The synthesis of vanadium oxide systems (with 5 and 20 wt% V2O5 loadings) supported on commercial γ-alumina was carried out by a wet impregnation method. The samples were characterized by low-temperature nitrogen adsorption (BET), inductively coupled plasma (ICP) method and by in situ electrical conductance/capacitance measurements. The adsorption of CO was used to investigate the acidic properties of alumina support and V2O5/-Al2O3 catalysts by FTIR spectroscopy. The catalytic activities of the samples were tested in propylene oxidation reaction, in the temperature range of 30-400°C. The electrical/dielectric properties of the support strongly influence the surface behavior of the supported phase.