Selective 2-Propanol Oxidation over Unsupported Co3O4 Spinel Nanoparticles: Mechanistic Insights into Aerobic Oxidation of Alcohols

Crystalline Co3O4 nanoparticles with a uniform size of 9 nm as shown by X-ray diffraction (XRD) and transmission electron microscopy (TEM) were synthesized by thermal decomposition of cobalt acetylacetonate in oleyl amine and applied in the oxidation of 2-propanol after calcination. The catalytic properties were derived under continuous flow conditions as function of temperature up to 573 K in a fixed-bed reactor at atmospheric pressure. Temperature-programmed oxidation, desorption (TPD), surface reaction (TPSR) and 2-propanol decomposition experiments were performed to study the interaction of 2-propanol and O2 with the exposed spinel surfaces. Co3O4 selectively catalyzes the oxidative dehydrogenation of 2-propanol yielding acetone and H2O and only to a minor extent the total oxidation to CO2 and H2O at higher temperatures. The superior activity of Co3O4 reaching nearly full conversion with 100% selectivity to acetone at 440 K is attributed to the high amount of active Co3+ species at the catalyst surfac...