We develop a simulation toolset employing density functional theory in conjunction with grand canonical Monte Carlo (GCMC) to study coke formation on Fe-based catalysts during propane dehydrogenation (PDH). As expected, pure Fe surfaces develop stable graphitic coke structures and rapidly deactivate. We find that coke formation is markedly less favorable on Fe₃C and FeS surfaces. Fe-Al alloys display varying degrees of coke resistance, depending on their composition, suggesting that they can be optimized for coke resistance under PDH conditions. Electronic structure analyses show that both electron-withdrawing effects (on Fe₃C and FeS) and electron-donating effects (on Fe-Al alloys) destabilize adsorbed carbon. On the alloy surfaces, a geometric effect also isolates Fe sites and disrupts the formation of graphitic carbon networks. This work demonstrates the utility of GCMC for studying the formation of disordered phases on catalyst surfaces and provides insights for improving the coke resistance of Fe-based PDH catalysts.

中文翻译：

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模拟催化剂表面的相形成：碳氢化合物环境中的焦炭形成和抑制

我们开发了一个模拟工具集，采用密度泛函理论与正则蒙特卡罗 (GCMC) 相结合来研究丙烷脱氢 (PDH) 过程中铁基催化剂上的焦炭形成。正如预期的那样，纯铁表面会形成稳定的石墨焦结构并迅速失活。我们发现在 Fe ₃ C 和 FeS 表面上焦炭的形成明显不太有利。Fe-Al 合金表现出不同程度的抗焦炭性，这取决于它们的成分，这表明它们可以在 PDH 条件下针对抗焦炭性进行优化。电子结构分析表明，两种吸电子效应（对 Fe ₃C 和 FeS）和给电子效应（在 Fe-Al 合金上）使吸附的碳不稳定。在合金表面，几何效应还隔离了 Fe 位点并破坏了石墨碳网络的形成。这项工作证明了 GCMC 在研究催化剂表面无序相形成方面的实用性，并为提高 Fe 基 PDH 催化剂的抗焦性提供了见解。