Strong Metal–Support Interactions Enhance the Pairwise Selectivity of Parahydrogen Addition over Ir/TiO2

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Department of Chemistry and Department of Chemical Engineering, University of Florida, Gainesville, Florida 32611, United States
# National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, United States
Cite this: ACS Catal. 2016, 6, 2, 974–978
Publication Date (Web):January 4, 2016
https://doi.org/10.1021/acscatal.5b02632
Copyright © 2016 American Chemical Society
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Abstract

The effects of strong metal–support interactions (SMSI) on the pairwise selectivity of propene hydrogenation over metal-oxide-supported Ir nanoparticles were investigated using parahydrogen-enhanced NMR spectroscopy. A ∼20-fold increase in the pairwise selectivity was observed following a reduction treatment of the Ir/TiO2 catalyst at 500 °C. Consistent with SMSI, the effects could be completely reversed by oxidation followed by rereduction at 200 °C. Noninteracting supports, such as Al2O3 and SiO2, did not show this behavior. X-ray photoelectron spectroscopy reveals partial reduction of the TiO2 support, and STEM data reveal flattening of Ir particles after high-temperature reduction. The presence of chloride ions during activation was found to further promote pairwise selectivity but only for the Ir/TiO2 catalyst. The results are interpreted in terms of the electronic and possible geometric blocking effects associated with SMSI.

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