Roles of Enhancement of C−H Activation and Diminution of C−O Formation Within M1‐Phase Pores in Propane Selective Oxidation
Roles of Enhancement of C−H Activation and Diminution of C−O Formation Within M1‐Phase Pores in Propane Selective Oxidation
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DOI：
10.1002/cctc.202001642
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发表时间：
2020-11
期刊：
影响因子：
4.5
通讯作者：
Yilang Liu;Adam Twombly;Yanliu Dang;Anne Mirich;S. Suib;P. Deshlahra
中科院分区：
文献类型：
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作者：
Yilang Liu;Adam Twombly;Yanliu Dang;Anne Mirich;S. Suib;P. Deshlahra
丙烷和丙烯在M1相MoVTeNb复合氧化物催化剂上的氧化表现出较高的丙烯醛和丙烯酸选择性。我们探测的反应物分子的能力，以访问这些氧化物的七边形孔内的催化位点，并分析限制选择性的基本步骤。在MoVTeNbO上测得的丙烷/环己烷活化速率比几乎比非微孔VOx/SiO2高一个数量级，这表明M1相孔对丙烷活化的重要贡献，因为两种分子通过同源限速C-H活化反应。密度泛函理论表明，所需的C3 H8脱氢和C3 H6烯丙基氧化为丙烯醛和丙烯酸受到C-H活化步骤的限制，而不太有价值的含氧化合物通过C-O键形成的步骤形成。当这些活化发生在孔内时，计算的C-O形成的活化势垒总是高于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。这些结果表明孔限制的作用和框架，以评估选择性限制在烃氧化涉及一个复杂的网络的顺序和平行的步骤。
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 VOx/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.