Influence of surface active groups on SO2 resistance of birnessite for low-temperature NH3-SCR

Understanding the SO2 poisoning mechanism of catalysts and improving their SO2 resistance are the key to the technology of selective catalytic reduction of NO with NH3 (NH3-SCR). Birnessite catalysts were synthesized and used to investigate the SO2 poisoning effects in low-temperature NH3-SCR. Physicochemical characterizations indicated that surface active groups play a vital role in the poisoning process. Hydroxyl groups (OH) could react with SO2 to form HSO3-, and further react with NH3 to form NH4HSO3. The accumulation of excessive surface active oxygen groups (O-2(-)/O-2(2-)) could produce an oxygen inhibitory effect. The sample obtained using Mn (NO3)(2)center dot 4H(2)O as a precursor, having the least OH groups, exhibited the best catalytic activity (T-90 = 83 degrees C) and excellent SO2 resistance (T-90 = 129 degrees C). This work demonstrated the significant effect of surface active groups on SO2 resistance over birnessite, providing a new perspective for other catalysts to improve SO2 resistance.