Multi-Site Modeling of the Urea/NH3-SCR over Fe-zeolites

Stavros  Skarlis, IFP Energies Nouvelles

Among the numerous techniques for the abatement of NOx from diesel engines exhaust stream, urea/NH3-SCR is a well established deNOx technology. Recently, Fe-zeolites are increasingly gaining attention due to their high deNOx efficiency and significant resistance to hydrothermal ageing. Storage and release of NH3 are probably the important processes for the dynamic behavior of the SCR catalyst. Thus, NH3 adsorption and desorption over Fe-ZSM5 catalysts were investigated through a multi-site approach where reaction rate expressions were based on the mean-field approximation. A kinetic model, including five different surface sites was formulated from literature data and validated over a broad range of NH3 adsorption and desorption experiments, showing the interest of the selected approach.

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