STUDY OF THE MORPHOLOGY OF VANADIA-TITANIA AND TIN-OXIDE-PROMOTED VANADIA-TITANIA CATALYSTS BY ELECTRON-MICROSCOPIC METHODS

An 8 wt% vanadia/titania catalyst, prepared by impregnation, was promo ted with tin(IV)-oxide, resulting in a catalyst with a Sn:V:Ti atomic ratio of 1:20:262. The catalyst morphology was characterised by high r esolution transmission electron microscopy, scanning transmission elec tron microscopy combined with energy dispersive X-ray analysis, and el ectron spectroscopic imaging/electron energy loss spectroscopy. The va nadia distribution was found to be inhomogeneous. A fraction of the ti tania was partly covered by vanadia, though there was a considerable a mount of separate vanadia and titania crystallites as well. The presen ce of an amorphous layer on titania and its restructuring during elect ron beam irradiation is disputed as evidence for a vanadia monolayer. Tin-oxide promotion did not influence significantly the vanadia distri bution; the low content of the promoter prevented the mapping of its d istribution.