Investigation of the ammonia adsorption on monolithic SCR catalysts by transient response analysis

The adsorption of ammonia on three different monolithic SCR catalysts was i nvestigated experimentally. Two Of the examined monoliths were coated cordi erite honeycombs, containing either V2O5-WO3/TiO2 or V2O5/TiO2 as active co mponents. The third sample was a commercially available extruded monolithic honeycomb consisting of V2O5-WO3/TiO2, and was tested for comparison. Diff erent transient response methods and a modified temperature programmed deso rption (TPD) method were used to investigate the ammonia adsorption in the presence of water (5%) and oxygen (10%). Under typical SCR conditions (stoi chiometric ratio NH3:NO<1), the ammonia coverage of the WO3-free catalyst s ample was significantly lower. Ammonia is more strongly adsorbed on the WO3 -containing catalyst. The extruded catalyst adsorbed substantially larger a mounts of ammonia especially at low temperatures, leading to a slow respons e under transient conditions. (C) 2000 Elsevier Science B.V. All rights res erved.