Microkinetic model for NO–CO reaction: Model reduction

Abstract

The objective of this work is to elucidate controlling mechanisms in NO x reduction, develop reduced-order reaction models, and analyze the reactor performance using the reduced-order reaction model for the NO-CO reaction. We start with the microkinetic model on platinum, which describes the mechanism of catalytic reduction of NO by CO. The formation of the main product N 2 and the competitive formation of the side product N 2 O are accounted for in the microkinetic model. Sensitivity and reaction path analysis have been carried out to determine the rate-limiting steps as well as the most abundant reactive intermediates in the system. Owing to the differences between system performance at high and low temperatures, the model has been analyzed in detail in these temperature regimes. Two closed-form expressions, corresponding to the two global reactions involved, have been derived. The characteristic features of the microkinetic model such as the sharp increase in NO conversion and the selectivity to N 2 O are captured well by the reduced model. The reduced-order model has been extended to the rhodium catalyst as well.

Transient Modeling of NOX Reduction in Automobile Exhausts

“…with time at three different temperatures. The system reaches steady state by t = 0.008 s. It can be seen that the selectivity is poor at lower temperatures as established in the steady state results [2].…”

“…[2]. Experimental results [3] are shown in symbols, while the results of PBR simulations using the global kinetic model [2] are shown in lines.…”

“…The steady state modelling of the above mentioned system gave the following plots with respect to temperature [2]. [2].…”

“…The importance of the undesirable side product N 2 O is considered explicitly in this kinetic model, and this is expected to be of particular importance for Pt catalyst based devices [1,2].…”

“…In order to model the catalytic converter, we make use of the kinetics of the reduction of NO in the presence of CO. Based on the micro-kinetic model developed earlier for the reduction of NO [1], reduced order rate expressions were arrived at in earlier work [2], according to which the following two global reactions are expected to occur:…”