Shaped Ceria Nanocrystals Catalyze Efficient and Selective Para-Hydrogen-Enhanced Polarization.

Autor: Zhao EW; Department of Chemistry, University of Florida, Gainesville, FL 32611 (USA)., Zheng H; Department of Chemical Engineering, University of Florida, Gainesville, FL 32611 (USA)., Zhou R; Department of Chemistry, University of Florida, Gainesville, FL 32611 (USA)., Hagelin-Weaver HE; Department of Chemical Engineering, University of Florida, Gainesville, FL 32611 (USA). hweaver@che.ufl.edu., Bowers CR; Department of Chemistry, University of Florida, Gainesville, FL 32611 (USA). bowers@chem.ufl.edu.
Jazyk: angličtina
Zdroj: Angewandte Chemie (International ed. in English) [Angew Chem Int Ed Engl] 2015 Nov 23; Vol. 54 (48), pp. 14270-5. Date of Electronic Publication: 2015 Sep 01.
DOI: 10.1002/anie.201506045
Abstrakt: Intense para-hydrogen-enhanced NMR signals are observed in the hydrogenation of propene and propyne over ceria nanocubes, nano-octahedra, and nanorods. The well-defined ceria shapes, synthesized by a hydrothermal method, expose different crystalline facets with various oxygen vacancy densities, which are known to play a role in hydrogenation and oxidation catalysis. While the catalytic activity of the hydrogenation of propene over ceria is strongly facet-dependent, the pairwise selectivity is low (2.4% at 375 °C), which is consistent with stepwise H atom transfer, and it is the same for all three nanocrystal shapes. Selective semi-hydrogenation of propyne over ceria nanocubes yields hyperpolarized propene with a similar pairwise selectivity of (2.7% at 300 °C), indicating product formation predominantly by a non-pairwise addition. Ceria is also shown to be an efficient pairwise replacement catalyst for propene.
(© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)
Databáze: MEDLINE
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