Storage models for ammonia synthesis over iron catalyst under periodic operation

Abstract Two models of possible nitrogen storage mechanisms in an iron catalyst during cycling of ammonia synthesis are examined. A surface storage model assumes two kinds of nitrogen adsorption sites on the catalyst surface. It is also assumed that chemical reaction can take place during the surface diffusion of nitrogen atoms between these sites. A bulk dissolution model also assumes dual nitrogen sites. With a well-mixed gas phase, it is shown that the surface storage model and bulk dissolution model can predict enhancement of the time-average production rate of ammonia over the optimal steady-state rate as well as resonance behaviour.

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