Propane oxidative dehydrogenation using CO2 over CrOx/Fe-CeO2 catalysts

The kinetic behavior of CrOx sites supported on Fe doped CeO2 was studied for CO2-assisted propane oxidative dehydrogenation. The support was synthesized via a co-precipitation method of Fe and Ce precursors while wetness impregnation was used to deposit the CrOx species. XRD and Raman analysis confirmed the presence of dispersed CrOx sites on the surface of the support at a low loading while small Cr2O3 nanoparticles were found at high loadings. The addition of CrOx sites reconstructs the available surface oxygen sites and enhances the reducibility of the catalyst as confirmed by H-2-TPR measurements. Herein, we show that the CrOx based catalysts outperform the parent support at low reaction temperatures both from a propane conversion and propylene selectivity perspective. At elevated temperatures, the effect of CrOx sites on the propylene production diminishes since propane dry reforming is dominant. A Langmuir-Hinshelwood kinetic model was developed based on 14 elementary steps to account for the dominating reaction pathways, i.e. propane dehydrogenation, reverse water gas shift and dry reforming. The regressed kinetic data showed that the incorporation of CrOx on the support decreases the activation energy of propane dehydrogenation by 60-75% while a small decrease in the activation energy of dry reforming was noted (similar to 15%).