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An In-Depth Mechanistic Study of Ru Catalysed Aqueous Methanol Dehydrogenation and Prospects for Future Catalyst Design

preprint
submitted on 17.07.2019 and posted on 18.07.2019 by Nitish Govindarajan, V. Sinha, Monica Trincado, Hansjörg Grützmacher, E.J. Meijer, Bas de Bruin
Herein we provide mechanistic insights into the dehydrogenation of aqueous methanol catalysed by the [Ru(trop2dae)] complex (which is in-situ generated from [Ru(trop2dad)]), established by density functional theory based molecular dynamics (DFT-MD) and static DFT calculations incorporating explicit solvent molecules. The aqueous solvent proved to participate actively in various stages of the catalytic cycle including the catalyst activation process, and the key reaction steps involving C-H activation and hydrogen production. The aqueous solvent forms an integral part of the reactive system for the C-H activation steps in the [Ru(trop2dae)] system, with strong hydrogen bond interactions with the anionic oxygen (RO-, R = CH3, CH2OH, HCO) and hydride moieties formed along the reaction pathway. In contrast to the [Ru(trop2dad)] catalyst, C-H activation and hydrogen production does not proceed via a metal-ligand cooperative pathway for the [Ru(trop2dae)] system. The pKa of the coordinated amine donors in these complexes provides a rationale for the divergent reactivity, and the obtained mechanistic information provides new guidelines for the rational design of active and additive free catalytic systems for aqueous methanol dehydrogenation.

Funding

This work is part of the Industrial Partnership Programme (IPP) Computational Sciences for Energy Research (project 13CSER003 (V.S) and project 14CSER044 (N.G)) which is financially supported by the Netherlands Organization for Scientific Research (NWO) and Shell Global International Solutions B.V.

V.S and B.d.B acknowledge support from the Research Priority Area Sustainable chemistry of the University of Amsterdam.

The calculations were carried out on the Dutch national e-infrastructure (Cartesius) with the support of the SURF cooperative.

M. T. and H. G. acknowledge the support from the Schweizer Nationalfonds (SNF, No. 2-77199-18) and Eidgenössische Hochschule Zürich.

History

Email Address of Submitting Author

b.debruin@uva.nl

Institution

University of Amsterdam, Van 't Hoff Institute for Molecular Sciences

Country

The Netherlands

ORCID For Submitting Author

0000-0002-3482-7669

Declaration of Conflict of Interest

No conflict of interest

Version Notes

First submission.

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