Propane and propene oxidations on M1 phase MoVTeNb mixed oxide catalysts exhibit relatively high selectivity to acrolein and acrylic acid. We probe the ability of the reactant molecules to access the catalytic sites inside the heptagonal pores of these oxides and analyze elementary steps that limit selectivity. Measured propane/cyclohexane activation rate ratios on MoVTeNbO are nearly an order of magnitude higher than non‐microporous VO_x/SiO₂, which suggests significant contribution of M1 phase pores to propane activation because both molecules react via homologous rate‐limiting C−H activation. Density functional theory suggests that desired C₃H₈ dehydrogenation and C₃H₆ allylic oxidation to acrolein and acrylic acid are limited by C−H activation steps, while less valuable oxygenates form via steps limited by C−O bond formation. Calculated activation barriers for C−O formation are invariably higher than C−H activation when these activations occur inside the pores, suggesting that reactions restricted within the pores are highly selective to desired products. These results demonstrate the role of pore confinement and a framework to assess selectivity limitation in hydrocarbon oxidations involving a complex network of sequential and parallel steps.

中文翻译：

---

丙烷选择性氧化中M1相孔内C H活化增强和C O形成减少的作用

M1相MoVTeNb混合氧化物催化剂上的丙烷和丙烯氧化对丙烯醛和丙烯酸具有较高的选择性。我们探讨了反应物分子访问这些氧化物的七边形孔内催化位点的能力，并分析了限制选择性的基本步骤。在MoVTeNbO上测得的丙烷/环己烷活化速率比比非微孔VO _x / SiO ₂高近一个数量级，这表明M1相孔对丙烷活化有重要贡献，因为两个分子均通过同源限速CH-H活化反应。密度泛函理论表明所需的C ₃ H ₈脱氢和C ₃ H ₆烯丙基氧化成丙烯醛和丙烯酸受CH活化步骤的限制，而有价值的含氧化合物则受受CH键形成限制的步骤的形成。当这些活化作用发生在孔内时，计算出的形成C-O的活化障碍总是高于C-H活化，这表明限制在孔内的反应对所需产物具有高度选择性。这些结果证明了孔隙限制的作用，以及评估烃氧化中选择性限制的框架，该氧化涉及顺序和平行步骤的复杂网络。