Preparation of Activated Alumina Catalyst

Alumina used for catalyst or catalyst carrier has certain requirements in terms of physical properties and structure. 

The most basic ones are specific surface area, pore structure, crystal structure, etc. 

For example, the reforming catalyst is the precious metals platinum and rhenium supported on γ-Al2O3 or η-Al2O3. 

The structure of alumina has a great influence on the reaction activity. When it is loaded on other forms of alumina, its activity is very low.

For example, as a hydrocarbon dehydrogenation catalyst, if Cr-K is loaded on γ-Al2O3 or η-Al2O3, 

The activity is good, while the activity is very poor when loaded on other forms of alumina. 

This shows that it not only acts as a carrier, but also acts as an active component. Therefore, this alumina is also called activated alumina. 

α-Al2O3 is an inert substance in the reaction and can only be used as a carrier. 

The preparation method of activated alumina is different, the structure of the product obtained is also different, and its activity is quite different. 

Therefore, the conditions of each step should be strictly controlled in the preparation, and impurities should not be mixed. 

Although there are many preparation methods and routes, no matter which one. 

All routes must be made into alumina hydrate (aluminum hydroxide), and then dehydrated at high temperature to form alumina. 

The alumina existing in nature or the alumina produced by the dehydration of aluminum hydroxide cannot be used as a carrier or catalyst, 

not only because of the large amount of impurities, but also because it is difficult to obtain the required structure and catalytic activity. To this end, it must be reprocessed. 

It can be seen that the preparation of alumina hydrate is the basis for the preparation of active Al2O3. 

Alumina hydrate is analyzed by X-ray, and it can be seen that there are various forms, which are usually divided into crystalline state and amorphous state. 

In the crystalline state, there are two forms of water and trihydrate; the amorphous state contains two forms of amorphous and very low crystallinity, both of which are in the gel state.