Tomographic Energy Dispersive Diffraction Imaging To Study the Genesis of Ni Nanoparticles in 3D within γ-Al2O3 Catalyst Bodies

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• 作者：Leticia Espinosa-Alonso ; Matthew G. O’ ; Brien ; Simon D. M. Jacques ; Andrew M. Beale ; Krijn P. de Jong ; Paul Barnes ; Bert M. Weckhuysen
• 刊名：Journal of the American Chemical Society
• 出版年：2009
• 出版时间：November 25, 2009
• 年：2009
• 卷：131
• 期：46
• 页码：16932-16938
• 全文大小：367K
• 年卷期：v.131,no.46(November 25, 2009)
• ISSN：1520-5126

文摘

Tomographic energy dispersive diffraction imaging (TEDDI) is a recently developed synchrotron-based characterization technique used to obtain spatially resolved X-ray diffraction and fluorescence information in a noninvasive manner. With the use of a synchrotron beam, three-dimensional (3D) information can be conveniently obtained on the elemental composition and related crystalline phases of the interior of a material. In this work, we show for the first time its application to characterize the structure of a heterogeneous catalyst body in situ during thermal treatment. Ni/γ-Al₂O₃ hydrogenation catalyst bodies have been chosen as the system of study. As a first example, the heat treatment in N₂ of a [Ni(en)₃](NO₃)₂/γ-Al₂O₃ catalyst body has been studied. In this case, the crystalline [Ni(en)₃](NO₃)₂ precursor was detected in an egg-shell distribution, and its decomposition to form metallic Ni crystallites of around 5 nm was imaged. In the second example, the heat treatment in N₂ of a [Ni(en)(H₂O)₄]Cl₂/γ-Al₂O₃ catalyst body was followed. The initial [Ni(en)(H₂O)₄]Cl₂ precursor was uniformly distributed within the catalyst body as an amorphous material and was decomposed to form metallic Ni crystallites of around 30 nm with a uniform distribution. TEDDI also revealed that the decomposition of [Ni(en)(H₂O)₄]Cl₂ takes place via two intermediate crystalline structures. The first one, which appears at around 180 °C, is related to the restructuring of the Ni precursor on the alumina surface; the second one, assigned to the formation of a limited amount of Ni₃C, is observed at 290 °C.