?Effect of titanium-doping on the properties of vanadium antimonate catalysts

A. BARBARO; S. LARRONDO; S.DUHALDE; AMADEO, N.

APPLIED CATALYSIS A-GENERAL

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2000 vol. 193 p. 277 - 283

0926-860X

Catalysts of nominal compositions VSb1−xTixO4, with xD0, 0.1, 0.2 and 0.4, were prepared by solid state reaction ofvanadium(V) oxide, antimony(III) oxide and titanium(IV) oxide mixtures. Their structural and catalytic properties werestudied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature programmed reduction (TPR) andcatalytic heterogeneous oxidation of toluene to benzaldehyde.The samples with 10% (xD0.1) and 20% (xD0.2) of titanium present the highest activity and selectivity to benzaldehydeunder the operating conditions used in this work. When the titanium content is 40% (xD0.4), the activity level drops stronglybelow the level found for the undoped vanadium antimonate. X-ray patterns show the presence of vanadium(V) oxide as aseparate phase in this sample, and this is probably the cause of the low catalytic performance.TPR results show that the replacement of antimony by titanium changes the oxidation-reduction properties of the vanadiumantimonate phase.In the samples with titanium content up to 20%, there seems to be a direct relationship between the selectivity and theseparation of the reduction temperatures of both reduction peaks of the TPR profile: the larger the separation, the higher isthe selectivity to benzaldehyde.All the samples with xD0, 0.1 and 0.2 show surface antimony excess despite being prepared from stoichiometric mixturesof nominal V/Sb ratios larger than or equal to 1. ©2000 Elsevier Science B.V. All rights reserved.