The Selective Catalytic Reduction by NH3/urea is a world-wide established after treatment technology for the removal of NOx in the stack gases of power plants and of other stationary sources. Typical SCR catalysts operate between 300 and 400 degrees C, however for some applications SCR systems with reasonable DeNO(x) activity at temperatures as low as 180 degrees C are required nowadays. It was recently shown that over both V2O5-WO3/TiO2 and Fe-ZSM-5 commercial SCR catalysts the addition of aqueous solutions of NH4NO3 to a NO-NH3 containing feed stream results in the occurrence of the "Enhanced SCR" (E-SCR) reaction (2NH(3) + 2NO + NH4NO3 > 3N(2) + 5H(2)O), characterized by superior NO reduction efficiencies in the 200-350 degrees C range. In this paper we present a systematic experimental study of the E-SCR reaction over a commercial V-based Haldor Topsoe catalyst. The effects of three operating variables, namely space velocity (18-75 k h(-1)), temperature (180-250 degrees C) and ammonium nitrate feed content (0-100% of stoichiometric feed), are addressed in order to identify the best process conditions in view of the specific application of this new technology to stationary SCR installations. (C) 2011 Elsevier B.V. All rights reserved.