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Conference Paper

Ruthenium as catalyst for ammonia synthesis

MPS-Authors
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Muhler,  Martin
Physical Chemistry, Fritz Haber Institute, Max Planck Society;

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Rosowski,  Frank
Physical Chemistry, Fritz Haber Institute, Max Planck Society;

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Hinrichsen,  Olaf
Physical Chemistry, Fritz Haber Institute, Max Planck Society;

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Hornung,  Alessandra
Physical Chemistry, Fritz Haber Institute, Max Planck Society;

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Ertl,  Gerhard
Physical Chemistry, Fritz Haber Institute, Max Planck Society;

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Citation

Muhler, M., Rosowski, F., Hinrichsen, O., Hornung, A., & Ertl, G. (1996). Ruthenium as catalyst for ammonia synthesis. In J. W. Hightower, W. N. Delgass, E. Iglesia, & A. T. Bell (Eds.), Proceedings of the 11th International Congress On Catalysis - 40th Anniversary (pp. 317-326). Elsevier.


Cite as: https://hdl.handle.net/21.11116/0000-0009-B4EF-F
Abstract
Five Ru-based catalysts were prepared to study the effect of the support and the role of the alkali promoter in NH3 synthesis: Ru/Al2O3, Ru/MgO, Cs-Ru/Al2O3 and Cs(K)−Ru/MgO. The catalysts were characterized by N2 physisorption, H2 chemisorption and XPS. The absence of chlorine- and sulphur containing compounds turned out to be important for the preparation of highly active catalysts. Power law expressions were derived from conversion measurements at atmospheric, pressure and at 20 bar. For all catalysts, the reaction order for H2 was found to be negative suggesting that a PN2/PH2 ratio in the feed gas higher than 1/3 would be favourable for industrial NH3 synthesis at high pressure. The microkinetic analysis of the temperature-programmed desorption and adsorption of N2 and of the kinetics of isotopic exchange demonstrated the enhancing influence of the Cs promoter on the rate of N2 dissociation and recombination. XPS measurements after through reduction revealed a shift of the Ru 3d5/2 peak to lower binding energy by about 1 e V in the presence of Cs suggesting an electronic promoter effect.