Effect of K, Cs and Ba on the kinetics of NH3 synthesis over carbon-based ruthenium catalysts |
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Authors: | Wioletta Raróg Zbigniew Kowalczyk Jan Sentek Dominik Składanowski Jerzy Zieliński |
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Affiliation: | (1) Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-662 Warsaw, Poland;(2) Institute of Physical Chemistry PAS, Kasprzaka 44/52, 01-224 Warsaw, Poland |
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Abstract: | The kinetics of NH3 synthesis over carbon-based ruthenium catalysts promoted with barium or alkali was studied. Both the ammonia partial pressure dependencies of the reaction rates (T = 400°C, p = 63 bar, H2 : N2 = 3 : 1) and the pressure variations of the activity (T = 370°C, p= 4–63 bar, H2 : NN2 = 3 : 1) were found to be different for Ba and for the alkali (K, Cs). Ba–Ru/C proved to be more sensitive to the NH3 content and to the total pressure. The rate of synthesis over the alkali-promoted catalysts is, in turn, much stronger influenced by the ruthenium dispersion. TOFs of NH3 synthesis for the promoted samples at 370°C and 4 bar (Ba 0.085 1/s, Cs 0.05 1/s, K 0.035 1/s) are significantly higher than that for the Ru(0001) basal plane (0.0085 1/s results from the literature data at 370°C, 2 bar). The most active Ru/C samples (Ba or Cs) exceed significantly the fused iron catalyst, especially at high conversions. |
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Keywords: | ammonia synthesis kinetics ruthenium catalysts promotional effect |
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