KINETICS AND ISOTOPE EFFECT OF AMMONIA SYNTHESIS OVER AN UNPROMOTED IRON CATALYST

The kinetics and deuterium isotope effect of the ammonia synthesis reaction over unpromoted iron catalyst have been studied at 305 °C. Some runs were carried out with mixtures of hydrogen and deuterium. The kinetic data as well as the isotope effect indicate that the rate-determining step is the chemisorption of nitrogen on a surface mainly covered with nitrogen atoms, and not with NH radicals as previously concluded for the doubly promoted catalyst. This result suggests that a part of the role of potash promoter is the change of the adsorbed species which retards the chemisorption process. © 1969.