期刊
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
卷 53, 期 45, 页码 12177-12181出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/anie.201406823
关键词
density functional calculations; dimethyl ether; hydrogen bonding; methanol; IR spectroscopy
资金
- Chevron
- XSEDE Science Gateways program [CTS130011]
Mechanistic interpretations of rates and in situ IR spectra combined with density functionals that account for van der Waals interactions of intermediates and transition states within confining voids show that associative routes mediate the formation of dimethyl ether from methanol on zeolitic acids at the temperatures and pressures of practical dehydration catalysis. Methoxy-mediated dissociative routes become prevalent at higher temperatures and lower pressures, because they involve smaller transition states with higher enthalpy, but also higher entropy, than those in associative routes. These enthalpy-entropy trade-offs merely reflect the intervening role of temperature in activation free energies and the prevalence of more complex transition states at low temperatures and high pressures. This work provides a foundation for further inquiry into the contributions of H-bonded methanol and methoxy species in homologation and hydrocarbon synthesis reactions from methanol.
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