Application of Temperature-Programmed Diffuse Reflectance Infrared Fourier Transform Spectroscopy to the Study of the Thermal Evolution of the Species Present in a Reacted Selective Catalytic Reduction V 2 O 5 /TiO 2 Catalyst

Temperature-programmed diffuse reflectance infrared Fourier transform spectroscopy (TPDRIFTS) has been used to characterize a reacted selective catalytic reduction (SCR) vanadia/titania catalyst. At room temperature the reacted catalyst presents ammonium ions adsorbed on the surface. On heating under N₂ flow, a surface redox reaction takes place; ammonium ions are oxidized to bridged nitrosyls species, while V⁵⁺ = O groups are reduced to V³⁺. Reduction of V⁵⁺ species to V³⁺ ions occurs at lower temperatures than those observed in conventional TPR processes under H₂ atmospheres. At higher temperatures, bridged nitrosyls species become monodentate, first in an angular configuration and then in a linear one. Previous data on the SCR reaction let us propose that they are desorbed from the surface as gaseous N₂O.