Study of the Kinetics of Ammonia Synthesis and Decomposition on Iron and Cobalt Catalysts

Abstract

Activity of cobalt and iron catalysts in ammonia synthesis was determined under a pressure of 10 MPa and at the temperature range of 673-823 K, in a sixchannel integral steel reactor. The catalytic ammonia decomposition was studied in a differential reactor under the atmosphere of low concentration of ammonia (\6%) in the temperature range of 673-823 K under atmospheric pressure. The determined values of the activation energy for the ammonia synthesis reaction over cobalt and iron catalysts are 268 and 180 kJ/mol, respectively, whilst for the ammonia decomposition reaction they are equal to 111 and 138 kJ/mol. The cobalt catalyst showed lower activity than a commercial iron catalyst in ammonia synthesis reaction. The cobalt catalyst turned out to be more effective in ammonia decomposition reaction than the iron one.

Ammonia decomposition over cobalt/carbon catalysts—Effect of carbon support and electron donating promoter on activity

“…The I D /I G ratio is related to the orderliness of the graphite structure and is inversely proportional to the microcrystalline planar size, which corresponds to the in-plane dimension of a single microcrystallite in graphite [26]. According to this parameter, the degree of graphitisation of the different carbon supports follows the trend of MESO-C > Activated charcoal > MSC-30 > CNTs > Ax- 21.…”

“…activity to that of Ni/CNT and Fe/CNT [20]. A recent kinetic study by Lendzion-Bielun et al [21] showed a lower ammonia decomposition activation energy on cobalt than on iron-based catalysts. Previous studies suggest that the catalytic activity of cobalt-based catalysts can be related to i. the level of dispersion and crystallite size [22] and ii.…”

H2 Production via Ammonia Decomposition Using Non-Noble Metal Catalysts: A Review

“…While the ammonia molecule needs to be adsorbed on the active metal to be activated, strongly adsorbed N adatoms would, on the other hand, poison the metal active sites. Therefore, there exists an optimum nitrogen binding energy for ammonia decomposition catalysts within the range of 544-586 kJ mol -1 , with the optimum activity observed at 561 kJ mol -1 , lower than that for ammonia synthesis catalysts [27][28][29].…”

“…A kinetic study by LendzionBielun et al [27]. Calculated the activation energy for NH 3 decomposition to be 27 kJ mol -1 lower on cobalt than on iron-based catalysts.…”

“…basicity and electron conductivity) [56] as well as the presence of promoters have been explored in order to understand their role and facilitate the development of active cobalt-based catalysts. Based on the current literature, the active cobalt phase for ammonia decomposition has not been clearly identified, although some reports suggest that it is metallic cobalt [27].…”