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

BET, scanning electron microscopy, X-ray diffraction, Mossbauer spectr oscopy and X-ray florescence spectroscopy were used to investigate the effect of cobalt on the morphology and activity of fused iron catalys t for ammonia synthesis. Activity tests were carried out under 10 MPa in the 350-450-degrees-C temperature range. Investigations were perfor med on the traditional multipromoted iron catalyst and on a series of catalysts prepared with addition of cobalt. Introduction of cobalt inc reased the activity of the iron catalyst. The maximum effect was obser ved for 5.5 wt.-% Co. Moreover, activating action was stronger at lowe r temperatures. Addition of cobalt caused a change in catalysts struct ure. Co2+ ions were incorporated in the crystal lattice of wustite and magnetite. They changed the surface structure and the relation Fe2+/F e3+, however the relation of bivalent to threevalent metal ions was no t 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.