Revealing nature of active site and reaction mechanism of supported chromium oxide catalyst in propane direct dehydrogenation

Abstract Chromium oxide is the conventional catalyst for propane direct dehydrogenation. However, the active site and reaction mechanism are still remaining unresolved due to the complicated valence of chromium and co-exists of several active sites. In this work, DFT calculations are performed to reveal the nature of active center and reaction mechanism for the supported chromium catalyst on silica. Three valences of chromium including Cr3+, Cr5+, and Cr6+ are examined to give a unbiased survey of reactivity. The reaction pathway and C–H activation are carefully examined. Moreover, a detailed analysis of active site regeneration is performed. The reactivities of different oxygen groups attached to Cr including terminal, bridge, and OH group are evaluated at the same footing. Furthermore, the calculations also reveal the intrinsic catalytic properties of chromium which show comparable abilities with oxygen groups. The influence from OH group on support is also evaluated. The comparisons of different reaction pathway give useful indication on the possible reaction mechanism. In the end, the most favorable active site is identified. The current work not only deepen the understanding of catalytic properties of supported chromium catalyst but also supply the doable optimization methods for further improvements.