EFFECTS OF THE ACTIVE PHASE SUPPORT INTERACTION IN VANADIUM-OXIDE ON TIO2 CATALYSTS FOR ORTHO-XYLENE OXIDATION

Catalytic performance in o-xylene oxidation of two samples of vanadium oxide on rutile or anatase TiO2 supports, prepared by mechanical mixing, is analyzed with reference to their characterization by XRD, FT-IR and chemical analyses. Results show that the active phase, characterized by a Vv:VIV ratio of 2:1 and an IR band at 995 cm-1, does not interact directly with the titania surface, but rather with a VIV-modified surface. It is suggested that these VIV surface sites act as the 'clinging' sites for stabilization of an upper active phase. The same active phase is found on both anatase- and rutile-based samples. Competing migration towards the bulk of these VIV sites on the rutile sample causes a slight decrease in catalyst performance. In particular enhanced formation of the intermediate product, phthalide, is observed. © 1990.