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Single-Facet Dominant Anatase TiO2 (101) and (001) Model Catalysts to Elucidate the Active Sites for Alkanol Dehydration
journal contribution
posted on 2020-03-20, 13:04 authored by Fan Lin, Yuan Chen, Lu Zhang, Donghai Mei, Libor Kovarik, Berlin Sudduth, Huamin Wang, Feng Gao, Yong WangAlkanol dehydration
on Lewis acid–base pairs of transition
metal oxide catalysts is a reaction of importance in oxygen removal
from biomass-derived feedstocks and their conversion to chemicals
in general. However, catalysts with a high degree of structural heterogeneity,
such as commercial TiO2 powders, are not well-suited to
establish rigorous structure–function relationships at an atomic
level. Here, we provide compelling evidence for the effects of surface
orientation of TiO2 catalyst on elimination reactions of
alcohols. Two anatase titania model catalysts, with preferential exposure
of (101) and (001) facets, were synthesized and studied for 2-propanol
dehydration using kinetic, isotopic, microscopic, and spectroscopic
measurements, coupled with DFT calculations. Surface Lewis acid sites
were found to be active for 2-propanol dehydration, and (101) facets
are more reactive than (001) facets under the reaction conditions
studied. On both anatase surfaces, 2-propanol was found to dehydrate
via concerted E2 elimination pathways, but with different initial
states and thus also different intrinsic activation barriers. Molecular
2-propanol dehydration dominates on TiO2 (101) while on
TiO2 (001), 2-propanol simultaneously converts to more
stable 2-propoxide before dehydration, which then requires higher
activation energies for E2 elimination.
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oxygen removal2- propanolspectroscopic measurementsAlkanol Dehydration Alkanol dehydrationE 2 eliminationtransition metal oxide catalystsDFT calculationsanatase surfacesTiO 2 powdersbiomass-derived feedstocksSurface Lewis acid sitesfacetsurface orientationTiO 2 catalyst2- propanol dehydration2- propoxideMolecular 2- propanol dehydrationreaction conditionsactivation energiesanatase titania model catalystsactivation barriersActive Siteselimination reactionsE 2 elimination pathways
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