Promotive effect of Nb2O5 on the catalytic activity of Ir/SiO2 for NO reduction with CO under oxygen-rich conditions

The addition of Nb2O5 was found to promote considerably the catalytic activity of Ir/SiO2 for the selective reduction of NO with CO under excess O2- and SO2-free conditions. Improvement of durability against oxidation of Ir metal by Nb2O5 addition is the main reason for the activity enhancement. Adding Nb2O5 to Ir/SiO2 (Nb2O5/Ir/SiO2) was more effective than using Nb2O5/SiO2 support for Ir (Ir/Nb2O5/SiO2). The excellent activity of Nb2O5/Ir/SiO2 can be attributed to the strong interaction of Ir with Nb2O5 as well as high Ir dispersion.