Interaction of V2O5 with TiO2 during prepn. of V/Ti-oxide catalysts via solid-state reaction was studied using in situ FT-Raman spectroscopy, HRTEM and XPS. This interaction results in the formation of monomeric vanadia species with vanadium in tetrahedral coordination. The bridging O in the V-O-Ti bond is responsible for the catalytic activity during the partial oxidn. of toluene. The formation of the monomeric vanadia species correlates with the improved catalyst performance, characterized by reaction rate and selectivity to benzaldehyde and benzoic acid. Mech. activation by intensive grinding of V2O5/TiO2 mixt. via ball milling was necessary for the interaction of the oxides during calcination. The monomeric species formation was obsd. at temps. as low as 523 K. The dynamics of V2O5/TiO2 interaction strongly depends on the presence of moisture during the calcination. (c) 2000 Academic Press. [on SciFinder (R)]