Potassium poisoning of titania supported deNOx catalysts: Preservation of vanadia and sacrifice of tungsten oxide

V2O5-WO3/TiO2 catalysts were prepared by a wet impregnation method, and the deactivation by KCl of their catalytic activity for selective catalytic reduction of NOx by NH3 (NH3-SCR) was investigated. The fresh and poisoned catalysts were characterized by inductively coupled plasma (ICP), N2 adsorption, Raman spectroscopy, H2 temperature-programmed reduction, IR spectroscopy of adsorbed NH3, and NH3 oxidation. Vanadia species, which are the active sites for the SCR reaction, were turned into inert potassium vanadate, but they were partially maintained on the catalyst at a high vanadia loading. Tungsten oxide acts as a sacrificial agent that reacts with potassium to form potassium tungstate in addition to its roles in increasing the surface acidity of the catalyst and facilitating the dispersion of vanadia. The V2O5-WO3/TiO2 catalyst at a high vanadia loading exhibited the best resistance to alkali poisoning.

Graphical AbstractDuring the deactivation of V2O5-WO3/TiO2 catalysts by KCl, the preservation of vanadia as active sites is critical to the catalytic activity for selective catalytic reduction of NOx by NH3 at the cost of increasing the vanadia loading and the sacrifice of tungsten oxide.Figure optionsDownload as PowerPoint slide