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Mechanistic Understanding of Ethane Dehydrogenation and Aromatization over Zn/ZSM-5: Effects of Zn Modification and CO2 Co-reactant

Abstract

Due to the vigorous development of shale gas production technology, the aromatization of light alkanes has become more attractive for chemical industry. The ethane dehydrogenation/aromatization over Zn/ZSM-5 catalyst was investigated by density functional theory calculations to clarify the intrinsic effects of introducing 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 increased barriers for the ethane dehydrogenation. H2O participation 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.

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Supplementary files

Article information


Submitted
05 Aug 2020
Accepted
13 Oct 2020
First published
13 Oct 2020

Catal. Sci. Technol., 2020, Accepted Manuscript
Article type
Paper

Mechanistic Understanding of Ethane Dehydrogenation and Aromatization over Zn/ZSM-5: Effects of Zn Modification and CO2 Co-reactant

H. Fan, X. Nie, H. Wang, M. J. Janik, C. Song and X. Guo, Catal. Sci. Technol., 2020, Accepted Manuscript , DOI: 10.1039/D0CY01566K

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