Insights into protonation for cyclohexanol/water mixtures at the zeolitic Brønsted acid site

Proton transfer from Brønsted acid sites (BASs) to alcohol molecules ignites the acid-catalyzed alcohol dehydration reactions. For aqueous phase dehydration reactions in zeolites, the coexisting water molecules around BASs in the zeolite pores significantly affect the alcohol dehydration activity. I...

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Bibliographic Details
Published in:Physical chemistry chemical physics : PCCP 2021-05, Vol.23 (17), p.1395-141
Main Authors: Liu, Peng, Yan, Zhenxin, Mei, Donghai
Format: Article
Language:English
Subjects:
Alcohol
Algorithms
Chemical reactions
Clusters
Dehydration
Free energy
Molecular dynamics
Protonation
Protons
Trimers
Water chemistry
Zeolites
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Summary:Proton transfer from Brønsted acid sites (BASs) to alcohol molecules ignites the acid-catalyzed alcohol dehydration reactions. For aqueous phase dehydration reactions in zeolites, the coexisting water molecules around BASs in the zeolite pores significantly affect the alcohol dehydration activity. In the present work, proton transfer processes among the BASs of H-BEA zeolites, the adsorbed cyclohexanol and surrounding water clusters with different sizes up to 8 water molecules were investigated using ab initio molecular dynamics (AIMD) simulations combined with the multiple-walker well-tempered metadynamics algorithm. The plausible proton locations and proton transfer processes were characterized using two/three-dimensional free energy landscapes. The strong proton affinity makes the protonated cyclohexanol stable species until a water trimer is formed. The proton either is shared between protonated cyclohexanol and the water trimer or remains with the water trimer (H 7 O 3 + ). With a further increase in water concentrations, the proton prefers to remain with the water clusters. Free energy landscapes of protonation for cyclohexanol/water mixtures at the zeolitic Brønsted acid site.
ISSN:1463-9076
1463-9084
DOI:10.1039/d0cp06523d