The way to enhance the thermal stability of V2O5-based catalysts for NH3-SCR

A series of V2O5/WO3-TiO2 and V2O5/SiO2-WO3-TiO2 catalysts containing 2 wt%, 3.5 wt% and 5 wt% V2O5, respectively, were prepared by impregnation method. The NH3-SCR activity and thermal stability of the catalysts were investigated. It is noted that both V2O5 loading and SiO2 modification could affect the thermal stability of the V2O5/WO3-TiO2 catalysts. Increasing V2O5 loading improved the low temperature SCR activity of the catalysts in fresh state, but high V2O5 loading aggravated the deactivation of the catalysts upon aging. With relatively high V2O5 loading (3.5 wt% and 5 wt% V2O5), V2O5/SiO2-WO3-TiO2 showed remarkably improved thermal stability than V2O5/WO3-TiO2 NH3-SCR catalysts. The catalysts were characterized by BET, XRD, SEM, Raman, XPS, H2-TPR and NH3-TPD. The results indicated that high V2O5 loading on V2O5/WO3-TiO2 catalyst can accelerate the phase transition of anatase TiO2 to rutile TiO2 upon thermal aging, which resulted in the loss of surface area and consequently led to the deactivation, while introduction of silica prevented the phase transition of TiO2, therefore enhancing the thermal stability of the catalysts.