Issue 15, 2024

Stabilization of intermediate Mo oxidation states by Nb doping enhancing methane aromatization on Mo/HZSM-5 catalysts

Abstract

The dehydroaromatization of the naturally abundant methane is a promising process to produce aromatics and COx-free hydrogen. Low-temperature activity, regenerability and time-on-stream stability are fundamental challenges for the industrial use of the commonly studied benzenoid-selective Mo/HZSM-5 catalysts. We report a promotional effect of Nb doping on the activity and stability of Mo/HZSM-5 catalysts between 600 and 700 °C. Nb addition enhances benzene yields measurably at all investigated temperatures. An increased thermal stability of MoNb/HZSM-5 compared to Mo/HZSM-5 catalysts was found upon exposure to multiple consecutive reaction and oxidative treatment cycles, thus resulting in higher restorability of activity which extends the catalyst lifetime. While high-resolution electron microscopy showed homogeneous mixing of Mo and Nb on the catalyst, in situ time-resolved Mo K-edge X-ray absorption spectroscopy, supported by ex situ and time-resolved in situ near-ambient pressure X-ray photoelectron spectroscopy measurements, revealed a distinct interaction between the transition metals, involving a partial reduction of the otherwise stable Nb and concurrent oxidation of Mo which leads to increased stability of Mo5+/Mo4+ states. These effects were correlated to the enhanced activity and regenerability of the MoNb/HZSM-5 catalyst for methane dehydroaromatization.

Graphical abstract: Stabilization of intermediate Mo oxidation states by Nb doping enhancing methane aromatization on Mo/HZSM-5 catalysts

Supplementary files

Article information

Article type
Paper
Submitted
05 dec 2023
Accepted
22 feb 2024
First published
22 feb 2024
This article is Open Access
Creative Commons BY license

J. Mater. Chem. A, 2024,12, 8869-8884

Stabilization of intermediate Mo oxidation states by Nb doping enhancing methane aromatization on Mo/HZSM-5 catalysts

S. Peters, S. Bartling, M. Parlinska-Wojtan, A. Wotzka, A. G. Buzanich, S. Wohlrab and A. M. Abdel-Mageed, J. Mater. Chem. A, 2024, 12, 8869 DOI: 10.1039/D3TA07532J

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