Journal of Molecular Catalysis, 81 (1993) L25-L30 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPON Elsevier Science Publishers B.V., Amsterdam L25 Ml51 Spectroscopic study of the nature of vanadium-oxo species adsorbed on anatase Margarita Kantcheva*Ta, Anatoly Davydovb and Konstantin Hadjiivanov” aInstitute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Sofia 1040 (Bulgaria); tel. (+359-2)7133598, fax. (+359-2)705024) bInstitute of Catalysis, Novosibirsk 630090 (Russian Federation) (Received December 26,1992; accepted February 21,1993) zyxwvutsrqponmlkjihgfedcbaZYXWVU Abstract Key words: VO, absorbed on anatase; diffuse-reflectance UV-Vis spectroscopy; infrared spectros- copy; localization Earlier [ zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA 1 ] we studied the VO, compounds formed after adsorption on to anatase of vanadium-oxo species from aqueous solutions. We have proposed the existence of two types of surface structures, depending on their localiza- tion: (i) hydroxyvanadyl species (containing OH group) located in the vicinity of coordinatively unsaturated (cus ) Ti4+ -ions and (ii) monomeric vanadyl species (without OH group), which have replaced the hydroxyl group of the support. Here the structure and localization of the surface vanadium oxo-spe- ties on anatase are considered more in detail. A detailed description of sample preparation has appeared [ 11. Two types of supports were used: (i) pure hydrated titania (anatase) obtained by hy- drolysis of TiC14at pH 9 and calcined in air at 400’ C for 2 h, and (ii ) a modified adsorbent prepared by treating hydrated anatase with a 5% H,O, solution fol- lowed by drying in air at 25 ’ C. Adsorption was carried out using an ammonium vanadate solution in nitric acid at pH 0.5. After 2 h the precipitate was filtered, washed with water, dried and calcined in air at 400’ C for 1 h. Some character- istics of the investigated samples are given in Table 1. The IR spectra were recorded with a Specord M-80, and the diffuse-reflectance UV-Vis spectra with a Shimadzu UV-300 instrument. The spectra of the samples were recorded after thermal treatment at 450°C in situ first under a vacuum of better than 10F4 Torr and then in oxygen (100 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPON Torr ) at the same temperature (activated samples ) . The atomic absorption analysis of the catalysts was performed by a Pye Unicam SP 1950 instrument at the corresponding resonance wavelength. The *Corresponding author. 0304-5102/93/$06.00 0 1993 - Elsevier Science Publishers B.V. All rights reserved.