In the present study, time-resolved in situ IR spectroscopy measurements were performed during selective catalytic reduction of NO with NH3 by supported V2O5-WO3/TiO2 catalysts to examine the reactivity of surface NH3,ads species on Lewis acid sites and surface NH4+,ads species on Brønsted acid sites. Both surface NH3,ads and NH4+,ads intermediates were found to participate in the SCR reaction. The relative population and reactivity of the two surface intermediates were found to be dependent on the coverage of the surface vanadia and tungsta sites on the titania support, temperature and moisture. Although the more abundant surface NH4+,ads intermediates dominate the overall SCR reaction, especially for hydrothermally aged catalysts, the minority surface NH3,ads intermediates exhibit a higher specific SCR activity (TOF). The surface tungsta sites are much less active than the surface vanadia sites for SCR and primarily function as promoters for surface vanadia sites. The exposed Ti sites of the support do not contribute to the reaction rate under the present reaction conditions. The current study serves to resolve the long standing controversy about the active sites for SCR of NO with NH3 by supported V2O5-WO3/TiO2 catalysts since surface NH4+,ads intermediates are the dominant adsorbed ammonia species during the SCR reaction, especially for activated catalysts.

Nature of active sites and surface intermediates during SCR of NO with NH3 by supported V2O5-WO3/TiO2 catalysts

255th National Meeting (2018)

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