Selected metal oxides for C[sbnd]H bond activation of n-octane and propensity for COx formation: An empirical study

Abstract

The propensity of a range of monometallic oxide catalysts, namely, TiO2; V2O5; Cr2O3; MnO2; Fe2O3; Co3O4; CuO; ZnO; and CeO2, to form carbon oxides during the oxidative activation of n-octane was investigated. The catalysts showed varied selectivity at iso-conversion. PXRD, BET surface area analysis, H2-TPR, NH3-TPD and O2-TPD were employed to probe the physical and chemical properties of the catalysts in order to understand their catalytic behaviour. The activity of a metal oxide in the activation of n-octane was found to be dependent on its extent of reduction, the extent to which molecular oxygen chemisorbs to its surface and surface acidity. It was also observed that metal oxides with a low band gap energy showed a higher propensity toward total oxidation than those with high energy. All these factors played a key role in carbon oxide formation, some more than others depending on the oxide in question, with TiO2 showing the lowest selectivity and CuO the highest.