Enhanced hydrothermal stability of a manganese metavanadate catalyst based on WO3–TiO2 for the selective catalytic reduction of NOx with NH3

A catalyst with 1 wt% manganese metavanadate (MnV2O6) based on WO3–TiO2 is prepared and applied to the selective catalytic reduction of NOx with NH3. After hydrothermal aging treatment at 750 °C for 12 h, it performs excellent activity with a wide temperature window. The catalysts are characterized by XRD, BET, DSC, UV–Vis, NH3-TPD and in situ FT-IR. With the introduction of MnV2O6, the sintering and phase transformation of TiO2 from anatase to rutile are suppressed during the aging process. Simultaneously, the excessive agglomeration of vanadium species and growth of crystalline V2O5 are hindered. The superior hydrothermal stability is attributed to the higher melting point of MnV2O6. The strong interaction between V and Mn contributes to maintain the vanadium species and inhibits the promoting effect of free vanadia on sintering and rutilization of support. MnV2O6 based catalyst exhibits higher adsorption capacity and activation ability of ammonia species after aging, which are in favor of the de-NOx activity.