NbOx/CeO2-rods catalysts for oxidative dehydrogenation of propane: Nb–CeO2 interaction and reaction mechanism

Abstract A series of NbO x /CeO 2 -rod catalysts were synthesized and employed as catalysts for oxidative dehydrogenation of propane (ODHP) reaction. Nb–CeO 2 interaction and reaction mechanisms were studied with synchrotron-radiation-based techniques. Synchrotron radiation photoemission spectroscopy and resonant photoemission spectroscopy results demonstrate that the Nb 5+ precursor preferentially interact with surface oxygen vacancies on CeO 2 rods. Surface redox reactions occur between Nb 5+ and Ce 3+ (surface oxygen vacancy) to produce Nb 4+ and Ce 4+ , resulting in decreased surface oxygen vacancy concentrations on CeO 2 rods. CeO 2 rods are active in catalyzing propane combustion at low temperatures (below 400 °C) via the MvK mechanism. The loading of NbO x suppresses the surface reducibility of CeO 2 rods, leading to decreased activity but greatly enhanced propene selectivity. The ODHP reaction catalyzed by CeO 2 rods and NbO x /CeO 2 -rods catalysts at high temperatures (above 450 °C) involves the radical mechanism, in which the gas-phase propyl radical was observed with synchrotron radiation VUV photoionization time-of-flight mass spectroscopy. These results greatly deepen the fundamental understanding of CeO 2 -based catalysts for ODHP reaction.