Selective catalytic reduction (SCR) of NO and NO2 with ammonia was investigated over activated carbon-supported vanadium oxide (V2O5/AC) catalyst. The results show that high activity and selectivity could be achieved in wide range of temperatures and space velocities. NOx conversion to N-2 increases with increasing NO2/NOx ratio, and the increase vanishes gradually with increasing temperature. An increase of NOx conversion to N-2 from 26% to 94% can be achieved at a temperature as low as 150 degrees C without the formation of NH4NO3. The results of temperature programmed desorption (TPD) and infrared (IR) spectrometry experiments show that NH4NO3 could be deposited on the catalyst at 100 degrees C and decomposed to NH3, N2O, and NO around 130 degrees C. To explain the observed behaviors, AC involved NO2-SCR process was proposed, in which NH4NO3 is reduced to N-2 by AC instead of NO. This process shows better reactivity at lower temperatures. (C) 2011 Elsevier B.V. All rights reserved.