Probing the Different Life Stages of a Fluid Catalytic Cracking Particle with Integrated Laser and Electron Microscopy

• Published in: Chemistry : a European journal 2013-03, Vol.19 (12), p.3846-3859
• Main Authors: Karreman, Matthia A., Buurmans, Inge L. C., Agronskaia, Alexandra V., Geus, John W., Gerritsen, Hans C., Weckhuysen, Bert M.
• Format: Article
• Language: English
• Subjects: Catalysis; Catalysts; Chemistry; cracking; Crystal defects; Deactivation; Degradation; Electron microscopy; Fluid catalytic cracking; Fluorescence; fluorescence microscopy; heterogeneous catalysis; Microscopy, Confocal - methods; Microscopy, Electron - methods; Microscopy, Fluorescence; Zeolites; Zeolites - chemistry
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201203491

While cycling through a fluid catalytic cracking (FCC) unit, the structure and performance of FCC catalyst particles are severely affected. In this study, we set out to characterize the damage to commercial equilibrium catalyst particles, further denoted as ECat samples, and map the different pathways involved in their deactivation in a practical unit. The degradation was studied on a structural and a functional level. Transmission electron microscopy (TEM) of ECat samples revealed several structural features; including zeolite crystals that were partly or fully severed, mesoporous, macroporous, and/or amorphous. These defects were then correlated to structural features observed in FCC particles that were treated with different levels of hydrothermal deactivation. This allowed us not only to identify which features observed in ECat samples were a result of hydrothermal deactivation, but also to determine the severity of treatments resulting in these defects. For functional characterization of the ECat sample, the Brønsted acidity within individual FCC particles was studied by a selective fluorescent probe reaction with 4‐fluorostyrene. Integrated laser and electron microscopy (iLEM) allowed correlating this Brønsted acidity to structural features by combining a fluorescence and a transmission electron microscope in a single set‐up. Together, these analyses allowed us to postulate a plausible model for the degradation of zeolite crystals in FCC particles in the ECat sample. Furthermore, the distribution of the various deactivation processes within particles of different ages was studied. A rim of completely deactivated zeolites surrounding each particle in the ECat sample was identified by using iLEM. These zeolites, which were never observed in fresh or steam‐deactivated samples, contained clots of dense structures. The structures are proposed to be carbonaceous deposits formed during the cracking process, and seem resistant towards burning off during catalyst regeneration. Exposing the cracks: Several processes in an industrial fluid catalytic cracking (FCC) unit lead to deactivation of FCC particles. A structural and functional analysis of hydrothermally deactivated FCC particles and particles from a commercial equilibrium catalyst particle (ECat) sample was performed. A model is postulated for the degradation of the zeolite component. Inter‐ and intraparticle distributions of defects were mapped, resulting in the identification of a rim of fully deactiv