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

Abstract

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 (O2−/O22−) could produce an “oxygen inhibitory effect”. The sample obtained using Mn(NO3)2·4H2O as a precursor, having the least OH groups, exhibited the best catalytic activity (T90 = 83 °C) and excellent SO2 resistance (T90 = 129 °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.