Abstract: Although C2H5OH and CH3OCH3 are isomeric compounds, C2H5OH is extremely efficient for NOx reduction while it is not the case for CH3OCH3. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was used to study the reaction mechanism. The enolic species derived from partial oxidation of C2H5OH over Ag/Al2O3 plays a crucial role in the -NCO species formation during the selective catalytic reduction (SCR) of NOx by C2H5OH. The high reactivity of the enolic species results in high surface concentration of -NCO species and high efficiency of NOx reduction when using C2H5OH as a reductant. In the case of CH3OCH3, the formate species as a main intermediate has lower activity for the formation of -NCO species, which results in the relatively low efficiency during the SCR of NOx.

Key words: silver, alumina, nitrogen oxide, selective catalytic reduction, ethanol, methyl ether, in situ diffuse reflectance infrared Fourier transform spectroscopy, enolic species, formate species, isocyanate species