Modeling NOx Storage and Reduction for a Diesel Automotive Catalyst Based on Synthetic Gas Bench Experiments

To comply with stringent NO x emission regulations, automotive dies el engines require advanced aftertreatment catalytic systems, such as lean NO x traps (LNTs). Considering that test bench and chassis dyno experimental campaigns are costly and require a vast use of resources for the generation of data; therefore, reliable and computationally e ffi cient simulation models are essential in order to identify the most promising technology mix to satisfy emission regulations. In the literature, a large number of simulation models for LNT kinetics can be found, realized for laboratory-scale samples and validated over synthetic gas bench (SGB) experimental tests, while full-size models validated over engine-dyno driving cycle data, crucial for industrial applications, are missing. In the current work, a simulation model of an LNT device is built to predict NO x storage and reduction, starting from SGB laboratory tests and fi nally validated over driving cycle data. The experiments including light-o ff , NO x storage and reduction (NSR), and oxygen storage capacity (OSC) characterization, were performed on a laboratory-scale sample extracted from a full-scale monolith. Light-o ff tests have been conducted under a temperature ramp cycle from 120 ° Cto 380 ° C, while OSC and NSR tests were performed under isothermal conditions at fi ve temperature levels, ranging from 150 ° C to 400 ° C. OSC tests were performed to characterize oxygen storage capacity of ceria sites and water gas shift (WGS) reaction over the precious metals by controlling inlet species concentrations with periodic lean/rich pulses. NSR experiments were then performed by alternating a lean inlet composition to reproduce adsorption/desorption of NO x with a rich inlet composition feed with three reductants (H 2 , CO, and C 3 H 6 ) to replicate NO x reduction reactions. A global kinetic scheme was de fi ned by means of a one-dimensional (1D) engine simulation fl uid-dynamic code, GT-SUITE, to model oxidation reactions (CO, HC, NO), NO x adsorption/desorption, oxygen storage and NO x reduction reactions. The kinetic parameters were obtained using Arrhenius plots with the aim to minimize the error between simulated and experimental NO x , reductants, N 2 O and NH 3 concentrations, reaching a satisfactory agreement with measurements.