Synthesis and FT–IR study of the acido–basic properties of the V2O5 catalysts supported on zirconia

In this paper we describe the synthesis and characterization of the acido–basic properties of catalysts containing varied amounts of vanadium supported on ZrO2. The preparation of the zirconia was carried out using a hydrolysis method and the vanadium was introduced by impregnation with a porous volume in several stages, followed by calcinations under air at a temperature of 723 K. The obtained samples are characterized by adsorption–desorption of nitrogen and infrared spectral analysis of different species formed by acidic and basic probes. This adsorption on the surface of these compounds has been studied in order, in the hand to investigate information on their surface acidity and in the other hand to know particularly the nature and strength of acidic and basic sites. Among the molecular probes, we used carbon monoxide, carbon dioxide, pyridine and 2,6-dimethylpyridine. The adsorption of CO has shown that contrary to pure zirconia and oxidized V2O5/ ZrO2, the reduced V2O5/ ZrO2 samples favour the formation of CO co-ordinated on Lewis acidic sites of reduced V2O5 species (CO on V4+ or V3+). We also observe the creation of Brønsted acidic sites by means of the incorporation of vanadium.