Catalytic performance and stability of Fe-doped CeO2 in propane oxidative dehydrogenation using carbon dioxide as an oxidant†
Propane oxidative dehydrogenation (ODH) in the presence of CO2 was investigated over a series of Fe-doped CeO2 catalysts. The well-recognized properties of cerium oxide materials regarding improved oxygen mobility and oxygen storage capacity (OSC) were utilized towards the synthesis of stable catalytic systems. The iron–cerium oxide solid solution catalysts with an Fe dopant content from 1% up to 15% were successfully synthesized via a co-precipitation method and calcined at 873 K. It was confirmed by XRD and Raman characterization that all samples featured a single cerianite crystalline phase with periodic lattice Ce ions substituted by Fe ions, with no hematite phase identified. Initial screening of catalytic behavior showed that the propane ODH pathway was enhanced at high Fe/Ce ratio while propane cracking was suppressed. Stable propane conversion and propylene selectivity for up to 20 hours were achieved for the synthesized catalysts with moderate Fe loading. Ex situ Raman, XPS and STEM were applied to analyze post-reaction catalysts and confirmed that deactivation occurring over low Fe catalysts resulted from coke deposition on the surface, while CeO2 sintering and Fe migration to form nanocrystals were the primary deactivation reasons for high Fe loading catalysts.