MODELING OF AMMONIA-SYNTHESIS KINETICS

This paper presents a brief review of recent results from the theoretical modelling of ammonia synthesis, based upon kinetic data from single crystals and catalysts. The conclusion from this work is that correct predictions of industrial yields can only be made by including a highly activated step of nitrogen dissociation from the gas phase. This fits with recent experimental evidence that nitrogen dissociation on Fe(111) is thermally activated, a finding supported by theoretical calculations and older work on real catalysts. Models which do not include this activation barrier predict low yields of ammonia. Experimental work on single crystals indicates that the "active site" is intimately connected with the two major promoters (alumina and potash) and that these play a multiplicity of roles.