Explanation of various physical properties of catalysts

Explanation of various physical properties of catalysts

Physical properties

Physical properties represent the shape, structure, density, particle size and other properties of the catalyst. They usually include five main items: specific surface area, pore volume, apparent bulk density, wear index, and sieving composition .The following are briefly described:

1. Specific surface area

The specific surface area of ​​a catalyst is the sum of the inner surface area and the outer surface area. The inner surface area refers to the surface area inside the catalyst pores, and the outer surface area refers to the outside of the catalyst pores. The surface area, usually the inner surface area is much larger than the outer surface area. The surface area per unit weight of the catalyst is called the specific surface area.

Specific surface area is an important indicator to measure the performance of catalysts. Different products have different carriers and preparation processes, so there is no direct correspondence between specific surface area and activity.

The method used to determine the specific surface area is the nitrogen adsorption capacity method.

2. Pore volume

Pore volume is a physical quantity that describes the pore structure of a catalyst. The pore structure not only affects the activity and selectivity of the catalyst, but also affects the mechanical strength, life and heat resistance of the catalyst.

Pore volume is the total volume of the micropores in the porous catalyst particles, and the unit is ml/g. The size of the pore volume is mainly related to the catalyst The carriers in are closely related. For the same type of catalyst, the pore volume will decrease and the pore diameter will increase during use.

The method used to measure pore volume is the water drop method.