Effect of the support on activity of silver catalysts for the selective reduction of NO by propene

Use of zirconia, ceria-zirconia and CeO2-containing supports for Ag-based lean deNOx catalysts lowers the temperature range of activity by about 150-200 K with respect to Al2O3-supported analogues. Ex-situ characterisation of the catalysts indicates that this remarkable effect is associated with a role of the support rather than Ag dispersion. The crucial role of the support is further evidenced by suppression of CO formation over these catalysts and by significant support-related differences when SO2 is added to the feed. The presence of ceria in the formulation results in an initial resistance to the deactivating effect of SO2; while the use of both zirconia and ceria-zirconia facilitates reactivation after sulphur poisoning.