Enhanced Selective Oxidation of Ammonia in a Pt/Al2O3@Cu/ZSM-5 Core Shell Catalyst

The ammonia slip catalyst (ASC) is an essential final step in the emission control system and involves the selective oxidation of NH3 to N2. The state-of-the-art ASC has a dual-layer architecture comprised of a Pt/Al2O3 (PGM) bottom layer and a metal (Fe, Cu)-exchanged zeolite (M-Z) top layer. The PGM layer provides high NH3 oxidation activity; however, the desired N2 product is achieved over a narrow temperature range just above light-off, whereas the reaction byproducts N2O and NOx (i.e. NO and NO2) appear at intermediate and high temperatures, respectively. An advantage of the M-Z catalyst is the selective lean reduction of NO via conversion of NH3 to N2 over a broad temperature range. While recent studies demonstrate the effectiveness of the dual layer design, further advances are needed to reduce the PGM loading and ASC volume while enhancing low temperature activity. In this study, the dual-layer concept is scaled down to the level of a single core-shell catalyst particle, Pt/Al2O3@Cu/ZSM-5, compris...