Ammonia synthesis with barium-promoted iron–cobalt alloys supported on carbon

• Published in: Journal of catalysis 2003-03, Vol.214 (2), p.327-335
• Main Authors: Hagen, Stefan, Barfod, Rasmus, Fehrmann, Rasmus, Jacobsen, Claus J.H, Teunissen, Herman T, Chorkendorff, Ib
• Format: Article
• Language: English
• Subjects: Ammonia synthesis; Barium; Catalysis; Catalytic reactions; Chemistry; Cobalt; Exact sciences and technology; General and physical chemistry; Iron; Kinetics; Promotion; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1016/S0021-9517(02)00182-3

Iron–cobalt alloys supported on carbon were investigated as ammonia synthesis catalysts. Barium was found to have a promoting effect for Fe with an optimum atomic ratio Ba/Fe of 0.35. At this Ba loading, a local maximum for the NH 3 synthesis activity was found at 4 wt% Co by varying the Fe/Co ratio. Samples containing only Co and no Fe, however, yielded by far the most active catalysts (7.0 μmol (NH 3) g −1 s −1 , 673 K, 10 bar). Barium was a very efficient promoter for Co, increasing the NH 3 synthesis activity by more than two orders of magnitude compared to the unpromoted Co samples, while it was not as effective for Fe. Power-law kinetic investigation revealed that, compared to the commercial Fe-based NH 3 catalyst, the Ba–Co/C samples showed a lower inhibition by NH 3 and were more active under ordinary ammonia synthesis conditions.