Three groups of catalysts can be roughly identified based on the alkane conversion 8 9:;9<# measured during the temperature variation step of the catalyst test (Fig. ): (i) highly active catalysts, containing MoVOx, SmMnO3, and MnWO4; (ii) moderately active catalysts, containing MoVTeNbOx, V2O5, VPP, and a-VPP; and (iii) unactive catalysts, containing the remaining β-VOPO4, αII-VWOPO4, αII-VOPO4, VOPO4*2H2O, and VWPOx. However, some materials are more or less active depending on the reaction, making the classification nontrivial. For instance, MoVTeNbOx is one of the most active catalysts in ethane or propane oxidation, but it has only moderate activity in n-butane oxidation. Additionally, while MoVOx is the most active catalyst in ethane and propane oxidation, SmMnO3 is the most active material for n-butane oxidation. This shows that not only the C-H bond strength in the alkane molecule determines its reactivity, but also the catalyst intrinsic properties and the interaction between the alkane with the material play a role.