Selective oxidation of long-chain fatty alcohols into acids is an important value-added reaction. However, exploring the basic catalytic steps over Pt-based catalysts throughout the entire oxidation process is still ambiguous. In this work, we systematically investigated the synergistic mechanisms of adsorption, reaction, and diffusion over Pt/MCM-41 for normal/isomeric alcohols oxidation into acids via molecular dynamics, in-situ characterization, and experiments. Specifically, diffusion coefficients decrease with the increase of the molecular weight of normal molecules due to the increased van der Waals forces, while isomeric alcohols exhibit more complex patterns originated from the steric hindrance between Pt particles and mesopores. To quantitatively describe this pattern, a cluster size descriptor of $d_{\mathit{Pt}}^{0.75}\times d_{\mathit{Pore}}^{0.25}$$d_{\mathit{Pt}}^{0.75}\times d_{\mathit{Pore}}^{0.25}$ was defined. Notably, 2-ethylhexanol exhibits the best self-diffusion coefficients at the descriptor value of 3.14. Correspondingly, the oxidation of 2-ethylhexanol to 2-ethylhexanoic acid displays highest reaction conversion (68.67 %) and selectivity (65.59 %).

中文翻译：

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破译 Pt/MCM-41 上脂肪醇氧化为脂肪酸的传质和扩散行为


长链脂肪醇选择性氧化成酸是一种重要的增值反应。然而，在整个氧化过程中探索 Pt 基催化剂的基本催化步骤仍然不明确。在这项工作中，我们通过分子动力学、原位表征和实验系统研究了 Pt/MCM-41 上吸附、反应和扩散对正醇/异构体醇氧化成酸的协同机制。具体来说，由于范德华力的增加，扩散系数随着正常分子分子量的增加而降低，而异构体醇则表现出更复杂的模式，这源于 Pt 颗粒和介孔之间的空间位阻。为了定量描述这种模式，定义了 $d_{\mathit{Pt}}^{0.75}\times d_{\mathit{孔径}}^{0.25}$ 的簇大小描述符。值得注意的是，2-乙基己醇在描述符值为 3.14 时表现出最佳的自扩散系数。相应地，2-乙基己醇氧化为 2-乙基己酸表现出最高的反应转化率 （68.67 %） 和选择性 （65.59 %）。