Abstract: The selective catalytic reduction (SCR) of NO with propylene was investigated over Cu/Al₂O₃ catalyst by using fixed-bed reactor and in situ FTIR and compared with Ag/Al₂O₃ which has a relative high activity in C₃H₆-SCR of NO. The highest conversion of NO is only 40% at about 650 K, when the catalyst was exposed to a gas mixture of NO/C₃H₆/O₂/N₂=0.08%/0.171 4%/10%/balance with W/F=0.018 g·s/mL. Surface R—NO₂ and R—ONO species, which were observed on Ag/Al₂O₃ catalyst as the precursor of —NCO species, can hardly be found on Cu/Al₂O₃ catalyst surface in FTIR spectra under the same condition. This results in the low activity of Cu/Al₂O₃ catalyst for NO reduction. Through dynamic FTIR experiment, it was found that NO₃^- species, which are dominant surface species over Cu/Al₂O₃ catalyst, have a low activity with C₃H₆, so that the reaction producing R—NO₂ and R—ONO is very difficult to take place.

Key words: Cu/Al₂O₃, Ag/Al₂O₃, NO_x, Selective catalytic reduction (SCR), In situ FTIR