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 V2O5/TiO2 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 N-2 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 H-2 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.