(69e) Mechanistic Transient Kinetic Analysis of the NH3-NO/NO2 SCR Reactions Over a Cu-Zeolite Catalyst for Automotive Applications | AIChE

(69e) Mechanistic Transient Kinetic Analysis of the NH3-NO/NO2 SCR Reactions Over a Cu-Zeolite Catalyst for Automotive Applications

Authors 

Nova, I. - Presenter, Politecnico di Milano
Colombo, M. - Presenter, Politecnico di Milano


 Tightening NOx emission standards for heavy-duty and passenger car engines require the development of highly efficient exhaust aftertreatment systems. One technology already adopted in Europe for heavy-duty applications to comply with EURO 4/5 regulations is the selective catalytic reduction (SCR) of NOx with NH3/urea. The new generation of SCR converters is based on zeolite catalysts promoted with transition metals (e.g. Cu, Fe) washcoated onto honeycomb monoliths. Such systems can better exploit the so called “Fast” SCR chemistry resulting from partial conversion of NO to NO2 over an upstream oxidation pre-catalyst; however little engineering work has been reported so far on the transient kinetics of this complex reacting system over zeolites. Drawing from our previous experience on V2O5-WO3/TiO2 and Fe-zeolite SCR catalysts, we have investigated by dynamic methods (step-response and temperature-programmed experiments) the intrinsic kinetics of the NH3-NO/NO2 reactions over a commercial copper exchanged zeolite powdered catalyst. The results are shown to be qualitatively and quantitatively consistent with a mechanistic model, closely in agreement with the details of the Fast SCR chemistry, which fully explains a variety of observed complex transient features. The accurate quantitative description of such transients is critical for model-based development of SCR converters in view of vehicle applications.

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