SURFACE ACID PROPERTY AND ITS RELATION TO SCR ACTIVITY OF PHOSPHORUS ADDED TO COMMERCIAL V2O5(WO3) TIO2 CATALYST/

To examine the influence of phosphorus on the commercial V2O5(WO3)/TiO 2 SCR catalyst, measurements were carried out by means of infrared and Raman spectroscopy, XPS, and NO reduction measurement as a function o f phosphorus loading. Phosphorus added to the catalyst was found to di sperse well over the catalyst without a significant agglomeration up t o 5 wt% P2O5 addition. The number of the hydroxyl groups bonded to the vanadium and titanium species decreased readily with increasing amoun t of phosphorus. Correspondingly the hydroxyl groups bonded to the pho sphorus species were formed. NH3 adsorbed on both hydroxyl groups bond ed to vanadium and phosphorus as ammonium ions, implying that the P-OH groups formed are also responsible for the Bronsted acidity. The NO r eduction activity was found to be decreased with increasing amount of phosphorus; however, the influence of phosphorus was relatively small irrespective of the large amount of phosphorus addition. The deactivat ion might be caused by the change in the nature of the surface hydroxy l groups as Bronsted acid sites. Phosphorus species might partially wr ap the surface V=O and W=O groups, which might also contribute to the deactivation.