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

摘要

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 FTlRspectroscopy 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 (Ag_n~(8+)) contain adsorbed oxygen in quantities sufficient only for the partial oxidation of alcohols toward oxygenated compounds, which then reduce NO.