Characterization of Cu and K containing Fe/Mn oxide catalysts for fischer‐tropsch synthesis

Copper and potassium containing Fe/Mn oxide catalysts for Fischer‐Tropsch synthesis were investigated by X‐ray microprobe technique, scanning electron microscopy, low‐temperature argon sorption and carbon monoxide and carbon dioxide chemisorption at −80°C. The specific surface areas of the catalysts depend on the preparation method, e.g. addition of K or Cu by coprecipitation leads to an increase while impregnation results in a decrease in surface area. The resulting samples are inhomogeneous, as shown by all method. Mn and especially K accumulated on the surface of the catalysts. Addition of Cu and K considerably altered the selectivity and activity of the Fe/Mn oxide catalyst. High potassium contents produced high olefin to paraffin ratios but these catalysts became rapidly deactivated. Copper and a very small addition of potassium led to a very low olefin to paraffin ratio but showed a high and constant activity.