Ethanol-selective catalytic reduction of NO by Ag/Al2O3 catalysts: Activity and deactivation by alkali salts

Ag/Al2O3 catalysts with and without potassium doping were prepared by incipient wetness impregnation and characterized by N2 physisorption, XRPD, NH3-TPD and SEM. The influence of the Ag content from 1 to 5 wt.% was investigated for the selective catalytic reduction (SCR) of NO with ethanol. The 3 wt.% Ag/Al2O3 catalyst was found to be the most active and CO2 selective over a wide temperature window (300–500 ◦C).

Addition of 500 ppm of H2 has a mild promotional effect on the activity while SO2 has a strong negative influence on the SCR activity. Furthermore, the Ag/Al2O3 ethanol-SCR catalyst deactivated significantly by the addition of potassium although it was more resistant than the conventional V2O5 based NH3-SCR catalyst, which deactivated more at lower potassium loading.

The higher potassium resistivity of the Ag/Al2O3 catalysts seems to be due to differences in reaction mechanism of Ag/Al2O3 ethanol-SCR catalyst compared to the conventional NH3-SCR catalyst. The still low potassium resistance, in combination with the high sensitivity to SO2, seems not to make these catalysts a real option for biomass fired boilers.