Pd/Nb 2 O 5 /Al 2 O 3 catalysts were investigated on propane oxidation. Diffuse reflectance spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS) analysis suggested that monolayer coverage was attained between 10 and 20wt.% of Nb 2 O 5 . Temperature programmed reduction (TPR) evidenced the partial reduction of niobium oxide. The maximum propane conversion observed on the Pd/10% Nb 2 O 5 /Al 2 O 3 corresponded to the maximum Nb/Al surface ratio. The presence of NbO x polymeric structures near to the monolayer could favor the ideal Pd 0 /Pd 2 + surface ratio to the propane oxidation which could explain the promoting effect of niobium oxide.