Ruthenium dissociative nitrogen adsorption

Dissociative adsorption only occurs to any significant extent on ruthenium, although there is direct evidence that, as on most transition metals, it does not occur on the close-packed Ru(OOOl) face " or even on the open faces in the absence of promoters. The heat of adsorption of dissociated nitrogen is, however, high on the Ru(OOOl) surface (184 kJ moP with p es of 1.3 x 10 The coverage of N, derived from the decomposition of ammonia, is approximately 100% at 600 K falling slowly to 10% at 800 K in 2 x 10" torr ammonia. 

Energetics of adsorption and dissociation of nitrogen on single crystal ruthenium surfaces... 

For ruthenium catalyst, same as iron, it was in general considered that dissociated adsorption of nitrogen was also rate determining step, but the reaction... 

The platinum group metals demonstrate clearly the impact of the key parameters that influence the efficiency of ammonia synthesis catalysts structure sensitivity, the heat of adsorption of reactants and products, and the roles of promoters and supports. The key requirement to minimize the activation energy for nitrogen dissociation limits the active metals to alkali-promoted ruthenium and osmium. Similar activities are then obtained, irrespective of the genesis of the alkali metal promoter (salt or metal), indicating that both convert to a similar... 

Nitrogen interacts weakly with most of the Group Vlll/Ib metals. Dissociative adsorption is only possible on iron, ruthenium, and on metals toward the left of the Periodic Table. This behavior correlates well with the enthalpy of metal nitride formation which is positive for copper, nickel, and cobalt nitrides, but negative for... 

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