Modelling Both the NH3 Storage on Automotive SCR Catalysts and the Radio-Frequency-Based Response

Since the ammonia (NH3) based selective catalytic reduction is today’s main DeNOx strategy to meet the emission limits for Diesel cars, research focuses on sensor and control approaches for higher conversion efficiencies and system robustness. One novel approach is the catalyst state monitoring based on radio frequencies (RF). It has proven its functionality to monitor the NH3 loading on SCR catalysts directly in previous studies. This study shows the first attempt to fully describe the whole RF SCR system by simulation. A divided model into the chemical reactions and the RF response is presented and parameterized on experimental test runs. The application of the adjusted model on a test run that was not included in parameter fitting correlates well with the simulated signals and the measured catalyst behavior as well as with the RF response.