title: Dehydration Pathways of 1-Propanol on HZSM-5 in the Presence and Absence of Water.
abstract: The Brønsted acid-catalyzed gas-phase dehydration of 1-propanol (0.075-4 kPa) was studied on zeolite H-MFI (Si/Al = 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.
authors.affiliation: Department of Chemistry and Catalysis Research Institute, Technische Universität München , Lichtenbergstrasse 4, 85748 Garching, Germany.
authors.forename: Yuchun
authors.initials: Y
authors.lastname: Zhi
authors.affiliation: Institute for Integrated Catalysis, Pacific Northwest National Laboratory , P.O. Box 999, Richland, Washington 99352, United States.
authors.forename: Hui
authors.initials: H
authors.lastname: Shi
authors.affiliation: Department of Chemistry and Catalysis Research Institute, Technische Universität München , Lichtenbergstrasse 4, 85748 Garching, Germany.
authors.forename: Linyu
authors.initials: L
authors.lastname: Mu
authors.affiliation: Department of Chemistry and Catalysis Research Institute, Technische Universität München , Lichtenbergstrasse 4, 85748 Garching, Germany.
authors.forename: Yue
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Institute for Integrated Catalysis, Pacific Northwest National Laboratory , P.O. Box 999, Richland, Washington 99352, United States.
authors.forename: Donghai
authors.initials: D
authors.lastname: Mei
authors.affiliation: Institute for Integrated Catalysis, Pacific Northwest National Laboratory , P.O. Box 999, Richland, Washington 99352, United States.
authors.forename: Donald M
authors.initials: DM
authors.lastname: Camaioni
authors.affiliation: Department of Chemistry and Catalysis Research Institute, Technische Universität München , Lichtenbergstrasse 4, 85748 Garching, Germany.|Institute for Integrated Catalysis, Pacific Northwest National Laboratory , P.O. Box 999, Richland, Washington 99352, United States.
authors.forename: Johannes A
authors.initials: JA
authors.lastname: Lercher