QM/MM study of the stability of dimethyl ether in zeolites H-ZSM-5 and H-Y

Nastase, Stefan Adrian F., Catlow, C. Richard A. and Logsdail, Andrew J 2021. QM/MM study of the stability of dimethyl ether in zeolites H-ZSM-5 and H-Y. Physical Chemistry Chemical Physics 23 (3) , pp. 2088-2096. 10.1039/D0CP05392A

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Abstract

The methanol-to-hydrocarbons (MTH) process transforms C1 carbon sources to higher hydrocarbons, but details of the mechanism that leads to the formation of the first carbon-carbon bond remain unclear. Here, we present a computational investigation of how a crucial intermediate, dimethyl ether (DME), interacts with different zeolite catalysts (H-ZSM-5, H-Y) to gain insight into the initial stages in the MTH process. We use QM/MM computational simulations to model the conversion of methanol to DME in H-ZSM-5, which is a well characterised and important reaction intermediate. We analyse and compare the stability of DME on several acid sites in H-ZSM-5 and H-Y, and show that the more acidic and open “intersection sites” in the H-ZSM-5 framework are able to bond strongest with DME, with complete deprotonation of the acid site occurring. The conversion of methanol to DME in H-ZSM-5 is observed as requiring a higher activation energy than framework methoxylation, which indicates that a stepwise (indirect) mechanism, through a methoxy intermediate, is the most likely route to DME formation during the initiation of the MTH process.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Chemistry Cardiff Catalysis Institute (CCI)
Additional Information:	This article is licensed under a Creative Commons Attribution 3.0 Unported Licence
Publisher:	Royal Society of Chemistry
ISSN:	1463-9076
Funders:	EPSRC
Date of First Compliant Deposit:	4 January 2021
Date of Acceptance:	23 December 2020
Last Modified:	19 Mar 2021 11:27
URI:	http://orca.cf.ac.uk/id/eprint/137283

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