Back Cover: Characterization of a Fluidized Catalytic Cracking Catalyst on Ensemble and Individual Particle Level by X‐ray Micro‐ and Nanotomography, Micro‐X‐ray Fluorescence, and Micro‐X‐ray Diffraction (ChemCatChem 5/2014)

Abstract

Many techniques, bigger pictureThe cover picture shows a combination of advanced characterization techniques: X-ray micro-and nanotomography and micro-X-ray fluorescence are used to characterize a commercial spent equilibrium fluid catalytic cracking catalyst at both the ensemble and individual particle level. In their Full Paper on p. 1427 ff., S. R. Bare et al. explain how the in-depth characterization study presents a robust methodology that provides an understanding of the equilibrium fluid catalytic cracking catalyst ECAT at both the micro-and nanometer scales.

3‐D X‐ray Nanotomography Reveals Different Carbon Deposition Mechanisms in a Single Catalyst Particle

“…The latter is a metric characterizing the particle's similarity to a perfect sphere (for which the roundness and sphericity parameters become one). The value before calcination confirms a smooth particle surface, which becomes rough after calcination – this again suggests that (patches of) coke deposits on the surface fill dips and dents in the catalyst's surface, which is in excellent agreement with earlier observations of a nodulated surface of aged (calcined) FCC catalyst particles [38,39,55–57,59] …”

“…The value before calcination confirms a smooth particle surface, which becomes rough after calcination -this again suggests that (patches of) coke deposits on the surface fill dips and dents in the catalyst's surface, which is in excellent agreement with earlier observations of a nodulated surface of aged (calcined) FCC catalyst particles. [38,39,[55][56][57]59] With respect to the observed porosity changes taking place due to calcination we observed a significant increase in macro-porosity and macro-pore surface area after the calcination step (Figure 3 and Supporting Table S4), which indicates that matter was removed also from the pores of the catalyst particle. Note that the measured porosity here inherently considered the previously reported metals contribution to pore space reduction [39,50,56,57] since the primary beam energy was above the metal's absorption edge.…”

“…The 3-D representation of the catalyst material obtained by Xray holotomography was used to characterize the studied FCC catalyst particle using single particle metrics established previously [38,55] (Figure 3, Experimental Section, Supporting Tables S4 and S5 in Section S14). The good agreement with earlier work [38,50,55] confirms that a typical, i. e., representative, aged FCC catalyst particle was investigated and, in agreement with bulk XRD data and SR-based in-situ SAXS/WAXS/DSC measurements, the comparison of values before and after calcination confirms that no morphological changes other than coke removal took place.…”

Structural Evolution of Highly Active Multicomponent Catalysts for Selective Propylene Oxidation

“…Furthermore, by applying computed tomography (CT) and three-dimensional (3D) image reconstruction, it is possible to retrieve chemical and structural data from the interior of catalyst bodies in a noninvasive manner [32][33][34]. Extending spatial resolution to 3D is a powerful advantage for the study of heterogeneous catalysts, which often contain delicate or fine structural features that are intimately linked to the catalyst function, as notably demonstrated for fluid catalytic cracking catalysts [35][36][37][38][39]. In principle, details such as sintering or growth of metal oxide phases, active metal distribution, and catalyst stability towards sintering and deactivation during short-and medium-term usage may all be feasibly studied using X-ray microscopy and were of interest in the current work.…”

Nickel Poisoning of a Cracking Catalyst Unravelled by Single‐Particle X‐ray Fluorescence‐Diffraction‐Absorption Tomography

“…[2] Poisoning metals, such as Fe, Ni and V, are normally contained in the vacuum gas oil (VGO) feedstock and are accumulated in a shell-like manner over time, while the catalyst runs through the reactor-regenerator cycles. [5][6][7][8][9][10][11][12][13][14] For this reason, their concentration is a direct indicator of the catalytic age of individual equilibrium catalyst (ECAT) particles. [6] While Fe contributes to surface vitrification of the catalyst, hindering catalyst accessibility, Ni and V promote hydrocarbons (de-) hydrogenation reactions speeding up coke deactivation.…”