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

Abstract

in Wiley InterScience (www.interscience.wiley.com).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 NO x removal from Diesel exhausts. Such a mechanistic model is consistent with the detailed catalytic chemistry proposed for the NH 3 -NO/NO 2 reacting system in which NO 2 disproportionates to form nitrites and nitrates, nitrates are reduced by NO to nitrites in a key redox step, and nitrites react with NH 3 to form N 2 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 NO 2 /NO x feed ratios in the 175-425 C temperature range. V U 2 ¼ 0:028 \ 0:08 Thus, also intraphase mass transfer limitations can be ruled out.

NH3–NO/NO2 SCR for Diesel Exhausts Aftertreatment: Reactivity, Mechanism and Kinetic Modelling of Commercial Fe- and Cu-Promoted Zeolite Catalysts

“…The experimental data were analyzed according to a dynamic one-dimensional isothermal heterogeneous PFR model of the test micro reactor [8,17,18].The rate parameters of all the reaction steps were estimated by global multiresponse nonlinear regression. Further details can be found in [8,10,18,19].…”

Experimental and numerical assessment of impingement and mixing of urea–water sprays for nitric oxide reduction in diesel exhaust

“…e.g. [3,4], the processes leading to the availability of NH 3 at the catalyst entrance are considerably less well studied. These encompass the injection of a urea-water solution in a cross-flow configuration, as well as thermolysis and hydrolysis reactions taking place in the hot gas consequently providing the reducing agent.…”

The Role of Fe2O3 Species in Depressing the Formation of N2O in the Selective Reduction of NO by NH3 over V2O5/TiO2-Based Catalysts

“…The standard Reaction (1) takes place in the presence of excess oxygen, while Reaction (2) has been known as the fast SCR pathway in an equimolar mixture of NO and NO 2 and is known to be much faster than the Reaction (1) at low temperatures [6,9,10].…”