Low-temperature reactivity of the surface species of vanadia-tungsta catalyst

This paper concerns species of WO3-V2O5 solid solution and of vanadia-tungs ta intermediate compound (IC) formed as a result of oxidation-induced vanad ium segregation on the surface of an unsupported V-W-O catalyst. The evolut ion of the surface species during their interaction with ammonia (64 Torr) and nitric oxide (64 Torr) at room temperature was investigated by FT-Raman spectroscopy. The transformation of WO3-V2O5 solid solution species into a mmonium methavanadate (V) ones and the reduction of intermediate compound s pecies, followed by inward vanadium diffusion into subsurface layers, were observed as a result of the catalyst interaction with ammonia. The next cat alyst interaction with NO was found to cause restoration of the WO3-V2O5 sp ecies but not of the intermediate compound ones at the surface. (C) 2001 El sevier Science B.V, All rights reserved.