The performance of the nine catalysts in C3-oxidation, in terms of propane conversion and acrylic acid selectivity (Fig. ), shows a wide range of behaviors in the nine selected vanadium-based catalysts. These catalysts have different activity, i.e., they react with propane in different amounts, as indicated by the different propane conversions profiles (Fig. ). MoVOx is much more active than the other catalysts and converts 58.8 % of the initial propane at 300 ºC. At higher temperatures, MoVTeNbOx, a-VPP, VPP and V2O5, achieve conversions higher than ca. 20 %, with MoVTeNbOx being the most active catalyst among them. β-VOPO4, α-VWOPO4, α-VOPO4 and VWPOx achieve significantly lower conversions (below ca. 10 %), even at the highest applied temperature. These catalysts are therefore the least active materials. Several products are formed from the initial propane on each catalyst, including the value-added acrylic acid and propylene, as well as the undesirable CO2. In our analysis, we focus on acrylic acid because the formation of this product involves a complex interplay of processes. The acrylic acid selectivity measured at each temperature of the catalyst test is shown in Fig. . Acrylic acid is a consecutive product of the propane oxidation reaction. It is formed after propane transformation to propylene, but before the total oxidation product CO2 (see eq. 1-3). For this reason, its formation is only observed at intermediate propane-conversion levels (Fig. ).