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Insight into the Microstructure and Deactivation Effects on Commercial NiMo/γ-Al2O3 Catalyst through Aberration-Corrected Scanning Transmission Electron Microscopy

Research Institute of Petroleum Processing, SINOPEC, Beijing 100083, China
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Catalysts 2019, 9(10), 810; https://doi.org/10.3390/catal9100810
Received: 8 September 2019 / Revised: 19 September 2019 / Accepted: 22 September 2019 / Published: 27 September 2019
(This article belongs to the Section Catalytic Materials)
Atom-resolved microstructure variations and deactivation effects on the commercial NiMo/γ-Al2O3 catalysts were revealed by aberration-corrected scanning transmission electron microscope (Cs-STEM) equipped with enhanced energy dispersive X-ray spectroscopy (EDS). Structural information parallel to and vertical to the electron beam provides definitive insight toward an understanding of structure–activity relations. Under the mild to harsher reaction conditions, “fragment” structures (like metal single atoms, metal clusters, and nanoparticles) of commercial NiMo/γ-Al2O3 catalysts, gradually reduces, while MoS2 nanoslabs get longer and thinner. Such a result about active slabs leads to the reduction in the number of active sites, resulting in a significant decrease in activity. Likewise, the average atomic ratio of promoter Ni and Ni/(Mo + S) ratio of slabs decrease from 2.53% to 0.45% and from 0.0788 to 0.0326, respectively, by means of EDS under the same conditions stated above, reflecting the weakening of the promotional effect. XPS result confirms the existence of NixSy species in deactivated catalysts. This could be ascribed to the Ni segregation from active phase. Furthermore, statistical data give realistic coke behaviors associated with the active metals. With catalytic activity decreasing, the coke on the active metals regions tends to increase faster than that on the support regions. This highlights that the commercial NiMo/γ-Al2O3 catalyst during catalysis is prone to produce more coke on the active metal areas. View Full-Text
Keywords: NiMo/γ-Al2O3 catalyst; Cs-STEM; microstructure; deactivation effects NiMo/γ-Al2O3 catalyst; Cs-STEM; microstructure; deactivation effects
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MDPI and ACS Style

He, W.; Hu, A.; Qiu, L.; Wang, W.; Xiang, Y.; Han, W.; Xu, G.; Zhang, L.; Zheng, A. Insight into the Microstructure and Deactivation Effects on Commercial NiMo/γ-Al2O3 Catalyst through Aberration-Corrected Scanning Transmission Electron Microscopy. Catalysts 2019, 9, 810.

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    Description: Table S1: The average slabs length (¯L) and average stacking degree (¯N) of four NiMo/γ-Al2O3 catalysts. Figures S1-S3: District types on STEM-HAADF images of Cat B, Cat C and Cat D, and corresponding EDS spectra, respectively. Figure S4: Peak-fitting of Ni 2p XPS spectra of Cat A.
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