The Role of Composition for Cobalt Molybdenum Carbide in Ammonia Synthesis

The performance of Co3Mo3N, Co3Mo3C, and Co6Mo6C for ammonia synthesis has been compared. In contrast to Co3Mo3N, which is active at 400 °C, a reaction temperature of 500 °C, which was preceded by an induction period, was necessary for the establishment of steady state activity for Co3Mo3C. Co6Mo6C was found to be inactive under the conditions tested. During the induction period, nitridation of the Co3Mo3C lattice was found to occur, and this continued throughout the period of steady state reaction with the material transforming in composition toward Co3Mo3N. Taken together, these observations demonstrate that ammonia synthesis activity in ternary cobalt molybdenum systems is associated with the presence of N in the 16c Wyckoff lattice site.