Enhancement of SCR activity and mechanical stability on cordierite supported V 2 O 5 -WO 3 /TiO 2 catalyst by substrate acid pretreatment and addition of silica

To evaluate the feasibility of the catalysts loaded onto the commercial cordierite monolith by a one-step loading method, the catalyst of V2O5-WO3/TiO2 was loaded onto cordierite with the aid of acid pretreatment and silica sol addition. The results by SEM and N2 adsorption showed that acid pretreatment of cordierite enlarged the BET surface area and pore volume of the catalysts significantly, enhancing both the SCR activity and mechanical stability. During the catalysts preparation, the introduction of silica sol demonstrated a significant improvement in the BET surface area and mechanical stability of the catalysts. The surface acidity of the catalysts increased with the increasing molar ratios of Si/Ti and decreased again, with the strongest surface acidity at Si/Ti molar ratio of 5/5. The XPS analysis showed that the incorporation of Si shifted the V valence from V5 + to V4 + and increased chemisorbed oxygen, which accelerated the SCR activity. The catalyst with cordierite acid pretreatment and Si/Ti molar ratio of 2/8 demonstrated to be an optimal catalyst, which showed a high NO conversion above 90% at 573–773 K, high mechanical stability, and resistance to sulfur and hydrothermal aging.