CoFe2O4 was tested in flow conditions and proved to be completely inactive, indicating that if Co 2+ actually takes part in the catalysis, its contribution is not enough for it to actually take place; Fe 3+ also inverts the spinel, increasing the M-O bond length, and might have an inhibiting effect as well. The effect of the addition of Fe 3+ to Co3O4 has been extensively studied in a previous work on 2-propanol oxidation over Co1+xFe2-xO4. Even very small additions of Fe 3+ in the framework of Co3O4, which was the most active composition, cause the activity to drop. Acetic acid was formed at higher temperatures, while we never detected any such byproduct: this effect could be the result of the different catalyst preparations or of the flow conditions. Interestingly, while MnCo2O4 is most active in the liquid-phase at 200 °C, it is less active than the Co3O4 counterpart in the gas phase. The enhanced Mn activity might then be a liquid-phase effect, related to the presence of a solvent which might, for example, stabilise any reaction intermediate. The negative effect of Mn doping in the gas phase was also observed in other works. The local maximum in activity for Co3O4 is attributed to pure oxidative dehydrogenation. However, even at 200 °C -the same temperature as the catalyst screening in the liquid phase, and even at a low oxygen conversion, an increase in hydrogen content is detected; the formation of hydrogen in other reports on similar systems is either not observed or not discussed. In aerobic oxidations proceeding via pure dehydrogenations, the alcohol is oxidised without the intervention of oxygen by forming molecular hydrogen, which is then combusted into water in a separate step. The net reactions, hence the observed products, are the same, but the mechanism would be completely different. This points to reaction mechanisms in the gas and in the liquid phase which might be completely different. At higher temperatures, the total oxidation of 2-propanol is observed, which likely brings about the reduction of the spinel into a monoxide, as observed by XRD.