GEOMETRIC FACTORS IN K AND AL PROMOTING OF THE FE MGO FISCHER-TROPSCHCATALYST/

The activity of K- and Al-promoted Fe/MgO catalyst for Fischer-Tropsch synthesis was measured under atmospheric pressure, with the aim to de termine the promoter's influence on the catalyst selectivity, particul arly in terms of olefins and isomers of lower hydrocarbons. The result s have been correlated to the data of a previous study on the same cat alyst, made under elevated pressure and designed for the alcohol produ ction. It has been concluded that the promoting effect of K should be attributed to a geometric influence rather than to electronic promotio n. The influence of Al promoter manifests itself like the ''skin effec t'', resulting in suppression of adsorption of both CO and H-2.