FT-IR spectroscopic investigation of the effect of SO2 on the SCR of NOx with propene over ZrO2–Nb2O5 catalyst

The SO2 tolerance of a catalyst based on ZrO2–Nb2O5 solid solution (mole ratio ZrO2:Nb2O5 = 1:6) in the catalytic activity for NOx reduction with propene in excess oxygen has been studied. No loss in the C3H6-SCR activity was observed for 2 h after the addition of 56 ppm of SO2 to the reaction mixture. When the concentration of SO2 has been increased to 200 ppm (the so-called fast poisoning experiment) the activity of the catalyst decreased by 13% and remained unchanged for more than 5 h under these conditions. The effect of SO2 on the surface reaction of the SCR reactants has been investigated by in situ FT-IR spectroscopy and mechanism for the suppression of the catalytic activity at high concentration of the poison has been proposed.