508 Simulation analysis of surface chemical species and NO_x reduction improvement over a Fe-Zeolite catalyst in an NH_3-SCR system on a diesel engine

抄録

N0X reduction of SCR system is significantly worse at low temperature. This study thus aims at understanding the way enriching N0X conversion by analyzing SCR catalyst surface chemical species o2-, H+, NH4+, NH4N03, N03" and N02- both during supplying and cutting off NH3. The simulation analysis shows chemical reactions are much more active at upstream and upper layer than that at downstream and lower layer of the catalyst.Furthermore, the N0X conversion is enhanced when the catalyst temperature rises accordingly. This improvement of N0X reduction is attributed from fast chemical reaction rates when temperature is high. Remarkably, the N0X is still in a high conversion after immediately cutting nh3 supply for a quick period before recovering to the initial state due to the occurrence of nh4no3 decomposition. Consequently, it can be concluded that supplying and cutting off NH3 for a while is effective and helps improve the total NOx conversion.