Unraveling Spatially Dependent Hydrophilicity and Reactivity of Confined Carbocation Intermediates during Methanol Conversion over ZSM‑5 Zeolite

Carbocations play a pivotal role as reactive intermediates in zeolite-catalyzed methanol-to-hydrocarbon (MTH) transformations. However, the interaction between carbocations and water vapor and its subsequent effects on catalytic performance remain poorly understood. Using micro-magnetic resonance im...

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Published inJournal of the American Chemical Society Vol. 146; no. 12; pp. 8688 - 8696
Main Authors Wang, Chao, Zheng, Mingji, Hu, Min, Cai, Wenjin, Chu, Yueying, Wang, Qiang, Xu, Jun, Deng, Feng
Format Journal Article
LanguageEnglish
Published United States American Chemical Society 27.03.2024
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Abstract Carbocations play a pivotal role as reactive intermediates in zeolite-catalyzed methanol-to-hydrocarbon (MTH) transformations. However, the interaction between carbocations and water vapor and its subsequent effects on catalytic performance remain poorly understood. Using micro-magnetic resonance imaging (μMRI) and solid-state NMR techniques, this work investigates the hydrophilic behavior of cyclopentenyl cations within ZSM-5 pores under vapor conditions. We show that the polar cationic center of cyclopentenyl cations readily initiates water nucleus formation through water molecule capture. This leads to an inhomogeneous water adsorption gradient along the axial positions of zeolite, correlating with the spatial distribution of carbocation concentrations. The adsorbed water promotes deprotonation and aromatization of cyclopentenyl cations, significantly enhancing the aromatic product selectivity in MTH catalysis. These results reveal the important influence of adsorbed water in modulating the carbocation reactivity within confined zeolite pores.
AbstractList Carbocations play a pivotal role as reactive intermediates in zeolite-catalyzed methanol-to-hydrocarbon (MTH) transformations. However, the interaction between carbocations and water vapor and its subsequent effects on catalytic performance remain poorly understood. Using micro-magnetic resonance imaging (μMRI) and solid-state NMR techniques, this work investigates the hydrophilic behavior of cyclopentenyl cations within ZSM-5 pores under vapor conditions. We show that the polar cationic center of cyclopentenyl cations readily initiates water nucleus formation through water molecule capture. This leads to an inhomogeneous water adsorption gradient along the axial positions of zeolite, correlating with the spatial distribution of carbocation concentrations. The adsorbed water promotes deprotonation and aromatization of cyclopentenyl cations, significantly enhancing the aromatic product selectivity in MTH catalysis. These results reveal the important influence of adsorbed water in modulating the carbocation reactivity within confined zeolite pores.
Author Zheng, Mingji
Hu, Min
Wang, Chao
Xu, Jun
Chu, Yueying
Deng, Feng
Wang, Qiang
Cai, Wenjin
AuthorAffiliation National Center for Magnetic Resonance in Wuhan, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology
Chinese Academy of Sciences
University of Chinese Academy of Sciences
AuthorAffiliation_xml – name: University of Chinese Academy of Sciences
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– name: National Center for Magnetic Resonance in Wuhan, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology
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  organization: University of Chinese Academy of Sciences
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Snippet Carbocations play a pivotal role as reactive intermediates in zeolite-catalyzed methanol-to-hydrocarbon (MTH) transformations. However, the interaction between...
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Title Unraveling Spatially Dependent Hydrophilicity and Reactivity of Confined Carbocation Intermediates during Methanol Conversion over ZSM‑5 Zeolite
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