HC-SCR reaction pathways on ion exchanged ZSM-5 catalysts

Metal cation (metal = Cu, In and La) ion exchanged ZSM-5 zeolites as catalysts for the NO selective reduction by propane and propene in excess oxygen. The surface reactions of HC-SCR over catalysts were investigated through in situ DRIFTS method. For C3H8-SCR, adsorbed nitrate species (-NO3) were observed as main reaction intermediates and they could react with gaseous propane to produce N-2, H2O and CO2. While for C3H6-SCR, adsorbed amine species (-NH2) were observed as main reaction intermediates and they could react with NO or NO2 to produce the final products. The different reaction pathways for C3H8-SCR and C3H6-SCR over catalysts were proposed based on the DRIFTS results and the main factors controlling the activities of catalysts were discussed in details. The competing adsorption between NO-O-2 and HC-O-2 on the Bronsted acid sites of catalysts was responsible for the different reaction pathways in HC-SCR. (c) 2008 Elsevier Inc. All rights reserved.