EFFECT OF COBALT ON THE MORPHOLOGY AND ACTIVITY OF FUSED IRON CATALYST FOR AMMONIA-SYNTHESIS

BET, scanning electron microscopy, X-ray diffraction, Mossbauer spectroscopy and X-ray florescence spectroscopy were used to investigate the effect of cobalt on the morphology and activity of fused iron catalyst for ammonia synthesis. Activity tests were carried out under 10 MPa in the 350-450-degrees-C temperature range. Investigations were performed on the traditional multipromoted iron catalyst and on a series of catalysts prepared with addition of cobalt. Introduction of cobalt increased the activity of the iron catalyst. The maximum effect was observed for 5.5 wt.-% Co. Moreover, activating action was stronger at lower temperatures. Addition of cobalt caused a change in catalysts structure. Co2+ ions were incorporated in the crystal lattice of wustite and magnetite. They changed the surface structure and the relation Fe2+/Fe3+, however the relation of bivalent to threevalent metal ions was not affected. The change of the catalyst structure in the unreduced form produced a catalyst that possessed other surface properties. The most active catalyst adsorbed less nitrogen than those without cobalt.