Methane dehydroaromatization (MDA) is a promising approach for direct methane transformation to aromatics and hydrogen. The benchmark catalyst Mo/H-ZSM-5 struggles to find commercial adoption because of thermodynamically-limited yields and rapid coking on Brønsted acid and molybdenum carbide species, especially on zeolite external surfaces. Here, gas-phase atomic layer deposition (ALD) overcoats H-ZSM-5 external surfaces with SiO2 or Al2O3. NH3-TPD, HRTEM, and textural properties show that these overcoats exclusively passivate zeolite external surfaces. Under MDA conditions, SiO2 gives softer coke and increases cumulative benzene yields by 25%, while Al2O3 strongly decreases yields. H2-TPR and UV-visible and Raman spectroscopy show how the overcoats redisperse the MoOx precatalysts, especially over multiple deactivation and isothermal oxidative regeneration cycles. Combined with 27Al-MAS NMR, MoOx redistribution and dealumination are seen as the causes of long-term deactivation over multiple regeneration cycles, and this process continues to occur regardless of the overcoat. Altogether, the deposition of a small amount of silica on the outer surface of Mo/H-ZSM-5 reduces the formation of hard coke, which could be regenerated by milder methods such as hydrogen treatment.
Ramos-Yataco, Jordy, et al. "Gas-phase surface modification to control catalyst structure and yields in methane dehydroaromatization." Microporous and Mesoporous Materials, vol. 377, Jun. 2024. https://doi.org/10.1016/j.micromeso.2024.113227
Ramos-Yataco, Jordy, Zhang, Xinrui, Alayoglu, Selim, et al., "Gas-phase surface modification to control catalyst structure and yields in methane dehydroaromatization," Microporous and Mesoporous Materials 377 (2024), https://doi.org/10.1016/j.micromeso.2024.113227
@article{osti_2482303,
author = {Ramos-Yataco, Jordy and Zhang, Xinrui and Alayoglu, Selim and Pham, Hien N. and Datye, Abhaya K. and Marks, Tobin J. and Notestein, Justin},
title = {Gas-phase surface modification to control catalyst structure and yields in methane dehydroaromatization},
annote = {Methane dehydroaromatization (MDA) is a promising approach for direct methane transformation to aromatics and hydrogen. The benchmark catalyst Mo/H-ZSM-5 struggles to find commercial adoption because of thermodynamically-limited yields and rapid coking on Brønsted acid and molybdenum carbide species, especially on zeolite external surfaces. Here, gas-phase atomic layer deposition (ALD) overcoats H-ZSM-5 external surfaces with SiO2 or Al2O3. NH3-TPD, HRTEM, and textural properties show that these overcoats exclusively passivate zeolite external surfaces. Under MDA conditions, SiO2 gives softer coke and increases cumulative benzene yields by 25%, while Al2O3 strongly decreases yields. H2-TPR and UV-visible and Raman spectroscopy show how the overcoats redisperse the MoOx precatalysts, especially over multiple deactivation and isothermal oxidative regeneration cycles. Combined with 27Al-MAS NMR, MoOx redistribution and dealumination are seen as the causes of long-term deactivation over multiple regeneration cycles, and this process continues to occur regardless of the overcoat. Altogether, the deposition of a small amount of silica on the outer surface of Mo/H-ZSM-5 reduces the formation of hard coke, which could be regenerated by milder methods such as hydrogen treatment.},
doi = {10.1016/j.micromeso.2024.113227},
url = {https://www.osti.gov/biblio/2482303},
journal = {Microporous and Mesoporous Materials},
issn = {ISSN 1387-1811},
volume = {377},
place = {United States},
publisher = {Elsevier},
year = {2024},
month = {06}}