Scandium activating action in the catalytic synthesis of ammonia and investigation of this effect by the method of contact potential difference and of Moessbauer effect

It has been shown that overheating of iron catalysts used for ammonia synthesis and promoted with scandium oxide considerably increases their activity, both specific and total. Upon prolonged overheating, specific catalytic activity decreases almost to the initial value. Changes in activity have been correlated with variations of electron work function: a decrease in phi by 0.7-0.8 eV corresponds to the highest activity; overheating causes an increase in phi almost to the initial value. Analysis of Mossbauer spectra reveals a monotonous increase in line broadening as overheating goes on. It has been assumed that a rise in catalytic activity is caused by dissociation of scandium oxide and adsorption of scandium on the surface a-Fe. This is complicated by the formation of Sc solid solution in a-Fe which results in a monotonous increase in broadening of the Mossbauer spectrum lines with time over heating. The phenomenon observed has been analyzed quantitatively