Fogel, S.2; Doronkin, D. E.1; Høj, J. W.4; Gabrielsson, P.4; Dahl, S.1
1 Department of Physics, Technical University of Denmark2 Experimental Surface and Nanomaterials Physics, Department of Physics, Technical University of Denmark3 Haldor Topsoe AS4 Haldor Topsoe AS
Low-temperature active Ag/Al2O3 and high-temperature active Fe-BEA zeolite were combined and tested for H2-assisted NH3-selective catalytic reduction (SCR) of NO x . The catalysts were either washcoated onto separate monoliths that were placed up- or downstream of each other (dual-brick layout) or washcoated on top of each other in a sandwiched layout (dual-layer). Our results showed that it is highly preferred to have Ag/Al2O3 as the upstream or outer layer catalyst. Fe-BEA showed a high NH3 oxidation giving an NH3 deficit over the Ag/Al2O3. Ag/Al2O3 formed NO2 which enhanced the activity over Fe-BEA through the “fast”-SCR reaction when Fe-BEA was placed downstream or as inner layer. When no H2, which is needed for the SCR reaction over Ag/Al2O3, was added, the dual-layer layout was preferred. The shorter diffusion distance between the layers is a probable explanation.
Topics in Catalysis, 2013, Vol 56, Issue 1-8, p. 14-18