Mechanistic insights into the oxidative coupling of methane over a Li/MgO catalyst: an experimental and microkinetic modeling study

Abstract

This study investigates the oxidative coupling of methane (OCM) using a Li/MgO catalyst in a packed bed reactor. Experiments were conducted at a pressure of 110 Torr over a temperature range of 873–1173 K. Stable products, including alcohols, aldehydes, ketones, and C3 hydrocarbons, were quantified using synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). Methyl and ethyl radicals were definitively identified, emphasizing their critical role in the formation of C2–C3 hydrocarbons. Based on these speciation results, a microkinetic model for the OCM reaction over Li/MgO was developed. The reaction network analysis revealed that the main pathway for COx generation involves the conversion of CH3 to CH3O(s)/CH3O through surface and gas-phase reactions. Gas-phase reactions also promote the deep oxidation of C2H4. Sensitivity analysis indicated that methane activation is primarily governed by surface reactions, while the coupling of CH3 to form C2H6 is mainly driven by gas-phase reactions. Both surface and gas-phase reactions contribute equally to the formation of C2H4. Additionally, the pressure dependence analysis demonstrated that the high-pressure limit of the CH3 coupling reaction restricts the increase in C2 yield as pressure rises. In conclusion, this study provides a comprehensive investigation into the OCM speciation pool, develops a microkinetic model aligned with experimental findings, and elucidates the reaction network driven by free radicals. These insights offer valuable guidance for optimization reaction conditions and catalyst performance.

Graphical abstract: Mechanistic insights into the oxidative coupling of methane over a Li/MgO catalyst: an experimental and microkinetic modeling study

Supplementary files

Article information

Article type
Paper
Submitted
22 Sep 2024
Accepted
15 Oct 2024
First published
18 Oct 2024

Catal. Sci. Technol., 2024, Advance Article

Mechanistic insights into the oxidative coupling of methane over a Li/MgO catalyst: an experimental and microkinetic modeling study

Z. Xiong, J. Guo, Y. Deng, M. Zeng, Z. Wang, Z. Zhou, W. Yuan and F. Qi, Catal. Sci. Technol., 2024, Advance Article , DOI: 10.1039/D4CY01132E

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements