Unifying redox kinetics for standard and fast NH3‐SCR over a V2O5‐WO3/TiO2 catalyst

A dynamic Mars–van Krevelen kinetic model that unifies Standard and Fast SCR reactions into a single redox approach is herein proposed for V‐based catalysts for NOx removal from Diesel exhausts. Such a mechanistic model is consistent with the detailed catalytic chemistry proposed for the NH3‐NO/NO2 reacting system in which NO2 disproportionates to form nitrites and nitrates, nitrates are reduced by NO to nitrites in a key redox step, and nitrites react with NH3 to form N2 via decomposition of unstable ammonium nitrite. Intrinsic kinetic parameters were estimated by global multiresponse nonlinear regression of 42 transient runs. The model accounts for stoichiometry, selectivity, and kinetics of the global SCR process, reproducing successfully both the steady‐state and transient behaviors of the SCR reacting system over the full range (0–1) of NO2/NOx feed ratios in the 175–425°C temperature range.