The Selective Catalytic Reduction of NOx with ethanol (EtOH-SCR) was studied over Ag/Al2O3 catalysts. A special attention was given to the ammonia emission and its possible relationship with the support acidic properties. For this purpose, five aluminas were selected, three provided by manufacturers and two synthesized in our laboratory by sol-gel or precipitation route. The supports were impregnated with 2 wt.% Ag, and tested in EtOH-SCR. The results showed that the catalytic activity of Ag/Al2O3 greatly depends on the used alumina. An unexpected ammonia production is evidenced, varying between 6 and 27% at 450 degrees C, while NOx are fully converted. A correlation was established between the NH3 yield and the Lewis acid sites (LAS) density measured by pyridine adsorption for each catalyst. (C) 2010 Elsevier B. V. All rights reserved.