Reaction mechanism of propane oxidation over Co3O4 nanorods as rivals of platinum catalysts

Abstract

Co3O4 nanorods and Pt/Al2O3 catalysts were synthesized and tested for catalytic oxidation of propane. In comparison to Pt/Al2O3, the catalytic results showed that Co3O4 nanorods were more active for propane oxidation under relatively high space velocity. Kinetic data suggested that the extraction of hydrogen from C-H bonds in propane can be considered as the reaction of kinetic relevance for both Co3O4 nanorods and Pt/Al2O3 catalysts. On both catalysts, propane could be first transformed into C3H7O* species. The intermediates further dissociate and are oxidized into carboxylates, with acetate and/or formate species as the primary products detectable by Fourier-transform infrared spectroscopy (FTIR). These species are later oxidized into CO2 and H2O as final products. However, the specific oxidation pathways might be different over these two catalysts. Over Co3O4 nanorods, propane oxidation appears to take place via the Langmuir-Hinshelwood mechanism. The rate-determining step is the C–H bond activation by the abstraction of H from adsorbed propane on two neighboring oxygen atoms. In contrast, on Pt/Al2O3 catalysts, the propane oxidation reaction follows an Eley-Rideal mechanism, and the rate-determining step is the activation of gaseous C3H8 on a neighboring oxygen atom and a vacant site.