QSTEM-based HAADF-STEM image analysis of Mo/V distribution in MoVTeTaO M1 phase and their correlations with surface reactivity

Abstract Three probability models (Model 1–3) were advanced and investigated in this study based on metal distributions determined by the QSTEM-based HAADF-STEM image analysis. The correlations between the Mo/V distributions in MoVTeTaO M1 phase catalysts and their catalytic behavior in propane ammoxidation were proposed for Model 1 (based on the probability of finding 1–2 V 5+ cations in the proposed S3-S4-S4-S7-S7 catalytic center), Model 2 (based on the total V content in the S2-S4-S4-S7-S7 catalytic center), and Model 3 (based on the probability of finding more than 2 V cations in the S2-S4-S4-S7-S7 catalytic center). Model 1 suggested V 5+ in S3 may activate propane. Model 2 and Model 3 emphasized the importance of total V content and multiple VO x sites in the S2-S4-S4-S7-S7 catalytic center for catalytic reactivity in propane ammoxidation, respectively.