Selective catalytic reduction of NO with ammonia over V2O5 doped TiO2 pillared clay catalysts

A series of vanadia doped TiO2-pillared clay (TiO2-PILC) catalysts with various amount of vanadia were studied for selective catalytic reduction (SCR) of NO by ammonia in the presence of excess oxygen. It was found that the V2O5/TiO2-PILC catalysts were highly active for the SCR reaction. The catalysts showed a broad temperature window, and the maximum NO conversion was higher than that on V2O5/TiO2 catalyst and was the same as the commercial V2O5 + WO3/TiO2 catalyst. The V2O5/TiO2-PILC catalysts also had higher N2/N2O product selectivities as compared to V2O5 doped TiO2 catalysts. In addition, H2O + SO2 slightly increased the activities at high temperatures (>350°C) for the V2O5/TiO2-PILC catalysts. Addition of WO3 to V2O5 further increased the activities of the PILC catalysts. These results indicate that TiO2-PILC is a good support for vanadia catalysts for the SCR reaction. In situ FT–IR experiment indicated that both Brønsted acid sites and Lewis acid sites exist on the catalyst surface, but with a large proportion being Brønsted acid sites at low temperatures (e.g., 100°C). The reaction path for NO reduction by NH3 on the V2O5/TiO2-PILC is similar to that on V2O5/TiO2 catalyst, i.e., N2 originates from the reaction between gaseous NO and NH3 adspecies.