Deactivation Mechanism and Enhanced Durability of V2O5/TiO2–SiO2–MoO3 Catalysts for NH3−SCR in the Presence of SO2

Abstract

AbstractV2O5/TiO2‐type catalysts are widely applied for selective catalytic NO reduction by NH3 (NH3‐SCR), but enhanced sulfur tolerance and low‐temperature activity are required. Herein, V2O5/TiO2−SiO2−MoO3 (V/TSM) was demonstrated to have excellent catalytic activity and durability for NH3‐SCR in the presence of SO2 at temperatures lower than 200 °C. The deactivation mechanism and factors influencing SO2 durability were investigated using catalytic durability tests, Fourier‐transform infrared spectroscopy, and temperature‐programmed desorption/decomposition. Our results revealed that (NH4)2S2O3 and NH4HSO4 form on catalyst surfaces by NH3−SO2−H2O reactions at low temperatures, resulting in catalyst deactivation via pore blockage. However, V/TSM was found to possess an increased number of active sites for decomposing deposited ammonium sulfate salts. The decomposition activity was related to the solid acidity, which enhanced SO2 desorption and reactions between ammonium sulfate salts and NO. These findings will contribute to the development of catalysts with improved lifetimes for NH3−SCR.