A Study of 15N/14N Isotopic Exchange over Cobalt Molybdenum Nitrides

The N-14/N-15 isotopic exchange pathways over Co3Mo3N, a material of interest as an ammonia synthesis catalyst and for the development of nitrogen transfer reactions, have been investigated. Both the homomolecular and heterolytic exchange processes have been studied, and it has been shown that lattice nitrogen species are exchangeable. The exchange behavior was found to be a strong function of pretreatment with ca. 25% of lattice N atoms being exchanged after 40 min at 600 degrees C after N-2 pretreatment at 700 degrees C compared to only 6% following similar Ar pretreatment. This observation, for which the potential contribution of adsorbed N species can be discounted, is significant in terms of the application of this material. In the case of the Co6Mo6N phase, regeneration to Co3Mo3N under N-15(2) at 600 degrees C occurs concurrently with (NN)-N-14-N-15 formation. These observations demonstrate the reactivity of nitrogen in the Co-Mo-N system to be a strong function of pretreatment and worthy of further consideration.