C2H4在Fe3C(100)表面吸附及脱氢裂解的密度泛函理论研究

采用自旋极化密度泛函理论和周期平板模型，对C₂H₄在铁基费托合成催化剂活性相之一Fe₃C（100）表面从热力学和动力学两个方面分析了C₂H₄在Fe₃C（100）表面进行脱氢和裂解反应的竞争性。结果表明，C₂H₄在Fe₃C（100）表面的μ-bridging吸附比π、di-σ吸附更加稳定；C₂H₄与Fe₃C（100）面的相互作用导致C₂H₄的C原子部分发生重新杂化（sp²→sp³），使C原子呈近四面体结构。在Fe₃C（100）表面C₂H₄易于发生脱氢反应，C-C键裂解反应不具有竞争性。亚乙烯基CCH₂和乙烯基CHCH₂是Fe₃C（100）表面最丰的C₂物种，或是C₂H₄参与链增长的主要单体形式。

Density functional theory study of the adsorption and reaction of C2H4 on Fe3C(100)

Spin-polarized density functional theory (DFT) and a periodic slab model were employed to investigate the adsorption of C₂H₄ on Fe₃C(100), which is an active phase of an Fe-based catalyst for Fischer-Tropsch synthesis. The competition between dehydrogenation and cleavage of C₂H₄ was analyzed. The μ-bridging adsorption mode is more stable than the π or di-σ adsorption modes. Partial rehybridization of the C atoms of C₂H₄ (sp²→sp³) caused by the interaction of C₂H₄ with the Fe₃C(100) surface resulted in the C atoms in C₂H₄ having a quasi-tetrahedron geometry. On Fe₃C(100) dehydrogenation of C₂H₄ occurs, while C-C bond cleavage is not competitive. The calculations indicated that vinylidene (CCH₂) and vinyl (CHCH₂) species are the most abundant C₂ species, which may be the major monomeric forms of C₂H₄ in the chain growth in Fischer-Tropsch synthesis.