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.
|Early online date||03 Feb 2021|
|Publication status||Early online date - 03 Feb 2021|
FingerprintDive into the research topics of 'Investigating the innate selectivity issues of methane to methanol: consideration of an aqueous environment'. Together they form a unique fingerprint.
Direct oxidation of methane to methanolAuthor: Bunting, R., Jul 2021
Supervisor: Hu, P. (Supervisor) & Thompson, J. (Supervisor)
Student thesis: Doctoral Thesis › Doctor of PhilosophyFile