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

Use of zirconia, ceria–zirconia and ceria supports for Ag-based lean deNOx catalysts lowers the temperature range of activity by about 150–200K 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 tothe feed. The presence of ceria in the formulation results in an initial resistance to the deactivating effectof SO2; while the use of both zirconia and ceria–zirconia facilitates reactivation after sulphur poisoning.