Oxidative dehydrogenation of propane on CeNixOy (0≤x≤1) mixed oxides hydrogen acceptors

The oxidative dehydrogenation of propane has been studied on CeNiXOY (0 less than or equal to x less than or equal to 1) mixed oxides previously reduced under hydrogen. The products obtained are propene and CO2. No CO is obtained, whatever the temperature. An optimum propene yield of 6.9 % is obtained at 648 K on previously, at 473 K under H-2, in-situ reduced CeNi0.5. Whereas without any pretreatment, a propene yield of 5.35 % is obtained. Therefore, a beneficial effect of the pretreatment under H-2 is shown. The reducibility under H-2 of some CeNiXOY mixed oxides has been previously studied and, in particular, it has been reported that these solids are able to store high quantities of hydrogen H* related to the existence of anionic vacancies. These H* species have been proposed to be one half H- species located in the anionic vacancies and the second half H+ species, forming with the O2- species of the solid, OH- groups. As dehydrogenation requires the abstraction of hydrogen from the molecule which could be performed by a lacunar phase, and by analogy to the dissociation of H-2, a mechanism of the dehydrogenation step of the alkane is proposed, involving a heterolytic abstraction of a H- species by an anionic vacancy and of a H+ species by an O2- species of the solid forming an OH group.