Alumina-supported mixed Mo-V oxide catalysts were prepared by impregnation at different atomic Mo/V ratios and with different total (Mo+V) coverage on alumina support, ranging from 0.2 to 5 times their dispersion limit (monolayers coverage). The characteristics of the calcination, total Mo+V loading, and Mo/V atomic ratio was studied during propane oxidative conventional dehydrogenation (ODH and DH) reaction. The nature of surface sites was evaluated by methanol TPR profiles with online MS. The nature of the Mo, V, and mixed Mo-V oxide phases during reaction was evaluated by Raman spectroscopy during propane ODH and DH reactions with simultaneous activity measurement (operando Raman methodology). This is an abstract of a paper presented at the 228th ACS National Meeting (Philadelphia, PA 8/22-26/2004).