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Fast detection and structural identification of carbocations on zeolites by dynamic nuclear polarization enhanced solid-state NMR

Xiao, Dong; Xu, Shutao; Brownbill, Nick J.; Paul, Subhradip; Chen, Li-Hua; Pawsey, Shane; Aussenac, Fabien; Su, Bao-Lian; Han, Xiuwen; Bao, Xinhe; Liu, Zhongmin; Blanc, Frédéric

Fast detection and structural identification of carbocations on zeolites by dynamic nuclear polarization enhanced solid-state NMR Thumbnail


Authors

Dong Xiao

Shutao Xu

Nick J. Brownbill

Subhradip Paul

Li-Hua Chen

Shane Pawsey

Fabien Aussenac

Bao-Lian Su

Xiuwen Han

Xinhe Bao

Zhongmin Liu

Frédéric Blanc



Abstract

Acidic zeolites are porous aluminosilicates used in a wide range of industrial processes such as adsorption and catalysis. The formation of carbocation intermediates plays a key role in reactivity, selectivity and deactivation in heterogeneous catalytic processes. However, the observation and determination of carbocations remain a significant challenge in heterogeneous catalysis due to the lack of selective techniques of sufficient sensitivity to detect their low concentrations. Here, we combine 13C isotopic enrichment and efficient dynamic nuclear polarization magic angle spinning nuclear magnetic resonance spectroscopy to detect carbocations in zeolites. We use two dimensional 13C–13C through-bond correlations to establish their structures and 29Si–13C through-space experiments to quantitatively probe the interaction between multiple surface sites of the zeolites and the confined hydrocarbon pool species. We show that a range of various membered ring carbocations are intermediates in the methanol to hydrocarbons reaction catalysed by different microstructural β-zeolites and highlight that different reaction routes for the formation of both targeted hydrocarbon products and coke exist. These species have strong van der Waals interaction with the zeolite framework demonstrating that their accumulation in the channels of the zeolites leads to deactivation. These results enable understanding of deactivation pathways and open up opportunities for the design of catalysts with improved performances.

Citation

Xiao, D., Xu, S., Brownbill, N. J., Paul, S., Chen, L., Pawsey, S., …Blanc, F. (2018). Fast detection and structural identification of carbocations on zeolites by dynamic nuclear polarization enhanced solid-state NMR. Chemical Science, 9(43), 8184-8193. https://doi.org/10.1039/c8sc03848a

Journal Article Type Article
Acceptance Date Oct 2, 2018
Online Publication Date Oct 2, 2018
Publication Date Nov 21, 2018
Deposit Date Nov 22, 2018
Publicly Available Date Nov 26, 2018
Journal Chemical Science
Print ISSN 2041-6520
Electronic ISSN 2041-6539
Publisher Royal Society of Chemistry
Peer Reviewed Peer Reviewed
Volume 9
Issue 43
Pages 8184-8193
DOI https://doi.org/10.1039/c8sc03848a
Keywords General Chemistry
Public URL https://nottingham-repository.worktribe.com/output/1301603
Additional Information : This document is Similarity Check deposited; : Supplementary Information; : Dong Xiao (ORCID); : Shutao Xu (ORCID); : Subhradip Paul (ORCID); : Li-Hua Chen (ORCID); : Bao-Lian Su (ORCID); : Xinhe Bao (ORCID); : Frédéric Blanc (ORCID); : Frédéric Blanc (ResearcherID); : Single-blind; : Received 28 August 2018; Accepted 2 October 2018; Accepted Manuscript published 2 October 2018; Advance Article published 17 October 2018; Version of Record published 7 November 2018

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