Calibration of a model for selective catalytic reduction with ammonia, including NO oxidation, and simulation of NOx reduction over an Fe–zeolite catalyst under highly transient conditions

Abstract

NOx reduction over an Fe–zeolite catalyst is simulated for highly transient conditions representative of automotive diesel engine operation. A transient 1D convection + 1D diffusion (1D + 1D) model for a single channel of a catalytic converter is developed, including a set of the most recently proposed kinetics for Fe–zeolite catalysts. The parameters specifying the characteristics of the selective catalytic reduction system are introduced, and an efficient calibration procedure is proposed that exploits the specific structure of the experimental dataset, consisting of a total of 90 operating conditions with varying space velocities, temperatures and inlet concentrations. Parameterization of the system is carried out by studying the system response to single step feeds in the inlet ammonia up to steady state (slow transient). Experimental data for highly dynamic ammonia dosing is subsequently employed to assess the model performance at highly transient conditions typical of diesel engine operation. Excellent agreement is reported for a total of 90 operating conditions; differences between the predictions and the experimental data in cumulative converted NOx after 20,000 s of operation are less than 2%.