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Resonant Ptychographic Tomography Facilitates Three-Dimensional Quantitative Colocalization of Catalyst Components and Chemical Elements

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posted on 17.09.2018, 00:00 by Johannes Ihli, Ana Diaz, Yuying Shu, Manuel Guizar-Sicairos, Mirko Holler, Klaus Wakonig, Michal Odstrcil, Teng Li, Frank Krumeich, Elisabeth Müller, Wu-Cheng Cheng, Jeroen Anton van Bokhoven, Andreas Menzel
The ability to localize selected chemical elements within individual components of functional matter is of great value to our understanding of material behavior. By means of resonant ptychographic X-ray computed tomography, we here provide such colocalization information with nanoscopic spatial resolution. Spatially correlated quantitative tomograms of electron density and iron concentration allowed the localization of native and feedstock-introduced iron impurities within the primary components of a prominent heterogeneous catalyst. Examinations found no direct evidence in favor of the currently suggested impurity-driven deactivation mechanisms of fluid catalytic cracking catalysts. The majority of iron impurities, present in the form of nanosized magnetite particulates, are found embedded in the outermost layer of an otherwise iron-poor, particle isolating amorphous silica–alumina envelope. Observations query both deactivation driven by impurity pore clogging and iron-impurity induced melting of catalyst components. The presented approach is general, extendable to secondary impurities or materials and spectroscopic ptychographic tomography. Future applications such as active-site localization and speciation in heterogeneous catalysis are envisioned.