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Influence of topology and brønsted acid site presence on methanol diffusion in zeolites beta and MFI

Botchway, Cecil H., Tia, Richard, Adei, Evans, O'Malley, Alexander J., Dzade, Nelson Y., Hernandez-Tamargo, Carlos and de Leeuw, Nora H. 2020. Influence of topology and brønsted acid site presence on methanol diffusion in zeolites beta and MFI. Catalysts 10 (11) , 1342. 10.3390/catal10111342

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Abstract

Detailed insight into molecular diffusion in zeolite frameworks is crucial for the analysis of the factors governing their catalytic performance in methanol-to-hydrocarbons (MTH) reactions. In this work, we present a molecular dynamics study of the diffusion of methanol in all-silica and acidic zeolite MFI and Beta frameworks over the range of temperatures 373–473 K. Owing to the difference in pore dimensions, methanol diffusion is more hindered in H-MFI, with diffusion coefficients that do not exceed 10×10−10 m2s−1. In comparison, H-Beta shows diffusivities that are one to two orders of magnitude larger. Consequently, the activation energy of translational diffusion can reach 16 kJ·mol−1 in H-MFI, depending on the molecular loading, against a value for H-Beta that remains between 6 and 8 kJ·mol−1. The analysis of the radial distribution functions and the residence time at the Brønsted acid sites shows a greater probability for methylation of the framework in the MFI structure compared to zeolite Beta, with the latter displaying a higher prevalence for methanol clustering. These results contribute to the understanding of the differences in catalytic performance of zeolites with varying micropore dimensions in MTH reactions.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Chemistry
Additional Information: This article is an open accessarticle distributed under the terms and conditions of the Creative Commons Attribution(CC BY) license (http://creativecommons.org/licenses/by/4.0/).
Publisher: MDPI
ISSN: 2073-4344
Funders: EPSRC, NERC, Royal Society and DFID
Date of First Compliant Deposit: 3 December 2020
Date of Acceptance: 14 November 2020
Last Modified: 18 Dec 2020 14:44
URI: http://orca.cf.ac.uk/id/eprint/136758

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