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

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• 作者：Evan W. Zhao ; Haibin Zheng ; Kaylee Ludden ; Yan Xin ; Helena E. Hagelin-Weaver ; Clifford R. Bowers
• 刊名：ACS Catalysis
• 出版年：2016
• 出版时间：February 5, 2016
• 年：2016
• 卷：6
• 期：2
• 页码：974-978
• 全文大小：345K
• ISSN：2155-5435

文摘

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.