Combination of Ag/Al2O3 and Fe-BEA for High-Activity Catalyst System for H2-Assisted NH3-SCR of NO x for Light-Duty Diesel Car Applications |
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Authors: | S. Fogel D. E. Doronkin J. W. Høj P. Gabrielsson S. Dahl |
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Affiliation: | 1. Haldor Tops?e A/S, Nym?llevej 55, 2800, Kgs. Lyngby, Denmark 2. CINF, Technical University of Denmark, Fysikvej 307, 2800, Kgs. Lyngby, Denmark
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Abstract: | 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. |
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