Promotional Effect of Ni on a CrOx Catalyst Supported on Silica in the Oxidative Dehydrogenation of Propane with CO2

As CrOx catalysts supported on the SBA-15 support (Cr/Si) are highly active, they represent potentially promising catalysts for the oxidative dehydrogenation of propane with CO2 (ODHP). However, reduction of the active sites (Cr3+) during the reaction is known to lead to severe deactivation. The findings reported herein indicate that after the addition of 0.5 wt?% Ni to 10 wt?% Cr/Si (0.5 Ni-Cr/Si), the catalytic activity was stable and the selectivity was high. Reduced CrOx was easily regenerated by the addition of Ni, as evidenced by a three-step H2-temperature programmed reduction analysis. In addition, ex situ XPS results revealed that Cr3+ was maintained only in the Ni-promoted catalyst whereas Cr3+ was easily reduced to Cr2+ in the non-promoted catalyst during the reaction. The role of the Ni added to the catalyst elucidates that Ni induces the dissociation of CO2 to CO and activated O (O*ads). Then, the generated O*ads regenerates the reduced CrOx. Consequently, the Ni-promoted Cr/Si catalyst enhances the catalytic stability of propylene in the ODHP reaction.