Insight into the Formation and Reactivity of Framework-Bound Methoxide Species in H-ZSM-5 from Static and Dynamic Molecular Simulations

• Published in: ChemCatChem Vol. 6; no. 7; pp. 1906 - 1918
• Main Authors: Van der Mynsbrugge, Jeroen, Moors, Samuel L. C., De Wispelaere, Kristof, Van Speybroeck, Veronique
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.07.2014; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: kinetics; Methanol; methylation; molecular dynamics; molecular modeling; Protons; Zeolites
• ISSN: 1867-3880; 1867-3899
• DOI: 10.1002/cctc.201402146

Framework‐bound methoxides occur as intermediates in the stepwise mechanism for zeolite‐catalyzed methylation reactions. Herein, the formation of methoxides from methanol or dimethyl ether in H‐ZSM‐5 is investigated by a combination of static and dynamic simulations, with particular focus on the effect of additional water and methanol molecules on the mechanism and kinetics. Metadynamics simulations allow partitioning the reaction path into distinct phases. Proton transfer from the zeolite to the reactants is found to be the rate‐limiting phase in the methoxide formation. Additional methanol molecules only assist the proton transfer in the methoxide formation from methanol, whereas the reaction from dimethyl ether does not benefit from methanol assistance. Once formed, methoxides are found to be as reactive toward alkene methylation as methanol and dimethyl ether. How may I assist you? The formation of framework‐bound methoxides from methanol or dimethyl ether in zeolite H‐ZSM‐5 is investigated by a combination of static and dynamic simulations. Additional methanol molecules assist the proton transfer, which is the rate‐limiting phase, in the methoxide formation from methanol, but not from dimethyl ether.