Promoted iron Fischer-Tropsch catalysts: characterization by nitrogen sorption

Abstract

The effects of promoters on BET surface area and porosity of precipitated iron catalysts are examined. A series of metal oxide promoted iron catalysts was prepared by coprecipitation of the nitrate salts to produce 6% by weight of promoter oxide. Surface areas and pore volumes tend to decrease with increasing promoter ionic radius although there is essentially no change in the shape of the nitrogen isotherm or pore size distribution. Addition of alkali (K) or alkaline-earth (Ca) metals to silica or alumina promoted iron catalysts also results in a decrease in surface area and pore volume with increasing metal loading. The presence of alkali or alkaline-earth metals appears to impede crystallization during heating.