Activity and DRIFT spectroscopy studies of NO oxidation, and reduction by C3Hg6 in excess O2 over A12O3 and Au/A12O3

The activity and in situ DRIFT spectroscopy studies of NO and NO 2 SCR were performed on γ −Al 2 O 3 and Au/γ −Al 2 O 3 . The oxidation of NO to NO 2 over Au/Al 2 O 3 increased with temperature passing over a maximum of 25% at ≈450 °C before declining to near equilibrium conversions of ≈20% at ca. 500 °C. The conversion of NO x over Au/Al 2 O 3 increased with temperature, reached a maximum of ≈40% at 450 °C. When NO 2 was used as a source of NO x , the NO x conversion reached up to 53% at 400 °C. The activity and DRIFT results indicate that the initiation of NO SCR on Au/γ −A1 2 O 3 involves the oxidation of NO to NO 2 followed by coupling of the NO 2 or its adspecies, NO - x , with activated C 3 H 6 on active sites on Al 2 O 3 to form C n H m N x Oy species, which are responsible for the propagation step. Its subsequent internal rearrangement and decomposition leads to the formation of N 2 and other products. Taken together, the obtained results suggest that the NO 2 intermediacy benefits the NO SCR over gold catalysts as a reaction initiator or oxygen transfer agent.