Superior resistance to alkali metal potassium of vanadium-based NH3-SCR catalyst promoted by the solid superacid SO42−-TiO2
The significant decrease of acid sites caused by alkali metal poisoning is the major factor in the deactivation of commercial V 2 O 5 -WO 3 /TiO 2 NH 3 -SCR catalysts. In this work, the solid superacid SO 4 2− -TiO 2 modified by sulfate radicals, was selected as the catalyst support, which showed superior potassium resistance. The physicochemical properties and K-poisoning resistance of the V 2 O 5 -WO 3 /SO 4 2− -TiO 2 (VWSTi) catalyst were carried out by XRD, BET, H 2 -TPR, NH 3 -TPD, XPS, in situ DRIFTS and TG. The results pointed out that the introduction of SO 4 2− significantly increased the NH 3 -SCR catalytic activity at high temperatures, with an exceptionally high NO x conversion over 90% between 275 °C and 500 °C. When 0.5% (mass) K 2 O was doped on the catalysts, the catalytic performance of the traditional V 2 O 5 -WO 3 /TiO 2 (VWTi) catalyst decreased significantly, while the VWSTi catalyst could still maintain a NO x conversion over 90% in the range of 300–500 °C. The characterizations suggested that the support of SO 4 2− -TiO 2 greatly increased the number of acidic sites, thereby enhancing the adsorption capacity of the reactant NH 3 . The results above demonstrated a potential approach to achieve superior potassium resistance for NH 3 -SCR catalysts using solid superacid.
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