The simultaneous effect of promoters and water on the reduction of an iron catalyst for ammonia synthesis

Abstract

The rate of reduction of magnetite by gaseous hydrogen is slightly affected by water vapour (1%). However, this effect of water vapour is significant in iron catalysts for ammonia synthesis of the KM I type. Promoted magnetite is the main component of the iron catalyst and it is concluded therefore that the influence of water is applicable only when promoters are present. The validity of the core-and-shell reduction model, assuming a Langmuir-Hinshelwood kinetic equation which describes the reaction at the oxide/iron interface, is discussed on the basis of the kinetic data for unpromoted and promoted iron catalysts. It is found that the model is generally valid, except for the case of advanced reduction of promoted catalyst in a moist atmosphere.