Radicals in carbonaceous residue deposited on mordenite from methanol

Spencer, N. A., Ditzel, E. J., Hargreaves, J. S. J. and Sproules, S. (2016) Radicals in carbonaceous residue deposited on mordenite from methanol. Journal of Materials Chemistry A, 4(18), pp. 7036-7044. (doi: 10.1039/C6TA01053A)

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It is shown that control of the degree of coking can lead to the observation of hyperfine structures in the carbonaceous residues deposited from methanol over mordenite (H-MOR) at temperatures relevant to the conversion of methanol to hydrocarbons. EPR measurements of the catalyst samples at various times on stream have been recorded, with a rich hyperfine splitting pattern observed in the early stages of the reaction. Interpretation of the EPR data with the aid of density functional theoretical calculations has afforded the first definitive assignment of the radical cations formed in high temperature coke. The results detail a shortlist of six species: 2,3/2,6/2,7-dimethylnaphthalenium, 2,3,6-trimethylnaphthalenium, 2,3,6,7-tetramethylnaphthalenium, and anthracenium radical cations whose proton hyperfine splitting profiles match the experimental spectra; 2,3,6,7-tetramethylnaphthalenium showed the best agreement. The observation of these particular isomers of polymethylnaphthalene suggest the formation of more highly branched polyaromatic species is less likely within the confines of the H-MOR 12-membered ring channel. These radicals formed when the catalyst is active may constitute key intermediates in the conversion of methanol to light olefins.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Sproules, Dr Stephen and Hargreaves, Professor Justin
Authors: Spencer, N. A., Ditzel, E. J., Hargreaves, J. S. J., and Sproules, S.
College/School:College of Science and Engineering > School of Chemistry
Journal Name:Journal of Materials Chemistry A
Publisher:Royal Society of Chemistry
ISSN (Online):2050-7496
Published Online:23 March 2016
Copyright Holders:Copyright © 2016 The Royal Society of Chemistry
First Published:First published in Journal of Materials Chemistry A 2016(4):7036-7044
Publisher Policy:Reproduced under a Creative Commons License

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