Due to the vigorous development of shale gas production technology, the aromatization of light alkanes has become more attractive for the chemical industry. Ethane dehydrogenation/aromatization over Zn/ZSM-5 catalyst was investigated using density functional theory calculations to clarify the intrinsic effects of introducing a Zn modifier and CO₂ co-reactant on the catalytic activity and performance. Introducing Zn to HZSM-5 resulted in the creation of new active sites composed of (Zn–O–Zn)²⁺ species and thus altered the reaction pathways and reduced the kinetic barriers of ethane dehydrogenation. Moreover, Zn/ZSM-5 significantly suppressed methane by-product formation as compared to the unmodified ZSM-5, leading to an increased selectivity to aromatic products. In the presence of CO₂, the H₂O produced via the reverse water gas shift (RWGS) reaction could hydrolyze the (Zn–O–Zn)²⁺ active sites and produce weaker acid sites, which correspond to the increased barriers for ethane dehydrogenation. The participation of H₂O in ethane conversion also reduced the catalytic activity of Zn/ZSM-5. The present DFT results predict that adding Pt or Fe as a second modifier for Zn/ZSM-5 helps to prevent the hydrolysis of (Zn–O–Zn)²⁺ active sites and minimize the negative effect of H₂O on ethane conversion, potentially leading to CO₂-assisted dehydrogenation/aromatization of light alkanes.

中文翻译：

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Zn / ZSM-5上乙烷脱氢和芳构化的机理理解：Zn改性和CO2共反应物的影响

由于页岩气生产技术的蓬勃发展，轻链烷烃的芳构化已对化学工业更具吸引力。使用密度泛函理论计算研究了Zn / ZSM-5催化剂上的乙烷脱氢/芳构化，以阐明引入Zn改性剂和CO ₂共反应剂对催化活性和性能的内在影响。在HZSM-5中引入Zn导致了由（Zn–O–Zn）²⁺物种组成的新活性位点的产生，从而改变了反应途径并减少了乙烷脱氢的动力学障碍。此外，与未改性的ZSM-5相比，Zn / ZSM-5显着抑制了甲烷副产物的形成，从而提高了对芳族产物的选择性。在CO存在下_{如图2所示}，通过反向水煤气变换（RWGS）反应产生的H ₂ O可以水解（Zn–O–Zn） ²⁺活性位点，并产生较弱的酸位点，这对应于乙烷脱氢的障碍增加。H ₂ O参与乙烷转化也降低了Zn / ZSM-5的催化活性。目前的DFT结果表明，添加Pt或Fe作为Zn / ZSM-5的第二种改性剂有助于防止（Zn–O–Zn） ²⁺活性位点水解，并最大程度降低H ₂ O对乙烷转化的负面影响，可能导致CO ₂辅助的轻烷烃脱氢/芳构化。