Issue 12, 2021

Investigating the innate selectivity issues of methane to methanol: consideration of an aqueous environment

Abstract

The higher reactivity of the methanol product over the methane reactant for the direct oxidation of methane to methanol is explored. C–H activation, C–O coupling, and C–OH coupling are investigated as key steps in the selective oxidation of methane using DFT. These elementary steps are initially considered in the gas phase for a variety of fcc (111) pristine metal surfaces. Methanol is found to be consistently more reactive for both C–H activation and subsequent oxidation steps. With an aqueous environment being understood experimentally to have a profound effect on the selectivity of this process, these steps are also considered in the aqueous phase by ab initio molecular dynamics calculations. The water solvent is modelled explicity, with each water molecule given the same level of theory as the metal surface and surface species. Free energy profiles for these steps are generated by umbrella sampling. It is found that an aqueous environment has a considerable effect on the kinetics of the elementary steps yet has little effect on the methane/methanol selectivity-conversion limit. Despite this, we find that the aqueous phase promotes the C–OH pathway for methanol formation, which could enhance the selectivity for methanol formation over that of other oxygenates.

Graphical abstract: Investigating the innate selectivity issues of methane to methanol: consideration of an aqueous environment

Supplementary files

Article information

Article type
Edge Article
Submitted
29 sep 2020
Accepted
01 feb 2021
First published
03 feb 2021
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2021,12, 4443-4449

Investigating the innate selectivity issues of methane to methanol: consideration of an aqueous environment

R. J. Bunting, P. S. Rice, J. Thompson and P. Hu, Chem. Sci., 2021, 12, 4443 DOI: 10.1039/D0SC05402J

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