Microkinetic analysis ammonia synthesis

Fastrup, B. (1994) Temperature programmed adsorption and desorption of nitrogen on iron ammonia synthesis catalysts, and consequences for the microkinetic analysis of NH3 synthesis. Top. Catal., 1, 273. 

The ammonia synthesis reaction is one of the most widely studied reactions and it has been discussed previously in this text. (See Example 1.1.1, Table 5.2.1, and Section 5.3.) In this section, results from the microkinetic analysis of ammonia synthesis over transition metal catalysts containing either iron or mthenium will be presented. 

A microkinetic analysis of ammonia synthesis over transition metals is presented in Section 7.3. Use the results of that analysis to explain how adsorbed nitrogen atoms (N ) can be the most abundant reaction intermediate on iron catalysts even though dissociative chemisorption of N2 is considered the rate-determining step. 

In previous papers by the authors [9,10], the temperature-programmed desorption of N2 from an iron-based catalyst has been studied experimentally. The microkinetic analysis of these results is based on the kinetic simulation of ammonia synthesis by Stoltze and Nprskov [22-24] using the approach by Dumesic and Trevino [2]. On Fe single crystal surfaces it was possible to detect a di-molecular precursor labelled a-N2 — forN2 dissociation... 

S. Dahl, J. Sehested, C. Jacobsen, E. Tornqvist, and I. Chorkendorff, Surface science based microkinetic analysis of ammonia synthesis over ruthenium catalysts, Journal of Catalysis, vol. 192, pp. 391-399,2000. 

The microkinetics analysis, as a useful and powerful tool to interpret, harmonize and consolidate the study of catal3dic phenomena, can describe various results obtained at wide experimental conditions. For ammonia synthesis reaction discussed in this section, the microkinetic models are evaluated from the experimental data such as the sticking coefficient of dissociated nitrogen adsorption, the spectrum of programmed-temperature desorption of adsorbed nitrogen as well as the kinetics of ammonia synthesis at industrial conditions and at laboratory conditions are far from equilibrium. 

B. Fastrup, Microkinetic analysis of ammonia synthesis based on siarface reaction studies of iron catalysts as compared to single-crystal studies, J. Catal. 168 (1997) 235. 

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