Role of the alumina surface properties on the ammonia production during the NOₓ SCR with ethanol over Ag/Al₂O₃ catalysts

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 2wt.% 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°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.