Method for preparing superfine aluminum oxide through indirect oxidation of primary aluminum

Abstract

The invention discloses a method for preparing superfine aluminum oxide by indirect oxidation of primary aluminum, which comprises the following steps of: chlorinating the primary aluminum at high temperature by adopting AlCl3, converting aluminum in the primary aluminum into gas-phase AlCl, reacting the gas-phase AlCl with oxygen in a fluidized bed filled with an aluminum oxide bed material to generate aluminum oxide and gas-phase AlCl3, and circularly using the gas-phase AlCl3 for chlorination of the primary aluminum. According to the present invention, the primary aluminum is adopted as the aluminum source, the AlCl3 is adopted as the chlorinating agent, the oxygen is adopted as the oxygen source, and the ultrafine alumina powder is prepared through the chlorination-oxidation, such that the process is easy to adjust and control, the heat generated by the oxidation reaction can be effectively removed, the large-scale sintering of the product is prevented, the production cost is low, and the product is convenient to collect, high in purity and good in quality. Meanwhile, the cyclic utilization rate of system materials is high, large-scale efficient preparation of superfine aluminum oxide can be achieved, and good economic benefits and social benefits are achieved.

Description

Technical Field

[0001] The invention relates to the fields of chemical industry and metallurgy, and in particular to a method for preparing ultrafine alumina by indirect oxidation of raw aluminum. Background Art

[0002] High-purity ultrafine alumina powder has the characteristics of high wear resistance, high temperature corrosion resistance, high resistivity and high thermal conductivity, and is widely used in mechanical industry, refractory materials, electronics industry, petrochemical industry, aerospace and other fields.

[0003] At present, the preparation methods of ultrafine alumina powder mainly include liquid phase method, solid phase method and gas phase method. The liquid phase method is to select one or more soluble aluminum salts and precipitants, generate precipitation, and then dehydrate and decompose to prepare alumina powder, including hydrothermal synthesis method, sol-gel method, microemulsion method, organic alcohol salt hydrolysis method and chemical coprecipitation method, among which chemical coprecipitation method has become the main method for industrial production of ultrafine alumina powder by liquid phase method due to its simple equipment, high yield and large-scale production. However, the chemical coprecipitation method is more complicated to operate and has many steps, and the obtained product particle size is larger and unevenly distributed. The solid phase method includes mechanical ball milling method, solid phase reaction method, ammonium aluminum sulfate thermal decomposition method and amorphous crystallization method. The solid phase method is simple and easy to operate, with large output and short production cycle, but the product purity is low, and there are also problems such as wide and uneven distribution of product particle size, which makes it difficult to apply in high-end fields. The gas phase method refers to the aluminum source being heated by electric arc, laser, plasma, etc. to become gas, and then reacting in an oxidizing atmosphere to generate aluminum oxide powder, including laser-induced vapor deposition, plasma vapor synthesis, and chemical vapor deposition. Compared with the liquid phase method and the solid phase method, the advantages of the gas phase method are simple operation, easy control of reaction conditions, and high product purity. The most commonly used gas phase method is the chemical vapor deposition method, that is, gas phase aluminum chloride reacts with hydrogen and oxygen to generate ultrafine aluminum oxide and hydrogen chloride, but there are problems such as high production cost, easy corrosion of equipment, and difficulty in product collection, which makes it difficult to apply on a large scale. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention aims to provide a method for preparing ultrafine alumina by indirect oxidation of primary aluminum.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] A method for preparing ultrafine alumina by indirect oxidation of primary aluminum comprises the following steps:

[0007] S1. Chlorination: using gas phase AlCl 3 Chlorination of raw aluminum to obtain gaseous AlCl;

[0008] S2, oxidation: using oxygen to oxidize the gaseous AlCl obtained in step S1 to obtain gaseous AlCl3 and amorphous alumina; gas phase AlCl 3 The amorphous aluminum oxide is sent to the chlorination process of step S1, and the amorphous aluminum oxide is sent to the crystallization process of step S3;

[0009] S3, crystallization: crystallize the amorphous aluminum oxide obtained in step S2 to obtain an aluminum oxide product.

[0010] Furthermore, in step S1, the chlorination temperature is 1050-1250°C.

[0011] Furthermore, in step S2, the oxidation temperature is 670-800°C.

[0012] Furthermore, in step S2, the oxidation reactor is a fluidized bed reactor, and the fluidized bed reactor is provided with a bed material, and the bed material is alumina with a particle size of 0.5-2 mm; the fluidized bed reactor is provided with an indirect heat exchange device.

[0013] Furthermore, in step S3, the crystallization temperature is 1300-1500° C., and the crystallization time is 0.5-5 h.

[0014] The beneficial effects of the present invention are:

[0015] 1. The present invention uses primary aluminum as the aluminum source and AlCl 3 Using oxygen as the chlorinating agent and oxygen as the oxygen source, ultrafine alumina powder is prepared by chlorination-oxidation. Compared with the one-step direct combustion method, the process is easier to adjust and control, has stronger operability, and the quality of the obtained product is better;

[0016] 2. The present invention uses a fluidized bed with an alumina bed material to carry out the oxidation reaction of gas-phase AlCl and oxygen. The fluidized bed has a fast mass transfer and heat transfer rate, which can effectively remove the heat generated by the reaction. At the same time, the alumina bed material can provide nucleation sites and matrix for the oxidation reaction, promote the occurrence of the oxidation reaction, and the obtained product is easy to collect and has high purity;

[0017] 3. AlCl in the present invention 3 It is consumed as a chlorinating agent in the chlorination reaction step and regenerated as a by-product in the oxidation reaction step. It can be recycled in the system, effectively reducing production costs.

[0018] 4. The present invention provides an indirect heat exchange device in the fluidized bed to timely remove the heat released by the reaction of gas phase AlCl and oxygen, which can effectively avoid the large-scale sintering of the product, and the obtained product has fine particle size and narrow distribution;

[0019] 5. The present invention can efficiently convert aluminum resources in raw aluminum into high-value-added alumina, with significant economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a method flow chart of each embodiment of the present invention;

[0021] Figure 2 This is an electron microscope scanning image of the aluminum oxide solid product obtained by the method of Example 1 of the present invention;

[0022] Figure 3 This is an electron microscope scanning image of the aluminum oxide solid product obtained by the method of Example 2 of the present invention;

[0023] Figure 4 This is an electron microscope scanning image of the aluminum oxide solid product obtained by the method of Example 3 of the present invention. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with the accompanying drawings. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to this embodiment.

[0025] Example 1

[0026] This embodiment provides a method for preparing ultrafine alumina by indirect oxidation of primary aluminum. Figure 1 As shown, the following steps are included:

[0027] S1. Chlorination: using gas phase AlCl 3 Chlorination of raw aluminum, wherein the raw aluminum is waste aluminum, the main element contained in the waste aluminum is aluminum, and it also contains multiple elements such as manganese, zinc, silicon, and copper, and the chlorination temperature is 1050° C. to obtain gaseous AlCl;

[0028] S2, oxidation: The gaseous AlCl obtained in step S1 is oxidized by oxygen at a temperature of 800°C to obtain gaseous AlCl 3 and amorphous alumina. Gas-phase AlCl 3 The amorphous aluminum oxide is sent to the chlorination process of step S1, and the amorphous aluminum oxide is sent to the crystallization process of step S3. The reactor for the oxidation reaction is a fluidized bed reactor, in which a bed material is provided, and the bed material is aluminum oxide with a particle size of 0.5 mm. The fluidized bed reactor is provided with an indirect heat exchange device. Gas phase AlCl 3 Before entering the chlorination process of step S1, it is first passed into an indirect heat exchange device to exchange heat with the inside of the fluidized bed reactor, absorb the heat released by the oxidation reaction, and obtain high-temperature gas phase AlCl 3 , and then sent to the chlorination process of step S1 to make full use of the heat generated by the oxidation reaction.

[0029] S3, crystallization: the amorphous aluminum oxide obtained in step S2 is crystallized at 1300°C for 5 hours to obtain an aluminum oxide product. The morphology of the aluminum oxide product is as follows: Figure 2 As shown. Figure 2 It can be seen that the alumina solid product obtained in this embodiment has a narrow particle size distribution, and the average particle size is about 0.58 μm.

[0030] Example 2

[0031] The method flow of this embodiment is basically the same as that of embodiment 1, except that: in step S1, the temperature of the chlorination reaction is 1250°C; in step S2, the temperature of the oxidation reaction is 670°C, and the particle size of the alumina bed material is 2 mm; in step S3, the crystallization temperature is 1500°C, the crystallization time is 0.5 h, and the morphology of the alumina product is as follows: Figure 3 As shown. Figure 3 It can be seen that the alumina solid product obtained in this embodiment has a narrow particle size distribution, and the average particle size is about 0.35 μm.

[0032] Example 3

[0033] The method flow of this embodiment is basically the same as that of embodiment 1, except that: in step S1, the temperature of the chlorination reaction is 1100°C; in step S2, the temperature of the oxidation reaction is 800°C, and the particle size of the alumina bed material is 1 mm; in step S3, the crystallization temperature is 1400°C, the crystallization time is 3 hours, and the morphology of the alumina product is as follows: Figure 4 As shown. Figure 4 It can be seen that the alumina solid product obtained in this embodiment has a narrow particle size distribution, and the average particle size is about 0.45 μm.

[0034] For those skilled in the art, various corresponding changes and modifications can be made according to the above technical solutions and concepts, and all of these changes and modifications should be included in the protection scope of the claims of the present invention.

Claims

1. A method for preparing ultrafine alumina by indirect oxidation of primary aluminum, characterized in that: The following steps are involved: S1. Chlorination: Chlorination of raw aluminum using gaseous AlCl3 to obtain gaseous AlCl; S2, oxidation: using oxygen to oxidize the gas phase AlCl obtained in step S1 to obtain gas phase AlCl3 and amorphous aluminum oxide; the gas phase AlCl3 is fed to the chlorination process of step S1, and the amorphous aluminum oxide is fed to the crystallization process of step S3; S3, crystallization: crystallize the amorphous aluminum oxide obtained in step S2 to obtain an aluminum oxide product.

2. The method according to claim 1, characterized in that In step S1, the chlorination temperature is 1050-1250°C.

3. The method according to claim 1, characterized in that In step S2, the oxidation temperature is 670-800°C.

4. The method according to claim 1, characterized in that In step S2, the oxidation reactor is a fluidized bed reactor, and the fluidized bed reactor is provided with a bed material, and the bed material is alumina with a particle size of 0.5-2 mm; An indirect heat exchange device is provided in the fluidized bed reactor.

5. The method according to claim 1, characterized in that In step S3, the crystallization temperature is 1300-1500° C., and the crystallization time is 0.5-5 h.

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