A kinetic model for SCR coated particulate filters: Effect of ammonia-soot interactions

Journal article, 2019

SCR coated filters have recently been introduced. These combine soot capture through diesel particulate filters (DPF) and NOxremoval through ammonia selective catalytic reduction (NH3SCR). This study investigates the impact of soot on the reactions being important for the SCR process on Cu/SSZ-13, as well as the impact of different gases on soot oxidation using flow reactor measurements. A limited impact of soot on the SCR reactions and a clear inhibiting effect of NH3on soot oxidation, is found. Ammonia TPD, in-situ DRIFT, and XPS experiments are used to investigate the interaction between soot and ammonia. Amines/amides are found on the soot when exposed to NH3and H2O. The results are used to develop a kinetic model for soot oxidation over DPF and a soot coated Cu/SSZ-13 catalyst using diesel soot generated from an engine bench. It is found that it is important to incorporate a random pore model and a free edge site mechanism through which ammonia block these free edge carbons. The model describes well soot oxidation in the presence of NH3over DPF, as well as soot oxidation and the SCR mechanism over soot loaded Cu/SSZ-13.