Effect of active component addition and support modification on catalytic activity of Ag/Al2O3 for the selective catalytic reduction of NOx by hydrocarbon - A review

The effect of active component addition and support modification of Ag/Al2O3 has been reviewed to examine their contribution to HC-SCR of NOx. This review has depicted the possible mechanisms of reduction of NO by hydrocarbon using metal/metal oxide doped Ag/Al2O3. The addition of second metal results in the maximum formation of well dispersed Agnδ+ clusters. Specifically, addition of Au improves the low-temperature activity of the catalyst. However, the role of second metal also depends on the pretreatment to the catalyst and nature of the reductants. The support modification of Ag/Al2O3 by the addition of different metal oxides has also been reviewed. Modification by MgO showed improvement in activity besides sulfur tolerance. In situ DRIFT study demonstrates that the modification by MgO leads to the inhibition of sulfate formation of Ag and Al2O3. Enhancement in activity after second metal addition and support modification attributed to the synergistic effect and improved surface properties of Ag/Al2O3 catalyst.