Evidence of ammonia synthesis by bulk diffusion in cobalt molybdenum particles in a CLAS process

For the first time ammonia-synthesis-on-nitridation has been reported in CoMo during a chemical looping ammonia synthesis experiment. The observation lends evidence to the existence of a dynamic surface, a shrinking core and counter diffusion. The Mars-van Krevlen mechanism involving surface and bulk exchange has been established for the CoMo system under H-2:N-2 atmospheres was extended into the CLAS domain and complicated by the existence of an unreacted oxide core containing molybdenum bronzes, HxMoO3. This OH-1 diffuses outward as the core is stabilized by N-3, resulting in the observation of gas phase H2O and NH3 in the absence of gaseous H-2.

Automated summary

This study reports the synthesis of ammonia on nitridation in CoMo for the first time during a chemical looping ammonia synthesis experiment. The results provide evidence for the presence of a dynamic surface, a shrinking core, and counter diffusion. The study also establishes the existence of an unreacted oxide core containing molybdenum bronzes, HxMoO3, which complicates the established Mars-van Krevlen mechanism.