1. Strong Metal–Support Interactions Enhance the Pairwise Selectivity of Parahydrogen Addition over Ir/TiO2
- Author
-
Yan Xin, Clifford R. Bowers, Evan Wenbo Zhao, Haibin Zheng, Kaylee Ludden, and Helena E. Hagelin-Weaver
- Subjects
010405 organic chemistry ,Chemistry ,General Chemistry ,Nuclear magnetic resonance spectroscopy ,010402 general chemistry ,Spin isomers of hydrogen ,Heterogeneous catalysis ,Photochemistry ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Metal ,Propene ,chemistry.chemical_compound ,X-ray photoelectron spectroscopy ,visual_art ,visual_art.visual_art_medium ,Selectivity - 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.
- Published
- 2016
- Full Text
- View/download PDF