期刊
CHEMICAL SCIENCE
卷 9, 期 31, 页码 -出版社
ROYAL SOC CHEMISTRY
DOI: 10.1039/c8sc02302f
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资金
- National Natural Science Foundation of China [21403290, 21522310, 21473244, 91645112, 21773296]
- Natural Science Foundation of Hubei Province of China [2018CFA009]
- Key Research Program of Frontier Sciences, CAS [QYZDB-SSW-SLH026]
- Program for Applied Research on Super Computation of the NSFC-Guangdong Joint Fund (the second phase) [U1501501]
The methanol-to-olefin (MTO) reaction is an active field of research due to conflicting mechanistic proposals for the initial carbon-carbon (C-C) bond formation. Herein, a new methane-formaldehyde pathway, a Lewis acid site combined with a BrOnsted acid site in zeolite catalysts can readily activate dimethyl ether (DME) to form ethene, is identified theoretically. The mechanism involves a hydride transfer from Al-OCH3 on the Lewis acid site to the methyl group of the protonated methanol molecule on the adjacent BrOnsted acid site leading to synchronous formation of methane and Al-COH2+ (which can be considered as formaldehyde (HCHO) adsorbed on the Al3+ Lewis acid sites). The strong electrophilic character of the Al-COH2+ intermediate can strongly accelerate the C-C bond formation with CH4, as indicated by the significant decrease of activation barriers in the rate-determining-step of the catalytic processes. These results highlight a synergy of extra-framework aluminum (EFAl) Lewis and BrOnsted sites in zeolite catalysts that facilitates initial C-C bond formation in the initiation step of the MTO reaction via the Al-COH2+ intermediate.
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