(638f) Mechanistic Insights Into the Catalytic Oxidative Dehydrogenation of Propane Over Co3O4 Surfaces

Catalytic fuel combustion shows promising applications in gas turbines and hypersonic jet engines, where promoted catalytic pathways can lower the ignition temperature of fuels and increase the heat sink of such systems [1]. Among a range of metal oxides, cobalt oxide is one of the most active catalysts for complete oxidation of light hydrocarbons. 

In order to understand the mechanisms that control the C-H activation of alkanes over surface O and Co-O site pairs of cobalt oxide under working condition, density functional theory calculations with on-site correction for Coulomb interactions of Co d-electrons (DFT+U method) have been carried out. The stable surface terminations of Co₃O₄ in equilibrium with gas-phase oxygen were determined by surface free energy calculations and the first two C-H bond activation steps in propane dehydrogenation were examined. Co^tetr- terminated (111) and type B (110) terminations were calculated to be the most stable surface terminations at moderate oxygen chemical potentials and temperatures, which is in good agreement with experimental observations.

Type B (110) surface is found to be more reactive than the Co^tetr- terminated (111) surface. The reactivities of different surface oxygen sites are found to be structure sensitive.  In addition, the C-H bond activation was found to be controlled by specific affinity of the oxide surface. The work provides direct insights in the experimental results [2] on the pathways that dominate the dehydrogenation of alkanes over cobalt oxide.

References

1.            Wickham, D.T., et al., Journal of Propulsion and Power, 2001. 17(6): p. 1253-1257.

2.            Di Vece, M., et al., Unpublished work, 2011.