The Preparation of Activated Alumina Catalyst Carrier

Activated alumina carrier is the most widely used catalyst carrier, and as an inert solid catalyst carrier, which accounts for about 70% of the supported catalysts in industry.Alumina has many kinds of forms,different forms of which will show different properties.Although same form with different sources will show different properties too,such as bulk density,pore structure,surface area,ect.Those properties have significance for alumina as catalyst.Alumina preparation is mostly from hydrogen oxide(called as hydrated alumina or alumina hydrate),the chemical properties are water-insoluble amphoteric oxide and soluble in inorganic acids and alkaline solutions.There are four isomers β-alumina, δ-alumina, γ-alumina, α-alumina, mainly in α-type and γ-type variants, which can be extracted from bauxite industrially.

The activated alumina carrier is used in the preparation of catalysts. The original purpose is to save the consumption of precious materials(such as Pd, Pt, Au),which are scattered and carried on bulky objects to replace whole metal materials.

Another purpose is to use a carrier with higher strength to improve the wear resistance and impact resistance of the catalyst.Therefore, the initial carrier is broken bricks, pumice and charcoal, etc., only considering the physical ,mechanical properties and low price.During the using process,we found big difference of catalyst performance will appear due to different carriers.So we began to pay attention to the selection of the carrier and conduct in-depth research.

Among them, activated alumina is one of the most important catalyst supportswhich is widely used in the field of petroleum processing catalysts.It is known that alumina has 8 crystal states, among which γ-Al2O3 has high pore volume,specific surface area and thermal stability, so it is widely used.One of the important properties of a catalyst support is its pore structure,which determines the pore structure of the catalyst.

The first requirement for the pore structure of the catalyst carrier is to provide the largest possible reaction contact area and improve the dispersion of active components.

The second is the pore size. If the pore size is too large, the specific surface area of the carrier will decrease.If the pore size is too small, it will adversely affect the diffusion of reactants,thus affecting the activity of the catalyst.

Therefore, γ-Al2O3 with suitable pore structure has become one of the important topics

in the development of catalysts.