Mechanistic Study of Selective Catalytic Reduction of NOx with C2H5OH and CH3OCH3 over Ag/Al2O3 by in Situ DRIFTS

Although C2H5OH and CH3OCH3 are isomeric compounds, C2H5OH is much more efficient for NOx reduction than CH3OCH3. In situ diffuse reflectance infrared Fourier transform spectroscopy was used to study the reaction mechanism. The enolic species derived from the partial oxidation of C2H5OH over Ag/Al2O3 plays a crucial role in the formation of -NCO species 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 C2H5OH was used as the reductant. In the case of CH3OCH3, the formate species as the main intermediate has low activity for the formation of -NCO species, which results in the relatively low efficiency during the SCR of NOx.