Remarkable activity of Ag/Al2O3/cordierite catalysts in SCR of NO with ethanol and butanol

Abstract

Structured silver–alumina catalysts were prepared by the one-step deposition of Al2O3 directly on the surface of cordierite block matrices with subsequent incipient wetness impregnation of Al2O3/cordierite with an AgNO3 aqueous solution. The catalysts were characterized by BET, XRD, XPS and FTIR spectroscopy with CO and pyridine as molecule probe, diffuse reflectance UV–vis, TEM and SEM. The Ag/Al2O3/cordierite catalysts are highly active in SCR of NO with ethanol and butanol and very selective toward N2. The conversion of NO over 0.6%Ag/45%Al2O3/cordierite catalyst reaches the high values of 95–99% already at 250°C and remains at this high level up to 430°C. The optimal silver loading in the silver–alumina catalysts is differing for C2 and C4 alcohols. It is shown that the role of silver in the Ag/Al2O3/cordierite catalyst consists in the modification of both redox and acid–base properties of the catalyst surface. Isolated cations (Ag+) and/or silver nanoclusters (Agnδ+) contain adsorbed oxygen in quantities sufficient only for the partial oxidation of alcohols toward oxygenated compounds, which then reduce NO.