Characterization and catalytic behavior of VO_x-CeO₂ catalysts for the oxidative dehydrogenation of propane

A series of vanadium-loaded ceria catalysts was prepared and their activity and selectivity towards propane oxidative dehydrogenation (ODH) was studied. The V-loaded samples all showed similar behavior, with high selectivity at low conversion (< 5%) dropping off exponentially with increasing conversion (and the inherent higher temperatures). The 6VCe sample showed the highest selectivity to proylpene at ∼ 33% and selectivity decreased with increasing V content. The ceria support itself showed virtually no selectivity towards propylene (maximum ∼ 2%) instead converting propane directly to CO₂ almost exclusively. For any given temperature, the 6VCe sample showed the highest yield, and the unpromoted support the lowest. In the 6 wt % V₂O₅ catalyst, hydrated surface VO_x species were present although they underwent conversion to CeVo₄ at above 573 K. The low reducibility of these surface vanadates was linked to the oxidation activity. Surface polyvanadates species were responsible for the selective ODH of propane with V-O-V and V-O-Ce being the active oxygen species.