Catalytic oxidative dehydrogenation of propane over Mg-V-Mo oxides

A series of single-phase compositions found in the MgO - V ₂O ₅ - MoO ₃ ternary phase diagram, e.g., Mg ₃(VO ₄) ₂, Mg ₂V ₂O ₇, MgMoO ₄, etc., were studied for their activity and selectivity for the oxidative dehydrogenation (ODH) of propane. Molybdenum substitution on vanadium sites increased both the selectivity and activity of propane ODH. The increase in selectivity and activity seen with molybdenum substitution was associated with Mg cation vacancies formed from the substitution of Mo ⁶⁺ for V ⁵⁺. The cation vacancies allowed for a more facile diffusion of the bulk oxide anions to the catalyst surface. The relationship between structure and the catalytic activity and selectivity of Mg ₃(VO ₄) ₂ and Mg _0.992MoO _3.992 was studied by in situ visible and UV Raman spectroscopy. The present work was directed toward understanding the reaction mechanism of propane ODH on the catalyst surface. This is an abstract of a paper presented at the 228th ACS National Meeting (Philadelphia, PA, 8/22-26/2004).