The effect of the calcination temperature of Ag/Al2O3 catalyst on NO removal activity by n-dodecane as a diesel simulant has been examined with respect to the Ag loading and C-1/NO feed ratio under a feed gas condition containing both excess H2O and oxygen. The higher the catalyst calcination temperature and Ag loading, the higher deNOx activity that has been achieved in the reaction temperature range lower than 300 degrees C. 56% of the NO conversion to N-2 has been attained over Ag(2)-800 catalyst at 300 degrees C when the C-1/NO feed ratio to the reactor is 6. The amount of the metallic Ag formed on the catalyst surface responsible for the high deNOx performance in the temperature region lower than 300 degrees C increases upon the increase of the catalyst calcination temperature from 550 to 800 degrees C and of the Ag loading from 1 to 3 wt.%, as determined by UV-vis and XPS. The -NCO species formed on the catalyst surface with acetate, formate and carbonate compounds produced from the partial oxidation of n-dodecane is a critical reaction intermediate for the present reaction system, as identified by in situ IR study. The formation of the -NCO species on the catalyst surface becomes apparent, particularly at 300 degrees C as the catalyst calcination temperature increases. (c) 2010 Elsevier B.V. All rights reserved.