Catalytic reactions of n-pentane and 1-pentene were performed as a function of reaction temperature, on different molybdenum oxides and metal surfaces. These oxides such as Mo2O5 and MoO2 were obtained following the exposure of MoO3/TiO2 to hydrogen at different temperatures up to 673 K. Metallic Mo(O) state is obtained at reduction temperatures beyond 723 K. Identification of the Mo chemical species was performed using in situ XPS-UPS surface techniques. The combination of both techniques provides valuable information on the chemical composition of the upper 10 atomic monolayers. X-ray diffraction and HRTEM techniques were also employed. The reduction procedure Of MoO3 does not follow the same pathway when it is deposited on an Al2O3 support. A strong electronic interaction between the two species promotes the formation of an Al-2(MoO4)(3) complex as revealed by XRD measurements. Catalytic active functions present on the different Mo species surfaces are of the acidic type (Lewis and Bronsted) on Mo2O5, metal-acid (bifunctional) on MoO2 and metal function on metallic Mo(O). Consequently, a specific catalytic reaction of n-pentane, such as hydroisomerization to iso-pentane, which is rationalized in terms of a bifunctional mechanism, is expected to occur on MoO2. Different isomerization reactions of 1-pentene were obtained in the case Of MoO3/TiO2 and MoO3/Al2O3 at reduction temperatures below 573 K. However, in the case of Mo on the alumina support, the conversion of I-pentene to iso-pentane is low and irreproducible, contrary to what has been observed for Mo on titania. (c) 2008 Elsevier B.V. All rights reserved.