Significance and Use

This test method has been found useful for the determination of the specific surface area of catalysts and catalyst carriers in the range from 0.05 to 10 m2/g for materials specification, manufacturing control, and research and development in the evaluation of catalysts. The determination of surface area of catalysts and catalyst carriers above 10 m2/g is addressed in Test Method D3663.

Scope

This test method covers the determination of the specific surface area of catalysts and catalyst carriers in the range from 0.05 to 10 m2/g. A volumetric measuring system is used to obtain at least three data points which fall within the linear BET region.

Summary of Test Method

A catalyst or catalyst carrier sample is degassed by heating in vacuum to remove absorbed vapors from the surface. The quantity of krypton adsorbed at various low pressure levels is determined by measuring pressure differentials after introduction of a fixed volume of krypton to the sample at liquid nitrogen temperature. The specific surface area is then calculated from the sample weight and adsorption data using the BET equation.

Apparatus

A schematic diagram of the apparatus is shown in Fig. 1. It may be constructed of glass or of metal and may operate manually or automatically. It has the following features:

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