A series of titania(anatase)-supported vanadia catalysts (20 wt% V2O5) was synthesized by various methods based on the use of TiO2-precursors, resulting to final materials with different anatase particle sizes and BET surface areas (69 � 220 m2/g) and vanadium surface densities in the 6 � 19 V/nm2 range.The speciation and the molecular structure of the deposited oxo-vanadium species was probed by in situ Raman spectroscopy under dehydrated (O2) and reducing (NH3/N2) atmospheres at 250o C. Figure 1 shows the in situ Raman spectra of the studies (VOx)n/TiO2 catalysts under dehydrated conditions (flowing O2) at 250o C. Vanadia is deposited in the form of oxo-V(V) species in various extents of association (polymerization). No evidence of crystalline V2O5 is found, even in the highest loaded sample with surface density of 19 V/nm2, although the monolayer coverage of vanadia in titania is ~7-8 V/nm2. Presumably, the formation of 3-D amorphous overlayers structured as alternating VO6, VO5 and/or VO4 units is favored, following the specific preparation method of the 19 V/nm2 sample. The spectral features of the 6 V/nm2 sample are indicative of the predominant occurrence of (O=VOx)n species in small size (e.g. n=2,3). The response of the catalyst structure to NH3/N2(SCR-like reducing) atmosphere shows an ease of reduction of deposited oxo-V(V) species in samples with high extent of association, a fact that is justified by the occurrence of V atoms in adjacent sites.

Molecular structure of titania-supported V2O5 DeNOx catalysts: An ?in situ? Raman spectroscopic study

247th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.