＝Al₂O₃+3Mg (7) and

2Al+3CaO＝Al₂O₃+3Ca (8)。

in the step (6), the mass concentration of the sodium hydroxide solution is 3-25%, and the dosage of the sodium hydroxide solution is 1-10 mL/g according to the liquid-solid ratio of the sodium hydroxide solution to the reducing slag.

In the step (7), the main reaction formula of the alkaline leaching is as follows:

2Al+2NaOH+6H₂O＝2NaAl(OH)₄+3H₂(9) and

Si+2NaOH+ H₂O＝Na₂SiO₃+2H₂(10)。

in the step (8), the mass concentration of the hydrochloric acid is 3-25%, and the dosage is 1-10 mL/g according to the liquid-solid ratio of the hydrochloric acid to the solid component in the primary solid phase.

In the step (8), the main reaction formula of acid leaching is as follows:

2Fe+6HCl＝2FeCl₃+3H₂(11)。

the purity of the high-purity alumina is more than or equal to 99.999 percent.

The main impurities of the industrial alumina are sodium oxide, silicon oxide and iron oxide, and in addition, a small amount of other metal oxides such as potassium oxide, lithium oxide, magnesium oxide, calcium oxide and the like are contained; the invention adopts a vacuum aluminothermic reduction method to reduce impurities in the industrial alumina into metal, removes metals with higher saturated vapor pressure such as sodium, magnesium, calcium, potassium, lithium and the like by a vacuum distillation mode, removes impurities which can react with alkali such as silicon and the like and redundant metallic aluminum by leaching with alkali, removes impurities which can react with acid such as iron and the like by acid leaching, simultaneously adopts a binding agent, aluminum dihydrogen phosphate, and generates alumina and volatile substances after high-temperature decomposition without influencing the purity of the alumina, thereby realizing the purification of the industrial alumina.

Drawings

FIG. 1 is a flow chart of a method for preparing high purity alumina according to an embodiment of the present invention.

Detailed Description

The alumina powder adopted in the embodiment of the invention is a commercial product.

The aluminum dihydrogen phosphate adopted in the embodiment of the invention is a commercial industrial-grade product.

In the embodiment of the invention, a ball mill is adopted for grinding.

The sodium hydroxide solution and the hydrochloric acid adopted in the embodiment of the invention are commercial industrial-grade products.

The vacuum reduction furnace adopted in the embodiment of the invention is vacuum reduction equipment for smelting magnesium by an industrial Pidgeon process.

In the embodiment of the invention, the water adopted in the water washing is deionized water.

In the embodiment of the invention, the alumina powder is industrial alumina powder, and the particle size is 0.075-0.15 mm.

In the embodiment of the invention, the vacuum condition of the step (4) is 0.1-100 Pa.

In the embodiment of the invention, the purity of the metal aluminum powder is more than or equal to 99%.