The Haber–Bosch Process Revisited: On the Real Structure and Stability of “Ammonia Iron” under Working Conditions

In situ neutron diffraction was used to study the structural properties of an industrial ammonia synthesis catalyst under working conditions similar to those of the Haber–Bosch process. Despite favorable thermodynamics, no indications of reversible bulk nitridation of the iron catalyst was observed in a self-generated ammonia concentration of 12 vol % at 425 °C and 75 bar after 88 h on stream.