Molecular-level investigation on supported CrOx catalyst for oxidative dehydrogenation of propane with carbon dioxide

Abstract

Although the supported CrOx is widely applied as an important industrial catalyst for oxidation processes (such as propane dehydrogenation), the molecular-level understanding of its catalytic mechanism is still limited. In this work, the oxidative dehydrogenation of propane with carbon dioxide (CO2-ODP) was exploited as a probe reaction to investigate CrOx highly dispersed over dealuminated β zeolite (CrSiβ). It was revealed that the activity of the CrSiβ catalyst was dependent on the dispersion of Cr species and the content of initial highly-dispersed Cr6+ oxides. Namely, the oxygen of terminal Cr = O bonds in initial Cr6+ oxides could rapidly react with propane molecules, thus generating the coordinatively unsaturated Cr3+ oxides as active sites for the redox cycles of CO2-ODP. In this redox cycle, the unsaturated Cr3+site takes an oxygen from a CO2 molecule and then the activated oxygen reacts with propane to produce H2O and propene. This finding is not only important for the molecular understanding of the CrOx catalytic properties, but also is beneficial for the rational design of more efficient CrOx catalysts for dehydrogenation reactions including CO2-ODP.