1. Properties of Activated Alumina

1.1 Specific Surface Area

In theory, the specific surface area of alumina can be as high as 360 m2/g if the sintering system of alumina is reasonably controlled. However, the pore size of activated alumina prepared by decomposition of NaAlO 2 into colloidal alumina hydroxide is very small, and the specific surface area can be as high as 600 m2/g.

1.2 Aperture Distribution

Owing to the strong bonding ability of Al-O, high vapor pressure is formed in the crystal when Al(OH)3 is heated and dehydrated to form H_2, which results in a wide distribution of micropore. Its pore size varies with Al(OH)3. Generally speaking, medium pore size products can be prepared by pure aluminium hydroxide. Activated alumina prepared from aluminium glue can produce products with smaller pore size. When some organic substances such as ethylene glycol and fibers are added to the preparation of activated alumina, larger pore size of activated alumina can be obtained after combustion, and even larger pore size can be obtained by sublimation.

2. Preparation and Properties of Activated Alumina Powder

Preparation of 2.1 Activated Alumina Powder

Activated alumina powder is prepared by mixing alumina water, such as alumina hydroxide, pseudo-boehmite, with different additives and controlling different roasting conditions. The specific technological process is as follows:

3. Characteristics of Activated Alumina Powder

The specific surface area is large, generally up to 350 m2/g. The product purity can be controlled by controlling the purity of raw materials, and the pore size distribution can be controlled by additives.

4. Application of Activated Alumina

The application of activated alumina is mainly in the field of adsorption and catalyst.

Application of 4.1 Activated Alumina in Adsorption Field

As an adsorbent, it is one of the main uses of activated alumina, mainly because of its large specific surface area, reasonable pore structure, good physical properties, good chemical stability and many other favorable factors. Its important industrial applications include drying gases, drying liquids, water purification and selective adsorption in the petroleum industry.

Application of 4.1.1 Activated Alumina in Gas Drying

Activated alumina has a strong affinity with water, so it has a very strong drying capacity for water in gas. In industrial desiccants, the drying capacity of calcium chloride, silica gel and calcium oxide is lower than that of activated alumina, only barium oxide is slightly higher than that of activated alumina. At the same time, because alumina has good chemical stability, only a few gases react with it, so there are many kinds of gases that it can dry. The literature introduces that it can dry more than 20 kinds of gases, such as acetylene, hydrogen, oxygen, air and nitrogen.

Application of 4.1.2 Activated Alumina in Liquid Drying

Liquid drying is much more complicated than gas drying, and the requirement of desiccant is relatively high. Firstly, when the liquid contacts with the adsorbent, no chemical reaction can take place between the components of the liquid and between the liquid and the oxygen adsorbent. Secondly, the adsorbed substance of the dry liquid can be washed away during regeneration. At present, the liquids that can be dried by alumina are aromatic hydrocarbons, macromolecule olefins, gasoline, kerosene and so on.

Application of 4.1.3 Activated Alumina in Water Purification

Activated alumina has been developing rapidly in the field of water purification. The treatment of water quality mainly focuses on the following aspects.

Removal of fluoride

Elimination of color and odor

(3) Phosphate removal

Alumina has a very good purification effect on the above three aspects, and the regeneration method is simple and cheap, so it has been rapidly promoted. With the increasing public awareness of the protection of water resources, people are more and more interested in this purification method.

Application of 4.2 Activated Alumina in Catalyst Field

In many industrial catalytic processes, alumina is not only used as catalyst itself, but also as carrier of active component of catalyst. With the improvement of forming method of active alumina catalyst carrier, many methods have been applied to catalyst carrier industry, such as block method, granulation method, compaction method, pelletizing extrusion method and so on. Therefore, it can be used as catalyst carrier of various shapes. 。