Combining quasielastic neutron scattering and molecular dynamics to study methane motions in ZSM-5

Hawkins, A. P. , Zachariou, A., Silverwood, I. P., Yong, C., Collier, P., Todorov, I., Howe, R. F., Parker, S. F. and Lennon, D. (2022) Combining quasielastic neutron scattering and molecular dynamics to study methane motions in ZSM-5. Journal of Chemical Physics, 157(18), 184702. (doi: 10.1063/5.0123434)

Abstract

Quasi-elastic neutron scattering (QENS) and molecular dynamics (MD) simulations are applied in combination to investigate the dynamics of methane in H-ZSM-5 zeolite catalysts used for methanol-to-hydrocarbons (MTH) reactions. Methane is employed as an inert model for the methanol reaction feedstock and studies are made of the fresh catalyst and used catalysts with varying levels of coke build-up to investigate the effect of coking on reactant mobility. Measurements are made in the temperature range from 5 - 373 K. Methane mobility under these conditions is found to be extremely high in fresh ZSM-5, with the majority of movements occurring too fast to be resolved by the QENS instrument used. A small fraction of molecules undergoing jump diffusion on QENS timescales is identified and found to correspond with short-range jump diffusion within single zeolite pores as identified in MD simulations. Agreement between QENS and MD mobility measurements is found to be within 50%, validating the simulation approach employed. Methane diffusion is found to be minimally affected by moderate levels of coke build-up, while highly coked samples result in the confinement of methane to single pores within the zeolite with minimal long-range diffusion.

• Item Type: Articles
• Additional Information: The work was funded by Johnson Matthey plc. through the provision of industrial CASE studentships in partnership with the EPSRC (AZ (EP/N509176/1), APH (EP/P510506/1).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Lennon, Professor David and Zachariou, Miss Andrea and Hawkins, Alexander
• Authors: Hawkins, A. P., Zachariou, A., Silverwood, I. P., Yong, C., Collier, P., Todorov, I., Howe, R. F., Parker, S. F., and Lennon, D.
• College/School: College of Science and Engineering > School of Chemistry
• Journal Name: Journal of Chemical Physics
• Publisher: American Institute of Physics
• ISSN: 0021-9606
• ISSN (Online): 1089-7690
• Published Online: 21 October 2022
• Copyright Holders: Copyright © 2022 The Authors
• First Published: First published in Journal of Chemical Physics 157(18): 184702
• Publisher Policy: Reproduced under a Creative Commons License

Project Code	Award No	Project Name	Principal Investigator	Funder's Name	Funder Ref	Lead Dept
172233		Anderson ICASE 2015 (Selex)	Heather Lambie	Engineering and Physical Sciences Research Council (EPSRC)	IND CASE EP/N509176/1	S&E - Academic & Student Administration
172921		EPSRC 2016 Industrial Case Award (iCASE) - Jaguar	Miles Padgett	Engineering and Physical Sciences Research Council (EPSRC)	16000061 - EP/P510506/1	Research and Innovation Services