期刊
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
卷 137, 期 50, 页码 15781-15794出版社
AMER CHEMICAL SOC
DOI: 10.1021/jacs.5b09107
关键词
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资金
- U.S. Department of Energy (DOE), Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences Biosciences
- Office of Biological and Environmental Research
- NERSC (the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility by Office of Science of the U.S. Department of Energy) [DE-AC02-05CH11231]
- DOE [DE-AC05-76RL01830]
The Bronsted acid-catalyzed gas-phase dehydration of 1-propanol (0.075-4 kPa) was studied on zeolite H-MFI (Si/A1 = 26, containing minimal amounts of extra framework Al moieties) in the absence and presence of co-fed water (0-2.5 kPa) at 413-443 K. It is shown that propene can be formed from monomeric and dimeric adsorbed 1-propanol. The stronger adsorption of 1-propanol relative to water indicates that the reduced dehydration rates in the presence of water are not a consequence of the competitive adsorption between 1-propanol and water. Instead, the deleterious effect is related to the different extents of stabilization of adsorbed intermediates and the relevant elimination/substitution transition states by water. Water stabilizes the adsorbed 1-propanol monomer significantly more than the elimination transition state, leading to a higher activation barrier and a greater entropy gain for the rate-limiting step, which eventually leads to propene. In a similar manner, an excess of 1-propanol stabilizes the adsorbed state of 1-propanol more than the elimination transition state. In comparison with the monomer-mediated pathway, adsorbed dimer and the relevant transition states for propene and ether formation are similarly, while less effectively, stabilized by intrazeolite water molecules.
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