Shaped Ceria Nanocrystals Catalyze Efficient and Selective Para‐Hydrogen‐Enhanced Polarization |
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Authors: | Evan W Zhao Haibin Zheng Dr Ronghui Zhou Prof Helena E Hagelin‐Weaver Prof Clifford R Bowers |
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Institution: | 1. Department of Chemistry, University of Florida, Gainesville, FL 32611 (USA);2. Department of Chemical Engineering, University of Florida, Gainesville, FL 32611 (USA) |
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Abstract: | 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. |
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Keywords: | catalysis ceria hydrogenation NMR spectroscopy nuclear spin hyperpolarization |
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