The selective catalytic reduction (SCR) of NO with C 3H 6 over Ag/Al 2O 3 in excess oxygen was studied. The Ag particles could evenly be dispersed on the surface of Al 2O 3 with an optimal Ag loading of 4%~6% and an average size of 15 nm. The NO conversion over 4%Ag/Al 2O 3 catalyst was above 90% under the conditions of GHSV= 50?000 h -1 and θ =430~550 ℃. Organic nitro compounds (R ONO, R NO 2) and nitrogen dioxide formed during the SCR reaction resulted in the difference between NO...