Abstract: With the aim of discovering the effect of indium species on the protolytic activation of isobutane by Brønsted acid sites (BAS), the kinetics of H/D hydrogen exchange between isobutane-d10 and BAS of the InO+/H-BEA zeolite was monitored by 1H MAS NMR spectroscopy. The exchange has been established to occur exclusively between methyl groups of isobutane-d10 and BAS and demonstrates a significant induction period. Dehydrogenation of isobutane to isobutene is observed alongside the H/D exchange in the alkane. Kinetics of protium transfer from BAS to both deuterated isobutane and isobutene are interpreted in terms of the indirect cyclic mechanism of H/D exchange with isobutene as a key intermediate. It is inferred that indium sites perform isobutane dehydrogenation and strongly retain isobutene formed. This accounts for the prolonged induction period in the H/D exchange reaction kinetics. Indium sites located in the zeolite pores decelerate protium transfer from zeolite BAS to isobutane via an indirect H/D exchange mechanism and, contrary to the case with linear alkanes, are not able to facilitate the direct hydrogen exchange between BAS and methyl groups in isobutane.

Cite: Arzumanov S.S. , Gabrienko A.A. , Toktarev A.V. , Freude D. , Stepanov A.G.
H/D Exchange of Isobutane on In-Modified BEA Zeolite Investigated by 1H MAS NMR
The Journal of Physical Chemistry C. 2024. V.128. N39. P.16491-16500. DOI: 10.1021/acs.jpcc.4c04998 WOS Scopus AN OpenAlex

Dates:

Submitted:	Jul 25, 2024
Accepted:	Sep 11, 2024
Published online:	Sep 19, 2024
Published print:	Oct 3, 2024

Identifiers:

Web of science:	WOS:001317069400001
Scopus:	2-s2.0-85204640647
Chemical Abstracts:	2024:2001409
OpenAlex:	W4402625792

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